Research On 3D Imaging Technology Of High-speed Dive Forward Line-of-sight Array SA

Synthetic Aperture Radar(SAR)is a microwave remote sensing detector that obtains high resolution in the distance direction by emitting large time and wide bandwidth signals as well as using pulse compression techniques,high resolution in the azimuth direction by means of the synthetic aperture formed by the relative motion between the platform and the target,and high resolution across the heading by using the real aperture formed by the antenna array elements.Among them,the high-speed dive SAR forward-looking imaging system has become one of the research hotspots in the field of SAR imaging in recent years due to its ability to provide SAR images of the scene directly in front of the platform motion,which has important application potential in the fields of blind aircraft landing,geological exploration,reconnaissance and surveillance,precision guidance and so on.Based on the basic theoretical research of radar imaging,this paper establishes the geometric model of 3D SAR imaging scene and echo signal model of high-speed swooping forward-looking line array,carries out the research of 3D distance Doppler improvement algorithm,3D non-linear frequency modulation variable scale algorithm and 3D compression perception algorithm,and validates the proposed theoretical model and imaging method through simulation experiments.The main research areas of this paper are as follows:1.Based on the research of traditional RD and NLCS imaging algorithms,a threedimensional SAR geometry model and echo signal model of high-speed swooping forwardlooking line array are established,and a three-dimensional RD imaging algorithm is applicable to high-speed swooping forward-looking line array SAR is proposed.The three-dimensional frequency domain expression of the echo signal is derived by using the principle of stationary phase and the level decomposition method,and the three-dimensional decoupling function,the distance direction compression function,the azimuth direction compression function and the cross-track compression function are designed to obtain the three-dimensional image of the forward-looking target area.The feasibility,and correctness of the algorithm are verified by simulating a single point target and a 3×3×3 point target.2.Aiming at the problem that the special operating mode of high-speed swooping forwardlooking line-array 3D SAR leads to easy scattering and poor imaging quality of azimuth-edge point targets,a 3D NLCS algorithm applicable to high-speed swooping forward-looking linearray SAR is proposed.The results of the 3×3×3 point array target imaging verify the feasibility and correctness of the 3D NLCS algorithm.The imaging results of single point targets show that the 3D NLCS algorithm is able to obtain azimuthal images with better focusing performance than the 3D RD algorithm.3.Based on the above problems,a three-dimensional compression-aware imaging algorithm is proposed for high-speed diving forward-looking line array SAR,which requires a high cost for the erection of uniform antenna arrays and low cross-curve resolution due to the use of matched filtering.A sparse antenna array is designed using random sampling,a truncated singular value decomposition principle is used to reduce the number of samples,non-uniform sampling of the echo signal is achieved,and a compression-aware reconstruction algorithm is used to obtain the cross-curve compressed images.The results of the single-point and multipoint targets demonstrate that the TSVD-CS algorithm is able to achieve higher resolution and higher efficiency in cross-track imaging than matched filtering methods.