一种低输入信噪比和低恒虚警约束下的PN码快捕算法

A Fast PN Code Acquisition Algorithm with the Constraints of Low Input Signal Noise Ratio and Low Constant False Alarm Probability

针对短帧突发模式下直接序列扩频(DSSS)通信系统要求在有限时间内以很低虚警和漏警概率捕获PN码相位这一难题,提出了一种基于数字匹配滤波器(DMF)的多码元非相干累加单次驻留检测的PN码快速捕获算法。它在传统单次驻留算法的基础上,用多码元累加来提高码相位判决量的信噪比,从而大大降低了低输入信噪比和低恒虚警约束下的平均捕获时间。分析了该算法在QPSK-DSSS系统下的捕获性能,仿真结果证明了该算法可以在低信噪比和低恒虚警条件下实现PN码的快速捕获。

Pseudo noise（PN） code acquisition with very low false alarm and miss probability in a limited period of time is required for the short frame burst-mode direct-sequence spread-spectrum （DSSS） communication systems. A novel noncoherent approach, based on multi-symbol accumulation-to-PN code acquisition and digital matched filters （DMFs）, was proposed to solve the problem. It is an improved mode of the traditional DMF single dwell algorithm. By using the method of multi-symbol accumulation, the proposed algorithm can increase the signal-noise ratio （SNR） of code phase detection statistics, so the mean acquisition time is greatly shortened under the constraints of low input SNR and low false alarm probability. Its performance in QPSK-DSSS systems was analyzed. The simulation resuits show that the proposed algorithm is able to capture PN code fast under the constraints of low SNR and low false alarm probability.