高动态条件下伪随机码捕获的旁瓣虚警分析

Side-lobes false alarm of acquisition of PN code under high dynamics

摘要:

采用Matlab对扩频码的自相关旁瓣在载波频差条件下的改变情况进行了仿真，可以看出自相关旁瓣峰值和均值随载波频偏的变化发生了较为明显的改变，在0 kHz~1 kHz范围内变化最为明显，在1 kHz~10 kHz范围内变化幅度较小，成波浪起伏变化。同时自相关旁瓣的变化，导致系统捕获时的虚警概率也发生了相应变化，进而导致虚假捕获。而在采用自适应门限情况下，虚警概率大大降低，因此在实际情况中，基于高斯分布的固定门限不是最佳选择。

Abstract:

This paper emulates the changes of autocorrelation side lobe for spreading code by Matlab under the condition of the carrier frequency offset. It can be found that the peak and averaged values of autocorrelation side lobe change greatly as the carrier frequency offset changes，and the change is most obvious in 0 kHz–1 kHz. At the same time，the change of autocorrelation side lobe results in the change in the false alarm probability of the system correspondingly，and then led to a false acquisition. Nevertheless，the false alarm probability decreases greatly when adopting self-adaptive threshold. Therefore，the regular threshold based on Gauss distribution is not the best option in actual condition.