Research On Fast Imaging Algorithm Of Ground-Based Circular Synthetic Aperture Rada

Ground-based arc synthetic aperture radar(GB-ArcSAR)is a new type of Groundbased synthetic aperture radar(GB-SAR).Unlike the linear trajectory of the Synthetic aperture radar(SAR)antenna,the antenna of GB-ArcSAR moves in a uniform circular motion with the spiral arm.Back projection(BP)imaging algorithm is widely used in SAR imaging due to its advantages of high imaging accuracy and wide application range.However,it needs to be backprojected on each point in the target scene,which makes it difficult to quickly monitor the target scene in real time due to the large amount of computation.Due to the special antenna motion trajectory of GB-ArcSAR,the slant course between the antenna and the point target in the imaging scene is more complicated than that of linear SAR,so a series of fast imaging algorithms in frequency domain designed based on linear SAR are no longer applicable.Therefore,it is necessary to design a fast imaging algorithm in frequency domain suitable for GB-ArcSAR based on the special antenna trajectory.BP imaging algorithm carries out oblique projection on point targets on fixed imaging reference plane to complete two-dimensional imaging.Due to the special antenna motion trajectory of GB-ArcSAR,if point targets in the target scene contain elevation information,the oblique distance history of the antenna,point targets and imaging projection points will be inconsistent,resulting in imaging errors and reducing the SAR imaging quality.This paper conducts a systematic and in-depth study on the above problems,designs a series of fast imaging algorithms applicable to GB-ArcSAR,and improves the imaging speed of GB-ArcSAR.Specific work is as follows:(1)A fast BP imaging algorithm suitable for GB-ArcSAR is proposedIn order to improve the imaging speed of GB-ArcSAR,a fast BP imaging algorithm suitable for GB-ArcSAR was proposed.Firstly,the geometric model of GB-ArcSAR is analyzed,and the slant course of GB-ArcSAR echo signal is deduced.Then,the computational efficiency is improved by reducing the redundant calculation of BP imaging algorithm.(2)A fast imaging algorithm based on Shengjin solution is proposed for GB-ArcSARIn order to improve the imaging speed of GB-ArcSAR,a fast imaging algorithm based on Shengjin solution was proposed for GB-ArcSAR.Firstly,the slant course of the echo signal is expanded to Taylor fourth order,and the accurate two-dimensional spectrum of GB-ArcSAR echo signal is derived by using Shengjin equation method combined with the stationary phase principle,and an accurate two-dimensional matching filter is designed.(3)An improved fast imaging algorithm based on series inversion is proposed for GBArcSARIn order to improve the imaging speed of GB-ArcSAR,a fast imaging algorithm based on series inversion is proposed for GB-ArcSAR.Since the two-dimensional spectrum of GBArcSAR echo signal is difficult to be derived by traditional mathematical methods,the algorithm deduces the accurate two-dimensional spectrum of GB-ArcSAR echo signal by inversion of the phasing point expansion coefficient,and designs the corresponding twodimensional frequency domain matching filter.(4)A GB-ArcSAR image fusion algorithm based on digital elevation model(DEM)data is proposedAiming at the problem that the imaging quality of GB-ArcSAR will be degraded when BP algorithm is used to image point targets containing elevation information,a GB-ArcSAR image fusion algorithm based on DEM data is proposed.By introducing DEM data to correct skew projection error,SAR imaging quality is improved.