Research On A Covert Satellite Communication System

The satellite overlap communication discussed in this dissertation works in a special manner, whose signal is designed so weak that it can be overlapped on the signals of satellite’s transparent transfers, but does not affect their normal running, is a covert satellite communication system. This dissertation emphasizes particularly on a new satellite overlap communication based on multi-level PN code and the technology of M-ary spread spectrum.The main work of author is as follows:1. Based on deep analysis of the communication technologies of detecting and incepting, the ways to improve communication invisibility is presented.2. Study the basic characteristics of Golay complementary sequences and the method to generate LS code. Discover a new character of LS code and prove it to be right. The method to generate a new multi-level PN code, which can be used in the M-ary spread spectrum to improve communication invisibility, is presented in this dissertation.3. Study the technologies of narrow band interference suppression in spread spectrum systems. And a scheme for the satellite overlap communication system is designed.4. Study the technologies of PN code acquisition in spread spectrum systems. And an improved approach for PN code fast acquisition under great frequency offset situation is presented.5. Study the technologies of PN code tracking in spread spectrum systems. And a joint estimation of carrier phase and symbol timing loop based on Decision-direct is proposed.