Digital Predistortion for nonlinear RF power amplifiers

• US 8,995,572 B1
• Filed: 03/17/2014
• Issued: 03/31/2015
• Est. Priority Date: 04/16/2010
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Wu, Songping
• Primary Examiner(s): Timory, Kabir A
• Application Number:
  US14/216,646
• Time in Patent Office: 379 Days
• Field of Search: 375/297, 375/296, 375/324, 375/254
• US Class Current: 375/297
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H04N 7/52 Systems for transmission of a pulse code modulated video signal with one or more other pulse code modulated signals, e.g. an audio signal or a synchronizing signal assembling of a multiplex stream by combining a video stream with other content or additional data, remultiplexing of multiplex streams, insertion of stuffing bits into the multiplex stream, assembling of a packetised elementary stream at server side H04N21/236; disassembling of a multiplex stream, remultiplexing of multiplex streams, extraction or processing of Service Information, disassembling of packetised elementary stream at client side H04N21/434

Abstract

Systems and techniques relating to wireless communications are described. A described technique includes aligning a received data sequence with a transmitted data sequence to produce an aligned data sequence, the received data sequence being based on an output of a power amplifier having one or more nonlinear characteristics that is responsive to the transmitted data sequence; dividing the aligned data sequence into N segments; obtaining first nonlinear parameters for the power amplifier based at least on first segments of the N segments; obtaining a second nonlinear parameter(s) corresponding to a second segment(s) of the N segments based on an extrapolation of the first nonlinear parameters, the second segment(s) having a lower transmitted data sequence value(s) than the first segments; and performing digital predistortion on a transmit data sequence based on the nonlinear predistortion parameters to compensate for the one or more nonlinear characteristics of the power amplifier.

Claims

1. A method, comprising:

aligning a received data sequence with a transmitted data sequence to produce an aligned data sequence, wherein the received data sequence is based on an output of a power amplifier having one or more nonlinear characteristics that is responsive to the transmitted data sequence;

dividing the aligned data sequence into N segments;

obtaining first nonlinear parameters for the power amplifier based at least on first segments of the N segments;

obtaining one or more second nonlinear parameters corresponding to one or more second segments of the N segments based at least on an extrapolation of the first nonlinear parameters, wherein the one or more second segments have lower transmitted data sequence values than the first segments; and

performing digital predistortion on a transmit data sequence based at least on predistortion parameters to compensate for the one or more nonlinear characteristics of the power amplifier, the predistortion parameters comprising the first nonlinear parameters and the one or more second nonlinear parameters.

2. The method of claim 1, wherein obtaining the first nonlinear parameters comprises determining first gain coefficients corresponding respectively to the first segments, and wherein obtaining the one or more second nonlinear parameters comprises determining one or more second gain coefficients based on an extrapolation of at least two of the first gain coefficients.

3. The method of claim 1, wherein obtaining the first nonlinear parameters comprises determining first phase coefficients corresponding respectively to the first segments, and wherein obtaining the one or more second nonlinear parameters comprises determining one or more second phase coefficients based on an extrapolation of at least two of the first phase coefficients.

4. The method of claim 1, wherein performing digital predistortion comprises:

accessing a sample value of the transmit data sequence;

retrieving a predistortion parameter from a data structure based on the accessed sample value, the data structure storing the predistortion parameters indexed based on input amplitude ranges or values; and

applying the retrieved predistortion parameter to the accessed sample value.

5. The method of claim 1, wherein the first segments and the one or more second segments are separated by a threshold parameter that is selected to avoid noisy estimation.

6. The method of claim 1, wherein the aligning comprises arranging sample pairs in sample pair groups, each sample pair comprising a transmit sample of the transmitted data sequence and a receive sample of the received data sequence, wherein the receive samples of the sample pairs are aligned with the corresponding transmit samples of the sample pairs.

7. The method of claim 6, comprising:

determining representative sample pairs for at least a portion of the sample pair groups that correspond to the first segments, wherein obtaining first nonlinear parameters comprises determining gain coefficients, corresponding respectively to the first segments, that are based on the representative sample pairs.

8. An apparatus, comprising:

circuitry configured to align a received data sequence with a transmitted data sequence to produce an aligned data sequence, and to divide the aligned data sequence into N segments, wherein the received data sequence is based on an output of a power amplifier having one or more nonlinear characteristics that is responsive to the transmitted data sequence; and

an estimator configured to obtain first nonlinear parameters for the power amplifier based at least on first segments of the N segments, and to obtain one or more second nonlinear parameters corresponding to one or more second segments of the N segments based at least on an extrapolation of the first nonlinear parameters, wherein the one or more second segments have lower transmitted data sequence values than the first segments.

