U.S. patent application number 14/054548 was filed with the patent office on 2014-10-16 for up-conversion based on gated information signal.
This patent application is currently assigned to ParkerVision, Inc.. The applicant listed for this patent is ParkerVision, Inc.. Invention is credited to Michael J. Bultman, Robert W. Cook, Robert C. Looke, Charley D. Moses, JR., David F. Sorrells.
Application Number | 20140308909 14/054548 |
Document ID | / |
Family ID | 34682075 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140308909 |
Kind Code |
A1 |
Sorrells; David F. ; et
al. |
October 16, 2014 |
Up-Conversion Based on Gated Information Signal
Abstract
A method and system is described wherein an information signal
is gated at a frequency that is a sub-harmonic of the frequency of
the desired output signal. In the modulation embodiments, the
information signal is modulated as part of the up-conversion
process. In a first modulation embodiment, one information signal
is phase modulated onto the carrier signal as part of the
up-conversion process. In a second modulation embodiment, two
information signals are multiplied, and, as part of the
up-conversion process, one signal is phase modulated onto the
carrier and the other signal is amplitude modulated onto the
carrier. In a third modulation embodiment, one information signal
is phase modulated onto the "I" phase of the carrier signal as part
of the up-conversion process and a second information signal is
phase modulated onto the "Q" phase of the carrier as part of the
up-conversion process.
Inventors: |
Sorrells; David F.;
(Middleburg, FL) ; Bultman; Michael J.;
(Jacksonville, FL) ; Cook; Robert W.;
(Switzerland, FL) ; Looke; Robert C.;
(Jacksonville, FL) ; Moses, JR.; Charley D.;
(Jacksonville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ParkerVision, Inc. |
Jacksonville |
FL |
US |
|
|
Assignee: |
ParkerVision, Inc.
Jacksonville
FL
|
Family ID: |
34682075 |
Appl. No.: |
14/054548 |
Filed: |
October 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13550492 |
Jul 16, 2012 |
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14054548 |
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|
12615326 |
Nov 10, 2009 |
8233855 |
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13550492 |
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11826416 |
Jul 16, 2007 |
7620378 |
|
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12615326 |
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11049057 |
Feb 3, 2005 |
7245886 |
|
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11826416 |
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09548923 |
Apr 13, 2000 |
7039372 |
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11049057 |
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09379497 |
Aug 23, 1999 |
6353735 |
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09548923 |
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09176154 |
Oct 21, 1998 |
6091940 |
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09379497 |
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Current U.S.
Class: |
455/118 |
Current CPC
Class: |
H04B 1/04 20130101; H03C
1/62 20130101; H03D 7/00 20130101; H04B 7/12 20130101; H04B
2001/0491 20130101 |
Class at
Publication: |
455/118 |
International
Class: |
H03D 7/00 20060101
H03D007/00; H04B 1/04 20060101 H04B001/04 |
Claims
1. A system for modulating and up-converting an information signal,
comprising: gating means for gating the information signal at a
rate that is substantially equal to a desired sub-harmonic of a
desired frequency of an output signal, thereby generating a gated
information signal, said gated information signal having an
amplitude that is a function of the information signal;
differentiating means for differentiating said gated information
signal to generate a harmonically rich signal having a plurality of
harmonics; and selecting means for selecting at least one of said
plurality of harmonics as a desired output signal, said desired
output signal being at said desired frequency.
Description
[0001] This is a continuation application of pending U.S. patent
application Ser. No. 13/550,492, titled "Up-Conversion Based on
Gated Information Signal" filed Jul. 16, 2012, which is a
continuation of U.S. patent application Ser. No. 12/615,326,
titled, "Up-Conversion Based On Gated Information Signal," filed on
Nov. 10, 2009, now U.S. Pat. No. 8,233,855, which is a continuation
of U.S. Pat. No. 7,620,378, titled, "Method And System for
Frequency Up-Conversion with Modulation Embodiments," filed on Jul.
16, 2007, which is a continuation of U.S. Pat. No. 7,245,886,
titled, "Method and System for Frequency Up-conversion With
Modulation Embodiments, filed Feb. 3, 2005, which is a continuation
of application of U.S. Pat. No. 7,039,372, titled, "Method and
System for Frequency Up-Conversion With Modulation Embodiments,"
filed Apr. 13, 2000, which is a continuation-in-part application of
U.S. Pat. No. 6,353,735, titled "Method for Output Signal
Generation," filed Aug. 23, 1999, which is a continuation of U.S.
Pat. No. 6,091,940, titled "Method and System for Frequency
Up-Conversion," filed Oct. 21, 1998, all of which are incorporated
herein by reference in their entireties.
CROSS-REFERENCE TO OTHER APPLICATIONS
[0002] The following applications of common assignee are related to
the present application, and are herein incorporated by reference
in their entireties:
[0003] "Method and System for Down-Converting Electromagnetic
Signals," Ser. No. 09/176,022, filed Oct. 21, 1998.
[0004] "Method and System for Ensuring Reception of a
Communications Signal," Ser. No. 09/176,415, filed Oct. 21,
1998.
[0005] "Integrated Frequency Translation and Selectivity," Ser. No.
09/175,966, filed Oct. 21, 1998, U.S. Pat. No. 6,049,706.
[0006] "Applications of Universal Frequency Translation," Ser. No.
09/261,129, filed Mar. 3, 1999.
[0007] "Method and System for Down-Converting Electromagnetic
Signals Having Optimized Switch Structures," Ser. No. 09/293,095,
filed Apr. 16, 1999.
[0008] "Method and System for Down-Converting Electromagnetic
Signals Including Resonant
[0009] Structures for Enhanced Energy Transfer," Ser. No.
09/293,342, filed Apr. 16, 1999.
[0010] "Method and System for Frequency Up-Conversion With a
Variety of Transmitter Configurations," Ser. No. 09/293,580, filed
Apr. 16, 1999.
[0011] "Integrated Frequency Translation And Selectivity With a
Variety of Filter Embodiments," Ser. No. 09/293,283, filed Apr. 16,
1999.
BACKGROUND OF THE INVENTION
[0012] 1. Field of the Invention
[0013] The present invention is generally directed to frequency
up-conversion of electromagnetic (EM) signals.
[0014] 2. Related Art
[0015] Modern day communication systems employ components such as
transmitters and receivers to transmit information from a source to
a destination. To accomplish this transmission, information is
imparted on a carrier signal and the carrier signal is then
transmitted. Typically, the carrier signal is at a frequency higher
than the baseband frequency of the information signal. Typical ways
that the information is imparted on the carrier signal are called
modulation.
[0016] Three widely used modulation schemes include: frequency
modulation (FM), where the frequency of the carrier wave changes to
reflect the information that has been modulated on the signal;
phase modulation (PM), where the phase of the carrier signal
changes to reflect the information imparted on it; and amplitude
modulation (AM), where the amplitude of the carrier signal changes
to reflect the information. Also, these modulation schemes are used
in combination with each other (e.g., AM combined with FM and AM
combined with PM).
SUMMARY OF THE INVENTION
[0017] The present invention is directed to methods and systems to
up-convert a signal from a lower frequency to a higher frequency,
and applications thereof.
[0018] In one embodiment, the invention uses a stable, low
frequency signal to generate a higher frequency signal with a
frequency and phase that can be used as stable references.
[0019] In another embodiment, the present invention is used as a
transmitter. In this embodiment, the invention accepts an
information signal at a baseband frequency and transmits a
modulated signal at a frequency higher than the baseband
frequency.
[0020] The methods and systems of transmitting vary slightly
depending on the modulation scheme being used. For some embodiments
using frequency modulation (FM) or phase modulation (PM), the
information signal is used to modulate an oscillating signal to
create a modulated intermediate signal. If needed, this modulated
intermediate signal is "shaped" to provide a substantially optimum
pulse-width-to-period ratio. This shaped signal is then used to
control a switch which opens and closes as a function of the
frequency and pulse width of the shaped signal. As a result of this
opening and closing, a signal that is harmonically rich is produced
with each harmonic of the harmonically rich signal being modulated
substantially the same as the modulated intermediate signal.
Through proper filtering, the desired harmonic (or harmonics) is
selected and transmitted.
[0021] For some embodiments using amplitude modulation (AM), the
switch is controlled by an unmodulated oscillating signal (which
may, if needed, be shaped). As the switch opens and closes, it
gates a reference signal which is the information signal. In an
alternate implementation, the information signal is combined with a
bias signal to create the reference signal, which is then gated.
The result of the gating is a harmonically rich signal having a
fundamental frequency substantially proportional to the oscillating
signal and an amplitude substantially proportional to the amplitude
of the reference signal. Each of the harmonics of the harmonically
rich signal also have amplitudes proportional to the reference
signal, and are thus considered to be amplitude modulated. Just as
with the FM/PM embodiments described above, through proper
filtering, the desired harmonic (or harmonics) is selected and
transmitted.
[0022] Further features and advantages of the invention, as well as
the structure and operation of various embodiments of the
invention, are described in detail below with reference to the
accompanying figures. The left-most digit(s) of a reference number
typically identifies the figure in which the reference number first
appears.
BRIEF DESCRIPTION OF THE FIGURES
[0023] FIG. 1 illustrates a circuit for a frequency modulation (FM)
transmitter;
[0024] FIGS. 2A, 2B, and 2C illustrate typical waveforms associated
with the FIG. 1 FM circuit for a digital information signal;
[0025] FIG. 3 illustrates a circuit for a phase modulation (PM)
transmitter;
[0026] FIGS. 4A, 4B, and 4C illustrate typical waveforms associated
with the FIG. 3 PM circuit for a digital information signal;
[0027] FIG. 5 illustrates a circuit for an amplitude modulation
(AM) transmitter;
[0028] FIGS. 6A, 6B, and 6C illustrate typical waveforms associated
with the FIG. 5 AM circuit for a digital information signal;
[0029] FIG. 7 illustrates a circuit for an
in-phase/quadrature-phase modulation ("I/Q") transmitter;
[0030] FIGS. 8A, 8B, 8C, 8D, and 8E illustrate typical waveforms
associated with the FIG. 7 "I/Q" circuit for digital information
signal;
[0031] FIG. 9 illustrates the high level operational flowchart of a
transmitter according to an embodiment of the present
invention;
[0032] FIG. 10 illustrates the high level structural block diagram
of the transmitter of an embodiment of the present invention;
[0033] FIG. 11 illustrates the operational flowchart of a first
embodiment (i.e., FM mode) of the present invention;
[0034] FIG. 12 illustrates an exemplary structural block diagram of
the first embodiment (i.e., FM mode) of the present invention;
[0035] FIG. 13 illustrates the operational flowchart of a second
embodiment (i.e., PM mode) of the present invention;
[0036] FIG. 14 illustrates an exemplary structural block diagram of
the second embodiment (i.e., PM mode) of the present invention;
[0037] FIG. 15 illustrates the operational flowchart of a third
embodiment (i.e., AM mode) of the present invention;
[0038] FIG. 16 illustrates an exemplary structural block diagram of
the third embodiment (i.e., AM mode) of the present invention;
[0039] FIG. 17 illustrates the operational flowchart of a fourth
embodiment (i.e., "I/Q" mode) of the present invention;
[0040] FIG. 18 illustrates an exemplary structural block diagram of
the fourth embodiment (i.e., "I/Q" mode) of the present
invention;
[0041] FIGS. 19A-19I illustrate exemplary waveforms (for a
frequency modulation mode operating in a frequency shift keying
embodiment) at a plurality of points in an exemplary high level
circuit diagram;
[0042] FIGS. 20A, 20B, 20C illustrate typical waveforms associated
with the FIG. 1 FM circuit for an analog information signal;
[0043] FIGS. 21A, 21B, 21C illustrate typical waveforms associated
with the FIG. 3 PM circuit for an analog information signal;
[0044] FIGS. 22A, 22B, 22C illustrate typical waveforms associated
with the FIG. 5 AM circuit for an analog information signal;
[0045] FIG. 23 illustrates an implementation example of a voltage
controlled oscillator (VCO);
[0046] FIG. 24 illustrates an implementation example of a local
oscillator (LO);
[0047] FIG. 25 illustrates an implementation example of a phase
shifter;
[0048] FIG. 26 illustrates an implementation example of a phase
modulator;
[0049] FIG. 27 illustrates an implementation example of a summing
amplifier;
[0050] FIGS. 28A-28C illustrate an implementation example of a
switch module for the FM and PM modes;
[0051] FIG. 29A-29C illustrate an example of the switch module of
FIGS. 28A-28C wherein the switch is a GaAsFET;
[0052] FIGS. 30A-30C illustrate an example of a design to ensure
symmetry for a GaAsFET implementation in the FM and PM modes;
[0053] FIGS. 31A-31C illustrate an implementation example of a
switch module for the AM mode;
[0054] FIGS. 32A-31C illustrate the switch module of FIGS. 31A-31C
wherein the switch is a GaAsFET;
[0055] FIGS. 33A-33C illustrates an example of a design to ensure
symmetry for a GaAsFET implementation in the AM mode;
[0056] FIG. 34 illustrates an implementation example of a
summer;
[0057] FIG. 35 illustrates an implementation example of a
filter;
[0058] FIG. 36 is a representative spectrum demonstrating the
calculation of "Q;"
[0059] FIGS. 37A and 37B are representative examples of filter
circuits;
[0060] FIG. 38 illustrates an implementation example of a
transmission module;
[0061] FIG. 39A shows a first exemplary pulse shaping circuit using
digital logic devices for a squarewave input from an
oscillator;
[0062] FIGS. 39B, 39C, and 39D illustrate waveforms associated with
the FIG. 39A circuit;
[0063] FIG. 40A shows a second exemplary pulse shaping circuit
using digital logic devices for a squarewave input from an
oscillator;
[0064] FIGS. 40B, 40C, and 40D illustrate waveforms associated with
the FIG. 40A circuit;
[0065] FIG. 41 shows a third exemplary pulse shaping circuit for
any input from an oscillator;
[0066] FIGS. 42A, 42B, 42C, 42D, and 42E illustrate representative
waveforms associated with the FIG. 41 circuit;
[0067] FIG. 43 shows the internal circuitry for elements of FIG. 41
according to an embodiment of the invention;
[0068] FIGS. 44A-44G illustrate exemplary waveforms (for a pulse
modulation mode operating in a pulse shift keying embodiment) at a
plurality of points in an exemplary high level circuit diagram,
highlighting the characteristics of the first three harmonics;
[0069] FIGS. 45A-45F illustrate exemplary waveforms (for an
amplitude modulation mode operating in an amplitude shift keying
embodiment) at a plurality of points in an exemplary high level
circuit diagram, highlighting the characteristics of the first
three harmonics;
[0070] FIG. 46 illustrates an implementation example of a harmonic
enhancement module;
[0071] FIG. 47 illustrates an implementation example of an
amplifier module;
[0072] FIGS. 48A and 48B illustrate exemplary circuits for a linear
amplifier;
[0073] FIG. 49 illustrates a typical superheterodyne receiver;
[0074] FIG. 50 illustrates a transmitter according to an embodiment
of the present invention in a transceiver circuit with a typical
superheterodyne receiver in a full-duplex mode;
[0075] FIGS. 51A, 51B, 51C, and 51D illustrate a transmitter
according to an embodiment of the present invention in a
transceiver circuit using a common oscillator with a typical
superheterodyne receiver in a half-duplex mode;
[0076] FIG. 52 illustrates an exemplary receiver using universal
frequency down conversion techniques according to an
embodiment;
[0077] FIG. 53 illustrates an exemplary transmitter of the present
invention;
[0078] FIGS. 54A, 54B, and 54C illustrate an exemplary transmitter
of the present invention in a transceiver circuit with a universal
frequency down conversion receiver operating in a half-duplex mode
for the FM and PM modulation embodiment;
[0079] FIG. 55 illustrates an exemplary transmitter of the present
invention in a transceiver circuit with a universal frequency down
conversion receiver operating in a half-duplex mode for the AM
modulation embodiment;
[0080] FIG. 56 illustrates an exemplary transmitter of the present
invention in a transceiver circuit with a universal frequency down
conversion receiver operating in a full-duplex mode;
[0081] FIGS. 57A-57C illustrate an exemplary transmitter of the
present invention being used in frequency modulation, phase
modulation, and amplitude modulation embodiments, including a pulse
shaping circuit and an amplifier module;
[0082] FIG. 58 illustrates harmonic amplitudes for a
pulse-width-to-period ratio of 0.01;
[0083] FIG. 59 illustrates harmonic amplitudes for a
pulse-width-to-period ratio of 0.0556;
[0084] FIG. 60 is a table that illustrates the relative amplitudes
of the first 50 harmonics for six exemplary pulse-width-to-period
ratios;
[0085] FIG. 61 is a table that illustrates the relative amplitudes
of the first 25 harmonics for six pulse-width-to-period ratios
optimized for the 1.sup.st through 10.sup.th subharmonics;
[0086] FIG. 62 illustrates an exemplary structural block diagram
for an alternative embodiment of the present invention (i.e., a
mode wherein AM is combined with PM);
[0087] FIGS. 63A-63H illustrate exemplary waveforms (for the
embodiment of FIG. 62) at a plurality of points in an exemplary
high level circuit diagram, highlighting the characteristics of the
first two harmonics;
[0088] FIGS. 64A and 64A1 illustrate exemplary implementations of
aliasing modules;
[0089] FIGS. 64B-64F illustrate exemplary waveforms at a plurality
of points in the FIGS. 64A and 64A1 circuits;
[0090] FIG. 65--illustrates an exemplary circuit for a first
implementation for phase modulating an information signal as part
of the up-conversion process;
[0091] FIG. 66--illustrates an exemplary circuit for a first
implementation for phase modulating one information signal and
amplitude modulating a second information signal as part of the
up-conversion process;
[0092] FIG. 67--illustrates an exemplary circuit for a second
implementation for phase modulating an information signal as part
of the up-conversion process;
[0093] FIG. 68--illustrates an exemplary circuit for a second
implementation for phase modulating one information signal and
amplitude modulating a second information signal as part of the
up-conversion process;
[0094] FIG. 69--illustrates an exemplary circuit for a first
implementation for phase modulating one information signal onto the
"I" phase of a carrier and for phase modulating a second
information signal onto the "Q" phase of a carrier as part of the
up-conversion process;
[0095] FIG. 70--illustrates an exemplary circuit for a second
implementation for phase modulating one information signal onto the
"I" phase of a carrier and for phase modulating a second
information signal onto the "Q" phase of a carrier as part of the
up-conversion process;
[0096] FIG. 71--illustrates an exemplary circuit for phase
modulating a first information signal and amplitude modulating a
second information signal onto the "I" phase of a carrier, and for
phase modulating a third information signal and amplitude
modulating a fourth information signal onto the "Q" phase of a
carrier as part of the up-conversion process;
[0097] FIG. 72A is a block diagram of a splitter according to an
embodiment of the invention;
[0098] FIG. 72B is a more detailed diagram of a splitter according
to an embodiment of the invention;
[0099] FIGS. 72C and 72D are exemplary waveforms related to the
splitter of FIGS. 72A and 72B;
[0100] FIG. 72E is a block diagram of an I/Q circuit with a
splitter according to an embodiment of the invention;
[0101] FIGS. 72F-72J are exemplary waveforms related to the diagram
of FIG. 72A;
[0102] FIG. 73 is a block diagram of a switch module according to
an embodiment of the invention;
[0103] FIG. 74A is an implementation example of the block diagram
of FIG. 73;
[0104] FIGS. 74B-74Q are exemplary waveforms related to FIG.
74A;
[0105] FIG. 75A is another implementation example of the block
diagram of FIG. 73;
[0106] FIGS. 75B-75Q are exemplary waveforms related to FIG.
75A;
[0107] FIG. 76A is an exemplary MOSFET embodiment of the
invention;
[0108] FIG. 76B is an exemplary MOSFET embodiment of the
invention;
[0109] FIG. 76C is an exemplary MOSFET embodiment of the
invention;
[0110] FIG. 77A is another implementation example of the block
diagram of FIG. 73; and
[0111] FIGS. 77B-77Q are exemplary waveforms related to FIG.
75A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Table of Contents
1. Terminology.
2. Overview of the Invention.
[0112] 2.1 Discussion of Modulation Techniques. [0113] 2.2
Explanation of Exemplary Circuits and Waveforms. [0114] 2.2.1
Frequency Modulation. [0115] 2.2.2 Phase Modulation. [0116] 2.2.3
Amplitude Modulation. [0117] 2.2.4 In-phase/Quadrature-phase
Modulation. [0118] 2.3 Features of the Invention.
3. Frequency Up-conversion.
[0118] [0119] 3.1 High Level Description. [0120] 3.1.1 Operational
Description. [0121] 3.1.2 Structural Description. [0122] 3.2
Exemplary Embodiments. [0123] 3.2.1 First Embodiment: Frequency
Modulation (FM) Mode. [0124] 3.2.1.1 Operational Description.
[0125] 3.2.1.2 Structural Description. [0126] 3.2.2 Second
Embodiment: Phase Modulation (PM) Mode. [0127] 3.2.2.1 Operational
Description. [0128] 3.2.2.2 Structural Description. [0129] 3.2.3
Third Embodiment Amplitude Modulation (AM) Mode. [0130] 3.2.3.1
Operational Description. [0131] 3.2.3.2 Structural Description.
[0132] 3.2.4 Fourth Embodiment: In-phase/Quadrature-phase ("1/Q")
Modulation Mode. [0133] 3.2.4.1 Operational Description. [0134]
3.2.4.2 Structural Description. [0135] 3.2.5 Other Embodiments.
[0136] 3.2.5.1 Combination of Modulation Techniques [0137] 3.2.5.2
Modulation as Part of the Up-Conversion Process. [0138] 3.3 Methods
and Systems for Implementing the Embodiments. [0139] 3.3.1 The
Voltage Controlled Oscillator (FM Mode). [0140] 3.3.1.1 Operational
Description. [0141] 3.3.1.2 Structural Description. [0142] 3.3.2
The Local Oscillator (PM, AM, and "I/Q" Modes). [0143] 3.3.2.1
Operational Description. [0144] 3.3.2.2 Structural Description.
[0145] 3.3.3 The Phase Shifter (PM Mode). [0146] 3.3.3.1
Operational Description. [0147] 3.3.3.2 Structural Description.
[0148] 3.3.4 The Phase Modulator (PM and "I/Q" Modes). [0149]
3.3.4.1 Operational Description. [0150] 3.3.4.2 Structural
Description. [0151] 3.3.5 The Summing Module (AM Mode). [0152]
3.3.5.1 Operational Description. [0153] 3.3.5.2 Structural
Description. [0154] 3.3.6 The Switch Module (FM, PM, and "I/Q"
Modes). [0155] 3.3.6.1 Operational Description. [0156] 3.3.6.2
Structural Description. [0157] 3.3.7 The Switch Module (AM Mode).
[0158] 3.3.7.1 Operational Description. [0159] 3.3.7.2 Structural
Description. [0160] 3.3.8 The Summer ("I/Q" Mode). [0161] 3.3.8.1
Operational Description. [0162] 3.3.8.2 Structural Description.
[0163] 3.3.9 The Filter (FM, PM, AM, and "I/Q" Modes). [0164]
3.3.9.1 Operational Description. [0165] 3.3.9.2 Structural
Description. [0166] 3.3.10 The Transmission Module (FM, PM, AM, and
"I/Q" Modes). [0167] 3.3.10.1 Operational Description. [0168]
3.3.10.2 Structural Description. [0169] 3.3.11 Other
Implementations.
4. Harmonic Enhancement.
[0169] [0170] 4.1 High Level Description. [0171] 4.1.1 Operational
Description. [0172] 4.1.2 Structural Description. [0173] 4.2
Exemplary Embodiments. [0174] 4.2.1 First Embodiment: When a Square
Wave Feeds the Harmonic Enhancement Module to Create One Pulse per
Cycle. [0175] 4.2.1.1 Operational Description. [0176] 4.2.1.2
Structural Description. [0177] 4.2.2 Second Embodiment: When a
Square Wave Feeds the Harmonic Enhancement Module to Create Two
Pulses per Cycle. [0178] 4.2.2.1 Operational Description. [0179]
4.2.2.2 Structural Description. [0180] 4.2.3 Third Embodiment: When
Any Waveform Feeds the Harmonic Enhancement Module. [0181] 4.2.3.1
Operational Description. [0182] 4.2.3.2 Structural Description.
[0183] 4.2.4 Other Embodiments. [0184] 4.3 Implementation Examples.
[0185] 4.3.1 First Digital Logic Circuit. [0186] 4.3.2 Second
Digital Logic Circuit. [0187] 4.3.3 Analog Circuit. [0188] 4.3.4
Other Implementations.
5. Amplifier Module.
[0188] [0189] 5.1 High Level Description. [0190] 5.1.1 Operational
Description. [0191] 5.1.2 Structural Description. [0192] 5.2
Exemplary Embodiment. [0193] 5.2.1 Linear Amplifier. [0194] 5.2.1.1
Operational Description. [0195] 5.2.1.2 Structural Description.
[0196] 5.2.2 Other Embodiments. [0197] 5.3 Implementation Examples.
[0198] 5.3.1 Linear Amplifier. [0199] 5.3.1.1 Operational
Description. [0200] 5.3.1.2 Structural Description. [0201] 5.3.2
Other Implementations.
6. Receiver/Transmitter System.
[0201] [0202] 6.1 High Level Description. [0203] 6.2 Exemplary
Embodiments and Implementation Examples. [0204] 6.2.1 First
Embodiment: The Transmitter of the Present Invention Being Used in
a Circuit with a Superheterodyne Receiver. [0205] 6.2.2 Second
Embodiment: The Transmitter of the Present Invention Being Used
with a Universal Frequency Down Converter in a Half-Duplex Mode.
[0206] 6.2.3 Third Embodiment: The Transmitter of the Present
Invention Being Used with a Universal Frequency Down Converter in a
Full-Duplex Mode. [0207] 6.2.4 Other Embodiments and
Implementations. [0208] 6.3 Summary Description of Down-conversion
Using a Universal Frequency Translation Module.
7. Designing a Transmitter According to an Embodiment of the
Present Invention.
[0208] [0209] 7.1 Frequency of the Transmission Signal. [0210] 7.2
Characteristics of the Transmission Signal. [0211] 7.3 Modulation
Scheme. [0212] 7.4 Characteristics of the Information Signal.
[0213] 7.5 Characteristic of the Oscillating Signal. [0214] 7.5.1
Frequency of the Oscillating Signal. [0215] 7.5.2 Pulse Width of
the String of Pulses. [0216] 7.6 Design of the Pulse Shaping
Circuit. [0217] 7.7 Selection of the Switch. [0218] 7.7.1 Optimized
Switch Structures. [0219] 7.7.2 Phased D2D--Splitter in CMOS [0220]
7.8 Design of the Filter. [0221] 7.9 Selection of an Amplifier.
[0222] 7.10 Design of the Transmission Module.
1. TERMINOLOGY
[0223] Various terms used in this application are generally
described in this section. Each description in this section is
provided for illustrative and convenience purposes only, and is not
limiting. The meaning of these terms will be apparent to persons
skilled in the relevant art(s) based on the entirety of the
teachings provided herein.
[0224] Amplitude Modulation (AM): A modulation technique wherein
the amplitude of the carrier signal is shifted (i.e., varied) as a
function of the information signal. The frequency of the carrier
signal typically remains constant. A subset of AM is referred to as
"amplitude shift keying" which is used primarily for digital
communications where the amplitude of the carrier signal shifts
between discrete states rather than varying continuously as it does
for analog information.
[0225] Analog signal: A signal in which the information contained
therein is continuous as contrasted to discrete, and represents a
time varying physical event or quantity. The information content is
conveyed by varying at least one characteristic of the signal, such
as but not limited to amplitude, frequency, or phase, or any
combinations thereof.
[0226] Baseband signal: Any generic information signal desired for
transmission and/or reception. As used herein, it refers to both
the information signal that is generated at a source prior to any
transmission (also referred to as the modulating baseband signal),
and to the signal that is to be used by the recipient after
transmission (also referred to as the demodulated baseband
signal).
[0227] Carrier signal: A signal capable of carrying information.
Typically, it is an electromagnetic signal that can be varied
through a process called modulation. The frequency of the carrier
signal is referred to as the carrier frequency. A communications
system may have multiple carrier signals at different carrier
frequencies.
[0228] Control a switch: Causing a switch to open and close. The
switch may be, without limitation, mechanical, electrical,
electronic, optical, etc., or any combination thereof. Typically,
it is controlled by an electrical or electronic input. If the
switch is controlled by an electronic signal, it is typically a
different signal than the signals connected to either terminal of
the switch.
[0229] Demodulated baseband signal: The baseband signal that is to
be used by the recipient after transmission. Typically it has been
down converted from a carrier signal and has been demodulated. The
demodulated baseband signal should closely approximate the
information signal (i.e., the modulating baseband signal) in
frequency, amplitude, and information.
[0230] Demodulation: The process of removing information from a
carrier or intermediate frequency signal.
[0231] Digital signal: A signal in which the information contained
therein has discrete states as contrasted to a signal that has a
property that may be continuously variable.
[0232] Direct down conversion: A down conversion technique wherein
a received signal is directly down converted and demodulated, if
applicable, from the original transmitted frequency (i.e., a
carrier frequency) to baseband without having an intermediate
frequency.
[0233] Down conversion: A process for performing frequency
translation in which the final frequency is lower than the initial
frequency.
[0234] Drive a switch: Same as control a switch.
[0235] Frequency Modulation (FM): A modulation technique wherein
the frequency of the carrier signal is shifted (i.e., varied) as a
function of the information signal. A subset of FM is referred to
as "frequency shift keying" which is used primarily for digital
communications where the frequency of the carrier signal shifts
between discrete states rather than varying continuously as it does
for analog information.
[0236] Harmonic: A harmonic is a frequency or tone that, when
compared to its fundamental or reference frequency or tone, is an
integer multiple of it. In other words, if a periodic waveform has
a fundamental frequency of "f" (also called the first harmonic),
then its harmonics may be located at frequencies of "nf," where "n"
is 2, 3, 4, etc. The harmonic corresponding to n=2 is referred to
as the second harmonic, the harmonic corresponding to n=3 is
referred to as the third harmonic, and so on.
[0237] In-phase ("I") signal: The signal typically generated by an
oscillator. It has not had its phase shifted and is often
represented as a sine wave to distinguish it from a "Q" signal. The
"I" signal can, itself, be modulated by any means. When the "I"
signal is combined with a "Q" signal, the resultant signal is
referred to as an "I/Q" signal.
[0238] In-phase/Quadrature-phase ("I/Q") signal: The signal that
results when an "I" signal is summed with a "Q" signal. Typically,
both the "I" and "Q" signals have been phase modulated, although
other modulation techniques may also be used, such as amplitude
modulation. An "I/Q" signal is used to transmit separate streams of
information simultaneously on a single transmitted carrier. Note
that the modulated "I" signal and the modulated "Q" signal are both
carrier signals having the same frequency. When combined, the
resultant "I/Q" signal is also a carrier signal at the same
frequency.
[0239] Information signal: The signal that contains the information
that is to be transmitted. As used herein, it refers to the
original baseband signal at the source. When it is intended that
the information signal modulate a carrier signal, it is also
referred to as the "modulating baseband signal." It may be voice or
data, analog or digital, or any other signal or combination
thereof.
[0240] Intermediate frequency (IF) signal: A signal that is at a
frequency between the frequency of the baseband signal and the
frequency of the transmitted signal.
[0241] Modulation: The process of varying one or more physical
characteristics of a signal to represent the information to be
transmitted. Three commonly used modulation techniques are
frequency modulation, phase modulation, and amplitude modulation.
There are also variations, subsets, and combinations of these three
techniques.
[0242] Operate a switch: Same as control a switch.
[0243] Phase Modulation (PM): A modulation technique wherein the
phase of the carrier signal is shifted (i.e., varied) as a function
of the information signal. A subset of PM is referred to as "phase
shift keying" which is used primarily for digital communications
where the phase of the carrier signal shifts between discrete
states rather than varying continuously as it does for analog
information.
[0244] Quadrature-phase ("Q") signal: A signal that is out of phase
with an in-phase ("I") signal. The amount of phase shift is
predetermined for a particular application, but in a typical
implementation, the "Q" signal is 90.degree. out of phase with the
"I" signal. Thus, if the "I" signal were a sine wave, the "Q"
signal would be a cosine wave. When discussed together, the "I"
signal and the "Q" signal have the same frequencies.
