U.S. patent application number 10/396251 was filed with the patent office on 2007-05-10 for apparatus, methods and articles of manufacture for processing an electromagnetic wave.
This patent application is currently assigned to M/A-Com, Eurotec BV. Invention is credited to Andrei Grebennikov, Pierce Joseph Nagle, Gerard Quilligan, Frank Sharpe.
Application Number | 20070103236 10/396251 |
Document ID | / |
Family ID | 32988763 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070103236 |
Kind Code |
A9 |
Nagle; Pierce Joseph ; et
al. |
May 10, 2007 |
APPARATUS, METHODS AND ARTICLES OF MANUFACTURE FOR PROCESSING AN
ELECTROMAGNETIC WAVE
Abstract
A method of processing an electromagnetic wave comprises
regulating at least two independently controllable current sources
with a signal determined from at least one characteristic of the
electromagnetic wave to generate a processed electromagnetic wave
from at least one of the independently controllable current
sources.
Inventors: |
Nagle; Pierce Joseph; (Cork
City, IE) ; Grebennikov; Andrei; (Cork, IE) ;
Sharpe; Frank; (Cork, IE) ; Quilligan; Gerard;
(Limerick, IE) |
Correspondence
Address: |
TYCO TECHNOLOGY RESOURCES
4550 NEW LINDEN HILL ROAD, SUITE 140
WILMINGTON
DE
19808-2952
US
|
Assignee: |
M/A-Com, Eurotec BV
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20040189395 A1 |
September 30, 2004 |
|
|
Family ID: |
32988763 |
Appl. No.: |
10/396251 |
Filed: |
March 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10294430 |
Nov 14, 2002 |
6891432 |
|
|
10396251 |
Mar 25, 2003 |
|
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Current U.S.
Class: |
330/295 |
Current CPC
Class: |
H03F 1/0266 20130101;
H03F 3/72 20130101; H03F 1/0277 20130101 |
Class at
Publication: |
330/295 |
International
Class: |
H03F 3/68 20060101
H03F003/68 |
Claims
1. A method of processing an electromagnetic wave comprising the
steps of: regulating a plurality of independently controllable
current sources by a signal so that each of the plurality of
independently controllable current sources are either off or on,
wherein each one of the independently controllable current sources
generates an output when on, with each of the outputs being
combined to provide a processed electromagnetic wave.
2. The method of claim 1, wherein said signal has a plurality of
signal components and wherein one or more of said independently
controllable independent current sources is associated with a
component in said signal.
3. The method of claim 1, wherein said signal has a plurality of
signal components and wherein each of said independently
controllable independent current sources represents a component of
said signal and provides an output current corresponding to said
component.
4. The method of claim 1, wherein said signal has a plurality of
signal components and wherein a plurality of said independently
controllable current sources together represents a component of
said signal and provides an output current corresponding to said
component.
5. The method of claim 1, wherein said independently controllable
current sources are configured so that the fewest number of said
independently controllable current sources will change when said
signal changes.
6. The method of claim 1, wherein said signal is a digital
signal.
7. The method of claim 1, wherein said signal is a binary
number.
8. The method of claim 1, wherein said signal is a seven bit binary
number.
9. The method of claim 1, wherein said independently controllable
current sources are regulated by one or more control components
configured to control the one or more of said independently
controllable current sources based upon said signal, said signal
comprising a digital word of a predetermined number of bits
comprising a "1" or "0", a "1" bit switching on said one or more
control components.
10. The method of claim 9, wherein said one or more control
component controls current to said one or more independently
controllable current sources, wherein current is input to said one
or more independently controllable current sources when said one or
more control components is switched on.
11. The method of claim 9, wherein a plurality of control
components comprise a bias control network configured to control
biasing said independently controllable current sources.
12. The method of claim 1, wherein said independently controllable
current sources comprise one or more transistors.
13. A method of claim 1, wherein each of the plurality of
independently controllable current sources are weighted a
predetermined magnitude and generate a particular output based on
the weight.
14. A method of claim 13, wherein the plurality of independently
controllable controlled current sources are switched on or off in a
sequence.
15. A method of claim 14, wherein the sequence by which the
plurality of independently controllable current sources are
switched on or off is regulated by a coded digital word.
