OFDM系统中存在IQ不平衡时的时域频偏估计算法  

Time domain carrier frequency offset estimation in the presence of IQ imbalance for OFDM systems

作　　者：王非一[1] 辜方林[1] 王杉[1] 

机构地区：[1]国防科学技术大学电子科学与工程学院,湖南长沙410073

出　　处：《电子技术应用》2016年第11期102-105,共4页Application of Electronic Technique

基　　金：国家自然科学基金重大计划(培育项目)(91338105)

摘　　要：载波频偏是制约OFDM系统性能的重要因素。直接变频收发信机以其集成化、低功耗、低成本的优点得到广泛应用,但由于其射频前端模拟器件的不理想性会引入IQ不平衡,使估计算法性能下降。针对存在IQ不平衡时的载波频偏估计问题,一种新的基于训练序列的时域CFO估计算法被采用。该算法采用QAM调制的PN序列作为训练序列,根据PN序列良好的自相关性和QAM信号的正则特性,利用接收信号与本地训练序列做互相关得到频偏估计。仿真结果表明,与现有算法相比,所提算法对IQ不平衡稳健性好,且具有良好的估计精度。Carrier frequency offset （CFO） can cause significant performance degradation in orthogonal frequency division muhiplexing （OFDM） systems. The direct conversion transceiver are widely used in wireless systems in terms of circuit-board size, cost and power consumption, however it suffers from IQ imbalance due to the non-ideal radio frequency （RF） devices. IQ imbalance has a critical effect on the performance of conventional CFO estimation algorithms based on autocorrelation. In this paper, a new time domain CFO estimation algorithm independent of IQ imbalance is proposed by using a pseudo noise（PN） sequence modulated by QAM constellation as a preamble. Owing to the properness of QAM constellation, the CFO estimation can be obtained by cross-correlation between receive signals and the preamble. Simulation results show that in comparison with the existing methods, the proposed algorithm is robust against IQ inlbalance and performs well in estimation precision.

关 键 词：OFDM 直接变频收发机 IQ不平衡 载波频偏 

分 类 号：TN929.5[电子电信—通信与信息系统]