GPS软件接收机捕获方法研究

ACQUISITION ALGORITHM FOR GPS SOFTWARE RECEIVER

为解决GPS软件接收机中频信号的捕获问题,首先基于FFT的并行码捕获实现了对基带信号的粗捕,对粗捕的捕获判决进行改进,采用自适应门限值调整方法,即基于次高峰判决,同时对次高峰的寻找采用开窗原理;然后利用FFT的频域分析方法进行精捕。与传统相位差分精捕不同,利用FFT频域内对中频信号进行精捕,通过增大FFT变换的点数来提高精捕频率的分辨率,同时具体给出了粗捕和精捕的具体捕获步骤以及主要的技术问题;最后利用一组GPS实测数据对上述分析进行了计算,实验结果表明:基于FFT的GPS信号的粗捕与利用FFT的频域精捕方法非常有效,捕获快速准确,可以满足GPS软件接收机的要求。

To solve the IF signal capture problems in the software GPS receiver,first the parallel code acquisition algorithm based on FFT is used to achieve the coarse frequency of IF signal and obtain the fine frequency based on the use of FFT in frequency domain analysis.The acquisition decision is dependent on the ratio of the maximum peak and the sub-peak ratio,at the same time,the specific steps are presented.Through the analysis of the real GPS IF signal,experimental results show that the FFT-based GPS signal acqusition and FFT frequency-domain method are very effective to obtain the fine frequency,this is,can capture quickly and accurately,so to meet the requirements of GPS software receiver.