关键词: 直接序列扩频, 延时相乘法, 多重自相关, 长伪码

Abstract: Due to its low power spectral density，the Direct Sequence Spread Spectrum signal（DSSS） is always submerged with the back-ground noise，so that it is difficult to reconnoiter the signal.So a kind of method of the long Pseudo Noise（PN） code estimation for DSSS signal is proposed to detect the period，the chip rate and the carried frequency based on the delay-multiply multi-autocorrelation.Firstly，delay-multiply signal can detect the chip rate and the carried frequency in the frequency domain through multi-autocorrelation.Then，the period of the long PN code can be detected through multi-autocorrelation based on the band-pass filter.This method can estimate not only the chip rate and the carried frequency but also the period of the long PN code，and boost up the sensitivity of the detection to some extent.At the same time，the applicability of multi-autocorrelation of delay-multiply signal is deduced，and the theory can testify that the validity of estimation is not in proportion to the times of multi-autocorrelation.The more times of multi-autocorrelation don’t mean the better estimation.The validity of this method is shown by the computer simulation.

Key words: direct sequence spread spectrum, delay-multiply, multi-autocorrelation, the long pseudo noise code