面向中频的短码直扩信号数字盲解扩算法

Digital blind despreading algorithm for IF short code DSSS signal

针对直接序列扩频(direct sequence spread spectrum,DSSS)信号盲解扩问题,现有的方法大多基于矩阵分解理论,抽取主特征向量进行解调进而恢复伪码波形。非合作接收条件下,由于伪码波形未知且信噪比极低,载波频率、相位信息往往难以精确估计。考虑非合作接收条件,伪码未同步且含有随机载波频偏,现有方法常对两倍长度的复基带分段相关矩阵进行分解,带来了极大的计算资源消耗,并且存在性能退化等问题。本文提出了一种面向中频的短码DSSS信号数字盲解扩算法,分析了载波残余对伪码波形同步的影响,并通过中频实矩阵分解重构了伪码波形,最后针对含任意载波残余的DSSS二进制相移键控(DSSS-binary phase shifted keying,DSSS-BPSK)信号,设计了完整的从波形到比特的低复杂度盲解调解扩流程。仿真结果表明,所提算法拥有更好的误码率性能以及良好的载波参数鲁棒性。

Aiming at the problem of the blind despreading for direct sequence spread spectrum(DSSS)signal,existing works are mostly based on matrix decomposition theory,and the principal eigenvectors are extracted and demodulated to recover the pseudo-noise(PN)code waveform.Under the non-cooperative reception occasion,the carrier frequency and phase information are almost impossible to estimate accurately due to the unknown PN code waveform and extremely low signal to noise ratio(SNR).Considering the non-cooperative reception occasion with unsynchronized PN code and stochastic carrier frequency offset,current methods usually decompose the complex baseband piecewise correlation matrix with twice the length.It brings problems such as huge computing resource consumption and performance degradation.A digital blind despreading algorithm for intermediate frequency(IF)short code DSSS signal is proposed.The influence of residual carrier to PN synchronization is evaluated and the PN waveform is reconstructed by decomposing the IF real matrix.Finally,the low complexity blind despreading and demodulating process from waveform to bit for DSSS-binary phase shifted keying(DSSS-BPSK)signal with any residual carrier is designed.Simulation results verify the better bit error rate(BER)performance and robustness to carrier parameter of the proposed algorithm.