16. An integrated circuit comprising the method of claim 15.
17. An integrated circuit of claim 16, wherein each of the
plurality of independently controllable current sources comprises
at least one of a transistor or a transistor segment.
18. An electromagnetic wave processor comprising: a plurality of
independently controllable current sources operatively connected
for receiving an input signal, with said independently controllable
current sources being on or off in response to said signal, wherein
each one of the independently controllable current sources
generates an output when on, and with each of the outputs being
combined to provide a processed electromagnetic wave.
19. The electromagnetic processor of claim 18, wherein said signal
has a plurality of signal components and wherein one or more of
said independently controllable independent current sources is
associated with a component in said signal.
20. The electromagnetic processor of claim 18, wherein said signal
has a plurality of signal components and wherein each of said
independently controllable current sources represents a component
of said signal and provides an output current corresponding to said
component.
21. The electromagnetic processor of claim 18, wherein said signal
has a plurality of signal components and wherein a plurality of
said independently controllable current sources together represents
a component of said signal and provides an output current
corresponding to said component.
22. The electromagnetic processor of claim 18, wherein said
independently controllable current sources are configured so that
the fewest number of said independently controllable current
sources will change when said signal changes.
23. The electromagnetic processor of claim 18, wherein said signal
is a digital signal.
24. The electromagnetic processor of claim 18, wherein said signal
is a binary number.
25. The electromagnetic processor of claim 18, wherein said signal
is a seven bit binary number.
26. The electromagnetic processor of claim 18, wherein said
independently controllable current sources are regulated by a
control component configured to control the one or more of said
independently controllable current sources based upon said
signal.
27. The electromagnetic processor of claim 26, wherein said control
component controls current to said one or more independently
controllable current sources.
28. The electromagnetic processor of claim 26, wherein a plurality
of control components comprise a bias control network configured to
control biasing said independently controllable current
sources.
29. The electromagnetic processor of claim 18, wherein said
independently controllable current sources comprise one or more
transistors.
30. The electromagnetic processor of claim 18, wherein each of the
plurality of independently controllable current sources are
weighted and generate a particular output based on the weight.
31. The electromagnetic processor of claim 30, wherein the
plurality of independently controllable controlled current sources
are switched on or off in a sequence.
32. The electromagnetic processor of claim 31, wherein the sequence
by which said independently controllable current sources are
switched on or off is regulated.
33. The electromagnetic processor of claim 32 comprising an
integrated circuit.
34. The electromagnetic processor of claim 33, wherein each of the
plurality of independently controllable current sources comprises
at least one of a transistor or a transistor segment.
35. An integrated circuit comprising: a plurality of segments
operatively connected, with each of said plurality of segments
being weighted and adapted to generate a desired output based on
said weight when in an on state, wherein a predefined sequence
determines which of the selected ones of said plurality of segments
are in the on state, and with the desired outputs of each of said
plurality of segments being combined to generate an output.
36. An integrated circuit of claim 35, wherein the plurality of
segments each comprises at least one of a transistor or a
transistor segment.
37. The method of claim 1, wherein said signal has a plurality of
signal components and wherein one or more of said independent
current sources is associated with an amplitude component for said
signal and one or more of said independent current sources is
associated with a phase component for said signal.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to electromagnetic
processing, and more particularly to the attenuation or
amplification of electromagnetic waves.
BACKGROUND OF THE INVENTION
[0002] The controlled attenuation or amplification of
electromagnetic waves has many uses. For example, intelligence may
be conveyed along a wave by attenuating and/or amplifying
("modifying") electromagnetic wave characteristics, such as is seen
when modulating amplitude, frequency or phase of an electrical
current or radio frequency (RF) wave to transmit data. As another
example, power may be conveyed along a wave in a controlled fashion
by attenuating and/or amplifying electromagnetic wave
characteristics, such as is seen when modulating voltage or current
in a circuit. Moreover, the uses may be combined, such as when
intelligence may be conveyed through a wave by modifying power
characteristics.
[0003] Electromagnetic wave characteristic modification may be
accomplished through digital or analog techniques. For instance, a
wave may be switched off, and thus the wave attenuated completely;
the voltage of a wave may be increased, such as by a factor of 1.5,
and thus the wave regulated; etc. Digital and analog attenuation
and/or amplification may also be combined, that is, the same wave
may be subject to various types of digital and/or analog
attenuation and/or amplification within a system in order to
accomplish desired tasks.
