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

摘要： 直接序列扩频信号具有较低的功率谱密度，信号淹没在背景噪声中，侦查难度较大。针对长伪码直接序列扩频（Direct Sequence Spread Spectrum，DSSS）信号伪码周期、码片速率、载频参数检测难题，提出了一种延时相乘多重自相关的综合性检测方法。首先对延时相乘信号进行多重自相关处理，在频域可以检测出信号的码片速率、载频。在此基础上，设置带通滤波器，同样经过多重自相关处理，可以检测出长伪码的周期。此方法不但可以检测出DSSS信号的码片速率、载频，而且可以同时检测出长伪码的周期，并在一定程度上提高了检测的灵敏度。同时对延时相乘信号多重自相关的适用性进行了推导，理论证明检测的效果与多重自相关的次数并不是成正比，即并不是多重自相关的次数越多，检测效果越好。仿真结果验证了其有效性。

关键词: 直接序列扩频, 延时相乘法, 多重自相关, 长伪码