| Circular Synthetic Aperture Radar(CSAR)is a new type of remote sensing imaging system with 3D reconstruction capability.The CSAR focusing image quality is highly dependent on the elevation information of target scene,and the focal quality of image reconstructed from SAR data is usually degraded as a result of the uncompensated motion error with non-ideal flight path.The defocus is no longer exist only along the azimuth dimension,and hence motion compensation become difficult.This paper,first study the method of extracting the target height information in the CSAR model;Then after using the Non-uniform Fourier Transformation(NUFFT)to realize the CSAR echo imaging,motion compensation under non-ideal track is realized.The main contents are listed below:1.The scene DEM extraction method based on CSAR model is researched,which includes the analysis of phase error of the reconstructed image from both full-aperture and sub-aperture imaging system of CSAR under height error condition,the introduction of extracting the scene DEM in CSAR Model based on the study of the relationship between the target positioning deviation and the height error of the sub-aperture,and the verification of the effectiveness of the algorithm by programming simulation.2.The CSAR imaging and motion compensation algorithm based on Non-uniform Fourier Transform(NUFFT)is researched.Since in the traditional polar format algorithm the interpolation will bring error and low data utilization rate problem,a CSAR imaging algorithm based on NUFFT is proposed in this paper to improve the resolution of the CSAR imagery.Then,the motion error model of the CSAR is analyzed,the kinematic error is compensated for each sub-aperture image by the phase gradient autofocus algorithm(PGA)based on NUFFT.At last,a full aperture focused-image without motion error can be obtained by the fusion of the compensated sub-aperture images.The feasibility of the algorithm is verified by programming simulation. |
PDF Full Text Request