Research On Multi-channel Radar Forward-looking Imaging And Parameter Estimation

Radar imaging and target parameter estimation play an important role in many fields such as forward reconnaissance,guidance,and autonomous landing.However,the traditional monostatic synthetic aperture radar(SAR)and Doppler beam sharpening(DBS)techniques have blind area in forward-looking imaging.By distributing multiple channels in azimuth and pitch,the radar has the potential of high-resolution imaging and parameter estimation in the forward-looking area.But at the same time,multi-channel reception brings complex processing problems.The thesis focuses on the theory and method of multi-channel radar forward-looking imaging and target parameter estimation.Firstly,the echo model is established according to the spatial geometry model.Then the reason for the left-right ambiguity in forwardlooking image is analyzed,and the method to avoid it is studied.Last,a target height estimation method based on forward-looking configuration is researched.The main contents of this thesis are divided into three parts,which are as follows:1.According to the spatial geometry configuration of forward-looking multi-channel radar,the range history expression is derived and then the echo signal model is established.Based on the principle of equivalent velocity and equivalent phase center(EPC),the expressions of resolution are derived,and the influencing factors of azimuth resolution are analyzed emphatically.This thesis analyzes the cause of left-right ambiguity in traditional single transmitter and single receiver radar forward-looking imaging,and designs a method to avoid it in multi-channel forward-looking radar.2.The multi-channel interference configuration is constructed and the effect of stationary target height on its location in two-dimensional image is analyzed.The relationship between the interferometric phase and the target distance is deduced,the influence of the distance change on the interferometric phase is analyzed.Then a target height estimation method for the forward-looking configuration is proposed.In this method,the distance between the target and the platform is considered.The residual function between the measured interferometric phase and the phase model is constructed,and the problem is solved by the Gauss-Newton method.3.The echo model of moving target is built and the focus imaging of moving target is realized.Aiming at the problem that the traditional elevation inversion method cannot estimate the target height and vertical velocity simultaneously,the relationship between the interferometric phase and the target height and vertical velocity is deduced.Then a joint estimation method of the target height and vertical velocity based on the forwardlooking configuration is studied.Multiple interferometric measurements of the image are completed by overlapping subaperture method,and the interferometric phase is obtained.The residual function between the measured phase and phase model is constructed,and the optimization algorithm is used to solve the problem.The methods proposed in this thesis have been verified by MATLAB.Simulation results show that the proposed methods can achieve multi-channel radar forward-looking imaging and accurate estimation of target parameters.