低载噪比下P码接收精频测量新算法及性能分析

A New Algorithm and Performance Analysis for Frequency Refinement of P Code under Low C/N0

GPS信号的P码码速率是C/A码的10倍,所以捕获时搜索相同时长的码相位需要做10倍点数的相关运算,相关运算通常用频域FFT实现,而硬件平台对FFT点数的限制使捕获得到的多普勒频率估计误差很大,因此C/A码的各种精频测量方法不能适用于低载噪比下的P码接收。本文针对P码的特性,在利用DFT相位差估计信号频率的基础上,提出了一种低载噪比下P码接收精频测量的新算法——差分相干法,并从理论和蒙特卡罗仿真两方面分析、比较了该算法与传统算法的性能,证明了本文算法能够兼顾接收机系统的实时性和精频测量精度的要求。

The rate of P code is 10 times of that of C/A, so the length of the correlation operation become 10 times correspondingly. The correlation operation is usually implemented by FVr in frequeney domain, but the estimation error of acquisition frequeney is signifieant beeause of the restrain from hardware. Therefore, kinds of methods for frequency refinement for C/A code can＇ t work well for P code, espeeially under low C/N0. Aecording to the characters of P code, and basing on the method of estimating signal frequency from DFT phase difference, a new algorithm for frequency refinement for P eode under low C/N0 is presented in this paper differen- tially eoherent method. Compared with the traditional algorithms, the algorithm＇ s performanee is analyzed beth from theory and monte- carlo simulation. The result proves that the new algorithm not only meets the real-time requirement of reeeiver system, but also satisfies the precision of frequency refinement.