Research On Vector Tracking Loop Algorithm Of GNSS Receiver

The wide application of Beidou Navigation Satellite System(BDS)in various fields promotes the constantly improving requirements of navigation receiver positioning accuracy and reliability.Currently,the vast majority of navigation receivers are still based on single frequency positioning mode with low-cost and high-accuracy,which cannot completely solve the application limitations caused by landform and environmental factors.Hence,to solve the problem of receiver limited application in the scene of multipath effect and signal occlusion,vector tracking technology is widely studied owing to its high precision and convenient structure design process.In this thesis,the research of vector tracking technology includes two parts: tracking loop design and positioning algorithm improvement.Firstly,aiming at the problems of filter dimension and update rate of vector tracking loop algorithm in Global Navigation Satellite System(GNSS)receiver,the tracking structure with Delayed Lock Loop(DLL)and Phase Lock Loop(PLL)is implemented,the state model and measurement model based on nonlinear navigation filter algorithm are given,and the coupling structure of positioning calculation unit and vector tracking unit is designed.Then,the effectiveness and robustness of the proposed vector tracking loop are verified by experiments in open outdoor and multipath scenarios,respectively.In addition,in order to solve the problem of positioning deviation caused by ionospheric delay in the single-frequency positioning,an Adaptive Window Smoothing Constant(AWSC)hatch filter is proposed.This algorithm determines the appropriate smoothing constant according to the current satellite signal carrier-to-noise ratio,and carries out the pseudorange smoothing process in each satellite channel,which can effectively suppress the positioning error caused by ionospheric delay,and its performance is verified by simulation experiments.Compared with the traditional BDS single-frequency positioning,the experimental results show that the vector tracking algorithm based on AWSC hatch filter improves the positioning performance under the influence of multipath effect,ionospheric delay and other factors,which is of great significance to improve the navigation receiver positioning performance.On the basis of the above theoretical research,the processing platform of vector tracking receiver is built.The platform can meet the positioning requirements of navigation receiver n open outdoor and multipath scenarios,and realize the vector tracking loop algorithm and pseudorange smoothing algorithm.According to the BDS receiver requirements,it can be divided into data reading module,acquisition module,tracking module and positioning solution module with the functions of signal acquisition quality analysis,time-domain parallel code phase acquisition,tracking mode selection and pseudorange smoothing algorithm selection.Moreover,the platform can output the signal processing results of vector tracking receiver for further research,including positioning result under different algorithms,error data diagram,and the receiver estimated position.