U.S. patent application number 12/474270 was filed with the patent office on 2010-07-15 for power amplifier architectures.
This patent application is currently assigned to Rayspan Corporation. Invention is credited to Maha Achour, Raul Alidio, Alexandre Dupuy, Ajay Gummalla, Cheng-Jung Lee, Can Zheng.
Application Number | 20100176880 12/474270 |
Document ID | / |
Family ID | 41379050 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100176880 |
Kind Code |
A2 |
Dupuy; Alexandre ; et
al. |
July 15, 2010 |
POWER AMPLIFIER ARCHITECTURES
Abstract
Implementations and examples of power amplifier devices, systems
and techniques for amplifying RF signals, including power amplifier
systems based on Composite Right and Left Handed (CRLH)
metamaterial (MTM) structures.
Inventors: |
Dupuy; Alexandre; (San
Diego, CA) ; Alidio; Raul; (Carlsbad, CA) ;
Gummalla; Ajay; (San Diego, CA) ; Achour; Maha;
(San Diego, CA) ; Lee; Cheng-Jung; (San Diego,
CA) ; Zheng; Can; (San Diego, CA) |
Correspondence
Address: |
Rayspan Corporation
11975 El Camino Real
Suite 301
San Diego
CA
92130
UNITED STATES
858-259-9596
akiko@rayspan.com
|
Assignee: |
Rayspan Corporation
11975 El Camino Real Suite 301
San Diego
CA
92130
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20090295473 A1 |
December 3, 2009 |
|
|
Family ID: |
41379050 |
Appl. No.: |
12/474270 |
Filed: |
May 28, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61/056,826 |
May 28, 2008 |
|
|
|
Current U.S.
Class: |
330/124R |
Current CPC
Class: |
H03F 2200/102 20130101;
H03F 2200/331 20130101; H03F 3/245 20130101; H03F 2200/543
20130101; H03F 2200/423 20130101; H03F 1/56 20130101; H03F 2200/255
20130101; H03F 3/602 20130101; H03F 2200/171 20130101; H03F 1/0222
20130101; H03F 2200/351 20130101; H03F 3/195 20130101; H03F 1/0288
20130101; H03F 2200/387 20130101; H03F 1/0294 20130101 |
Class at
Publication: |
330/124.00R |
International
Class: |
H03F 3/68 20060101
H03F003/68 |
Claims
1. A power amplifier system for amplifying an RF signal,
comprising: an input port that receives an input RF signal; a power
divider including an input transmission line coupled to the input
port to receive the input RF signal and output branch transmission
lines that are coupled to the input transmission line to split the
received input RF signal into branch RF signals that are
respectively carried by the output branch transmission lines; power
amplifiers that are coupled to the output branch transmission lines
of the power divider, respectively, each power amplifier receiving
and amplifying a respective branch RF signal to produce an
amplified branch RF signal; and a power combiner including input
branch transmission lines that are respectively coupled to the
power amplifiers to receive amplified branch RF signals produced by
the power amplifiers, and an output transmission line coupled to
the input branch transmission lines to combine the received
amplified branch RF signals into a combined output RF signal,
wherein at least one of the power divider and the power combiner
includes a Composite Right and Left Handed (CRLH) Metamaterial
(MTM) structure.
2. The power amplifier system of claim 1, wherein: the input
transmission line and the output branch transmission lines of the
power divider are CRLH MTM transmission lines and at least two of
the output branch transmission lines are structured to have
different impedances.
3. The power amplifier system of claim 1, wherein: the input
transmission line and the output branch transmission lines of the
power divider are CRLH MTM transmission lines and the output branch
transmission lines are structured to have substantially equal
impedances.
4. The power amplifier system of claim 1, wherein: the input
transmission line and the output branch transmission lines of the
power divider are CRLH MTM transmission lines and structured to
render branch RF signals in at least two output branch transmission
lines to have different power levels.
5. The power amplifier system of claim 1, wherein: the input
transmission line and the output branch transmission lines of the
power divider are CRLH MTM transmission lines and structured to
render the branch RF signals in all of the output branch
transmission lines substantially equal in power.
6. The power amplifier system of claim 1, wherein: the input
transmission line of the power divider is a CRLH MTM transmission
line of an electrical length having a zero phase delay or a phase
delay of .+-.m180.degree. where m is a positive integer, and each
output branch transmission line of the power divider is a CRLH MTM
transmission line of an electrical length having a phase delay of
.+-.n90.degree. where n is a positive odd integer.
7. The power amplifier system of claim 1, wherein: the input
transmission line of the power divider is a CRLH MTM transmission
line of an electrical length having a phase delay of
.+-.m90.degree. where m is a positive odd integer, and each output
branch transmission line of the power divider is a CRLH MTM
transmission line of an electrical length having a zero phase delay
or a phase delay of .+-.n180.degree. where n is a positive
integer.
8. The power amplifier system of claim 1, wherein: the input
transmission line and the output branch transmission lines of the
power divider are CRLH MTM transmission lines that have at least
two different resonances at two RF frequencies, and the power
amplifiers and the power combiner are structured to operate at the
two RF frequencies.
9. The power amplifier system of claim 1, wherein: the input branch
transmission lines and the output transmission line of the power
combiner are CRLH MTM transmission lines and at least two of the
input branch transmission lines are structured to have different
impedances.
10. The power amplifier system of claim 1, wherein: the input
branch transmission lines and the output branch transmission line
of the power combiner are CRLH MTM transmission lines and the input
branch transmission lines are structured to have substantially
equal impedances.
11. The power amplifier system of claim 1, wherein: each input
branch transmission line of the power combiner is a CRLH MTM
transmission line of an electrical length having a zero phase delay
or a phase delay of .+-.m180.degree. where m is a positive integer,
and the output transmission line of the power combiner is a CRLH
MTM transmission line of an electrical length having a phase delay
of .+-.n90.degree. where n is a positive odd integer.
12. The power amplifier system of claim 1, wherein: each input
branch transmission line of the power combiner is a CRLH MTM
transmission line of an electrical length having a phase delay of
.+-.m90.degree. where m is a positive odd integer, and the output
transmission line of the power combiner is a CRLH MTM transmission
line of an electrical length having a zero phase delay or a phase
delay of .+-.n180.degree. where n is a positive integer.
13. The power amplifier system of claim 1, wherein: the input
branch transmission lines and the output branch transmission line
of the power combiner are CRLH MTM transmission lines that have at
least two different resonances at two different RF frequencies, and
the power amplifiers and the power divider are structured to
operate at the two different RF frequencies.
14. The power amplifier system of claim 1, wherein: the power
divider is a Wilkinson power splitter formed by Composite Right and
Left Handed (CRLH) Metamaterial (MTM) transmission lines.
15. The power amplifier system of claim 14, wherein: the Wilkinson
power splitter includes: a first CRLH MTM transmission line as the
input transmission line; a second CRLH MTM transmission line as one
of the branch output transmission lines having a first terminal
coupled to the first CRLH MTM transmission line and a second
terminal; a third CRLH MTM transmission line as another one of the
branch output transmission lines having a first terminal coupled to
the first CRLH MTM transmission line and a second terminal; a
resistor having a first terminal coupled to the second terminal of
the second CRLH MTM transmission line and a second terminal coupled
to the second terminal of the third CRLH MTM transmission line; a
fourth CRLH MTM transmission line coupled to the second terminal of
the third CRLH MTM transmission line; and a fifth CRLH MTM
transmission line coupled to the second terminal of the third CRLH
MTM transmission line.
16. The power amplifier system of claim 1, wherein: the power
combiner is a Wilkinson power combiner formed by Composite Right
and Left Handed (CRLH) Metamaterial (MTM) transmission lines.
17. The power amplifier system of claim 16, wherein: the Wilkinson
power combiner includes: a first CRLH MTM transmission line having
a first terminal coupled to a first power amplifier to receive a
first amplified RF signal and a second terminal to output the first
amplified RF signal; a second CRLH MTM transmission line having a
first terminal coupled to a second power amplifier to receive a
second amplified RF signal and a second terminal to output the
second amplified RF signal; a resistor having a first terminal
coupled to the second terminal of the first CRLH MTM transmission
line and a second terminal coupled to the second terminal of the
second CRLH MTM transmission line; a third CRLH MTM transmission
line coupled to the second terminal of the first CRLH MTM
transmission line as one of the input branch transmission lines; a
fourth CRLH MTM transmission line coupled to the second terminal of
the fourth CRLH MTM transmission line as another one of the input
branch transmission lines; and a fifth CRLH MTM transmission line
forming the output transmission line and coupled to the third and
fourth CRLH MTM transmission lines.
18. The power amplifier system of claim 1, wherein: at least one of
the power divider and the power combiner is made of right handed
components and is free of a Composite Right and Left Handed (CRLH)
Metamaterial (MTM) structure.
19. The power amplifier system of claim 1, wherein: the power
amplifiers are power amplifiers having non-linear components to
provide linear amplification.
20. The power amplifier system of claim 1, wherein: each of the
power amplifiers includes non-linear components to provide linear
amplification and a Composite Right and Left Handed (CRLH)
Metamaterial (MTM) structure.
21. A device based on a Composite Right and Left Handed (CRLH)
Metamaterial (MTM) structure, comprising: a first transmission line
including a Composite Right and Left Handed (CRLH) Metamaterial
(MTM) structure, a first terminal that is terminated at a first
impedance and a second terminal; a plurality of second transmission
lines of CRLH MTM structures that are coupled to the second
terminal of the first transmission line to either split an input RF
signal received from the second terminal of the first transmission
line into a plurality of output RF signals in the second
transmission lines, respectively, or combine a plurality of input
RF signals in the second transmission lines into an output RF
signal at the second terminal of the first transmission line, each
second transmission line having a first terminal that is coupled to
the second terminal of the first transmission line and a second
terminal that is terminated at a respective second impedance,
wherein the first transmission line and the second transmission
lines are structured to provide impedance match between the first
impedance at the first terminal of the first transmission line and
a respective second impedance of each of the second transmission
lines, and wherein the first transmission line and the second
transmission lines are structured to be in a first configuration
where the first transmission line is a CRLH MTM transmission line
of an electrical length having a phase delay of .+-.m90.degree.
where m is a positive odd integer, and each of the second
transmission lines is a CRLH MTM transmission line of an electrical
length having a zero phase delay or a phase delay of
.+-.n180.degree. where n is a positive integer, or in a second
configuration where the first transmission line is a CRLH MTM
transmission line of an electrical length having a zero phase delay
or a phase delay of .+-.m180.degree. where m is a positive integer
and each of the second transmission lines is a CRLH MTM
transmission line having a phase delay of .+-.n90.degree. where n
is a positive odd integer.
22. The device as in claim 21, wherein: the second transmission
lines have different impedances.
23. The device as in claim 21, wherein: the second transmission
lines have substantially equal impedances.
24. The device as in claim 21, wherein: the first transmission line
has resonances at two or more different RF frequencies; and each
second transmission line is structured to have resonances at the
two or more different RF frequencies of the first transmission
line.
25. A power amplifier system, comprising: an RF input port for
receiving an input RF signal; an envelope detector coupled to the
RF input port to receive a first portion of the input RF signal to
extract information on an amplitude envelope of the input RF signal
to produce an envelope signal; a sigma-delta modulator coupled to
the envelope detector to convert the envelope signal into a first
signal; a limiter circuit coupled to the RF input port to receive a
second portion of the input RF signal to eliminate amplitude
modulation components of the input RF signal to produce a second
signal that retains phase of the input RF signal; a time delay
circuit coupled to the limiter circuit to cause a delay in the
second amplifier input signal to synchronize with the first signal;
a modulator coupled to receive the first and second signals and to
combine the received first and second signals into a third signal;
and a power amplifier coupled to the modulator to receive and
amplify the third signal into an output RF signal which is
proportional to the input RF signal, wherein the power amplifier is
a Composite Right and Left Handed (CRLH) Metamaterial (MTM)
structure power amplifier.
