System and method for adaptive nonlinear filtering

1. An adaptive nonlinear filtering system comprising:

a first interface configured to receive an input signal;

a second interface configured to receive a target signal;

an adaptive filter module coupled to the first interface, configured to:

divide a range of possible input values of the input signal into a plurality of subranges;

determine the subrange within which a value of the input signal falls;

determine an input dependent filter parameter based at least in part on the determined subrange;

generate an output signal based at least in part on the input dependent filter parameter; and

feed back a feedback signal that is generated based at least in part on the output signal and the target signal.

2. The system of claim 1 , wherein the adaptive filter module is further configured to:

determine a delayed subrange pertaining to a subrange within which a delayed input signal falls; and

wherein the input dependent filter parameter is determined further based at least in part on the delayed subrange.

3. The system of claim 1 , wherein the input dependent filter parameter includes a filter coefficient value.

4. The system of claim 1 , wherein the input dependent filter parameter includes a filter coefficient function.

5. The system of claim 1 , wherein the input dependent filter parameter includes a construction function.

6. The system of claim 1 , wherein the adaptive filter module includes a memory bank.

7. The system of claim 6 , wherein the input range is divided into S subranges, and the memory bank stores S sets of values.

8. The system of claim 1 , wherein the adaptive filter module includes a plurality of memory banks.

9. The system of claim 6 , wherein the adaptive filter module is further configured to adapt a value stored in the memory bank.

10. The system of claim 8 , wherein the adaptive filter module is further configured to:

determine a delayed subrange pertaining to a subrange within which a delayed input signal falls; and

wherein determining the input dependent filter parameter includes:

selecting a first value from a first one of the plurality of memory banks using the determined subrange;

selecting a second value from a second one of the plurality of memory banks using the delayed subrange; and

summing the first value and the second value.

11. The system of claim 10 , wherein the input dependent filter parameter includes a filter coefficient that is dependent at least in part on a sum of the first value and the second value.

12. The system of claim 1 , wherein the adaptive filter module includes N filter taps, the adaptive filter module includes N memory banks, and N is an integer that is greater than 1.

13. The system of claim 8 , wherein:

the input dependent filter parameter is a first input dependent filter parameter;

determining the first input dependent filter parameter includes selecting a first function from a first one of the plurality of memory banks using the relative location information;

the adaptive filter module is further configured to:

determine a delayed subrange pertaining to a subrange within which a delayed input signal falls; and

determine a second input dependent filter parameter, including by selecting a second function from a second one of the plurality of memory banks using the delayed subrange.

14. The system of claim 13 , wherein the output signal is generated based at least in part on a sum of the first and the second input dependent filter parameters.

15. The system of claim 1 , wherein the input range is divided into S subranges, and S depends on a granularity of a nonlinear function implemented by the adaptive filter module.

16. The system of claim 1 , wherein the adaptive filter module is a first adaptive filter module, and the system further comprises a second adaptive filter module that is coupled to the first adaptive filter module in a cascaded configuration.

17. The system of claim 1 , wherein the input signal is an in-phase (I) component of a received signal.

18. The system of claim 17 , wherein the adaptive filter module is a first adaptive filter module configured to process the I component, and the system further includes a second adaptive filter module configured in parallel with the first adaptive filter module to process a quadrature phase (Q) component of the received signal.

19. The system of claim 1 , wherein the adaptive filter module includes a thermometer code address generator that is configured to determine the subrange.

20. The system of claim 19 , wherein the adaptive filter module further includes an absolute value operator coupled to the thermometer code address generator.

21. The system of claim 19 , wherein the adaptive filter module further includes a sign operator.

22. The system of claim 1 , wherein the output signal includes odd harmonics that are approximately equal to the odd harmonics of the target signal.

23. The system of claim 1 , wherein the output signal includes even harmonics that are approximately equal to the even harmonics of the target signal.

24. The system of claim 1 , wherein:

the input signal is an input signal of a nonlinear system;

the target signal is an output signal of the nonlinear system; and

the adaptive nonlinear filtering system is configured to model the nonlinear system.

25. The system of claim 1 , wherein:

the input signal is an output signal of a nonlinear system;

the target signal is an input signal of the nonlinear system; and

the adaptive nonlinear filtering system is configured to perform post-distortion correction on the nonlinear system.

26. The system of claim 1 , wherein:

the output signal is an input of a nonlinear system;

the target signal is an output of the nonlinear system; and

the adaptive nonlinear filtering system is configured to perform pre-distortion correction on the nonlinear system.

27. A signal processing method, comprising:

receiving an input signal and a target signal;

generating relative location information corresponding to a relative location of a value of the input signal within a range of input values;

determining an input dependent filter parameter based at least in part on the relative location information;

generating an output signal based at least in part on the input dependent filter parameter; and

feeding back a feedback signal that is generated based at least in part on the output signal and the target signal,

wherein at least one of the above steps is performed by a processor.

28. An adaptive filter module comprising:

a memory bank storing a plurality of entries;

a thermometer code address generator coupled to the memory bank, the thermometer code address generator configured to generate relative location information corresponding to a relative location of a value of an input signal within a range of possible input values, the relative location information being used to select an entry from the memory bank, and the entry being used to generate an output signal; and

a feedback loop coupled to the memory bank, configured to update the memory bank using a feedback signal that is based at least in part on the output signal.