Research On Target Localization Method Of Distributed Multistatic Radar

Target positioning technology is one of the key technologies in modern radar.With the continuous development of science and technology,weapons and equipment among countries are changing with each passing day.When a war breaks out,it is no longer a contest of manpower but a confrontation of equipment.Radar is an indispensable equipment in military warfare.Therefore,improving the target positioning accuracy of the radar system has important military value.The distributed multistatic radar system consists of multiple transmitting stations,multiple receiving stations and a joint data processing center.Multi-station cooperation of distributed multistatic radar system can observe the target from different angles,which has great advantages in improving the accuracy of target positioning.This paper studies the positioning methods of distributed multistatic radar systems in two situations.One is a distributed multistatic line-of-sight radar that locates moving targets in the air,and the other is a distributed multistatic skywave over-the-horizon radar that locates sea-surface targets beyond the horizon.The positioning algorithms with higher positioning accuracy is proposed,which aim at the target positioning technology in the distributed multistatic line-of-sight radar system,The research work of the thesis is as follows:(1)The positioning principle of the distributed multistatic radar system is described,the composition structure and positioning model of the multistatic radar system are analyzed,and the corresponding mathematical model is established according to the positioning model.The two-step weighted least squares(2WLS)method based on the measurement data of Bistatic Range(BR),Time Difference of Arrive(TDOA)and Doppler Shift(DS)is studied,which can jointly estimate the position and speed of the air-moving target.The proposed algorithm not only improves the positioning accuracy,but also estimates the velocity of the moving target,this is important for distinguishing the type of airplane.(2)Based on the research of 2WLS method,the fixed Step Steepest-Ascent hillclimbing based on two-step weighted least squares(SAHC-2WLS)method is proposed.This algorithm is based on BR,TDOA and DS measurement data to estimate the position and velocity of the air-moving target.The proposed algorithm further improves the estimation accuracy of moving target's position and velocity.(3)On the basis of the SAHC algorithm and considering the influence of the search step size on the positioning accuracy,a variable steepest-ascent hill-climbing algorithm based on two-step weighted least squares(VSAHC-2WLS)method is proposed.This algorithm is based on BR,TDOA and DS measurement data to estimate the position and velocity of the air-moving target.This algorithm optimizes the search step length based on the SAHC algorithm.In simple terms,the fixed step search is optimized to the variable step search.The simulation results also prove that the estimation accuracy of the VSAHC is better than that of the SAHC.VSAHC-2WLS method achieved accurate positioning and speed estimation of the air-moving target.The research on target positioning of distributed multistatic sky-wave over-thehorizon radar is equally important,and target positioning is the basis of long-range early warning for sky-wave over-the-horizon radar.Improving the target positioning accuracy of sky-wave over-the-horizon radar has a positive effect on safeguarding homeland security.When the target is in a position beyond the line-of-sight,the signal model is more complicated and the positioning research is more challenging.Therefore,the method of locating the sea surface target of the distributed multistatic sky-wave over-the-horizon radar is studied.The research work is as follows:(4)First,the ionosphere,which is the propagation medium of sky wave signals,is introduced briefly,then the signal propagation model of distributed multistatic skywave over-the-horizon radar is established,and the positioning equation under this model is deduced.A single target localization algorithm based on the distributed multistatic sky wave over-the-horizon radar signal model is proposed,and the steepestascent hill-climbing algorithm based on the weighted least squares(SAHC-WLS)method is proposed.The performance of the algorithm is simulated and analyzed according to the set site coordinates.The result proves that the positioning accuracy of the proposed algorithm is significantly better than that of the WLS algorithm when locating sea-surface targets beyond the horizon.SAHC-WLS realizes the single target localization on the sea surface beyond the visual range.(5)The problem of multi-target positioning on the sea surface beyond the horizon in the distributed multistatic sky-wave over-the-horizon radar is studied,a signal propagation model of multi-target is established,and the mathematical equations of multi-target positioning and Doppler frequency shift are deduced.A positioning algorithm of multi-target is proposed.The proposed positioning algorithm of multitarget is mainly divided into four steps.First,the position of multiple targets is roughly estimated by the site configuration of one transmitter and multiple receivers.Second,according to the estimated target position,the observed and inverted data in the multiple transmitters and receivers configuration is classified.Third,the proposed SAHC algorithm is used to optimize the position.Then,according to the Doppler shift equation and the observed Doppler shift parameters,the speed of targets is calculated by using the LS method.Finally,according to the Bowring formula and the coordinate conversion formula,the position and speed coordinates in the rectangular coordinate system are converted to the geodetic coordinate system.The proposed algorithm is simulated and the results show that the proposed algorithm realizes the positioning of multiple targets on the sea surface beyond the horizon,and it realizes the estimation of the velocity and orientation of multiple targets.