Research On High Precision Strategy Of Radar Wave Refraction Correction

With the rapid development of UAV（Unmanned Aerial Vehicle）technology at home and abroad,the UAV market is gradually expanding,which has brought great convenience.However,there are also some serious problems.At present,a safe and reliable UAV control scheme is urgently needed in society.According to the technical index,the communication between uplink and downlink of most unmanned aerial vehicles on the market depends on FHSs（Frequency Hopping Signals）.Thus,the interference with FHSs is an indispensable part of UAV counter-system.In this thesis,the FHSs used in UAV communication system is interfered so that the communication between systems cannot be completed normally.Instructions such as left-turn and acceleration sent out by the communication system of UAV are realized by FHS transmission.So,FHS is the key to the operation of UAV system.Interference with FHS is one of the most valid methods in the research and development of Anti-UAV system.Due to the application of frequency hopping technology,the receiver cannot obtain the modulation mode,signal composition or other information of the signal if there is no cooperation agreement between the transmitter and the receiver.Thus,the receiver cannot get the information contained in the signal or interfere with it.In order to solve this problem,this thesis studies the parameter estimation of FHS on the basic of obtaining these signals to achieve the purpose of intercepting or interfering with frequency hopping signal.Firstly,this thesis explains the fundamental theory of frequency hopping communication system and deeply understands the elementary knowledge of FHS.It summarizes the performance of some traditional FHS analysis by reading many references and finally finds out the key and difficult points for future work.The simulation model of FHS is set up based on MATLAB for estimating parameters by the time-frequency analysis method.Secondly,the traditional time-frequency analysis method is used to simulate different kinds of FHSs,the time-frequency distribution performance is compared and summarized while using time-frequency analysis method to deeply study parameter estimation of FHSs.Through the simulation of some traditional methods and aiming at their advantages and disadvantages,it proposes a joint algorithm combining the advantages of STFT（Short Time Fourier Transform）and PWVD（Pseudo Wigner-Ville Distribution）.The UAV communication signal is transformed using STFT and PWVD（Pseudo Wigner-Ville Distribution）.After obtaining the calculation results of these two operations,a stable time-frequency analysis map is obtained based on the Hadamard product.The maximum time-frequency at each time is used to calculate the hop rate,and the reciprocal of it is the period value.Finally,the principles and operation process of broad Band blocking and tracking interference are introduced,and the interference simulation system of UAV frequency hopping communication system is set up by Simulink module of MATLAB.Simulation of two jamming methods is carried out under different SNRs（signal-to-noise ratios）.Through the data comparison and analysis of the results,the advantages and disadvantages are analyzed.The correctness and validity of the proposed study in this thesis is verified by the simulation.