带残余频偏的QPSK-DSSS信号伪码序列盲估计

Blind Estimation of Pseudo-Code Sequence of QPSK-DSSS Signal with Residual Carrier

针对正交相移键控(QPSK)调制的带残余频偏直接序列扩频(DSSS)信号伪码序列难以估计的问题,提出信号相关矩阵特征分解结合全数字锁相环(DPLL)进行伪码序列估计的方法。首先对接收信号进行采样和分段得到数据矩阵;根据最大化信号相关矩阵的谱范数估计出伪码序列的同步点;在同步基础上再计算信号相关矩阵的特征子空间;针对其主分量特征向量带有残余频偏且相位存在π/2跳变的问题,采用全数字锁相环跟踪和消除其残余频偏进而恢复伪码序列。研究结果表明,针对QPSK-DSSS信号,所提方法能够实现负信噪比下伪码序列的盲估计。

To solve the estimation difficulties of pseudo-code sequence of direct sequence spread spectrum(DSSS) signals with quadrature phase shift keying(QPSK) modulation with residual carrier, a method of pseudo-code sequence estimation is proposed based on signal correlation matrix eigendecomposition combined with all digital phase locked loop(DPLL). First, the received signal is sampled and segmented to obtain the data matrix. Then, the synchronization point of pseudo-code sequence is estimated by maximizing the spectral norm of signal correlation matrix. Based on synchronization, the characteristic subspace of signal correlation matrix is calculated. To eliminate the residual carrier of the eigenvector of the principal component and the phase change of π/2, a DPLL tracking and a residual carrie elimination are used to recover the pseudo-code sequence. The research results show that, for QPSK-DSSS signals, the proposed method can achieve blind pseudo-code sequence estimation under negative signal to noise ratio.