High Dynamic Spread Spectrum Communication System Synchronization Key Technology Research And Implmentation

Satellite mobile communication technology, as a new mobile communication technology with large coverage and communication capacity,plays an important role in today's image-based era of data communication, and promotes satellite communication technology and the whole information and communication industry to produce significant and profound evolution. As key technology in the communication system, synchronization plays a decisive role in the performance of the communication system. However, due to satellite communication channel limited power and frequency band, and low-earth orbit satellites in communication with the ground station facing with the low signal to noise ratio, large frequency deviation and fast frequency change rate conditions,There are many related research in synchronization problems of communication in recent years. This passage mainly refers to the study of synchronization acquisition algorithm, Doppler shift model and correlation estimation algorithm in satellite communication system. Combining with 863 project of data link distribution system based on high dynamic networking in laboratory, the following work is accomplished:(1) Design a baseband communication system structure for different orbiting satellites, and implement the theoretical simulation and realize the communication scheme of LEO satellite in hardware.(2) According to the Doppler shift of the low earth orbit satellites during the communication with the ground mobile station, the frequency offset compensation can be done by choosing the appropriate frequency offset compensation algorithm according to the error model.(3) According to the analysis of acquisition and acquisition time of the existing synchronization acquisition algorithm, a matching filter-fast Fourier transform algorithm is proposed, which is suitable for the environment with high dynamic and low SNR in satellite communication system. Simulation is carried out, and the hardware description language is used to simulate on Modelsim,which reduces the capture time and improves the precision of acquisition.(4) Design the communication interface between DSP and FPGA, including McBSP interface and EMIF interface, improve the communication processing capacity of the whole system, and make the design of transmitter and receiver more flexible, can adapt to different communication needs.