带残余载波的周期长码直扩信号PN码盲估计

针对下变频后含有残余载波的周期长码直扩信号PN(Pseudo-Noise)码盲估计难题，在已知码片速率和PN码周期前提下，该文提出一种结合矩阵特征值分解和数字锁相环(Digital Phase Locked Loop, DPLL)的PN码盲估计方法。该方法首先将带有残余载波的周期长码直扩信号等效建模为虚拟多用户短码直扩信号模型，利用矩阵特征值分解和模糊酉矩阵的方法估计出含有残余载波的PN码，然后利用DPLL对残余载波的频率和相位进行跟踪和估计并最终消除残余载波，最后根据特定约束条件（如m序列、Gold序列）去除分段相位模糊，最终估计出PN码序列。理论分析和仿真结果表明，提出的方法能够有效地工作在较低信噪比下，且表现出良好的性能。 

Blind Estimation of PN Codes for Periodic Long-code DSSS Signals with Residual Carrier

With focus on blind estimation of the PN(Pseudo-Noise) codes for periodic long-code Direct Sequence Spread Spectrum(DSSS) signals with residual carrier after down-conversion, a blind estimation approach of PN codes is proposed based on Eigenvalue Decomposition and Digital Phase Locked Loop(DPLL). The chip rate of the PN code and the PN codes period need to be known. Firstly, the periodic long code DSSS signal with residual carrier is equivalently modeled as a virtual multiuser short code DSSS signal model. The PN codes with residual carrier can be estimated by the matrix eigenvalue decomposition and fuzzy unitary matrix methods. Then, a DPLL is used to track and estimate the frequency and phase of the residual carrier, and remove the carrier frequency in the end. Finally, the PN codes can be estimated by removing its segmentation phase ambiguity with the condition of the specific constraint(such as m sequence and Gold sequence). Theoretical analysis and simulation show that the proposed approach can work effectively under low SNR and exhibits good performance