多径干扰下GPS弱信号跟踪算法研究

在带有多径干扰的、并且低载噪比的GPS信号下,分析了多径带来的码环误差以及因此引起的伪距误差的原理.在此基础上,考虑在码环跟踪的Strobe鉴相算法中,引入一个修正因子σ,使得码环跟踪时,对一定范围内的短多径起到抑制的作用.由于改进后的跟踪算法没有用到Q路输出,并且原信号为弱信号,因此需要跟踪环路提供好的载波跟踪性能.为此,考虑使用扩展卡尔曼滤波(EKF)算法来替代原有的载波跟踪环路,提高跟踪环路的噪声抑制性能.在此基础上,将EKF载波环跟踪与修正后的码环跟踪结合起来使用,共同进行多径干扰下GPS弱信号的跟踪.

Research on the tracking algorithm of GPS weak signal under multipath interference

This research discusses the theory of code- tracking error and pseudo- range error brought about by multipath interference on the low C /N ratio GPS signal. With this,an adjusting factor was introduced into the Strobe phase algorithms during code loop tracking to reduce the interference of short multipath within some range.Because of the absence of Q output in the improved algorithm and the weakness of the original signal,the carrier tracking loop has to provide better carrier tracking performance. As a result,the Extended Kalman Filter( EKF) algorithm is used instead of the original carrier tracking loop in order to improve the noise suppression performance.Based on this,the EKF carrier loop tracking and code loop tracking after adjustment were combined to process the weak GPS signal tracking under multipath interference.