[0004] Electromagnetic waves have, until fairly recently, been
modified using analog techniques, and there had been no attempt to
isolate discrete wave characteristics such as current, voltage and
the like and modify those characteristics in order to modify the
wave itself. Recently, however, wave modification techniques have
become digitized, so that characteristics of the wave can be
isolated and modified directly in order to achieve a desired
result. Digitization has become desirable because it usually
provides increased precision and flexibility in wave modification
while consuming less power than previous methods.
[0005] Using digitization to process electromagnetic wave, such as
in the amplification of a wave, has provided improved linearity of
the processed wave, while at the same time also improving the
efficiency of the process by reducing power consumption.
Digitization also allows for the reduction of noise in the
processed wave through the use of digital based techniques that are
not available in analog processing systems.
[0006] Accordingly, it would be helpful to the art of
electromagnetic wave modification if apparatus, methods, and
articles of manufacture were provided that utilize digital
techniques in the processing of electromagnetic waves.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention include apparatus,
methods and articles of manufacture for generating and/or modifying
electromagnetic waves. In one embodiment, a method of processing an
electromagnetic wave comprises regulating at least two
independently controllable current sources with a signal determined
from at least one characteristic of the electromagnetic wave to
generate a processed electromagnetic wave from at least one of the
independently controllable current sources. In another embodiment,
an electromagnetic wave processor comprises a plurality of
independently controllable current sources connected to use a
signal determined from at least one characteristic of an
electromagnetic wave. The signal is input to the plurality of
independently controllable current sources to generate a processed
electromagnetic wave from at least one of the independently
controllable current sources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagram illustrating an embodiment of a wave
processor.
[0009] FIG. 2. is a diagram illustrating exemplary embodiments of a
control circuit for a wave processor
[0010] FIG. 3 is a chart illustrating states of a wave over
time.
[0011] FIGS. 4 (a)-(c) are diagrams illustrating the operation of
embodiments of a segmented wave processor.
DETAILED DESCRIPTION
[0012] Embodiments of the invention include apparatus, methods and
articles of manufacture for wave or signal processing. The term
"signal" as used herein should be broadly construed to include any
manner of conveying data from one place to another, such as, for
example, an electric current or electromagnetic field, including
without limitation, a direct current that is switched on and off or
an alternating-current or electromagnetic carrier that contains one
or more data streams. Data, for example, may be superimposed on a
carrier current or wave by means of modulation, which may be
accomplished in analog or digital form. The term "data" as used
herein should also be broadly construed to comprise any type of
intelligence or other information, such as, for example and without
limitation, audio, voice, text and/or video, etc.
[0013] In an exemplary embodiment, a wave may be divided into two
component characteristics. This wave may be an input wave, for
example, to an electromagnetic signal transmitter, receiver, or
transceiver. As shown in FIG. 1, the input wave may be divided into
a magnitude component m comprising magnitude characteristics of the
input wave over a defined period and a phase component p,
comprising phase characteristics of the input wave over the same
period.
[0014] The manner in which the input wave is divided is not
particularly limited. One exemplary manner in which this may be
accomplished is to provide input wave a to a digital signal
processor, which digitizes the wave, such as by the use of
rectangular coordinates or I,Q data. A rectangular to polar
converter then receives the I,Q data and translates it into polar
coordinates.
[0015] It should be noted that, in other embodiments, a different
digitized representation of a wave may be provided if desired.
While the invention is described herein in connection with an
embodiment using a digitized wave with polar data, those of
ordinary skill in the art will appreciate that the invention is not
limited thereto and may use any digital or analog waveform, or
combination thereof.
[0016] An output wave b is shown after processing by a preferred
embodiment. It should be noted that the time period in this and
other embodiments is as desired. For example, embodiments may
derive magnitude and phase characteristics of the wave over various
time periods in order to maximize resolution of the wave, maximize
speed of operation, etc. These time periods may be dynamically
determined as well in various embodiments so that they change
during operation. In the preferred embodiments, the division of the
input wave is synchronized, in order to maximize accuracy of output
and minimize any distortion.
[0017] FIG. 1 shows an exemplary embodiment of a wave processor.
