Methods And Performance Analysis For Unknown Emitter Geolocation Via Multilayer Ionosphere Reflection

Short-wave geolocation is of great value in a number of civilian and military fields,such as navigation,aviation,maritime search and rescue and support,radio spectrum monitoring and management,etc..We mainly consider the problem of the method and performance for unknown emitter localization under multi-layer ionosphere reflection in the paper.The main work of the paper is as follows: 1)Based on the ray analytic expression of the propagation path model under the existing multilayer quasi parabolic(MQP)ionosphere model,the unknown emitter geolocation using the time difference of arrival(TDOA)measurement of the multiple receivers is described as a highly nonlinear and non-convex optimization problem in the sense of maximum likehood,and an approximation approach based on the gradient descent method and Newton second-order iterative algorithm is proposed.At the same time,the Cramer-Rao bound(CRB)formula for position estimation is derived;2)Under the single layer quasi-parabolic(QP)ionosphere model,the effects of perturbation of single-parameter in QP model on the geolocation performance using TDOA measurement was studied by simulation;3)The joint maximum likelihood estimation and CRB calculation formula of ionosphere parameters and unknown emitter are studid and derived using TDOA measurements of multiple receivers when the single-layer QP ionosphere model parameters are unknown but there are multiple known emitters,and we perform Monte Carlo simulation.Monte Carlo simulation results show that: 1)When the ionosphere model parameters(single layer or double layer)are known,the geolocation errors are close to the corresponding CRB in the case of setting up three receivers and five receivers respectively.They perform the geolocation with high accuracy,and the more the number of receivers is,the better the positioning effect is;2)the geolocation performance under the perturbation of singleparameter in QP model within a given certain range is acceptable when the knowledge of single-layer ionosphere is not completely known;3)When the parameters of the single ionosphere model are unknown but there are multiple known emitters,in the two scec=narios that three receivers and five receivers are respectively deployed with three known emitters,the ionosphere parameters and geolocation errors are close to their corresponding CRB.They all have good positioning results,and the more the number of receivers is set,the better the positioning result is.