[0245] Spectrum: Spectrum is used to signify a continuous range of
frequencies, usually wide, within which electromagnetic (EM) waves
have some specific common characteristic. Such waves may be
propagated in any communication medium, both natural and manmade,
including but not limited to air, space, wire, cable, liquid,
waveguide, microstrip, stripline, optical fiber, etc. The EM
spectrum includes all frequencies greater than zero hertz.
[0246] Subharmonic: A subharmonic is a frequency or tone that is an
integer submultiple of a referenced fundamental frequency or tone.
That is, a subharmonic frequency is the quotient obtained by
dividing the fundamental frequency by an integer. For example, if a
periodic waveform has a frequency of "f" (also called the
"fundamental frequency" or first subharmonic), then its
subharmonics have frequencies of "f/n," where n is 2, 3, 4, etc.
The subharmonic corresponding to n=2 is referred to as the second
subharmonic, the subharmonic corresponding to n=3 is referred to as
the third subharmonic, and so on. A subharmonic itself has possible
harmonics, and the it.sup.h harmonic of the i.sup.th subharmonic
will be at the fundamental frequency of the original periodic
waveform. For example, the third subharmonic (which has a frequency
of "f/3") may have harmonics at integer multiples of itself (i.e.,
a second harmonic at "2f/3," a third harmonic at "3f/3," and so
on). The third harmonic of the third subharmonic of the original
signal (i.e., "3f/3") is at the frequency of the original
signal.
[0247] Trigger a switch: Same as control a switch.
[0248] Up conversion: A process for performing frequency
translation in which the final frequency is higher than the initial
frequency.
2. OVERVIEW OF THE INVENTION
[0249] The present invention is directed to systems and methods for
frequency up-conversion, and applications thereof.
[0250] In one embodiment, the frequency up-converter of the present
invention is used as a stable reference frequency source in a phase
comparator or in a frequency comparator. This embodiment of the
present invention achieves this through the use of a stable, low
frequency local oscillator, a switch, and a filter. Because it
up-converts frequency, the present invention can take advantage of
the relatively low cost of low frequency oscillators to generate
stable, high frequency signals.
[0251] In a second embodiment, the frequency up-converter is used
as a system and method for transmitting an electromagnetic (EM)
signal.
[0252] Based on the discussion contained herein, one skilled in the
relevant art(s) will recognize that there are other, alternative
embodiments in which the frequency up-converter of the present
invention could be used in other applications, and that these
alternative embodiments fall within the scope of the present
invention.
[0253] For illustrative purposes, various modulation examples are
discussed below. However, it should be understood that the
invention is not limited by these examples. Other modulation
techniques that might be used with the present invention will be
apparent to persons skilled in the relevant art(s) based on the
teaching contained herein.
[0254] Also for illustrative purposes, frequency up-conversion
according to the present invention is described below in the
context of a transmitter. However, the invention is not limited to
this embodiment. Equivalents, extensions, variations, deviations,
etc., of the following will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. Such
equivalents, extensions, variations, deviations, etc., are within
the scope and spirit of the present invention.
2.1 Discussion of Modulation Techniques
[0255] Techniques by which information can be imparted onto EM
signals to be transmitted are called modulation. These techniques
are generally well known to one skilled in the relevant art(s), and
include, but are not limited to, frequency modulation (FM), phase
modulation (PM), amplitude modulation (AM), quadrature-phase shift
keying (QPSK), frequency shift keying (FSK), phase shift keying
(PSK), amplitude shift keying (ASK), etc., and combinations
thereof. These last three modulation techniques, FSK, PSK, and ASK,
are subsets of FM, PM, and AM, respectively, and refer to circuits
having discrete input signals (e.g., digital input signals).
[0256] For illustrative purposes only, the circuits and techniques
described below all refer to the EM broadcast medium. However, the
invention is not limited by this embodiment. Persons skilled in the
relevant art(s) will recognize that these same circuits and
techniques can be used in all transmission media (e.g.,
over-the-air broadcast, point-to-point cable, etc.).
2.2 Explanation of Exemplary Circuits and Waveforms
2.2.1 Frequency Modulation
[0257] FIG. 1 illustrates an example of a frequency modulation (FM)
circuit 100 and FIGS. 2A, 2B, and 2C, and FIGS. 20A, 20B, and 20C
illustrate examples of waveforms at several points in FM circuit
100. In an FM system, the frequency of a carrier signal, such as an
oscillating signal 202 (FIG. 2B and FIG. 20B), is varied to
represent the data to be communicated, such as information signals
102 of FIG. 2A and 2002 of FIG. 20A. In FIG. 20A, information
signal 2002 is a continuous signal (i.e., an analog signal), and in
FIG. 2A, information signal 102 is a discrete signal (i.e., a
digital signal). In the case of the discrete information signal
102, the FM circuit 100 is referred to as a frequency shift keying
(FSK) system, which is a subset of an FM system.
[0258] Frequency modulation circuit 100 receives an information
signal 102, 2002 from a source (not shown). Information signal 102,
2002 can be amplified by an optional amplifier 104 and filtered by
an optional filter 114 and is the voltage input that drives a
voltage controlled oscillator (VCO) 106. Within VCO 106, an
oscillating signal 202 (seen on FIG. 2B and FIG. 20B) is generated.
The purpose of VCO 106 is to vary the frequency of oscillating
signal 202 as a function of the input voltage, i.e., information
signal 102, 2002. The output of VCO 106 is a modulated signal shown
as modulated signal 108 (FIG. 2C) when the information signal is
the digital information signal 102 and shown as modulated signal
2004 (FIG. 20C) when the information signal is the analog signal
2002. Modulated signal 108, 2004 is at a relatively low frequency
(e.g., generally between 50 MHz and 100 MHz) and can have its
frequency increased by an optional frequency multiplier 110 (e.g.,
to 900 MHz, 1.8 GHz) and have its amplitude increased by an
optional amplifier 116. The output of optional frequency multiplier
110 and/or optional amplifier 116 is then transmitted by an
exemplary antenna 112.
2.2.2 Phase Modulation
[0259] FIG. 3 illustrates an example of a phase modulation (PM)
circuit 300 and FIGS. 4A, 4B, and 4C, and FIGS. 21A, 21B, and 21C
illustrate examples of waveforms at several points in PM circuit
300. In a PM system, the phase of a carrier signal, such as a local
oscillator (LO) output 308 (FIG. 4B and FIG. 21B), is varied to
represent the data to be communicated, such as an information
signals 302 of FIG. 4A and 2102 of FIG. 21A. In FIG. 21A,
information signal 2102 is a continuous signal (i.e., an analog
signal), and in FIG. 4A, information signal 302 is a discrete
signal (i.e., a digital signal). In the case of the discrete
information signal 302, the PM circuit is referred to as a phase
shift keying (PSK) system. This is the typical implementation, and
is a subset of a PM system.
[0260] Phase modulation circuit 300 receives information signal
302, 2102 from a source (not shown). Information signal 302, 2102
can be amplified by an optional amplifier 304 and filtered by an
optional filter 318 and is routed to a phase modulator 306. Also
feeding phase modulator 306 is LO output 308 of a local oscillator
310. LO output 308 is shown on FIG. 4B and FIG. 21B. Local
oscillators, such as local oscillator 310, output an
electromagnetic wave at a predetermined frequency and
amplitude.
[0261] The output of phase modulator 306 is a modulated signal
shown as a phase modulated signal 312 (FIG. 4C) when the
information signal is the discrete information signal 302 and shown
as a phase modulated signal 2104 (FIG. 21C) when the information
signal is the analog information signal 2102. The purpose of phase
modulator 306 is to change the phase of LO output 308 as a function
of the value of information signal 302, 2102. That is, for example
in a PSK mode, if LO output 308 were a sine wave, and the value of
information signal 302 changed from a binary high to a binary low,
the phase of LO output 308 would change from a sine wave with a
zero phase to a sine wave with, for example, a phase of
180.degree.. The result of this phase change would be phase
modulated signal 312 of FIG. 4C which would have the same frequency
as LO output 308, but would be out of phase by 180.degree. in this
example. For a PSK system, the phase changes in phase modulated
signal 312 that are representative of the information in
information signal 302 can be seen by comparing waveforms 302, 308,
and 312 on FIGS. 4A, 4B, and 4C. For the case of an analog
information signal 2102 of FIG. 21A, the phase of LO output 308 of
FIG. 21B changes continuously as a function of the amplitude of the
information signal 2102. That is, for example, as information
signal 2102 increases from a value of "X" to "X+ox", the PM signal
2104 of FIG. 21C changes from a signal which may be represented by
the equation sin(.omega.t) to a signal which can be represented by
the equation sin(.omega.t+.phi.), where .phi. is the phase change
associated with a change of Ox in information signal 2102. For an
analog PM system, the phase changes in phase modulated signal 2104
that are representative of the information in information signal
2102 can be seen by comparing waveforms 2102, 308, and 2104 on
FIGS. 21A, 21B, and 21C.
[0262] After information signal 302, 2102 and LO output 308 have
been modulated by phase modulator 306, phase modulated signal 312,
2104 can be routed to an optional frequency multiplier 314 and
optional amplifier 320. The purpose of optional frequency
multiplier 314 is to increase the frequency of phase modulated
signal 312 from a relatively low frequency (e.g., 50 MHz to 100
MHz) to a desired broadcast frequency (e.g., 900 MHz, 1.8 GHz).
Optional amplifier 320 raises the signal strength of phase
modulated signal 312, 2104 to a desired level to be transmitted by
an exemplary antenna 316.
2.2.3 Amplitude Modulation
[0263] FIG. 5 illustrates an example of an amplitude modulation
(AM) circuit 500 and FIGS. 6A, 6B, and 6C, and FIGS. 22A, 22B, and
22C illustrate examples of waveforms at several points in AM
circuit 500. In an AM system, the amplitude of a carrier signal,
such as a local oscillator (LO) signal 508 (FIG. 6B and FIG. 22B),
is varied to represent the data to be communicated, such as
information signals 502 of FIG. 6A and 2202 of FIG. 22A. In FIG.
22A, information signal 2202 is a continuous signal (i.e., an
analog signal), and in FIG. 6A, information signal 502 is a
discrete signal (i.e., a digital signal). In the case of the
discrete information signal 502, the AM circuit is referred to as
an amplitude shift keying (ASK) system, which is a subset of an AM
system.
[0264] Amplitude modulation circuit 500 receives information signal
502 from a source (not shown). Information signal 502, 2202 can be
amplified by an optional amplifier 504 and filtered by an optional
filter 518. Amplitude modulation circuit 500 also includes a local
oscillator (LO) 506 which has an LO output 508. Information signal
502, 2202 and LO output 508 are then multiplied by a multiplier
510. The purpose of multiplier 510 is to cause the amplitude of LO
output 508 to vary as a function of the amplitude of information
signal 502, 2202. The output of multiplier 510 is a modulated
signal shown as amplitude modulated signal 512 (FIG. 6C) when the
information signal is the digital information signal 502 and shown
as modulated signal 2204 (FIG. 22C) when the information signal is
the analog information signal 2202. AM signal 512, 2204 can then be
routed to an optional frequency multiplier 514 where the frequency
of AM signal 512, 2204 is increased from a relatively low level
(e.g., 50 MHz to 100 MHz) to a higher level desired for broadcast
(e.g., 900 MHz, 1.8 GHz) and an optional amplifier 520, which
increases the signal strength of AM signal 512, 2204 to a desired
level for broadcast by an exemplary antenna 516.
2.2.4 in-Phase/Quadrature-Phase Modulation
[0265] FIG. 7 illustrates an example of an
in-phase/quadrature-phase ("I/Q") modulation circuit 700 and FIGS.
8A, 8B, 8C, 8D, and 8E illustrate examples of waveforms at several
points in "I/Q" modulation circuit 700. In this technique, which
increases bandwidth efficiency, separate information signals can be
simultaneously transmitted on carrier signals that are out of phase
with each other. That is, a first information signal 702 of FIG. 8A
can be modulated onto the in-phase ("I") oscillator signal 710 of
FIG. 8B and a second information signal 704 of FIG. 8C can be
modulated onto the quadrature-phase ("Q") oscillator signal 712 of
FIG. 8D. The "I" modulated signal is combined with the "Q"
modulated signal and the resulting "I/Q" modulated signal is then
transmitted. In a typical usage, both information signals are
digital, and both are phase modulated onto the "I" and "Q"
oscillating signals. One skilled in the relevant art(s) will
recognize that the "I/Q" mode can also work with analog information
signals, with combinations of analog and digital signals, with
other modulation techniques, or any combinations thereof.
[0266] This "I/Q" modulation system uses two PM circuits together
in order to increase the bandwidth efficiency. As stated above, in
a PM circuit, the phase of an oscillating signal, such as 710 (or
712) (FIG. 8B or 8D), is varied to represent the data to be
communicated, such as an information signal such as 702 (or 704).
For ease of understanding and display, the discussion herein will
describe the more typical use of the "I/Q" mode, that is, with
digital information signals and phase modulation on both
oscillating signals. Thus, both signal streams are phase shift
keying (PSK), which is a subset of PM.
[0267] "I/Q" modulation circuit 700 receives an information signal
702 from a first source (not shown) and an information signal 704
from a second source (not shown). Examples of information signals
702 and 704 are shown in FIGS. 8A and 8C. Information signals 702
and 704 can be amplified by optional amplifiers 714 and 716 and
filtered by optional filters 734 and 736. It is then routed to
phase modulators 718 and 720. Also feeding phase modulators 718 and
720 are oscillating signals 710 and 712. Oscillating signal 710 was
generated by a local oscillator 706, and is shown in FIG. 8B, and
oscillating signal 712 is the phase shifted output of local
oscillator 706. Local oscillators, such as local oscillator 706,
output an electromagnetic wave at a predetermined frequency and
amplitude.
[0268] The output of phase modulator 718 is a phase modulated
signal 722 which is shown using a dotted line as one of the
waveforms in FIG. 8E. Similarly, the output of phase modulator 720,
which operates in a manner similar to phase modulator 718, is a
phase modulated signal 724 which is shown using a solid line as the
other waveform in FIG. 8E. The effect of phase modulators 718 and
720 on oscillating signals 710 and 712 is to cause them to change
phase. As stated above, the system shown here is a PSK system, and
as such, the phase of oscillating signals 710 and 712 is shifted by
phase modulators 718 and 720 by a discrete amount as a function of
information signals 702 and 704.
[0269] For simplicity of discussion and ease of display,
oscillating signal 710 is shown on FIG. 8B as a sine wave and is
referred to as the "I" signal in the "I/Q" circuit 700. After the
output of oscillator 706 has gone through a phase shifter 708,
shown here as shifting the phase by .pi./2, oscillating signal 712
is a cosine wave, shown on FIG. 8D, and is referred to as the "Q"
signal in the "I/Q" circuit. Again, for ease of display, phase
modulators 718 and 720 are shown as shifting the phase of the
respective oscillating signals 710 and 712 by 180.degree.. This is
seen on FIG. 8E. Modulated signal 722 is summed with modulated
signal 724 by a summer 726. The output of summer 726 is the
arithmetic sum of modulated signal 722 and 724 and is an "I/Q"
signal 728. (For clarity of the display on FIG. 8E, the combined
signal 728 is not shown. However, one skilled in the relevant
art(s) will recognize that the arithmetic sum of 2 sinusoidal waves
having the same frequency is also a sinusoidal wave at that
frequency.)
[0270] "I/Q" signal 728 can then be routed to an optional frequency
multiplier 730, where the frequency of "I/Q" signal 718 is
increased from a relatively low level (e.g., 50 MHz to 100 MHz) to
a higher level desired for broadcast (e.g., 900 MHz, 1.8 GHz), and
to an optional amplifier 738 which increases the signal strength of
"I/Q" signal 728 to a desired level for broadcast by an exemplary
antenna 732.
2.3 Features of the Invention
[0271] As apparent from the above, several frequencies are involved
in a communications system. The frequency of the information signal
is relatively low. The frequency of the local oscillator (both the
voltage controlled oscillator as well as the other oscillators) is
higher than that of the information signal, but typically not high
enough for efficient transmission. A third frequency, not
specifically mentioned above, is the frequency of the transmitted
signal which is greater than or equal to the frequency of the
oscillating signal. This is the frequency that is routed from the
optional frequency multipliers and optional amplifiers to the
antennas in the previously described circuits.
[0272] Typically, in the transmitter subsystem of a communications
system, upconverting the information signal to broadcast frequency
requires, at least, filters, amplifiers, and frequency multipliers.
Each of these components is costly, not only in terms of the
purchase price of the component, but also because of the power
required to operate them.
[0273] The present invention provides a more efficient means for
producing a modulated carrier for transmission, uses less power,
and requires fewer components. These and additional advantages of
the present invention will be apparent from the following
description.
3. FREQUENCY UP-CONVERSION
[0274] The present invention is directed to systems and methods for
frequency up-conversion and applications of the same. In one
embodiment, the frequency up-converter of the present invention
allows the use of a stable, low frequency oscillator to generate a
stable high frequency signal that, for example and without
limitation, can be used as a reference signal in a phase comparator
or a frequency comparator. In another embodiment, the up-converter
of the present invention is used in a transmitter. The invention is
also directed to a transmitter. Based on the discussion contained
herein, one skilled in the relevant art(s) will recognize that
there are other, alternative embodiments and applications in which
the frequency up-converter of the present invention could be used,
and that these alternative embodiments and applications fall within
the scope of the present invention.
[0275] For illustrative purposes, frequency up-conversion according
to the present invention is described below in the context of a
transmitter. However, as apparent from the preceding paragraph, the
invention is not limited to this embodiment.
[0276] The following sections describe methods related to a
transmitter and frequency up-converter. Structural exemplary
embodiments for achieving these methods are also described. It
should be understood that the invention is not limited to the
particular embodiments described below. Equivalents, extensions,
variations, deviations, etc., of the following will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such equivalents, extensions, variations,
deviations, etc., are within the scope and spirit of the present
invention.
3.1. High Level Description
[0277] This section (including its subsections) provides a
high-level description of up-converting and transmitting signals
according to the present invention. In particular, an operational
process of frequency up-conversion in the context of transmitting
signals is described at a high-level. The operational process is
often represented by flowcharts. The flowcharts are presented
herein for illustrative purposes only, and are not limiting. In
particular, the use of flowcharts should not be interpreted as
limiting the invention to discrete or digital operation. In
practice, those skilled in the relevant art(s) will appreciate,
based on the teachings contained herein, that the invention can be
achieved via discrete operation, continuous operation, or any
combination thereof. Furthermore, the flow of control represented
by the flowcharts is also provided for illustrative purposes only,
and it will be appreciated by persons skilled in the relevant
art(s) that other operational control flows are within the scope
and spirit of the invention.
[0278] Also, a structural implementation for achieving this process
is described at a high-level. This structural implementation is
described herein for illustrative purposes, and is not limiting. In
particular, the process described in this section can be achieved
using any number of structural implementations, one of which is
described in this section. The details of such structural
implementations will be apparent to persons skilled in the relevant
art(s) based on the teachings contained herein.
3.1.1 Operational Description
[0279] The flow chart 900 of FIG. 9 demonstrates the operational
method of frequency up-conversion in the context of transmitting a
signal according to an embodiment of the present invention. The
invention is directed to both frequency up-conversion and
transmitting signals as represented in FIG. 9. Representative
waveforms for signals generated in flow chart 900 are depicted in
FIG. 19. For purposes of illustrating the high level operation of
the invention, frequency modulation of a digital information signal
is depicted. The invention is not limited to this exemplary
embodiment. One skilled in the relevant art(s) will appreciate that
other modulation modes could alternatively be used (as described in
later sections).
[0280] In step 902, an information signal 1902 (FIG. 19A) is
generated by a source. This information signal may be analog,
digital, and any combination thereof, or anything else that is
desired to be transmitted, and is at the baseband frequency. As
described below, the information signal 1902 is used to modulate an
intermediate signal 1904. Accordingly, the information signal 1902
is also herein called a modulating baseband information signal. In
the example of FIG. 19A, the information signal 1902 is illustrated
as a digital signal. However, the invention is not limited to this
embodiment. As noted above, the information signal 1902 can be
analog, digital, and/or any combination thereof.
[0281] An oscillating signal 1904 (FIG. 19B) is generated in step
904. In step 906, the oscillating signal 1904 is modulated, where
the modulation is a result of, and a function of, the information
signal 1902. Step 906 produces a modulated oscillating signal 1906
(FIG. 19C), also called a modulated intermediate signal. As noted
above, the flowchart of FIG. 9 is being described in the context of
an example where the information signal 1902 is a digital signal.
However, alternatively, the information signal 1902 can be analog
or any combination of analog and digital. Also, the example shown
in FIG. 19 uses frequency shift keying (FSK) as the modulation
technique. Alternatively, any modulation technique (e.g., FM, AM,
PM, ASK, PSK, etc., or any combination thereof) can be used. The
remaining steps 908-912 of the flowchart of FIG. 9 operate in the
same way, whether the information signal 1902 is digital, analog,
etc., or any combination thereof, and regardless of what modulation
technique is used.
[0282] A harmonically rich signal 1908 (FIG. 19D) is generated from
the modulated signal 1906 in step 908. Signal 1908 has a
substantially continuous and periodically repeated waveform. In an
embodiment, the waveform of signal 1908 is substantially
rectangular, as is seen in the expanded waveform 1910 of FIG. 19E.
One skilled in the relevant art(s) will recognize the physical
limitations to and mathematical obstacles against achieving an
exact or perfect rectangular waveform and it is not the intent or
requirement of the present invention that a perfect rectangular
waveform be generated or needed. However, for ease of discussion,
the term "rectangular waveform" will be used herein and will refer
to waveforms that are substantially rectangular, and will include
but will not be limited to those waveforms that are generally
referred to as square waves or pulses. It should be noted that if
the situation arises wherein a perfect rectangular waveform is
proven to be both technically and mathematically feasible, that
situation will also fall within the scope and intent of this
invention
[0283] A continuous periodic waveform (such as waveform 1908) is
composed of a series of sinusoidal waves of specific amplitudes and
phases, the frequencies of which are integer multiples of the
repetition frequency of the waveform. (A waveform's repetition
frequency is the number of times per second the periodic waveform
repeats.) A portion of the waveform of signal 1908 is shown in an
expanded view as waveform 1910 of FIG. 19E. The first three
sinusoidal components of waveform 1910 (FIG. 19E) are depicted as
waveforms 1912a, b, & c of FIG. 19F and waveforms 1914a, b,
& c of FIG. 19G. (In the examples of FIGS. 19F & G, the
three sinusoidal components are shown separately. In actuality,
these waveforms, along with all the other sinusoidal components
which are not shown, occur simultaneously, as seen in FIG. 19H.
Note that in FIG. 19H, the waveforms are shown simultaneously, but
are not shown summed. If waveforms 1912 and 1914 were shown summed,
they would, in the limit, i.e., with an infinite number of
sinusoidal components, be identical to the periodic waveform 1910
of FIG. 19E. For ease of illustration, only the first three of the
infinite number of sinusoidal components are shown.) These
sinusoidal waves are called harmonics, and their existence can be
demonstrated both graphically and mathematically. Each harmonic
(waveforms 1912a, b, & c and 1914a, b, & c) has the same
information content as does waveform 1910 (which has the same
information as the corresponding portion of waveform 1908).
Accordingly, the information content of waveform 1908 can be
obtained from any of its harmonics. As the harmonics have
frequencies that are integer multiples of the repetition frequency
of signal 1908, and since they have the same information content as
signal 1908 (as just stated), the harmonics each represent an
up-converted representation of signal 1908. Some of the harmonics
are at desired frequencies (such as the frequencies desired to be
transmitted). These harmonics are called "desired harmonics" or
"wanted harmonics." According to the invention, desired harmonics
have sufficient amplitude for accomplishing the desired processing
(i.e., being transmitted). Other harmonics are not at the desired
frequencies. These harmonics are called "undesired harmonics" or
"unwanted harmonics."
[0284] In step 910, any unwanted harmonics of the continuous
periodic waveform of signal 1908 are filtered out (for example, any
harmonics that are not at frequencies desired to be transmitted).
In the example of FIG. 19, the first and second harmonics (i.e.,
those depicted by waveforms 1912a & b of FIG. 19F and 1914a
& b of FIG. 19G) are the unwanted harmonics. In step 912, the
remaining harmonic, in the example of FIG. 19, the third harmonic
(i.e., those depicted by waveforms 1912c of FIG. 19F and 1914c of
FIG. 19G), is transmitted. This is depicted by waveform 1918 of
FIG. 19I. In the example of FIG. 19, only three harmonics are
shown, and the lowest two are filtered out to leave the third
harmonic as the desired harmonic. In actual practice, there are an
infinite number of harmonics, and the filtering can be made to
remove unwanted harmonics that are both lower in frequency than the
desired harmonic as well as those that are higher in frequency than
the desired harmonic.
3.1.2 Structural Description
[0285] FIG. 10 is a block diagram of an up-conversion system
according to an embodiment of the invention. This embodiment of the
up-conversion system is shown as a transmitter 1000. Transmitter
1000 includes an acceptance module 1004, a harmonic generation and
extraction module 1006, and a transmission module 1008 that accepts
an information signal 1002 and outputs a transmitted signal
1014.
[0286] Preferably, the acceptance module 1004, harmonic generation
and extraction module 1006, and transmission module 1008 process
the information signal in the manner shown in the operational
flowchart 900. In other words, transmitter 1000 is the structural
embodiment for performing the operational steps of flowchart 900.
However, it should be understood that the scope and spirit of the
present invention includes other structural embodiments for
performing the steps of flowchart 900. The specifics of these other
structural embodiments will be apparent to persons skilled in the
relevant art(s) based on the discussion contained herein.
[0287] The operation of the transmitter 1000 will now be described
in detail with reference to the flowchart 900. In step 902, an
information signal 1002 (for example, see FIG. 19A) from a source
(not shown) is routed to acceptance module 1004. In step 904, an
oscillating signal (for example, see FIG. 19B) is generated and in
step 906, it is modulated, thereby producing a modulated signal
1010 (for an example of FM, see FIG. 19C). The oscillating signal
can be modulated using any modulation technique, examples of which
are described below. In step 908, the harmonic generation and
extraction module (HGEM) generates a harmonically rich signal with
a continuous and periodic waveform (an example of FM can be seen in
FIG. 19D). This waveform is preferably a rectangular wave, such as
a square wave or a pulse (although, the invention is not limited to
this embodiment), and is comprised of a plurality of sinusoidal
waves whose frequencies are integer multiples of the fundamental
frequency of the waveform. These sinusoidal waves are referred to
as the harmonics of the underlying waveform. A Fourier series
analysis can be used to determine the amplitude of each harmonic
(for example, see FIGS. 19F and 19G). In step 910, a filter (not
shown) within HGEM 1006 filters out the undesired frequencies
(harmonics), and outputs an electromagnetic (EM) signal 1012 at the
desired frequency (for example, see FIG. 19I). In step 912, EM
signal 1012 is routed to transmission module 1008 (optional), where
it is prepared for transmission. The transmission module 1008 then
outputs a transmitted signal 1014.
3.2 Exemplary Embodiments
[0288] Various embodiments related to the method(s) and
structure(s) described above are presented in this section (and its
subsections). These embodiments are described herein for purposes
of illustration, and not limitation. The invention is not limited
to these embodiments. Alternate embodiments (including equivalents,
extensions, variations, deviations, etc., of the embodiments
described herein) will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. The
invention is intended and adapted to include such alternate
embodiments.
3.2.1 First Embodiment
Frequency Modulation (FM) Mode
[0289] In this embodiment, an information signal is accepted and a
modulated signal whose frequency varies as a function of the
information signal results.
[0290] 3.2.1.1 Operational Description.
[0291] The flow chart of FIG. 11 demonstrates the method of
operation of a transmitter in the frequency modulation (FM) mode
according to an embodiment of the present invention. As stated
above, the representative waveforms shown in FIG. 19 depict the
invention operating as a transmitter in the FM mode.
[0292] In step 1102, an information signal 1902 (FIG. 19A) is
generated by a source by any means and/or process. (Information
signal 1902 is a baseband signal, and, because it is used to
modulate a signal, may also be referred to as a modulating baseband
signal 1902.) Information signal 1902 may be, for example, analog,
digital, or any combination thereof. The signals shown in FIG. 19
depict a digital information signal wherein the information is
represented by discrete states of the signal. It will be apparent
to persons skilled in the relevant art(s) that the invention is
also adapted to working with an analog information signal wherein
the information is represented by a continuously varying signal. In
step 1104, information signal 1902 modulates an oscillating signal
1904 (FIG. 19B). The result of this modulation is the modulated
signal 1906 (FIG. 19C) as indicated in block 1106. Modulated signal
1906 has a frequency that varies as a function of information
signal 1902 and is referred to as an FM signal.
[0293] In step 1108, a harmonically rich signal with a continuous
periodic waveform, shown in FIG. 19D as rectangular waveform 1908,
is generated. Rectangular waveform 1908 is generated using the
modulated signal 1906. One skilled in the relevant art(s) will
recognize the physical limitations to and mathematical obstacles
against achieving an exact or perfect rectangular waveform and it
is not the intent of the present invention that a perfect
rectangular waveform be generated or needed. Again, as stated
above, for ease of discussion, the term "rectangular waveform" will
be used to refer to waveforms that are substantially rectangular.
In a similar manner, the term "square wave" will refer to those
waveforms that are substantially square and it is not the intent of
the present invention that a perfect square wave be generated or
needed. A portion of rectangular waveform 1908 is shown in an
expanded view as periodic waveform 1910 in FIG. 19E. The first part
of waveform 1910 is designated "signal A" and represents
information signal 1902 being "high," and the second part of
waveform 1910 is designated "signal B" and information signal 1902
being "low." It should be noted that this convention is used for
illustrative purposes only, and alternatively, other conventions
could be used.
[0294] As stated before, a continuous and periodic waveform, such
as a rectangular wave 1908 as indicated in block 1110 of flowchart
1100, has sinusoidal components (harmonics) at frequencies that are
integer multiples of the fundamental frequency of the underlying
waveform (i.e., at the Fourier component frequencies). Three
harmonics of periodic waveform 1910 are shown separately, in
expanded views, in FIGS. 19F and 19G. Since waveform 1910 (and also
waveform 1908) is shown as a square wave in this exemplary
embodiment, only the odd harmonics are present, i.e., the first,
third, fifth, seventh, etc. As shown in FIG. 19, if rectangular
waveform 1908 has a fundamental frequency of f.sub.1 (also known as
the first harmonic), the third harmonic will have a frequency of
3f.sub.1, the fifth harmonic will have a frequency of 5f.sub.1, and
so on. The first, third, and fifth harmonics of signal A are shown
as waveforms 1912a, 1912b, and 1912c of FIG. 19F, and the first,
third, and fifth harmonics of signal B are shown as waveforms
1914a, 1914b, and 1914c of FIG. 19G. In actuality, these harmonics
(as well as all of the higher order harmonics) occur
simultaneously, as shown by waveform 1916 of FIG. 19H. Note that if
all of the harmonic components of FIG. 19H were shown summed
together with all of the higher harmonics (i.e., the seventh, the
ninth, etc.) the resulting waveform would, in the limit, be
identical to waveform 1910.
[0295] In step 1112, the unwanted frequencies of waveform 1916 are
removed. In the example of FIG. 19, the first and third harmonics
are shown to be removed, and as indicated in block 1114, the
remaining waveform 1918 (i.e., waveforms 1912c and 1914c) is at the
desired EM frequency. Although not shown, the higher harmonics
(e.g., the seventh, ninth, etc.) are also removed.
[0296] The EM signal, shown here as remaining waveform 1918, is
prepared for transmission in step 1116, and in step 1118, the EM
signal is transmitted.
[0297] 3.2.1.2 Structural Description.
[0298] FIG. 12 is a block diagram of a transmitter according to an
embodiment of the invention. This embodiment of the transmitter is
shown as an FM transmitter 1200. FM transmitter 1200 includes a
voltage controlled oscillator (VCO) 1204, a switch module 1214, a
filter 1218, and a transmission module 1222 that accepts an
information signal 1202 and outputs a transmitted signal 1224. The
operation and structure of exemplary components are described
below: an exemplary VCO is described below at sections
3.3.1-3.3.1.2; an exemplary switch module is described below at
sections 3.3.6-3.3.6.2; an exemplary filter is described below at
sections 3.3.9-3.3.9.2; and an exemplary transmission module is
described below at sections 3.3.10-3.3.10.2.
[0299] Preferably, the voltage controlled oscillator 1204, switch
module 1214, filter 1218, and transmission module 1222 process the
information signal in the manner shown in the operational flowchart
1100. In other words, FM transmitter 1200 is the structural
embodiment for performing the operational steps of flowchart 1100.
