基于位同步点未知的GPS长码直捕算法研究

Research on GPS Long-code Acquisition Method Based on the Unkown In-phase Point

基于位同步点未知的GPS长码直捕算法是基于存储的滑动相关搜索,并利用FFT将时频二维联合搜索变成时域一维搜索。同时,不考虑位同步点的因素,接收资源池只需存储一段接收序列,成倍地缩短了捕获时间且利于硬件实现。针对极性反转带来额外的信噪比损耗以及‘频谱泄漏’问题,简要提出了解决办法。仿真结果表明,多普勒频移为±3 kHz时,所带来的峰值衰减为2 dB左右,本地信号与接收信号对齐时出现明显的相关峰,较好地实现了捕获功能。

Based on the in-phase point is unkown and the data stored firstly, GPS long- code acquisition method makes the incoming signal and the local code slide correlated. Using the FFT,it can only search over the time uncertainty zone instead of the time- frequency planar zone. The resource pool receives one section of the data without regard to the in- phase point,it can reduce the acquisition time and benefit the hardware realization,present a method aim to the SNR loss caused by the code polar reversal and the ＂speetrum - leakage＂problem. The emulation results show the attenuation of the peak value brought by the Doppler effect is less than 2dB in the ease of Doppler offset is ± kHz,when the input signal and the PN code is synchronization,there is an obvious peak,and prove the method can meet the acquisition function well.