In one approach to calibration, a continuous wave (CW) tone with continuous ramping amplitude is transmitted by the transmission circuitry 102 and fed back from the output of the PA 106 to the input of the auxiliary receiver circuitry 104 via the feedback loop 112. The number of amplitude steps in the continuous ramp can be determined based on the characteristics of the PA 106. The graph of FIG. 2 illustrates an example of such an amplitude ramp. The distortion estimation component 110 receives the digital signals output by the auxiliary receiver circuitry 104 at each step and estimates the AM/AM and AM/PM values representing the distortion introduced by the PA at the corresponding amplitude. The estimated AM/AM and AM/PM values for the amplitude steps are then used to determine the correction entries of the calibration lookup table used by the DPD component 108.

Values for AM/AM and AM/PM are estimated for each step in the continuous ramp as follows. At each amplitude step, several samples of a complex CW tone are transmitted at that amplitude and received in the auxiliary receiver circuitry 104. An accumulated sample for the amplitude is generated based on the samples output by the auxiliary receiver circuitry 104. In general, the output samples are down converted to baseband and, after a specified number of samples has been output by the auxiliary receiver circuitry 104 and down converted, a filter is applied to the down converted samples to generate the accumulated sample. The magnitude and angle of the accumulated sample indicate AM/AM and AM/PM, respectively, for the step.