基于快速OPAST算法的直扩信号PN码序列估计

摘要

In direct sequence spread spectrum ( DSSS) communication countermeasure systems,the blind es-timation of pseudo-noise ( PN) sequence is an important research subject. A blind estimation approach of PN code sequence is proposed based on fast orthogonal projection approximation subspace tracking( OPAST) al-gorithm and sliding window technique,thus solving the problem that the weight vector does not converge in some cases. The main eigenvector is extracted by OPAST algorithm,and sliding window technique is used to realize the code synchronization when the received DSSS signals are asynchronous and divided by wide win-dows. It guarantees the orthonormality of the weight vector at each iteration and fast convergence properties, and also solves phase ambiguity. It has the advantage of lower complexity,less storage and easier realization in hardware and real-time processing. Simulations show that the proposed algorithm can estimate the PN code sequence effectively and accurately in low signal-to-noise ratio( SNR) condition(-10 dB) .%在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题.针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS信号按照宽窗口分段,利用快速OPAST算法提取主特征向量,滑动窗技术实现码同步.该算法迭代权值向量具有正交性以及良好的收敛性,同时解决了常见相位模糊问题.算法具有较低复杂度,数据存储量少,易于硬件实现与实时处理.仿真结果表明,在-10 dB的较低信噪比背景环境中,该快速OPAST算法可以正确有效地估计出PN码序列.