RF power amplifier system with impedance modulation

• US 7,782,134 B2
• Filed: 02/05/2009
• Issued: 08/24/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Quantance, Inc. (Skyworks Solutions Incorporated)
• Original Assignee: Quantance, Inc. (Skyworks Solutions Incorporated)
• Inventors: Drogi, Serge Francois, Vinayak, Vikas
• Primary Examiner(s): Nguyen; Khanh V
• Application Number:
  US12/366,568
• Publication Number:
  US 20100060357A1
• Time in Patent Office: 565 Days
• Field of Search: 330/127, 330/129, 330/136, 330/297, 330/302
• US Class Current: 330/136
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0238 using supply converters
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 2200/99 A diode as rectifier being used as a detecting circuit in an amplifying circuit
• CPC Class Codes: H03F 2201/3231 Adaptive predistortion using phase feedback from the output of the main amplifier
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H

Abstract

A power amplifier controller circuit controls an adjustable impedance matching network at the output of a power amplifier to vary its load line to improve the efficiency of the RF PA. The PA controller circuit comprises an amplitude control loop that determines an amplitude correction signal. The amplitude loop is configured to control or correct for distortion from the adjustable matching network based upon the amplitude correction signal.

Claims

1. A radio frequency (RF) power amplifier circuit, comprising:

a power amplifier coupled to receive and amplify an RF input signal to generate an RF output signal;

a power amplifier controller including an amplitude control loop determining an amplitude correction signal indicative of an amplitude difference between an amplitude of the RF input signal and an attenuated amplitude of the RF output signal; and

an adjustable matching network coupled to an output of the power amplifier, the amplitude control loop controlling the adjustable matching network to adjust a load line of the power amplifier based on the amplitude correction signal.

2. The RF power amplifier circuit of claim 1, wherein the amplitude control loop controls the adjustable matching network to adjust the load line of the power amplifier to allow the power amplifier to operate in a compressed region.

3. The RF power amplifier circuit of claim 1, further comprising a power supply generating an adjusted supply voltage provided to the power amplifier based upon the amplitude correction signal.

4. The RF power amplifier circuit of claim 3, wherein the power supply is a switch-mode type.

5. The RF power amplifier circuit of claim 3, wherein:

the power supply receives a first portion of the amplitude correction signal in a first frequency range and generates an adjusted supply voltage provided to the power amplifier based upon the first portion of the amplitude correction signal; and

the adjustable matching network receives a second portion of the amplitude correction signal in a second frequency range and adjusts the load line of the power amplifier based upon the second portion of the amplitude correction signal.

6. The RF power amplifier circuit of claim 5, wherein the first frequency range includes frequencies lower than the lowest frequencies of the second frequency range.

7. The RF power amplifier circuit of claim 3, wherein an average of the adjusted supply voltage of the power supply is set such that the power amplifier operates in a compressed region.

8. The RF power amplifier circuit of claim 3, further comprising:

a phase control loop determining a phase error signal indicative of a phase difference between phases of the RF input signal and the RF output signal and adjusting the phase of the RF input signal to reduce phase distortion generated by the RF power amplifier circuit.

9. The RF power amplifier circuit of claim 1, further comprising at least a gain element for adjusting gain within the amplitude control loop, and wherein:

the adjustable matching network receives a first portion of the amplitude correction signal and adjusts the load line of the power amplifier based upon the first portion of the amplitude correction signal; and

the gain element receives a second portion of the amplitude correction signal and controls the gain within the amplitude control loop based upon the second portion of the amplitude correction signal; and

wherein

the gain element responds to the amplitude correction signal at a rate at least equal to a rate of modulation of the RF input signal.

10. The RF power amplifier circuit of claim 9, wherein the power amplifier operates in both a compressed and linear region.

11. The RF power amplifier circuit of claim 9, wherein an average gain of the gain element is set separately by a DC control signal instead of the amplitude correction signal.

12. The RF power amplifier circuit of claim 9, wherein an average gain of the gain element is set based on a distortion level of the RF output signal.

13. The RF power amplifier circuit of claim 9, wherein an average load line of the adjustable matching network is set separately by a DC control signal instead of the amplitude correction signal.

14. The RF power amplifier circuit of claim 9, wherein an average load line of the adjustable matching network is set based on a distortion level of the RF output signal.

15. The RF power amplifier circuit of claim 9, wherein the gain element is a variable gain amplifier coupled between the RF input signal and the power amplifier.

16. The RF power amplifier circuit of claim 9, wherein the gain element corresponds to a bias adjustment for the power amplifier or a variable gain amplifier internal to the power amplifier.

17. The RF power amplifier circuit of claim 9, wherein the gain element is a power supply supplying power to the power amplifier.

18. The RF power amplifier circuit of claim 9, further comprising

a phase control loop determining a phase error signal indicative of a phase difference between phases of the RF input signal and the RF output signal and adjusting the phase of the RF input signal to reduce phase distortion generated by the RF power amplifier circuit.

19. The RF power amplifier circuit of claim 9, further comprising a power supply generating an adjusted supply voltage provided to the power amplifier based upon the amplitude correction signal, and wherein:

the power supply receives a first portion of the amplitude correction signal in a first frequency range and generates the adjusted supply voltage provided to the power amplifier based upon the first portion of the amplitude correction signal; and

the adjustable matching network receives a second portion of the amplitude correction signal in a second frequency range and adjusts the load line of the power amplifier based upon the second portion of the amplitude correction signal; and

the gain element receives a third portion of the amplitude correction signal in a third frequency range and adjusts the gain within the amplitude control loop based upon the third portion of the amplitude correction signal; and

wherein the first frequency range includes frequencies lower than the lowest frequencies of the second frequency range or the third frequency range.

20. A radio frequency (RF) power amplifier circuit, comprising:

a power amplifier coupled to receive and amplify an RF input signal to generate an RF output signal;

a power amplifier controller including an amplitude control loop determining an amplitude correction signal indicative of an amplitude difference between an amplitude of the RF input signal and an attenuated amplitude of the RF output signal;

a gain element receiving the amplitude correction signal and controlling a gain within the amplitude control loop based upon the amplitude correction signal; and

an adjustable matching network coupled to an output of the power amplifier, the adjustable matching network adjusting a load line of the power amplifier based on an amplitude of an RF signal within the amplitude control loop.

21. The RF power amplifier circuit of claim 20, further comprising:

a low pass filter receiving an amplitude signal indicative of the amplitude of the RF input signal to provide a control signal indicative of an average of the amplitude of the RF input signal to the adjustable matching network, the adjustable matching network adjusting the load line of the power amplifier based on the average of the amplitude of the RF input signal.

22. The RF power amplifier circuit of claim 21, wherein the adjustable matching network adjusts the load line of the power amplifier based on a distortion level of the RF output signal instead of the average of the amplitude of the RF input signal.

23. The RF power amplifier circuit of claim 22, wherein the distortion level of the RF output signal comprises a ratio of a first output power of a first portion of the RF output signal outside a desired frequency channel to a second output power of a second portion of the RF output signal within the desired frequency channel.

24. The RF power amplifier circuit of claim 20, further comprising:

a phase control loop determining a phase error signal indicative of a phase difference between phases of the RF input signal and the RF output signal and adjusting the phase of the RF input signal to reduce phase distortion generated by the RF power amplifier circuit.