Research And Implementation Of Synchronization In Hybrid Spread Spectrum System

JTIDS (Joint Tactical Information Distribution System) is an information distribution system integrated with communication, navigation and identification, with the characteristics of large capacity, high speed, anti-interference, and high security. The synchronization techniques of the JTIDS'development system were the main contents of this thesis.First of all, the thesis introduces the principles of spread spectrum communication, especially investigates the system structure and features of hybrid spread spectrum communication. Next, some classic frequency, phase and timing synchronization algorithms based on maximum likelihood criterion were discussed, and the performance was simulated and compared. Furthermore, for the characteristics of MSK modulation, on one hand, the synchronization algorithm for nonlinear modulation was investigated, and on the other hand, the signal was decomposed by Laurent expansion to adopt the synchronization methods for linear modulated signals. Based on these theories and algorithms, two estimation algorithms were emphatically studied. A fully digital method for frequency and timing joint estimation of MSK signal was investigated, and simulated. Meanwhile, a joint estimation method for frequency, phase and timing of QPSK signal was analyzed, and the algorithm was improved based on the performance simulation, which had the features of low complexity, real-time processing and good performance. Finally, the MSK synchronization scheme was implemented with FPGA devices, and its hardware structure was optimized to utilize all kinds of resources in FPGA device more effectively.