北斗系统伪距多径特征及对其定位精度影响分析

Analysis of Positioning Precision Affected by Pseudoranging Multipath for BDS

随着全球卫星导航系统现代化程度提高,电离层延迟、对流层延迟、轨道误差等各项误差得到了有效消除或减弱,但是不同用户端的多路径效应误差是不相关的,不能通过差分修正,使得多径误差成为影响用户定位精度的主要误差源。针对北斗系统多星座伪距多径分析需求,首先给出了基于相干超前-滞后延迟锁定环的码跟踪多径误差模型,生成了不同带宽、不同相关间距条件下的多径误差包络线;其次,利用信号源模拟北斗信号及其一路多径信号,定量分析了多径对北斗伪距观测值的影响,研究了不同厂家北斗接收机的抗多径性能;最后,利用北斗接收机实测数据,设计了短基线差分方法,分析了实测环境下伪距多径大小及其对单双频定位性能的影响。结果表明:北斗系统B1频点伪距多径大于B3频点,地球静止轨道卫星伪距多径大于倾斜地球同步轨道和中圆地球轨道卫星;静态条件下,B1频点多径误差均方根最大值为2.53m,B3频点多径误差均方根最大值为0.73m。

With the global navigation satellite system（GNSS） modernization, the satellite orbit error, the ionospheric delay and the tropospheric delay have been effectively eliminated or reduced, but the multipath error for different users is noncorrelation, which can not be removed through differential technique, and then it will be the major error source for GNSS navigation and positioning. Considering BeiDou navigation satellite system （BDS） constellation contains geostationary earth orbits （GEO） and inclined geo-synchronous orbits （IGSO） satellites, which are high-orbiting satellites, so the muhipath effect of BDS is different from that of global positioning system （GPS）. In order to analyze the multipath effect of high-orbiting satellites, three schemes are adopted in this paper. 1） Model of code tracking mutipath error is deduced based on coherent early-late delay-locked loop, mutipath error envelopes are achieved for different bandwidth and different correlation space. 2） The multipath effects on pseudo-range are quantitatively analyzed based on the satellite signals and multipath signals simulated by the signal source. The performance of anti-rnultipath is analyzed for the first time with different receivers. 3） The pseudorange multipath effect on the navigation and positioning is analyzed with the observations of BDS receiver through differential algorithm of short line. The calculation and analysis show that： pseudorange multipath of B1 is larger than B3, and pseudorange multipath of GEO is larger than IGSO and MEO. In static positioning, root mean square （RMS） of multipath of B1 can reach up to 2.53m, and RMS of multipath of B3 can reach up to 0.73 m.