Research On Inverse Synthetic Aperture Radar Imaging Of Ship Targets

Inverse synthetic aperture radar(ISAR)is capable of high-resolution imaging of non-cooperative targets at all-weather and all-time,and plays a very important role in military and civilian fields.With the increasing demand for the development of naval equipment,many technologies which are related to radar imaging of ship targets have become the research hotspots again.This thesis mainly studies the related technologies of ISAR for ship imaging,especially discusses the methods of three-dimensional motion detection,the estimation of three dimensional rotation vector,the research of super-resolution imaging and the three-dimensional imaging method of interferometric inverse synthetic aperture radar(InISAR).First of all,the basic principle of ISAR and motion compensation is briefly introduced in this thesis.The research status of two-dimensional and three-dimensional imaging and ship imaging at home and abroad is analyzed,and the research background and main contents of the thesis are given.Then,this thesis studies the detection method of ship's three-dimensional motion.The principal component analysis(PCA)method is used to process radar data,and according to the number of selected principal component to detect three-dimensional rotation.The traditional motion compensation algorithm can still be applied by selecting the time interval with low degree of rotation to image.The experimental data proves the validity of the method.Then,the method of estimating the three-dimensional rotation vector of ship is studied.Because of the non-cooperative nature of the target,the estimation of rotation vector is a difficult point in ISAR technology.In this thesis,the singular value decomposition(SVD)method is used to estimate the slope of the center line of the ship,and the Doppler frequency of the scattering points of some special positions on the hull is changed to estimate the three-dimensional rotation vector of the ship.By selecting the appropriate time period,the vertical and horizontal rotational components are used to obtain the overlook and side view of the ship,respectively.The experimental data verifies the correctness of the algorithm.On the basis of the above research,the super-resolution imaging method is studied in this thesis.The ISAR imaging method of ship targets based on amplitude and phase estimation(APES)is presented.The adaptive filter is constructed to reconstruct the target scattering point according to the echo data.The simulated and real ISAR data imaging results verify the effectiveness of APES.Compared with the traditional range Doppler(RD)algorithm,the proposed algorithm is able to reconstruct the amplitudes of the scatterers with higher accuracy and lower sidelobe.The image contrast and signal and noise ratio of the image are also increased leading to good image quality.The three-dimensional imaging method of ship targets is studied in this thesis.First,the basic principle and the concrete implementation steps of the three-dimensional imaging method under normal model are introduced.Then,the three-dimensional imaging method under squint model is studied.In view of the longitudinal coordinate estimation error and image distortion introduced by the squint angle,squint iterative method and distortion correction method are given.Finally,the simulation experiments verify the effectiveness of the three-dimensional imaging in these two cases.At the end,the work of the thesis is concluded and the problems that need to be further studied and solved are pointed out.