| Spread spectrum communication can effectively use of bandwidth and power in digital communication; it also has a certain safety performance. Chaos theory has become an important research content of nonlinear science in recent years. As one of the hotspot of research in communication, chaotic spread spectrum communication has wide application prospects. Then, in the receiver of communication system, how to recover carrier fast and accurately also is an eternal task.This paper based on the project of weak signal detection, we emphatically propose a design method of hybrid chaotic spread spectrum sequence, and simulated Costas loop in Simulink, which is the key link in carrier recovery.Firstly, we introduced the battlefield communication environment and technology, the application prospect of chaotic spread spectrum communication in battlefield security communication, the basic theory, history, definition and characters of chaos, the three chaotic-maps most commonly been used, and the digital quantized methods of chaos-maps.Secondly, based on the predecessors' research and work, we summarized disadvantages of the chaotic spread spectrum sequence design methods using a single chaotic-map. Then we put forward a hybrid chaotic spread spectrum sequence design method especially in the paper. Get parameters of the hybrid system through a large number of experiments. The sequence generated by the system not only follows uniform probability distributions, but also can pass Diehard test. And this performance can't appear in the design method which is using a single chaotic-map.Thirdly, we introduced the importance and key technique of carrier recovery in the spread spectrum communication, especially in Doppler frequency shift condition. And then we introduced Costas loop in the paper.Finally, according to project requirement, we simulated Costas loop in Simulink with a lot of different parameters. And the result is satisfactory. |
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