However, it should be understood that the scope and spirit of the
present invention includes other structural embodiments for
performing the steps of flowchart 1100. The specifics of these
other structural embodiments will be apparent to persons skilled in
the relevant art(s) based on the discussion contained herein.
[0300] The operation of the transmitter 1200 will now be described
in detail with reference to the flowchart 1100. In step 1102, an
information signal 1202 (for example, see FIG. 19A) from a source
(not shown) is routed to VCO 1204. In step 1104, an oscillating
signal (for example, see FIG. 19B) is generated and modulated,
thereby producing a frequency modulated signal 1210 (for example,
see FIG. 19C). In step 1108, the switch module 1214 generates a
harmonically rich signal 1216 with a continuous and periodic
waveform (for example, see FIG. 19D). This waveform is preferably a
rectangular wave, such as a square wave or a pulse (although, the
invention is not limited to this embodiment), and is comprised of a
plurality of sinusoidal waves whose frequencies are integer
multiples of the fundamental frequency of the waveform. These
sinusoidal waves are referred to as the harmonics of the underlying
waveform, and a Fourier analysis will determine the amplitude of
each harmonic (for example, see FIGS. 19F and 19G). In step 1112, a
filter 1218 filters out the undesired frequencies (harmonics), and
outputs an electromagnetic (EM) signal 1220 at the desired harmonic
frequency (for example, see FIG. 19I). In step 1116, EM signal 1220
is routed to transmission module 1222 (optional), where it is
prepared for transmission. In step 1118, transmission module 1222
outputs a transmitted signal 1224.
3.2.2 Second Embodiment
Phase Modulation (PM) Mode
[0301] In this embodiment, an information signal is accepted and a
modulated signal whose phase varies as a function of the
information signal is transmitted.
[0302] 3.2.2.1 Operational Description.
[0303] The flow chart of FIG. 13 demonstrates the method of
operation of the transmitter in the phase modulation (PM) mode. The
representative waveforms shown in FIG. 44 depict the invention
operating as a transmitter in the PM mode.
[0304] In step 1302, an information signal 4402 (FIG. 44A) is
generated by a source. Information signal 4402 may be, for example,
analog, digital, or any combination thereof. The signals shown in
FIG. 44 depict a digital information signal wherein the information
is represented by discrete states of the signal. It will be
apparent to persons skilled in the relevant art(s) that the
invention is also adapted to working with an analog information
signal wherein the information is represented by a continuously
varying signal. In step 1304, an oscillating signal 4404 is
generated and in step 1306, the oscillating signal 4404 (FIG. 44B)
is modulated by the information signal 4402, resulting in the
modulated signal 4406 (FIG. 44C) as indicated in block 1308. The
phase of this modulated signal 4406 is varied as a function of the
information signal 4402.
[0305] A harmonically rich signal 4408 (FIG. 44D) with a continuous
periodic waveform is generated at step 1310 using modulated signal
4406. Harmonically rich signal 4408 is a substantially rectangular
waveform. One skilled in the relevant art(s) will recognize the
physical limitations to and mathematical obstacles against
achieving an exact or perfect rectangular waveform and it is not
the intent of the present invention that a perfect rectangular
waveform be generated or needed. Again, as stated above, for ease
of discussion, the term "rectangular waveform" will be used to
refer to waveforms that are substantially rectangular. In a similar
manner, the term "square wave" will refer to those waveforms that
are substantially square and it is not the intent of the present
invention that a perfect square wave be generated or needed. As
stated before, a continuous and periodic waveform, such as the
harmonically rich signal 4408 as indicated in block 1312, has
sinusoidal components (harmonics) at frequencies that are integer
multiples of the fundamental frequency of the underlying waveform
(the Fourier component frequencies). The first three harmonic
waveforms are shown in FIGS. 44E, 44F, and 44G. In actual fact,
there are an infinite number of harmonics. In step 1314, the
unwanted frequencies are removed, and as indicated in block 1316,
the remaining frequency is at the desired EM output. As an example,
the first (fundamental) harmonic 4410 and the second harmonic 4412
along with the fourth, fifth, etc., harmonics (not shown) might be
filtered out, leaving the third harmonic 4414 as the desired EM
signal as indicated in block 1316.
[0306] The EM signal is prepared for transmission in step 1318, and
in step 1320, the EM signal is transmitted.
[0307] 3.2.2.2 Structural Description.
[0308] FIG. 14 is a block diagram of a transmitter according to an
embodiment of the invention. This embodiment of the transmitter is
shown as a PM transmitter 1400. PM transmitter 1400 includes a
local oscillator 1406, a phase modulator 1404, a switch module
1410, a filter 1414, and a transmission module 1418 that accepts an
information signal 1402 and outputs a transmitted signal 1420. The
operation and structure of exemplary components are described
below: an exemplary phase modulator is described below at sections
3.3.4-3.3.4.2; an exemplary local oscillator is described below at
sections 3.3.2-3.3.2.2; an exemplary switch module is described
below at sections 3.3.6-3.3.6.2; an exemplary filter is described
below at sections 3.3.9-3.3.9.2; and an exemplary transmission
module is described below at sections 3.3.10-3.3.10.2.
[0309] Preferably, the local oscillator 1406, phase modulator 1404,
switch module 1410, filter 1414, and transmission module 1418
process the information signal in the manner shown in the
operational flowchart 1300. In other words, PM transmitter 1400 is
the structural embodiment for performing the operational steps of
flowchart 1300. However, it should be understood that the scope and
spirit of the present invention includes other structural
embodiments for performing the steps of flowchart 1300. The
specifics of these other structural embodiments will be apparent to
persons skilled in the relevant art(s) based on the discussion
contained herein.
[0310] The operation of the transmitter 1400 will now be described
in detail with reference to the flowchart 1300. In step 1302, an
information signal 1402 (for example, see FIG. 44A) from a source
(not shown) is routed to phase modulator 1404. In step 1304, an
oscillating signal from local oscillator 1406 (for example, see
FIG. 44B) is generated and modulated, thereby producing a modulated
signal 1408 (for example, see FIG. 44C). In step 1310, the switch
module 1410 generates a harmonically rich signal 1412 with a
continuous and periodic waveform (for example, see FIG. 44D). This
waveform is preferably a rectangular wave, such as a square wave or
a pulse (although, the invention is not limited to this
embodiment), and is comprised of a plurality of sinusoidal waves
whose frequencies are integer multiples of the fundamental
frequency of the waveform. These sinusoidal waves are referred to
as the harmonics of the underlying waveform, and a Fourier analysis
will determine the amplitude of each harmonic (for an example of
the first three harmonics, see FIGS. 44E, 44F, and 44G). In step
1314, a filter 1414 filters out the undesired harmonic frequencies
(for example, the first harmonic 4410, the second harmonic 4412,
and the fourth, fifth, etc., harmonics, not shown), and outputs an
electromagnetic (EM) signal 1416 at the desired harmonic frequency
(for example, the third harmonic, see FIG. 44G). In step 1318, EM
signal 1416 is routed to transmission module 1418 (optional), where
it is prepared for transmission. In step 1320, the transmission
module 1418 outputs a transmitted signal 1420.
3.2.3 Third Embodiment
Amplitude Modulation (AM) Mode
[0311] In this embodiment, an information signal is accepted and a
modulated signal whose amplitude varies as a function of the
information signal is transmitted.
[0312] 3.2.3.1 Operational Description.
[0313] The flow chart of FIG. 15 demonstrates the method of
operation of the transmitter in the amplitude modulation (AM) mode.
The representative waveforms shown in FIG. 45 depict the invention
operating as a transmitter in the AM mode.
[0314] In step 1502, an information signal 4502 (FIG. 45A) is
generated by a source. Information signal 4502 may be, for example,
analog, digital, or any combination thereof. The signals shown in
FIG. 45 depict a digital information signal wherein the information
is represented by discrete states of the signal. It will be
apparent to persons skilled in the relevant art(s) that the
invention is also adapted to working with an analog information
signal wherein the information is represented by a continuously
varying signal. In step 1504, a "reference signal" is created,
which, as indicated in block 1506, has an amplitude that is a
function of the information signal 4502. In one embodiment of the
invention, the reference signal is created by combining the
information signal 4502 with a bias signal. In another embodiment
of the invention, the reference signal is comprised of only the
information signal 4502. One skilled in the relevant art(s) will
recognize that any number of embodiments exist wherein the
reference signal will vary as a function of the information
signal.
[0315] An oscillating signal 4504 (FIG. 45B) is generated at step
1508, and at step 1510, the reference signal (information signal
4502) is gated at a frequency that is a function of the oscillating
signal 4504. The gated referenced signal is a harmonically rich
signal 4506 (FIG. 45C) with a continuous periodic waveform and is
generated at step 1512. This harmonically rich signal 4506 as
indicated in block 1514 is substantially a rectangular wave which
has a fundamental frequency equal to the frequency at which the
reference signal (information signal 4502) is gated. In addition,
the rectangular wave has pulse amplitudes that are a function of
the amplitude of the reference signal (information signal 4502).
One skilled in the relevant art(s) will recognize the physical
limitations to and mathematical obstacles against achieving an
exact or perfect rectangular waveform and it is not the intent of
the present invention that a perfect rectangular waveform be
generated or needed. Again, as stated above, for ease of
discussion, the term "rectangular waveform" will be used to refer
to waveforms that are substantially rectangular. In a similar
manner, the term "square wave" will refer to those waveforms that
are substantially square and it is not the intent of the present
invention that a perfect square wave be generated or needed.
[0316] As stated before, a harmonically rich signal 4506, such as
the rectangular wave as indicated in block 1514, has sinusoidal
components (harmonics) at frequencies that are integer multiples of
the fundamental frequency of the underlying waveform (the Fourier
component frequencies). The first three harmonic waveforms are
shown in FIGS. 45D, 45E, and 45F. In fact, there are an infinite
number of harmonics. In step 1516, the unwanted frequencies are
removed, and as indicated in block 1518, the remaining frequency is
at the desired EM output. As an example, the first (fundamental)
harmonic 4510 and the second harmonic 4512 along with the fourth,
fifth, etc., harmonics (not shown) might be filtered out leaving
the third harmonic 4514 as the desired EM signal as indicated in
block 1518.
[0317] The EM signal is prepared for transmission in step 1520, and
in step 1522, the EM signal is transmitted.
[0318] 3.2.3.2 Structural Description.
[0319] FIG. 16 is a block diagram of a transmitter according to an
embodiment of the invention. This embodiment of the transmitter is
shown as an AM transmitter 1600. AM transmitter 1600 includes a
local oscillator 1610, a summing module 1606, a switch module 1614,
a filter 1618, and a transmission module 1622 that accepts an
information signal 1602 and outputs a transmitted signal 1624. The
operation and structure of exemplary components are described
below: an exemplary local oscillator is described below at sections
3.3.2-3.3.2.2; an exemplary a switch module is described below at
sections 3.3.7-3.3.7.2; an exemplary filter is described below at
sections 3.3.9-3.3.9.2; and an exemplary transmission module is
described below at sections 3.3.10-3.3.10.2.
[0320] Preferably, the local oscillator 1610, summing module 1606,
switch module 1614, filter 1618, and transmission module 1622
process an information signal 1602 in the manner shown in the
operational flowchart 1500. In other words, AM transmitter 1600 is
the structural embodiment for performing the operational steps of
flowchart 1500. However, it should be understood that the scope and
spirit of the present invention includes other structural
embodiments for performing the steps of flowchart 1500. The
specifics of these other structural embodiments will be apparent to
persons skilled in the relevant art(s) based on the discussion
contained herein.
[0321] The operation of the transmitter 1600 will now be described
in detail with reference to the flowchart 1500. In step 1502,
information signal 1602 (for example, see FIG. 45A) from a source
(not shown) is routed to summing module 1606 (if required), thereby
producing a reference signal 1608. In step 1508, an oscillating
signal 1612 is generated by local oscillator 1610 (for example, see
FIG. 45B) and in step 1510, switch module 1614 gates the reference
voltage 1608 at a rate that is a function of the oscillating signal
1612. The result of the gating is a harmonically rich signal 1616
(for example, see FIG. 45C) with a continuous and periodic
waveform. This waveform is preferably a rectangular wave, such as a
square wave or a pulse (although, the invention is not limited to
this embodiment), and is comprised of a plurality of sinusoidal
waves whose frequencies are integer multiples of the fundamental
frequency of the waveform. These sinusoidal waves are referred to
as the harmonics of the underlying waveform, and a Fourier analysis
will determine the relative amplitude of each harmonic (for an
example of the first three harmonics, see FIGS. 45D, 45E, and 45F).
When amplitude modulation is applied, the amplitude of the pulses
in rectangular waveform 1616 vary as a function of reference signal
1608. As a result, this change in amplitude of the pulses has a
proportional effect on the absolute amplitude of all of the
harmonics. In other words, the AM is embedded on top of each of the
harmonics. In step 1516, a filter 1618 filters out the undesired
harmonic frequencies (for example, the first harmonic 4510, the
second harmonic 4512, and the fourth, fifth, etc., harmonics, not
shown), and outputs an electromagnetic (EM) signal 1620 at the
desired harmonic frequency (for example, the third harmonic, see
FIG. 45F). In step 1520, EM signal 1620 is routed to transmission
module 1622 (optional), where it is prepared for transmission. In
step 1522, the transmission module 1622 outputs a transmitted
signal 1624.
[0322] Note that the description of the AM embodiment given herein
shows the information signal being gated, thus applying the
amplitude modulation to the harmonically rich signal. However, is
would be apparent based on the teachings contained herein, that the
information signal can be modulated onto the harmonically rich
signal or onto a filtered harmonic at any point in the circuit.
3.2.4 Fourth Embodiment
In-Phase/Quadrature-Phase Modulation ("I/Q") Mode
[0323] In-phase/quadrature-phase modulation ("I/Q") is a specific
subset of a phase modulation (PM) embodiment. Because "I/Q" is so
pervasive, it is described herein as a separate embodiment.
However, it should be remembered that since it is a specific subset
of PM, the characteristics of PM also apply to "I/Q."
[0324] In this embodiment, two information signals are accepted. An
in-phase signal ("I") is modulated such that its phase varies as a
function of one of the information signals, and a quadrature-phase
signal ("Q") is modulated such that its phase varies as a function
of the other information signal. The two modulated signals are
combined to form an "I/Q" modulated signal and transmitted.
[0325] 3.2.4.1 Operational Description.
[0326] The flow chart of FIG. 17 demonstrates the method of
operation of the transmitter in the in-phase/quadrature-phase
modulation ("I/Q") mode. In step 1702, a first information signal
is generated by a first source. This information signal may be
analog, digital, or any combination thereof. In step 1710, an
in-phase oscillating signal (referred to as the "I" signal) is
generated and in step 1704, it is modulated by the first
information signal. This results in the "I" modulated signal as
indicated in block 1706 wherein the phase of the "I" modulated
signal is varied as a function of the first information signal.
[0327] In step 1714, a second information signal is generated.
Again, this signal may be analog, digital, or any combination
thereof, and may be different than the first information signal. In
step 1712, the phase of "I" oscillating signal generated in step
1710 is shifted, creating a quadrature-phase oscillating signal
(referred to as the "Q" signal). In step 1716, the "Q" signal is
modulated by the second information signal. This results in the "Q"
modulated signal as indicated in block 1718 wherein the phase of
the "Q" modulated signal is varied as a function of the second
information signal.
[0328] An "I" signal with a continuous periodic waveform is
generated at step 1708 using the "I" modulated signal, and a "Q"
signal with a continuous periodic waveform is generated at step
1720 using the "Q" modulated signal. In step 1722, the "I" periodic
waveform and the "Q" periodic waveform are combined forming what is
referred to as the "I/Q" periodic waveform as indicated in block
1724. As stated before, a continuous and periodic waveform, such as
a "I/Q" rectangular wave as indicated in block 1724, has sinusoidal
components (harmonics) at frequencies that are integer multiples of
the fundamental frequency of the underlying waveform (the Fourier
component frequencies). In step 1726, the unwanted frequencies are
removed, and as indicated in block 1728, the remaining frequency is
at the desired EM output.
[0329] The "I/Q" EM signal is prepared for transmission in step
1730, and in step 1732, the "I/Q" EM signal is transmitted.
[0330] 3.2.4.2 Structural Description.
[0331] FIG. 18 is a block diagram of a transmitter according to an
embodiment of the invention. This embodiment of the transmitter is
shown as an "I/Q" transmitter 1800. "I/Q" transmitter 1800 includes
a local oscillator 1806, a phase shifter 1810, two phase modulators
1804 & 1816, two switch modules 1822 & 1828, a summer 1832,
a filter 1836, and a transmission module 1840. The "I/Q"
transmitter accepts two information signals 1802 & 1814 and
outputs a transmitted signal 1420. The operation and structure of
exemplary components are described below: an exemplary phase
modulator is described below at sections 3.3.4-3.3.4.2; an
exemplary local oscillator is described below at sections
3.3.2-3.3.2.2; an exemplary phase shifter is described below at
sections 3.3.3-3.3.3.2; an exemplary switch module is described
below at sections 3.3.6-3.3.6.2; an exemplary summer is described
below at sections 3.3.8-3.3.8.2; an exemplary filter is described
below at sections 3.3.9-3.3.9.2; and an exemplary transmission
module is described below at sections 3.3.10-3.3.10.2.
[0332] Preferably, the local oscillator 1806, phase shifter 1810,
phase modulators 1804 & 1816, switch modules 1822 & 1828,
summer 1832, filter 1836, and transmission module 1840 process the
information signal in the manner shown in the operational flowchart
1700. In other words, "I/Q" transmitter 1800 is the structural
embodiment for performing the operational steps of flowchart 1700.
However, it should be understood that the scope and spirit of the
present invention includes other structural embodiments for
performing the steps of flowchart 1700. The specifics of these
other structural embodiments will be apparent to persons skilled in
the relevant art(s) based on the discussion contained herein.
[0333] The operation of the transmitter 1800 will now be described
in detail with reference to the flowchart 1700 In step 1702, a
first information signal 1802 from a source (not shown) is routed
to the first phase modulator 1804. In step 1710, an "I" oscillating
signal 1808 from local oscillator 1806 is generated and in step
1704, "I" oscillating signal 1808 is modulated by first information
signal 1802 in the first phase modulator 1804, thereby producing an
"I" modulated signal 1820. In step 1708, the first switch module
1822 generates a harmonically rich "I" signal 1824 with a
continuous and periodic waveform.
[0334] In step 1714, a second information signal 1814 from a source
(not shown) is routed to the second phase modulator 1816. In step
1712, the phase of oscillating signal 1808 is shifted by phase
shifter 1810 to create "Q" oscillating signal 1812. In step 1716,
"Q" oscillating signal 1812 is modulated by second information
signal 1814 in the second phase modulator 1816, thereby producing
"Q" modulated signal 1826. In step 1720, the second switch module
1828 generates a harmonically rich "Q" signal 1830 with a
continuous and periodic waveform. Harmonically rich "I" signal 1824
and harmonically rich "Q" signal 1830 are preferably rectangular
waves, such as square waves or pulses (although, the invention is
not limited to this embodiment), and are comprised of pluralities
of sinusoidal waves whose frequencies are integer multiples of the
fundamental frequency of the waveforms. These sinusoidal waves are
referred to as the harmonics of the underlying waveforms, and a
Fourier analysis will determine the amplitude of each harmonic.
[0335] In step 1722, harmonically rich "I" signal 1824 and
harmonically rich "Q" signal 1830 are combined by summer 1832 to
create harmonically rich "I/Q" signal 1834. In step 1726, a filter
1836 filters out the undesired harmonic frequencies, and outputs an
"I/Q" electromagnetic (EM) signal 1838 at the desired harmonic
frequency. In step 1730, "I/Q" EM signal 1838 is routed to
transmission module 1840 (optional), where it is prepared for
transmission. In step 1732, the transmission module 1840 outputs a
transmitted signal 1842.
[0336] It will be apparent to those skilled in the relevant art(s)
that an alternate embodiment exists wherein the harmonically rich
"I" signal 1824 and the harmonically rich "Q" signal 1830 may be
filtered before they are summed, and further, another alternate
embodiment exists wherein "I" modulated signal 1820 and "Q"
modulated signal 1826 may be summed to create an "I/Q" modulated
signal before being routed to a switch module.
3.2.5 Other Embodiments
[0337] Other embodiments of the up-converter of the present
invention being used as a transmitter (or in other applications)
may use subsets and combinations of modulation techniques, and may
include modulating one or more information signals as part of the
up-conversion process.
[0338] 3.2.5.1 Combination of Modulation Techniques
[0339] Combinations of modulation techniques that would be apparent
to those skilled in the relevant art(s) based on the teachings
disclosed herein include, but are not limited to, quadrature
amplitude modulation (QAM), and embedding two forms of modulation
onto a signal for up-conversion.
[0340] An exemplary circuit diagram illustrating the combination of
two modulations is found in FIG. 62. This example uses AM combined
with PM. The waveforms shown in FIG. 63 illustrate the phase
modulation of a digital information signal "A" 6202 combined with
the amplitude modulation of an analog information signal "B" 6204.
An oscillating signal 6216 (FIG. 63B) and information signal "A"
6202 (FIG. 63A) are received by phase modulator 1404, thereby
creating a phase modulated signal 6208 (FIG. 63C). Note that for
illustrative purposes, and not limiting, the information signal is
shown as a digital signal, and the phase modulation is shown as
shifting the phase of the oscillating signal by 180.degree.. Those
skilled in the relevant art(s) will appreciate that the information
signal could be analog (although typically it is digital), and that
phase modulations other than 180.degree. may also be used. FIG. 62
shows a pulse shaper 6216 receiving phase modulated signal 6208 and
outputting a pulse-shaped PM signal 6210. The pulse shaper is
optional, depending on the selection and design of the phase
modulator 1404. Information signal "B" 6304 and bias signal 1604
(if required) are combined by summing module 1606 (optional) to
create reference signal 6206 (FIG. 63E). Pulse-shaped PM signal
6210 is routed to switch module 1410, 1614 where it gates the
reference signal 6206 thereby producing a harmonically rich signal
6212 (FIG. 63F). It can be seen that the amplitude of harmonically
rich signal 6212 varies as a function of reference signal 6206, and
the period and pulse width of harmonically rich signal 6212 are
substantially the same as pulse-shaped PM signal 6210. FIG. 63 only
illustrates the fundamental and second harmonics of harmonically
rich signal 6212. In fact, there may be an infinite number of
harmonics, but for illustrative purposes (and not limiting) the
first two harmonics are sufficient to illustrate that both the
phase modulation and the amplitude modulation that are present on
the harmonically rich signal 6212 are also present on each of the
harmonics. Filter 1414, 1618 will remove the unwanted harmonics,
and a desired harmonic 6214 is routed to transmission module 1418,
1622 (optional) where it is prepared for transmission. Transmission
module 1418, 1622 then outputs a transmitted signal 1420, 1624.
Those skilled in the relevant art(s) will appreciate that these
examples are provided for illustrative purposes only and are not
limiting.
[0341] The embodiments described above are provided for purposes of
illustration. These embodiments are not intended to limit the
invention. Alternate embodiments, differing slightly or
substantially from those described herein, will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such alternate embodiments include, but are not
limited to, combinations of modulation techniques in an "I/Q" mode.
Such alternate embodiments fall within the scope and spirit of the
present invention.
[0342] 3.2.5.2 Modulation as Part of the Up-Conversion Process.
[0343] Alternate embodiments of the present invention include
implementations wherein one or more information signals are
modulated as part of the up-conversion process. For ease of
discussion, these implementations will be referred to as
"modulation embodiments" and will be discussed in more detail
below.
[0344] In a first modulation embodiment, one information signal is
phase modulated onto the carrier signal as part of the
up-conversion process. Two exemplary implementations of this
modulation embodiment are herein described. One involves using a
differentiation circuit and the other involves using parallel
switches that are controlled by signals that are 180.degree. out of
phase with each other.
[0345] In a second modulation embodiment, two information signals
are multiplied. As part of the up-conversion process, one signal is
phase modulated onto the carrier and the other signal is amplitude
modulated onto the carrier. Again, as described in the first
modulation embodiment above, two exemplary implementations of this
modulation embodiment are herein described.
[0346] In a third modulation embodiment, one information signal is
phase modulated onto the "I" phase of the carrier signal as part of
the up-conversion process and a second information signal is phase
modulated onto the "Q" phase of the carrier as part of the
up-conversion process. As described above, two exemplary
implementations of this modulation embodiment are herein
described.
[0347] In a fourth modulation embodiment, a first information
signal is multiplied with a second information signal, and the
result is modulated onto the "I" phase of a carrier as part of the
up-conversion process. The first information signal is phase
modulated and the second information signal is amplitude modulated.
Additionally, a third information signal is multiplied with a
fourth information signal, and the result is modulated onto the "Q"
phase of a carrier as part of the up-conversion process. The third
information signal is phased modulated and the fourth information
signal is amplitude modulated. As described above, two exemplary
implementations of this modulation embodiment are herein
described.
[0348] It is noted that the exemplary implementations are described
herein for illustrative purposes only. The invention is not limited
to these examples. Other implementations will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein.
[0349] One exemplary implementation of the first modulation
embodiment is shown in FIG. 65. An information signal 6502 is
routed through an optional filter 6504. This results in a filtered
information signal 6522. Typically, information signal 6502 (as
well as filtered information signal 6522) is a digital signal,
although the invention may work with analog signals. Filtered
information signal 6522 is connected through a load, shown as an
inductor 6506, to the first input of a switch 6512. The second
input of switch 6512 is connected to a reference 6514. In one
implementation, reference 6514 is at ground and, in a second
implementation, reference 6514 is at a non-zero voltage.
[0350] A local oscillator 6508 generates an oscillating signal
6526. The frequency of oscillating signal 6526 is a sub-harmonic of
the desired output frequency of the up-converter. Oscillating
signal 6526 is routed through a pulse shaper 6510. Pulse shaper
6510 is optional, and, when used, outputs a string of pulses 6528.
String of pulses 6528 is connected to the control input of switch
6512, and controls the frequency at which switch 6512 closes and
opens.
[0351] The first input of switch 6512 is also connected to the
input of a differentiation circuit 6516. Differentiation circuit
6516 is shown as being comprised of a capacitor 6518 in series and
a resistor 6520 shunted to ground. This circuit diagram is shown
for illustrative purposes only, and persons skilled in the relevant
art(s) will appreciate that other differentiating circuits may be
used. The output of differentiation circuit 6516 is a harmonically
rich signal 6524 that is phase modulated. Harmonically rich signal
6524 is comprised of a plurality of harmonics and is routed to a
filter 6530. Filter 6530 extracts one or more of the harmonics as
desired output signal 6532.
[0352] A second exemplary implementation of the first modulation
embodiment is shown in FIG. 67. An information signal 6702 is
routed through an optional filter 6704. This results in a filtered
information signal 6708. Typically, information signal 6702 (as
well as filtered information signal 6708) is a digital signal,
although the invention may work with analog signals. Filtered
information signal 6708 is connected to a buffer/inverter module
6706. Buffer/inverter module 6706 outputs a buffered information
signal 6710 and an inverted information signal 6712. Buffered
information signal 6710 is substantially the same as filtered
information signal 6708 and inverted information signal 6712 is
substantially equal to the inverse of buffered information signal
6710. A number of circuits, such as off-the-shelf buffers and
off-the-shelf inverters, or customer designed buffers and
inverters, can be used to accomplish the function of
buffer/inverter module 6706, as can be appreciated by those skilled
in the relevant art(s).
[0353] Buffered information signal 6710 is then routed through a
load, shown as an inductor 6730, to the first input of a switch
6726, and inverted information signal 6712 is routed through a
load, shown as an inductor 6732, to the first input of a switch
6728. The second input of switch 6726 and the second input of
switch 6728 are connected to a reference 6746. As shown in FIG. 67,
the second input of switch 6726 and the second input of switch 6728
are connected to the same reference 6746. Those skilled in the
relevant art(s) will understand that this does not need to be the
same reference. In one implementation, reference 6746 is at ground
and in another implementation reference 6746 is at a non-zero
voltage.
[0354] A local oscillator 6714 generates an oscillating signal
6716. The frequency of oscillating signal 6716 is preferably an odd
sub-harmonic of the desired output frequency of the up-converter.
Oscillating signal 6716 is routed through a 180.degree. phase
shifter 6718 to generate a phase shifted oscillating signal 6720.
Oscillating signal 6716 is also routed through a pulse shaper 6722,
and phase shifted oscillating signal 6720 is routed through a pulse
shaper 6724. Pulse shaper 6722 and pulse shaper 6724 are both
optional, and, when used, output a string of pulses 6748 and a
string of pulses 6750, respectively. String of pulses 6748 is
connected to the control input of switch 6726 and controls the
frequency at which switch 6726 closes and opens. String of pulses
6750 is connected to the control input of switch 6728 and controls
the frequency at which switch 6728 closes and opens.
[0355] A signal 6734 from the first input of switch 6726 and a
signal 6736 from the first input of switch 6728 are combined by a
summer 6738. The output of summer 6738 is a harmonically rich
signal 6740 that is phase modulated. Harmonically rich signal 6740
is comprised of a plurality of harmonics and is routed to a filter
6742. Filter 6742 extracts one or more of the harmonics as desired
output signal 6744.
[0356] One exemplary implementation of the second modulation
embodiment of the present invention is shown in FIG. 66 wherein a
multiplication, modulation, and harmonic generation module 6600
generates a signal that is phase and amplitude modulated, as
described below. A first information signal 6602 and a second
information signal 6604 are multiplied by a multiplier 6606. For
ease of discussion, and not meant to be limiting, first information
signal 6602 will be considered to be a digital signal, and second
information signal 6604 will be considered to be an analog signal.
The output of multiplier 6606 is a combined signal 6608. Combined
signal 6608 is preferably a digital signal having a baud rate
substantially the same as the baud rate of first information signal
6602 and whose bits have amplitudes that are a function of the
amplitude of second information signal 6604.
[0357] Combined signal 6608 is routed through an optional filter
6610. This results in a filtered combined signal 6612. Filtered
combined signal 6612 is connected through a load, shown as an
inductor 6614, to the first input of a switch 6616. The second
input of switch 6616 is connected to a reference 6626. Preferably,
reference 6626 is at the potential about which first information
signal 6602 switches. That is, if first information signal 6602 is
a digital signal whose "low" value is 0 volts and whose "high"
value is 5 volts, then reference 6626 will be between 0 and 5
volts, such as, for example, 2.5 volts. This example is for
illustrative purposes only, and is not meant to be limiting. A
person skilled in the relevant art(s) will understand that there
are a number of values for the "high," "low," and reference
voltages which will result in a phase shift of the carrier when the
"state" of the information signal crosses the reference
voltage.
[0358] A local oscillator 6618 generates an oscillating signal
6620. The frequency of oscillating signal 6620 is a sub-harmonic of
the desired output frequency of the up-converter. Oscillating
signal 6620 is routed through a pulse shaper 6622. Pulse shaper
6622 is optional, and, when used, outputs a string of pulses 6624.
String of pulses 6624 is connected to the control input of switch
6616, and controls the frequency at which switch 6616 closes and
opens.
[0359] The first input of switch 6616 is also connected to the
input of a differentiation circuit 6628. In FIG. 66,
differentiation circuit 6628 is shown as being comprised of a
capacitor 6630 in series and a resistor 6632 shunted to ground.
This circuit diagram is shown for illustrative purposes only, and
persons skilled in the art(s) will appreciate that other
differentiating circuits may be used. The output of differentiation
circuit 6628 is a harmonically rich signal 6634 that is both phase
and amplitude modulated. In summary, first information signal 6602,
the digital signal, phase modulates harmonically rich signal 6634,
and second information signal 6604, the analog signal, amplitude
modulates harmonically rich signal 6634.
[0360] Harmonically rich signal 6634 is comprised of a plurality of
harmonics and is routed to a filter 6636. Filter 6636 extracts one
or more of the harmonics as desired output signal 6638.
[0361] Although the discussion herein was directed toward a digital
and an analog signal, the invention is not limited to this
implementation. The output of differentiation circuit 6628 is such
that the phase modulation is a function of an information signal
whose high and low states are above and below the reference
voltage, and the amplitude modulation is a function of the
information signal whose voltage remains either above or below the
reference voltage, but does not cross it.
