An Automatic Error Compensation Method for the Feedback Loop in Adaptive DPD Systems

摘要

Baseband digital predistortion (DPD) is an attractive method to improve the performance of high power amplifiers (PA). The feedback loop plays a very important role in the baseband DPD system. Its aim is to obtain the sampled signals on which the model of the PA is based and the DPD processing is done. The imperfections of the devices in the analog circuits, such as the modulator and demodulator, will influence the signal performance. Such non-ideal characters will influence the modeling of the PA and the processing of the DPD part and therefore limit the improvement of the predistortion system. In this article, error items oj the modulation and the demodulation in the feedback loop are analyzed and the compensation and correction algorithm is derived. Simulations are accomplished to validate the closed-form algorithm in a numerical way. The compensation and correction of the errors can be carried out automatically, and this method can be easily adopted in the adaptive DPD based on realtime data.