26. A power amplifier system, comprising: an RF input port for
receiving an input RF signal; an envelope detector coupled to the
RF input port to receive a first portion of the input RF signal to
extract information on an amplitude envelope of the input RF signal
to produce an envelope signal; a sigma-delta modulator coupled to
the envelope detector to convert the envelope signal into a first
signal; a limiter circuit coupled to the RF input port to receive a
second portion of the input RF signal to eliminate amplitude
modulation components of the input RF signal to produce a second
signal that retains phase of the input RF signal; a time delay
circuit coupled to the limiter circuit to cause a delay in the
second amplifier input signal to synchronize with the first signal;
a power amplifier coupled to receive the first and second signals
to produce an output RF signal which is proportional to the input
RF signal; and a filter coupled to the power amplifier to filter
the output RF signal and having a Composite Right and Left Handed
(CRLH) Metamaterial (MTM) structure.
27. The system as in claim 26, wherein: the power amplifier is a
Composite Right and Left Handed (CRLH) Metamaterial (MTM) power
amplifier.
28. A power amplifier system for amplifying an RF signal,
comprising: an input port that receives an input RF signal; a
plurality of transmission lines based on Composite Right and Left
Handed (CRLH) Metamaterial (MTM) structures and connected in series
to receive the input RF signal from the input port, each
transmission line having a CRLH MTM structure to produce, at an
operating frequency, a zero phase delay or a phase delay of
n360.degree. where n is a positive or negative integer and
including a branch output port that splits a portion of the RF
signal as a respective branch RF signal for the transmission line
and different transmission lines producing different respective
branch RF signals; a plurality of power amplifiers that are coupled
to the branch output ports of the transmission lines, respectively,
each power amplifier receiving and amplifying a respective branch
RF signal to produce an amplified branch RF signal; and a power
combiner based on a CRLH MTM structure and coupled to receive the
amplified branch RF signals from the power amplifiers and to
combine the received amplified branch RF signals into a combined
output RF signal.
29. The system as in claim 28, wherein: the transmission lines
based on CRLH MTM structures have at least a first resonance and a
second resonances in frequency, wherein each of the transmission
lines is structured to produce a first phase delay at the first
resonance and a second phase delay at the second resonance, and the
first and second phase delays are two different values selected
values from zero and n360.degree. where n is a positive or negative
integer.
30. The system as in claim 28, wherein: the power combiner includes
input CRLH MTM transmission lines that are respectively coupled to
the power amplifiers to receive amplified branch RF signals
produced by the power amplifiers, and a CRLH MTM output
transmission line coupled to the input CRLH MTM transmission lines
to combine the received amplified branch RF signals into the
combined output RF signal.
31. The system as in claim 28, wherein: the power divider is a
Wilkinson power splitter formed by Composite Right and Left Handed
(CRLH) Metamaterial (MTM) transmission lines to receive amplified
branch RF signals produced by the power amplifiers and to combine
the received amplified branch RF signals into the combined output
RF signal.
32. A power amplifier system for amplifying an RF signal,
comprising: a Zero.sup.th order resonator power divider having a
Composite Right and Left Handed (CRLH) Metamaterial (MTM) structure
that receives an input RF signal and splits the received input RF
signal into branch RF signals in phase with respective to one
another; a plurality of transistors coupled to the Zero.sup.th
order resonator power divider to receive the branch RF signals,
respectively, and to amplify the received branch RF signals; and a
Zero.sup.th order resonating antenna based on a CRLH MTM structure
and coupled to transistors to receive amplified branch RF
signals.
33. A power amplifier system, comprising: an RF input for receiving
an input RF signal; a first quadrature coupler based on a Composite
Right and Left Handed (CRLH) Metamaterial (MTM) structure and
having a first input port coupled to the RF input to receive the
input RF signal, a second input port that is terminated, a first
output port and a second output port, the first quadrature coupler
splitting the input RF signal into a first RF signal at the first
output port and a second RF signal at the second output port that
has a phase shift of 90 degrees with respect to the first RF
signal; a first power amplifier coupled to the first output port to
receive and amplify the first RF signal; a second power amplifier
coupled to the second output port to receive and amplify the second
RF signal; and a second quadrature coupler based on a CRLH MTM
structure and having a first input port coupled to receive the
amplified first RF signal from the first power amplifier, a second
input port coupled to receive the amplified second RF signal from
the second power amplifier, a first output port that is terminated
and a second output to produce an RF output signal, the second
quadrature coupler combining signals received at the first and
second input ports with a 90-degree phase shift to produce the RF
output signal.
34. The power amplifier system as in claim 33, wherein: one of the
first and second quadrature couplers is a CRLH MTM branch line
coupler formed by four CRLH MTM transmission lines.
35. The power amplifier system as in claim 34, wherein: the first
and second quadrature couplers have CRLH MTM structures with
resonances at two or more RF frequencies.
36. The power amplifier system as in claim 33, wherein: one of the
first and second quadrature couplers is a planar forward-wave
directional coupler based on a CRLH MTM structure that unit cells
formed in common metallization layers at different horizontal
locations in a plane of a substrate in which the unit cells are
formed.
37. The power amplifier system as in claim 33, wherein: one of the
first and second quadrature couplers is a vertical forward-wave
directional coupler based on a CRLH MTM structure that unit cells
formed in different metallization layers along a vertical direction
perpendicular to a place of a substrate in which the unit cells are
formed.
Description
PRIORITY CLAIM AND RELATED APPLICATION
[0001] This patent document claims the benefits of U.S. Provisional
Patent Application Ser. No. 61/056,826 entitled "POWER AMPLIFIER
ARCHITECTURES FOR HIGH EFFICIENCY AND HIGH LINEARITY USING
METAMATERIAL STRUCTURES" and filed on May 28, 2008. The disclosure
of the above provisional application is incorporated by reference
as part of the specification of this document.
BACKGROUND
[0002] This patent document relates to power amplifier devices,
systems and techniques for amplifying RF signals.
[0003] Power amplifiers (PAs) are devices that amplify power of RF
signals by converting DC power into RF power and are used in
various RF devices and systems. Many power amplifiers used in a
transceiver system tend to occupy a large chip or board area,
require high DC power, and need to dissipate heat generated during
operation. Good efficiency and linearity of the PAs are demanded in
wireless communications and other RF applications. Many wireless
standards targeting high communication throughput utilize complex
modulation schemes to generate an RF signal with both amplitude and
phase components. Such schemes may impose stringent linearity
requirements on the PAs in the system. In addition, the PAs are
required to operate at adequate levels of efficiencies to minimize
battery power consumption and heat dissipation.
SUMMARY
[0004] Implementations and examples of power amplifier devices,
systems and techniques for amplifying RF signals are provided,
including power amplifier systems based on Composite Right and Left
Handed (CRLH) metamaterial (MTM) structures.
[0005] In one aspect, a power amplifier system for amplifying an RF
signal is provided to include an input port that receives an input
RF signal and a power divider including an input transmission line
coupled to the input port to receive the input RF signal and output
branch transmission lines that are coupled to the input
transmission line to split the received input RF signal into branch
RF signals that are respectively carried by the output branch
transmission lines. This system includes power amplifiers that are
coupled to the output branch transmission lines of the power
divider, respectively and each power amplifier receives and
amplifies a respective branch RF signal to produce an amplified
branch RF signal. A power combiner is provided to include input
branch transmission lines that are respectively coupled to the
power amplifiers to receive amplified branch RF signals produced by
the power amplifiers, and an output transmission line coupled to
the input branch transmission lines to combine the received
amplified branch RF signals into a combined output RF signal. At
least one of the power divider and the power combiner includes a
Composite Right and Left Handed (CRLH) Metamaterial (MTM)
structure.
[0006] In another aspect, a device based on a Composite Right and
Left Handed (CRLH) Metamaterial (MTM) structure includes a first
transmission line including a Composite Right and Left Handed
(CRLH) Metamaterial (MTM) structure, a first terminal that is
terminated at a first impedance and a second terminal; and second
transmission lines of CRLH MTM structures that are coupled to the
second terminal of the first transmission line to either split an
input RF signal received from the second terminal of the first
transmission line into output RF signals in the second transmission
lines, respectively, or combine input RF signals in the second
transmission lines into an output RF signal at the second terminal
of the first transmission line. Each second transmission line has a
first terminal that is coupled to the second terminal of the first
transmission line and a second terminal that is terminated at a
respective second impedance. The first transmission line and the
second transmission lines are structured to provide impedance match
between the first impedance at the first terminal of the first
transmission line and a respective second impedance of each of the
second transmission lines. In this device, the first transmission
line and the second transmission lines are structured to be a first
configuration or a second configuration. In the first
configuration, the first transmission line is a CRLH MTM
transmission line of an electrical length having a phase delay of
.+-.m90.degree. where m is a positive odd integer, and each of the
second transmission lines is a CRLH MTM transmission line of an
electrical length having a zero phase delay or a phase delay of
.+-.n180.degree. where n is a positive integer. In the second
configuration, the first transmission line is a CRLH MTM
transmission line of an electrical length having a zero phase delay
or a phase delay of .+-.m180.degree. where m is a positive integer
and each of the second transmission lines is a CRLH MTM
transmission line having a phase delay of .+-.n90.degree. where n
is a positive odd integer.
[0007] In another aspect, a power amplifier system includes an RF
input port for receiving an input RF signal; an envelope detector
coupled to the RF input port to receive a first portion of the
input RF signal to extract information on an amplitude envelope of
the input RF signal to produce an envelope signal; a sigma-delta
modulator coupled to the envelope detector to convert the envelope
signal into a first signal; a limiter circuit coupled to the RF
input port to receive a second portion of the input RF signal to
eliminate amplitude modulation components of the input RF signal to
produce a second signal that retains phase of the input RF signal;
a time delay circuit coupled to the limiter circuit to cause a
delay in the second amplifier input signal to synchronize with the
first signal; a modulator coupled to receive the first and second
signals and to combine the received first and second signals into a
third signal; and a power amplifier coupled to the modulator to
receive and amplify the third signal into an output RF signal which
is proportional to the input RF signal. The power amplifier is a
Composite Right and Left Handed (CRLH) Metamaterial (MTM) structure
power amplifier.
[0008] In another aspect, a power amplifier system is provided to
include an RF input port for receiving an input RF signal; an
envelope detector coupled to the RF input port to receive a first
portion of the input RF signal to extract information on an
amplitude envelope of the input RF signal to produce an envelope
signal; a sigma-delta modulator coupled to the envelope detector to
convert the envelope signal into a first signal; a limiter circuit
coupled to the RF input port to receive a second portion of the
input RF signal to eliminate amplitude modulation components of the
input RF signal to produce a second signal that retains phase of
the input RF signal; a time delay circuit coupled to the limiter
circuit to cause a delay in the second amplifier input signal to
synchronize with the first signal; a power amplifier coupled to
receive the first and second signals to produce an output RF signal
which is proportional to the input RF signal; and a filter coupled
to the power amplifier to filter the output RF signal and having a
Composite Right and Left Handed (CRLH) Metamaterial (MTM)
structure.
[0009] In another aspect, a power amplifier system for amplifying
an RF signal includes an input port that receives an input RF
signal; and transmission lines based on Composite Right and Left
Handed (CRLH) Metamaterial (MTM) structures and connected in series
to receive the input RF signal from the input port. Each
transmission line has a CRLH MTM structure to produce, at an
operating frequency, a zero phase delay or a phase delay of n360o
where n is a positive or negative integer and includes a branch
output port that splits a portion of the RF signal as a respective
branch RF signal for the transmission line and different
transmission lines producing different respective branch RF
signals. This system includes power amplifiers that are coupled to
the branch output ports of the transmission lines, respectively,
and each power amplifier receives and amplifies a respective branch
RF signal to produce an amplified branch RF signal. A power
combiner based on a CRLH MTM structure is coupled to receive the
amplified branch RF signals from the power amplifiers and to
combine the received amplified branch RF signals into a combined
output RF signal.
