GNSS信号模拟器通道群时延标定方法

传统的全球导航卫星系统(GNSS)信号模拟器通道群时延标定方法有相位翻转点法和相关峰法两种,两者均在零伪距或固定伪距的特殊仿真场景下进行测量,且在通道传输特性非理想的情况下测得的群时延均存在偏差.提出了基于闭环伪距测量的模拟器通道群时延标定方法,并设计实现了GNSS信号模拟器通道群时延标定系统.首先,采用高速直接射频采样存储系统对模拟器正常星座动态仿真场景下输出的导航信号和秒脉冲(1 PPS)信号同时进行记录.其次,使用软件接收机对信号进行捕获跟踪,利用三次样条插值判定1 PPS上升沿位置作为伪距观测历元时刻,对软件接收机的伪距观测量和模拟器仿真的伪距记录值做数据比对,得到模拟器的群时延标定值.最后,分别利用上述方法对两种商用模拟器的群时延进行了标定,实验结果表明,闭环伪距测量法有效可行,测量不确定度优于0.7 ns.

Group delay calibration method for GNSS signal simulator channel

Two kinds of traditional group delay calibration methods for global navigation satellite system (GNSS) signal simulator channels have been reported so far,which are phase transition point method and correlation peak method. Both of them measure the group delay in a special simulation scenario with zero or fixed pseudorange, and the measurements under non-ideal channel transmission characteristics are biased estimates of the group delay. A group delay calibration method for simulator channel based on closed-loop pseudorange measurement was proposed, and the corresponding group delay calibration system for GNSS signal simulator channels were designed. Firstly, the navigation signal and one pulse per second (1 PPS) signal outputted by the simulator in normal constellation dynamic scenariowere recorded simultaneously by a high-speed direct radio freqency (RF) sampling and storage system. Secondly, the navigation signal was captured and tracked by a software receiver, and the 1 PPS signal rising edge was determined by cubic spline interpolation and used as the pseudorange measurement epoch. Then the group delay can be obtained by data comparison between the software receiver-measured pseudorange and the simulator-recorded true pseudorange. Finally, the group delays of two different commercialsimulators were calibrated employing all the above methods. The experimental results show that the proposed method is effectively feasible and the measurement uncertainty reaches below 0.7 ns.