说明：  MATLAB自带的函数XCORR好象有点像卷积,如果要是求一个PN序列的自相关,我看一般的资料都是用我这个办法求PN序列相关的。
(MATLAB comes with seems a bit like a function XCORR convolution, if the request if the autocorrelation of a PN sequence, I see the general information are seeking ways to use my PN sequence related.)