Research On Frequency Hopping Pattern Synchronization Technology Under Complex Electronmagnetic Environment

The significant and kernel of the frequency hopping communication system is frequency hopping pattern synchronization,so the performance of frequency hopping pattern synchronization directly affects the performance of the frequency hopping communication system.With the increase in the hopping speed of frequency hopping communication,higher requirements are put forward for the synchronization of frequency hopping patterns in a complex electromagnetic environment.At the same time,since frequency hopping communication systems always work in a complex electromagnetic environment,which is a scene where low signal-to-noise ratio and interference co-exist,it is important to achieve fast frequency hopping pattern synchronization in low signal-to-noise ratio and interference environment.The specific realization of frequency hopping pattern synchronization can be divided into two processes of acquisition and tracking,and focus on the two processes of acquisition and tracking will be studied.The main content of the thesis is as follows:First,the basic principle of frequency hopping communication system is introduced,the principle of frequency hopping pattern synchronization is explained,and then the fast outgoing capture methods are explained,including partial correlation matched filtering method,two-level capture method,TOD synchronization prefix in the synchronization capture of frequency hopping pattern and based on the frequency estimation acquisition method.The delay phase locked loop,the jitter phase locked loop and the principle based on the Maximum Likelihood(ML)criterion algorithm in the synchronization tracking process of the frequency hopping pattern are briefly introduced.The common interference of frequency hopping communication system,including partial frequency band interference and tracking interference are described.Secondly,focus on the acquisition algorithm based on frequency estimation,and propose a frequency estimation algorithm based on the Variable Forgetting Factor Recursive Least Square,(VFFRLS)algorithm,and perform numerical simulation analysis in a low signal-to-noise ratio environment.The results show that the frequency estimation algorithm based on VFFRLS has better anti-noise performance.The H~?theory is used to analyze the robustness of the frequency estimation algorithm based on VFFRLS,and the upper and lower bounds of the input signal estimation error of the frequency estimation algorithm based on VFFRLS are deduced to verify the feasibility of the algorithm.Numerical simulation analysis is carried out under the comprehensive environment of Gaussian white noise and partial band interference.The results show that the frequency estimation algorithm based on VFFRLS has relatively small frequency estimation error.Aiming at the problem that the original capture algorithm prolongs the capture time when the frequency estimation error occurs,an error correction capture algorithm is proposed.The state value of the linear feedback shift register is constructed with the effective bits of three consecutive hops,thereby increasing the correct probability of the state value.In the environment of Gaussian white noise and partial band interference,the error correction capture algorithm and the original capture algorithm are compared and simulated.The results show that the capture probability of the error correction capture algorithm is higher than the original algorithm,and the error correction capture algorithm is lower than the original algorithm.The signal-to-noise ratio environment significantly decreases the average capture time.Finally,study the tracking algorithm of frequency hopping pattern synchronization,including delay phase locked loop,jitter phase locked loop and algorithm based on ML criteria for comparative analysis,and the tracking speed,jitter performance and the loss-of-lock performance was verified by comparison and simulation under the environment of Gaussian white noise and partial band interference.