Research On Some Key Techniques Of The Satellite Overlap Communication System

Satellite overlap communication is a means of military communication, whose spread-spectrum (SS) signal can be hidden in signals of other communication systems. Its main characteristics are high anti-jamming ability and high security. This thesis deals with a satellite overlap communication system which occupies less bandwidth than traditional systems by using M-ary spread-spectrum (M-ary SS) instead of direct sequence spread-spectrum (DSSS).The research focuses on the basic theories and key techniques of this M-ary SS overlap communication system's transmitter and receiver, as well as the realization of the receiver's digital signal processing algorithm with DSP. Based on these techniques, a prototype of the satellite overlap communication system has been developed. The test result shows that the system has good performance and high stabilization. The main contributions of this thesis are as follows:1. Based on deep research on the synchronization and de-spreading problems of M-ary SS, a new M-ary transmitting signal scheme is proposed, which adopts two-level SS code for synchronization and one-level cyclic code for de-spreading. It can greatly reduce the system's synchronization and de-spreading complexity.2. By analysis of the effect of frequency offset on M-ary SS, a synchronization algorithm containing frequency offset search is proposed. This algorithm has high synchronization speed and precision and can be easily implemented with DSP.3. A scheme to combine channel coding with M-ary SS is proposed, which can realize high quality data transmission.4. Based on software radio technique and a TMS320C6416 DSP hardware platform, a realization method of the receiver's software is proposed and used in the prototype of the satellite overlap communication system.