On Detection Of The DS-based Embezzled Signal In Satellite Transmitters

The embezzlement detection is one of the big problems needed to be solved in satellite communication. There are mainly two cases in satellite sources embezzlement: one is transferring information using frequency band of the idle transmitters; the other adds DS signals to the normal operation signals to embezzle the satellite resources. There have already been some methods to solve the problems of the first case of embezzlement, but to the second, we still can not find refined method. So the research of DS signal embezzlement is very important and has meaningful potentials.This thesis study the DS signal detection, and also the detection of the embezzled signal in satellite transmitters, and put forward a combination method of SVD and cyclic-autocorrelation.The main jobs of this thesis include:(1) Introduce the importance and meanings of this topic, and give an overview of the recent researches of the DS signal detection.(2) Give out the fundamental principles and features of DS signal communication system. Briefly introduce some relevant information of satellite transmitters. Investigate on the communication module of the satellite transmitters which contains DS signal embezzlement. Also, introduce the DS signal embezzled communication principle diagram.(3) Put emphasis on the detection methods of DS signal, including second-moment method of auto-correlation, cyclic spectrum method, square frequency doubling method, quadratic spectrum method, and so on. The article induces the principle of DS signal detection and parameter estimation, and does computerized simulation for the first three methods, then gives the analysis of the simulation's results.(4) Put forward a combination method of SVD and cyclic-autocorrelation to detect the embezzled signal in satellite transmitters. The method can weaken the normal signal from the combined resource using SVD, then by using one-dimension splitter in the cyclic-auto correlation, it can detect the embezzled signal. The method can avoid the multi-dimension search, which improves the efficiency greatly. It provides a possible solution to the detection of satellite transmitters' embezzled signal.