The amplitude characteristics of the original input wave may be
modulated along path m into digital pulses comprising a digital
word quantized into bits B1 to Bn, with a Most Significant Bit
("MSB") to Least Significant Bit ("LSB"). It should be noted in
FIG. 2 that, for ease of viewing the figure, the control component
lines are consolidated into a single path m leading into control
components 22a-n. However, in the embodiment, and as further
described below, the control component lines are not consolidated
and instead feed into the control components individually. The
digital word may be as of varying lengths in various embodiments.
In general, the longer the word the greater the accuracy of
reproduction ("resolution") of the input wave. The digital word
provides instruction signals for processing of the wave, such as
for attenuation and/or amplification, in manner to be described
further below. Of course, as is described further below, in other
embodiments, a differently composed digital word may be used, as
well as other types of derivation of amplitude or other wave
characteristics.
[0018] The phase characteristic component of input wave a travels
along path p, where it is modulated onto a carrier wave, preferably
an RF signal. This wave preferably has a constant envelope, i.e.,
it has no amplitude variations, yet it has phase characteristic
information of the original input wave, and passes to wave
processor 25. The wave, which has been split among individual
driver lines, is then fed into current sources 21a-n, and will
serve to potentially drive current sources 21a-n, as is further
described below. In other embodiments, as further described below,
other sources of other wave characteristics may be used.
[0019] It should be noted that, in the present embodiment,
transistors maybe used as current sources 21a-n. Additionally, in
other embodiments, one or more transistors segmented appropriately
may be used as current sources 21a-n. The current sources 21a-n in
one preferred embodiment must not be configured to behave like
voltage sources, which will interfere with the desired current
combining of the sources.
[0020] Path m (comprised of control component lines m1-mn as
described above) terminates in control components 22a-n. In a
preferred embodiment, these are switching transistors, and are
preferably current sources, although, as further described below,
in other embodiments, other sources of other wave characteristics
may be used, as well as other regulation schemes. Control
components 22a-g are switched by bits of the digital word output
from the amplitude component and so regulated by the digital word
output from the amplitude component. If the digital control word is
a binary signal and an individual bit is "1" or "high," the
corresponding control component may be switched "on", and so
current flows from that control component to appropriate current
source 21a-n. As had been noted above, the length of the digital
word may vary, and so the number of bits, control components,
control component lines, driver lines, bias control lines, current
sources, etc. may vary accordingly in various embodiments.
Moreover, there does not have to be a one to one correspondence
among digital word resolution, components, lines and current
sources in various embodiments.
[0021] Current sources 21a-n receive current from a control
component if the control component is on, and thus each current
source is regulated according to that component. In the especially
preferred embodiments, an appropriate control component provides
bias current to the current sources, as is described further below,
and so the control component may be referred to as a bias control
circuit, and a number of them as a bias network. In some
embodiments, it may be desired to statically or dynamically
allocate one or more bias control circuits to one or more current
sources using a switching network if desired. For example, the
circuitry of control components 22a-n may be configured to control
a particular one or more of transistors of segments 21a-n.
[0022] An examples of an embodiment of a control circuit is
illustrated in FIG. 2. It will be appreciated that while particular
circuits and components are shown herein for purposes of
explanation, the invention is not limited thereto. Different or
additional components may be added and components may also be
deleted.
[0023] FIG. 2 illustrates a bias circuit that incorporates one
reference transistor. In this example, output transistor Q.sub.o
may represent one of transistor segments 21a-n, which, when
switched on, contributes a predetermined amount of output current
(RF.sub.out) to the output of wave processor 25. A plurality of
control circuits and output transistors may be provided to
contribute the aforementioned current outputs. In this embodiment,
a biasing voltage for transistor Q.sub.1. is varied in accordance
with a respective control bit of the digital control word. As
control voltage V.sub.con, is varied, varying current i flows
through resistor R.sub.1 as determined by the gain G of transistor
Q.sub.1. Current i thus controls the flow of current through
transistor Q.sub.2.
[0024] The current from transistor Q.sub.2is used to control the
predetermined current to be outputted from transistor Q.sub.o. The
phase portion of the input wave p is inputted at RF.sub.in, where
it may pass components such as capacitor C.sub.1, which acts to
block DC components from the signal. When the control bit is "on",
current flows though the circuit and output transistor Q.sub.o
contributes its output current to the output of wave processor 25.
