Research On Key Technologies Of Doppler Positioning On TDOA Satellite

The research of positioning problem is oriented to improve the positioning accuracy,and how to reduce the positioning error and locate the target source more accurately becomes the goal of this paper.In this article,we focus on the satellite-based passive positioning technology using Time Difference of Arrival(TDOA)as the positioning parameter,and investigate three aspects of the positioning equation solution method,time delay estimation method,and positioning method that affect the positioning accuracy,as follows.(1)Positioning equation solving method.In this paper,we study the analytical algorithm,Chan algorithm and Newton algorithm in the three-satellite time difference positioning solution method.The simulation results show that the variation curves of root mean square error with TDOA measurement accuracy of the above positioning algorithms can approach the lower limit of CRLB.(2)Time delay estimation methods.For the problem that the generalized mutual correlation algorithms based on different weighting functions require prior knowledge of the a priori statistical information of the signal and noise,and such information is difficult to obtain,an adaptive time difference estimation algorithm based on the minimum mean square error criterion is studied.The simulation results show that the algorithm can accurately estimate the time difference value in the case of different signal-to-noise ratio differences.(3)High and low orbit three-satellite time difference positioning method.To address the problem of poor positioning accuracy in the traditional three-satellite time-difference positioning research,a method of time-difference positioning with three-satellite constellations of different orbital altitudes is proposed.The method combines the advantages of large observation volume introduced by loworbit satellites and wide coverage by high-orbit satellites,and makes more reasonable and efficient use of existing satellite resources,so that satellites at different orbital altitudes can provide large distance differences under the premise of co-viewing.The simulation results show that the orbital altitude of three satellites has a great influence on the positioning accuracy,and the positioning accuracy of the proposed method is significantly better than the traditional three-satellite time difference positioning method.(4)Different orbit time-sharing single-satellite time difference positioning method.The multisatellite positioning method is restricted by certain conditions,which requires multiple satellites to be visible at the same time for the target source and the gateway station,and these satellites must be matched.In an environment where the user terminal is severely obscured,the line of sight is limited,and only a single satellite is visible at a moment,the multi-satellite positioning method will not be applied.Unlike the traditional single-satellite time-difference positioning method in the same orbit,it uses three satellites flying into the visual area of the positioning target at different moments for positioning.Simulation results show that the positioning performance of this positioning method is better than that of the same-orbit single-satellite time-difference positioning method.