Research On Algorithm Of Passive Location And Measuring Velocity Based On TDOA And FDOA Of Three Satellites

Space-borne passive location system is of great application value in reconnaissance and surveillance,early warning detection and battlefield sensing because of its wide detection range,high position accuracy,and free from national and climatic influences.Among them,the signals from the three low orbit satellites intercepting the target radiation source are different due to the different arrival time of the radiation source and the Doppler-effect,leading to Time Difference of Arrival and Frequency Difference of arrival.Take advantage of the two time differences and two frequency differences between the three satellites,combined with information on the surface of the earth,the target velocity can be determined while determining the position of the target radiation source,either for a fixed target or without elevation information to obtain the three-dimensional position of the radiation source.In this paper,the processing flow of the TDOA system is on research.On the basis of analyzing the position principle of time difference and frequency difference,this thesis mainly studies the following points:1.The joint location algorithm of time difference.frequncy difference and time-frequnency for three satellites based on the spherical model and the WGS-84 earth model for fixed targets are studied.The improvement of the positioning of the three satellites TDOA systems is analyzed and compared.Through the control variable method,the joint positioning accuracy with different time error and different frequcency error is on research.2.In the absence of elevation a priori condition,a new method of three dimensional positioning of unknown elevation fixed radiation source using three-satellite time difference and frequency difference is proposed.In this thesis,the influence of slow motion on the accuracy of the dimensional positioning is analyzed.3.According to the movement law of most airborne radiation source targets,a new equal motion constraint condition is derived,and a new method of locating the target and measuring velocity of the moving radiation source is proposed,named Step-by-Step calculation.The effectiveness of the algorithm is verified by simulation.Through the theoretical analysis and simulation experiments,the influence of time difference measurement error,frequency error and elevation error on the position error and velocity error of the moving target radiation source are on research.