Mathimatical Processing Of Weak Signal Detection In Non-coorperate Communication System

In the preface of this paper, and our main work and results in this paper are summarized.In chapter 2, we introduce the basic conception of signal dectection and main ways. In sucession, the basic concept of DSSS signal ,its modulation and detection.In chapter 3,In order to detect the unknown weak frequency modulation signal and increase the possibility of detection in a non-cooperative communication system we propose a pretreatmental way includes cutting, copying and spreading A Chaotic detection system describe by Duffing function is sensetive to weak period signal and no sensitive to Gauss White Noise. Combine this two ways we detect the the unknown weak frequency modulation signal from strong noise in a non-cooperative communication system.In chapter 4, To detect the DSSS signal hidden in strong noise, based on the Center Limit Theorem and the Big Number Law, we proposed a method so-called "Second-order Sampling and Reconstruction" (SOSR) to increase the signal to noise ratio (SNR). For this aim, after reducing noise by second-order sampling, some sets of first-order sampling (FOS) points are produced from the results of seconde-order sampling, and then the signal is reconstructed from the first-order sampling points. This method can effectively increase the SNR. With SOSR, we can detect the existence of spread spectrum sequence (DSSS) signal in non-cooperative communication and even describe its form clearly.