Research On Key Techniques Of Short Burst Frequency Hopping Transmission System

Frequency hopping communication system has been widely concerned because of its excellent anti-interference and anti-interception performance.Short burst frequency hopping communication systems based on traditional frequency hopping communication have the characteristics of short duration of each hop,strong randomness and good signal concealment.In the process of real communication,there will always be various kinds of interference,such as carrier frequency offset,multipath interference and some man-made malicious interference.If these interferences can’t be eliminated efficiently,the communication quality will be greatly affected.To solve the above problems,the estimation of carrier parameters,elimination of multipath interference and anti-frequency interference in short burst frequency hopping communication system are studied in this thesis.The relevant knowledge of TCM-CPM modulation,including the advantages of TCM-CPM modulation and its modulation and demodulation principle are firstly introduced in this thesis.Then,some common carrier parameter estimation methods are introduced,including time domain carrier parameter estimation method and frequency domain carrier parameter estimation method,and the estimation performance of various methods is compared by normalized mean square error.The influence of rotating factor on the estimation performance of RPA algorithm is analyzed.Then,the influence of multipath fading on the communication process is introduced.Based on the existing MLSE equalization algorithm of TCM-CPM signal,an improved combined equalization and demodulation algorithm of TCM-CPM signal in multipath channel is proposed.The algorithm uses the combined equalization and demodulation result of the first time as a reference signal to assist the second demodulation through two combined equalization and demodulations,so that the multipath interference can be better eliminated.Through the simulation analysis of the bit error rate of the two algorithms,the improved algorithm can eliminate multipath interference to a greater extent and reduce the bit error rate compared with the existing algorithm.Finally,for the malicious interference in the communication process,some existing anti-jamming methods are introduced from multiple perspectives.In this thesis,the RS code is combined with the short burst frequency hopping technique,and the characteristics of the RS code itself are used to enhance the system’s anti-interference performance.The frequency interference is simulated by randomly adding high-power noise.The simulation results show that for the interference that does not exceed the error correction capability of the RS code,it can effectively resist the influence of the interference to the system.Once the number of interfered frequency points exceeds the error correction limit of the RS code,then the receiving end will not be able to demodulate and decode correctly,and the communication quality will be greatly disturbed.At the same time,the performance of the improved combined equalization and demodulation algorithm of TCM-CPM signal in multipath channel proposed in this thesis is also simulated and analyzed in the presence of frequency interference.The simulation results show that in the presence of frequency interference,the demodulation algorithm proposed in this thesis can still effectively eliminate multipath interference and reduce the bit error rate.At the same time,it is verified that the antiinterference performance of the system is improved after cascading RS codes.