Research On Vector Tracking Technology For GPS/BDS Dual-mode Satellite Signals

As Beidou-3 satellites continue to be launched,dual-mode navigation receiver technology are becoming of scientific interest these years.The Vector Tracking loop(VTL)is well-known for its high stability.It can deal with signal loss conditions by improving the structure of the tracking loop during designing without introducing extra information.The GPS/BDS dualmode vector tracking algorithm is investigated in this thsis,thereinto the vector delay frequency locked loop(VDFLL)is designed and tested.The main contents of the thesis are as follows:First of all,the satellite signal structure of GPS/ BDS and processing of the dual-mode baseband signal is introduced and analyzed,and a fast cold start algorithm based on the satellite structure and probability statistics is proposed.The structure and characteristics of GPS and Beidou signal are introduced in this section.The signal structures of different frequency points of GPS and Beidou are described respectively.Then,the principles and methods of signal acquisition are analyzed.At the end of this section,a fast cold start algorithm based on the satellite structure and probability statistics is proposed,and it is verified by the experiment that the algorithm can improve the efficiency of cold start of receiver.Next,traditional scalar tracking loops and navigation calculation module are analyzed according to its principles.In signal tracking part,the thesis focuses on code loop and carrier loop.The differences among the different phase discriminators/frequency discriminators are analyzed.The theory of satellite orbit is analyzed.Thereinto the orbit parameters and calculation principles of Beidou GEO satellite are different from MEO/IGSO satellites and GPS satellites.Besides,Navigation calculation formulas from ICD documents are described.In this thsis,the common pseudo-range and Doppler frequency are used as the observation of Kalman filter.It is shown from the semi physical simulation of scalar tracking that the doppler frequency estimation has a large deviation in case of signal loss.Also,the location results drift away.Finally,GPS/BDS dual-mode vector tracking loop is designed and verified.The key technologies of dual-mode vector tracking loop are investigated in this section,mainly including the loop structure design,the comparison of Beidou GEO,IGSO and MEO orbit solutions and the calculation mode selection.The model of VDFLL tracking loop is established in this section,experiments under different circumstances are carried out to collect the navigation results of the vector tracking loop and the scalar tracking loop.The experimental data is analyzed and demonstrates the conclusion: the VDFLL can make a better use of the coupling of different signal channels.When signal lost or blocked,VDFLL performs better in positioning.The north position error is reduced by 15.0% and the east position error is reduced by 14.3%.Experimental results show that the GNSS vector tracking loop can more fully utilize each tracking channel's output residuals,make a better use of the inherent correlation among the visible satellites combined with the ephemeris data and improve the stability and recapture rate of satellite in case of signal loss.