[0010] In another aspect, a power amplifier system for amplifying
an RF signal includes a Zeroth order resonator power divider having
a Composite Right and Left Handed (CRLH) Metamaterial (MTM)
structure that receives an input RF signal and splits the received
input RF signal into branch RF signals in phase with respective to
one another, transistors coupled to the Zeroth order resonator
power divider to receive the branch RF signals, respectively, and
to amplify the received branch RF signals, and a Zeroth order
resonating antenna based on a CRLH MTM structure and coupled to
transistors to receive amplified branch RF signals.
[0011] In yet another aspect, a power amplifier system is provided
to include an RF input for receiving an input RF signal and a first
quadrature coupler based on a Composite Right and Left Handed
(CRLH) Metamaterial (MTM) structure. This first quadrature coupler
has a first input port coupled to the RF input to receive the input
RF signal, a second input port that is terminated, a first output
port and a second output port. The first quadrature coupler splits
the input RF signal into a first RF signal at the first output port
and a second RF signal at the second output port that has a phase
shift of 90 degrees with respect to the first RF signal. A first
power amplifier us coupled to the first output port to receive and
amplify the first RF signal and a second power amplifier is coupled
to the second output port to receive and amplify the second RF
signal. This system includes a second quadrature coupler based on a
CRLH MTM structure that includes a first input port coupled to
receive the amplified first RF signal from the first power
amplifier, a second input port coupled to receive the amplified
second RF signal from the second power amplifier, a first output
port that is terminated and a second output to produce an RF output
signal. The second quadrature coupler combines signals received at
the first and second input ports with a 90-degree phase shift to
produce the RF output signal.
[0012] These and other implementations and their variations are
described in detail in the attached drawings, the detailed
description and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A illustrates an Equivalent Circuit Model for CRLH TL
with Lumped Elements; FIG. 1B illustrates a Dispersion Diagram of
Balanced CRLH Metamaterial;
[0014] FIG. 2 illustrates a Multi-band Phase Response of LH, RH and
CRLH TL, 0.degree. @ f1 and -360.degree. @ f2;
[0015] FIG. 3A shows an example of: a Single Band N-Way MTM Power
Combiner/Splitter that has a zero-degree MTM transmission line
coupled to N branch MTM transmission lines with electrical lengths
of quarter wavelengths
[0016] FIG. 3B shows an example of a Single Band N-Way MTM Power
Combiner/Splitter that has a quarter-wavelength MTM transmission
line coupled to N zero-degree branch MTM transmission lines;
[0017] FIG. 4A illustrates a multi-band N-Way MTM Power
Combiner/Splitter with one Zero Degree CRLH TL and N Quarter
Wavelength CRLH TLs;
[0018] FIG. 4B illustrates a multi-band N-Way MTM Power
Combiner/Splitter with one Quarter Wavelength CRLH TL and NZero
Degree CRLH TL;
[0019] FIG. 5A illustrates a multi-band 2-Way MTM Wilkinson Power
Splitter/Combiner;
[0020] FIG. 5B illustrates a multi-band N-Way MTM Wilkinson Power
Splitter/Combiner;
[0021] FIG. 6A illustrates a general case of a PA with a Power
Splitter and a Power Combiner;
[0022] FIG. 6B illustrates an MTM Doherty PA and a 2-Way MTM Power
Splitter and a 2-Way MTM Power Combiner; FIG. 6C illustrates an
N-Way MTM Doherty PA, an N-Way MTM Power Splitter and an N-Way MTM
Power Combiner;
[0023] FIG. 7 illustrates an MTM Doherty PA with an MTM Wilkinson
and conventional components;
[0024] FIG. 8 illustrates an MTM Doherty PA and an MTM
Wilkinson;
[0025] FIG. 9 illustrates an MTM Inverted Doherty PA and an MTM
Wilkinson;
[0026] FIG. 10 illustrates an MTM Doherty PA and Two MTM
Wilkinsons;
[0027] FIG. 11A illustrates an Envelope Elimination and Restoration
(EER) architecture;
[0028] FIG. 11B-11D illustrates an Integration of MTM PA in
Envelope Elimination and Restoration (EER);
[0029] FIG. 12 illustrates a Series Fed Parallel Combining
Distributed Amplifier with Zero Degree CRLH TL;
[0030] FIG. 13 illustrates a Series Fed Parallel Combining
Distributed Amplifier with Zeroth Order Resonator;
[0031] FIG. 14 illustrates an N-Port Multi-band Zero Degree CRLH
TL;
[0032] FIG. 15 illustrates an N-port Multi-band zeroth order
resonator;
[0033] FIG. 16 illustrates an MTM Amplifying Antenna;
[0034] FIG. 17 illustrates an MTM Balanced Power Amplifier;
[0035] FIG. 18 illustrates a Multi-band MTM Branch Line
Coupler;
[0036] FIG. 19 illustrates a Dispersion Diagram of CRLH-TL;
[0037] FIG. 20A illustrates a Broadband MTM Branch Line
Coupler;
[0038] FIG. 20B illustrates a plot of the return and insertion loss
comparing the Broadband MTM Branch Line Coupler with a conventional
branch line coupler; FIG. 20C illustrates a plot of the phase
difference between |S21| and |S31|;
[0039] FIG. 21 illustrates a Planar MTM Forward-Wave (FW)
Directional Coupler;
[0040] FIG. 22A illustrates a Vertical MTM Forward-Wave (FW)
Directional Coupler;
[0041] FIG. 22B illustrates a cross-section view of the Vertical
MTM FW Directional Coupler shown in FIG. 22A;
[0042] FIG. 23 illustrates an MTM LINC PA; and
[0043] FIG. 24 illustrates an MTM LINC PA for different
signals.
DETAILED DESCRIPTION
[0044] Various power amplifier architectures are available for
designing RF devices and systems. Some implementations for the
techniques, devices and systems described in this document can
incorporate features in various power amplifier architectures.
[0045] Linear PAs biased Class AB are widely used in RF
applications while other PA architectures are also used such as
certain PA architectures used in Global System for Mobile
communications (GSM), General Packet Radio Service (GPRS)
communication systems and Enhanced Data rates for GSM Evolution
(EDGE) applications, some of which use the Gaussian Minimum Shift
Keying (GMSK) modulation. In general, a Class A PA can be used to
achieve good linearity at the expense of high DC power dissipation,
thus achieving low efficiency. Class AB PAs can be used to obtain a
good compromise of efficiency and linearity. By way of comparison,
Class AB amplifiers can achieve higher efficiency than Class A
amplifiers.
[0046] Many power amplifiers are designed to achieve their maximum
efficiencies when operated to produce their respective maximum
power levels. Various wireless standards targeting high
communication throughput utilize complex modulation schemes by
manipulating both amplitude and phase components to generate an RF
signal. Such techniques may impose stringent linearity requirements
on the PAs in the system. At the same time, the PAs may be required
to operate at adequate levels of efficiencies to minimize battery
power consumption and to reduce heat dissipation. Thus, PA designs
that achieve good efficiency and linearity are desired for wireless
communication systems. In addition to operating in the linear
region while maintaining adequate efficiency, modern wireless
applications may require devices to support multiple frequency
bands. In some implementations, PAs are designed to operate in
their respective single bands and are packaged into a single module
to provide multiple band operations.
[0047] Some modulation schemes used in wireless systems, such as
Quadrature Amplitude Modulation (QAM) with Orthogonal Frequency
Divisional Multiple Access (OFDMA) or Code Division Multiple Access
(CDMA), create RF signals that have a high Peak to Average Power
Ratio (PAPR) in the range of 7-15 dB, for example. To avoid this,
the PA is set to operate so as to output the power that is lower
than its peak output power until the linearity requirements are
just met. This operation is referred to as "power back-off" and can
significantly reduce the efficiency of the PA when the PA is
designed to achieve its maximum efficiency at or near its maximum
power level. Typical Power Added Efficiency (PAE) values for OFDM
signals (802.11a/g, n, WiMax) are 15% to 20% @ 3% RMS EVM or
<10% @ 2% RMS EVM, where EVM stands for Error Vector Magnitude.
In an RF power amplifier, PAE is defined as the ratio of the
difference between the output and input RF power to the DC power
consumed, whereas drain efficiency is defined as the ratio of the
output power to the DC power consumed.
[0048] In many PA designs, the linearity and good efficiency do not
occur simultaneously. The PA output power may be backed off from
its maximum power to meet linearity requirements while compromising
the PA efficiency during the backing-off operation.
[0049] To increase the output power of a PA, either the voltage
swing or the current swing of the PA needs to be increased.
Conventionally, the size of the device periphery is increased to
allow a large current swing. An increase in the device size can
increase its maximum power, but also decreases its optimum load
impedance, which is difficult to match. The architectures presented
in this application can use any technology available. Examples
include printing the designs on a conventional FR-4 PCB, Duroid and
using thin/thick-film ceramic techniques based on alumina or Low
Temperature Co-fired Ceramic (LTCC). Another example is a
monolithic fabrication. The architectures presented herein are
applicable to most Monolithic Microwave Integrated Circuits (MMIC)
semiconductor processes. These include GaAs-, InGaP-, SiGe-, GaN,
InP, Si-based fabrication processes and others. The transistors in
the different architectures can be FET, pHEMT, HBT, CMOS, LDMOS and
BiCMOS transistors and the like based on the appropriate device
process technology.
[0050] Examples of power amplifier (PA) architectures designed to
enhance efficiency and linearity include the Doherty amplifier, the
Envelope Elimination and Restoration (EER), and the Linear
amplification using Non-linear Components (LINC). Distributed
amplifier architectures can be used for broadband amplification.
These and other different techniques and architectures can
integrate different classes of amplification. Examples include a
class A/B/AB/C/D/E/F/F-1/J or a combination thereof. Each class
presents some advantages and disadvantages depending on the
performance requirements.
[0051] The Doherty architecture uses two or more power amplifiers
and operates in the back-off region in order to maintain good
linearity with good efficiency. The Doherty architecture has the
advantage of being easy to implement, and there is no need for a
high-power modulator that restricts the bandwidth requirement. A PA
system based on the Doherty architecture can include two power
amplifiers: a carrier PA or main PA and one peak PA or auxiliary
PA. These two power amplifiers are evenly or unevenly fed with
input power and can be designed to operate in any of the classes
mentioned above. Some Doherty PA implementations use a class-AB PA
for the carrier PA and a class-C PA for the peak PA.
[0052] In operation of a Doherty PA system, when the input power is
low, the peak PA is OFF, and the carrier PA is ON, acting as a
controlled current source seeing twice the optimum resistance. In
this state, the carrier PA has reached to one half of its maximum
current and its maximum voltage. When the input power increases to
a certain level, the peak PA turns ON and acts as a controlled
current source, and the carrier PA acts as a controlled voltage
source in this case. When the current of the peak PA increases, the
impedance seen by the carrier PA decreases. Therefore, the output
voltage remains constant. When the input power reaches its maximum,
the two PAs experience optimum impedance which can be equal to the
characteristic impedance of the quarter wavelength. The current is
at a maximum at this level. The peak amplifier modulates the load
during the signal peak so as to prevent the carrier PA from
saturating. It is possible to unevenly feed the Doherty PA by
applying more power to the peak PA than to the carrier PA in order
to fully modulate the load impedance to the value of the optimum
impedance at high power level. This results in more output power
than the case in which the PAs are driven with the same amount of
power. Inverted Doherty architecture improves carrier cell
efficiency at low levels when the peak PA is OFF. In this case, the
challenge is to design the output matching with the quarter
wavelength.
[0053] A distributed power amplifier is a structure that can
exhibit broadband characteristics in terms of gain, group delay and
impedance matching. A balanced power amplifier splits an input
signal into two identical PAs by using a phase quadrature coupler,
and then the two outputs of the PAs are recombined by using another
phase quadrature coupler. The advantage of using phase quadrature
couplers is that any mismatch reflection from any of the PAs
appears in antiphase and does not affect the input or output of the
system. The balanced configuration can therefore enhance the
stability of the PA and is insensitive to the load mismatch.
