Transmitter signal shaping

• US 9,246,523 B1
• Filed: 04/15/2015
• Issued: 01/26/2016
• Est. Priority Date: 08/27/2014
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: MagnaCom, Ltd. (Broadcom, Inc.)
• Inventors: Stopler, Daniel, Eliaz, Amir
• Primary Examiner(s): Tse, Young T
• Application Number:
  US14/687,861
• Time in Patent Office: 286 Days
• Field of Search: 375/260, 375/278, 375/284, 375/285, 375295-297, 330/149, 370/208, 370/210, 370/319, 370/344, 381/94.1, 381/94.4, 381/94.7, 381/119, 381/120, 455/67.13, 455/114.2, 455/114.3
• US Class Current: 1/1
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• 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
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04L 1/0042 Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26265 Arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral precoding
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A transmitter comprises at least one nonlinear circuit, and a power spectral density (PSD) shaping circuit. The PSD shaping circuit is operable to receive a symbol of a modulated signal, wherein the symbol corresponds to a first one or more frequency bins. The PSD shaping circuit is operable to perform iterative processing of the symbol, wherein each iteration of the processing comprises: generation of a pre-distortion signal based on a model of the at least one nonlinear circuit, wherein the nonlinearly distorted signal corresponds to a second one or more frequency bins; and combination of the symbol, or a pre-distorted version of the symbol, with the nonlinearly-distorted signal. The generation of the pre-distorted signal may comprise generation of a nonlinearly-distorted signal, and adjustment of one or more components of the nonlinearly-distorted signal.

Claims

1. A transmitter comprising:

at least one nonlinear circuit; and

a power spectral density shaping circuit configured to;

receive a symbol of a modulated signal, wherein said symbol corresponds to a first one or more frequency bins; and

perform iterative processing of said symbol, wherein each iteration of said processing comprises;

generation of a pre-distortion signal based on a model of said at least one nonlinear circuit, wherein said pre-distortion signal corresponds to a second one or more frequency bins; and

combination of said symbol, or a pre-distorted version of said symbol, with said pre-distortion signal.

2. The transmitter of claim 1, wherein said generation of said pre-distortion signal comprises:

generation of a nonlinearly-distorted signal; and

adjustment of one or more components of said nonlinearly-distorted signal.

3. The transmitter of claim 2, wherein said adjustment comprises weighting said one or more components of said nonlinearly-distorted signal.

4. The transmitter of claim 3, wherein:

said weighting is determined per frequency bin or per group of frequency bins; and

said weighting is determined based on distortion remaining in said pre-distorted signal after an iteration of said iterative processing of said symbol.

5. The transmitter of claim 2, wherein said one or more components are in one or more desired signal frequency bands.

6. The transmitter of claim 5, wherein said one or more desired signal frequency bands are frequency bands assigned to said transmitter by a basestation.

7. The transmitter of claim 2, wherein said one or more components are in one or more undesired signal frequency bands.

8. The transmitter of claim 7, wherein said one or more undesired signal frequency bands are out-of-band frequency bands.

9. The transmitter of claim 7, wherein said one or more undesired signal frequency bands are frequency bands allocated, by a basestation, to one or more other transmitters.

10. The transmitter of claim 2, wherein said adjustment of said one or more components is controlled based on a performance metric fed back to said transmitter from a receiver.

11. The transmitter of claim 2, wherein said adjustment of said one or more components is controlled based on order of a modulation constellation used for generation of said symbol.

12. The transmitter of claim 2, wherein said adjustment of said one or more components is controlled based on a determination of interference present at a receiver to which said symbol is to be transmitted.

13. The transmitter of claim 2, wherein said adjustment of said one or more components is controlled based on which frequency bands have been allocated to said transmitter by a basestation.

14. The transmitter of claim 2, wherein said adjustment of said one or more components results in shifting distortion from out-of-band frequencies to in-band frequencies.

15. The transmitter of claim 2, wherein said adjustment of said one or more components results in shifting distortion from in-band frequencies to out-of-band frequencies.

16. The transmitter of claim 2, wherein said adjustment of said one or more components is controlled based on whether a receiver to which said symbol is destined comprises circuitry for modeling and mitigating nonlinear distortion introduced by said transmitter.

17. The transmitter of claim 1, wherein said at least one nonlinear circuit comprises a power amplifier.

18. The transmitter of claim 1, wherein said at least one nonlinear circuit comprises a digital pre-distortion circuit.

19. The transmitter of claim 1, wherein said at least one nonlinear circuit comprises a digital nonlinear function circuit configured to compress a signal to be transmitted prior to input of said signal to be transmitted to a power amplifier of said transmitter.

20. The transmitter of claim 1, wherein said generation of said pre-distortion signal is based on a seeking of a minimum, maximum, or desired value of a performance metric.

21. The transmitter of claim 1, further comprising a pilot distortion circuit configured to distort pilots of said symbol.

22. A transmitter comprising:

a modulator circuit configured to generate a symbol to be transmitted;

a combiner circuit configured to combine said symbol with a first portion of a pre-distortion signal, a result of said combination being a pre-distorted signal;

a nonlinear distortion modeling circuit configured to;

model nonlinear distortion introduced by at least one nonlinear circuit of said transmitter; and

nonlinearly distort said pre-distorted signal, a result of said nonlinear distortion being a distorted signal; and

a modification circuit configured to modify said distorted signal to generate a second portion of said pre-distortion signal.

23. The transmitter of claim 22, wherein said modification circuit is configured to modify said distorted signal on a per subcarrier basis.

24. The transmitter of claim 23, wherein modification of said distorted signal by said modification circuit comprises weighting spectral components of said distorted signal.

25. The transmitter of claim 22, wherein said at least one nonlinear circuit comprises a digital pre-distortion circuit and a power amplifier circuit.

26. A transmitter comprising:

a modulator circuit configured to generate an orthogonal frequency division multiplexed (OFDM) or frequency division multiple access (FDMA) signal; and

a pre-distortion circuit configured to;

generate a periodic pre-distortion signal, wherein a period of the pre-distortion signal is synchronized to the period of said OFDM or FDMA signal; and

combine said periodic pre-distortion signal with said OFDM or FDMA signal, resulting in a pre-distorted signal.

27. The transmitter of claim 26, further comprising at least one nonlinear circuit and a nonlinear distortion modeling circuit, wherein:

said at least one nonlinear circuit comprises a power amplifier and a digital nonlinear function circuit; and

said nonlinear distortion modeling circuit is configured to model nonlinear distortion introduced by said at least one nonlinear circuit.