[0362] A second exemplary implementation of the second modulation
embodiment is shown in FIG. 68 wherein a multiplication,
modulation, and harmonic generation module 6800 generates a signal
that is phase and amplitude modulated, as described below. A first
information signal 6802 and a second information signal 6804 are
multiplied by a multiplier 6806. For ease of discussion, and not
meant to be limiting, first information signal 6802 will be
considered to be a digital signal, and second information signal
6804 will be considered to be an analog signal. The output of
multiplier 6806 is a combined signal 6808. Combined signal 6808 is
a digital signal having a baud rate substantially the same as the
baud rate of first information signal 6802 and whose bits have
amplitudes that are a function of the amplitude of second
information signal 6804.
[0363] Combined signal 6808 is routed through an optional filter
6810. This results in a filtered combined signal 6812. Filtered
combined signal 6812 is connected to a buffer/inverter module 6814.
Buffer/inverter module 6814 outputs a buffered combined signal 6820
and an inverted combined signal 6822. Buffered combined signal 6820
is substantially the same as filtered combined signal 6812 and
inverted combined signal 6822 is substantially equal to the inverse
of buffered combined signal 6820. A number of circuits, such as
off-the-shelf buffers and off-the-shelf inverters, or custom
designed buffers and inverters, can be used to accomplish the
function of buffer/inverter module 6814, as can be appreciated by
those skilled in the relevant art(s).
[0364] Buffered combined signal 6820 is then routed through a load,
shown as an inductor 6840, to the first input of a switch 6844, and
inverted combined signal 6822 is routed through a load, shown as an
inductor 6842, to the first input of a switch 6846. The second
input of switch 6844 and the second input of switch 6846 are
connected to a reference 6848. As shown in FIG. 68, the second
input of switch 6844 and the second input of switch 6846 are
connected to the same reference 6848. Those skilled in the relevant
art(s) will understand that this does not need to be the same
reference. Typically, reference 6848 is at the potential about
which first information signal 6802 switches. That is, if first
information signal 6802 is a digital signal whose "low" value is 0
volts and whose "high" value is 5 volts, then reference 6848 will
be between 0 and 5 volts, such as, for example, 2.5 volts. This
example is for illustrative purposes only, and is not meant to be
limiting. A person skilled in the relevant art(s) will understand
that there are a number of values for the "high," "low," and
reference voltages which will result in a phase shift of the
carrier when the "state" of the information signal crosses the
reference voltage.
[0365] A local oscillator 6824 generates an oscillating signal
6826. The frequency of oscillating signal 6826 is preferably an odd
sub-harmonic of the desired output frequency of the up-converter.
Oscillating signal 6826 is routed through a 180.degree. phase
shifter 6828 to generate a phase shifted oscillating signal 6830.
Oscillating signal 6826 is also routed through a pulse shaper 6832,
and phase shifted oscillating signal 6830 is routed through a pulse
shaper 6834. Pulse shaper 6832 and pulse shaper 6834 are both
optional, and, when used, output a string of pulses 6836 and a
string of pulses 6838, respectively. String of pulses 6836 is
connected to the control input of switch 6844 and controls the
frequency at which switch 6844 closes and opens. String of pulses
6838 is connected to the control input of switch 6846 and controls
the frequency at which switch 6846 closes and opens.
[0366] A signal 6850 from the first input of switch 6844 and a
signal 6852 from the first input of switch 6846 are combined by a
summer 6854. The output of summer 6854 is a harmonically rich
signal 6856 that is both phase and amplitude modulated. In summary,
first information signal 6802, the digital signal, phase modulates
harmonically rich signal 6854, and second information signal 6804,
the analog signal, amplitude modulates harmonically rich signal
6856.
[0367] Harmonically rich signal 6856 is comprised of a plurality of
harmonics and is routed to a filter 6858. Filter 6858 extracts one
or more of the harmonics as desired output signal 6860.
[0368] Although the discussion herein was directed toward a digital
and an analog signal, the invention is not limited to this
implementation. The output of the circuit is such that the phase
modulation is a function of an information signal whose high and
low states are above and below the reference voltage, and the
amplitude modulation is a function of the information signal whose
voltage remains either above or below the reference voltage, but
does not cross it. Thus the amplitude is preserved.
[0369] One exemplary implementation of the third modulation
embodiment is the "I/Q" embodiment shown in FIG. 69. A first
information signal 6902 is routed through an optional filter 6906.
This results in a first filtered information signal 6910.
Typically, first information signal 6902 (as well as first filtered
information signal 6910) is a digital signal, although the
invention may be able to operate with analog signals. First
filtered information signal 6910 is connected through a load, shown
as an inductor 6914, to the first input of a switch 6934. The
second input of switch 6934 is connected to a reference 6938. In
one implementation, reference 6938 is at ground and, in another
implementation, reference 6938 is at a non-zero voltage.
[0370] A second information signal 6904 is routed through an
optional filter 6908. This results in a second filtered information
signal 6912. Typically, second information signal 6904 (as well as
second filtered information signal 6912) is a digital signal,
although the invention may operate with analog signals. Second
filtered information signal 6912 is connected through a load, shown
as an inductor 6916, to the first input of a switch 6936. The
second input of switch 6936 is connected to a reference 6940. In
one implementation, reference 6940 is at ground and, in another
implementation, reference 6940 is at a non-zero voltage.
[0371] A local oscillator 6918 generates an in-phase, "I,"
oscillating signal 6920. The frequency of "I" oscillating signal
6920 is a sub-harmonic of the desired output frequency of the
up-converter. "I" oscillating signal 6920 is routed through a pulse
shaper 6926. Pulse shaper 6926 is optional, and, when used, outputs
an "I" string of pulses 6930. "I" string of pulses 6930 is
connected to the control input of switch 6934, and controls the
frequency at which switch 6934 closes and opens.
[0372] "I" oscillating signal 6920 is also routed through a
90.degree. phase shifter 6922. The output of 90.degree. phase
shifter 6922 is a quadrature-phase, "Q," oscillating signal 6924.
"Q" oscillating signal 6924 is routed through a pulse shaper 6928.
Pulse shaper 6928 is optional, and, when used, outputs a "Q" string
of pulses 6932. "Q" string of pulses 6932 is connected to the
control input of switch 6936, and controls the frequency at which
switch 6936 closes and opens.
[0373] The first input of switch 6934 is also connected to the
input of a differentiation circuit 6942. In FIG. 69,
differentiation circuit 6942 is shown as being comprised of a
capacitor 6944 in series and a resistor 6946 shunted to ground.
This circuit diagram is shown for illustrative purposes only, and
persons skilled in the art(s) will appreciate that other
differentiating circuits may be used. The output of differentiation
circuit 6942 is a harmonically rich "I" signal 6954 that is phase
modulated.
[0374] The first input of switch 6936 is also connected to the
input of a differentiation circuit 6948. In FIG. 69,
differentiation circuit 6948 is shown as being comprised of a
capacitor 6950 in series and a resistor 6952 shunted to ground.
This circuit diagram is shown for illustrative purposes only, and
persons skilled in the art(s) will appreciate that other
differentiating circuits may be used. The output of differentiation
circuit 6948 is a harmonically rich "Q" signal 6956 that is phase
modulated. Harmonically rich "I" signal 6954 and harmonically rich
"Q" signal 6956 are then routed to a summer 6958 where they are
combined. Summer 6958 outputs harmonically rich "I/Q" signal 6960.
Harmonically rich "I/Q" signal 6960 is comprised of a plurality of
harmonics and is routed to a filter 6962. Filter 6962 extracts one
or more of the harmonics as desired "I/Q" output signal 6964.
[0375] A second exemplary implementation of the third modulation
embodiment is the "I/Q" embodiment shown in FIG. 70. A first
information signal 7002 is routed to an optional filter 7006. This
results in a first filtered information signal 7008. Typically,
first information signal 7002 (as well as first filtered
information signal 7008) is a digital signal, although the
invention may operate with analog signals. First filtered
information signal 7008 is connected to a first buffer/inverter
module 7010. First buffer/inverter module 7010 outputs a buffered
first information signal 7016 and an inverted first information
signal 7018. Buffered first information signal 7016 is
substantially the same as first filtered information signal 7008
and inverted first information signal 7018 is substantially equal
to the inverse of buffered first information signal 7016. A number
of circuits, such as off-the-shelf buffers and off-the-shelf
inverters, or custom designed buffers and inverters, can be used to
accomplish the function of buffer/inverter module 7010, as can be
appreciated by those skilled in the relevant art(s).
[0376] Buffered first information signal 7016 is then routed
through a load, shown as an inductor 7066, to the first input of a
switch 7074, and inverted first information signal 7018 is routed
through a load, shown as an inductor 7068, to the first input of a
switch 7076. The second input of switch 7074 and the second input
of switch 7076 are connected to a reference 7082. As shown in FIG.
70, the second input of switch 7074 and the second input of switch
7076 are connected to the same reference 7082. Those skilled in the
relevant art(s) will understand that this does not need to be the
same reference. In one implementation, reference 7082 is at ground
and in another implementation reference 7082 is at a non-zero
voltage.
[0377] A second information signal 7004 is routed to an optional
filter 7036. This results in a second filtered information signal
7038. Typically, second information signal 7004 (as well as second
filtered information signal 7038) is a digital signal. Second
filtered information signal 7038 is connected to a second
buffer/inverter module 7040. Second buffer/inverter module 7040
outputs a buffered second information signal 7046 and an inverted
second information signal 7048. Buffered second information signal
7046 is substantially the same as second filtered information
signal 7038 and inverted second information signal 7048 is
substantially equal to the inverse of buffered second information
signal 7046. A number of circuits, such as off-the-shelf buffers
and off-the-shelf inverters, or custom designed buffers and
inverters, can be used to accomplish the function of
buffer/inverter module 7040, as can be appreciated by those skilled
in the relevant art(s).
[0378] Buffered second information signal 7046 is then routed
through a load, shown as an inductor 7070, to the first input of a
switch 7078, and inverted second information signal 7048 is routed
through a load, shown as an inductor 7072, to the first input of a
switch 7080. The second input of switch 7078 and the second input
of switch 7080 are connected to a reference 7084. As shown in FIG.
70, the second input of switch 7078 and the second input of switch
7080 are connected to the same reference 7084. Those skilled in the
relevant art(s) will understand that this does not need to be the
same reference. In one implementation, reference 7084 is at ground
and in another implementation reference 7084 is at a non-zero
voltage.
[0379] A local oscillator 7020 generates an in-phase, "I,"
oscillating signal 7022. The frequency of "I" oscillating signal
7022 is preferably an odd sub-harmonic of the desired output
frequency of the up-converter. "I" oscillating signal 7022 is
routed through a 180.degree. phase shifter 7024 to generate a
180.degree. phase shifted "I" oscillating signal 7026. "I"
oscillating signal 7022 is also routed through a pulse shaper 7028,
and 180.degree. phase shifted "I" oscillating signal 7026 is routed
through a pulse shaper 7030. Pulse shaper 7028 and pulse shaper
7030 are both optional, and, when used, output an "I" string of
pulses 7032 and an "I" string of pulses 7034, respectively. "I"
string of pulses 7032 is connected to the control input of switch
7074 and controls the frequency at which switch 7074 closes and
opens. "I" string of pulses 7034 is connected to the control input
of switch 7076 and controls the frequency at which switch 7076
closes and opens.
[0380] An "I" signal 7086 from the first input of switch 7074 and
an "I" signal 7088 from the first input of switch 7076 are combined
by a summer 7094. The output of summer 7094 is a harmonically rich
"I" signal 7081 that is phase modulated.
[0381] "I" oscillating signal 7022 is also routed through a
90.degree. phase shifter 7050 to generate a quadrature-phase, "Q,"
oscillating signal 7052. "Q" oscillating signal 7052 is routed
through a 180.degree. phase shifter 7054 to generate a 180.degree.
phase shifted "Q" oscillating signal 7056. "Q" oscillating signal
7052 is also routed through a pulse shaper 7058, and 180.degree.
phase shifted "Q" oscillating signal 7056 is routed through a pulse
shaper 7060. Pulse shaper 7058 and pulse shaper 7060 are both
optional, and, when used, output a "Q" string of pulses 7062 and a
"Q" string of pulses 7064, respectively. "Q" string of pulses 7062
is connected to the control input of switch 7078 and controls the
frequency at which switch 7078 closes and opens. "Q" string of
pulses 7064 is connected to the control input of switch 7080 and
controls the frequency at which switch 7080 closes and opens.
[0382] A "Q" signal 7090 from the first input of switch 7078 and a
"Q" signal 7092 from the first input of switch 7080 are combined by
a summer 7096. The output of summer 7096 is a harmonically rich "Q"
signal 7083 that is phase modulated.
[0383] Harmonically rich "I" signal 7081 and harmonically rich "Q"
signal 7083 are combined by summer 7085 which outputs a
harmonically rich "I/Q" signal 7087. Harmonically rich "I/Q" signal
7087 is comprised of a plurality of harmonics and is routed to a
filter 7089. Filter 7089 extracts one or more of the harmonics as
desired "I/Q" output signal 7098.
[0384] In the fourth modulation embodiment, four information
signals are modulated onto an "I/Q" carrier as shown in the example
of FIG. 71. A first information signal 7102 and a second
information signal 7104 are received by a multiplication,
modulation, and harmonic generation module 7110. A first exemplary
implementation of multiplication, modulation, and harmonic
generation module 7110 is shown in FIG. 66 as multiplication,
modulation, and harmonic generation module 6600 and a second
exemplary implementation of multiplication, modulation, and
harmonic generation module 7110 is shown in FIG. 68 as
multiplication, modulation, and harmonic generation module 6800.
Based on the teachings contained herein, other implementations will
be apparent to persons skilled in the relevant art(s).
[0385] A local oscillator 7114 generates an in-phase, "I,"
oscillating signal 7116. The frequency of "I" oscillating signal
7116 is a sub-harmonic frequency of the desired output frequency of
the up-converter, and is received by multiplication, modulation,
and harmonic generation module 7110, and causes it to output a
harmonically rich "I" signal 7122 that is both phase and amplitude
modulated. In the exemplary implementation wherein the
multiplication, modulation, and harmonic generation module 7110 is
multiplication, modulation, and harmonic generation module 6800,
the frequency of "I" oscillating signal 7116 is an odd sub-harmonic
of the desired output frequency.
[0386] A third information signal 7106 and a fourth information
signal 7108 are received by a multiplication, modulation, and
harmonic generation module 7112. A first exemplary implementation
of multiplication, modulation, and harmonic generation module 7112
is shown in FIG. 66 as multiplication, modulation, and harmonic
generation module 6600 and a second exemplary implementation of
multiplication, modulation, and harmonic generation module 7112 is
shown in FIG. 68 as multiplication, modulation, and harmonic
generation module 6800. Based on the teachings contained herein,
other implementations will be apparent to persons skilled in the
relevant art(s).
[0387] "I" oscillating signal 7116 is routed to 90.degree. phase
shifter 7118. The output of 90.degree. phase shifter 7118 is a
quadrature-phase, "Q," oscillating signal 7120. "Q" oscillating
signal 7120 is received by multiplication, modulation, and harmonic
generation module 7112 and causes it to output a harmonically rich
"Q" signal 7124 that is both phase and amplitude modulated.
[0388] Harmonically rich "I" signal 7122 and harmonically rich "Q"
signal 7124 are combined by a summer 7126. The output of summer
7126 is a harmonically rich "I/Q" signal 7128. Harmonically rich
"I/Q" signal 7128 is comprised of a plurality of harmonics and is
routed to a filter 7130. Filter 7130 extracts one or more of the
harmonics as desired "I/Q" output signal 7132. Desired "I/Q" output
signal 7132 is phase and amplitude modulated on the "I" phase and
phase and amplitude modulated on the "Q" phase, as discussed above
in the discussion of the second modulation embodiment.
3.3 Methods and Systems for Implementing the Embodiments
[0389] Exemplary operational and/or structural implementations
related to the method(s), structure(s), and/or embodiments
described above are presented in this section (and its
subsections). These components and methods are presented herein for
purposes of illustration, and not limitation. The invention is not
limited to the particular examples of components and methods
described herein. Alternatives (including equivalents, extensions,
variations, deviations, etc., of those described herein) will be
apparent to persons skilled in the relevant art(s) based on the
teachings contained herein. Such alternatives fall within the scope
and spirit of the present invention.
3.3.1 the Voltage Controlled Oscillator (Fm Mode)
[0390] As discussed above, the frequency modulation (FM) mode
embodiment of the invention uses a voltage controlled oscillator
(VCO). See, as an example, VCO 1204 in FIG. 12. The invention
supports numerous embodiments of the VCO. Exemplary embodiments of
the VCO 2304 (FIG. 23) are described below. However, it should be
understood that these examples are provided for illustrative
purposes only. The invention is not limited to these
embodiments.
[0391] 3.3.1.1 Operational Description.
[0392] The information signal 2302 is accepted and an oscillating
signal 2306 whose frequency varies as a function of the information
signal 2302 is created. Oscillating signal 2306 is also referred to
as frequency modulated intermediate signal 2306. The information
signal 2302 may be analog or digital or a combination thereof, and
may be conditioned to ensure it is within the desired range.
[0393] In the case where the information signal 2302 is digital,
the oscillating signal 2306 may vary between discrete frequencies.
For example, in a binary system, a first frequency corresponds to a
digital "high," and a second frequency corresponds to a digital
"low." Either frequency may correspond to the "high" or the "low,"
depending on the convention being used. This operation is referred
to as frequency shift keying (FSK) which is a subset of FM. If the
information signal 2302 is analog, the frequency of the oscillating
signal 2306 will vary as a function of that analog signal, and is
not limited to the subset of FSK described above.
[0394] The oscillating signal 2306 is a frequency modulated signal
which can be a sinusoidal wave, a rectangular wave, a triangular
wave, a pulse, or any other continuous and periodic waveform. As
stated above, one skilled in the relevant art(s) will recognize the
physical limitations to and mathematical obstacles against
achieving exact or perfect waveforms and it is not the intent of
the present invention that a perfect waveform be generated or
needed. Again, as stated above, for ease of discussion, the term
"rectangular waveform" will be used to refer to waveforms that are
substantially rectangular, the term "square wave" will refer to
those waveforms that are substantially square, the term "triangular
wave" will refer to those waveforms that are substantially
triangular, and the term "pulse" will refer to those waveforms that
are substantially a pulse, and it is not the intent of the present
invention that a perfect square wave, triangle wave, or pulse be
generated or needed.
[0395] 3.3.1.2 Structural Description.
[0396] The design and use of a voltage controlled oscillator 2304
is well known to those skilled in the relevant art(s). The VCO 2304
may be designed and fabricated from discrete components, or it may
be purchased "off the shelf." VCO 2304 accepts an information
signal 2302 from a source. The information signal 2302 is at
baseband and generally is an electrical signal within a prescribed
voltage range. If the information is digital, the voltage will be
at discrete levels. If the information is analog, the voltage will
be continuously variable between an upper and a lower level. The
VCO 2304 uses the voltage of the information signal 2302 to cause a
modulated oscillating signal 2306 to be output. The information
signal 2302, because it is a baseband signal and is used to
modulate the oscillating signal, may be referred to as the
modulating baseband signal 2302.
[0397] The frequency of the oscillating signal 2306 varies as a
function of the voltage of the modulating baseband signal 2302. If
the modulating baseband signal 2302 represents digital information,
the frequency of the oscillating signal 2306 will be at discrete
levels. If, on the other hand, the modulating baseband signal 2302
represents analog information, the frequency of the oscillating
signal 2306 will be continuously variable between its higher and
lower frequency limits. The oscillating signal 2306 can be a
sinusoidal wave, a rectangular wave, a triangular wave, a pulse, or
any other continuous and periodic waveform.
[0398] The frequency modulated oscillating signal 2306 may then be
used to drive a switch module 2802.
3.3.2 the Local Oscillator (PM, AM, and "I/Q" Modes)
[0399] As discussed above, the phase modulation (PM) and amplitude
modulation (AM) mode embodiments of the invention use a local
oscillator. So too does the in-phase/quadrature-phase modulation
("I/Q") mode embodiment. See, as an example, local oscillator 1406
in FIG. 14, local oscillator 1610 in FIG. 16, and local oscillator
1806 in FIG. 18. The invention supports numerous embodiments of the
local oscillator. Exemplary embodiments of the local oscillator
2402 (FIG. 24) are described below. However, it should be
understood that these examples are provided for illustrative
purposes only. The invention is not limited to these
embodiments.
[0400] 3.3.2.1 Operational Description.
[0401] An oscillating signal 2404 is generated. The frequency of
the signal 2404 may be selectable, but generally is not considered
to be "variable." That is, the frequency may be selected to be a
specific value for a specific implementation, but generally it does
not vary as a function of the information signal 2302 (i.e., the
modulating baseband signal).
[0402] The oscillating signal 2404 generally is a sinusoidal wave,
but it may also be a rectangular wave, a triangular wave, a pulse,
or any other continuous and periodic waveform. As stated above, one
skilled in the relevant art(s) will recognize the physical
limitations to and mathematical obstacles against achieving exact
or perfect waveforms and it is not the intent of the present
invention that a perfect waveform be generated or needed. Again, as
stated above, for ease of discussion, the term "rectangular
waveform" will be used to refer to waveforms that are substantially
rectangular, the term "square wave" will refer to those waveforms
that are substantially square, the term "triangular wave" will
refer to those waveforms that are substantially triangular, and the
term "pulse" will refer to those waveforms that are substantially a
pulse, and it is not the intent of the present invention that a
perfect square wave, triangle wave, or pulse be generated or
needed.
[0403] 3.3.2.2 Structural Description.
[0404] The design and use of a local oscillator 2402 is well known
to those skilled in the relevant art(s). A local oscillator 2402
may be designed and fabricated from discrete components or it may
be purchased "off the shelf." A local oscillator 2402 is generally
set to output a specific frequency. The output can be "fixed" or it
can be "selectable," based on the design of the circuit. If it is
fixed, the output is considered to be substantially a fixed
frequency that cannot be changed. If the output frequency is
selectable, the design of the circuit will allow a control signal
to be applied to the local oscillator 2402 to change the frequency
for different applications. However, the output frequency of a
local oscillator 2402 is not considered to be "variable" as a
function of an information signal 2302 such as the modulating
baseband signal 2302. (If it were desired for the output frequency
of an oscillator to be variable as a function of an information
signal, a VCO would preferably be used.) The oscillating signal
2404 generally is a sinusoidal wave, but it may also be a
rectangular wave, a triangular wave, a pulse, or any other
continuous and periodic waveform.
[0405] The output of a local oscillator 2402 may be an input to
other circuit components such as a phase modulator 2606, a phase
shifting circuit 2504, switch module 3102, etc.
3.3.3 the Phase Shifter ("I/Q" Mode)
[0406] As discussed above, the in-phase/quadrature-phase modulation
("I/Q") mode embodiment of the invention uses a phase shifter. See,
as an example, phase shifter 1810 in FIG. 18. The invention
supports numerous embodiments of the phase shifter. Exemplary
embodiments of the phase shifter 2504 (FIG. 25) are described
below. The invention is not limited to these embodiments. The
description contained herein is for a "90.degree. phase shifter."
The 90.degree. phase shifter is used for ease of explanation, and
one skilled in the relevant art(s) will understand that other phase
shifts can be used without departing from the intent of the present
invention.
[0407] 3.3.3.1 Operational Description.
[0408] An "in-phase" oscillating signal 2502 is received and a
"quadrature-phase" oscillating signal 2506 is output. If the
in-phase ("I") signal 2502 is referred to as being a sine wave,
then the quadrature-phase ("Q") signal 2506 can be referred to as
being a cosine wave (i.e., the "Q" signal 2506 is 90.degree. out of
phase with the "I" signal 2502). However, they may also be
rectangular waves, triangular waves, pulses, or any other
continuous and periodic waveforms. As stated above, one skilled in
the relevant art(s) will recognize the physical limitations to and
mathematical obstacles against achieving exact or perfect waveforms
and it is not the intent of the present invention that a perfect
waveform be generated or needed. Again, as stated above, for ease
of discussion, the term "rectangular waveform" will be used to
refer to waveforms that are substantially rectangular, the term
"square wave" will refer to those waveforms that are substantially
square, the term "triangular wave" will refer to those waveforms
that are substantially triangular, and the term "pulse" will refer
to those waveforms that are substantially a pulse, and it is not
the intent of the present invention that a perfect square wave,
triangle wave, or pulse be generated or needed. Regardless of the
shapes of the waveforms, the "Q" signal 2506 is out of phase with
the "I" signal 2506 by one-quarter period of the waveform. The
frequency of the "I" and "Q" signals 2502 and 2506 are
substantially equal.
[0409] The discussion contained herein will be confined to the more
prevalent embodiment wherein there are two intermediate signals
separated by 90.degree.. This is not limiting on the invention. It
will be apparent to those skilled in the relevant art(s) that the
techniques tough herein and applied to the "I/Q" embodiment of the
present invention also apply to more exotic embodiments wherein the
intermediate signals are shifted by some amount other than
90.degree., and also wherein there may be more than two
intermediate frequencies.
[0410] 3.3.3.2 Structural Description.
[0411] The design and use of a phase shifter 2504 is well known to
those skilled in the relevant art(s). A phase shifter 2504 may be
designed and fabricated from discrete components or it may be
purchased "off the shelf." A phase shifter accepts an "in-phase"
("I") oscillating signal 2502 from any of a number of sources, such
as a VCO 2304 or a local oscillator 2402, and outputs a
"quadrature-phase" ("Q") oscillating signal 2506 that is
substantially the same frequency and substantially the same shape
as the incoming "I" signal 2502, but with the phase shifted by
90.degree.. Both the "I" and "Q" signals 2502 and 2506 are
generally sinusoidal waves, but they may also be rectangular waves,
triangular waves, pulses, or any other continuous and periodic
waveforms. Regardless of the shapes of the waveforms, the "Q"
signal 2506 is out of phase with the "I" signal 2502 by one-quarter
period of the waveform. Both the "I" and "Q" signals 2502 and 2506
may be modulated.
[0412] The output of a phase shifter 2504 may be used as an input
to a phase modulator 2606.
3.3.4 the Phase Modulator (PM and "I/Q" Modes)
[0413] As discussed above, the phase modulation (PM) mode
embodiment including the in-phase/quadrature-phase modulation
("I/Q") mode embodiment of the invention uses a phase modulator.
See, as an example, phase modulator 1404 of FIG. 14 and phase
modulators 1804 and 1816 of FIG. 18. The invention supports
numerous embodiments of the phase modulator. Exemplary embodiments
of the phase modulator 2606 (FIG. 26) are described below. However,
it should be understood that these examples are provided for
illustrative purposes only. The invention is not limited to these
embodiments.
[0414] 3.3.4.1 Operational Description.
[0415] An information signal 2602 and an oscillating signal 2604
are accepted, and a phase modulated oscillating signal 2608 whose
phase varies as a function of the information signal 2602 is
output. The information signal 2602 may be analog or digital and
may be conditioned to ensure it is within the desired range. The
oscillating signal 2604 can be a sinusoidal wave, a rectangular
wave, a triangular wave, a pulse, or any other continuous and
periodic waveform. As stated above, one skilled in the relevant
art(s) will recognize the physical limitations to and mathematical
obstacles against achieving exact or perfect waveforms and it is
not the intent of the present invention that a perfect waveform be
generated or needed. Again, as stated above, for ease of
discussion, the term "rectangular waveform" will be used to refer
to waveforms that are substantially rectangular, the term "square
wave" will refer to those waveforms that are substantially square,
the term "triangular wave" will refer to those waveforms that are
substantially triangular, and the term "pulse" will refer to those
waveforms that are substantially a pulse, and it is not the intent
of the present invention that a perfect square wave, triangle wave,
or pulse be generated or needed. The modulated oscillating signal
2608 is also referred to as the modulated intermediate signal
2608.
[0416] In the case where the information signal 2602 is digital,
the modulated intermediate signal 2608 will shift phase between
discrete values, the first phase (e.g., for a signal represented by
sin (.omega.t+.theta..sub.o)) corresponding to a digital "high,"
and the second phase (e.g., for a signal represented by sin
(.omega.t+.theta..sub.o+.delta.), where .delta. represents the
amount the phase has been shifted) corresponding to a digital
"low." Either phase may correspond to the "high" or the "low,"
depending on the convention being used. This operation is referred
to as phase shift keying (PSK) which is a subset of PM.
[0417] If the information signal 2602 is analog, the phase of the
modulated intermediate signal 2608 will vary as a function of the
information signal 2602 and is not limited to the subset of PSK
described above.
[0418] The modulated intermediate signal 2608 is a phase modulated
signal which can be a sinusoidal wave, a rectangular wave, a
triangular wave, a pulse, or any other continuous and periodic
waveform, and which has substantially the same period as the
oscillating signal 2604.
[0419] 3.3.4.2 Structural Description.
[0420] The design and use of a phase modulator 2606 is well known
to those skilled in the relevant art(s). A phase modulator 2606 may
be designed and fabricated from discrete components, or it may be
purchased "off the shelf." A phase modulator 2606 accepts an
information signal 2602 from a source and an oscillating signal
2604 from a local oscillator 2402 or a phase shifter 2504. The
information signal 2602 is at baseband and is generally an
electrical signal within a prescribed voltage range. If the
information is digital, the voltage will be at discrete levels. If
the information is analog, the voltage will be continuously
variable between an upper and a lower level as a function of the
information signal 2602. The phase modulator 2606 uses the voltage
of the information signal 2602 to modulate the oscillating signal
2604 and causes a modulated intermediate signal 2608 to be output.
The information signal 2602, because it is a baseband signal and is
used to modulate the oscillating signal, may be referred to as the
modulating baseband signal 2604.
[0421] The modulated intermediate signal 2608 is an oscillating
signal whose phase varies as a function of the voltage of the
modulating baseband signal 2602. If the modulating baseband signal
2602 represents digital information, the phase of the modulated
intermediate signal 2608 will shift by a discrete amount (e.g., the
modulated intermediate signal 2608 will shift by an amount .delta.
between sin (.omega.t+.theta..sub.o) and sin
(.omega.t+.theta..sub.o+.pi.)). If, on the other hand, the
modulating baseband signal 2602 represents analog information, the
phase of the modulated intermediate signal 2608 will continuously
shift between its higher and lower phase limits as a function of
the information signal 2602. In one exemplary embodiment, the upper
and lower limits of the modulated intermediate signal 2608 can be
represented as sin(.omega.t+.theta..sub.o) and
sin(.omega.t+.theta..sub.o+.pi.). In other embodiments, the range
of the phase shift may be less than .pi.. The modulated
intermediate signal 2608 can be a sinusoidal wave, a rectangular
wave, a triangular wave, a pulse, or any other continuous and
periodic waveform.
[0422] The phase modulated intermediate signal 2608 may then be
used to drive a switch module 2802.
3.3.5 The Summing Module (AM Mode)
[0423] As discussed above, the amplitude modulation (AM) mode
embodiment of the invention uses a summing module. See, as an
example, summing module 1606 in FIG. 16. The invention supports
numerous embodiments of the summing module. Exemplary embodiments
of the summing module 2706 (FIG. 27) are described below. However,
it should be understood that these examples are provided for
illustrative purposes only. The invention is not limited to these
embodiments. It may also be used in the "I/Q" mode embodiment when
the modulation is AM. The summing module 2706 need not be used in
all AM embodiments.
[0424] 3.3.5.1 Operational Description.
[0425] An information signal 2702 and a bias signal 2702 are
accepted, and a reference signal is output. The information signal
2702 may be analog or digital and may be conditioned to ensure it
is within the proper range so as not to damage any of the circuit
components. The bias signal 2704 is usually a direct current (DC)
signal.
[0426] In the case where the information signal 2702 is digital,
the reference signal 2706 shifts between discrete values, the first
value corresponding to a digital "high," and the second value
corresponding to a digital "low." Either value may correspond to
the "high" or the "low," depending on the convention being used.
This operation is referred to as amplitude shift keying (ASK) which
is a subset of AM.
[0427] If the information signal 2702 is analog, the value of the
reference signal 2708 will vary linearly between upper and lower
extremes which correspond to the upper and lower limits of the
information signal 2702. Again, either extreme of the reference
signal 2708 range may correspond to the upper or lower limit of the
information signal 2702 depending on the convention being used.
[0428] The reference signal 2708 is a digital or analog signal and
is substantially proportional to the information signal 2702.
[0429] 3.3.5.2 Structural Description.
