GNSS Space Signal Monitoring Technology

In recent years,with the increasing attention of the Global Navigation Satellite System(GNSS),new strategic plans have been drawn up for the development of navigation systems.As the Beidou navigation of our country is about to be fully operational,the role of navigation in people's lives is increasing,and people have put forward higher requirements for the performance of navigation systems.The improvements in system performance include improved accuracy and completeness.During the navigation,the navigation signal may add ionospheric delay,multipath,noise,and wide and narrow band interference,which will inevitably lead to a decline in the performance of the global navigation satellite system receiver,and may even fail to determine the location.The existing navigation files contain information about the signal-to-noise ratio,ionospheric delay,and multipath errors that directly affect the quality of the navigation signal.Therefore,on the one hand,people began to study monitoring methods and building theoretical models,which can effectively reflect the changes of these parameters of the navigation signal,such as the signal-to-noise ratio,ionospheric delay,and multipath error.On the other hand,for the intentional or unintentional interference signals(such as spurious,harmonics and electromagnetic interference)existing in the signal,the corresponding interference detection algorithm such as energy detection methods and time-frequency feature extraction methods is studied.In this paper,a program which is developed based on MATLAB can easily,quickly and accurately implement the analysis and quality check of data in different formats such as Rinex result data,NMEA format data and SP3 format data.Through processing signal to noise ratio,ionospheric delay multipath error data,and displaying the data in the form of a picture,which can provide an intuitive visual judgment and provide an effective monitoring method.The interference that widely exists in the signal of the navigation receiver and the method of interference detection are explored.And take the common linear frequency modulation signal(LFM)interference as an example to verify the effect of energy detection under different thresholds on MATLAB.At the same time,the time-frequency analysis method short-time Fourier transform(STFT),Wigner-Ville distribution(WVD)and Wigner-Hough transform(WHT)methods are used to detect LFM interference in the navigation signal.The results show that the WHT method can effectively detect LFM interference,and it is better than the WVD method in performance.performance.