[0054] In addition to the above and other PA architectures, the
techniques, devices and systems described in this document can be
implemented based on different circuit structures. The propagation
of electromagnetic waves in most materials obeys the right handed
rule for the (E,H,.beta.) vector fields, where E is the electrical
field, H is the magnetic field, and .beta. is the wave vector. The
phase velocity direction is the same as the direction of the signal
energy propagation (group velocity) and the refractive index is a
positive number. Such materials are "right handed" (RH). Most
natural materials are RH materials. Artificial materials can also
be RH materials. A metamaterial (MTM) has an artificial structure.
When designed with a structural average unit cell size p much
smaller than the wavelength of the electromagnetic energy guided by
the metamaterial, the metamaterial can behave like a homogeneous
medium to the guided electromagnetic energy. Unlike RH materials, a
metamaterial can exhibit a negative refractive index with
permittivity .epsilon. and permeability .mu. being simultaneously
negative, and the phase velocity direction is opposite to the
direction of the signal energy propagation where the relative
directions of the (E,H,.beta.) vector fields follow the left handed
rule. Metamaterials that support only a negative index of
refraction with permittivity .epsilon. and permeability .mu. being
simultaneously negative are pure "left handed" (LH) metamaterials.
Many metamaterials are mixtures of LH metamaterials and RH
materials and thus are Composite Right and Left Handed (CRLH)
metamaterials. A CRLH metamaterial can behave like a LH
metamaterial at low frequencies and a RH material at high
frequencies. Designs and properties of various CRLH metamaterials
are described in, for example, Caloz and Itoh, "Electromagnetic
Metamaterials: Transmission Line Theory and Microwave
Applications," John Wiley & Sons (2006). CRLH metamaterials and
their applications in antennas are described by Tatsuo Itoh in
"Invited paper: Prospects for Metamaterials," Electronics Letters,
Vol. 40, No. 16 (August, 2004).
[0055] CRLH metamaterials can be structured and engineered to
exhibit electromagnetic properties that are tailored for specific
applications and can be used in applications where it may be
difficult, impractical or infeasible to use other materials. In
addition, CRLH metamaterials may be used to develop new
applications and to construct new devices that may not be possible
with RH materials. Examples of MTM antenna, transmission lines, RF
power dividers and combiners can be found, e.g., in U.S. patent
applications: Ser. No. 11/741,674 entitled "Antennas, Devices and
Systems Based on Metamaterial Structures" and filed on Apr. 27,
2007 (U.S. Patent Publication No. US20080258981), Ser. No.
11/844,982 entitled "Antennas Based on Metamaterial Structures" and
filed on Aug. 24, 2007 (U.S. Patent Publication No. US20080048917),
Ser. No. 11/963,710 entitled "Power Combiners and Dividers Based on
Composite Right and Left Handed Metamaterial Structures" and filed
on Dec. 21, 2007 (U.S. Patent Publication No. ______), and Ser. No.
12/340,657 entitled "Multi-Metamaterial-Antenna Systems with
Directional Couplers" and filed on Dec. 20, 2008 (U.S. Patent
Publication No. ______), which are incorporated by reference as
part of the disclosure of this document. The circuit structures for
the present PA architectures can be based on RH material structures
or CRLH MTM structures. As an example, the transmission lines used
in the present PA architectures can be implemented by CRLH
Metamaterial (MTM) transmission lines or circuit components to
achieve multi-band or wide-band operations in compact form factors
while complying with impedance and phase matching conditions.
Consider a simple example of a 1-dimensional structure of CRLH MTM
elements which can include MTM unit cells characterized by the cell
shunt inductance (LL), the cell shunt capacitance (CR), the cell
series inductance (LR) and the cell series capacitance (CL). These
parameters and the number of MTM unit cells determine the resonant
frequencies, the corresponding bandwidth, input and output
impedance matching and the circuit structure and size. The LH
properties of MTM structures allow the dimensions of MTM structures
to be smaller than equivalent circuits made of RH materials, e.g.,
a fraction of .lamda./2, where .lamda. is the propagation
wavelength of an RF signal in the free-space. An CRLH transmission
line can be designed to have an electrical length that corresponds
to various phase values, including a phase of zero degree, 180
degrees or a multiple of 180 degrees, 90 degrees or a multiple of
90 degrees at an operating signal frequency. A CRLH structure can
also be designed to support two or more frequency bands or broad
band operations. CRLH MTM structures can be used in PA systems to
provide multi-band operation, high efficiency, variable output
power, and compact form factor while complying with matching
conditions. Examples in this document include (1) power amplifier
designs multiple PA systems such as Doherty PA architectures using
the MTM technology in various configurations such as single band
MTM PA systems, multi-band MTM PA systems, MTM Wilkinson or MTM
power combiners and splitters, and MTM Inverted Doherty PA; (2)
envelope elimination restoration (EER) PA systems including EER PAs
that drive drain bias of an MTM PA and mix digital signals before
feeding an MTM PA; (3) MTM balanced PA systems in multi-band and
broadband configurations; and (4) MTM Linear Amplification using
Non-linear Components (LINC).
[0056] A pure Left Handed (LH) material follows the left hand rule
for the vector trio (E,H,.beta.), and the phase velocity direction
is opposite to the signal energy propagation. Both the permittivity
and permeability of the LH material are negative. A Composite
Right/Left Handed (CRLH) metamaterial can exhibit both left hand
and right hand electromagnetic modes of propagation depending on
the regime or frequency of operation. Under certain circumstances,
a CRLH metamaterial can exhibit a non-zero group velocity when the
wavevector of a signal is zero. This situation occurs when both
left hand and right hand modes are balanced. In an unbalanced mode,
there is a bandgap in which electromagnetic wave propagation is
forbidden. In the balanced case, the dispersion curve does not show
any discontinuity at the transition point of the propagation
constant .beta.(.omega..sub.o)=0 between the Left and Right handed
modes, where the guided wavelength is infinite
.lamda..sub.g=2.pi./|.beta.|.fwdarw..infin. while the group
velocity is positive: v g = d .omega. d .beta. .beta. = 0 > 0 (
1 ) ##EQU1## This state corresponds to the Zeroth Order mode m=0 in
a Transmission Line (TL) implementation in the LH region. The CRHL
structure supports a fine spectrum of low frequencies with a
dispersion relation that follows the negative .beta. parabolic
region which allows a physically small device to be built that is
electromagnetically large with unique capabilities in manipulating
and controlling near-field radiation patterns. When this TL is used
as a Zeroth Order Resonator (ZOR), it allows a constant amplitude
and phase resonance across the entire resonator. The ZOR mode may
be used to build MTM-based power combiners and splitters or
dividers, directional couplers, matching networks, and leaky wave
antennas. Examples of MTM-based power combiners and dividers are
described below.
[0057] In RH TL resonators, the resonance frequency corresponds to
electrical lengths .theta..sub.m=.beta..sub.ml=m.pi. (m=1, 2, 3, .
. . ), where l is the length of the TL. The TL length should be
long enough to reach low and wide spectrum of resonant frequencies.
The operating frequencies of a pure LH material are at low
frequencies. A CRLH metamaterial structure is very different from
RH and LH materials and can be used to reach both high and low
spectral regions of the RF spectral ranges of RH and LH materials.
In the CRLH case, .theta..sub.m=.beta..sub.ml=m.pi., where l is the
length of the CRLH TL and the parameter m=0, .+-.1, .+-.2, .+-.3, .
. . , .+-..infin..
[0058] FIG. 1A illustrates an equivalent circuit of an MTM
transmission line 101 with unit cell 103 in which different unit
cells can be connected together in series in a periodic
configuration. The equivalent circuit for each unit cell 103 has a
right-handed (RH) series inductance L.sub.R, a shunt capacitance
C.sub.R and a left-handed (LH) series capacitance C.sub.L, and a
shunt inductance L.sub.L. The shunt inductance L.sub.L and the
series capacitance C.sub.L are structured and connected to provide
the left handed properties to the unit cell 103. This CRLH TL can
be implemented by using distributed circuit elements, lumped
circuit elements or a combination of both. Each unit cell 101 is
smaller than .lamda./10 where .lamda. is the wavelength of the
electromagnetic signal that is transmitted in the CRLH TL. CRLH TLs
possess interesting phase characteristics such as anti-parallel
phase, group velocity, non-linear phase slope and phase offset at
zero frequency.
[0059] FIG. 1B shows the dispersion diagram of a balanced CRLH
metamaterial with the unit cell in FIG. 1A. The CRLH structure can
support a fine spectrum of low frequencies and produce higher
frequencies including the transition point with m=0 that
corresponds to infinite wavelength. This can be used to provide
integration of CRLH antenna elements, such as but not limited to
directional couplers, matching networks, amplifiers, filters, and
power combiners and splitters. In some implementations, RF or
microwave circuits and devices may be made of a CRLH MTM structure,
such as but not limited to directional couplers, matching networks,
amplifiers, filters, and power combiners and splitters.
[0060] Referring back to FIG. 1A, in the unbalanced case where
L.sub.RC.sub.L.noteq.L.sub.LC.sub.R, two different resonant
frequencies exist: .omega..sub.se and .omega..sub.sh that can
support an infinite wavelength given by equations: .omega. sh = 1 C
R .times. L L ( 2 ) .omega. se = 1 C L .times. L R . ( 3 ) ##EQU2##
At .omega..sub.se and .omega..sub.sh the group velocity
(v.sub.g=d.omega./d.beta.) is zero and the phase velocity
(vp=.omega./.beta.) is infinite. When the series and shunt
resonances are equal, i.e., L.sub.RC.sub.L=L.sub.LC.sub.R, the
structure is said to be balanced, and the resonant frequencies
coincide: .omega..sub.se=.omega..sub.sh=.omega..sub.0. (4)
[0061] For the balanced case, the phase response can be
approximated by the following equations: .phi. C = .phi. RH + .phi.
LH = - .beta. .times. .times. l = - Nl .times. .times. .omega. c (
5 ) .phi. RH .apprxeq. - N .times. .times. 2 .times. .times. .pi.
.times. .times. f .times. L R .times. C R ( 6 ) .phi. LH .apprxeq.
N 2 .times. .times. .pi. .times. .times. f .times. L L .times. C L
( 7 ) ##EQU3## where N is the number of unit cells. The slope of
the phase is given by equation: d .phi. CRLH d f = - N .times.
.times. 2 .times. .times. .pi. .times. L R .times. C R - N 2
.times. .times. .pi. .times. .times. f 2 .times. L L .times. C L (
8 ) ##EQU4## The characteristic impedance is given by equation: Z o
CRLH = L R C R = L L C L . ( 10 ) ##EQU5## The inductance and
capacitance values may be selected and controlled to create a
desired slope for a chosen frequency. In addition, the phase may be
set to have a positive phase offset at DC. These two factors are
used to provide the designs of multi-band and other MTM power
combining and dividing structures presented herein.
[0062] The following sections provide examples of determining MTM
parameters of multi-band mode MTM structures, and similar
techniques can be used to determine MTM parameters with three or
more bands.
[0063] In a multi-band MTM structure, the signal frequencies
f.sub.1, f.sub.2 for the two bands are first selected for two
different phase values: .phi..sub.1 at f.sub.1 and .phi..sub.2 at
f.sub.2. In this example, let N be the number of unit cells in the
CRLH TL and Z.sub.t, the characteristic impedance. The values for
parameters L.sub.R, C.sub.R, L.sub.L and C.sub.L can be calculated
as: L R = Z t .function. [ .PHI. 1 .function. ( .omega. 1 .omega. 2
) - .PHI. 2 ] N .times. .times. .omega. 2 .function. [ 1 - (
.omega. 1 .omega. 2 ) 2 ] .times. .times. C R = .PHI. 1 .function.