[0430] The design and use of a summing module 2706 is well known to
those skilled in the relevant art(s). A summing module 2706 may be
designed and fabricated from discrete components, or it may be
purchased "off the shelf." A summing module 2706 accepts an
information signal 2702 from a source. The information signal 2702
is at baseband and generally is an electrical signal within a
prescribed voltage range. If the information is digital, the
information signal 2702 is at either of two discrete levels. If the
information is analog, the information signal 2702 is continuously
variable between an upper and a lower level. The summing module
2706 uses the voltage of the information signal 2702 and combines
it with a bias signal 2704. The output of the summing module 2706
is called the reference signal 2708. The purpose of the summing
module 2706 is to cause the reference signal 2708 to be within a
desired signal range. One skilled in the relevant art(s) will
recognize that the information signal 2702 may be used directly,
without being summed with a bias signal 2704, if it is already
within the desired range. The information signal 2702 is a baseband
signal, but typically, in an AM embodiment, it is not used to
directly modulate an oscillating signal. The amplitude of the
reference signal 2708 is at discrete levels if the information
signal 2702 represents digital information. On the other hand, the
amplitude of the reference signal 2708 is continuously variable
between its higher and lower limits if the information signal 2702
represents analog information. The amplitude of the reference
signal 2708 is substantially proportional to the information signal
2702, however, a positive reference signal 2708 need not represent
a positive information signal 2702.
[0431] The reference signal 2708 is routed to the first input 3108
of a switch module 3102. In one exemplary embodiment, a resistor
2824 is connected between the output of the summing module 2706 (or
the source of the information signal 2702 in the embodiment wherein
the summing amplifier 2706 is not used) and the switch 3116 of the
switch module 3102.
3.3.6 the Switch Module (FM, PM, and "I/Q" Modes)
[0432] As discussed above, the frequency modulation (FM), phase
modulation (PM), and the in-phase/quadrature-phase modulation
("I/Q") mode embodiments of the invention use a switching assembly
referred to as switch module 2802 (FIGS. 28A-28C). As an example,
switch module 2802 is a component in switch module 1214 in FIG. 12,
switch module 1410 in FIG. 14, and switch modules 1822 and 1828 in
FIG. 18. The invention supports numerous embodiments of the switch
module. Exemplary embodiments of the switch module 2802 are
described below. However, it should be understood that these
examples are provided for illustrative purposes only. The invention
is not limited to these embodiments. The switch module 2802 and its
operation in the FM, PM, and "I/Q" mode embodiments is
substantially the same as its operation in the AM mode embodiment,
described in sections 3.3.7-3.3.7.2 below.
[0433] 3.3.6.1 Operational Description.
[0434] A bias signal 2806 is gated as a result of the application
of a modulated oscillating signal 2804, and a signal with a
harmonically rich waveform 2814 is created. The bias signal 2806 is
generally a fixed voltage. The modulated oscillating signal 2804
can be frequency modulated, phase modulated, or any other
modulation scheme or combination thereof. In certain embodiments,
such as in certain amplitude shift keying modes, the modulated
oscillating signal 2804 may also be amplitude modulated. The
modulated oscillating signal 2804 can be a sinusoidal wave, a
rectangular wave, a triangular wave, a pulse, or any other
continuous and periodic waveform. In a preferred embodiment,
modulated oscillating signal 2804 would be a rectangular wave. As
stated above, one skilled in the relevant art(s) will recognize the
physical limitations to and mathematical obstacles against
achieving exact or perfect waveforms and it is not the intent of
the present invention that a perfect waveform be generated or
needed. Again, as stated above, for ease of discussion, the term
"rectangular waveform" will be used to refer to waveforms that are
substantially rectangular, the term "square wave" will refer to
those waveforms that are substantially square, the term "triangular
wave" will refer to those waveforms that are substantially
triangular, and the term "pulse" will refer to those waveforms that
are substantially a pulse, and it is not the intent of the present
invention that a perfect square wave, triangle wave, or pulse be
generated or needed.
[0435] The signal with harmonically rich waveform 2814, hereafter
referred to as the harmonically rich signal 2814, is a continuous
and periodic waveform that is modulated substantially the same as
the modulated oscillating signal 2804. That is, if the modulated
oscillating signal 2804 is frequency modulated, the harmonically
rich signal 2814 will also be frequency modulated, and if the
modulated oscillating signal 2804 is phase modulated, the
harmonically rich signal 2814 will also be phase modulated. (In one
embodiment, the harmonically rich signal 2814 is a substantially
rectangular waveform.) As stated before, a continuous and periodic
waveform, such as a rectangular wave, has sinusoidal components
(harmonics) at frequencies that are integer multiples of the
fundamental frequency of the underlying waveform (the Fourier
component frequencies). Thus, the harmonically rich signal 2814 is
composed of sinusoidal signals at frequencies that are integer
multiples of the fundamental frequency of itself.
[0436] 3.3.6.2 Structural Description.
[0437] The switch module 2802 of an embodiment of the present
invention is comprised of a first input 2808, a second input 2810,
a control input 2820, an output 2822, and a switch 2816. A bias
signal 2806 is applied to the first input 2808 of the switch module
2802. Generally, the bias signal 2806 is a fixed voltage, and in
one embodiment of the invention, a resistor 2824 is located between
the bias signal 2806 and the switch 2816. The second input 2810 of
the switch module 2802 is generally at electrical ground 2812.
However, one skilled in the relevant art(s) will recognize that
alternative embodiments exist wherein the second input 2810 may not
be at electrical ground 2812, but rather a second signal 2818,
provided that the second signal 2818 is different than the bias
signal 2806.
[0438] A modulated oscillating signal 2804 is connected to the
control input 2820 of the switch module 2802. The modulated
oscillating signal 2804 may be frequency modulated or phase
modulated. (In some circumstances and embodiments, it may be
amplitude modulated, such as in on/off keying, but this is not the
general case, and will not be described herein.) The modulated
oscillating signal 2804 can be a sinusoidal wave, a rectangular
wave, a triangular wave, a pulse, or any other continuous and
periodic waveform. In a preferred embodiment, it would be a
rectangular wave. The modulated oscillating signal 2804 causes the
switch 2816 to close and open.
[0439] The harmonically rich signal 2814 described in section
3.3.6.1 above, is found at the output 2822 of the switch module
2802. The harmonically rich signal 2814 is a continuous and
periodic waveform that is modulated substantially the same as the
modulated oscillating signal 2804. That is, if the modulated
oscillating signal 2804 is frequency modulated, the harmonically
rich signal 2814 will also be frequency modulated, and if the
modulated oscillating signal 2804 is phase modulated, the
harmonically rich signal 2814 will also be phase modulated. In one
embodiment, the harmonically rich signal 2814 has a substantially
rectangular waveform. As stated before, a continuous and periodic
waveform, such as a rectangular wave, has sinusoidal components
(harmonics) at frequencies that are integer multiples of the
fundamental frequency of the underlying waveform (the Fourier
component frequencies). Thus, the harmonically rich signal 2814 is
composed of sinusoidal signals at frequencies that are integer
multiples of the fundamental frequency of itself. Each of these
sinusoidal signals is also modulated substantially the same as the
continuous and periodic waveform (i.e., the modulated oscillating
signal 2804) from which it is derived.
[0440] The switch module 2802 operates as follows. When the switch
2816 is "open," the output 2822 of switch module 2802 is at
substantially the same voltage level as bias signal 2806. Thus,
since the harmonically rich signal 2814 is connected directly to
the output 2822 of switch module 2802, the amplitude of
harmonically rich signal 2814 is equal to the amplitude of the bias
signal 2806. When the modulated oscillating signal 2804 causes the
switch 2816 to become "closed," the output 2822 of switch module
2802 becomes connected electrically to the second input 2810 of
switch module 2802 (e.g., ground 2812 in one embodiment of the
invention), and the amplitude of the harmonically rich signal 2814
becomes equal to the potential present at the second input 2810
(e.g., zero volts for the embodiment wherein the second input 2810
is connected to electrical ground 2812). When the modulated
oscillating signal 2804 causes the switch 2816 to again become
"open," the amplitude of the harmonically rich signal 2814 again
becomes equal to the bias signal 2806. Thus, the amplitude of the
harmonically rich signal 2814 is at either of two signal levels,
i.e., bias signal 2806 or ground 2812, and has a frequency that is
substantially equal to the frequency of the modulated oscillating
signal 2804 that causes the switch 2816 to open and close. The
harmonically rich signal 2814 is modulated substantially the same
as the modulated oscillating signal 2804. One skilled in the
relevant art(s) will recognize that any one of a number of switch
designs will fulfill the scope and spirit of the present invention
as described herein.
[0441] In an embodiment of the invention, the switch 2816 is a
semiconductor device, such as a diode ring. In another embodiment,
the switch is a transistor, such as a field effect transistor
(FET). In an embodiment wherein the FET is gallium arsenide (GaAs),
switch module 2802 can be designed as seen in FIGS. 29A-29C, where
the modulated oscillating signal 2804 is connected to the gate 2902
of the GaAsFET 2901, the bias signal 2806 is connected through a
bias resistor 2824 to the source 2904 of the GaAsFET 2901, and
electrical ground 2812 is connected to the drain 2906 of GaAsFET
2901. (In an alternate embodiment shown in FIG. 29C, a second
signal 2818 may be connected to the drain 2906 of GaAsFET 2901.)
Since the drain and the source of GaAsFETs are interchangeable, the
bias signal 2806 can be applied to either the source 2904 or to the
drain 2906. If there is concern that there might be some
source-drain asymmetry in the GaAsFET, the switch module can be
designed as shown in FIGS. 30A-30C, wherein two GaAsFETs 3002 and
3004 are connected together, with the source 3010 of the first 3002
connected to the drain 3012 of the second 3004, and the drain 3006
of the first 3002 being connected to the source 3008 of the second
3004. This design arrangement will balance substantially all
asymmetries.
[0442] An alternate implementation of the design includes a "dwell
capacitor" wherein one side of a capacitor is connected to the
first input of the switch and the other side of the capacitor is
connected to the second input of the switch. The purpose of the
design is to increase the apparent aperture of the pulse without
actually increasing its width. For additional detail on the design
and use of a dwell capacitor, see co-pending application entitled
"Method and System for Down-Converting Electromagnetic Signals
Having Optimized Switch Structures," Ser. No. 09/293,095, filed
Apr. 16, 1999, and other applications as referenced above.
[0443] Other switch designs and implementations will be apparent to
persons skilled in the relevant art(s).
[0444] The output 2822 of the switch module 2802, i.e., the
harmonically rich signal 2814, can be routed to a filter 3504 in
the FM and PM modes or to a Summer 3402 in the "I/Q" mode.
3.3.7 the Switch Module (AM Mode)
[0445] As discussed above, the amplitude modulation (AM) mode
embodiment of the invention uses a switching assembly referred to
as switch module 3102 (FIGS. 31A-31C). As an example, switch module
3102 is a component in switch module 1614 of FIG. 16. The invention
supports numerous embodiments of the switch module. Exemplary
embodiments of the switch module 3102 are described below. However,
it should be understood that these examples are provided for
illustrative purposes only. The invention is not limited to these
embodiments. The switch module 3102 and its operation in the AM
mode embodiment is substantially the same as its operation in the
FM, PM, and "I/Q" mode embodiments described in sections
3.3.6-3.3.6.2 above.
[0446] 3.3.7.1 Operational Description.
[0447] A reference signal 3106 is gated as a result of the
application of an oscillating signal 3104, and a signal with a
harmonically rich waveform 3114 is created. The reference signal
3106 is a function of the information signal 2702 and may, for
example, be either the summation of the information signal 2702
with a bias signal 2704 or it may be the information signal 2702 by
itself. In the AM mode, the oscillating signal 3104 is generally
not modulated, but can be.
[0448] The oscillating signal 3104 can be a sinusoidal wave, a
rectangular wave, a triangular wave, a pulse, or any other
continuous and periodic waveform. In a preferred embodiment, it
would be a rectangular wave. As stated above, one skilled in the
relevant art(s) will recognize the physical limitations to and
mathematical obstacles against achieving exact or perfect waveforms
and it is not the intent of the present invention that a perfect
waveform be generated or needed. Again, as stated above, for ease
of discussion, the term "rectangular waveform" will be used to
refer to waveforms that are substantially rectangular, the term
"square wave" will refer to those waveforms that are substantially
square, the term "triangular wave" will refer to those waveforms
that are substantially triangular, and the term "pulse" will refer
to those waveforms that are substantially a pulse, and it is not
the intent of the present invention that a perfect square wave,
triangle wave, or pulse be generated or needed.
[0449] The signal with a harmonically rich waveform 3114, hereafter
referred to as the harmonically rich signal 3114, is a continuous
and periodic waveform whose amplitude is a function of the
reference signal. That is, it is an AM signal. In one embodiment,
the harmonically rich signal 3114 has a substantially rectangular
waveform. As stated before, a continuous and periodic waveform,
such as a rectangular wave, will have sinusoidal components
(harmonics) at frequencies that are integer multiples of the
fundamental frequency of the underlying waveform (the Fourier
component frequencies). Thus, harmonically rich signal 3114 is
composed of sinusoidal signals at frequencies that are integer
multiples of the fundamental frequency of itself.
[0450] Those skilled in the relevant art(s) will recognize that
alternative embodiments exist wherein combinations of modulations
(e.g., PM and ASK, FM and AM, etc.) may be employed simultaneously.
In these alternate embodiments, the oscillating signal 3104 may be
modulated. These alternate embodiments will be apparent to persons
skilled in the relevant art(s), and thus will not be described
herein.
[0451] 3.3.7.2 Structural Description.
[0452] The switch module 3102 of the present invention is comprised
of a first input 3108, a second input 3110, a control input 3120,
an output 3122, and a switch 3116. A reference signal 3106 is
applied to the first input 3108 of the switch module 3102.
Generally, the reference signal 3106 is a function of the
information signal 2702, and may either be the summation of the
information signal 2702 with a bias signal or it may be the
information signal 2702 by itself. In one embodiment of the
invention, a resistor 3124 is located between the reference signal
3106 and the switch 3116. The second input 3110 of the switch
module 3102 is generally at electrical ground 3112, however, one
skilled in the relevant art(s) will recognize that alternative
embodiments exist wherein the second input 3110 may not be at
electrical ground 3112, but rather connected to a second signal
3118. In an alternate embodiment, the inverted value of the
reference signal 3106 is connected to the second input 3110 of the
switch module 3102.
[0453] An oscillating signal 3104 is connected to the control input
3120 of the switch module 3102. Generally, in the AM mode, the
oscillating signal 3104 is not modulated, but a person skilled in
the relevant art(s) will recognize that there are embodiments
wherein the oscillating signal 3104 may be frequency modulated or
phase modulated, but these will not be described herein. The
oscillating signal 3104 can be a sinusoidal wave, a rectangular
wave, a triangular wave, a pulse, or any other continuous and
periodic waveform. In a preferred embodiment, it would be a
rectangular wave. The oscillating signal 3104 causes the switch
3116 to close and open.
[0454] The harmonically rich signal 3114 described in section
3.3.7.1 above is found at the output 3122 of the switch module
3102. The harmonically rich signal 3114 is a continuous and
periodic waveform whose amplitude is a function of the amplitude of
the reference signal. In one embodiment, the harmonically rich
signal 3114 has a substantially rectangular waveform. As stated
before, a continuous and periodic waveform, such as a rectangular
wave, has sinusoidal components (harmonics) at frequencies that are
integer multiples of the fundamental frequency of the underlying
waveform (the Fourier component frequencies). Thus, harmonically
rich signal 3114 is composed of sinusoidal signals at frequencies
that are integer multiples of the fundamental frequency of itself.
As previously described, the relative amplitude of the harmonics of
a continuous periodic waveform is generally a function of the ratio
of the pulse width of the rectangular wave and the period of the
fundamental frequency, and can be determined by doing a Fourier
analysis of the periodic waveform. When the amplitude of the
periodic waveform varies, as in the AM mode of the invention, the
change in amplitude of the periodic waveform has a proportional
effect on the absolute amplitude of the harmonics. In other words,
the AM is embedded on top of each of the harmonics.
[0455] The description of the switch module 3102 is substantially
as follows: When the switch 3116 is "open," the amplitude of the
harmonically rich signal 3114 is substantially equal to the
reference signal 3106. When the oscillating signal 3104 causes the
switch 3116 to become "closed," the output 3122 of the switch
module 3102 becomes connected electrically to the second input 3110
of the switch module 3102 (e.g., ground 3112 in one embodiment),
and the amplitude of the harmonically rich signal 3114 becomes
equal to the value of the second input 3110 (e.g., zero volts for
the embodiment wherein the second input 3110 is connected to
electrical ground 3112). When the oscillating signal 3104 causes
the switch 3116 to again become "open," the amplitude of the
harmonically rich signal 3114 again becomes substantially equal to
the reference signal 3106. Thus, the amplitude of the harmonically
rich signal 3114 is at either of two signal levels, i.e., reference
signal 3106 or ground 3112, and has a frequency that is
substantially equal to the frequency of the oscillating signal 3104
that causes the switch 3116 to open and close. In an alternate
embodiment wherein the second input 3110 is connected to the second
signal 3118, the harmonically rich signal 3114 varies between the
reference signal 3106 and the second signal 3118. One skilled in
the relevant art(s) will recognize that any one of a number of
switch module designs will fulfill the scope and spirit of the
present invention.
[0456] In an embodiment of the invention, the switch 3116 is a
semiconductor device, such as a diode ring. In another embodiment,
the switch is a transistor, such as, but not limited to, a field
effect transistor (FET). In an embodiment wherein the FET is
gallium arsenide (GaAs), the module can be designed as seen in
FIGS. 32A-32C, where the oscillating signal 3104 is connected to
the gate 3202 of the GaAsFET 3201, the reference signal 3106 is
connected to the source 3204, and electrical ground 3112 is
connected to the drain 3206 (in the embodiment where ground 3112 is
selected as the value of the second input 3110 of the switch module
3102). Since the drain and the source of GaAsFETs are
interchangeable, the reference signal 3106 can be applied to either
the source 3204 or to the drain 3206. If there is concern that
there might be some source-drain asymmetry in the GaAsFET 3201, the
switch 3116 can be designed as shown in FIGS. 33A-33C, wherein two
GaAsFETs 3302 and 3304 are connected together, with the source 3310
of the first 3302 connected to the drain 3312 of the second 3304,
and the drain 3306 of the first 3302 being connected to the source
3308 of the second 3304. This design arrangement will substantially
balance all asymmetries.
[0457] An alternate implementation of the design includes a "dwell
capacitor" wherein one side of a capacitor is connected to the
first input of the switch and the other side of the capacitor is
connected to the second input of the switch. The purpose of the
design is to increase the apparent aperture of the pulse without
actually increasing its width. For additional detail on the design
and use of a dwell capacitor, see co-pending application entitled
"Method and System for Down-Converting Electromagnetic Signals
Having Optimized Switch Structures," Ser. No. 09/293,095, filed
Apr. 16, 1999, and other applications as referenced above.
[0458] Other switch designs and implementations will be apparent to
persons skilled in the relevant art(s).
[0459] The output 3122 of the switch module 3102, i.e., the
harmonically rich signal 3114, can be routed to a filter 3504 in
the AM mode.
3.3.8 the Summer ("I/Q" Mode)
[0460] As discussed above, the in-phase/quadrature-phase modulation
("I/Q") mode embodiment of the invention uses a summer. See, as an
example, summer 1832 in FIG. 18. The invention supports numerous
embodiments of the summer. Exemplary embodiments of the summer 3402
(FIG. 34) are described below. However, it should be understood
that these examples are provided for illustrative purposes only.
The invention is not limited to these embodiments.
[0461] 3.3.8.1 Operational Description.
[0462] An "I" modulated signal 3404 and a "Q" modulated signal 3406
are combined and an "I/Q" modulated signal 3408 is generated.
Generally, both "I" and "Q" modulated signals 3404 and 3406 are
harmonically rich waveforms, which are referred to as the
harmonically rich "I" signal 3404 and the harmonically rich "Q"
signal 3406. Similarly, "I/Q" modulated signal 3408 is harmonically
rich and is referred to as the harmonically rich "I/Q" signal. In
one embodiment, these harmonically rich signals have substantially
rectangular waveforms. As stated above, one skilled in the relevant
art(s) will recognize the physical limitations to and mathematical
obstacles against achieving exact or perfect waveforms and it is
not the intent of the present invention that a perfect waveform be
generated or needed.
[0463] In a typical embodiment, the harmonically rich "I" signal
3404 and the harmonically rich "Q" signal 3406 are phase modulated,
as is the harmonically rich "I/Q" signal 3408. A person skilled in
the relevant art(s) will recognize that other modulation
techniques, such as amplitude modulating the "I/Q" signal, may also
be used in the "I/Q" mode without deviating from the scope and
spirit of the invention.
[0464] As stated before, a continuous and periodic waveform, such
as harmonically rich "I/Q" signal 3408, has sinusoidal components
(harmonics) at frequencies that are integer multiples of the
fundamental frequency of the underlying waveform (the Fourier
component frequencies). Thus, harmonically rich "I/Q" signal 3408
is composed of sinusoidal signals at frequencies that are integer
multiples of the fundamental frequency of itself. These sinusoidal
signals are also modulated substantially the same as the continuous
and periodic waveform from which they are derived. That is, in this
embodiment, the sinusoidal signals are phase modulated, and include
the information from both the "I" modulated signal and the "Q"
modulated signal.
[0465] 3.3.8.2 Structural Description.
[0466] The design and use of a summer 3402 is well known to those
skilled in the relevant art(s). A summer 3402 may be designed and
fabricated from discrete components, or it may be purchased "off
the shelf." A summer 3402 accepts a harmonically rich "I" signal
3404 and a harmonically rich "Q" signal 3406, and combines them to
create a harmonically rich "I/Q" signal 3408. In a preferred
embodiment of the invention, the harmonically rich "I" signal 3404
and the harmonically rich "Q" signal 3406 are both phase modulated.
When the harmonically rich "I/Q" signal 3404 and the harmonically
rich "Q" signal 3406 are both phase modulated, the harmonically
rich "I/Q" signal 3408 is also phase modulated.
[0467] As stated before, a continuous and periodic waveform, such
as the harmonically rich "I/Q" signal 3408, has sinusoidal
components (harmonics) at frequencies that are integer multiples of
the fundamental frequency of the underlying waveform (the Fourier
component frequencies). Thus, the harmonically rich "I/Q" signal
3408 is composed of "I/Q" sinusoidal signals at frequencies that
are integer multiples of the fundamental frequency of itself. These
"I/Q" sinusoidal signals are also phase modulated substantially the
same as the continuous and periodic waveform from which they are
derived (i.e., the harmonically rich "I/Q" signal 3408).
[0468] The output of the summer 3402 is then routed to a filter
3504.
3.3.9 the Filter (FM, PM, AM, and "I/Q" Modes)
[0469] As discussed above, all modulation mode embodiments of the
invention use a filter. See, as an example, filter 1218 in FIG. 12,
filter 1414 in FIG. 14, filter 1618 in FIG. 16, and filter 1836 in
FIG. 18. The invention supports numerous embodiments of the filter.
Exemplary embodiments of the filter 3504 (FIG. 35) are described
below. However, it should be understood that these examples are
provided for illustrative purposes only. The invention is not
limited to these embodiments.
[0470] 3.3.9.1 Operational Description.
[0471] A modulated signal with a harmonically rich waveform 3502 is
accepted. It is referred to as the harmonically rich signal 3502.
As stated above, a continuous and periodic waveform, such as the
harmonically rich signal 3502, is comprised of sinusoidal
components (harmonics) at frequencies that are integer multiples of
the fundamental frequency of the underlying waveform from which
they are derived. These are called the Fourier component
frequencies. In one embodiment of the invention, the undesired
harmonic frequencies are removed, and the desired frequency 3506 is
output. In an alternate embodiment, a plurality of harmonic
frequencies are output.
[0472] The harmonic components of the harmonically rich signal 3502
are modulated in the same manner as the harmonically rich signal
3502 itself. That is, if the harmonically rich signal 3502 is
frequency modulated, all of the harmonic components of that signal
are also frequency modulated. The same is true for phase
modulation, amplitude modulation, and "I/Q" modulation.
[0473] 3.3.9.2 Structural Description.
[0474] The design and use of a filter 3504 is well known to those
skilled in the relevant art(s). A filter 3504 may be designed and
fabricated from discrete components or it may be purchased "off the
shelf." The filter 3504 accepts the harmonically rich signal 3502
from the switch module 2802 or 3102 in the FM, PM, and AM modes,
and from the summer 3402 in the "I/Q" mode. The harmonically rich
signal 3502 is a continuous and periodic waveform. As such, it is
comprised of sinusoidal components (harmonics) that are at
frequencies that are integer multiples of the fundamental frequency
of the underlying harmonically rich signal 3502. The filter 3504
removes those sinusoidal signals having undesired frequencies. The
signal 3506 that remains is at the desired frequency, and is called
the desired output signal 3506.
[0475] To achieve this result, according to an embodiment of the
invention, a filter 3504 is required to filter out the unwanted
harmonics of the harmonically rich signal 3502.
[0476] The term "Q" is used to represent the ratio of the center
frequency of the desired output signal 3506 to the half power band
width. Looking at FIG. 36 we see a desired frequency 3602 of 900
MHz. The filter 3504 is used to ensure that only the energy at that
frequency 3602 is transmitted. Thus, the bandwidth 3604 at half
power (the so-called "3 dB down" point) should be as narrow as
possible. The ratio of frequency 3602 to bandwidth 3604 is defined
as "Q." As shown on FIG. 36, if the "3 dB down" point is at plus or
minus 15 MHz, the value of Q will be 900/(15+15) or 30. With the
proper selection of elements for any particular frequency, Qs on
the order of 20 or 30 are achievable.
[0477] For crisp broadcast frequencies, it is desired that Q be as
high as possible and practical, based on the given application and
environment. The purpose of the filter 3504 is to filter out the
unwanted harmonics of the harmonically rich signal. The circuits
are tuned to eliminate all other harmonics except for the desired
frequency 3506 (e.g., the 900 MHz harmonic 3602). Turning now to
FIGS. 37A and 37B, we see examples of filter circuits. One skilled
in the relevant art(s) will recognize that a number of filter
designs will accomplish the desired goal of passing the desired
frequency while filtering the undesired frequencies.
[0478] FIG. 37A illustrates a circuit having a capacitor in
parallel with an inductor and shunted to ground. In FIG. 37B, a
capacitor is in series with an inductor, and a parallel circuit
similar to that in FIG. 37A is connected between the capacitor and
inductor and shunted to ground.
[0479] The modulated signal at the desired frequency 3506 may then
be routed to the transmission module 3804.
3.3.10 the Transmission Module (FM, PM, AM, and "I/Q" Modes)
[0480] As discussed above, the modulation mode embodiments of the
invention preferably use a transmission module. See, as an example,
transmission module 1222 in FIG. 12, transmission module 1418 in
FIG. 14, transmission module 1622 in FIG. 16, and transmission
module 1840 in FIG. 18. The transmission module is optional, and
other embodiments may not include a transmission module. The
invention supports numerous embodiments of the transmission module.
Exemplary embodiments of the transmission module 3804 (FIG. 38) are
described below. However, it should be understood that these
examples are provided for illustrative purposes only. The invention
is not limited to these embodiments.
[0481] 3.3.10.1 Operational Description.
[0482] A modulated signal at the desired frequency 3802 is accepted
and is transmitted over the desired medium, such as, but not
limited to, over-the-air broadcast or point-to-point cable.
[0483] 3.3.10.2 Structural Description.
[0484] The transmission module 3804 receives the signal at the
desired EM frequency 3802. If it is intended to be broadcast over
the air, the signal may be routed through an optional antenna
interface and then to the antenna for broadcast. If it is intended
for the signal to be transmitted over a cable from one point to
another, the signal may be routed to an optional line driver and
out through the cable. One skilled in the relevant art(s) will
recognize that other transmission media may be used.
3.3.11 Other Implementations
[0485] The implementations described above are provided for
purposes of illustration. These implementations are not intended to
limit the invention. Other implementation embodiments are possible
and covered by the invention, such as but not limited to software,
software/hardware, and firmware implementations of the systems and
components of the invention. Alternate implementations and
embodiments, differing slightly or substantially from those
described herein, will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. Such
alternate implementations fall within the scope and spirit of the
present invention.
4. HARMONIC ENHANCEMENT
4.1 High Level Description
[0486] This section (including its subsections) provides a
high-level description of harmonic enhancement according to the
present invention. In particular, pulse shaping is described at a
high-level. Also, a structural implementation for achieving this
process is described at a high-level. This structural
implementation is described herein for illustrative purposes, and
is not limiting. In particular, the process described in this
section can be achieved using any number of structural
implementations, one of which is described in this section. The
details of such structural implementations will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein.
[0487] It is noted that some embodiments of the invention include
harmonic enhancement, whereas other embodiments do not.
4.1.1 Operational Description
[0488] To better understand the generation and extraction of
harmonics, and the purpose behind shaping the waveforms to enhance
the harmonics, the following discussion of Fourier analysis as it
applies to the present invention is offered.
[0489] A discovery made by Baron Jean B. J. Fourier (1768-1830)
showed that continuous and periodic waveforms are comprised of a
plurality of sinusoidal components, called harmonics. More
importantly, the frequency of these components are integer
multiples of the frequency of the original waveform (called the
fundamental frequency). The amplitude of each of these component
waveforms depends on the shape of the original waveform. The
derivations and proofs of Baron Fourier's analysis are well known
to those skilled in the relevant art(s).
[0490] The most basic waveform which is continuous and periodic is
a sine wave. It has but one harmonic, which is at the fundamental
frequency. This is also called the first harmonic. Since it only
has one component, the amplitude of the harmonic component is equal
to the amplitude of the original waveform, i.e., the sine wave
itself. The sine wave is not considered to be "harmonically
rich."
[0491] An impulse train is the other extreme case of a periodic
waveform. Mathematically, it is considered to have zero width. The
mathematical analysis in this case shows that there are harmonics
at all multiples of the frequency of the impulse. That is, if the
impulse has a frequency of F.sub.i, then the harmonics are
sinusoidal waves at 1F.sub.i, 2F.sub.i, 3F.sub.i, 4F.sub.i, etc. As
the analysis also shows in this particular case, the amplitude of
all of the harmonics are equal. This is indeed, a "harmonically
rich" waveform, but is realistically impractical with current
technology.
[0492] A more typical waveform is a rectangular wave, which is a
series of pulses. Each pulse will have a width (called a pulse
width, or ".tau."), and the series of pulses in the waveform will
have a period ("T" which is the inverse of the frequency, i.e.,
T=1/F.sub.r, where "F.sub.r" is the fundamental frequency of the
rectangular wave). One form of rectangular wave is the square wave,
where the signal is at a first state (e.g., high) for the same
amount of time that it is at the second state (e.g., low). That is,
the ratio of the pulse width to period (.tau./T) is 0.5. Other
forms of rectangular waves, other than square waves, are typically
referred to simply as "pulses," and have .tau./T<0.5 (i.e., the
signal will be "high" for a shorter time than it is "low"). The
mathematical analysis shows that there are harmonics at all of the
multiples of the fundamental frequency of the signal. Thus, if the
frequency of the rectangular waveform is F.sub.r, then the
frequency of the first harmonic is 1F.sub.r, the frequency of the
second harmonic is 2F.sub.r, the frequency of the third harmonic is
3F.sub.r, and so on. There are some harmonics for which the
amplitude is zero. In the case of a square wave, for example, the
"null points" are the even harmonics. For other values of .tau./T,
the "null points" can be determined from the mathematical
equations. The general equation for the amplitude of the harmonics
in a rectangular wave having an amplitude of A.sub.pulse is as
follows:
Amplitude(n.sup.th harmonic)=A.sub.n={[A.sub.pulse][(2/.pi.)/n] sin
[n.pi.(.tau./T)]} Eq. 1
Table 6000 of FIG. 60 shows the amplitudes of the first fifty
harmonics for rectangular waves having six different .tau./T
ratios. The .tau./T ratios are 0.5 (a square wave), 0.25, 0.10,
0.05, 0.01, and 0.005. (One skilled in the relevant art(s) will
recognize that A.sub.pulse is set to unity for mathematical
comparison.) From this limited example, it can be seen that the
ratio of pulse width to period is a significant factor in
determining the relative amplitudes of the harmonics. Notice too,
that for the case where .tau./T=0.5 (i.e., a square wave), the
relationship stated above (i.e., only odd harmonics are present)
holds. Note that as VT becomes small (i.e., the pulse approaches an
impulse), the amplitudes of the harmonics becomes substantially
"flat." That is, there is very little decrease in the relative
amplitudes of the harmonics. One skilled in the relevant art(s)
will understand how to select the desired pulse width for any given
application based on the teachings contained herein. It can also be
shown mathematically and experimentally that if a signal with a
continuous and periodic waveform is modulated, that modulation is
also present on every harmonic of the original waveform.
