基于PMF-FFT的高精度伪码捕获算法

针对低信噪比、高动态环境下传统的伪码捕获算法捕获概率较低的问题,提出一种高精度的时频联合两轮频偏校正捕获算法.算法以两级PMF-FFT(Partial Match Filter-Fast Fourier Transform)捕获单元为模型,在不增加FFT点数的前提下对第一级增加差分相干累积模块提高信噪比,并运用时频联合频偏估计分别对信号进行两轮频偏校正,第二级输入经加窗处理,同时适当增加PMF长度,进一步提高捕获精度.理论分析和仿真结果表明,该算法与传统的PMF-FFT算法相比,有效地提高了多普勒频偏估计精度,且系统在低信噪比、高动态条件下捕获概率得到提升,具有良好的捕获性能.

High-precision Algorithm in PN Code Acquisition Based on PMF-FFT

Aiming at the shortage of performance of traditional partial match filter-fast Fourier transform(PMF-FFT) acquisition algorithm under low SNR(signal-to-noise ratio) and high dynamic environment, a high accuracy acquisition algorithm in time - frequen - cy domain and two-frequency offset compensation was proposed. The algorithm was based on the model of two level PMF-FFT acquisition unit, the first stage add differential coherent accumulation module to improved SNR without increasing in FFT points, and the two - frequency offset correction of the signal was carried out by using the joint frequency offset estimation, the second stage input through adopting the window technique and appropriate increasing PMF length to further improve the capture accuracy. Theoretical analysis and simulation results showed that, compared with the traditional PMF-FFT algorithm, the new algorithm effectively improve the accuracy of Doppler frequency offset estimation, and has higher capture performance under low SNR and high dynamic environment.