In this example, output transistor Q.sub.o has a gain that is ten
times that of transistor Q.sub.1, however, as should be understood,
other values may be used as well. Output transistor Q.sub.o is
biased by voltage V.sub.cc. The current outputted from the
collector of output transistor Q.sub.o is filtered by inductor
L.sub.1 and capacitor C.sub.2, which act to provide filtering of
the output signal RF.sub.out.
[0025] Each of the outputs from each of the output transistor
segments that are switched "on" in this manner contribute their
respective currents to the output of wave processor 25, (while the
transistors that are switched "off" do not), thus processing the
input wave to form the output wave.
[0026] The digital control word of amplitude component m may be
configured or coded in any desired manner for operating the
above-described segments in any desired manner. By way of
illustration, in one preferred embodiment the digital control word
contains seven bits to represent a wave characteristic of the input
wave a, such as amplitude. Each configuration of these seven bits
represents a different input state to wave processor 25, where each
input state may correspond to a digital representation of the wave
characteristic.
[0027] This is further illustrated in FIG. 3 for this example. If
the control bits are configured in a binary system, then seven
control bits may be configured in 2.sup.7 or 128 different ways,
allowing for 128 different input states to wave processor 25. Each
of these 128 states may represent, for example, a discrete
amplitude level or range of an input wave a. As can be seen from
FIG. 3, the greater the number of control bits, the greater the
number of input states, and hence the greater the resolution of the
wave processor.
[0028] The coding system that may be employed in accordance with
the embodiments disclosed herein is not limited and may include any
digital representation of a characteristic of an input wave a that
may be used to control wave processor 25 in any manner. In an
especially preferred embodiment, the digital representation is of
the amplitude of the input wave and comprises a binary digital word
having seven bits, where each bit, from the most significant bit
("MSB") to the least significant bit ("LSB") is used to control a
designated segment or segments of wave processor 25 to generate an
output current.
[0029] In this preferred embodiment, each bit(1,2,4,8,16,32, and
64) represents the number 2 raised to a power (0,1,2,3,4,5,6) and
one or more of these bits are combined to designate a number
corresponding to the wave characteristic of input wave a, such as
amplitude. If a bit is switched high or "on" ("1"), it is counted;
if it is switched low or "off" ("0"), it is not counted. Thus, for
example, if the digital word represents the number "63", then the
bit representing the number 64 would be off (or "0") and the bits
for 32, 16, 8, 4, 2, and 1 would be on ("0111111"). Adding the
designated bits together equals 63 (32+16+8+4+2+1=63). If the
digital word represents the number "64", then only the bit
representing the number 64 would be on, and the others would be off
("1000000").
[0030] Each segment of wave processor 25 receives current from one
or more of the control components based upon these control bits and
may be biased to serve as a potential current source. The segment
may or may not act as a current source, because it is regulated via
the appropriate digital word value regulating the control
component, and activation of a segment is dependant upon the value
of the appropriate bit from the digital representation of the
amplitude component, and concomitant regulation of the appropriate
control component.
[0031] In one embodiment, the segments are varied in size such that
the first segment a is twice the size of the next segment b, which
in turn is twice the size of the next segment c, and so on until
reaching the final segment n. The largest segment a is controlled
by the MSB of the amplitude word, the next bit of the word to the
next largest segment, etc., until the LSB, which is sent to the
smallest segment. Alternatively, the segments may be sized and
grouped so that a particular group of segments may represent a
particular bit of the control word. Of course, as noted above,
other embodiments may have a different pattern of matching bit to
segment. In other embodiments, other wave characteristics may be
fed to another source of wave characteristics and so regulate that
source.
[0032] As the digital control word changes over time, one or more
of segments may become a current source, contributing a
corresponding amount of current to the output of wave processor 25.
The current output from each segment is thus combined at the output
of wave processor 25 to drive load R.sub.L. The current is
outputted from wave processor 25 in relation to the input state of
the wave processor as designated by the digital control. The input
state changes as the digital control word changes, which, in turn,
changes the segments that contribute current to the output, thus
processing the input wave in the determined manner, e.g.,
amplification.
