Abstract: 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.

Key words: spread spectrum communication, pseudo-code sequence blind estimation, quadrature phase shift keying, eigenvalue decomposition, phase-locked loop