Study On Algorithm For Downward-Looking Synthetic Aperture Radar Three-Dimensional Imaging Based On Linear Array Antennas

As an active spaceflight,aviation remote sensing method,microwave imaging technology have the characteristics of all-day and all-weather work,and have extensive applications in environmental protection,disaster monitoring,ocean observation,resource exploration,military reconnaissance,etc.It has become one of the most important tools for resolution earth observation and global resource management.Three-dimensional synthetic aperture radar imaging(3D-SAR)is a new microwave imaging technique developed from the traditional two-dimensional SAR imaging.The 3D-SAR imaging technology based on array antenna is one of the important ways to realize three-dimensional high-resolution SAR imaging.Applying linear array to radar imaging field can realize two-dimensional and three-dimensional imaging,which expands the performance and application fields of the existing SAR systems.Therefore,it has become one of the research hotspots in SAR field.This article is based on the mastery of two-dimensional imaging technology such as RD algorithm,CS algorithm and BP algorithm,further research on 3D-SAR imaging technology.The existing array 3D-SAR imaging algorithm has been improved.The system models,resolutions and 3D imaging algorithms for 3D-SAR with monostatic,single-input and mutiple-output(SIMO)linear array antennas respectively are firstly investigated in this dissertation.The proposed theoretical model and imaging method were verified by simulation experiments.The main research content of this paper is as follows:1.The imaging principle and resolution characteristics of downward-looking 3DSAR imaging radar are introduced.The signal model of downward-looking 3D-SAR is studied.The downward-looking 3D-SAR three-dimensional resolution characteristics are deduced,and the principle of antenna element spacing is given.On this basis,the geometric model and echo signal model of downward-looking 3D-SAR of SIMO array antenna are studied,and three-dimensional resolution characteristics of downwardlooking 3D-SAR are deduced.2.According to the characteristics of downward-looking 3D-SAR imaging,based on the conventional 2D-SAR Range Doppler imaging algorithm,an extended threedimensional range Doppler imaging algorithm is proposed to construct a threedimensional range-Doppler domain reference function.The algorithm adopts two-dimensional polynomial interpolation method,which effectively reduces the complexity of three-dimensional interpolation in existing three-dimensional imaging.Finally,simulation experiments verify the correctness and effectiveness of the imaging algorithm.3.Aiming at the problem of cross-heading non-uniform sampling in downwardlooking 3D-SAR imaging,a non-uniformly interpolated 3D beamforming algorithm is studied,and the description model of the beamforming principle in the track direction and cross-track direction is established.Through the weighted summation of the received signals,a beam in a specific direction is formed so that the beam main lobe is directed at the target and the zero lobe is aligned with the interference signal,thereby improving the imaging accuracy.Simulation experiments verify the correctness and effectiveness of the imaging algorithm.