[0493] From the foregoing, it can be seen how pulse width is an
important factor in assuring that the harmonic waveform at the
desired output frequency has sufficient amplitude to be useful
without requiring elaborate filtering or unnecessary
amplification.
[0494] Another factor in assuring that the desired harmonic has
sufficient amplitude is how the switch 2816 and 3116 (FIGS. 28A and
31A) in the switch module 2802 and 3102 responds to the control
signal that causes the switch to close and to open (i.e., the
modulated oscillating signal 2804 of FIG. 28 and the oscillating
signal 3104 of FIG. 31). In general, switches have two thresholds.
In the case of a switch that is normally open, the first threshold
is the voltage required to cause the switch to close. The second
threshold is the voltage level at which the switch will again open.
The convention used herein for ease of illustration and discussion
(and not meant to be limiting) is for the case where the switch is
closed when the control signal is high, and open when the control
signal is low. It would be apparent to one skilled in the relevant
art(s) that the inverse could also be used. Typically, these
voltages are not identical, but they may be. Another factor is how
rapidly the switch responds to the control input once the threshold
voltage has been applied. The objective is for the switch to close
and open such that the bias/reference signal is "crisply" gated.
That is, preferably, the impedance through the switch must change
from a high impedance (an open switch) to a low impedance (a closed
switch) and back again in a very short time so that the output
signal is substantially rectangular.
[0495] It is an objective of this invention in the transmitter
embodiment that the intelligence in the information signal is to be
transmitted. That is, the information is modulated onto the
transmitted signal. In the FM and PM modes, to achieve this
objective, the information signal is used to modulate the
oscillating signal 2804. The oscillating signal 2804 then causes
the switch 2816 to close and open. The information that is
modulated onto the oscillating signal 2804 must be faithfully
reproduced onto the signal that is output from the switch circuit
(i.e., the harmonically rich signal 2814). For this to occur
efficiently, in embodiments of the invention, the switch 2816
preferably closes and opens crisply so that the harmonically rich
signal 2814 changes rapidly from the bias/reference signal 2806 (or
3106) to ground 2812 (or the second signal level 2818 in the
alternate embodiment). This rapid rise and fall time is desired so
that the harmonically rich signal 2814 will be "harmonically rich."
(In the case of AM, the oscillating signal 3104 is not modulated,
but the requirement for "crispness" still applies.) For the switch
2816 to close and open crisply, the oscillating signal 2804 must
also be crisp. If the oscillating signal 2804 is sinusoidal, the
switch 2816 will open and close when the threshold voltages are
reached, but the pulse width of the harmonically rich signal 2814
may not be as small as is needed to ensure the amplitude of the
desired harmonic of the harmonically rich signal 2814 is
sufficiently high to allow transmission without elaborate filtering
or unnecessary amplification. Also, in the embodiment wherein the
switch 2816 is a GaAsFET 2901, if the oscillating signal 2804 that
is connected to the gate 2902 of the GaAsFET 2901 (i.e., the signal
that causes the switch 2816 to close and open) is a sinusoidal
wave, the GaAsFET 2901 will not crisply close and open, but will
act more like an amplifier than a switch. (That is, it will conduct
during the time that the oscillating signal is rising and falling
below the threshold voltages, but will not be a "short.") In order
to make use of the benefits of a GaAsFET's capability to close and
open at high frequencies, the oscillating signal 2804 connected to
the gate 2902 preferably has a rapid rise and fall time. That is,
it is preferably a rectangular waveform, and preferably has a pulse
width to period ratio the same as the pulse width to period ratio
of the harmonically rich signal 2814.
[0496] As stated above, if a signal with a continuous and periodic
waveform is modulated, that modulation occurs on every harmonic of
the original waveform. Thus, in the FM and PM modes, when the
information is modulated onto the oscillating signal 2804 and the
oscillating signal 2804 is used to cause the switch 2816 to close
and open, the resulting harmonically rich signal 2814 that is
output from the switch module 2802 will also be modulated. If the
oscillating signal 2804 is crisp, the switch 2816 will close and
open crisply, the harmonically rich signal 2814 will be
harmonically rich, and each of the harmonics of the harmonically
rich signal 2814 will have the information modulated on it.
[0497] Because it is desired that the oscillating signal 2804 be
crisp, harmonic enhancement may be needed in some embodiments.
Harmonic enhancement may also be called "pulse shaping" since the
purpose is to shape the oscillating signal 2804 into a string of
pulses of a desired pulse width. If the oscillating signal is
sinusoidal, harmonic enhancement will shape the sinusoidal signal
into a rectangular (or substantially rectangular) waveform with the
desired pulse width to period ratio. If the oscillating signal 2804
is already a square wave or a pulse, harmonic enhancement will
shape it to achieve the desired ratio of pulse width to period.
This will ensure an efficient transfer of the modulated information
through the switch.
[0498] Three exemplary embodiments of harmonic enhancement are
described below for illustrative purposes. However, the invention
is not limited to these embodiments. Other embodiments will be
apparent to persons skilled in the relevant art(s) based on the
teachings contained herein.
4.1.2 Structural Description
[0499] The shape of the oscillating signal 2804 causes the switch
2816 to close and open. The shape of the oscillating signal 2804
and the selection of the switch 2816 will determine how quickly the
switch 2816 closes and opens, and how long it stays closed compared
to how long it stays open. This then will determine the "crispness"
of the harmonically rich signal 2814. (That is, whether the
harmonically rich signal 2814 is substantially rectangular,
trapezoidal, triangular, etc.) As shown above, in order to ensure
that the desired harmonic has the desired amplitude, the shape of
the oscillating signal 2804 should be substantially optimized.
[0500] The harmonic enhancement module (HEM) 4602 (FIG. 46) is also
referred to as a "pulse shaper." It "shapes" the oscillating
signals 2804 and 3104 that drive the switch modules 2802 and 3102
described in sections 3.3.6-3.3.6.2 and 3.3.7-3.3.7.2. Harmonic
enhancement module 4602 preferably transforms a continuous and
periodic waveform 4604 into a string of pulses 4606. The string of
pulses 4606 will have a period, "T," determined by both the
frequency of the continuous and periodic waveform 4604 and the
design of the pulse shaping circuit within the harmonic enhancement
module 4602. Also, each pulse will have a pulse width, ".tau.,"
determined by the design of the pulse shaping circuit. The period
of the pulse stream, "T," determines the frequency of the switch
closing (the frequency being the inverse of the period), and the
pulse width of the pulses, "T," determines how long the switch
stays closed.
[0501] In the embodiment described above in sections 3.3.6-3.3.6.2
(and 3.3.7-3.3.7.2), when the switch 2816 (or 3116) is open, the
harmonically rich signal 2814 (or 3114) will have an amplitude
substantially equal to the bias signal 2806 (or reference signal
3106). When the switch 2816 (or 3116) is closed, the harmonically
rich signal 2814 (or 3114) will have an amplitude substantially
equal to the potential of signal 2812 or 2818 (or 3112 or 3118) of
the second input 2810 (or 3110) of the switch module 2802 (or
3102). Thus, for the case where the oscillating signal 2804 (or
3104) driving the switch module 2802 (or 3102) is substantially
rectangular, the harmonically rich signal 2814 (or 3114) will have
substantially the same frequency and pulse width as the shaped
oscillating signal 2804 (or 3104) that drives the switch module
2802 (or 3102). This is true for those cases wherein the
oscillating signal 2804 (or 3104) is a rectangular wave. One
skilled in the relevant art(s) will understand that the term
"rectangular wave" can refer to all waveforms that are
substantially rectangular, including square waves and pulses.
[0502] The purpose of shaping the signal is to control the amount
of time that the switch 2816 (or 3116) is closed. As stated above,
the harmonically rich signal 2814 (or 3114) has a substantially
rectangular waveform. Controlling the ratio of the pulse width of
the harmonically rich signal 2814 (or 3114) to its period will
result in the shape of the harmonically rich signal 2814 (or 3114)
being substantially optimized so that the relative amplitudes of
the harmonics are such that the desired harmonic can be extracted
without unnecessary and elaborate amplification and filtering.
4.2 Exemplary Embodiments
[0503] Various embodiments related to the method(s) and
structure(s) described above are presented in this section (and its
subsections). These embodiments are described herein for purposes
of illustration, and not limitation. The invention is not limited
to these embodiments. Alternate embodiments (including equivalents,
extensions, variations, deviations, etc., of the embodiments
described herein) will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. The
invention is intended and adapted to include such alternate
embodiments.
4.2.1 First Embodiment
When a Square Wave Feeds the Harmonic Enhancement Module to Create
One Pulse Per Cycle
[0504] 4.2.1.1 Operational Description.
[0505] According to this embodiment, a continuous periodic waveform
4604 is received and a string of pulses 4606 is output. The
continuous periodic waveform 4604 may be a square wave or any other
continuous periodic waveform that varies from a value recognized as
a "digital low" to a value recognized as a "digital high." One
pulse is generated per cycle of the continuous and periodic
waveform 4604. The description given herein will be for the
continuous periodic waveform 4604 that is a square wave, but one
skilled in the relevant art(s) will appreciate that other waveforms
may also be "shaped" into waveform 4606 by this embodiment.
[0506] 4.2.1.2 Structural Description.
[0507] In this first embodiment of a harmonic enhancement module
4602, herein after referred to as a pulse shaping circuit 4602, a
continuous periodic waveform 4604 that is a square wave is received
by the pulse shaping circuit 4602. The pulse shaping circuit 4602
is preferably comprised of digital logic devices that result in a
string of pulses 4606 being output that has one pulse for every
pulse in the continuous periodic waveform 4604, and preferably has
a .tau./T ratio less than 0.5.
4.2.2 Second Embodiment
When a Square Wave Feeds the Harmonic Enhancement Module to Create
Two Pulses Per Cycle
[0508] 4.2.2.1 Operational Description.
[0509] In this embodiment, a continuous periodic waveform 4604 is
received and a string of pulses 4606 is output. In this embodiment,
there are two pulses output for every period of the continuous
periodic waveform 4604. The continuous periodic waveform 4604 may
be a square wave or any other continuous periodic waveform that
varies from a value recognized as a "digital low" to a value
recognized as a "digital high." The description given herein will
be for a continuous periodic waveform 4604 that is a square wave,
but one skilled in the relevant art(s) will appreciate that other
waveforms may also be "shaped" into waveform 4606 by this
embodiment.
[0510] 4.2.2.2 Structural Description.
[0511] In this second embodiment of a pulse shaping circuit 4602, a
continuous periodic waveform 4604 that is a square wave is received
by the pulse shaping circuit 4602. The pulse shaping circuit 4602
is preferably comprised of digital logic devices that result in a
string of pulses 4606 being output that has two pulses for every
pulse in the continuous periodic waveform 4604, and preferably has
a .tau./T ratio less than 0.5.
4.2.3 Third Embodiment
When any Waveform Feeds the Module
[0512] 4.2.3.1 Operational Description.
[0513] In this embodiment, a continuous periodic waveform 4604 of
any shape is received and a string of pulses 4606 is output.
[0514] 4.2.3.2 Structural Description.
[0515] In this third embodiment of a pulse shaping circuit 4602, a
continuous periodic waveform 4604 of any shape is received by the
pulse shaping circuit 4602. The pulse shaping circuit 4602 is
preferably comprised of a series of stages, each stage shaping the
waveform until it is substantially a string of pulses 4606 with
preferably a .tau./T ratio less than 0.5.
4.2.4 Other Embodiments
[0516] The embodiments described above are provided for purposes of
illustration. These embodiments are not intended to limit the
invention. Alternate embodiments, differing slightly or
substantially from those described herein, will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such alternate embodiments fall within the scope
and spirit of the present invention.
4.3 Implementation Examples
[0517] Exemplary operational and/or structural implementations
related to the method(s), structure(s), and/or embodiments
described above are presented in this section (and its
subsections). These components and methods are presented herein for
purposes of illustration, and not limitation. The invention is not
limited to the particular examples of components and methods
described herein. Alternatives (including equivalents, extensions,
variations, deviations, etc., of those described herein) will be
apparent to persons skilled in the relevant art(s) based on the
teachings contained herein. Such alternatives fall within the scope
and spirit of the present invention.
4.3.1 First Digital Logic Circuit
[0518] An exemplary implementation of the first embodiment
described in sections 4.2.1-4.2.1.2 is illustrated in FIG. 39. In
particular, the circuit shown in FIG. 39A is a typical circuit
design for a pulse shaping circuit 4602 using digital logic
devices. Also shown in FIGS. 39B-39D are representative waveforms
at three nodes within the circuit. In this embodiment, pulse shaper
3900 uses an inverter 3910 and an AND gate 3912 to produce a string
of pulses. An inverter, such as inverter 3910, changes the sign of
the input, and an AND gate, such as AND gate 3912, outputs a
digital "high` when all of the input signals are digital "highs."
The input to pulse shaper 3900 is waveform 3902, and, for
illustrative purposes, is shown here as a square wave. The output
of inverter 3910 is waveform 3904, which is also a square wave.
However, because of the circuitry of the inverter 3910, there is a
delay between the application of the input and the corresponding
sign change of the output. If waveform 3902 starts "low," waveform
3904 will be "high" because it has been inverted by inverter 3910.
When waveform 3902 switches to "high," AND gate 3912 will
momentarily see two "high" signals, thus causing its output
waveform 3906 to be "high." When inverter 3910 has inverted its
input (waveform 3902) and caused waveform 3904 to become "low," AND
gate 3912 will then see only one "high" signal, and the output
waveform 3906 will become "low." Thus, the output waveform 3906
will be "high" for only the period of time that both waveforms 3902
and 3904 are high, which is the time delay of the inverter 3910.
Accordingly, as is apparent from FIGS. 39B-39D, pulse shaper 3900
receives a square wave and generates a string of pulses, with one
pulse generated per cycle of the square wave.
4.3.2 Second Digital Logic Circuit
[0519] An exemplary implementation of the second embodiment
described in sections 4.2.2-4.2.2.2 is illustrated in FIG. 40. In
particular, the circuit of FIG. 40A is a typical circuit design for
a pulse shaping circuit 4602 using digital logic devices. Also
shown in FIGS. 40B-40D are representative waveforms at three nodes
within the circuit. In this embodiment, pulse shaping circuit 4000
uses an inverter 4010 and an exclusive NOR (XNOR) gate 4012. An
XNOR, such as XNOR 4012, outputs a digital "high" when both inputs
are digital "highs" and when both signals are digital "lows."
Waveform 4002, which is shown here as a square wave identical to
that shown above as waveform 3902, begins in the "low" state.
Therefore, the output of inverter 4010 will begin at the "high"
state. Thus, XNOR gate 4012 will see one "high" input and one "low"
input, and its output waveform 4006 will be "low." When waveform
4002 changes to "high," XNOR gate 4012 will have two "high" inputs
until the waveform 4004 switches to "low." Because it sees two
"high" inputs, its output waveform 4006 will be "high." When
waveform 4004 becomes "low," XNOR gate 4012 will again see one
"high" input (waveform 4002) and one "low" input (waveform 4004).
When waveform 4002 switches back to "low," XNOR gate 4012 will see
two "low" inputs, and its output will become "high." Following the
time delay of inverter 4010, waveform 4004 will change to "high,"
and XNOR gate 4012 will again see one "high" input (waveform 4004)
and one "low" input (waveform 4002). Thus, waveform 4006 will again
switch to "low." Accordingly, as is apparent from FIGS. 40B-40D,
pulse shaper 4000 receives a square wave and generates a string of
pulses, with two pulses generated per cycle of the square wave.
4.3.3 Analog Circuit
[0520] An exemplary implementation of the third embodiment
described in sections 4.2.3-4.2.3.2 is illustrated in FIG. 41. In
particular, the circuit shown in FIG. 41 is a typical pulse shaping
circuit 4602 where an input signal 4102 is shown as a sine wave.
Input signal 4102 feeds the first circuit element 4104, which in
turn feeds the second, and so on. Typically, three circuit elements
4104 produce incrementally shaped waveforms 4120, 4122, and 4124
before feeding a capacitor 4106. The output of capacitor 4106 is
shunted to ground 4110 through a resistor 4108 and also feeds a
fourth circuit element 4104. An output signal 4126 is a pulsed
output, with a frequency that is a function of the frequency of
input signal 4102.
[0521] An exemplary circuit for circuit elements 4104 is shown in
FIG. 43. Circuit 4104 is comprised of an input 4310, an output
4312, four FETs 4302, two diodes 4304, and a resistor 4306. One
skilled in the relevant art(s) would recognize that other pulse
shaping circuit designs could also be used without deviating from
the scope and spirit of the invention.
4.3.4 Other Implementations
[0522] The implementations described above are provided for
purposes of illustration. These implementations are not intended to
limit the invention. Alternate implementations, differing slightly
or substantially from those described herein, will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such alternate implementations fall within the
scope and spirit of the present invention.
5. AMPLIFIER MODULE
5.1 High Level Description
[0523] This section (including its subsections) provides a
high-level description of the amplifier module according to the
present invention. In particular, amplification is described at a
high-level. Also, a structural implementation for achieving signal
amplification is described at a high-level. This structural
implementation is described herein for illustrative purposes, and
is not limiting. In particular, the process described in this
section can be achieved using any number of structural
implementations, one of which is described in this section. The
details of such structural implementations will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein.
5.1.1 Operational Description
[0524] Even though the present invention is intended to be used
without requiring amplification, there may be circumstance when, in
the embodiment of the present invention wherein it is being used as
a transmitter, it may prove desirable to amplify the modulated
signal before it is transmitted. In another embodiment of the
invention wherein it is being used as a stable signal source for a
frequency or phase comparator, it may also be desirable to amplify
the resultant signal at the desired frequency.
[0525] The requirement may come about for a number of reasons. A
first may be that the bias/reference signal is too low to support
the desired use. A second may be because the desired output
frequency is very high relative to the frequency of the oscillating
signal that controls the switch. A third reason may be that the
shape of the harmonically rich signal is such that the amplitude of
the desired harmonic is low.
[0526] In the first case, recall that the amplitude of the
bias/reference signal determines the amplitude of the harmonically
rich signal which is present at the output of the switch circuit.
(See sections 3.3.6-3.3.6.2 and 3.3.7-3.3.7.2.) Further recall that
the amplitude of the harmonically rich signal directly impacts the
amplitude of each of the harmonics. (See the equation in section
4.1, above.)
[0527] In the second instance, if the frequency of the oscillating
signal is relatively low compared to the desired output frequency
of the up-converter, a high harmonic will be needed. As an example,
if the oscillating signal is 60 MHz, and the desired output
frequency is at 900 MHz, the 15.sup.th harmonic will be needed. In
the case where .tau./T is 0.1, it can be seen from Table 6000 of
FIG. 60 that the amplitude of the 15.sup.th harmonic (A.sub.15) is
0.0424, which is 21.5% of the amplitude of the first harmonic
(A.sub.1=0.197). There may be instances wherein this is
insufficient for the desired use, and consequently it must be
amplified.
[0528] The third circumstance wherein the amplitude of the output
may need to be amplified is when the shape of the harmonically rich
signal in not "crisp" enough to provide harmonics with enough
amplitude for the desired purpose. If, for example, the
harmonically rich signal is substantially triangular, and given the
example above where the oscillating signal is 60 MHz and the
desired output signal is 900 MHz, the 15.sup.th harmonic of the
triangular wave is 0.00180. This is significantly lower than the
amplitude of the 15.sup.th harmonic of the "0.1" rectangular wave
(shown above to be 0.0424) and can be mathematically shown to be
0.4% of the amplitude of the 1.sup.st harmonic of the triangular
wave (which is 0.405). Thus, in this example, the 1.sup.st harmonic
of the triangular wave has an amplitude that is larger than the
amplitude of the 1.sup.st harmonic of the "0.1" rectangular wave,
but at the 15.sup.th harmonic, the triangular wave is significantly
lower than the "0.1" rectangular wave.
[0529] Another reason that the desired harmonic may need to be
amplified is that circuit elements such as the filter may cause
attenuation in the output signal for which a designer may wish to
compensate.
[0530] The desired output signal can be amplified in a number of
ways. One is to amplify the bias/reference signal to ensure that
the amplitude of the harmonically rich wave form is high. A second
is to amplify the harmonically rich waveform itself. A third is to
amplify the desired harmonic only. The examples given herein are
for illustrative purposes only and are not meant to be limiting on
the present invention. Other techniques to achieve amplification of
the desired output signal would be apparent to those skilled in the
relevant art(s).
5.1.2 Structural Description
[0531] In one embodiment, a linear amplifier is used to amplify the
bias/reference signal. In another embodiment, a linear amplifier is
used to amplify the harmonically rich signal. And in yet another
embodiment, a linear amplifier is used to amplify the desired
output signal. Other embodiments, including the use of non-linear
amplifiers, will be apparent to persons skilled in the relevant
art(s).
5.2 Exemplary Embodiment
[0532] An embodiment related to the method(s) and structure(s)
described above is presented in this section (and its subsections).
This embodiment is described herein for purposes of illustration,
and not limitation. The invention is not limited to this
embodiment. Alternate embodiments (including equivalents,
extensions, variations, deviations, etc., of the embodiment
described herein) will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. The
invention is intended and adapted to include such alternate
embodiments.
5.2.1 Linear Amplifier
[0533] The exemplary linear amplifier described herein will be
directed towards an amplifier composed of solid state electronic
devices to be inserted in the circuit at one or more points. Other
amplifiers suitable for use with the invention will be apparent to
persons skilled in the relevant art(s). As shown in FIG. 47, an
amplifier module 4702 receives a signal requiring amplification
4704 and outputs an amplified signal 4706. It would be apparent to
one skilled in the relevant art(s) that a plurality of embodiments
may be employed without deviating from the scope and intent of the
invention described herein.
[0534] 5.2.1.1 Operational Description.
[0535] The desired output signal can be amplified in a number of
ways. Such amplification as described in the section may be in
addition to the techniques described above to enhance the shape of
the harmonically rich signal by pulse shaping of the oscillating
signal that causes the switch to close and open.
[0536] 5.2.1.2 Structural Description.
[0537] In one embodiment, a linear amplifier is placed between the
bias/reference signal and the switch module. This will increase the
amplitude of the bias/reference signal, and as a result, will raise
the amplitude of the harmonically rich signal that is the output of
the switch module. This will have the effect of not only raising
the amplitude of the harmonically rich signal, it will also raise
the amplitude of all of the harmonics. Some potential limitation of
this embodiment are: the amplified bias/reference signal may exceed
the voltage design limit for the switch in the switch circuit; the
harmonically rich signal coming out of the switch circuit may have
an amplitude that exceeds the voltage design limits of the filter;
and/or unwanted distortion may occur from having to amplify a wide
bandwidth signal.
[0538] A second embodiment employs a linear amplifier between the
switch module and the filter. This will raise the amplitude of the
harmonically rich signal. It will also raise the amplitude of all
of the harmonics of that signal. In an alternate implementation of
this embodiment, the amplifier is tuned so that it only amplifies
the desired frequencies. Thus, it acts both as an amplifier and as
a filter. A potential limitation of this embodiment is that when
the harmonically rich signal is amplified to raise a particular
harmonic to the desired level the amplitude of the whole waveform
is amplified as well. For example, in the case where the amplitude
of the pulse, A.sub.pulse, is equal to 1.0, to raise the 15.sup.th
harmonic from 0.0424 volts to 0.5 volts, the amplitude of each
pulse in the harmonically rich signal, A.sub.pulse, will increase
from 1.0 to 11.8 volts. This may well exceed the voltage design
limit of the filter.
[0539] A third embodiment of an amplifier module will place a
linear amplifier between the filter and the transmission module.
This will only raise the amplitude of the desired harmonic, rather
than the entire harmonically rich signal.
[0540] Other embodiments, such as the use of non-linear amplifiers,
will be apparent to one skilled in the relevant art(s), and will
not be described herein.
5.2.2 Other Embodiments
[0541] The embodiments described above are provided for purposes of
illustration. These embodiments are not intended to limit the
invention. Alternate embodiments, differing slightly or
substantially from those described herein, will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such alternate embodiments fall within the scope
and spirit of the present invention.
5.3 Implementation Examples
[0542] Exemplary operational and/or structural implementations
related to the method(s), structure(s), and/or embodiments
described above are presented in this section (and its
subsections). These components and methods are presented herein for
purposes of illustration, and not limitation. The invention is not
limited to the particular examples of components and methods
described herein. Alternatives (including equivalents, extensions,
variations, deviations, etc., of those described herein) will be
apparent to persons skilled in the relevant art(s) based on the
teachings contained herein. Such alternatives fall within the scope
and spirit of the present invention.
5.3.1 Linear Amplifier
[0543] Although described below as if it were placed after the
filter, the amplifier may also be placed before the filter without
deviating from the intent of the invention
[0544] 5.3.1.1 Operational Description.
[0545] According to embodiments of the invention, a linear
amplifier receives a first signal at a first amplitude, and outputs
a second signal at a second amplitude, wherein the second signal is
proportional to the first signal. It is a objective of an amplifier
that the information embedded onto the first signal waveform will
also be embedded onto the second signal. Typically, it is desired
that there be as little distortion in the information as
possible.
[0546] In a preferred embodiment, the second signal is higher in
amplitude than the first signal, however, there may be
implementations wherein it is desired that the second signal be
lower than the first signal (i.e., the first signal will be
attenuated).
[0547] 5.3.1.2 Structural Description.
[0548] The design and use of a linear amplifier is well known to
those skilled in the relevant art(s). A linear amplifier may be
designed and fabricated from discrete components, or it may be
purchased "off the shelf."
[0549] Exemplary amplifiers are seen in FIG. 48. In the exemplary
circuit diagram of FIG. 48A, six transistors are used in a wideband
amplifier. In the more basic exemplary circuit of FIG. 48B, the
amplifier is composed of one transistor, four resistors, and a
capacitor. Those skilled in the relevant art(s) will recognize that
numerous alternative designs may be used.
5.3.2 Other Implementations
[0550] The implementations described above are provided for
purposes of illustration. These implementations are not intended to
limit the invention. Alternate implementations, differing slightly
or substantially from those described herein, will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such alternate implementations fall within the
scope and spirit of the present invention.
6. RECEIVER/TRANSMITTER SYSTEM
[0551] The present invention is for a method and system for
up-conversion of electromagnetic signals. In one embodiment, the
invention is a source of a stable high frequency reference signal.
In a second embodiment, the invention is a transmitter.
[0552] This section describes a third embodiment. In the third
embodiment, the transmitter of the present invention to be used in
a receiver/transmitter communications system. This third embodiment
may also be referred to as the communications system embodiment,
and the combined receiver/transmitter circuit is referred to as a
"transceiver." There are several alternative enhancements to the
communications systems embodiment.
[0553] The following sections describe systems and methods related
to exemplary embodiments for a receiver/transmitter system. It
should be understood that the invention is not limited to the
particular embodiments described below. Equivalents, extensions,
variations, deviations, etc., of the following will be apparent to
persons skilled in the relevant art(s) based on the teachings
contained herein. Such equivalents, extensions, variations,
deviations, etc., are within the scope and spirit of the present
invention.
6.1 High Level Description
[0554] This section provides a high-level description of a
receiver/transmitter system according to the present invention. The
implementations are described herein for illustrative purposes, and
are not limiting. In particular, any number of functional and
structural implementations may be used, several of which are
described in this section. The details of such functional and
structural implementations will be apparent to persons skilled in
the relevant art(s) based on the teachings contained herein.
[0555] According to a first embodiment of the transmitter of the
present invention is used with a traditional superheterodyne
receiver. In this embodiment, the transmitter and the receiver can
operate either in a full-duplex mode or in a half-duplex mode. In a
full duplex mode, the transceiver can transmit and receive
simultaneously. In the half-duplex mode, the transceiver can either
transmit or receive, but cannot do both simultaneously. The
full-duplex and the half-duplex modes will be discussed together
for this embodiment.
[0556] A second embodiment of the transceiver is for the
transmitter of the present invention to be used with a universal
frequency down conversion circuit being used as a receiver. In this
embodiment the transceiver is used in a half-duplex mode.
[0557] A third embodiment of the transceiver is for the transmitter
of the present invention to be used with a universal frequency down
conversion circuit, where the transceiver is used in a full-duplex
mode.
[0558] These embodiments of the transceiver are described
below.
6.2 Exemplary Embodiments and Implementation Examples
[0559] Various embodiments related to the method(s) and
structure(s) described above and exemplary operational and/or
structural implementations related to those embodiments are
presented in this section (and its subsections). These embodiments,
components, and methods are described herein for purposes of
illustration, and not limitation. The invention is not limited to
these embodiments or to the particular examples of components and
methods described herein. Alternatives (including equivalents,
extensions, variations, deviations, etc., of those described
herein) will be apparent to persons skilled in the relevant art(s)
based on the teachings contained herein. Such alternatives fall
within the scope and spirit of the present invention, and the
invention is intended and adapted to include such alternatives.
6.2.1 First Embodiment
The Transmitter of the Present Invention being Used in a Circuit
with a Superheterodyne Receiver
[0560] A typical superheterodyne receiver is shown in FIG. 49. An
antenna 4904 receives a signal 4902. Typically, signal 4902 is a
radio frequency (RF) signal which is routed to a filter 4910 and an
amplifier 4908. The filter 4910 removes all but a frequency range
that includes the desired frequency, and the amplifier 4908 ensures
that the signal strength will be sufficient for further processing.
The output of amplifier 4908 is a signal 4911.
[0561] A local oscillator 4914 generates an oscillating signal 4916
which is combined with signal 4911 by mixer 4912. The output of
mixer 4912 is a signal 4934 which is amplified by an amplifier 4918
and filtered by a filter 4920. The purpose of amplifier 4918 is to
ensure that the strength of signal 4934 is sufficient for further
processing, and the purpose of filter 4920 is to remove the
undesired frequencies.
[0562] A second local oscillator 4924 generates a second
oscillating signal 4926 which is combined with the
amplified/filtered signal 4934 by a mixer 4922. The output of mixer
4922 is signal 4936. Again, an amplifier 4928 and a filter 4930
ensure that the signal 4936 is at the desired amplitude and
frequency. The resulting signal is then routed to decoder 4932
where the intelligence is extracted to obtain baseband signal
4938.
[0563] Signal 4934 is referred to as the first intermediate
frequency (IF) signal, and signal 4936 is referred to as the second
IF signal. Thus, the combination of local oscillator 4914 and mixer
4912 can be referred to as the first IF stage, and the combination
of local oscillator 4924 and mixer 4922 can be referred to as the
second IF stage.
[0564] Exemplary frequencies for the circuit of FIG. 49 are as
follows. Signal 4902 may be 900 MHz. The oscillator signal 4916 may
be at 830 MHz, which will result in the frequency of the first IF
signal, signal 4934, being at 70 MHz. If the second oscillating
signal 4926 is at 59 MHz, the second IF signal, signal 4936, would
be at 11 MHz. This frequency is typical of second IF
frequencies.
[0565] Other superheterodyne receiver configurations are well known
and these can be used in the transceiver embodiments of the
invention. Also, the exemplary frequencies mentioned above are
provide for illustrative purposes only, and are not limiting.
[0566] FIG. 50 shows a transmitter of the present invention in a
transceiver circuit with a typical superheterodyne receiver.
Accordingly, FIG. 50 illustrates an exemplary transceiver circuit
of the invention. The transceiver includes a receiver module 5001,
which is implemented using any superheterodyne receiver
configuration, and which is described above. The transceiver also
includes a transmitter module 5003, which is described below.
[0567] In the FM and PM modes, an information signal 5004 modulates
an intermediate signal to produce the oscillating signal 5002.
Oscillating signal 5002 is shaped by signal shaper 5010 to produce
a string of pulses 5008 (see the discussion above regarding the
benefits of harmonic enhancement). The string of pulses 5008 drives
the switch module 5012. In the FM/PM modes, a bias/reference signal
5006 is also received by switch module 5012. The output of switch
module 5012 is a harmonically rich signal 5022. Harmonically rich
signal 5022 is comprised of a plurality of sinusoidal components,
and is routed to a "high Q" filter that will remove all but the
desired output frequency(ies). The desired output frequency 5024 is
amplified by an amplifier 5016 and routed to a transmission module
5018 which outputs a transmission signal 5026 which is routed to a
duplexer 5020. The purpose of duplexer 5020 is to permit a single
antenna to be used simultaneously for both receiving and
transmitting signals. The combination of received signal 4902 and
transmission signal 5026 is a duplexed signal 5028.
[0568] In the AM mode, the same circuit of FIG. 50 applies, except:
(1) an information signal 5030 replaces information signal 5004;
(2) bias/reference signal 5006 is a function of the information
signal 5030; and (3) oscillating signal 5002 is not modulated.
