Feedback Quantization in Crosscorrelation Predistorters

Amplification of signals with fluctuating envelopes inevitably leads to distortion because of non-linear behavior of the Power Amplifier (PA). Digital Predistortion can counteract these non-linear effects. In this paper, the crosscorrelation predistorter is described and the effects of quantization in the feedback path are presented. One of the effects is that the quantization noise becomes correlated with the signal to be quantized, resulting in reduced performance of predistortion. A technique to reduce these effects is to inject a dither signal before quantization. Because of the quantization noise and dither signal, more data has to be used to obtain estimates of the PA behavior that are accurate enough for effective predistortion.