( .omega. 1 .omega. 2 ) - .PHI. 2 N .times. .times. .omega. 2
.times. Z t .function. [ 1 - ( .omega. 1 .omega. 2 ) 2 ] ( 11 ) L L
= NZ t .function. [ 1 - ( .omega. 1 .omega. 2 ) 2 ] .omega. 1
.function. [ .PHI. 1 - ( .omega. 1 .omega. 2 ) .times. .PHI. 2 ]
.times. .times. C L = N .function. [ 1 - ( .omega. 1 .omega. 2 ) 2
] .omega. 1 .times. Z t .function. [ .PHI. 1 - ( .omega. 1 .omega.
2 ) .times. .PHI. 2 ] ( 12 ) Z 0 CRLH = L R C R = L L C L ( 13 )
##EQU6##
[0064] In the unbalanced case, the propagation constant is given by
equation: .beta. = s .function. ( .omega. ) .times. .omega. 2
.times. L R .times. C R + 1 .omega. 2 .times. L L .times. C L - ( L
R L L + C R C L ) .times. .times. where ( 14 ) s .function. (
.omega. ) = { - 1 if .times. .times. .omega. < min .function. (
.omega. se , .omega. sh ) .times. : .times. .times. LH .times.
.times. range + 1 if .times. .times. .omega. > max .function. (
.omega. se , .omega. sh ) .times. : .times. .times. RH .times.
.times. range ( 15 ) ##EQU7##
[0065] For the balanced case: .beta. = .omega. .times. L R .times.
C R - 1 .omega. .times. L L .times. C L ( 16 ) ##EQU8## A CRLH TL
has a physical length of d with N unit cells each having a length
of p: d=Np. The signal phase value is .phi.=-.beta.d. Therefore,
.beta. = - .PHI. d ( 17 ) .beta. i = - .PHI. i ( N p ) ( 18 )
##EQU9##
[0066] It is possible to select two different phases .phi..sub.1
and .phi..sub.2 at two different frequencies f1 and f2,
respectively: { .beta. 1 = .omega. 1 .times. L R .times. C R - 1
.omega. 1 .times. L L .times. C L .beta. 2 = .omega. 2 .times. L R
.times. C R - 1 .omega. 2 .times. L L .times. C L ( 19 )
##EQU10##
[0067] In comparison, a non-MTM RH microstrip transmission line
exhibits the following dispersion relationship: .beta. n = .beta. 0
+ 2 .times. .times. .pi. p .times. n , n = 0 , .+-. 1 , .+-. 2 , (
20 ) ##EQU11## See, for example, the description on page 370 in
Pozar, "Microwave Engineering," 3rd Edition and page 623 in Collin,
"Field Theory of Guided Waves," Wiley-IEEE Press; 2nd Edition (Dec.
1, 1990).
[0068] Multi-band CRLH TL devices can be designed based on a matrix
approach described in U.S. patent application Ser. No. 11/844,982.
Under this matrix approach, each 1D CRLH transmission line includes
N identical cells with shunt (L.sub.L, C.sub.R) and series
(L.sub.R, C.sub.L) parameters. These five parameters, i.e.,
(L.sub.L, C.sub.R), (L.sub.R, C.sub.L) and N identical cells,
determine the N resonant frequencies and phase curves,
corresponding bandwidth, and input/output TL impedance variations
around these resonances.
[0069] The frequency bands are determined from the dispersion
equation derived by letting the N CRLH cell structure resonate with
n.pi. propagation phase length, where n=0, .+-.1, . . . .+-.(N-1).
In other words, a zero and 2.pi. phase resonances can be
accomplished with N=3 CRLH cells. Furthermore, a tri-band power
combiner and splitter can be designed using N=5 CRLH cells where
zero, 2.pi., and 4.pi. cells are used to define resonances.
[0070] The n=0 mode resonates at .omega..sub.0=.omega..sub.SH, and
higher frequencies are given by the following equation for the
different values of M specified in Table 1: For .times. .times. n
> 0 , .times. .omega. .+-. n 2 = .omega. SH 2 + .omega. SE 2 + M
.times. .times. .omega. R 2 2 .+-. ( .omega. .times. SH .times. 2 +
.omega. .times. SE .times. 2 + M .times. .times. .omega. .times. R
.times. 2 2 ) 2 - .omega. SH 2 .times. .omega. SE 2 ( 21 )
##EQU12##
[0071] Table 1 provides M values for N=1, 2, 3, and 4.
TABLE-US-00001 TABLE 1 Resonances for N = 1, 2, 3 and 4 cells N
\Modes |n| = 0 |n| = 1 |n| = 2 |n| = 3 N = 1 M = 0; .omega..sub.0 =
.omega..sub.SH N = 2 M = 0; .omega..sub.0 = .omega..sub.SH M = 2 N
= 3 M = 0; .omega..sub.0 = .omega..sub.SH M = 1 M = 3 N = 4 M = 0;
.omega..sub.0 = .omega..sub.SH M = 2 - {square root over (2)} M =
2
[0072] FIG. 2 shows an example of the phase response of a CRLH TL
which is a combination of the phase of the RH components and the
phase of the LH components. Phase curves for CRLH, RH and LH
transmission lines are shown. The CRLH phase curve approaches the
LH TL phase at low frequencies and approaches the RH TL phase at
high frequencies. Notably, the CRLH phase curve crosses the
zero-phase axis with a frequency offset from zero. This offset from
zero frequency enables the CRLH curve to be engineered to intercept
a desired pair of phases at any arbitrary pair of frequencies. The
inductance and capacitance values of the LH and RH can be selected
and controlled to create a desired slope with a positive offset at
the zero frequency (DC). By way of example, FIG. 2 shows that the
phase chosen at the first frequency f.sub.1 is 0 degree, and the
phase chosen at the second frequency f.sub.2 is -360 degrees. In
addition, a CRLH TL can be used to obtain an equivalent phase with
a much smaller footprint than an RH transmission line.
[0073] Therefore, CRLH power combiners and dividers can be designed
for combining and dividing signals at two or more different
frequencies under impedance matched conditions to achieve compact
devices that are smaller than conventional combiners and dividers.
Referring back to FIG. 1A, each CRLH unit cell 103 can be designed
based on different unit configurations in CRLH power combiners and
dividers. The properties of the metamaterial offer new
possibilities for different types of design for dual-frequencies
but also for multi-band systems.
[0074] One example of a power amplifier system for amplifying an RF
signal based on a CLRH MTM structure can be designed to include a
power divider, multiple power amplifiers connected in parallel and
a power combiner. Both or just one of the power divider and the
power combiner can be a CRLH MTM structure to achieve certain
technical features. In this system, an input port is provided to
receive an input RF signal. The power divider includes (1) an input
CRLH transmission line coupled to the input port to receive the
input RF signal and (2) multiple output CRLH transmission lines
that are coupled to the input CRLH transmission line to split the
received input RF signal into different branches. The power
amplifiers are coupled to the output branch transmission CRLH lines
of the power divider, respectively. Each power amplifier receives
and amplifies an RF signal to produce an amplified RF signal. The
power combiner in this system includes multiple input CRLH
transmission lines that are respectively coupled to the power
amplifiers to receive amplified RF signals produced by the power
amplifiers. Each input CRLH transmission line of the power combiner
is connected to one power amplifier. This combiner also includes an
output CRLH transmission line coupled to the input CRLH
transmission lines to combine the received amplified branch RF
signals into a combined output RF signal.
[0075] The above MTM-based multi-PA system can be implemented as a
MTM-enhanced Doherty PA system. The Doherty technique may achieve
high efficiency in the back-off region. Also, by using the property
of the MTM, linearity may be enhanced. A non-MTM Doherty PA has a
large size due to presence of quarter wavelength transformers
designed on microstrip which support a single-band. MTM-enhanced
Doherty PA can replace the single-band quarter wavelength
transformers with multi-band MTM quarter wavelength transformers
which are also more compact. The power splitter at the input can be
implemented by a compact MTM multi-band power splitter. The
input/output matching networks may be integrated in the power
combiner for better efficiency. An N-way power combiner/splitter
may be also used with each branch matched to the desired impedance.
The use of MTM elements may increase the bandwidth of operation by
being able to control the phase slope. In addition, the MTM
properties may facilitate the connection of antennas with poor
Voltage Standing Wave Ratio (VSWR), for example.
[0076] The power divider or combiner in the above MTM-based
multi-PA system can be designed to include a first transmission
line including a CRLH MTM structure and multiple second
transmission lines of CRLH MTM structures that are coupled to one
terminal of the first transmission line to either split an input RF
signal received from the first transmission line into multiple
output RF signals in the second transmission lines, respectively,
when configured as a power divider, or, when configured as a power
combiner, combine input RF signals in the second transmission lines
into an output RF signal in the first transmission line. The first
transmission line and the second transmission lines are structured
to be in two configurations. In the first configuration, the first
transmission line is a CRLH MTM transmission line of an electrical
length having a phase delay of .+-.m90.degree. where m is a
positive integer, and each of the second transmission lines is a
CRLH MTM transmission line of an electrical length having a zero
phase delay or a phase delay of .+-.n180.degree. where n is a
positive integer. In the second configuration, the first
transmission line is a CRLH MTM transmission line of an electrical
length having a zero phase delay or a phase delay of
.+-.m180.degree. where m is a positive integer and each of the
second transmission lines is a CRLH MTM transmission line having a
phase delay of .+-.n90.degree. where n is a positive integer. The
transmission lines can be designed to have a single RF frequency or
two or more different RF frequencies.
[0077] FIGS. 3A and 3B show examples of two different single band
N-way MTM power combiner/splitters. These two MTM power
combiner/splitters can be designed to achieve a more compact
package with respect to non-MTM power combiner/splitters.
[0078] In one implementation shown in FIG. 3A, each of the quarter
wavelength (.PHI..sub.12) CRLH-TLs 301 are connected at one end to
its corresponding impedance 303, and at the other end to a zero
degree (.PHI..sub.11) CRLH-TL 305. The phase .PHI..sub.11 is the
phase delay caused by the electrical length and is at 0.degree.,
.+-.180.degree., .+-.360.degree., . . . , or a multiple of
180.degree. (i.e., n180.degree. where n is a positive or negative
integer), and the phase .PHI..sub.12 is the phase delay caused by
the electrical length and is at .+-.90.degree., .+-.270.degree., .
. . or a multiple of 90.degree. (n90.degree. where n is a positive
or negative odd integer). In this application, the "quarter
wavelength" refers to an odd multiple of a quarter wavelength, i.e.
(2n+1).times..lamda./4, where n=1, 2, 3 . . . . As illustrated, the
quarter wavelength (.PHI..sub.12) CRLH-TLs 301 terminated at their
respective impedances Z.sub.1, Z.sub.2, . . . and Z.sub.N.
[0079] The quarter wavelength (.PHI..sub.12) CRLH-TLs 301 and the
zero-degree (.PHI..sub.11) CRLH-TL 305 are designed to provide
impedance matching between each of the impedances Z.sub.1, Z.sub.2,
. . . and Z.sub.N to the impedance 307 (which can be, e.g., 50 Ohms
as shown) at the terminal end of the zero-degree (.PHI..sub.11)
CRLH-TL 305. In this regard, each of the quarter wavelength
(.PHI..sub.12) CRLH-TLs is used to transform the corresponding
impedance to match the impedance 307 (e.g., 50 ohms as shown). The
number of ports, N, may be selected based on the requirement of a
specific application. In the implementation shown in FIG. 3A, the
zero degree (.PHI..sub.11) CRLH-TL 305 is connected between the
impedance 307 at one terminal end of the CRLH-TL 305 and the
quarter wavelength (.PHI..sub.12) CRLH-TLs 301 at the other
terminal end of the CRLH-TL 305. In another implementation, the
quarter wavelength (.PHI..sub.12) CRLH-TLs 301 may be connected
directly to the 50-ohm impedance 307 without the zero degree
(.PHI..sub.11) CRLH-TL 305. For the example of the impedance 307 at
50 ohm, the impedance of each quarter wavelength CRLH-TL 301 is
determined by Z.sub.0= {square root over ((50*Z.sub.J*N))}, where
J=1, . . . , or N, in either configuration.