[0033] The foregoing is further illustrated by FIGS. 4(a)-(c),
which comprise exemplary IC layouts. In these examples, each
segment, or group of segments, may represent a number corresponding
to an input state. For example, as shown in FIG. 4(a), seven
segments may be used to each represent a number corresponding to
the significance of one of the seven bits of the digital control
word, i.e., 64, 32, 16, 8, 4, 2, and 1. Each segment may be sized
or weighted in this example to contribute a proportionate amount of
current to the output when acting as a current source. For example,
a segment representing the number "64" may contribute twice as much
current as a segment representing the number "32". When the digital
word inputted to the wave processor designates a particular input
state, the control components switch on segments that combine to
designate that state. For the example shown in FIG. 4(a), if the
input state is "63", then segments 1, 2, 4, 8, 16, and 32 are
turned on to contribute current and the segment representing 64 is
turned off. When the digital word, and thus the input state,
changes (for example, to "64"), then the control components switch
off segments 1, 2, 4, 8, 16, and 32, and switch on the segment
representing 64.
[0034] Alternatively, as shown in FIG. 4(b), some of the segments
may be evenly weighted, but more than one segment may be grouped to
designate a number for the input state. In this example, eleven
segments may be used to represent the seven bits of the digital
control word. Seven of the segments each represent the number 16,
while the remaining segments represent the numbers 8, 4, 2, and 1.
Four of these segments may thus be combined to represent the number
64, two may be combined to represent the number 32, etc.
[0035] Weighting the segments in this manner allows for the
segments to be combined in a variety of ways to achieve the desired
state. Thus, as shown in FIG. 4(c), in switching from state "63" to
state "64", the four smaller segments (8, 4, 2, 1) may be switched
off and only one 16 segment need be switched on to achieve the
desired change in state. The use of smaller segments is
advantageous, for example, when switching transistors, because it
may reduce switching noise and glitching that may occur in the
processed signal due to inherently larger capacitance of the larger
transistors.
[0036] In addition, the sequence by which segments are switched off
or on in order to achieve a particular change in state may be
regulated where desired. For example, in some embodiments, a
particular sequence may be selected based upon certain factors,
such as environmental factors, including, for instance, temperature
gradients and/or other non-linearities in a fabricated chip, etc.
Moreover, a particular sequence may be chosen at any desired time
period, and a particular sequence may be further re-sequenced one
or more times at any later point where ever that may be deemed
appropriate. One exemplary sequence is illustrated in FIG. 4(c). In
this embodiment, the seven segments representing the number 16 are
labeled, beginning with the segment on the upper left hand comer
and moving clockwise, as 0, 1, 4, 5, 6, 3, 2. As shown in FIG.
4(c), the order of the sequence as to when each of these seven
segments are switched on comprises segment 3 first, segment 4
second, segment 5 third, segment 6 fourth, segment 2 fifth, segment
1 sixth and segment 0 seventh. Of course, it should be understood
that any other particular sequence may be utilized where
desired.
[0037] Returning now to the embodiment of FIG. 1, each of the
components serves as a potential current source, and is capable of
generating a current, which is output to current source lines 21a-n
respectively. It should be noted that the current sources are not
an amplifier or amplifiers, in the preferred embodiments, rather
the plurality of current sources function as an amplifier, as is
described herein. Indeed, amplification and/or attenuation may be
considered in the preferred embodiments as functions of those
embodiments, and so may an amplifier and/or attenuator be
considered to be an electrical component or system that amplifies
and/or attenuates.
[0038] The combined current, i.e. the sum of any current output
from current sources 21a-n, is the current sources output. Thus, an
embodiment may act as an attenuator and/or amplifier. In preferred
embodiments, no further circuitry or components are necessary
between current sources to combine current from each current source
and so provide a useful output current. Therefore, the combined
current, which is output on line 26, may be used as desired, e.g.,
as an amplifier, as an attentuator, to drive a load, etc.
[0039] It should be noted that, in the invention, the current
sources are biased non-linearly. Thus, any current source operates
efficiently. In the preferred embodiments, therefore, power
consumption is reduced. Additionally, as a result of current source
regulation according to signal characteristics, as had been
described above, the resultant output signal has a relatively
accurate linearity and proportionality with the input signal. Thus,
an amplifier may be provided in the preferred embodiments with the
relative precision of linear operation combined with the relative
efficiency and power consumption of non-linear operation.
[0040] For example, returning to the embodiment of FIG. 1, if one
of current sources 21a-n is switched on, it will act as a
non-linear current source with attendant relative efficiency. If
the current source is off, the source consumes little or no power.
