大频偏条件下PN码捕获改进算法

针对大频偏条件下PN码捕获的问题，提出了一种改进的PN码捕获算法，即基于谱线插值的 联合码捕获算法。首先对现有的码捕获技术进行了分析，然后在部分相关值作FFT的码捕获 算法的基础上，提出了基于谱线插值的联合码捕获算法。算法的核心思想是对部分相关值作 FF T处理，并利用插值公式计算出载波频偏的精确估计值，使得后续的载波跟踪环更有利于载 波跟踪。介绍了新的码捕获系统的工作原理，推导了载波频偏估计的插值公式，并将非相干 累加技术应用于码捕获系统，从而提高了低信噪比条件下载波频偏估计的精度。最后，通过 仿真证明了此算法对现有GPS接收机性能有5 dB的改善。

An improved PN code acquisition algorithm in condition of large frequency offset

For PN code acquisition in condition of large frequency offset, an impr oved PN code acquisition algorithm is provided, which is joint code acquisition algorithm based on spectrum line interpolation. Firstly, current PN code acquisi tion technologies are analysed. Secondly, on the basis of part correlation with FFT for PN code acquisition, joint code acquisition algorithm based on spectrum line interpolation is proposed. The core idea of algorithm is part correlation w ith FFT and precise estimation for carrier frequency offset with interpolation f ormula,thus making carrier tracking loop work better. Working principle of ne w code acquisition system is introduced, and expression of estimation for carrie r frequency offset is deduced. Non-coherent accumulation technology is applied t o code acquisition system, so precision of estimation for frequency offset in lo w SNR condition is improved. Finally, it shows that performance of current GPS r eceiver is improved by 5 dB through simulation.