[0080] FIG. 3B shows another implementation in which each of the
zero degree (.PHI..sub.11) CRLH-TLs 321 is connected at one end to
an impedance Z.sub.1 323 and at the other end to a quarter
wavelength (.PHI..sub.12) CRLH-TL 325. N number of the impedances
with the same value Z.sub.1 323 connected in parallel are
transformed to 50 ohms 327 by the quarter wavelength (.PHI..sub.12)
CRLH-TL 325. For the example of the impedance 327 at 50 ohm, the
impedance of the quarter wavelength (.PHI..sub.12) CRLH-TL 325 is
determined by Z 0 = ( 50 * Z 1 * 1 N ) ##EQU13##
[0081] FIGS. 4A and 4B presents two examples of multi-band N-way
MTM power combiner/splitters which may be used to combine or split
the power in the Doherty architecture or other PA
architectures.
[0082] In the implementation shown in FIG. 4A, each of quarter
wavelength (.PHI..sub.12, .PHI..sub.22) CRLH-TLs 401 may be
connected at one end to its corresponding impedance 403, i.e. one
of Z.sub.1, Z.sub.2, . . . and Z.sub.N, and at the other end to a
zero degree (.PHI..sub.11, .PHI..sub.21) CRLH-TL 405, where both
.PHI..sub.11 and .PHI..sub.21 are set to be any one of 0.degree.,
.+-.180.degree., .+-.360.degree., . . . .+-.n180.degree. (n is a
positive or negative integer). Both .PHI..sub.12 and .PHI..sub.22
are set to be any of .+-.90.degree., .+-.270.degree., . . .
.+-.(2n+1)90.degree. where n is a positive or negative integer and
(2n+1) is an odd integer. At one frequency f.sub.1, each quarter
wavelength (.PHI..sub.12, .PHI..sub.22) CRLH-TL 401 provides a
phase of .PHI..sub.12, and at another frequency f.sub.2 it provides
a phase of .PHI..sub.22. The zero degree (.PHI..sub.11,
.PHI..sub.21) CRLH-TL 405 has a phase of .PHI..sub.11 at the
frequency f.sub.1 and a phase of .PHI..sub.21 at the other
frequency f.sub.2. Each of the quarter wavelength (.PHI..sub.12,
.PHI..sub.22) CRLH-TLs 401 is used to transform the corresponding
impedance to 50 ohms 407, where the number of ports, N, can be
arbitrary. The impedance of each quarter wavelength CRLH-TL 401 is
determined by Z.sub.0= {square root over ((50*Z.sub.j*N))}, j=1, .
. . , or N, for both .PHI..sub.12 and .PHI..sub.22.
[0083] In another implementation shown in FIG. 4B, each of zero
degree (.PHI..sub.11, .PHI..sub.21) CRLH-TLs 421 may be connected
at one end to an impedance Z.sub.1 423 and at the other end to a
quarter wavelength (.PHI..sub.12, .PHI..sub.22) CRLH-TL 425. N
number of the impedances with the same value Z.sub.1 423 connected
in parallel are transformed to 50 ohms 427 by the quarter
wavelength (.PHI..sub.12, .PHI..sub.22) CRLH-TL 425. The impedance
of the quarter wavelength (.PHI..sub.12, .PHI..sub.22) CRLH-TL 425
is determined by Z 0 = ( 50 * Z 1 * 1 N ) ##EQU14## for both
.PHI..sub.12 and .PHI..sub.22.
[0084] In yet another implementation, the series capacitor C.sub.L
in the equivalent circuit shown in FIG. 1A may be replaced with a
varactor. The bias of the varactor is adjusted in order to control
the impedance matching of the CRLH-TL to compensate for the
impedance change depending on the number of multiple CRLH-TLs that
are operating in the "ON" state.
[0085] Wilkinson power combiners and splitter can also be designed
based on MTM structures. A Wilkinson power splitter, for example,
can include a first CRLH MTM transmission line as the input
transmission line of the power splitter, a second CRLH MTM
transmission line as one of the branch output transmission lines of
the power splitter to have a first terminal coupled to the first
CRLH MTM transmission line and a second terminal. A third CRLH MTM
transmission line is provided as another one of the branch output
transmission lines to have a first terminal coupled to the first
CRLH MTM transmission line and a second terminal. A resistor is
coupled as a bridge between the second and third CRLH MTM
transmission lines by coupling its first terminal to the second
terminal of the second CRLH MTM transmission line and by coupling
its second terminal to the second terminal of the third CRLH MTM
transmission line. This Wilkinson power splitter also includes a
fourth CRLH MTM transmission line coupled to the second terminal of
the third CRLH MTM transmission line and a fifth CRLH MTM
transmission line coupled to the second terminal of the third CRLH
MTM transmission line. The fourth and fifth transmission lines
provide the outputs of the Wilkinson power splitter.
[0086] A Wilkinson power combiner is a reversed design of the power
splitter. Such a combiner is placed downstream from power
amplifiers to receive the outputs of the power amplifiers. In the
example of two power amplifiers, the combiner can include a first
CRLH MTM transmission line having a first terminal coupled to a
first power amplifier to receive a first amplified RF signal and a
second terminal to output the first amplified RF signal, and a
second CRLH MTM transmission line having a first terminal coupled
to a second power amplifier to receive a second amplified RF signal
and a second terminal to output the second amplified RF signal. A
resistor is provided to have its first terminal coupled to the
second terminal of the first CRLH MTM transmission line and its
second terminal coupled to the second terminal of the second CRLH
MTM transmission line. In addition, a third CRLH MTM transmission
line is coupled to the second terminal of the first CRLH MTM
transmission line and a fourth CRLH MTM transmission line is
coupled to the second terminal of the fourth CRLH MTM transmission
line. The combiner further includes a fifth CRLH MTM transmission
line forming the output transmission line and coupled to the third
and fourth CRLH MTM transmission lines to combine their outputs
into a single output.
[0087] FIG. 5A shows an example of a 2-Way MTM Wilkinson Power
Splitter/Combiner. In this implementation, a multi-band input RF
signal is received at an input port 501 having frequencies f.sub.1
and f.sub.2, for example. The RF input signal may be unevenly or
evenly divided into two branches. Each CRLH-TLs 503 may be
connected at one end to its corresponding resistor 505, i.e. one of
R, and at the other end to a CRLH-TL 507, where the impedance of
each CRLH-TL 503 is determined by the impendence Z.sub.0,1 from the
following equations: k.sup.2=P.sub.3/P.sub.2, where k is the ratio
of predetermined uneven powers, P.sub.2 and P.sub.3, at outputs
port 2 and port 3, respectively, Z.sub.0,3=Z.sub.0,1
(1+k.sup.2)/k.sup.3, Z.sub.0,3=Z.sub.0,1 {square root over
((1+k.sup.2)/k.sup.3)} Z.sub.0,2=K.sup.2Z.sub.0,3, and
R=Z.sub.0,1(k+1/k) The two impedances with the value Z.sub.0,2 and
Z.sub.0,3 corresponding to each CRLH-TLs 503 are transformed to 50
ohms 509 by corresponding CRLH-TLs 511.
[0088] FIG. 5B illustrates an implementation of an N-Way MTM
Wilkinson Power Splitter/Combiner. In this implementation, a
multi-band input RF signal is received at an input port 521 having
frequencies f.sub.1 and f.sub.2, for example. The RF input signal
may be unevenly or evenly divided into N branches. Each CRLH-TLs
523 can be connected at one end to its corresponding resistor 525,
i.e. one of R.sub.1, R.sub.2, . . . and R.sub.N, and at the other
end to a CRLH-TL 527, where the impedance of each CRLH-TL 523 is
determined by the input impendence Z.sub.0,1. The other end of each
corresponding resistor 525 is connected to each other to form a
single connection between all N resistors in this Wilkinson design.
In this example, the N impedances with the value Z.sub.0,N
corresponding to each CRLH-TLs 523 can be transformed to the
impedance 529 (which can be, e.g., 50 ohms) by the corresponding
CRLH-TLs 531.
[0089] Based on the above MTM-based power combiners or splitters,
FIG. 6A shows an example of a single or multi-band PA system
comprising an N-way power splitter 601 and an N-way power combiner
603. At least one of the devices 601 and 603 is based a CRLH MTM
design. In operation, the PA system amplifies the low input power
of the RF signal received at an input port into higher levels of RF
output power transmitted at an output port by converting DC power
into RF power. For example, an input signal is received at the
input port 600 coupled to an N-way Power Splitter 601 where the
input signal is unevenly or evenly divided into N branches forming
multiple output signals. Each output signals of the N-way Power
Splitter A 601 is connected to the input of each PA.sub.n 605,
where n=1, 2, . . . N. The output of each PA.sub.n 605 is connected
to each input of an N-way Power Combiner 603, where n=1, 2, . . .
N. The output of the N-way Power Combiner 603 transmits the
amplified combined input signal to an output port 607.
[0090] Various implementations of the PA-Power Splitter/Combiner
system described above and shown in FIG. 6A can be made. For
example, an MTM power splitter can be used in FIG. 6A to reduce the
size and, thus, integrate the PA system on a microchip depending on
the substrate. The MTM structures can be used to enable multi-band
operations. The MTM application described for the power splitter
can be applied to the power combiner at the output of the system
resulting in similar sizing benefits and multi-band properties.
[0091] The exemplary systems described in this document can utilize
PAs such as Doherty PAs, Balanced PAs (e.g., MTM Balanced PAs and
non-MTM Balanced PAs), and other MTM and non-MTM PAs. Various types
and combinations of N-way splitters and N-way combiners may be
implemented in the PA system shown in FIG. 6A. For example, each
N-way Power Splitter 601 and N-way combiner 603 may be formed from
MTM or conventional structures. Examples of the various
combinations of N-way Power Splitter 601 and N-way Power Combiner
603 shown in FIG. 6A may include conventional splitters/MTM
combiners, MTM splitters/conventional combiners, and MTM
splitters/MTM combiners. In addition, these systems may implement
MTM and conventional structures operating in different frequency
ranges or bands, e.g., one or more frequency bands.
[0092] The Doherty architecture can be implemented to include two
power amplifiers that are evenly fed with input power and can be
designed to operate in any of the classes such as class
A/B/AB/C/D/E/F/F-1/J. It is possible to unevenly feed the Doherty
PA by applying more power to the peak PA than to the carrier PA in
order to fully modulate the load impedance. This results in more
output power than the case in which the PAs are driven with the
same amount of power.
[0093] FIG. 6B illustrates one implementation of the PA system
presented in FIG. 6A. This MTM Doherty PA system includes two PAs,
617 and 619, coupled to a 2-way MTM power splitter 613 and a 2-way
MTM power combiner 615 such as the 2-way MTM power
combiners/splitters described in FIGS. 3A-3B and FIGS. 4A-4B. The
two PAs comprises two power amplifiers: one "main PA" 617 or
"carrier PA" and one "auxiliary PA" 619 or "peak PA". These MTM
power combiners/splitters may have a small footprint and low
losses, and, therefore, can enhance efficiency. In addition, these
MTM power combiner/splitters may also support multi-band
frequencies as described in the previous section and integrate
input matching network (IMN) and/or output matching network
(OMN).
[0094] FIG. 6C illustrates another implementation of the PA system
presented in FIG. 6A. In FIG. 6C, an N-way MTM Doherty PA system is
comprised of an N PAs 629, 631 coupled to an N-way MTM power
splitter 623 at its input and an N-way MTM power combiner 625 at
its output such as the N-way MTM power combiners/splitters
described in FIGS. 3A-3B and FIGS. 4A-4B. In this example, the PAs
are comprised of a single main or carrier amplifier 629 and (N-1)
peak or auxiliary amplifiers 631. An N-way Doherty PA may have the
ability to operate at a greater back-off while retaining high
efficiency and high linearity. By applying the MTM technology to
the Doherty PA system, the MTM Doherty PA system can be constructed
in a compact form and have multi-band properties. When this
architecture is unevenly driven, the output power of the system may
be increased due to the unevenly driven split. For example, the
auxiliary or (peak) amplifier 631, characterized by a switching
amplifier, turns ON only when there is a certain power applied to
the input of the switching amplifier 631. When the input power is
low, the switching amplifier 631 is turned OFF. Therefore, by using
unevenly driven splitters 623, the auxiliary amplifiers 631 can be
turned ON earlier or later than in the evenly driven case. The
impedance of each branch of the power splitter 623 may be matched
by selecting the parameters that defines the CRLH and by design to
the input impedance of the PA. The same is true for the power
combiner 625 located at the output. Each branch of the power
combiner 625 may be matched to the output impedance of the PAs 629,
631. It is also possible to use a series 90.degree. line at the
output of each PAs 629-631 as described in FIG. 14. The only
difference is the use of 90.degree. and 270.degree. instead of
0.degree. and 360.degree..
