Digital hybrid mode power amplifier system

• US 8,811,917 B2
• Filed: 04/23/2008
• Issued: 08/19/2014
• Est. Priority Date: 05/01/2002
• Status: Expired due to Term

• Current Assignee: Dali Systems Co., Ltd.
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Kim, Wan Jong, Cho, Kyoung Joon, Stapleton, Shawn Patrick, Kim, Jong Heon, Yang, Dali
• Primary Examiner(s): Jain, Ankur
• Application Number:
  US12/108,502
• Publication Number:
  US 20080265996A1
• Time in Patent Office: 2,309 Days
• Field of Search: 455/424, 455/425, 455/456.5, 455/456.6, 455/561, 455/550.1, 455/575.1, 455/63.1, 455/67.13, 455/114.3, 455/114.2, 455/127.3, 455/127.1, 455/69, 455/126, 330/129, 330/149, 330/266, 330/265, 330/267, 330/271, 330/272, 330/289, 375/296, 375/297
• US Class Current: 455/114.3
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 2200/129 there being a feedback over the complete amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3227 Adaptive predistortion based on amplitude, envelope or power level feedback from the output of the main amplifier
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/20 Power amplifiers, e.g. Class B amplifiers, Class C amplifiers H03F3/26 - H03F3/30 take precedence
• CPC Class Codes: H03F 3/24 of transmitter output stages

Abstract

A RF-digital hybrid mode power amplifier system for achieving high efficiency and high linearity in wideband communication systems is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier in the RF domain. The power amplifier characteristics such as variation of linearity and asymmetric distortion of the amplifier output signal are monitored by the narrowband feedback path and controlled by the adaptation algorithm in a digital module. Therefore, the present invention could compensate the nonlinearities as well as memory effects of the power amplifier systems and also improve performances, in terms of power added efficiency, adjacent channel leakage ratio and peak-to-average power ratio. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels. As a result, the digital hybrid mode power amplifier system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems, where baseband I-Q signal information is not readily available.

Claims

1. A digital hybrid mode power amplifier system comprising:

a down-converted RF input;

a multi-channel digital input;

a digital predistortion module for receiving at least one of the down-converted RF input or multi-channel digital input, wherein the digital predistortion module utilizes a predistortion polynomial;

a power amplifier portion responsive to signals representative of an output of the digital predistortion module;

a down-converted feedback portion adapted to monitor signals representative of adjacent channel power for feeding back to the digital predistortion module signals representative of an output of one or more channels of the power amplifier portion, in response to which the digital predistortion module computes the predistortion polynomial and modifies its output to reduce adjacent channel power level; and

wherein the digital predistortion module searches locations of a main channel signal to determine a value representative of adjacent channel power, and implements a multi-directional search algorithm comprising evaluation, rotation, expansion, and contraction using the adjacent channel power value or an adjacent channel power ratio as an evaluation function to develop coefficients for modifying its output.

2. The digital hybrid mode power amplifier system of claim 1 wherein the digital predistortion module comprises at least one of a digital field programmable gate array, digital-to-analog converters, analog-to-digital converters, or a phase-locked loop.

3. The digital hybrid mode power amplifier system of claim 2 wherein:

the power amplifier system is configured for base station applications, and

the digital field programmable gate array comprises at least one of a digital up-converter, a crest factor reduction, a predistorter, or a digital quadrature modulator.

4. The digital hybrid mode power amplifier system of claim 2 wherein:

the power amplifier system is configured for repeater applications, and

the digital field programmable gate array comprises at least one of a digital quadrature demodulator, a crest factor reduction, a predistorter, or a digital quadrature modulator.

5. The digital hybrid mode power amplifier system of claim 2 wherein the digital field programmable gate array provides predistortion that compensates adaptively for both nonlinearity and memory effects of the power amplifier portion by generating asymmetric distortion of a power amplifier.

6. The digital hybrid mode power amplifier system of claim 5 wherein the adaptive compensation for predistortion further comprises:

updating coefficients by detecting adjacent channel powers; and

using the adjacent channel power in performing an evaluative function.