[0569] This description is for the full-duplex mode of the
transceiver wherein the transmitting portion of the communications
system is a separate circuit than the receiver portion. A possible
embodiment of a half-duplex mode is described below.
[0570] Alternate embodiments of the transceiver are possible. For
example, FIGS. 51A through 51D illustrate an embodiment of the
transceiver wherein it may be desired, for cost or other
considerations, for an oscillator to be shared by both the
transmitter portion and the receiver portion of the circuit. To do
this, a trade off must be made in selecting the frequency of the
oscillator. In FIG. 51A, a local oscillator 5104 generates an
oscillating signal 5106 which is mixed with signal 4911 to generate
a first IF signal 5108. A local oscillator 5110 generates a second
oscillating signal 5112 which is mixed with the first IF signal
5108 to generate a second IF signal 5114. For the example herein,
the frequencies of the oscillating signals 5106 and 5112 will be
lower than the frequencies of signal 4911 and first IF signal 5108,
respectively. (One skilled in the relevant art(s) will recognize
that, because the mixers 4912 and 4922 create both the sum and the
difference of the signals they receive, the oscillator frequencies
could be higher than the signal frequencies.)
[0571] As described in the example above, a typical second IF
frequency is 11 MHz. The selection of this IF frequency is less
flexible than is the selection of the first IF frequency, since the
second IF frequency is routed to a decoder where the signal is
demodulated and decoded. Typically, demodulators and decoders are
designed to receive signals at a predetermined, fixed frequency,
e.g., 11 MHz. If this is the case, the combination of the first IF
signal 5108 and the second oscillating signal 5112 must generate a
second IF signal with a second IF frequency of 11 MHz. Recall that
the received signal 4902 was 900 MHz in the example above. To
achieve the second IF signal frequency of 11 MHz, the frequencies
of the oscillating signals 4916 and 4926 were set at 830 MHz and 59
MHz. Before setting the frequencies of the oscillating signals 5106
and 5112, the desired frequency of the transmitted signal must be
determined. If it, too, is 900 MHz, then the frequency of the
oscillating signal that causes the switch in the present invention
to open and close must be a "sub-harmonic" of 900 MHz. That is, it
must be the quotient of 900 MHz divided by an integer. (In other
words, 900 MHz must be a harmonic of the oscillating signal that
drives the switch.) The table below is a list of some of the
sub-harmonics of 900
TABLE-US-00001 sub-harmonic frequency 1.sup.st 900 MHz 2.sup.nd 450
3.sup.rd 300 4.sup.th 225 5.sup.th 180 10.sup.th 90 15.sup.th
60
Recall that the frequency of the second oscillating signal 4926 in
FIGS. 49 and 50 was 59 MHz. Notice that the frequency of the
15.sup.th sub-harmonic is 60 MHz. If the frequency of oscillating
signal 5112 of FIG. 51 were set at 60 MHz, it could also be used as
the oscillating signal to operate the switches in switch module
5126 of FIG. 51B and switch module 5136 of FIG. 51C. If this were
done, the frequency of the first IF signal would be 71 MHz (rather
than 70 MHz in the previous example of a stand-alone receiver), as
indicated below:
First I F frequency = Second I F frequency + Second oscillating
frequency = 11 MHz + 60 MHz = 71 MHz ##EQU00001##
The frequency of the first oscillating signal 5106 can be
determined from the values of the first IF frequency and the
frequency of the received signal 4902. In this example, the
frequency of the received signal is 900 MHz and the frequency of
the first IF signal is 71 MHz. Therefore, the frequency of the
first oscillating signal 5106 must be 829 MHz, as indicated
below:
First oscillating frequency = Freq of recieved signal - First I F
freq = 900 MHz - 71 MHz = 829 MHz ##EQU00002##
Thus the frequencies of the oscillating signals 5106 and 5112 are
829 MHz and 60 MHz, respectively.
[0572] In FIG. 51B, the PM embodiment is shown. The second
oscillating signal 5112 is routed to a phase modulator 5122 where
it is modulated by the information signal 5120 to generate a PM
signal 5132. PM signal 5132 is routed to a harmonic enhancement
module 5124 to create a string of pulses 5133. The string of pulses
5133 is also a phase modulated signal and is used to cause the
switch in switch module 5126 to open and close. Also entering
switch module 5126 is a bias signal 5128. The output of switch
module 5126 is a harmonically rich signal 5134.
[0573] In FIG. 51C, the AM embodiment is shown. The second
oscillating signal 5112 directly enters the harmonic enhancement
module 5124 to create a string of pulses 5138. String of pulses
5138 (not modulated in this embodiment) then enters a switch module
5136 where it causes a switch to open and close. Also entering
switch module 5136 is a reference signal 5140. Reference signal is
created by summing module 5130 by combining information signal 5120
with bias signal 5128. It is well known to those skilled in the
relevant art(s) that the information signal 5120 may be used as the
reference signal without being combined with the bias signal 5128.
The output of switch module 5136 is a harmonically rich signal
5134.
[0574] The scope of the invention includes an FM embodiment wherein
the oscillator 5110 of the receiver circuit is used as a source for
an oscillating signal for the transmitter circuit. In the
embodiments discussed above, the FM embodiment requires a voltage
controlled oscillator (VCO) rather than a simple local oscillator.
There are circuit designs that would be apparent to those skilled
in the relevant art(s) based on the discussion contained herein,
wherein a VCO is used in place of a local oscillator in the
receiver circuit.
[0575] In FIG. 51D, the harmonically rich signal 5134 is filtered
by a filter 5142, which removes all but the desired output
frequency 5148. The desired output frequency 5148 is amplified by
amplifier module 5146 and routed to transmission module 5150. The
output of transmission module 5150 is a transmission signal 5144.
Transmission signal 5144 is then routed to the antenna 4904 for
transmission.
[0576] Those skilled in the relevant art(s) will understand that
there are numerous combinations of oscillator frequencies, stages,
and circuits that will meet the scope and intent of this invention.
Thus, the description included herein is for illustrative purposes
only and not meant to be limiting.
6.2.2 Second Embodiment
The Transmitter of the Present Invention being Used with a
Universal Frequency Down-Converter in a Half-Duplex Mode
[0577] An exemplary receiver using universal frequency down
conversion techniques is shown in FIG. 52 and described in section
6.3, below. An antenna 5202 receives an electromagnetic (EM) signal
5220. EM signal 5220 is routed through a capacitor 5204 to a first
terminal of a switch 5210. The other terminal of switch 5210 is
connected to ground 5212 in this exemplary embodiment. A local
oscillator 5206 generates an oscillating signal 5228 which is
routed through a pulse shaper 5208. The result is a string of
pulses 5230. The selection of the oscillator 5206 and the design of
the pulse shaper 5208 control the frequency and pulse width of the
string of pulses 5230. The string of pulses 5230 control the
opening and closing of switch 5210. As a result of the opening and
closing of switch 5210, a down converted signal 5222 results. Down
converted signal 5222 is routed through an amplifier 5214 and a
filter 5216, and a filtered signal 5224 results. In a preferred
embodiment, filtered signal 5224 is at baseband, and a decoder 5218
may only be needed to convert digital to analog or to remove
encryption before outputting the baseband information signal. This
then is a universal frequency down conversion receiver operating in
a direct down conversion mode, in that it receives the EM signal
5220 and down converts it to baseband signal 5226 without requiring
an IF or a demodulator. In an alternate embodiment, the filtered
signal 5224 may be at an "offset" frequency. That is, it is at an
intermediate frequency, similar to that described above for the
second IF signal in a typical superheterodyne receiver. In this
case, the decoder 5218 would be used to demodulate the filtered
signal so that it could output a baseband signal 5226.
[0578] An exemplary transmitter using the present invention is
shown in FIG. 53. In the FM and PM embodiments, an information
signal 5302 modulates an oscillating signal 5306 which is routed to
a pulse shaping circuit 5310 which outputs a string of pulses 5311.
The string of pulses 5311 controls the opening and closing of the
switch 5312. One terminal of switch 5312 is connected to ground
5314, and the second terminal of switch 5312 is connected through a
resistor 5330 to a bias/reference signal 5308. In the FM and PM
modes, bias/reference signal 5308 is preferably a non-varying
signal, often referred to simply as the bias signal. In the AM
mode, the oscillating signal 5306 is not modulated, and the
bias/reference signal is a function of the information signal 5304.
In one embodiment, information signal 5304 is combined with a bias
voltage to generate the reference signal 5308. In an alternate
embodiment, the information signal 5304 is used without being
combined with a bias voltage. Typically, in the AM mode, this
bias/reference signal is referred to as the reference signal to
distinguish it from the bias signal used in the FM and PM modes.
The output of switch 5312 is a harmonically rich signal 5316 which
is routed to a "high Q" filter which removes the unwanted
frequencies that exist as harmonic components of harmonically rich
signal 5316. Desired frequency 5320 is amplified by amplifier
module 5322 and routed to transmission module 5324 which outputs a
transmission signal 5326. Transmission signal is output by antenna
5328 in this embodiment.
[0579] For the FM and PM modulation modes, FIGS. 54A, 54B, and 54C
show the combination of the present invention of the transmitter
and the universal frequency down-conversion receiver in the
half-duplex mode according to an embodiment of the invention. That
is, the transceiver can transmit and receive, but it cannot do both
simultaneously. It uses a single antenna 5402, a single oscillator
5444/5454 (depending on whether the transmitter is in the FM or PM
modulation mode), a single pulse shaper 5438, and a single switch
5420 to transmit and to receive. In the receive function,
"Receiver/transmitter" (R/T) switches 5406, 5408, and 5446/5452 (FM
or PM) would all be in the receive position, designated by (R). The
antenna 5402 receives an EM signal 5404 and routes it through a
capacitor 5407. In the FM modulation mode, oscillating signal 5436
is generated by a voltage controlled oscillator (VCO) 5444. Because
the transceiver is performing the receive function, switch 5446
connects the input to the VCO 5444 to ground 5448. Thus, VCO 5444
will operate as if it were a simple oscillator. In the PM
modulation mode, oscillating signal 5436 is generated by local
oscillator 5454 which is routed through phase modulator 5456. Since
the transceiver is performing the receive function, switch 5452 is
connected to ground 5448, and there is no modulating input to phase
modulator. Thus, local oscillator 5454 and phase modulator 5456
operate as if they were a simple oscillator. One skilled in the
relevant art(s) will recognize based on the discussion contained
herein that there are numerous embodiments wherein an oscillating
signal 5436 can be generated to control the switch 5420.
[0580] Oscillating signal 5436 is shaped by pulse shaper 5438 to
produce a string of pulses 5440. The string of pulses 5440 cause
the switch 5420 to open and close. As a result of the switch
opening and closing, a down converted signal 5409 is generated. The
down converted signal 5409 is amplified and filtered to create a
filtered signal 5413. In an embodiment, filtered signal 5413 is at
baseband and, as a result of the down conversion, is demodulated.
Thus, a decoder 5414 may not be required except to convert digital
to analog or to decrypt the filtered signal 5413. In an alternate
embodiment, the filtered signal 5413 is at an "offset" frequency,
so that the decoder 5414 is needed to demodulate the filtered
signal and create a demodulated baseband signal.
[0581] When the transceiver is performing the transmit function,
the R/T switches 5406, 5408, and 5446/5452 (FM or PM) are in the
(T) position. In the FM modulation mode, an information signal 5450
is connected by switch 5446 to VCO 5444 to create a frequency
modulated oscillating signal 5436. In the PM modulation mode switch
5452 connects information signal 5450 to the phase modulator 5456
to create a phase modulated oscillating signal 5436. Oscillation
signal 5436 is routed through pulse shaper 5438 to create a string
of pulses 5440 which in turn cause switch 5420 to open and close.
One terminal of switch 5420 is connected to ground 5442 and the
other is connected through switch R/T 5408 and resistor 5423 to a
bias signal 5422. The result is a harmonically rich signal 5424
which is routed to a "high Q" filter 5426 which removes the
unwanted frequencies that exist as harmonic components of
harmonically rich signal 5424. Desired frequency 5428 is amplified
by amplifier module 5430 and routed to transmission module 5432
which outputs a transmission signal 5434. Again, because the
transceiver is performing the transmit function, R/T switch 5406
connects the transmission signal to the antenna 5402.
[0582] In the AM modulation mode, the transceiver operates in the
half duplex mode as shown in FIG. 55. The only distinction between
this modulation mode and the FM and PM modulation modes described
above, is that the oscillating signal 5436 is generated by a local
oscillator 5502, and the switch 5420 is connected through the R/T
switch 5408 and resistor 5423 to a reference signal 5506. Reference
signal 5506 is generated when information signal 5450 and bias
signal 5422 are combined by a summing module 5504. It is well known
to those skilled in the relevant art(s) that the information signal
5450 may be used as the reference signal 5506 without being
combined with the bias signal 5422, and may be connected directly
(through resistor 5423 and R/T switch 5408) to the switch 5420.
6.2.3 Third Embodiment
The Transmitter of the Present Invention being Used with a
Universal Frequency Down Converter in a Full-Duplex Mode
[0583] The full-duplex mode differs from the half-duplex mode in
that the transceiver can transmit and receive simultaneously.
Referring to FIG. 56, to achieve this, the transceiver preferably
uses a separate circuit for each function. A duplexer 5604 is used
in the transceiver to permit the sharing of an antenna 5602 for
both the transmit and receive functions.
[0584] The receiver function performs as follows. The antenna 5602
receives an EM signal 5606 and routes it through a capacitor 5607
to one terminal of a switch 5626. The other terminal of switch 5626
is connected to ground 5628, and the switch is driven as a result
of a string of pulses 5624 created by local oscillator 5620 and
pulse shaper 5622. The opening and closing of switch 5626 generates
a down converted signal 5614. Down converted signal 5614 is routed
through a amplifier 5608 and a filter 5610 to generate filtered
signal 5616. Filtered signal 5616 may be at baseband and be
demodulated or it may be at an "offset" frequency. If filtered
signal 5616 is at an offset frequency, decoder 5612 will demodulate
it to create the demodulated baseband signal 5618. In a preferred
embodiment, however, the filtered signal 5616 will be a demodulated
baseband signal, and decoder 5612 may not be required except to
convert digital to analog or to decrypt filtered signal 5616. This
receiver portion of the transceiver can operate independently from
the transmitter portion of the transceiver.
[0585] The transmitter function is performed as follows. In the FM
and PM modulation modes, an information signal 5648 modulates an
oscillating signal 5630. In the AM modulation mode, the oscillating
signal 5630 is not modulated. The oscillating signal is shaped by
pulse shaper 5632 and a string of pulses 5634 is created. This
string of pulses 5634 causes a switch 5636 to open and close. One
terminal of switch 5636 is connected to ground 5638, and the other
terminal is connected through a resistor 5647 to a bias/reference
signal 5646. In the FM and PM modulation modes, bias/reference
signal 5646 is referred to as a bias signal 5646, and it is
substantially non-varying. In the AM modulation mode, an
information signal 5650 may be combined with the bias signal to
create what is referred to as the reference signal 5646. The
reference signal 5646 is a function of the information signal 5650.
It is well known to those skilled in the relevant art(s) that the
information signal 5650 may be used as the bias/reference signal
5646 directly without being summed with a bias signal. A
harmonically rich signal 5652 is generated and is filtered by a
"high Q" filter 5640, thereby producing a desired signal 5654. The
desired signal 5654 is amplified by amplifier 5642 and routed to
transmission module 5644. The output of transmission module 5644 is
transmission signal 5656. Transmission signal 5656 is routed to
duplexer 5604 and then transmitted by antenna 5602. This
transmitter portion of the transceiver can operate independently
from the receiver portion of the transceiver.
[0586] Thus, as described above, the transceiver embodiment the
present invention as shown in FIG. 56 can perform full-duplex
communications in all modulation modes.
6.2.4 Other Embodiments and Implementations
[0587] Other embodiments and implementations of the
receiver/transmitter of the present invention would be apparent to
one skilled in the relevant art(s) based on the discussion
herein.
[0588] The embodiments and implementations described above are
provided for purposes of illustration. These embodiments and
implementations are not intended to limit the invention.
Alternatives, differing slightly or substantially from those
described herein, will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. Such
alternate embodiments and implementations fall within the scope and
spirit of the present invention.
6.3 Summary Description of Down-Conversion Using a Universal
Frequency Translation Module
[0589] The following discussion describes down-converting using a
Universal Frequency Translation Module. The down-conversion of an
EM signal by aliasing the EM signal at an aliasing rate is fully
described in co-pending U.S. patent application entitled "Method
and System for Down-Converting Electromagnetic Signals," Ser. No.
09/176,022, filed Oct. 21, 1998, the full disclosure of which is
incorporated herein by reference. A relevant portion of the above
mentioned patent application is summarized below to describe
down-converting an input signal to produce a down-converted signal
that exists at a lower frequency or a baseband signal.
[0590] FIG. 64A illustrates an aliasing module 6400 for
down-conversion using a universal frequency translation (UFT)
module 6402 which down-converts an EM input signal 6404. In
particular embodiments, aliasing module 6400 includes a switch 6408
and a capacitor 6410. The electronic alignment of the circuit
components is flexible. That is, in one implementation, the switch
6408 is in series with input signal 6404 and capacitor 6410 is
shunted to ground (although it may be other than ground in
configurations such as differential mode). In a second
implementation (see FIG. 64A-1), the capacitor 6410 is in series
with the input signal 6404 and the switch 6408 is shunted to ground
(although it may be other than ground in configurations such as
differential mode). Aliasing module 6400 with UFT module 6402 can
be easily tailored to down-convert a wide variety of
electromagnetic signals using aliasing frequencies that are well
below the frequencies of the EM input signal 6404.
[0591] In one implementation, aliasing module 6400 down-converts
the input signal 6404 to an intermediate frequency (IF) signal. In
another implementation, the aliasing module 6400 down-converts the
input signal 6404 to a demodulated baseband signal. In yet another
implementation, the input signal 6404 is a frequency modulated (FM)
signal, and the aliasing module 6400 down-converts it to a non-FM
signal, such as a phase modulated (PM) signal or an amplitude
modulated (AM) signal. Each of the above implementations is
described below.
[0592] In an embodiment, the control signal 6406 includes a train
of pulses that repeat at an aliasing rate that is equal to, or less
than, twice the frequency of the input signal 6404 In this
embodiment, the control signal 6406 is referred to herein as an
aliasing signal because it is below the Nyquist rate for the
frequency of the input signal 6404. Preferably, the frequency of
control signal 6406 is much less than the input signal 6404.
[0593] The train of pulses 6418 as shown in FIG. 64D controls the
switch 6408 to alias the input signal 6404 with the control signal
6406 to generate a down-converted output signal 6412. More
specifically, in an embodiment, switch 6408 closes on a first edge
of each pulse 6420 of FIG. 64D and opens on a second edge of each
pulse. When the switch 6408 is closed, the input signal 6404 is
coupled to the capacitor 6410, and charge is transferred from the
input signal to the capacitor 6410. The charge stored during
successive pulses forms down-converted output signal 6412.
[0594] Exemplary waveforms are shown in FIGS. 64B-64F.
[0595] FIG. 64B illustrates an analog amplitude modulated (AM)
carrier signal 6414 that is an example of input signal 6404. For
illustrative purposes, in FIG. 64C, an analog AM carrier signal
portion 6416 illustrates a portion of the analog AM carrier signal
6414 on an expanded time scale. The analog AM carrier signal
portion 6416 illustrates the analog AM carrier signal 6414 from
time t.sub.0 to time t.sub.1.
[0596] FIG. 64D illustrates an exemplary aliasing signal 6418 that
is an example of control signal 6406. Aliasing signal 6418 is on
approximately the same time scale as the analog AM carrier signal
portion 6416. In the example shown in FIG. 64D, the aliasing signal
6418 includes a train of pulses 6420 having negligible apertures
that tend towards zero (the invention is not limited to this
embodiment, as discussed below). The pulse aperture may also be
referred to as the pulse width as will be understood by those
skilled in the art(s). The pulses 6420 repeat at an aliasing rate,
or pulse repetition rate of aliasing signal 6418. The aliasing rate
is determined as described below, and further described in
co-pending U.S. patent application entitled "Method and System for
Down-Converting Electromagnetic Signals," Ser. No. 09/176,022,
filed Oct. 21, 1998.
[0597] As noted above, the train of pulses 6420 (i.e., control
signal 6406) control the switch 6408 to alias the analog AM carrier
signal 6416 (i.e., input signal 6404) at the aliasing rate of the
aliasing signal 6418. Specifically, in this embodiment, the switch
6408 closes on a first edge of each pulse and opens on a second
edge of each pulse. When the switch 6408 is closed, input signal
6404 is coupled to the capacitor 6410, and charge is transferred
from the input signal 6404 to the capacitor 6410. The charge
transferred during a pulse is referred to herein as an
under-sample. Exemplary under-samples 6422 form down-converted
signal portion 6424 (FIG. 64E) that corresponds to the analog AM
carrier signal portion 6416 (FIG. 64C) and the train of pulses 6420
(FIG. 64D). The charge stored during successive under-samples of AM
carrier signal 6414 form the down-converted signal 6424 (FIG. 64E)
that is an example of down-converted output signal 6412 (FIG. 64A).
In FIG. 64F a demodulated baseband signal 6426 represents the
demodulated baseband signal 6424 after filtering on a compressed
time scale. As illustrated, down-converted signal 6426 has
substantially the same "amplitude envelope" as AM carrier signal
6414. Therefore, FIGS. 64B-64F illustrate down-conversion of AM
carrier signal 6414.
[0598] The waveforms shown in FIGS. 64B-64F are discussed herein
for illustrative purposes only, and are not limiting. Additional
exemplary time domain and frequency domain drawings, and exemplary
methods and systems of the invention relating thereto, are
disclosed in co-pending U.S. patent application entitled "Method
and System for Down-Converting Electromagnetic Signals," Ser. No.
09/176,022, filed Oct. 21, 1998.
[0599] The aliasing rate of control signal 6406 determines whether
the input signal 6404 is down-converted to an IF signal,
down-converted to a demodulated baseband signal, or down-converted
from an FM signal to a PM or an AM signal. Generally, relationships
between the input signal 6404, the aliasing rate of the control
signal 6406, and the down-converted output signal 6412 are
illustrated below:
(Freq. of input signal 6403)=n(Freq. of control signal
6406).+-.(Freq. of down-converted output signal 6412)
For the examples contained herein, only the "+" condition will be
discussed. The value of n represents a harmonic or sub-harmonic of
input signal 6404 (e.g., n=0.5, 1, 2, 3, . . . ).
[0600] When the aliasing rate of control signal 6406 is off-set
from the frequency of input signal 6404, or off-set from a harmonic
or sub-harmonic thereof, input signal 6404 is down-converted to an
IF signal. This is because the under-sampling pulses occur at
different phases of subsequent cycles of input signal 6404. As a
result, the under-samples form a lower frequency oscillating
pattern. If the input signal 6404 includes lower frequency changes,
such as amplitude, frequency, phase, etc., or any combination
thereof, the charge stored during associated under-samples reflects
the lower frequency changes, resulting in similar changes on the
down-converted IF signal. For example, to down-convert a 901 MHz
input signal to a 1 MHz IF signal, the frequency of the control
signal 6406 would be calculated as follows:
(Freq.sub.input-Freq.sub.IF)/n=Freq.sub.control(901 MHz-1
MHz)/n=900/n
For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal
6406 would be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300
MHz, 225 MHz, etc.
[0601] Exemplary time domain and frequency domain drawings,
illustrating down-conversion of analog and digital AM, PM and FM
signals to IF signal, and exemplary methods and systems thereof,
are disclosed in co-pending U.S. patent application entitled
"Method and System for Down-Converting Electromagnetic Signals,"
Ser. No. 09/176,022, filed Oct. 21, 1998.
[0602] Alternatively, when the aliasing rate of the control signal
6406 is substantially equal to the frequency of the input signal
6404, or substantially equal to a harmonic or sub-harmonic thereof,
input signal 6404 is directly down-converted to a demodulated
baseband signal. This is because, without modulation, the
under-sampling pulses occur at the same point of subsequent cycles
of the input signal 6404. As a result, the under-samples form a
constant output baseband signal. If the input signal 6404 includes
lower frequency changes, such as amplitude, frequency, phase, etc.,
or any combination thereof, the charge stored during associated
under-samples reflects the lower frequency changes, resulting in
similar changes on the demodulated baseband signal. For example, to
directly down-convert a 900 MHz input signal to a demodulated
baseband signal (i.e., zero IF), the frequency of the control
signal 6406 would be calculated as follows:
(Freq.sub.input-Freq.sub.IF)/n=Freq.sub.control(900 MHz-0
MHz)/n=900/n
For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal
6406 should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz,
300 MHz, 225 MHz, etc.
[0603] Exemplary time domain and frequency domain drawings,
illustrating direct down-conversion of analog and digital AM and PM
signals to demodulated baseband signals, and exemplary methods and
systems thereof, are disclosed in the co-pending U.S. patent
application entitled "Method and System for Down-Converting
Electromagnetic Signals," Ser. No. 09/176,022, filed Oct. 21,
1998.
[0604] Alternatively, to down-convert an input FM signal to a
non-FM signal, a frequency within the FM bandwidth must be
down-converted to baseband (i.e., zero IF). As an example, to
down-convert a frequency shift keying (FSK) signal (a sub-set of
FM) to a phase shift keying (PSK) signal (a subset of PM), the
mid-point between a lower frequency F.sub.1 and an upper frequency
F.sub.2 (that is, [(F.sub.1+F.sub.2)/2]) of the FSK signal is
down-converted to zero IF. For example, to down-convert an FSK
signal having F.sub.1 equal to 899 MHz and F.sub.2 equal to 901
MHz, to a PSK signal, the aliasing rate of the control signal 6406
would be calculated as follows:
Frequency of the input = ( F 1 + F 2 ) / 2 = ( 899 MHz + 901 MHz )
/ 2 = 900 MHz ##EQU00003##
Frequency of the down-converted signal=0 (i.e., baseband)
(Freq.sub.input-Freq.sub.IF)/n=Freq.sub.control(900 MHz-0
MHz)/n=900/n
For n=0.5, 1, 2, 3, etc., the frequency of the control signal 6406
should be substantially equal to 1.8 GHz, 900 MHz, 450 MHz, 300
MHz, 225 MHz, etc. The frequency of the down-converted PSK signal
is substantially equal to one half the difference between the lower
frequency F.sub.1 and the upper frequency F.sub.2.
[0605] As another example, to down-convert a FSK signal to an
amplitude shift keying (ASK) signal (a subset of AM), either the
lower frequency F.sub.1 or the upper frequency F.sub.2 of the FSK
signal is down-converted to zero IF. For example, to down-convert
an FSK signal having F.sub.1 equal to 900 MHz and F.sub.2 equal to
901 MHz, to an ASK signal, the aliasing rate of the control signal
6406 should be substantially equal to;
(900 MHz-0 MHz)/n=900 MHz/n, or (901 MHz-0 MHz)/n=901 MHz/n.
For the former case of 900 MHz/n, and for n=0.5, 1, 2, 3, 4, etc.,
the frequency of the control signal 6406 should be substantially
equal to 1.8 GHz, 900 MHz, 450 MHz, 300 MHz, 225 MHz, etc. For the
latter case of 901 MHz/n, and for n=0.5, 1, 2, 3, 4, etc., the
frequency of the control signal 6406 should be substantially equal
to 1.802 GHz, 901 MHz, 450.5 MHz, 300.333 MHz, 225.25 MHz, etc. The
frequency of the down-converted AM signal is substantially equal to
the difference between the lower frequency F.sub.1 and the upper
frequency F.sub.2 (i.e., 1 MHz).
[0606] Exemplary time domain and frequency domain drawings,
illustrating down-conversion of FM signals to non-FM signals, and
exemplary methods and systems thereof, are disclosed in the
co-pending U.S. patent application entitled "Method and System for
Down-Converting Electromagnetic Signals," Ser. No. 09/176,022,
filed Oct. 21, 1998.
[0607] In an embodiment, the pulses of the control signal 6406 have
negligible apertures that tend towards zero. This makes the UFT
module 6402 a high input impedance device. This configuration is
useful for situations where minimal disturbance of the input signal
may be desired.
[0608] In another embodiment, the pulses of the control signal 6406
have non-negligible apertures that tend away from zero. This makes
the UFT module 6402 a lower input impedance device. This allows the
lower input impedance of the UFT module 6402 to be substantially
matched with a source impedance of the input signal 6404. This also
improves the energy transfer from the input signal 6404 to the
down-converted output signal 6412, and hence the efficiency and
signal to noise (s/n) ratio of UFT module 6402.
[0609] Exemplary systems and methods for generating and optimizing
the control signal 6406, and for otherwise improving energy
transfer and s/n ratio, are disclosed in the co-pending U.S. patent
application entitled "Method and System for Down-Converting
Electromagnetic Signals," Ser. No. 09/176,022, filed Oct. 21,
1998.
7. DESIGNING A TRANSMITTER ACCORDING TO AN EMBODIMENT OF THE
PRESENT INVENTION
[0610] This section (including its subsections) provides a
high-level description of an exemplary process to be used to design
a transmitter according to an embodiment of the present invention.
The techniques described herein are also applicable to designing a
frequency up-converter for any application, and for designing the
applications themselves. The descriptions are contained herein for
illustrative purposes and are not limiting. Alternatives (including
equivalents, extensions, variations, deviations, etc., of those
described herein) will be apparent to persons skilled in the
relevant art(s) based on the teachings contained herein. Such
alternatives fall within the scope and spirit of the present
invention, and the invention is intended and adapted to include
such alternative.
[0611] The discussion herein describes an exemplary process to be
used to design a transmitter according to an embodiment of the
present invention. An exemplary circuit for a transmitter of the
present invention operating in the FM embodiment is shown in FIG.
57A. Likewise, FIG. 57B illustrates the transmitter of the present
invention operating in the PM embodiment, and FIG. 57C shows the
transmitter of the present invention operating in the AM
embodiment. These circuits have been shown in previous figures, but
are presented here to facilitate the discussion of the design. As
the "I/Q" embodiment of the present invention is a subset of the PM
embodiment, it will not be shown in a separate figure here, since
the design approach will be very similar to that for the PM
embodiment.
[0612] Depending on the application and on the implementation, some
of the design considerations may not apply. For example, and
without limitation, in some cases it may not be necessary to
optimize the pulse width or to include an amplifier.
7.1 Frequency of the Transmission Signal
[0613] The first step in the design process is to determine the
frequency of the desired transmission signal 5714. This is
typically determined by the application for which the transmitter
is to be used. The present invention is for a transmitter that can
be used for all frequencies within the electromagnetic (EM)
spectrum. For the examples herein, the explanation will focus on
the use of the transmitter in the 900 MHz to 950 MHz range. Those
skilled in the relevant art(s) will recognize that the analysis
contained herein may be used for any frequency or frequency
range.
7.2 Characteristics of the Transmission Signal
[0614] Once the frequency of the desired transmission signal 5714
is known, the characteristics of the signal must be determined.
These characteristics include, but are not limited to, whether the
transmitter will operate at a fixed frequency or over a range of
frequencies, and if it is to operate over a range of frequencies,
whether those frequencies are continuous or are divided into
discrete "channels." If the frequency range is divided into
discrete channels, the spacing between the channels must be
ascertained. As an example, cordless phones operating in this
frequency range may operate on discrete channels that are 50 KHz
apart. That is, if the cordless phones operate in the 905 MHz to
915 MHz range (inclusive), the channels could be found at 905.000,
905.050, 905.100, . . . , 914.900, 914.950, and 915.000.
7.3 Modulation Scheme
[0615] Another characteristic that must be ascertained is the
desired modulation scheme that is to be used. As described above in
sections 2.1-2.2.4, above, these modulation schemes include FM, PM,
AM, etc., and any combination or subset thereof, specifically
including the widely used "I/Q" subset of PM. Just as the frequency
of the desired transmission signal 5714 is typically determined by
the intended application, so too is the modulation scheme.
7.4 Characteristics of the Information Signal
[0616] The characteristics of an information signal 5702 are also
factors in the design of the transmitter circuit. Specifically, the
bandwidth of the information signal 5702 defines the minimum
frequency for an oscillating signal 5704, 5738, 5744 (for the FM,
PM, and AM modes, respectively).