[0095] In yet another implementation of a PA system presented in
FIG. 6A, the N-way power splitter/combiner described in FIG. 6A can
be replaced with a 2-way MTM Wilkinson splitter/combiner as
described in FIG. 5A. However, the design may be extended to N-way
splitter/combiners such as those described in FIGS. 4A-4B and based
on the N-way MTM Wilkinson splitter/combiners described in FIG. 5B.
Examples of various PA architectures that may use the 2-way MTM
Wilkinson power splitter/combiners shown in FIG. 5A are illustrated
in FIGS. 7-10 and are described herein as follows.
[0096] In the MTM Doherty PA system shown in FIG. 7, the input
stage of the MTM Doherty PA system may be comprised of a 2-way MTM
Wilkinson splitter 701 as shown in FIG. 5A and described
previously. In this implementation, the Wilkinson splitter may
utilize an evenly divided splitter where k=1. Two PAs 705 and 707
are coupled to the output ports of the MTM Wilkinson splitter 701
in which the power is evenly divided into the input of a main
amplifier 705 and the input of an auxiliary amplifier 707.
Alternatively, each PA can be fed with an arbitrary amount of input
power which can be designed by selectively choosing and splitting
the input signal to the PAs 705, 707. The amplified signals from
each amplifier 705, 707 are fed into a output power combiner 709 in
which conventional RH components (713, and 717) can be used at the
output stage of the PA system.
[0097] The MTM Doherty PA system in FIG. 8 utilizes the same
splitter 701 and two PAs 705 and 707 shown in FIG. 7 and previously
described. In this implementation, the output power combiner 709
can be replaced with an MTM output power combiner 801 comprised of
CRLH-TLs. In contrast to the conventional case, the MTM components
at the output stage offer an increased bandwidth of the Doherty
amplifier due to a flatter phase slope.
[0098] The MTM Doherty PA system in FIG. 9 also utilizes the same
splitter 701 and two PAs 705 and 707 shown in FIG. 7 and previously
described. In this implementation, the conventional RH components
709 having a phase of +90 degrees are replaced with MTM quarter
wavelength components 901 at the output stage. The bandwidth of the
inverted Doherty may also be increased as a result of the MTM
components 901 supplied at the output stage.
[0099] In another implementation, the MTM Doherty PA system shown
in FIG. 10 is comprised of the same MTM Wilkinson splitter 701 and
two PAs 705 and 707 shown in FIG. 7 and previously described. In
this configuration, a signal from the main amplifier 705 and
another signal from the auxiliary amplifier 707 are coupled and fed
to corresponding input ports of a MTM Wilkinson combiner 1001.
[0100] One technique to build power amplifiers with enhanced
efficiency and linearity is known as the Envelope Elimination and
Restoration (EER). FIG. 11A illustrates an example of an EER system
1100. In the EER system 1100, an RF signal at an input port 600 is
split into two paths: an upper path 1101 and a lower path 1103. In
the upper path 1101, the RF signal at the input port 600 is fed
into an envelope detector 1101 for detecting an envelope of the
input signal. The envelope detector 1105 is in series with and
coupled to a pulse width modulator (PWM) 1107 for digitizing the
envelope signal from the detector 1105. The PWM 1107 is coupled to
a Class-S Modulator 1109 which receives and amplifies the digitized
envelope signal transmitted by PWM 1107. A low pass filter (LPF)
1111, which is coupled to the output of the Class-S Modulator 1109,
is used for recovering the desired frequency range to the bias
input of a conventional PA 1117. In the lower path 1103, the RF
signal at the input port 600 is fed into a limiter 1113 for
eliminating the amplitude modulation components and retaining the
phase portion of the signal. The limiter 1113 is further coupled to
a time delay 1115 for compensating delay of the modulated signal in
the upper path 1101. The time compensated signal at the output of
the time delay 1115 is fed into the conventional PA 1117 for
amplification to produce an output signal at the output port 607,
which is proportional to the RF input signal at the input port
600.
[0101] The EER architecture in FIG. 11A may suffer several
disadvantages. One disadvantage is switching losses coming from the
Class-S modulator 1109 which can increase when the frequency
increases. Another disadvantage is clipping problems occurring at
the pulse width modulator (PWM) 1107 caused by signals that have
large envelope variations and non-linearity originating at the
output portion of the envelope detector 1005. To address the large
envelope variations, one solution is to replace the pulse width
modulator (PWM) 1107, the Class-S modulator 1109, and low pass
filter 1111 with a delta-sigma modulator, which also rejects the
noise outside the band of interest. In addition, by including MTM
filters in the envelope delta-sigma modulated (EDSM) scheme, the
band pass filter can achieve a desired bandwidth having a lower
loss than with conventional filters. In addition, for this EER
architecture, a low pass MTM filter may be utilized. MTM PAs of
class-F, inverse class-F, or class-J, for example, can include an
integrated filter which is part of the output matching network
(OMN) of the PA. Such design can have the advantage of reducing
losses introduced when connecting to a conventional filter. High
efficiency may be obtained by utilizing a filter that is connected
at the output of the PA. This type of an MTM filter design with a
harmonic tuner can improve the amplifier's linearity.
[0102] In an exemplary implementation presented in FIGS. 11B-11D,
an MTM PA or another MTM circuit element is integrated in the
Envelope Elimination Restoration (EER) to enhance the EER.
[0103] For example, the EER system in FIG. 11B illustrates an RF
signal at an input port 600 that is split into two paths: an upper
path 1121 and a lower path 1123. In the upper path 1121, the RF
signal at the input port 600 is fed into an envelope detector 1105
for detecting an envelope of the input signal. Envelope detector
1105 is in series with and coupled to a delta-sigma modulator 1125
which digitizes the envelope signal from the detector 1105. The
delta-sigma modulator 1125 is coupled to a modulator 1127 that
combines the two paths where the output of the delta-sigma
modulator is recombined with the signal in the lower path 1123. In
the lower path 1123, the RF signal at the input port 600 is fed
into a limiter 1113 for eliminating the amplitude modulation
components and retaining only the phase portion of the RF signal.
The output of the limiter 1113 is coupled to a time delay 1115 for
compensating the delay of the modulated signal in the upper path
1121 so that the signals in the two paths are synchronized in phase
at the modulator 1127. The time compensated signal at the output of
the time delay 1115 is fed into modulator 1127 and is recombined
with the envelope signal in the upper path 1121. In this
implementation, the output signal at modulator 1127 is fed into an
MTM PA for amplification to produce an output signal at the output
port 607, which is proportional to the RF input signal at the input
port 600. In another implementation, the MTM PA 1129 can be
integrated with a harmonic tuner and a band pass filter which is
part of the output matching network of the PA. By integrating the
PA with other MTM components, the overall circuit size of the PA
can be reduced while improving the performance of the PA.
[0104] FIG. 11C illustrates an implementation of the conventional
EER system of FIG. 11A. In this implementation, the amplified RF
signal generated at the output of the PA 1117 can be coupled to an
MTM filter 1137. By including an MTM filter in the EER system of
FIG. 11A, a desired bandwidth can be achieved for the band pass
filter. In this example, the modulated scheme can be an envelope
delta-sigma modulated (EDSM) 1125 scheme or PWM/Class-S/LPF
modulated scheme (1107, 1109, 1111) as shown in FIG. 11A.
[0105] In FIG. 11D, the PA 1117 and MTM filter 1137 of FIG. 11C are
replaced by an MTM PA 1141. The MTM PA 1141 is a PA with a CRLH MTM
structure to enhance the PA performance and to reduce the PA
dimension. The MTM PA 1141 may also include an integrated filter.
Because the MTM PAs are designed as a block, the MTM PA 1141 can be
optimized with all the MTM components. This design integration
methodology can have several advantages, such as the ability to
reduce circuit size and improve overall performance of the PA. The
MTM PA can be designed as class-F, inverse class-F, or class-J
power amplifiers.
[0106] A MTM-based multi-PA system can also include an input port
that receives an input RF signal and multiple transmission lines
based on CRLH MTM structures and connected in series to receive the
input RF signal from the input port. Each transmission line has a
CRLH MTM structure to produce, at a given operating frequency or
resonance, a zero phase delay or a phase delay of n360.degree.
where n is a non-zero integer and including a branch output port
that splits a portion of the RF signal as a respective branch RF
signal for the transmission line and different transmission lines
producing different respective branch RF signals. This system
includes multiple power amplifiers that are coupled to the branch
output ports of the transmission lines, respectively where each
power amplifier receives and amplifies a respective branch RF
signal to produce an amplified branch RF signal. A power combiner
based on a CRLH MTM structure is coupled to receive the amplified
branch RF signals from the power amplifiers and to combine the
received amplified branch RF signals into a combined output RF
signal.
[0107] FIG. 12 shows one example of such a system where a series
fed parallel combining distributed amplifier includes zero-degree
CRLH TLs 1203. At the input of each transistor 1209 there may be a
zero degree CRLH TL 1203. All of these zero degree CRLH TLs form a
series zero degree CRLH TL which is terminated with a load 1205. An
MTM power combiner 1207 is coupled to the outputs of the
transistors 1209 to combine the amplified outputs into a single
output signal. The zero degree CRLH TL 1203 and the MTM power
combiner 1207 can be designed to provide multi-band operations and
optimize the matching and power transfer in multiple bands. In
addition, the zero degree CRLH TL 1203 provides filtering of 2nd
and 3rd harmonic frequencies because the characteristic impedance
can be a function of the signal frequency. Therefore, the
efficiency of the structure shown in FIG. 12 may be enhanced in
comparison to some other PA structures.
[0108] In yet another implementation shown in FIG. 13, a series fed
parallel combining distributed amplifier may include a zeroth order
resonator. In this implementation, there may be a zeroth order
resonator at the input 600 which provides a stationary wave at the
input in the resonator with a filtering effect and no energy
dissipated at the load 1205 as in the previous case. As a result, a
better efficiency and a better linearity may be obtained.
[0109] The exemplary implementations illustrated in FIGS. 14 and 15
depict the zero degree CRLH TL and the zeroth order resonator used
in FIGS. 12 and 13, respectively. Under these designs, a dual-band
or multi-band main CRLH transmission line is structured to exhibit,
at least, a first phase at a first signal frequency f1 and a second
phase at a second, different signal frequency f2. This main CRLH
transmission line includes CRLH unit cells coupled in series and
each CRLH unit cell has a first electrical length that is a
multiple of +/-180 degrees at the first signal frequency and a
second, different electrical length that is a different multiple of
+/-180 degrees at the second signal frequency. Two or more branch
CRLH feed lines are connected at different locations on the CRLH
transmission line to combine signals in the CRLH feed lines into
the CRLH transmission line or to divide a signal in the CRLH
transmission line into different signals to the CRLH feed lines.
Each branch CRLH feed line includes at least one CRLH unit cell
that exhibits a third electrical length that is an odd multiple of
+/-90 degrees at the first signal frequency and a fourth, different
electrical length that is a different odd multiple of +/-90 degrees
at the second signal frequency. As illustrated, each CRLH feed line
1020 is connected to a location between two adjacent CRLH unit
cells or at one side of a CRLH unit cell.
