Spread Spectrum Signal Detection And Parameters Estimation

Spread spectrum communication has a good performance in aspects of anti-jamming, anti-intercepting and secret-keeping. It is widely used in military communication domain, such as military transceivers and tactical data link. Spread spectrum signal reconnaissance becomes the important fighter means of military communications counter-measures. Spread spectrum signal reconnaissance includes three main parts: signal modulation classification, signal detection and signal parameters estimation. This dissertation focuses on spread spectrum signal detection and parameters estimation including direct sequence spread spectrum (DS-SS) signal detection and parameters estimation, hopping-frequency signal detection and parameters estimation.DS-SS signal is a kind of special non-stationary signal. It presents a characteristic of cyclostationary. Firstly, the non-stationary of DS-SS signal is analyzed. Secondly, based upon Delay-and-Multiply device, the best DS-SS carrier detector is proposed. On the condition of the known part of parameters about signal, the best detector is matching-filter energy detector; And On the condition of any unknown parameter about signal, detector reaches the best performance when d= 0.4/B, which d is time delay, B is bandwidth of band-pass filter. Then, the theoretic precision of DS-SS signal estimation is analyzed. The Cramer-Rao lower limit of carrier frequency estimation, chip rate estimation and symbol rate estimation are proved. Finally, based upon ambiguity function, a new united estimation method is proposed. It has good performance even at very low SNR. Along with the increasing of observational time, estimation performance can be improved.Now, hopping-frequency signal detection and parameters estimation methods become mature. The cross terms of hopping-frequency signal which affects time-frequency estimation precision is analyzed. The position of cross terms is proved. And an amelioration method of time-frequency estimation is proposed.The Joint Tactical Information Distribution System (JTIDS) adopts hopping-frequency, DS-SS and hopping-time technology. It has a good performance on anti-reconnaissance, anti-jamming and anti-intercepting. Physical layer of this system is simulated. And multiple-hop autocorrelation detection of JTIDS signal is simulated too.