7. The digital hybrid mode power amplifier system of claim 2 wherein the digital field programmable gate array comprises an adaptation algorithm to determine an optimum gate bias voltage of a power amplifier for stabilizing linearity fluctuations due to temperature changes of the power amplifier.

8. The digital hybrid mode power amplifier system of claim 1 wherein the power amplifier portion comprises at least one of an up-converter for real signal and an analog quadrature modulator for real and complex signals, a high power amplifier with multi-stage drive amplifiers, or a temperature sensor.

9. The digital hybrid mode power amplifier system of claim 8 wherein the power amplifier portion uses efficiency boosting techniques comprising at least one of Doherty, Envelope Elimination and Restoration, Envelope Tracking, Envelope Following, or Linear amplification using Nonlinear Components.

10. The digital hybrid mode power amplifier system of claim 1 wherein the down-converted feedback portion comprises at least one of a directional coupler, a mixer, a low pass filter, gain amplifiers, a band pass filter, or detectors.

11. The digital hybrid mode power amplifier system of claim 1 wherein in-band distortion resulting from a clipped signal at the output of the power amplifier portion caused by crest factor reduction is compensated by a DAC and UPC responsive to an output of the digital predistortion module.

12. A digital hybrid mode power amplifier system comprising:

a digital predistortion module for receiving multi-channel digital input, wherein the digital predistortion module utilizes a predistortion polynomial;

a power amplifier portion responsive to signals representative of an output of the digital predistortion module;

a down-converted feedback portion adapted to monitor signals representative of adjacent channel power for feeding back to the digital predistortion module signals representative of an output of one or more channels of the power amplifier portion, in response to which the digital predistortion module computes the predistortion polynomial and modifies its output to reduce adjacent channel power level; and

wherein the digital predistortion module searches locations of a main channel signal to determine a value representative of adjacent channel power, and implements a multi-directional search algorithm comprising evaluation, rotation, expansion, and contraction using the adjacent channel power value or an adjacent channel power ratio as an evaluation function to develop coefficients for modifying its output.

13. The digital hybrid mode power amplifier system of claim 12 wherein the digital predistortion module comprises at least one of a digital field programmable gate array, digital-to-analog converters, analog-to-digital converters, or a phase-locked loop.

14. The digital hybrid mode power amplifier system of claim 13 wherein:

the power amplifier system is configured for base station applications, and

the digital field programmable gate array comprises at least one of a digital up-converter, a crest factor reduction, a predistorter, or a digital quadrature modulator.

15. The digital hybrid mode power amplifier system of claim 13 wherein the digital field programmable gate array provides predistortion that compensates adaptively for both nonlinearity and memory effects of the power amplifier portion by generating asymmetric distortion of a power amplifier.

16. The digital hybrid mode power amplifier system of claim 15 wherein the adaptive compensation for predistortion further comprises:

updating coefficients by detecting adjacent channel powers; and

using the adjacent channel power in performing an evaluative function.

17. The digital hybrid mode power amplifier system of claim 13 wherein the digital field programmable gate array comprises an adaptation algorithm to determine an optimum gate bias voltage of a power amplifier for stabilizing linearity fluctuations due to temperature changes of the power amplifier.

18. The digital hybrid mode power amplifier system of claim 12 wherein the power amplifier portion comprises at least one of an up-converter for real signal and an analog quadrature modulator for real and complex signals, a high power amplifier with multi-stage drive amplifiers, or a temperature sensor.

19. The digital hybrid mode power amplifier system of claim 18 wherein the power amplifier portion uses efficiency boosting techniques comprising at least one of Doherty, Envelope Elimination and Restoration, Envelope Tracking, Envelope Following, or Linear amplification using Nonlinear Components.

20. The digital hybrid mode power amplifier system of claim 12 wherein the down-converted feedback portion comprises at least one of a directional coupler, a mixer, a low pass filter, gain amplifiers, a band pass filter, or detectors.

21. The digital hybrid mode power amplifier system of claim 12 wherein in-band distortion resulting from a clipped signal at the output of the power amplifier portion caused by crest factor reduction is compensated by a DAC and UPC responsive to an output of the digital predistortion module.