长码快速直接捕获中的多普勒频率偏移估计

Estimation of Satellite Signal＇ s Doppler Shift for Fast and Direct Acquisition of Long Cycle and High Rate Pseudo- Random Code

长码直捕中，卫星信号多普勒频率偏移估计是提供先验频率信息，减少频域搜索范围的一个重要方面。本文提出了一种基于接收机和卫星概略PVT（位置、速度和时间）信息的多普勒频率偏移估计算法。算例结果表明，通常的启动状态下，该算法可以将多普勒频率偏移不确定范围压缩4～10倍，使长码直捕的时间或功耗相应成倍降低，有效地辅助长码直捕的实现。

In the direct acquisition of long cycle and high rate PRN code, satellite signal ＇s Doppler shift estimation is an important aspect of offering prior frequency information to reduce the searching ranges in frequency field. Basing on approximate PVT information of receiver and satellite, a new algorithm of compressing Doppler shift＇s uncertainty ranges is put forward. Numerical results indicate that the uncertainty ranges of Doppler shift can be compressed 4 to 10 times generally. And the effective compression of frequency uncertainty ranges will cut the time or power cost down correspondingly in direct acquisition of long cycle and high rate PRN code, thereby assist the direct acquisition effectively.