9. The apparatus of claim 8, wherein the first nonlinear parameters comprise first gain coefficients corresponding respectively to the first segments, and wherein the one or more second nonlinear parameters comprise one or more second gain coefficients based on an extrapolation of at least two of the first gain coefficients.

10. The apparatus of claim 8, wherein the first nonlinear parameters comprise first phase coefficients corresponding respectively to the first segments, and wherein the one or more second nonlinear parameters comprise one or more second phase coefficients based on an extrapolation of at least two of the first phase coefficients.

11. The apparatus of claim 8, comprising:

a compensator configured to perform digital predistortion on a transmit data sequence based at least on predistortion parameters to compensate for the one or more nonlinear characteristics of the power amplifier, the predistortion parameters comprising the first nonlinear parameters and the one or more second nonlinear parameters.

12. The apparatus of claim 11, wherein the compensator is configured to:

access a sample value of the transmit data sequence,

retrieve a predistortion parameter from a data structure based on the accessed sample value, the data structure storing the predistortion parameters indexed based on input amplitude ranges or values, and

apply the retrieved predistortion parameter to the accessed sample value.

13. The apparatus of claim 8, wherein the first segments and the one or more second segments are separated by a threshold parameter that is selected to avoid noisy estimation.

14. The apparatus of claim 8, wherein the circuitry comprises a data sync module that is configured to arrange sample pairs in sample pair groups, each sample pair comprising a transmit sample of the transmitted data sequence and a receive sample of the received data sequence, and wherein the receive samples of the sample pairs are aligned with the corresponding transmit samples of the sample pairs.

15. The apparatus of claim 14, wherein the circuitry is configured to determine representative sample pairs for at least a portion of the sample pair groups that correspond to the first segments, and wherein the first nonlinear parameters comprises gain coefficients, corresponding respectively to the first segments, that are based on the representative sample pairs.

16. A system, comprising:

processor electronics configured to produce a digital transmit data sequence;

a first converter to convert the digital transmit data sequence to an analog transmit signal;

a power amplifier configured to produce an amplified signal based on the analog transmit signal, wherein the power amplifier has one or more nonlinear characteristics;

a second converter to convert the amplified signal to a digital receive data sequence;

circuitry configured to align the digital receive data sequence with the digital transmit data sequence to produce an aligned data sequence, and to divide the aligned data sequence into multiple segments; and

an estimator configured to obtain first nonlinear parameters for the power amplifier based at least on first segments of the multiple segments, and to obtain one or more second nonlinear parameters corresponding to one or more second segments of the multiple segments based at least on an extrapolation of the first nonlinear parameters, wherein the one or more second segments have lower digital transmit data sequence values than the first segments,

wherein the processor electronics are configured to perform digital predistortion based at least on predistortion parameters to compensate for the one or more nonlinear characteristics of the power amplifier, the predistortion parameters comprising the first nonlinear parameters and the one or more second nonlinear parameters.

17. The system of claim 16, wherein the first nonlinear parameters comprise first gain coefficients corresponding respectively to the first segments, and wherein the one or more second nonlinear parameters comprise one or more second gain coefficients based on an extrapolation of at least two of the first gain coefficients.

18. The system of claim 16, wherein the first nonlinear parameters comprise first phase coefficients corresponding respectively to the first segments, and wherein the one or more second nonlinear parameters comprise one or more second phase coefficients based on an extrapolation of at least two of the first phase coefficients.

19. The system of claim 16, wherein the processor electronics are configured to:

access a sample value of an input data sequence,

retrieve a predistortion parameter from a data structure based on the accessed sample value, the data structure storing the predistortion parameters indexed based on input amplitude ranges or values, and

apply the retrieved predistortion parameter to the accessed sample value.

20. The system of claim 16, wherein the first segments and the one or more second segments are separated by a threshold parameter that is selected to avoid noisy estimation.

21. The system of claim 16, wherein the circuitry comprises a data sync module that is configured to arrange sample pairs in sample pair groups, each sample pair comprising a transmit sample of the digital transmit data sequence and a receive sample of the digital receive data sequence, and wherein the receive samples of the sample pairs are aligned with the corresponding transmit samples of the sample pairs.

22. The system of claim 21, wherein the circuitry is configured to determine representative sample pairs for at least a portion of the sample pair groups that correspond to the first segments, and wherein the first nonlinear parameters comprises gain coefficients, corresponding respectively to the first segments, that are based on the representative sample pairs.

23. The system of claim 16, wherein the processor electronics comprise the estimator.

24. The system of claim 16, wherein the processor electronics comprise the circuitry.