[0110] The device in FIG. 14 includes a dual-band main CRLH
transmission line 1410 with dual-band CRLH TL unit cells 1412 and
branch CRLH feed lines 1420. Each unit cell 1412 is designed to
have an electrical signal length equal to a phase of zero degree at
the first signal frequency f1 and a second electrical signal length
equal to a phase of 360 degrees at the second signal frequency f2.
Each branch CRLH feed line 1420 includes one or more CRLH unit
cells and is configured as a dualband CRLH TL quarter wavelength
transformer. The optimum impedances are transformed via the CRLH TL
quarter wavelength transformer 1420 of a length L at 2 different
frequencies, f1 and f2. In this particular example, each CRLH feed
line 1420 is designed to have a phase of 90.degree. (.lamda./4)
[module .pi.] at the first signal frequency f1 and a phase of
270.degree. (3.lamda./4) [module .pi.] at the second signal
frequency f2. This device has 0 degree phase difference at one
frequency and 360.degree. at another frequency between each
port.
[0111] The device in FIG. 15 illustrates a dual-band resonator
serial power combiner/divider. This dual-band CRLH TL performs as a
resonator by being terminated with an open ended. The output/input
ports (port1-N) can be matched to 50.OMEGA., while the other ports
are match to optimum impedances. These optimum impedances are
transformed via a CRLH TL quarter wavelength transformer of length
L at 2 different frequencies, f1 and f2. By way of example f1 has a
phase of 90.degree. (.lamda./4) [modulo .pi.] while f2 has a phase
of 270.degree. (3.lamda./4) [modulo .pi.].
[0112] The two signal frequencies f1 has f2 do not have a harmonic
frequency relationship with each other. This feature can be used to
comply with frequencies used in various standards such as the 2.4
GHz band and the 5.8 GHz in the Wi-Fi applications. In this
configuration, the port position and the port number along the
dual-band CRLH TL 1410 can be selected as desired because of the
zero degree spacing at f1 and 360.degree. at f2 between each
port.
[0113] In another implementation shown in FIG. 16, an MTM
amplifying antenna is comprised of a serial zeroth order resonator
power divider 1601 at the input of each transistor 1605 and a
zeroth order resonating antenna 1603 at the output of each
transistor 1605. Therefore, in this architecture, the output
signals are combined in the zeroth order resonating antenna without
a power combiner. U.S. Pat. Nos. 7,482,893 and 7,330,090 disclose
examples of zeroth order resonating antennas and power dividers
which can be used to implementing the design in FIG. 16 and are
incorporated by reference as part of the disclosure of this
document. In other implementations, the antenna 1603 may be
implemented by a leaky wave antenna.
[0114] The MTM technology can be used to provide broadband or
multi-band power combiner/splitters in compact packages. Some
implementations can use 3-dB power combiner/splitters to decrease
losses in the MTM balanced PA, thereby improving the overall
efficiency of the system.
[0115] In the example shown in FIG. 17, a balanced PA is comprised
of a quadrature coupler such as an MTM branch line coupler 1701,
two identical PAs (1702, 1703), and an MTM branch line coupler
1705. The RF signal is received at the input port 600 of the MTM
branch line coupler 1701 and split equally into two outputs 1711
having a 90.degree. phase difference. The signals at two outputs
1711 are fed into PA1 1702 and PA2 1703. The remaining port of the
MTM branch line coupler 1701 is terminated with a resistor R 1707.
The outputs of the PA1 1702 and PA2 1703 are connected to two
inputs 1713 of the MTM branch line coupler 1705. One output of the
MTM branch line coupler 1705 is used as the RF output 607 and the
other one is terminated by using a resistor R 1709.
[0116] The advantage of using the quadrature coupler at the input
is that the reflected signals caused by the impedance mismatch at
inputs of the PAs can return to the RF input port in anti-phase.
Therefore, the reflected signals are canceled, and the input
voltage standing wave ratio (VSWR) may be better than the one
without the quadrature coupler.
[0117] The same reason generally applies to the usage of a
quadrature coupler at the outputs of the PAs. The output VSWR can
be improved by using other quadrature couplers such as, for
example, a microwave branch line coupler or a Lange coupler.
However, the conventional microwave branch line coupler only
provides a narrow band and is generally bulky, while the Lange
coupler requires complicated fabrication processes such as wire
bonding or microwave bridge.
[0118] The PA systems can also be designed to support either a wide
operational bandwidth or at least two bands.
[0119] In one example shown in FIG. 18, a multi-band MTM branch
line coupler includes four CRLH-TL branches, where two ends of the
CRLH-TL1 1801, 1803 are connected to the CRLH-TL2 1805, 1807 and
two ends of the CRLH-TL2 1805, 1807 are connected to the CRLH-TL1
1801, 1803. CRLH-TL1 1801, 1803 has phases of .theta.1 at f1 and
.theta.2 at f2 while CRLH-TL2 1805, 1807 has phases of .theta.3 at
f1 and .theta.4 at f2, where f2 is larger than f1. The .theta.1,
.theta.2, .theta.3 and .theta.4 have to satisfy the phase
requirement listed in FIG. 18 in order to provide a 3 dB power
division and quadrature phase between two outputs. In addition, the
characteristic impedance of CRLH-TL1 1801, 1803 and CRLH-TL2 1805,
1807 are 35.35.OMEGA. and 50.OMEGA., respectively. By using MTM
technology, these branch line couplers can be made smaller in size
as compared to the conventional branch line couplers.
[0120] FIG. 19 illustrates an exemplary dispersion diagram of a
CRLH-TL, which may be a nonlinear curve and may have zero phase
delay at a non-DC frequency. As a result, the phase advance/delay
of .theta.1 and .theta.2 can be arbitrarily chosen at arbitrary
frequencies of f1 and f2.
[0121] PA systems with a wide operational bandwidth can use a
branch line coupler with a wide bandwidth. FIG. 20A shows an
example where a broadband branch line coupler includes four
CRLH-TLs 2011, 2013, 2015, 2017 coupled to form a 4-port coupler.
In one implementation, P1 2001 is the input and P2 2002 and P3 2003
are the two outputs, and P4 2004 can be designed to handle
reflection or to be isolated from the other ports. Due to the
symmetry of the branch line coupler, the input and output ports can
be used interchangeably. By choosing .theta.1=-90.degree. and
.theta.2=+90.degree., the branch line coupler may provide broader
bandwidth as compared to the conventional branch line coupler.
[0122] FIG. 20B illustrates a comparison of the return loss and
insertion loss between the broadband MTM branch line coupler and
conventional branch line coupler. In comparison to the conventional
case, the MTM branch line coupler covers a broader frequency range
in both return loss and insertion loss responses. FIG. 20C also
affirms that the bandwidth of the phase difference between |S21|
and |S31| is wider for the MTM branch line coupler than the
conventional branch line coupler.
[0123] FIG. 21 illustrates another implementation of the MTM
broadband coupler known as a planar MTM forward-wave (FW)
directional coupler. Examples for such an MTM broadband coupler re
described in the U.S. patent application Ser. No. 12/340,657 which
is incorporated by reference as part of this document. This planar
MTM FW directional coupler is implemented by cascading two coupled
metamaterial cells horizontally. The coupled metamaterial cell is
realized by paralleling two metamaterial unit cells, for example,
2100-1 and 2100-2, with an additional inductor L.sub.m1 connecting
between the two cells. Each metamaterial unit cell 2100 comprises
two transmission lines, two series capacitors of 2C.sub.L and one
shunt inductor of L.sub.L. In this exemplary implementation shown
in FIG. 21, the two transmission lines associated with an input
port, Port 1 2101, are represented by 2105 and 2107. The two
transmission lines associated with a transmission port, Port 2
2102, are represented by 2115 and 2117. The two transmission lines
associated with a coupling port, Port 4 2104, are represented by
2111 and 2113. The two transmission lines associated with an
isolation port, Port 3 2103, are represented by 2109 and 2119. The
mutual inductor and capacitor of L.sub.m and C.sub.m are introduced
when two transmission lines of each unit cell are close to each
other. See transmission lines 2107 and 2109, for example. These two
transmission lines may possess the intrinsic series inductance of
L.sub.R along the line and the shunt capacitance C.sub.R between
the lines and the ground. This planar MTM FW directional coupler
can provide a wide band of return loss and 3 dB insertion loss at
each output port. The planar MTM FW directional coupler described
above can be implemented in the balanced power amplifier for the
input and output sections.
[0124] FIG. 22A-22B illustrates another implementation of the MTM
coupler known as a vertical MTM FW directional coupler. Examples of
this vertical MTM FW directional coupler are also described in the
U.S. patent application Ser. No. 12/340,657. The FW coupler in this
implementation may be constructed by cascading two coupled
metamaterial cells. In this exemplary implementation, the coupled
metamaterial cell is built by paralleling two metamaterial
transmission lines 2201, 2203 vertically with an additional
inductor L.sub.m1 2231 connecting between the two metamaterial
transmission lines which indicates one metamaterial transmission
line 2201 is on top of the substrate and the other metamaterial
transmission line 2203 is on the bottom of the substrate. The
cross-sectional view of this MTM FW coupler is shown in FIG. 22B.
Each metamaterial transmission line 2201, 2203 includes two
metamaterial unit cells. Each unit cell comprises two sections of
transmission line, two series capacitors of 2C.sub.L and one shunt
inductor of L.sub.L. The vertically coupled transmission lines
provide mutual inductance L.sub.m and mutual capacitance C.sub.m.
In addition, each port of the metamaterial coupled lines is
connected to the 50.OMEGA. CPW 2221 through a CPW bend. In this
implementation, there are a total of four CPW lines 2221 and four
CPW bends 2209. The MTM FW coupler in this example may also provide
a broad bandwidth of return loss and 3 dB insertion loss at each
output port. The vertical MTM FW directional coupler can be used in
the balanced power amplifier for the input and output sections.
[0125] Linear amplification using non-linear components (LINC) is
formed by adding two signals vectorialy to achieve power
amplification. In the exemplary implementation presented in FIG.
23, a LINC architecture includes MTM LINC (non-linear) PAs 2305
coupled to an N-way MTM Power Splitter 2301 at the input stage and
N-way MTM Power Combiner 2303 at the output stage. Alternatively,
conventional LINC PAs can be used. MTM PAs can support multi-band
RF signals with its compact size and provide low loss, resulting in
high efficiency. One disadvantage of conventional LINC amplifiers
is the complexity of the hardware; some applications require
extensive signal processing, which makes the LINC architecture
bulky and expensive. The MTM PAs may reduce the complexity of the
hardware and provide broadband with high efficiency. The MTM can
achieve a flat slope for the phase in a certain range of
frequencies. In other words, the same phase can be achieved at
different frequencies which can improve the phase matching of the
combined PAs.
[0126] In an exemplary implementation of a phase combining system,
shown in FIG. 24, different MTM non-linear PAs 2403 may be fed with
different signals and different phases, which may be combined in
phase with an N-way MTM power combiner 2405 or other power
combiners such as an MTM Wilkinson power combiner shown in FIG.
5A-5B and previously described. Each PA is fed with an RF input
signal. In this configuration, the use of MTM structures can be
designed to allow a certain frequency to pass while blocking other
frequencies. Therefore, the PA architecture of FIG. 24 can
implement this design when input signals have different frequency
bands or a single frequency band.
[0127] While this document contains many specifics, these should
not be construed as limitations on the scope of any invention or of
what may be claimed, but rather as descriptions of features
specific to particular embodiments. Certain features that are
described in this document in the context of separate embodiments
can also be implemented in combination in a single embodiment.
Conversely, various features that are described in the context of a
single embodiment can also be implemented in multiple embodiments
separately or in any suitable subcombination. Moreover, although
features may be described above as acting in certain combinations
and even initially claimed as such, one or more features from a
claimed combination can in some cases be excised from the
combination, and the claimed combination may be directed to a
subcombination or variation of a subcombination.
[0128] Thus, particular implementations have been described.
Variations and enhancements of the described implementations and
other implementations can be made based on what is described and
illustrated.
* * * * *