Research And Implementation Of Interference Recognition And Direction Finding Technology In BeiDou Navigation Satellite System

BeiDou Navigation Satellite System(BDS)is a global active satellite positioning and communication system(GNSS)developed and built by China.It has been widely used in national defense and economic development.The received signal of BDS on the ground segment is challenged by human-induced interference signals.Interference recognition and direction finding technology can obtain information such as the type,spatial distribution and source orientation of interferences,which is one of the key technologies to improve the availability of satellite navigation systems.Based on the review of the research situation of interference recognition and direction finding technology both at home and abroad,the jamming recognition algorithm is designed and implemented according to characteristics of jamming,and the direction finding technology of non-coherent interference is studied in this thesis.The main work is as follows:1.The working principle of jamming is given.The common jamming is modeled,and the time and frequency domain characteristics of jamming are analyzed;2.A jamming recognition algorithm for BDS is proposed.Based on decision tree theory,the proposed algorithm can recognize the jamming of BDS accurately according to characteristic parameters such as energy factor,interference 3dB bandwidth,spectral kurtosis coefficient,time domain kurtosis coefficient,normalized spectrum impact partial standard deviation,fractional Fourier transform energy aggregation degree.The proposed algorithm was simulated with MATLAB.The simulation results show that the algorithm has reasonable recognition accuracy even under low JNR.3.Based on FPGA hardware platform and Verilog-HDL,the circuit design and development of the jamming recognition algorithm for BDS is completed.The performance of the jamming recognition algorithm was tested by Chipscope online logic analyzer.The test results show that in the case of low JNR,the recognition accuracy of the algorithm for linear frequency modulation interference reach more than 80%,and the recognition accuracy for other jamming reach more than 90%;4.An interference direction finding algorithm for BDS is proposed.Based on B3 half-wavelength four-element rectangular array antenna,the MVDR beamformer and MUSIC algorithm were used to find incident direction of jamming.The proposed direction finding algorithm was simulated with MATLAB.The simulation results show that under ideal conditions,the the direction finding error of is azimuth less than 2°,and the direction finding error of pitch angle is less than 1°.Under non-ideal conditions,the gain and phase error of the array antenna will affect the direction finding accuracy.