Closed loop active cancellation technique (ACT) - based RF power amplifier linearization architecture

• US 20020084845A1
• Filed: 12/20/2001
• Published: 07/04/2002
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Spectrian Corp. (REMEC, Inc.)
• Inventors: Avis, Steve, Eisenberg, John
• Granted Patent: US 6,452,446 B1
• Time in Patent Office: Days
• US Class Current: 330/52
• CPC Class Codes: H03F 1/3235 using a pilot signal

Abstract

A closed loop, active cancellation technique (ACT)-based RF power amplifier linearization architecture injects a pilot tone as a ‘pseudo distortion’ signal into signal paths through first and second matched RF amplifiers, and a set of power minimization loops are closed around the RF amplifier pair. The power minimizing control loops control a set of vector modulators such that both the injected pilot tone and intermodulation distortion products are canceled, while RF carrier components constructively sum in the composite output of the two RF amplifiers.

Claims

1. An RF power amplifier apparatus comprising:

an RF input port to which an RF input signal is applied;

an RF output port from which an amplified RF output signal is derived;

first and second RF signal processing paths coupled between said input and output ports and containing first and second RF power amplifiers;

said first RF signal processing path including a first RF signal vector modulator, that is adapted to controllably adjust a first RF signal component of said RF input signal applied to said first RF power amplifier;

said second RF signal processing path including an intermodulation distortion (IMD) extraction circuit coupled to an output of said first RF power amplifier and to said RF input port, and including a second RF signal vector modulator adapted to controllably adjust said RF input signal, and a third RF signal vector modulator adapted to controllably adjust an IMD component present in an amplified RF output signal from said first RF power amplifier, and to generate a second RF signal component as a combination of a controllably adjusted RF input signal and said controllably adjusted IMD component;

an output signal combiner coupled to outputs of said first and second RF power amplifiers and to said output port, and being operative to produce said RF output signal as a composite of said first and second RF signal components, in which RF carrier components produced by said first and second RF power amplifiers constructively sum and IMD components produced thereby destructively combine; and

a vector modulator controller, which is adapted to control said first, second and third vector modulators independently of one another.

2. The RF power amplifier apparatus according to claim 1, wherein said first and second RF power amplifiers are matched RF power amplifiers.

3. The RF power amplifier apparatus according to claim 1, wherein said vector modulator controller is adapted to control one of said vector modulators based upon power minimization at a signal port of said output signal combiner.

4. The RF power amplifier apparatus according to claim 3, wherein said vector modulator controller is adapted to control said first vector modulator based upon power minimization of carrier energy leakage in said output signal combiner.

5. The RF power amplifier apparatus according to claim 1, wherein said IMD extraction circuit includes a cancellation combiner that is operative to differentially combine a sample of the amplified RF output signal produced by said first RF power amplifier with a portion of said RF input signal to derive said IMD component, and to combine said IMD component with said RF input signal applied to said second signal processing path, to produce said second RF signal component as a combination of said RF input signal and said IMD component, where said IMD component is phase-inverted with respect to a carrier component at the output of the first RF power amplifier.

6. The RF power amplifier apparatus according to claim 5, wherein said vector modulator controller is adapted to control said third vector modulator based upon power minimization of monitored distortion energy the output of said carrier cancellation combiner.

7. The RF power amplifier apparatus according to claim 1, further including a pilot tone generator, which is operative to inject a first pilot tone into the signal path through said first RF power amplifier, and a second pilot tone into the signal path through said second RF power amplifier, and wherein said vector modulator controller includes a pilot tone receiver coupled to said output port of said output signal combiner, and being adapted to control said third vector modulator based upon pilot tone energy in said output port of said output signal combiner.

8. The RF power amplifier apparatus according to claim 7, wherein said vector modulator controller is adapted to control said second vector modulator based upon pilot tone energy in the composite output of said output signal combiner.

9. The RF power amplifier apparatus according to claim 8, wherein said second pilot tone has the same frequency as, but complementary phase with respect to, said first pilot tone.

10. The RF power amplifier apparatus according to claim 1, further including a feed-forward RF amplifier loop coupled to said first RF signal processing path and said output port, and being operative to provide an amplified RF distortion output signal containing distortion introduced by said first and second RF amplifiers, but effectively excluding said RF input signal, and wherein said output signal combiner is coupled to said feed-forward amplifier loop and is operative to combine said amplified RF distortion output signal with said RF output signal to produce a refined RF output signal.

11. The RF power amplifier apparatus according to claim 10, further including a fourth vector modulator coupled with said first RF signal processing path and being adapted to controllably adjust said first RF signal component of said RF input signal applied to said first RF power amplifier, and wherein said feed-forward RF amplifier loop includes a fifth vector modulator adapted to controllably adjust said amplified RF distortion output signal, and wherein said vector modulator controller is adapted to control said fourth and fifth vector modulators independently of one another and independently of said first, second and third vector modulators.

12. The RF power amplifier apparatus according to claim 11, wherein said vector modulator controller is adapted to control said fourth vector modulator based upon power minimization at a signal port of said signal combiner.

