一种高灵敏度GPS信号快速捕获算法

为了提高GPS软件接收机捕获算法的灵敏度和快速性，提出了一种高灵敏度GPS卫星信号快捕方案。首先对GPS信号进行频率补偿，然后进行相干滤波提高卫星信号的信噪比，从而提高捕获算法的灵敏度。再采用延迟、累积捕获结构寻找输入信号中各颗卫星的C/A码起始点，引入延迟累加器实现各卫星多普勒频移成分的分离、估计，将传统的二维捕获过程简化为两个一维搜索过程，捕获时间仅为传统FFT快捕算法的几十分之一，提高了捕获算法的速度。分别通过实测和GPS数字中频信号发生器仿真生成的GPS数字中频数据对所设计的捕获算法进行了验证，实验结果表明该捕获算法行之有效。

A novel high sensitive fast acquisition algorithm of GPS signals

To improve the sensitivity and fast acquisition ability of a GPS software receiver, a novel acquisition scheme is presented. Firstly, by compensating the frequency of the intermediate frequency(IF) signal to improve its cyclicity, the signal-to-noise ratio(SNR) of the IF signal can be improved by using coherent average algorithm. So the sensitivity of acquisition algorithm is improved.Secondly,the C/A code start of every satellite is searched through the delay-multiply configuration, then the delay and accumulation unit is put forward to pretreat the multi-frequency signals.Finally, the separation and estimation of Doppler-shift components are fulfilled by frequency domain analysis on post-treatment signals,therefore, the two-dimensional searching process in conventional acquisition scheme is transformed into two one-dimensional searching processes in the proposed acquisition scheme. In the proposed acquisition scheme, a shorted fast Fourier transform(FFT) version is adopted, which can greatly reduce the computation burden without degradation on performance. Sampled data from GPS receiver and simulated GPS signals are used for simulation experiments. Simulation results indicate effectiveness of the proposed acquisition scheme.