基于多级结构的高阶QAM信号大频偏估计方法

Based on Multi-stage Structure High-order QAM Modulation Large Frequency Offset Estimation

基于极性判别的频率估计方法在对大频偏的高阶QAM信号进行载波同步时,最大频偏估计范围约3%符号速率,不能满足大频偏高质量信号分析的测试要求。针对该问题,本文提出一种改进的多级结构的高阶QAM调制大频偏估计方法,利用基于DFT频率估计的改进开环结构实现载波频率的粗同步,并结合优化极性判别方式的闭环同步环路实现精细同步。仿真结果显示,所提方法在保证精度的同时,扩大了载波频偏的捕获范围,在信噪比大于20dB时,频偏捕获范围最大可达50%符号速率,满足大频偏高阶QAM调制信号的分析测试需求。

Based on polar-decision of frequency estimation can’t satisfy high quality signal analysistest when it used in large frequency offset estimation of High-order QAM signal,especially in case ofmaximum frequency offset achieved for3percent symbol rate.This article addressed these issues andproposed one improved multi-stage structure of high-order QAM large frequency offset estimation.Thisestimation was based on DFT frequency estimation to improve open-loop to realize carrier frequencycoarse synchronization.It used optimized polar-decision of closed-loop to realize high precisionsynchronization.Simulation results show that the proposed method expands the captured range of carrieroffset ensure accuracy while ensuring accuracy.Frequency offset can achieve maximal50percent ofsymbol rate when SNR is bigger than20dB to satisfy large frequency offset High-order QAM signalanalysis test.