Research On Interference Detection Technology Based On Time-frequency Analysis In GNSS Receiver

Global Navigation Satellite System(GNSS)is a system to achieve the function of positioning and navigation by space satellites.The navigation signal broadcast by satellites is weak,and Direct Sequence Spread Spectrum(DSSS)system is used to improve its signal to noise ratio.However,once the power of interference signal exceeds the interference tolerance of the system,the navigation and positioning performance of GNSS receiver will decrease significantly.Therefore,the anti-jamming capability of the receiver is very important,it mainly depends on the signal reception and processing environment.This paper researches the anti-jamming technology of the satellite navigation receiver from the perspective of signal processing.Two time-frequency analysis methods,reassigned wavelet transform and Fractional Fourier transform,are applied to detect frequency sweeping interference.The feasibility and effectiveness of the two algorithms are verified by simulation.Firstly,the system structure and communication mode of satellite navigation signals are analyzed with GPS as an example.Then it introduces two kinds of interference signal(pulse interference and frequency sweeping interference)and the interference detection and suppression methods.In order to eliminate frequency sweeping interference,defects of several time-frequency analysis algorithms in interference detection,such as spectrum,Wigner-Ville distribution and wavelet transform,are analyzed.To overcome the shortcomings of traditional time-frequency analysis algorithms in the detection of frequency sweeping interference,reassigned wavelet transform is adopted to improve the time-frequency aggregation,and great energy aggregation of frequency sweeping interference can be obtained by using Fractional Fourier transform.The simulation results show that the proposed algorithms are effective for the detection of frequency sweeping interference.