北斗导航卫星伪距偏差特性及减弱方法

导航卫星信号的非理想特性会引起伪距测量产生偏差,具体表现为相同类型接收机具有相同伪距偏差,不同类型接收机的伪距偏差不一致.当提供导航定位服务产品的接收机技术状态与用户端不一致时,伪距偏差将引起导航定位服务性能降低.本文利用超短基线双差伪距O?C(Observation Minus Computation)方法计算了BDS(Beidou Satellite Navigation System)的伪距偏差,发现在早期试验卫星阶段的不同状态接收机之间存在较大的伪距偏差现象,设计了接收机环路参数调整、改变抗多径算法和卫星预失真滤波器参数调整三种减弱伪距偏差的方法.分别试验验证结果表明,接收机环路参数调整能大幅降低卫星之间的伪距偏差,B1I各颗卫星伪距偏差标准差由0.63 m降低至0.36 m;抗多径算法会造成额外的伪距偏差,窄相关算法能大幅减小伪距偏差,B1I各颗卫星伪距偏差标准差由0.36 m降低至0.18 m;调整卫星预失真滤波器参数能在一定程度上减小伪距偏差,单颗卫星伪距偏差降低约0.3–0.4 m.最后,针对BDS卫星伪距偏差解算无固定参考基准的问题,设计了一种基于外频标非实时双差O?C方法,利用该方法分别处理了BDS和GPS(Global Positioning System)数据,并对两个系统卫星伪距偏差的特性进行比较分析.结果表明,BDS和GPS卫星都存在伪距偏差;GPS卫星L2C伪距偏差与BDS-3卫星B1C数据支路相当;GPS卫星L1CA伪距偏差与其兼容互操作的BDS-3卫星B1C导频支路相当;L5C与其兼容互操作的BDS-3卫星B2a信号相比伪距偏差更大.

Pseudorange-bias characteristics and the weakening method of BDS satellites

The nonideal characteristics of a navigation satellite signal will cause a pseudorange bias,which is manifested by the same type of receiver with the same pseudorange biases and different types of receivers with different pseudorange biases.When the technical state of receivers providing the navigation product is inconsistent with that of the users,the pseudorange bias will cause degradation of navigation and positioning service performance.In this paper,the pseudorange bias of BDS(Beidou Satellite Navigation System)is calculated using the ultrashort baseline pseudorange double-difference O?C(Observation Minus Computation)method.A large bias of B1I is obtained between two different juxtapositional receivers in the early stage of the experimental satellites.Thereafter,three methods,including the adjustment of the parameters of the loop of the receiver,a change in the multipath reduction algorithm,and an adjustment of the filter parameter of the predistortion of the satellite,are designed to reduce the bias.Experimental results indicate that the adjustment of parameters of the loop of the receiver can significantly reduce the pseudorange bias between the satellites,and the standard deviation of the pseudorange bias of B1I can be reduced from 0.63 to 0.36 m.Compared with the antimultipath observation,the observation of a narrow correlation can significantly reduce the pseudorange bias,and the standard deviation of the pseudorange bias of BII can be reduced from 0.36 to 0.18 m.Further,an adjustment of the filter parameters of the predistortion of the satellite can reduce the pseudorange bias of a single satellite by 0.3–0.4 m.There is no fixed reference satellite to evaluate the pseudorange biases of BDS satellites.A non-real-time doubledifference O?C method that is based on the same external time and frequency controls of different receivers is designed to calculate the pseudorange bias.Employing this method,the characteristics of the pseudorange biases of BDS and GPS(Global Positioning System)satellites are compared.It is confirmed that(1)pseudorange biases exist in both BDS and GPS satellites,(2)the pseudorange bias of the L2C signal of GPS satellites is equivalent to that of the B1C data branch of BDS satellites,(3)the pseudorange bias of L1CA of GPS satellites is equivalent to the interoperable B1C pilot branch of BDS satellites,and(4)the pseudorange bias of L5C of GPS satellites is larger than that of the interoperable B2a signal of BDS satellites.