Research On The Key Technologies Of Precise Point Positing In Ground-based Navigation System

Satellite navigation signals are very weak,vulnerable to interference and deception,and easily blocked in urban canyon,indoor and other complex environment,which can not guarantee the availability,continuity and reliability of positioning service.The ground-based navigation system can provide continuous and reliable positioning service in the region,which can provide support for the comprehensive Positioning,Navigation,and Timing architecture with Bei Dou satellite navigation system as the core.Focusing on the problem of precise point positioning in ground-based navigation,this paper studies four key technical problems,including precise point positioning model and parameter estimation method,precise measuring carrier phase technology,maintenance of ambiguity integer characteristic technology,and precise point positioning technology based on integer ambiguity resolution.Aiming at the problem of precise single point positioning model and parameter estimation method,the observation model of precise single point positioning of ground-based navigation system is established;The related errors in precise point positioning are sorted out.The error analysis shows that clock difference and uncalibrated phase delay difference between the stations are the reasons that single-differenced ambiguity does not have the ambiguity integer characteristic,and that carrier frequency synchronization between stations is the basis of precise point positioning of ground-based navigation system.A OTF-MAFA(On The Fly-Modified Ambiguity Function Approach)method based on coordinate domain search is proposed,which lays a foundation for the subsequent design of integer ambiguity resolution method.Theoretical analysis and experiment results show that the OTF-MAFA method has the same ambiguity success rate as the LAMBDA(Least-squares AMBiguity Decorrelation Adjustment)method.In order to solve the problem of precise measurement of carrier phase,the measurement error of carrier phase is analyzed,the formula of thermal noise jitter of the PLL tracking the pulsed navigation signal is derived,and the measurement stochastic model based on the carrier-to-noise ratio is established.For reducing the probability of the cycle slip,a multi-pulse coherent integral phase locked loop(MPCI-PLL)is proposed,and the equivalent noise bandwidth formula of digital PLL is derived.Experiment results show that the cycle slip threshold of MPCI-PLL is 3 dB lower than that of NSM-PLL.In addition,the error analysis of the Doppler measurement is performed,and the thermal noise jitter formula of is derived,which lays the foundation for the subsequent performance analysis of Doppler integration cycle slip detection.Aiming at the maintenance of ambiguity integer characteristic,the influence of ambiguity integer characteristic on precise point positioning is analyzed,and the initialization time and positioning accuracy of integer solution and float solution are compared.In order to solve the drift problem of single-differene ambiguity caused by frequency difference of clock oscillators between stations,the carrier frequency synchronization between stations based the phase-locked loop is studied;Based on the equivalence of Kalman filter and optimal phase locked loop system,the optimal loop bandwidth formula of slave synchronization loop is derived.In this paper,a new method for measuring fractional cycle bias,which is based on two-way measurement between stations,is proposed to recover the integer characteristic of single difference ambiguity between stations.The influence of hardware delay of the base stations and tropospheric delay on the stability of fractional cycle bias is analyzed.The change of hardware delay difference between stations due to temperature fluctuation is explored experimentally.The estimation formula of tropospheric delay variation is derived.Aiming at the problem of precise single point positioning based on integer ambiguity resolution,the success rate of the single-epoch ambiguity resolution is analyzed,which shows the necessity of OTF ambiguity resolution with multi-epoch observation.About the cycle slip detection problem in the multi-epoch ambiguity resolution,the performance of Doppler integration method is analyzed,and the cycle slip detection method based on phase locked indicator is studied.To shorten the initialization time of precise point positioning,an ambiguity resolution method based on hybrid domain search is proposed,which has the advantage of not needing cycle slip repairing.Kinematic positioning experiments show that,compared with the LAMBDA method,the time to first fix of ambiguity resolution method based on hybrid domain search is reduced by 20.39% when cycle slips occur in a single station.Finally,the research content is summarized,and the following research plan is prospected.The research results of this thesis can provide reference for the establishment of ground-based navigation system and the reaserch of the precise point positioning technology.