Power amplifier signal compensation

1. A method, comprising:

applying digital pre-distortion (DPD) of a power amplifier at a frequency channel, a fixed input power alignment value, and a fixed temperature; and

determining an optimal input power alignment value for the power amplifier in response to a change in at least one of frequency and temperature, the determining including measuring adjacent channel leakage ratios (ACLRs) for a plurality of input power alignment values and a plurality of frequency channels with the DPD at a plurality of temperatures, and selecting the optimal input power alignment value for the power amplifier for each frequency channel of the plurality of frequency channel based on the measured ACLRs;

applying the DPD and the optimal input power alignment value across frequency channels and temperature;

measuring and recording output power variations of the power amplifier versus frequency and temperature; and

determining optimal input power value curve for each temperature of the plurality of temperatures across each frequency channel of the plurality of frequency channels by selecting an optimal static input power alignment value for the power amplifier for each frequency channel of the plurality of frequency channel and for each temperature of the plurality of temperature based on the measured ACLRs.

2. The method of claim 1 , wherein the applied DPD may be characterized a priori or calibrated.

3. The method of claim 1 , wherein selecting an optimal static input power alignment value comprises selecting, for each frequency channel, a static input power alignment value that corresponds to an optimal ACLR.

4. The method of claim 1 , further comprising varying the input power alignment values when applying the DPD onto any frequency channel and temperature.

5. The method of claim 1 , further comprising adjusting a gain to compensate the output power variation.

6. The method of claim 1 , wherein determining comprises:

dithering a power level of a transmit signal;

measuring a difference in input power levels of the power amplifier and a difference in output power levels of the power amplifier in response to dithering the power level of the transmit signal; and

adjusting the input power alignment value to achieve a desired ratio of the difference in the output power levels with respect to the difference in the input power levels.

7. The method of claim 6 , wherein dithering comprises dithering a power level of the transmit signal by a fraction of the power level.

8. The method of claim 6 , wherein adjusting comprises adjusting the input power alignment value to achieve a target slope equal to the difference in output power values divided by the difference in input power values.

9. The method of claim 1 , wherein determining comprises:

capturing in-phase and quadrature (IQ) samples of a transmit signal;

constructing an amplitude-to-amplitude (AM-AM) table from the IQ samples; and

calculating a compression of the power amplifier based on the AM-AM table.

10. The method of claim 9 , further comprising adjusting the input power alignment value based on characteristics of an AM-AM curve.

11. A device, comprising:

means for applying digital pre-distortion (DPD) of a power amplifier at a frequency channel, a fixed input power alignment value, and a fixed temperature; and

means for determining an optimal input power alignment value for the power amplifier in response to a change in at least one of frequency and temperature, wherein the means for determining comprises means for measuring adjacent channel leakage ratios (ACLRs) for a plurality of input power alignment values and a plurality of frequency channels and temperatures with a calibrated DPD at a plurality of temperatures, means for selecting the optimal static input power alignment value for the power amplifier for each frequency channel of the plurality of frequency channel based on the measured ACLRs;

means for applying the DPD and optimal static input power alignment onto a frequency and temperature during operation;

means for measuring and recording output power variations of the power amplifier versus frequency and temperature; and

means for determining optimal input power value curve for each temperature of the plurality of temperatures across each frequency channel of the plurality of frequency channels by selecting an optimal static input power alignment value for the power amplifier for each frequency channel of the plurality of frequency channel and for each temperature of the plurality of temperature based on the measured ACLRs.

12. The device of claim 11 , wherein the means for determining comprises:

means for dithering a power level of a transmit signal;

means for measuring a difference in input power levels of the power amplifier and a difference in output power levels of the power amplifier in response to dithering the power level of the transmit signal; and

means for adjusting the input power alignment value to achieve a desired ratio of the difference in the output power levels with respect to the difference in the input power levels.

13. The device of claim 11 , wherein the means for determining comprises:

means for capturing in-phase and quadrature (IQ) samples of a transmit signal;

means for constructing an amplitude-to-amplitude (AM-AM) table from the IQ samples;

means for calculating at least one parameter based on the AM-AM table; and

means for adjusting the input power alignment value based on the at least one parameter.