Research On MEO Dual-satellite TDOA/FDOA Emitter Location Technology

In the field of satellite positioning technology,the precise localization of radiation sources has been an ongoing subject of research.This includes active electromagnetic wave radiation signals,passive cooperative signals,non-cooperative signals,and interferences.Especially in aviation accidents,maritime search and rescue,satellite communication interference and other fields.This paper focuses on utilizing Medium Earth Orbit(MEO)satellites to enhance positioning accuracy by emphasizing the time difference of arrival(TDOA)and Frequency Difference of Arrival(FDOA)in dual-satellite positioning.The research primarily revolves around three directions: developing positioning calculation methods,determining the necessary MEO satellite position and velocity parameters,and devising TDOA/FDOA parameter estimation algorithms.The goal is to achieve accurate emitter localization by using MEO dual-satellite TDOA/FDOA techniques,followed by the design,testing,and analysis of relevant software.The specific research content is as follows:First,we introduce the principle of dual-satellite time-frequency difference positioning,establish the positioning model,and deduce the TDOA/FDOA equations.These equations,along with the Earth equation,forms a group of positioning equations.We analyze the structure of the dual-satellite system and study three positioning calculation methods: Newton’s iterative method,algebraic analysis method,and particle swarm algorithm.By simulating results and analyzing performance,we assess the practicality of these three methods and provide a theoretical foundation for subsequent software design.Second,based on the analysis of the acquisition method for real-time satellite position and velocity parameters required by time-frequency difference positioning equations,we introduce the U-blox module and the relevant protocol.We verify our approach using the Beidou MEO satellite,acquiring ephemeris from its navigation message and calculating satellite parameters.By simulating the satellite trajectory based on the orbital parameters,we obtain real-time satellite position and velocity.A comparison between the simulation scene and the measured calculation results demonstrates minimal error,confirming the accuracy of the positioning solution’s satellite position and velocity parameters.Next,we discuss the time-frequency difference parameters necessary for the positioning equations and introduce common time-frequency difference estimation methods.We derive a timefrequency difference estimation method utilizing the cross ambiguity function.To address the issue of channel noise significantly impacting the accuracy of time-frequency difference estimation under bursty emitter signal’s low duty ratio characteristic,we propose an improved method using a windowed cross ambiguity function.This method enhances the accuracy of time-frequency difference estimation while reducing the computational load and shortening the estimation time.Finally,we designed MEO dual-satellite time-frequency difference positioning software based on search and rescue signals.The software composition and its modular design are introduced in detail.After the design is completed,each module is tested and combined with other software.In addition,an optimal scheme for MEO satellites is proposed to further improve the positioning accuracy in practical applications.