扩频测距系统中多径跟踪误差研究

Study of Multipath Tracking Errors in Spread Spectrum Ranging Systems

研究了任一“早”—“迟”码间距的相干和非相干延迟锁定环路中多径跟踪误差对伪距和载波相位观测量的影响。对于大的衰减带宽，相干延迟锁定环路的多径跟踪误差为零，而非相干延迟所定环路有１０ｍ左右误差，载波相位的测量无误差；对于小的衰减带宽，相干延迟锁定环路和非相干延迟锁定环路的多径跟踪误差相同。计算机模拟表明，对于相干和非相干延迟锁定环路，小的“早”—“迟”码间距能有效地降低多径跟踪误差。

In this paper,multipath tracking errors on pseudorange and carrier phase measurements are studied for both coherent and noncoherent delay lock loops with arbitrary early late spacings.The coherent delay lock loop is shown to have a major advantage,for a relatively high fading bandwidth, it has a zero tracking error,while a noncoherent delay lock loop has bias error of up to ten of meters.Carrier phase measurements are proved to be free of bias.For a small fading bandwidth,both coherent and noncohernent loops have the same maximum multipath errors.The simulation shows that a smaller early late spacing can reduce the multipath tracking errors effectively than commonly used one chip time for coherent and noncoherent delay lock loops.The results are especially interested for spread spectrum ranging systems such as GPS.