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为了解决低信噪比直扩信号扩频码的盲估计问题,提出了一种直扩信号的协方差矩阵累加平均和离散卡洛(Karhunen-Loève,K-L)变换的方法。该方法是在已知直扩信号的扩频码周期、码速率等参数的前提下,将接收到的直扩信号以一随机确定值为起点进行周期分段以形成连续多个观察向量,求协方差矩阵并累加平均,实施离散K-L变换以得到信号所含主成分,由主成分特征向量估计观察信号的扩频码。而后对观察信号进行解扩处理,从而实现直序扩频信号的盲解扩处理。理论分析和数值结果表明了该方法非常鲁棒不易受噪声影响,在通常情况下可以工作于低于-20dB信噪比的环境下。
In order to solve the problem of blind estimation of DSSS spreading codes with low signal-to-noise ratio (SNR), a method of cumulative average and discrete Karhunen-Loeve (K-L) transformation of DSSS signals is proposed. The method is based on the known spreading code spread spectrum code cycle, code rate and other parameters under the premise of the received DS signal with a randomly determined value as a starting point for periodic segmentation to form a continuous multiple observation vector, seek Covariance matrix and cumulative average, the implementation of discrete KL transform to obtain the main components contained in the signal from the principal component of the eigenvector to estimate the observation signal spreading code. Then, the observation signal is despread, so as to realize the blind despreading processing of the direct sequence spread spectrum signal. Theoretical analysis and numerical results show that this method is robust and not susceptible to noise. Under normal circumstances, it can work under SNR below -20dB.