Research On Fractional Time-Frequency Analysis Based Anti-Interference Techniques For GNSS Receivers

The Global Navigation Satellite System(GNSS)has been widely used in people's daily lives,but with the heavy use of radios,the overlapping of spectrum,and urban multipath effects,it has brought serious interference problems to GNSS receivers.At present,for the anti-jamming research of satellite navigation,processing from the signal level is the most effective and direct anti-jamming method.The thesis starts from the level of signal processing,regarding the shortcomings of the traditional timefrequency analysis(Short-Time Fourier Transform,Wigner-Ville Distribution)antiinterference method,it is proposed to use Fractional Time-Frequency analysis to study the anti-interference technology of the navigation signal,Specifically,Fractional Fourier Transform and Fractional Wavelet Transform are used to perform interference detection and anti-interference on sweep interference.,and carry out corresponding algorithm simulation.The simulation results verify the correctness and effectiveness of the proposed algorithm.Specifically,the main contribution of this thesis are as follows:(1)For navigation satellite receivers that are susceptible to the sweep interference,a Fractional Fourier Transform is used to detect interference and resist interference,and an algorithm simulation is performed.Specifically,the traditional Time-Frequency analysis method is introduced first,and then the theoretical basis of applying the Fractional Fourier Transform to the navigation satellite receiver is analyzed.For the scientific problem of calculating the optimal order of fractional order,from timefrequency analysis Based on the analysis of the Time-frequency Bandwidth Product,an optimal order calculation method is proposed.At the same time,in the presence of single-component and multi-component sweep interference,were discussed separately,and the algorithm flow was designed.The Simulation results show that,based on the proposed optimal order calculation method,The Fractional Fourier Transform has obvious interference detection and anti-interference effects on the navigation satellite receiver compared with the traditional Time-Frequency analysis algorithm.(2)For navigation satellite receivers,in addition to being susceptible the sweep interference,it will also be affected by noise.The use of Fractional Wavelet Transform for anti-jamming research is proposed,and algorithm simulation is designed.Specifically,the research status and three implementation methods of Fractional Wavelet are introduced first,and one of them is selected for theoretical analysis,that is,the advantages of fractional order domain to deal with sweep frequency signal and the advantages of wavelet transform multi-resolution.In the case where there is both sweep interference and noise on the navigation signal,a fractional order wavelet antiinterference algorithm flow is designed.Based on the proposed optimal order algorithm,the simulation results show that the Fractional Wavelet can not only deal with the sweep interference,but also have the function of denoising,and it has more obvious advantages compared with other Time-Frequency analysis algorithms.