7.5 Characteristics of the Oscillating Signal
[0617] The desired frequency of the oscillating signal 5704, 5738,
5744 is also a function of the frequency and characteristics of the
desired transmission signal 5714. Also, the frequency and
characteristics of the desired transmission signal 5714 are factors
in determining the pulse width of the pulses in a string of pulses
5706. Note that the frequency of the oscillating signal 5704, 5738,
5744 is substantially the same as the frequency of the string of
pulses 5706. (An exception, which is discussed below, is when a
pulse shaping circuit 5722 increases the frequency of the
oscillating signal 5704, 5738, 5744 in a manner similar to that
described above in section 4.3.2.) Note also that the frequency and
pulse width of the string of pulses 5706 is substantially the same
as the frequency and pulse width of a harmonically rich signal
5708.
7.5.1 Frequency of the Oscillating Signal
[0618] The frequency of the oscillating signal 5704, 5738, 5744
must be a subharmonic of the frequency of the desired transmission
signal 5714. A subharmonic is the quotient obtained by dividing the
fundamental frequency, in this case the frequency of the desired
transmission signal 5714, by an integer. When describing the
frequency of certain signals, reference is often made herein to a
specific value. It is understood by those skilled in the relevant
art(s) that this reference is to the nominal center frequency of
the signal, and that the actual signal may vary in frequency above
and below this nominal center frequency based on the desired
modulation technique being used in the circuit. As an example to be
used herein, if the frequency of the desired transmission signal is
910 MHz, and it is to be used in an FM mode where, for example, the
frequency range of the modulation is 40 KHz, the actual frequency
of the signal will vary .+-.20 KHz around the nominal center
frequency as a function of the information being transmitted. That
is, the frequency of the desired transmission signal will actually
range between 909.980 MHz and 910.020 MHz.
[0619] The first ten subharmonics of a 910.000 MHz signal are given
below.
TABLE-US-00002 harmonic frequency 1.sup.st 910.000 MHz 2.sup.nd
455.000 3.sup.rd 303.333 . . . 4.sup.th 227.500 5.sup.th 182.000
6.sup.th 151.666 . . . 7.sup.th 130.000 8.sup.th 113.750 9.sup.th
101.111 . . . 10.sup.th 91.000
The oscillating signal 5704, 5738, 5744 can be at any one of these
frequencies or, if desired, at a lower subharmonic. For discussion
herein, the 9.sup.th subharmonic will be chosen. Those skilled in
the relevant art(s) will understand that the analysis herein
applies regardless of which harmonic is chosen. Thus the nominal
center frequency of the oscillating signal 5704, 5738, 5744 will be
101.1111 MHz. Recalling that in the FM mode, the frequency of the
desired transmission signal 5714 is actually 910.000 MHz.+-.0.020
MHz, it can be shown that the frequency of the oscillating signal
5704 will vary .+-.0.00222 MHz (i.e., from 101.10889 MHz to
101.11333 MHz). The frequency and frequency sensitivity of the
oscillating signal 5704 will drive the selection or design of the
voltage controlled oscillator (VCO) 5720.
[0620] Another frequency consideration is the overall frequency
range of the desired transmission signal. That is, if the
transmitter is to be used in the cordless phone of the above
example and will transmit on all channels between 905 MHz and 915
MHz, the VCO 5720 (for the FM mode) or the local oscillator (LO)
5734 (for the PM and AM modes) will be required to generate
oscillating frequencies 5704, 5738, 5744 that range from 100.5556
MHz to 101.6667 MHz. (That is, the 9.sup.th subharmonic of 910
MHz.+-.5 MHz). In some applications, such as the cellular phone,
the frequencies will change automatically, based on the protocols
of the overall cellular system (e.g., moving from one cell to an
adjacent cell). In other applications, such as a police radio, the
frequencies will change based on the user changing channels.
[0621] In some applications, different models of the same
transmitter will transmit signals at different frequencies, but
each model will, itself, only transmit a single frequency. A
possible example of this might be remote controlled toy cars, where
each toy car operates on its own frequency, but, in order for
several toy cars to operate in the same area, there are several
frequencies at which they could operate. Thus, the design of the
VCO 5720 or LO 5734 will be such that it is able to be tuned to a
set frequency when the circuit is fabricated, but the user will
typically not be able to adjust the frequency.
[0622] It is well known to those skilled in the relevant art(s)
that several of the criteria to be considered in the selection or
design of an oscillator (VCO 5720 or LO 5734) include, but are not
limited to, the nominal center frequency of the desired
transmission signal 5714, the frequency sensitivity caused by the
desired modulation scheme, the range of all possible frequencies
for the desired transmission signal 5714, and the tuning
requirements for each specific application. Another important
criterion is the determination of the subharmonic to be used, but
unlike the criteria listed above which are dependent on the desired
application, there is some flexibility in the selection of the
subharmonic.
7.5.2 Pulse Width of the String of Pulses
[0623] Once the frequency of the oscillating signal 5704, 5738,
5744 has been selected, the pulse width of the pulses in the stream
of pulses 5706 must be determined. (See sections 4-4.3.4, above,
for a discussion of harmonic enhancement and the impact the
pulse-width-to-period ratio has on the relative amplitudes of the
harmonics in a harmonically rich signal 5708.) In the example used
above, the 9.sup.th subharmonic was selected as the frequency of
the oscillating signal 5704, 5738, 5744. In other words, the
frequency of the desired transmission signal will be the 9.sup.th
harmonic of the oscillating signal 5704, 5738, 5744. One approach
in selecting the pulse width might be to focus entirely on the
frequency of the oscillating signal 5704, 5738, 5744 and select a
pulse width and observe its operation in the circuit. For the case
where the harmonically rich signal 5708 has a unity amplitude, and
the pulse-width-to-period ratio is 0.1, the amplitude of the
9.sup.th harmonic will be 0.0219. Looking again at Table 6000 and
FIG. 58 it can be seen that the amplitude of the 9.sup.th harmonic
is higher than that of the 10.sup.th harmonic (which is zero) but
is less than half the amplitude of the 8.sup.th harmonic. Because
the 9.sup.th harmonic does have an amplitude, this
pulse-width-to-period ratio could be used with proper filtering.
Typically, a different ratio might be selected to try and find a
ratio that would provide a higher amplitude.
[0624] Looking at Eq. 1 in section 4.1.1, it is seen that the
relative amplitude of any harmonic is a function of the number of
the harmonic and the pulse-width-to-period ratio of the underlying
waveform. Applying calculus of variations to the equation, the
pulse-width-to-period ratio that yields the highest amplitude
harmonic for any given harmonic can be determined.
[0625] From Eq. 1, where A.sub.n is the amplitude of the n.sup.th
harmonic,
A.sub.n=[A.sub.pulse][(2/.pi.)/n] sin {n.pi.(.tau./T)] Eq. 2
If the amplitude of the pulse, A.sub.pulse, is set to unity (i.e.,
equal to 1), the equation becomes
A.sub.n=[(2/n.pi.)] sin [n.pi.(.tau./T)] Eq. 3
[0626] From this equation, it can be seen that for any value of n
(the harmonic) the amplitude of that harmonic, A.sub.n, is a
function of the pulse-width-to-period ratio, .tau./T. To determine
the highest value of A.sub.n for a given value of n, the first
derivative of A.sub.n with respect to .tau./T is taken. This gives
the following equations.
.delta. ( A n ) / .delta. ( .tau. / T ) = .delta. { [ 2 / ( n .pi.
) ] sin [ n .pi. ( .tau. / T ) ] } / .delta. ( .tau. / T ) = [ 2 /
( n .pi. ) ] .delta. [ sin [ n .pi. ( .tau. / T ) ] / .delta. (
.tau. / T ) Eq . 5 = [ 2 / ( n .pi. ) ] cos [ n .pi. ( .tau. / T )
] Eq . 6 Eq . 4 ##EQU00004##
From calculus of variations, it is known that when the first
derivative is set equal to zero, the value of the variable that
will yield a relative maximum (or minimum) can be determined.
.delta.(A.sub.n)/.delta.(.tau./T)=0 Eq. 7
[2/(n.pi.)] cos [n.pi.(.tau./T)]=0 Eq. 8
cos [n.pi.(.tau./T)]=0 Eq. 9
From trigonometry, it is known that for Eq. 9 to be true,
n.pi.(.tau./T)=.pi./2(or 3.pi./2, 5.pi./2, etc.) Eq. 10
.tau./T=(.pi./2)/(n.pi.) Eq. 11
.tau./T=1/(2n)(or 3/(2n), 5/(2n), etc.) Eq. 12
The above derivation is well known to those skilled in the relevant
art(s). From Eq. 12, it can be seen that if the
pulse-width-to-period ratio is equal to 1/(2n), the amplitude of
the harmonic should be substantially optimum. For the case of the
9.sup.th harmonic, Eq. 12 will yield a pulse-width-to-period ratio
of 1/(29) or 0.0556. For the amplitude of this 9.sup.th harmonic,
Table 6100 of FIG. 61 shows that it is 0.0796. This is an
improvement over the previous amplitude for a pulse-width-to-period
ratio of 0.1. Table 6100 also shows that the 9.sup.th harmonic for
this pulse-width-to-period ratio has the highest amplitude of any
9.sup.th harmonic, which bears out the derivation above. The
frequency spectrum for a pulse-width-to-period ratio of 0.0556 is
shown in FIG. 59. (Note that other pulse-width-to-period ratios of
3/(2n), 5/(2n), etc., will have amplitudes that are equal to but
not larger than this one.)
[0627] This is one approach to determining the desired
pulse-width-to-period ratio. Those skilled in the relevant art(s)
will understand that other techniques may also be used to select a
pulse-width-to-period ratio.
7.6 Design of the Pulse Shaping Circuit
[0628] Once the determination has been made as to the desired
frequency of the oscillating signal 5704, 5738, 5744 and of the
pulse width, the pulse shaping circuit 5722 can be designed.
Looking back to sections 4-4.3.4 it can be seen that the pulse
shaping circuit 5722 can not only produce a pulse of a desired
pulse width, but it can also cause the frequency of the string of
pulses 5706 to be higher than the frequency of the oscillating
signal 5704, 5738, 5744. Recall that the pulse-width-to-period
ratio applies to the pulse-width-to-period ratio of the
harmonically rich signal 5708 and not to the pulse-width-to-period
ratio of the oscillating signal 5704, 5738, 5744, and that the
frequency and pulse width of the harmonically rich signal 5708
mirrors the frequency and pulse width of the string of pulses 5706.
Thus, if in the selection of the VCO 5720 or LO 5734 it was desired
to choose an oscillator that is lower than that required for the
selected harmonic, the pulse shaping circuit 5733 can be used to
increase the frequency. Going back to the previous example, the
frequency of the oscillating signal 5704, 5738, 5744 could be
50.5556 MHz rather than 101.1111 MHz if the pulse shaping circuit
5722 was designed such as discussed in sections 4.2.2-4.2.2.2
(shown in FIGS. 40A-40D) not only to shape the pulse, but also to
double the frequency. While that discussion was specifically for a
square wave input, those skilled in the relevant art(s) will
understand that similar techniques will apply to non-rectangular
waveforms (e.g., a sinusoidal wave). This use of the pulse shaping
circuit to double the frequency has a possible advantage in that it
allows the design and selection of an oscillator (VCO 5720 of LO
5734) with a lower frequency, if that is a consideration.
[0629] It should also be understood that the pulse shaping circuit
5722 is not always required. If the design or selection of the VCO
5720 or LO 5734 was such that the oscillating signal 5704, 5738,
5744 was a substantially rectangular wave, and that substantially
rectangular wave had a pulse-width-to-period ratio that was
adequate, the pulse shaping circuit 5722 could be eliminated.
7.7 Selection of the Switch
[0630] The selection of a switch 5724 can now be made. The switch
5724 is shown in the examples of FIGS. 57A, 57B, and 57C as a
GaAsFET. However, it may be any switching device of any technology
that can open and close "crisply" enough to accommodate the
frequency and pulse width of the string of pulses 5706.
7.7.1 Optimized Switch Structures
Switches of Different Sizes
[0631] In an embodiment, the switch modules discussed herein can be
implemented as a series of switches operating in parallel as a
single switch. The series of switches can be transistors, such as,
for example, field effect transistors (FET), bi-polar transistors,
or any other suitable circuit switching devices. The series of
switches can be comprised of one type of switching device, or a
combination of different switching devices.
[0632] For example, FIG. 73 illustrates a switch module 7300. In
FIG. 73, the switch module is illustrated as a series of FETs
7302a-n. The FETs 7302a-n can be any type of FET, including, but
not limited to, a MOSFET, a JFET, a GaAsFET, etc. Each of FETs
7302a-n includes a gate 7304a-n, a source 7306a-n, and a drain
7308a-n. The series of FETs 7302a-n operate in parallel. Gates
7304a-n are coupled together, sources 7306a-n are coupled together,
and drains 7308a-n are coupled together. Each of gates 7304a-n
receives the control signal 2804, 3104 to control the switching
action between corresponding sources 7306a-n and drains 7308a-n.
Generally, the corresponding sources 7306a-n and drains 7308a-n of
each of FETs 7302a-n are interchangeable. There is no numerical
limit to the number of FETs. Any limitation would depend on the
particular application, and the "a-n" designation is not meant to
suggest a limit in any way.
[0633] In an embodiment, FETs 7302a-n have similar characteristics.
In another embodiment, one or more of FETs 7302a-n have different
characteristics than the other FETs. For example, FETs 7302a-n may
be of different sizes. In CMOS, generally, the larger size a switch
is (meaning the larger the area under the gate between the source
and drain regions), the longer it takes for the switch to turn on.
The longer turn on time is due in part to a higher gate to channel
capacitance that exists in larger switches. Smaller CMOS switches
turn on in less time, but have a higher channel resistance. Larger
CMOS switches have lower channel resistance relative to smaller
CMOS switches. Different turn on characteristics for different size
switches provides flexibility in designing an overall switch module
structure. By combining smaller switches with larger switches, the
channel conductance of the overall switch structure can be tailored
to satisfy given requirements.
[0634] In an embodiment, FETs 7302a-n are CMOS switches of
different relative sizes. For example, FET 7302a may be a switch
with a smaller size relative to FETs 7302b-n. FET 7302b may be a
switch with a larger size relative to FET 7302a, but smaller size
relative to FETs 7302c-n. The sizes of FETs 7302c-n also may be
varied relative to each other. For instance, progressively larger
switch sizes may be used. By varying the sizes of FETs 7302a-n
relative to each other, the turn on characteristic curve of the
switch module can be correspondingly varied. For instance, the turn
on characteristic of the switch module can be tailored such that it
more closely approaches that of an ideal switch. Alternately, the
switch module could be tailored to produce a shaped conductive
curve.
[0635] By configuring FETs 7302a-n such that one or more of them
are of a relatively smaller size, their faster turn on
characteristic can improve the overall switch module turn on
characteristic curve. Because smaller switches have a lower gate to
channel capacitance, they can turn on more rapidly than larger
switches.
[0636] By configuring FETs 7302a-n such that one or more of them
are of a relatively larger size, their lower channel resistance
also can improve the overall switch module turn on characteristics.
Because larger switches have a lower channel resistance, they can
provide the overall switch structure with a lower channel
resistance, even when combined with smaller switches. This improves
the overall switch structure's ability to drive a wider range of
loads. Accordingly, the ability to tailor switch sizes relative to
each other in the overall switch structure allows for overall
switch structure operation to more nearly approach ideal, or to
achieve application specific requirements, or to balance trade-offs
to achieve specific goals, as will be understood by persons skilled
in the relevant arts(s) from the teachings herein.
[0637] It should be understood that the illustration of the switch
module as a series of FETs 7302a-n in FIG. 73 is for example
purposes only. Any device having switching capabilities could be
used to implement the switch module, as will be apparent to persons
skilled in the relevant art(s) based on the discussion contained
herein.
Reducing Overall Switch Area
[0638] Circuit performance also can be improved by reducing overall
switch area. As discussed above, smaller switches (i.e., smaller
area under the gate between the source and drain regions) have a
lower gate to channel capacitance relative to larger switches. The
lower gate to channel capacitance allows for lower circuit
sensitivity to noise spikes. FIG. 74A illustrates an embodiment of
a switch module, with a large overall switch area. The switch
module of FIG. 74A includes twenty FETs 7402-7440. As shown, FETs
7402-7440 are the same size ("Wd" and "Ing" parameters are equal).
Input source 7446 produces the input EM signal. Pulse generator
7448 produces the energy transfer signal for FETs 7402-7440.
Capacitor C1 is the storage element for the input signal being
sampled by FETs 7402-7440. FIGS. 74B-74Q illustrate example
waveforms related to the switch module of FIG. 74A. FIG. 74B shows
a received 1.01 GHz EM signal to be sampled and downconverted to a
10 MHz intermediate frequency signal. FIG. 74C shows an energy
transfer signal having an aliasing rate of 200 MHz, which is
applied to the gate of each of the twenty FETs 7402-7440. The
energy transfer signal includes a train of energy transfer pulses
having non-negligible apertures that tend away from zero time in
duration. The energy transfer pulses repeat at the aliasing rate.
FIG. 74D illustrates the affected received EM signal, showing
effects of transferring energy at the aliasing rate, at point 7442
of FIG. 74A. FIG. 74E illustrates a down-converted signal at point
7444 of FIG. 74A, which is generated by the down-conversion
process.
[0639] FIG. 74F illustrates the frequency spectrum of the received
1.01 GHz EM signal. FIG. 74G illustrates the frequency spectrum of
the received energy transfer signal. FIG. 74H illustrates the
frequency spectrum of the affected received EM signal at point 7442
of FIG. 74A. FIG. 74I illustrates the frequency spectrum of the
down-converted signal at point 7444 of FIG. 74A.
[0640] FIGS. 74J-74M respectively further illustrate the frequency
spectra of the received 1.01 GHz EM signal, the received energy
transfer signal, the affected received EM signal at point 7442 of
FIG. 74A, and the down-converted signal at point 7444 of FIG. 74A,
focusing on a narrower frequency range centered on 1.00 GHz. As
shown in FIG. 74L, a noise spike exists at approximately 1.0 GHz on
the affected received EM signal at point 7442 of FIG. 74A. This
noise spike may be radiated by the circuit, causing interference at
1.0 GHz to nearby receivers.
[0641] FIGS. 74N-74Q respectively illustrate the frequency spectra
of the received 1.01 GHz EM signal, the received energy transfer
signal, the affected received EM signal at point 7442 of FIG. 74A,
and the down-converted signal at point 7444 of FIG. 74A, focusing
on a narrow frequency range centered near 10.0 MHz. In particular,
FIG. 74Q shows that an approximately 5 mV signal was downconverted
at approximately 10 MHz.
[0642] FIG. 75A illustrates an alternative embodiment of the switch
module, this time with fourteen FETs 7502-7528 shown, rather than
twenty FETs 7402-7440 as shown in FIG. 74A. Additionally, the FETs
are of various sizes (some "Wd" and "lng" parameters are different
between FETs).
[0643] FIGS. 75B-75Q, which are example waveforms related to the
switch module of FIG. 75A, correspond to the similarly designated
figures of FIGS. 74B-74Q. As FIG. 75L shows, a lower level noise
spike exists at 1.0 GHz than at the same frequency of FIG. 74L.
This correlates to lower levels of circuit radiation. Additionally,
as FIG. 75Q shows, the lower level noise spike at 1.0 GHz was
achieved with no loss in conversion efficiency. This is represented
in FIG. 75Q by the approximately 5 mV signal downconverted at
approximately 10 MHz. This voltage is substantially equal to the
level downconverted by the circuit of FIG. 74A. In effect, by
decreasing the number of switches, which decreases overall switch
area, and by reducing switch area on a switch-by-switch basis,
circuit parasitic capacitance can be reduced, as would be
understood by persons skilled in the relevant art(s) from the
teachings herein. In particular this may reduce overall gate to
channel capacitance, leading to lower amplitude noise spikes and
reduced unwanted circuit radiation.
[0644] It should be understood that the illustration of the
switches above as FETs in FIGS. 74A-74Q and 75A-75Q is for example
purposes only. Any device having switching capabilities could be
used to implement the switch module, as will be apparent to persons
skilled in the relevant art(s) based on the discussion contained
herein.
Charge Injection Cancellation
[0645] In embodiments wherein the switch modules discussed herein
are comprised of a series of switches in parallel, in some
instances it may be desirable to minimize the effects of charge
injection. Minimizing charge injection is generally desirable in
order to reduce the unwanted circuit radiation resulting therefrom.
In an embodiment, unwanted charge injection effects can be reduced
through the use of complementary n-channel MOSFETs and p-channel
MOSFETs. N-channel MOSFETs and p-channel MOSFETs both suffer from
charge injection. However, because signals of opposite polarity are
applied to their respective gates to turn the switches on and off,
the resulting charge injection is of opposite polarity. As a
result, n-channel MOSFETs and p-channel MOSFETs may be paired to
cancel their corresponding charge injection. Hence, in an
embodiment, the switch module may be comprised of n-channel MOSFETs
and p-channel MOSFETS, wherein the members of each are sized to
minimize the undesired effects of charge injection.
[0646] FIG. 77A illustrates an alternative embodiment of the switch
module, this time with fourteen n-channel FETs 7702-7728 and twelve
p-channel FETs 7730-7752 shown, rather than twenty FETs 7402-7440
as shown in FIG. 74A. The n-channel and p-channel FETs are arranged
in a complementary configuration. Additionally, the FETs are of
various sizes (some "Wd" and "lng" parameters are different between
FETs).
[0647] FIGS. 77B-77Q, which are example waveforms related to the
switch module of FIG. 77A, correspond to the similarly designated
figures of FIGS. 74B-74Q. As FIG. 77L shows, a lower level noise
spike exists at 1.0 GHz than at the same frequency of FIG. 74L.
This correlates to lower levels of circuit radiation. Additionally,
as FIG. 77Q shows, the lower level noise spike at 1.0 GHz was
achieved with no loss in conversion efficiency. This is represented
in FIG. 77Q by the approximately 5 mV signal downconverted at
approximately 10 MHz. This voltage is substantially equal to the
level downconverted by the circuit of FIG. 74A. In effect, by
arranging the switches in a complementary configuration, which
assists in reducing charge injection, and by tailoring switch area
on a switch-by-switch basis, the effects of charge injection can be
reduced, as would be understood by persons skilled in the relevant
art(s) from the teachings herein. In particular this leads to lower
amplitude noise spikes and reduced unwanted circuit radiation.
[0648] It should be understood that the use of FETs in FIGS.
77A-77Q in the above description is for example purposes only. From
the teachings herein, it would be apparent to persons of skill in
the relevant art(s) to manage charge injection in various
transistor technologies using transistor pairs.
Overlapped Capacitance
[0649] The processes involved in fabricating semiconductor
circuits, such as MOSFETs, have limitations. In some instances,
these process limitations may lead to circuits that do not function
as ideally as desired. For instance, a non-ideally fabricated
MOSFET may suffer from parasitic capacitances, which in some cases
may cause the surrounding circuit to radiate noise. By fabricating
circuits with structure layouts as close to ideal as possible,
problems of non-ideal circuit operation can be minimized.
[0650] FIG. 76A illustrates a cross-section of an example n-channel
enhancement-mode MOSFET 7600, with ideally shaped n+ regions.
MOSFET 7600 includes a gate 7602, a channel region 7604, a source
contact 7606, a source region 7608, a drain contact 7610, a drain
region 7612, and an insulator 7614. Source region 7608 and drain
region 7612 are separated by p-type material of channel region
7604. Source region 7608 and drain region 7612 are shown to be n+
material. The n+ material is typically implanted in the p-type
material of channel region 7604 by an ion implantation/diffusion
process. Ion implantation/diffusion processes are well known by
persons skilled in the relevant art(s). Insulator 7614 insulates
gate 7602 which bridges over the p-type material. Insulator 7614
generally comprises a metal-oxide insulator. The channel current
between source region 7608 and drain region 7612 for MOSFET 7600 is
controlled by a voltage at gate 7602.
[0651] Operation of MOSFET 7600 shall now be described. When a
positive voltage is applied to gate 7602, electrons in the p-type
material of channel region 7604 are attracted to the surface below
insulator 7614, forming a connecting near-surface region of n-type
material between the source and the drain, called a channel. The
larger or more positive the voltage between the gate contact 7606
and source region 7608, the lower the resistance across the region
between.
[0652] In FIG. 76A, source region 7608 and drain region 7612 are
illustrated as having n+ regions that were formed into idealized
rectangular regions by the ion implantation process. FIG. 76B
illustrates a cross-section of an example n-channel
enhancement-mode MOSFET 7616 with non-ideally shaped n+ regions.
Source region 7620 and drain region 7622 are illustrated as being
formed into irregularly shaped regions by the ion implantation
process. Due to uncertainties in the ion implantation/diffusion
process, in practical applications, source region 7620 and drain
region 7622 do not form rectangular regions as shown in FIG. 76A.
FIG. 76B shows source region 7620 and drain region 7622 forming
exemplary irregular regions. Due to these process uncertainties,
the n+ regions of source region 7620 and drain region 7622 also may
diffuse further than desired into the p-type region of channel
region 7618, extending underneath gate 7602 The extension of the
source region 7620 and drain region 7622 underneath gate 7602 is
shown as source overlap 7624 and drain overlap 7626. Source overlap
7624 and drain overlap 7626 are further illustrated in FIG. 76C.
FIG. 76C illustrates a top-level view of an example layout
configuration for MOSFET 7616. Source overlap 7624 and drain
overlap 7626 may lead to unwanted parasitic capacitances between
source region 7620 and gate 7602, and between drain region 7622 and
gate 7602. These unwanted parasitic capacitances may interfere with
circuit function. For instance, the resulting parasitic
capacitances may produce noise spikes that are radiated by the
circuit, causing unwanted electromagnetic interference.
[0653] As shown in FIG. 76C, an example MOSFET 7616 may include a
gate pad 7628. Gate 7602 may include a gate extension 7630, and a
gate pad extension 7632. Gate extension 7630 is an unused portion
of gate 7602 required due to metal implantation process tolerance
limitations. Gate pad extension 7632 is a portion of gate 7602 used
to couple gate 7602 to gate pad 7628. The contact required for gate
pad 7628 requires gate pad extension 7632 to be of non-zero length
to separate the resulting contact from the area between source
region 7620 and drain region 7622. This prevents gate 7602 from
shorting to the channel between source region 7620 and drain region
7622 (insulator 7614 of FIG. 76B is very thin in this region).
Unwanted parasitic capacitances may form between gate extension
7630 and the substrate (FET 7616 is fabricated on a substrate), and
between gate pad extension 7632 and the substrate. By reducing the
respective areas of gate extension 7630 and gate pad extension
7632, the parasitic capacitances resulting therefrom can be
reduced. Accordingly, embodiments address the issues of uncertainty
in the ion implantation/diffusion process. it will be obvious to
persons skilled in the relevant art(s) how to decrease the areas of
gate extension 7630 and gate pad extension 7632 in order to reduce
the resulting parasitic capacitances.
[0654] It should be understood that the illustration of the
n-channel enhancement-mode MOSFET is for example purposes only. The
present invention is applicable to depletion mode MOSFETs, and
other transistor types, as will be apparent to persons skilled in
the relevant art(s) based on the discussion contained herein.
7.7.2 Phased D2D--Splitter in CMOS
[0655] FIG. 72A illustrates an embodiment of a splitter circuit
7200 implemented in CMOS. This embodiment is provided for
illustrative purposes, and is not limiting. In an embodiment,
splitter circuit 7200 is used to split a local oscillator (LO)
signal into two oscillating signals that are approximately
90.degree. out of phase. The first oscillating signal is called the
I-channel oscillating signal. The second oscillating signal is
called the Q-channel oscillating signal. The Q-channel oscillating
signal lags the phase of the I-channel oscillating signal by
approximately 90.degree.. Splitter circuit 7200 includes a first
I-channel inverter 7202, a second I-channel inverter 7204, a third
I-channel inverter 7206, a first Q-channel inverter 7208, a second
Q-channel inverter 7210, an I-channel flip-flop 7212, and a
Q-channel flip-flop 7214.
[0656] FIGS. 72F-J are example waveforms used to illustrate signal
relationships of splitter circuit 7200. The waveforms shown in
FIGS. 72F-J reflect ideal delay times through splitter circuit 7200
components. LO signal 7216 is shown in FIG. 72F. First, second, and
third I-channel inverters 7202, 7204, and 7206 invert LO signal
7216 three times, outputting inverted LO signal 7218, as shown in
FIG. 72G. First and second Q-channel inverters 7208 and 7210 invert
LO signal 7216 twice, outputting non-inverted LO signal 7220, as
shown in FIG. 72H. The delay through first, second, and third
I-channel inverters 7202, 7204, and 7206 is substantially equal to
that through first and second Q-channel inverters 7208 and 7210, so
that inverted LO signal 7218 and non-inverted LO signal 7220 are
approximately 180.degree. out of phase. The operating
characteristics of the inverters may be tailored to achieve the
proper delay amounts, as would be understood by persons skilled in
the relevant art(s).
[0657] I-channel flip-flop 7212 inputs inverted LO signal 7218.
Q-channel flip-flop 7214 inputs non-inverted LO signal 7220. In the
current embodiment, I-channel flip-flop 7212 and Q-channel
flip-flop 7214 are edge-triggered flip-flops. When either flip-flop
receives a rising edge on its input, the flip-flop output changes
state. Hence, I-channel flip-flop 7212 and Q-channel flip-flop 7214
each output signals that are approximately half of the input signal
frequency. Additionally, as would be recognized by persons skilled
in the relevant art(s), because the inputs to I-channel flip-flop
7212 and Q-channel flip-flop 7214 are approximately 180.degree. out
of phase, their resulting outputs are signals that are
approximately 90.degree. out of phase. I-channel flip-flop 7212
outputs I-channel oscillating signal 7222, as shown in FIG. 72I.
Q-channel flip-flop 7214 outputs Q-channel oscillating signal 7224,
as shown in FIG. 72J. Q-channel oscillating signal 7224 lags the
phase of I-channel oscillating signal 7222 by 90.degree., also as
shown in a comparison of FIGS. 721 and 72J.
[0658] FIG. 72B illustrates a more detailed circuit embodiment of
the splitter circuit 7200 of FIG. 72. The circuit blocks of FIG.
72B that are similar to those of FIG. 72A are indicated by
corresponding reference numbers. FIGS. 72C-D show example output
waveforms relating to the splitter circuit 7200 of FIG. 72B. FIG.
72C shows I-channel oscillating signal 7222. FIG. 72D shows
Q-channel oscillating signal 7224. As is indicated by a comparison
of FIGS. 72C and 72D, the waveform of Q-channel oscillating signal
7224 of FIG. 72D lags the waveform of I-channel oscillating signal
7222 of FIG. 72C by approximately 90.degree..
[0659] It should be understood that the illustration of the
splitter circuit 7200 in FIGS. 72A and 72B is for example purposes
only. Splitter circuit 7200 may be comprised of an assortment of
logic and semiconductor devices of a variety of types, as will be
apparent to persons skilled in the relevant art(s) based on the
discussion contained herein.
7.8 Design of the Filter
[0660] The design of the filter 5726 is determined by the frequency
and frequency range of the desired transmission signal 5714. As
discussed above in sections 3.3.9-3.3.9.2, the term "Q" is used to
describe the ratio of the center frequency of the output of the
filter to the bandwidth of the "3 dB down" point. The trade offs
that were made in the selection of the subharmonic to be used is a
factor in designing the filter. That is, if, as an excursion to the
example given above, the frequency of the desired transmission
signal were again 910 MHz, but the desired subharmonic were the
50.sup.th subharmonic, then the frequency of that 50.sup.th
subharmonic would be 18.2000 MHz. This means that the frequencies
seen by the filter will be 18.200 MHz apart. Thus, the "Q" will
need to be high enough to avoid allowing information from the
adjacent frequencies being passed through. The other consideration
for the "Q" of the filter is that it must not be so tight that it
does not permit the usage of the entire range of desired
frequencies.
7.9 Selection of an Amplifier
[0661] An amplifier module 5728 will be needed if the signal is not
large enough to be transmitted or if it is needed for some
downstream application. This can occur because the amplitude of the
resultant harmonic is too small. It may also occur if the filter
5726 has attenuated the signal.
7.10 Design of the Transmission Module
[0662] A transmission module 5730, which is optional, ensures that
the output of the filter 5726 and the amplifier module 5728 is able
to be transmitted. In the implementation wherein the transmitter is
used to broadcast EM signals over the air, the transmission module
matches the impedance of the output of the amplifier module 5728
and the input of an antenna 5732. This techniques is well known to
those skilled in the relevant art(s). If the signal is to be
transmitted over a point-to-point line such as a telephone line (or
a fiber optic cable) the transmission module 5730 may be a line
driver (or an electrical-to-optical converter for fiber optic
implementation).
* * * * *