Design And Realization Of Novel Look-Up Table Digital Predistorter

The contradiction between limited spectrum resources and high speed data transfer rate has promoted the continuous development of communication system.The communication signal produced by the new way of digital modulation has high spectrum efficiency,but the signal power peak to average ratio is very large due to its multiple carrier aggregation.It can push the power amplifier into nonlinear area,which increases the bit error rate and affects the normal communication.Digital predistortion technology is implemented via baseband signal processing,which has the advantages of flexible,efficient,and easy programming.Digital predistortion technology has become the main power amplifier linearization techniques.This paper presents a novel type of polar look-up table predistorter model.Two one-dimensional look-up tables are adopted for the amplitude and phase predistortion respectively.Predistortion parameters of the novel model are directly acquired based on nonlinear modeling of power amplifier.Compared with the traditional model,the implementation is more simple and the requirement for hardware resources is lower.The novel predistorter model is designed and implemented based on the FPGA hardware platform.Measurement results show that the model is effective in the aspect of improving power amplifier linearity.It can improve the ACPR of power amplifier over 20 dB,which confirms the reliability of the novel predistortion model.Based on the novel polar look-up table predistortion model,we put forward non-uniform table indexing algorithm.The weighted error factor ?,which is dependent on the linear interpolation error and signal amplitude probability distribution,is used to realize the non-uniform table indexing.We complete algorithm simulation in matlab,and set up the VSG-VSA digital predistortion physical verification platform.Measurement results show that the proposed non-uniform look-up table indexing is effective in improving power amplifier linearity.Compared with the traditional uniform look-up table indexing,the non-uniform look-up table has 3-4 dB improvement in improving ACPR of power amplifier,which confirms the validity of the algorithm.