CAPS信号的电离层色散效应研究

Ionospheric is a dispersive medium for electromagnetic wave. The CAPS signals which propagate through the ionosphere are influenced by the dispersion effect. The different frequency components of the CAPS signal suffers different delay, resulting in a distortion of the ranging signal, and causing the ranging error. Considering CAPS using 40 MHz bandwidth signal, such dispersion distortion effects will be more pronounced. The current research mainly consider the ionospheric delay error which causes the group velocity of the satellite navigation signals, but rarely consider the influence of dispersion distortion ranging error. This project examines the ranging error caused by ionospheric distortion of the CAPS 40 MHz spread spectrum signal. And the theoretical analysis, computer modeling and Monte Carlo simulation method is used to calculate the ranging error caused by the ionospheric dispersion distortion of the CAPS 40MHz spread spectrum signal. And the method to reduce this error will be studied.

电离层对电磁波是色散介质。CAPS信号在电离层中传播时受色散效应作用，不同频率成分所受延时不同，导致测距信号的失真，从而引起测距误差增加。特别是CAPS采用40 MHz的宽带测距信号时，这种色散失真影响会更明显。目前研究主要考虑电离层对卫星导航信号的群速度时延误差，未考虑色散失真带来的测距误差。本项目研究CAPS的40 MHz宽带测距信号受电离层色散失真引起的测距误差，从理论分析、计算机建模、Monte Carlo仿真和生成实际信号进行试验分析来开展研究，分析和计算电离层色散失真引起的CAPS信号的测距误差量级，并探索减小此误差的方法。

卫星导航信号在空间传播中通过电离层到达用户接收机，电离层对电磁波信号是色散介质。CAPS信号为C波段宽带信号，在电离层中传播时受色散效应作用，其不同频率成分的传播延时不同，导致地面用户接收到的测距信号失真，从而增加了测距误差。特别是在CAPS增加信号带宽，采用40 MHz的宽带测距信号时，这种色散失真影响会更显著。目前电离层误差研究主要考察电离层对卫星导航信号的群速度时延误差，未考虑色散失真导致的测距误差。本项目研究CAPS的40 MHz宽带测距信号受电离层色散失真引起的测距误差。通过理论分析和仿真计算，考察CAPS在中心频率为3820 Mhz，带宽为40 MHz时的测距信号，根据电离层TEC常见变化范围，得到电离层色散失真导致的测距误差量级为毫米级到厘米级，在某些电离层TEC极端异常情况下可以达到分米级。在高精度定位需求中，需考虑此误差，通过电离层对信号失真的特性研究和卫星导航信号体制改进，可减小此信号失真对定位的影响。在实验室中，通过研制CAPS的40MHz宽带信号发射基带生成试验信号，通过数据采集设备采集信号进行分析并研究改善定位精度的方法。