无码载波频率初值估计与导航星识别

Codeless carrier frequency initial value estimation and navigation satellite recognition

当导航卫星的民码信号不可用时,利用无码载波恢复技术测量各个导航卫星的多普勒频移能够实现多普勒定轨。针对伪码未知的情况,提出了基于相位补偿及数据块累加来增强信号,并结合快速傅里叶变换估计载波频率的方法;为解决无码条件下的导航卫星识别问题,提出了一种基于多普勒频移特征的导航星识别方法,研究了基于三分法快速搜索优化平移量的匹配算法,并采用全局匹配、局部剔除的策略来提高卫星识别的全局可信度。仿真结果表明,对于80ms的卫星中频数据,无码载波频率估计误差保持在7 Hz之内,并且正确估计的卫星数在9颗以上;在考虑先验参数不精准及测量误差的情况下,正确识别的卫星数大多为6颗及以上,满足定轨要求的最少卫星数目。

There is a way of Doppler orbit determination that recovers carrier signal effectively, and measures the Doppler frequency shift precisely when civil codes of satellite navigation signals are not available. For unknown pseudo-code, a method based on phase compensation and data block accumulation is presented to estimate the carrier frequency of the square signal accurately. For codeless navigation satellite identification, a method based on the characteristics of Doppler frequency shift is proposed, and the clock frequency offset of the receiver is re- ceived,and the match algorithm based on the three points method is researched. The global match, local elimi- nation strategy is adopt to improve the reliability of satellite recognition. The simulation reveals that codeless carrier frequency estimation error is within 7 Hz, and the number of satellites estimated correctly is 9 or more. Considering the inaccuracy prior parameters and measurement errors, at least 6 satellites are identified correct- ly, which satisfies the requirement of orbit determination of satellites.