高动态弱直扩信号的分级捕获算法

A Hierarchical Acquisition Algorithm for High Dynamic Weak DSSS Signals

针对低信噪比高动态环境下直扩信号经典捕获算法中多普勒频偏估计精度和快速傅里叶变换(FFT)运算量的矛盾,提出了一种基于频偏补偿的两级非相干累加捕获算法。该算法以部分匹配滤波器结合快速傅里叶变换(PMF-FFT)算法为单元,首先利用第一级频偏粗估值对多普勒频偏进行补偿,然后通过调整第二级PMF-FFT中部分匹配滤波器长度并利用滑动平均窗对残余频偏进行精估。理论分析和仿真结果表明,与经典捕获算法相比,该算法在FFT运算点数相同的条件下,可以有效地提高多普勒频偏估计精度,并且在高动态环境下具有更好的检测性能。

To solve the contradictions between Doppler frequency offset estimation accuracy and fast Fouriertransform（FFT） operation points in classical acquisition algorithm for direct sequence spread spectrum（DSSS） signal in high dynamic environment with low signal-to-noise ratio（SNR）,this paper proposes atwo-stage noncoherent integration acquisition algorithm based on frequency offset compensation. This algo-rithm is based on the partial match filter combined with FFT（PMF-FFT）. Firstly,Doppler frequency offsetis compensated by coarse frequency offset estimation. Secondly,through adjusting subsequent PMF lengthand adopting the moving-average technique,the residual frequency offset is accurately estimated. Both a-nalysis and simulation show that,compared with classical acquisition algorithm,the proposed algorithm caneffectively enhance the accuracy of Doppler frequency offset estimation when FFT operation points are thesame,and has higher detection performance in high dynamic environment.