数字电视大范围载波频偏快速捕获算法

Rapid large frequency offset estimation for DTMB system

根据中国数字电视地面传输标准帧结构特点,提出了一种大范围频率偏差捕获方法.该算法利用PN(Pseudo Noise)序列移位相加后仍为PN序列这一特征,通过帧头PN序列与本地PN序列的差分互相关得到待求的频偏值,然后利用BLUE(Best Linear Unbi-ased Estimator)方法,在不损失频偏精度的前提下扩大频偏估计范围.该算法能在帧同步前快速捕获大范围频偏,为可靠实现帧同步以及频偏跟踪过程提供了必要条件.仿真结果表明,相对于传统的差分互相关算法,该算法能在一个帧头时间内快速锁定频偏,频偏估计范围扩大了H倍且频偏精度不变.

A frequency synchronization algorithm for digital terreslrial television multimedia broadcasting（DTMB） system with a large frequency offset was developed.The estimated frequency offset was obtained by differential correlation between received pseudo noise（PN） sequence and local PN sequence based on the m sequence cyclic shift-and-add property.Best linear unbiased estimator was used to enlarge the estimation range and maintain the estimation accuracy.This scheme could finish carrier frequency acquisition even with large frequency offset in a short time,and provide the necessary conditions for frequency offset tracking.Simulation results under AWGN and multipath channels show that the proposed scheme enlarges the frequency estimation range by H times with the same accuracy compared with the traditional differential correlation algorithm used for frequency synchronization in DTMB system.