Research On Moving Target Parameter Estimation And Imaging With Distributed Space-borne SAR

Distributed space-borne SAR has been widely researched in recent years since it can meet the needs of imaging and investigation for modern society. In the research of spaceborne SAR moving target parameter estimation, the main research object is a target moving on two directions, which are azimuth and range. However, in actual situation, the motion on vertical direction is too obvious to be ignored. The main works of this paper is to study on the parameter estimation problem of a target moving on three directions, which are azimuth, range and vertical.The research background of this paper is distributed space borne SAR. Firstly, this paper introduces the echo model of three dimension accelerated moving target. Secondly, this paper introduces the polynomial phase signal parameter estimation method based on cubic phase function. Then the method of cubic phase function is used to estimate each order phase coefficient of the echo model, the components of velocities and accelerations of the moving target are solved by the phase coefficients estimated. Finally, the parameter estimation results of the moving target are put into use to compensate the phase error during radar imaging, the aim of the compensation is to correct the defocusing and azimuth position deviation.Compared to a two-dimension uniform motion target, the oblique distance equation of a three-dimension accelerated moving target becomes more complicated, the phase coefficients estimated by a second-order Taylor expansion model are not precise enough to estimate parameters of the moving target. In order to estimate phase coefficients more precisely, a third-order Taylor expansion model is developed, by which the parameters of the moving target can be more precise. In this paper, a third-order Taylor expansion model is given and the polynomial phase signal parameter estimation method based on cubic phase function is used to estimate order phase coefficient, the parameters of the moving target are estimated preciously based on phase coefficients of several space-borne radars.The effect of moving target on the imaging results are mainly embodied in the defocus and position deviation, these two effects are analyzed properly and the correcting method with the estimated parameters of moving target is given in this paper, which are based on the Doppler rate compensation and Doppler center frequency corrected. The defocusing and azimuth position deviation of moving target can be corrected by these methods in the image.