Research On 3D Imaging Algorithms Of Circular Scanning Ground-Based SAR Based On FFBP Algorithms

As a high-precision measurement technology,ground-based SAR has the advantages of all-weather,non-contact and flexible station setting.It can monitor the deformation situation and deformation trend of the scene in real time.Since its inception,it has become an important tool for earth observation.With the increasing application requirements,ground-based SAR systems of different systems have gradually emerged.In order to meet the needs of three-dimensional information acquisition and multi-angle observation,the circular scanning ground-based SAR came into being.Compared with linear ground-based SAR,the system has a larger observation range and a threedimensional resolution capability,which can effectively suppress the overlay phenomenon.In the imaging algorithm of circular scanning ground-based SAR,the back projection algorithm is widely used by scholars because of its high accuracy and unlimited radar trajectory.At present,the feasibility of circular scanning ground-based SAR back projection 3D imaging has been verified internationally,but the imaging efficiency is still difficult to meet the needs of actual use.Therefore,this paper proposes a 3D imaging algorithm for circular scanning ground-based SAR based on fast factored back projection,and studies the imaging model,imaging algorithm and imaging quality analysis of circular scanning ground-based SAR.The main research contents and results are as follows:(1)Aiming at the problem that the conventional imaging algorithm has low imaging efficiency and cannot meet the needs of continuous monitoring when the circular scanning ground-based SAR faces large scenes,a terrain-assisted 3D imaging method is proposed in this paper.By comparing the amplitudes of the target points,the effective points of each position in the scene are screened out,and the extracted effective points are constructed into a three-dimensional terrain surface,and back projected on the three-dimensional terrain surface to achieve three-dimensional imaging.This method reduces the dimension of the target point in the scene into a threedimensional surface,thereby reducing the amount of data in back projection and improving the imaging efficiency.Simulation experiments show that the target point distribution in the imaging results is consistent with the target point distribution in the actual data,the imaging quality is high,and the algorithm takes less time.(2)Aiming at the problem that the back projection algorithm needs to perform pixel-by-pulse projection,which leads to the slow imaging speed,this paper proposes a fast factorized back projection algorithm suitable for the circular scanning groundbased SAR.The algorithm needs to equally divide the full aperture into multiple subapertures,and image them separately under the sub-apertures.The baseband conversion is performed by multiplying the sub-image and the phase function to realize the spectrum shift,the sub-image is upsampled by zero-padding in the two-dimensional frequency domain,and the non-baseband restoration of the sub-image is realized by compensating the phase function,and finally the multiple sub-images are fused.for fullaperture high-resolution images.Simulation experiments show that the imaging accuracy of the algorithm is close to that of the back projection algorithm and the imaging speed is greatly improved.(3)The fast factored back projection algorithm is applied to terrain-assisted 3D imaging,and a circular scanning ground-based SAR 3D imaging algorithm based on fast factored back projection is formed.The imaging quality and imaging efficiency of the algorithm are verified by point target simulation,and compared with the point target simulation results of the back projection algorithm.The applicability of the algorithm is verified by 3D image data simulation,and the theoretical calculation amount of the algorithm is analyzed.