Open-loop valley regulation for supply voltage modulation in power amplifier circuits

A method for valley compensation in a power amplifier system, the method comprising:

• monitoring a digital amplitude signal to detect a present gain setting of a plurality of gain settings, the digital amplitude signal being converted by a digital to analog converter to an analog amplitude signal, the analog amplitude signal used to amplitude modulate a signal output of a power amplifier circuit, the power amplifier circuit generating the signal output according to a supply voltage and to the present gain setting as indicated by the digital amplitude signal;
• identifying a present compensation value as associated with the present gain setting, the present compensation value being one of a plurality of compensation values, each stored by a lookup table in association with a respective gain setting of the plurality of gain settings, and each corresponding to a respective compensated supply voltage level that is calibrated so that setting the supply voltage to the respective compensated supply voltage level when the present gain setting is set to the respective gain setting causes an output valley level of the signal output generated by the power amplifier circuit to be substantially at a predetermined target valley level;
• generating a compensation signal based on the present compensation value;
• and
• outputting the compensation signal to a supply modulator circuit to generate the supply voltage at the respective compensated supply voltage level corresponding to the present compensation value.

A method for valley compensation in a power amplifier system, the method comprising:

• generating, for each gain setting of at least a portion of a plurality of gain settings, a respective compensation value of a plurality of compensation values by:
• setting a digital amplitude signal to indicate the gain setting, the digital amplitude signal converted by a digital to analog converter to an analog amplitude signal, the analog amplitude signal coupled with a power amplifier circuit configured to generate a signal output from a signal input such that the signal output has an amplitude based on the gain setting and a common mode based on a supply voltage;
• detecting a present output valley level of an amplitude envelope of the signal output at the gain setting;
• computing the respective compensation value for the gain setting based on the detecting the present output valley level, the respective compensation value corresponding to a respective compensated supply voltage level, calibrated such that setting the supply voltage to the respective compensated supply voltage level with the digital amplitude signal set to the gain setting causes an output valley level of the signal output generated by the power amplifier circuit to be substantially at a predetermined target valley level;
• and
• storing the respective compensation value in a lookup table in association with the gain setting.