| Ship imaging is an integral part of inverse synthetic aperture radar(ISAR)imaging.In recent years,ISAR imaging is developing along the trends of dual/multi-static imaging,ultra-wideband wide-angle imaging,and sparse imaging.Multistatic ISAR can improve image resolution and obtain richer features of targets through data fusion.When the ship target is sailing on the sea surface,it will be subjected to periodic three-dimensional swings under the action of waves.This complex movement will cause the effective rotation vector of the ship to be time-varying,which brings great difficulties to imaging.This thesis aims to study how to get high-quality ship images.The main research contents of this thesis are as follows:1)Starting from the ship ISAR imaging model,the three-dimensional oscillation form of the ship was analyzed,the ship echo model under the dual-base imaging model was derived,and the ship imaging resolution was analyzed according to the echo characteristics.Motion compensation methods in ISAR imaging are introduced.Finally,simulation experiments and analysis are given.2)Aiming at the problem that ships have time-varying effective rotation vectors under the action of sea waves,an optimal imaging time selection method based on Doppler broadening is studied,and then the optimal imaging accumulation time is obtained by searching based on image contrast guidelines,and given Simulation experiments and analysis are given.Aiming at the problem of low ship imaging resolution in low sea conditions,a method for improving ship imaging resolution using multistatic ISAR is investigated,and the effectiveness of the method is verified by using a simple scattering point model and a Stereolithography(STL)model.Finally,considering the line-of-sight occlusion problem in actual imaging,a multi-base ISAR solution is given,and simulation experiments and analysis are given.3)Aiming at the discontinuity of adjacent equivalent radar observations in multistatic ISAR,the problem of multi-view imaging based on compressed sensing is studied.A comparison of several compressive sensing algorithms is given.The multistatic ISAR imaging method based on the orthogonal matching pursuit algorithm is introduced.Firstly,the echo data from multiple views are processed,and finally the multistatic ISAR imaging result is obtained based on the orthogonal matching pursuit algorithm.The simulation experiments of simple scatter point model and STL model are given to verify the validity of the method. |
