多径效应对直扩延迟锁定环的影响及消除技术

Interference of Multipath on Delay-Lock Loop and Elimination Technology in DS-SS Reciever

针对多径环境下直扩(DS-SS)信号的伪码跟踪问题,对延迟锁定环(DLL)进行了研究。在考虑多条路径干扰信号的情况下分析了多径效应对DLL鉴相特性的影响。为了消除DLL中的多径和噪声干扰,采用一种基于卡尔曼滤波的最大似然多径估计方法对DLL进行了改进。该方法通过对最大似然估计的输出进行卡尔曼滤波,得到了较为准确的多径幅度和延迟估计值,并对多径消除前后的DLL鉴相特性进行了仿真比较。结果表明,该多径估计方法能够有效消除多径和噪声对直扩信号伪码跟踪的影响。

For tracking the PN code of direct-sequence spread-spectrum（DS-SS） signals under multipath environment,the delay locked loop（DLL） is studied.In the case of existing multipath interference,the analysis on phase-detecting characteristic of DLL is given.In order to eliminate the multipath and noise interference on DLL,Kalman filter is used to filter the noise from the output of maximum likelihood estimation（MLE）,and then the more accurate multipath magnitude and delay are got.Finally,the phase-detecting characteristic of DLL is compared before and after eliminating multipath.The computer simulations show that the multipath estimation method can effectively eliminate the interference of multipath and noise on the PN code tracking.