Linear characteristics are seen as well because each current source
that is on provides current contribution in similar proportions to
the amplitude characteristic of the input signal, and so a
relatively precise reproduction of the input signal is
provided.
[0041] The current sources 21a-n may comprise, in the preferred
embodiment of FIG. 1, one or more HBT transistors. Other
transistors may be used as well, such as FETs, etc., as well as
other current sources. Other components may be interposed as well,
e.g., a variable gain amplifier or attenuator to reduce the drive
current to the transistor segments, non-linear components along the
amplitude path, etc.
[0042] The use of the preferred embodiments may provide a
capability for wide band amplitude modification in an associated
transmitter because it makes possible linear amplification and/or
attenuation across a relatively large frequency spectrum, due to
the relatively low input capacitance. Thus, embodiments may be used
for cellular and other transmitters, as is described further
herein.
[0043] Advantageously, embodiments of the present invention may
improve efficiency over conventional power amplification, because
linearity of the transmission is not dependent on the linearity of
the amplifier, but instead depends only on how linearly the
currents add to the load. Accordingly, each current source can be
biased as a non-linear current source, such as Class B or C, to
maximize the efficiency. Efficiency may further be improved because
there is little or no quiescent current draw for disabled current
sources.
[0044] In the illustrated embodiments, power control may readily be
achieved because the output current is dependent primarily on the
signal drive level. Increasing or decreasing the signal drive
level, for example, with a variable gain amplifier or attenuator,
causes a corresponding increase or decrease in the output current.
In addition, an increase or decrease of the bias to the drive
controller, also causes a respective increase or decrease in the
output current.
[0045] As should be understood, any suitable types of current
sources, for example, other transistor segments and/or formats, as
well as other devices or methods, may be used with any of the
embodiments of the present invention where desired.
[0046] In, embodiments fabricated as a single integrated circuit,
weighting may be achieved by providing segments having different
semiconductor areas. For example, when the area of a segment is
reduced in size by half, the current supplied by the segment to the
load is also reduced in half. This is because the smaller segment
has half the current density of the larger segment.
[0047] Amplifiers according to embodiments of the invention can
provide a direct digital interface for baseband DSP functions. The
amplifiers also may be dynamically programmed to accommodate
multiple modulation formats and wireless network standards. An
advantage is that cost and size of devices using an amplifier based
on this aspect of the invention can be reduced. Furthermore, the
output current combines into the load to develop a voltage that can
be an analog representation of the amplitude characteristic, so
that the amplifier also performs a digital-to-analog
conversion.
[0048] Various types of system architectures may be utilized for
constructing the embodiments of the present invention. One of
ordinary skill in the art will accordingly appreciate that
embodiments of the invention or various components and/or features
thereof may be entirely comprised of hardware, software or may be a
combination of software and hardware. The embodiments or various
components may also be provided on a semiconductor device where
desired, such as an integrated circuit or an application-specific
integrated circuit composition; some examples include silicon (Si),
silicon germanium (SiGe) or gallium arsenide (GaAs) substrates.
[0049] Various embodiments may modify various parameters without
departing from the spirit and scope of the present invention. For
example, the length of the digital word may be longer or shorter in
various embodiments, which may provide a more or less precise
digitization of the wave. As other examples, as was described
further above, the number of bits, control components, control
component lines, driver lines, bias control lines, current sources,
etc., may all be varied as desired.
[0050] While the invention has been described by illustrative
embodiments, additional advantages and modifications will occur to
those skilled in the art. Therefore, the invention in its broader
aspects is not limited to specific details shown and described
herein. Modifications, for example, may be made without departing
from the spirit and scope of the invention. In addition, preferred
embodiments may include amplifiers that are specialized for
particular input signals, carrier waves and output signals e.g.
embodiments may be used in various RF, microprocessor,
microcontroller and/or computer devices, e.g. cell phones, such as
CDMA, CDMA2000, W-CDMA, GSM, TDMA, as well as other wired and
wireless devices, e.g. Bluetooth, 802.11a, -b, -g, radar, 1xRTT,
two-way radios, GPRS, computers and computer communication devices,
PDA's and other handheld devices, etc. Accordingly, it is intended
that the invention not be limited to the specific illustrative
embodiments, but be interpreted within the full spirit and scope of
the appended claims and their equivalents.
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