Selecting samples for amplifier digital predistortion estimation
View Patent ↗The present invention provides a method for selecting samples for digital amplifier predistortion estimation. The method may include accessing a plurality of samples. Each sample includes information associated with an input signal and a corresponding output signal of the amplifier. The method may also include selecting a subset of the plurality of samples based on a sample distribution and determining a transfer function associated with the amplifier based on the subset of the plurality of samples. The method further includes determining a predistortion function based on the transfer function and applying the predistortion function to the input signal of the amplifier.
1. A method, comprising:
accessing a plurality of samples, each sample comprising information associated with an input signal and a corresponding output signal of an amplifier at a selected time interval;
selecting a subset of the plurality of samples based on a sample distribution that is determined prior to accessing the samples, the sample distribution being normalized to a number of samples that is determined prior to accessing the samples;
determining a transfer function associated with the amplifier based on the subset of the plurality of samples using only samples collected during the selected time interval;
determining a predistortion function based on the transfer function; and
applying the predistortion function to the input signal of the amplifier.
2. The method of claim 1 , wherein accessing the plurality of samples comprises accessing information indicative of a plurality of powers associated with the input signal and the output signal.
3. The method of claim 1 , wherein selecting the subset of the plurality of samples comprises associating each of the plurality of samples with one of a plurality of bins.
4. The method of claim 3 , wherein selecting the subset of the plurality of samples comprises determining a threshold for each of the plurality of bins based on the sample distribution.
5. The method of claim 4 , wherein selecting the subset of the plurality of samples comprises selecting a sample if the number of samples in the associated bin is less than the threshold for the associated bin.
6. The method of claim 1 , wherein determining the transfer function comprises determining the transfer function at a predetermined time interval.
7. The method of claim 1 , wherein determining the transfer function comprises determining a response matrix.
8. The method of claim 7 , wherein determining the response matrix comprises determining a correlation matrix.
9. The method of claim 7 , wherein determining the transfer function comprises inverting the response matrix.
10. The method of claim 1 , comprising storing the predistortion function in a lookup table.
11. The method of claim 10 , wherein applying the predistortion function comprises accessing a predistortion function from the lookup table.
12. A method involving a radiofrequency amplifier in a wireless communication device, comprising:
accessing a plurality of samples, each sample comprising information associated with an input radiofrequency signal and a corresponding output radiofrequency signal of the amplifier at a selected time interval;
selecting a subset of the plurality of samples based on a sample distribution that is determined prior to accessing the samples, the sample distribution being normalized to a number of samples that is determined prior to accessing the samples;
determining a transfer function associated with the amplifier based on the subset of the plurality of samples using only samples collected during the selected time interval;
determining a predistortion function based on the transfer function; and
applying the predistortion function to the input radiofrequency signal of the amplifier.
13. The method of claim 12 , wherein accessing the plurality of samples comprises accessing information indicative of a plurality of powers associated with the input radiofrequency signal and the output radiofrequency signal.
14. The method of claim 13 , wherein accessing information indicative of a plurality of powers associated with the input radiofrequency signal comprises accessing information indicative of a plurality of powers associated with at least one wireless communication device.
15. The method of claim 13 , wherein selecting the subset of the plurality of samples comprises associating each of the plurality of samples with one of a plurality of bins.
16. The method of claim 15 , wherein selecting the subset of the plurality of samples comprises determining a threshold for each of the plurality of bins based on the sample distribution.
17. The method of claim 16 , wherein selecting the subset of the plurality of samples comprises selecting a sample if the number of samples in the associated bin is less than the threshold for the associated bin.
18. The method of claim 11 , wherein determining the transfer function comprises determining a response matrix.
19. The method of claim 18 , wherein determining the response matrix comprises determining a correlation matrix.
20. The method of claim 18 , wherein determining the transfer function comprises inverting the response matrix.
21. The method of claim 12 , comprising storing the predistortion function in a lookup table.
22. The method of claim 21 , wherein applying the predistortion function comprises accessing a predistortion function stored in the lookup table.