13. The RF power amplifier apparatus according to claim 12, wherein said vector modulator controller is adapted to control said fifth vector modulator based upon pilot tone energy in the composite output of said output signal combiner.

15. The RF power amplifier apparatus according to claim 14, wherein said first pilot tone has the same frequency as, but complementary phase with respect to, said second pilot tone.

16. The RF power amplifier apparatus according to claim 14, further including a feed-forward RF amplifier loop coupled to said first RF signal processing path and said output port, and being operative to provide an amplified RF distortion output signal containing distortion introduced by said first and second RF amplifiers, but effectively excluding said RF input signal, and wherein said output signal combiner is coupled to said feed-forward amplifier loop and is operative to combine said amplified RF distortion output signal with said RF output signal to produce a refined RF output signal.

17. The RF power amplifier apparatus according to claim 16, further including a fourth vector modulator coupled with said first RF signal processing path and being adapted to controllably adjust said first RF signal component of said RF input signal applied to said first RF power amplifier, and wherein said feed-forward RF amplifier loop includes a fifth vector modulator adapted to controllably adjust said amplified RF distortion output signal, and wherein said vector modulator controller is adapted to control said fourth and fifth vector modulators independently of one another and independently of said first, second and third vector modulators.

18. The RF power amplifier apparatus according to claim 17, wherein said vector modulator controller is adapted to control said fourth vector modulator based upon power minimization of a signal port of said output signal combiner, and said fifth vector modulator based upon pilot tone energy in the composite output of said output signal combiner.

20. The method according to claim 19, further including the step (j) of coupling a feed-forward RF amplifier loop coupled to said first RF signal processing path and said output port, and being operative to provide an amplified RF distortion output signal containing distortion introduced by said first and second RF amplifiers, but effectively excluding said RF signal, and wherein said step (h) further includes combining said amplified RF distortion output signal with said RF output signal to produce a refined RF output signal.

14. An RF power amplifier apparatus comprising:

an RF input port;

an RF output port;

a first RF signal processing path coupled between said RF input and output ports and containing a first RF power amplifier, and a first RF signal vector modulator, that is adapted to controllably adjust a first RF signal component of an RF input signal coupled to said RF input port;

a second RF signal processing path coupled between said input and output ports and containing a second RF power amplifier, that is effectively matched with said first RF power amplifier, and an intermodulation distortion (IMD) extraction circuit coupled to an output of said first RF power amplifier and to said RF input port, said second RF signal processing path including a second RF signal vector modulator, that is adapted to controllably adjust said RF input signal, and a third RF signal vector modulator, that is adapted to controllably adjust said IMD component, and to generate a second RF signal component as a combination of a controllably adjusted RF input signal and a controllably adjusted IMD component present in an amplified RF output signal from said first RF power amplifier;

an output signal combiner coupled to outputs of said first and second RF power amplifiers and to said output port, and being adapted to produce said RF output signal as a composite of said first and second RF signal components, in which RF carrier components produced by said first and second RF power amplifiers constructively sum and IMD components destructively combine;

a pilot tone generator, which is operative to inject a first pilot tone into the signal path through said first RF power amplifier and a second pilot tone into the signal path through said second RF power amplifier; and

a vector modulator controller, which is adapted to control said first vector modulator based upon power minimization of carrier energy in a carrier cancellation path of said intermodulation distortion (IMD) extraction circuit, said second vector modulator based upon leakage energy in a terminated output port of said output signal combiner, and said third vector modulator based upon power minimization of monitored pilot tone energy at the output of said carrier cancellation combiner.

19. A method of amplifying an RF signal comprising the steps of:

(a) applying said RF signal to a first RF signal processing path containing a first RF power amplifier;

(b) controllably adjusting said RF signal applied to said first RF power amplifier;

(c) combining said RF signal and a first amplified RF output signal from said first RF signal amplifier in a carrier cancellation path to produce a distortion signal containing distortion in said first amplified RF output signal;

(d) controllably adjusting said distortion signal to produce an adjusted distortion signal;

(e) controllably adjusting said RF signal to produce a further adjusted RF signal;

(f) combining said adjusted distortion signal with said further adjusted RF signal to produce a distorted RF signal;

(g) coupling said distorted RF signal to a second signal processing path containing a second RF power amplifier, that is effectively matched with said first RF power amplifier;

(h) combining said first amplified RF output signal from said first RF power amplifier with a second amplified RF output signal from said second RF power amplifier to produce at an output port an RF output signal in which RF carrier components produced by said first and second RF power amplifiers constructively sum and distortion components destructively combine; and

(i) injecting a first pilot tone into said first signal path through said first RF power amplifier and a second pilot tone into said second signal path through said second RF power amplifier; and

wherein

step (b) comprises controllably adjusting said RF signal applied to said first RF power amplifier based upon power minimization of carrier energy in said carrier cancellation path,

step (d) comprises controllably adjusting said distortion signal based upon power minimization of monitored pilot tone energy in said RF output signal produced in step (h), and

step (e) comprises controllably adjusting said RF signal to produce said further adjusted RF signal based upon leakage energy produced in step (h).