GPS频域并行码捕获改进算法

Improved Frequency Domain Parallel Code Acquisition Algorithm for GPS Signal

针对基于FPGA平台的GPS L1信号的软件接收机捕获实时性差的问题,设计并实现了改进的GPS信号频域并行码相位捕获算法。首先分析了频域并行码相位捕获的理论模型,在此基础上采用平均采样方法对5 714点的数据进行下采样,平均采样后为1 024点,用Altera FFT IP核实现1 024点数据的FFT计算,实现算法的改进。利用ModelSim进行了仿真,仿真结果表明改进的算法降低了运算量,极大地提高了捕获速度,尽管平均采样造成了一定的C/A码相位误差,但不影响跟踪的结果,保证了捕获的正确性。

This paper proposes an improved frequency domain parallel code acquisition algorithm for GPS L1 signal, which could overcome poor acquisition real-time of GPS software receiver based on FPGA. According to the frequency domain parallel code acquisition algorithm, the improved algorithm samples 5 714 points of data to 1 024 points during one period using average sampling technique. Subsequently, we utilize Altera FFT IP core to work out Fourier transform of 1024 points of data. Simulation experiment implemented to test the optimized algorithm by using ModelSim simulator. Simulation results indicate that the proposed approach could obviously reduce the calculating amount and largely increase acquisition speed. It doesn＇t affect the final result of tracking process because only a little C/A code phase errors exist.