卫星地基增强系统下的级联双频载波相位平滑优化算法

Cascade Dual Frequency Carrier Phase Smoothing Optimization Algorithm Under GBAS

在卫星地基增强系统(GBAS)中,电离层时间和空间梯度是影响相位平滑过程的重要因子。为降低电离层对伪距平滑输出的影响并提高伪距平滑差分修正量的可用性,基于单频相位平滑引入的电离层额外误差的分析,本文提出了级联双频载波相位平滑算法。其基本原理为:利用一级低通滤波器对导航信号中的电离层延迟进行有效估计,将一级滤波器的输出与双频信号伪距值及载波相位值线性组合,生成码减载波值(CMC)作为二级低通滤波器的输入,同时对输出的平滑伪距值进行钟差校正,该滤波算法能够消除电离层延迟误差及衰减接收信号噪声。利用地基增强系统实时采集数据,并从平滑残差、定位精度等方面进行了对比仿真分析。结果表明,该改进算法能够有效地降低电离层对伪距差分修正量的影响,减小平滑伪距的残余误差,提高平滑伪距差分修正量的可用性及在精密进近着落过程中的定位精度。

Both temporal and spatial gradients of ionosphere are major factors that influence the phase smoothing of the carrier for GBAS.In order to reduce the effect of ionosphere on the pseudo-range smoothing output and improve the availability of the differential correction on smoothed pseudo-range,a cascaded dual-frequency smoothing filtering algorithm based on the analysis of additional ionosphere error induced by single frequency phase smoothing is proposed.The filter algorithm estimates effectively the ionosphere delay in the navigation signal through the first-order low-pass filter,and takes code minus carrier（ CMC） generated through linearly combining the first-order filter output with dual-band signal pseudo-range value and the carrier phase value as a second-order low-pass filter input,with correcting the output of the smooth pseudo-range value of the clock correction,eliminates the ionosphere delay error and attenuate the received signal noise.The results show that the improved algorithm can effectively reduce the influence of the ionosphere on the pseudo-range differential correction and the residual error of the smoothed pseudo range,improve the availability of the smoothed pseudo-range differential correction,and the positioning accuracy during the precision approach landing.