基于平均相关和差分相干累积的微弱GPS C/A码信号精密捕获算法

针对弱信号条件下GPS C/A码捕获问题，提出一种基于平均相关和差分相干累积的码捕获算法。首先，引入相干能量最大值与第二大值的比值作为判决变量，仿真了各种捕获算法的虚警概率得到最佳的判决门限；然后，通过设置的判决门限获得不同多普勒频率偏差及信噪比条件下的检测概率；最后，比较了所提差分相干累积算法、相干非相干累积算法以及非相干累积算法的捕获灵敏度。仿真实验表明，在相同接收数据长度的情况下，采用差分相干累积算法比其他2种算法提高捕获灵敏度约2 dB。

Fine C/A code acquisition algorithm for weak GPS signal based on averaging correlation and differential coherent accumulation

Aiming at the problem of global positioning system (GPS) C/A code acquisition under weak signal conditions, a code acquisition algorithm based on averaging correlation and differential coherent accumulation was proposed. First, the strength ratio of the largest peak to the second largest peak was adopted as the decision variable; optimum decision thresholds can be obtained through the simulation probability of false alarm of all kinds of acquisition algorithms. Second, by setting the decision threshold, the probabilities of detection of different Doppler frequency deviation and signal to noise ratio (SNR) were obtained. Finally, acquisition sensitivities of the code acquisition algorithm based on the differential coherent accumulation were compared with those of the code acquisition algorithm based on coherent and noncoherent accumulation and the code acquisition algorithm based on noncoherent accumulation. Simulation results show that acquisition sensitivities of the code acquisition algorithm based on the differential coherent accumulation are improved by about 2.0 dB than those of the other two acquisition algorithms under the same receiving data length condition.