Adaptive digital predistorter with improving feedback signal distortion over-compensation

In this paper, a method for improving feedback signal distortion over-compensation of a digital pre-distortion(DPD) system is presented. The method comprises the following steps: acquiring a distortion compensation characteristic parameter of an input signal in a forward channel of the digital pre-distortion system to form a forward channel distortion compensation lookup table(LUT), and compensating the input signal before digit-analog converter (DAC); acquiring an ideal compensation characteristic parameter of the input signal in a small closed loop without power amplification to form a feedback signal distortion compensation LUT for compensating in a feedback signal; and acquiring an ideal compensation characteristic parameter of the input signal in a big closed loop with power amplification to form a digital pre-distortion LUT dealing with power amplification non-linear distortion for compensating in the forward signal. Through the method, the over-compensation characteristic of the feedback signal can be further effectively counter balanced based on compensation to forward channel distortion to achieve the aim of improving the performance of the digital pre-distortion system.