Research On Key Technologies Of Maneuvering Target ISAR Imaging

Inverse synthetic aperture radar(ISAR),which can implement moving targets imaging in space,air and sea under the conditions of all-time and all-weather,has a significant practical value on both national security and national economy.However,there are still some problems in the imaging of maneuvering target.Under the maneuvering state,high-order phase terms which caused by the acceleration and even the jerk still exist in the receive data after motion compensation.The high-order phase terms will result in the defocus in azimuth profiles and reduce the quality of the reconstructed two-dimensional image.Moreover,radar echo will be affected by the radial velocity and acceleration of the maneuvering target in the stepped frequency system.The reconstructed one-dimensional range profile will shift and defocus.To solve the above problems,this thesis will make researches on ISAR imaging and one-dimensional range profile reconstructing of the maneuvering target.First of all,the basic principle of ISAR imaging is introduced,including the ISAR turntable imaging model and the linear frequency modulation signal.Also,the methods of the echo pulse compression and motion compensation are summarized as the basic technique of radar imaging.In addition,the RD imaging algorithm of an aircraft target is simulated,which lays a theoretical foundation for the subsequent ISAR imaging of maneuvering target.Secondly,the Cubic Phase Signals(CPS)model of the cross-range receive data is established after analyzing the characteristics of strong maneuvering target echo in detail.Because both of the chirp rate and quadratic chirp rate of CPSs defocus the image in azimuth,the phase difference-chirp fourier transform algorithm is presented in the thesis to solve the problem.With the presented method,all parameters of CPSs can be estimated to reconstruct the echo signal.Then,RD algorithm can be used to obtain a high resolution ISAR image.The simulations of the new method are experimented with MATLAB,and the preferable imaging can be obtained.Thirdly,one-dimensional range imaging of stepped frequency pulse echo signal of maneuvering target is studied.The Integrated cubic phase function(ICPF)algorithm is brought out on the basis of analyzing the effect of the radial velocity and acceleration that maneuver motion caused on the range profile.With the new method,the target motion parameters can be accurately estimated,and the motion phase terms can be compensated by the Dechirp technology.After performing the inverse fast fourier transform,the high resolution range profile will be obtained.Also,the high resolution imaging of stepped frequency pulse signal of maneuvering target is simulated,and the validity of the method is verified.Finally,the thesis summarizes the whole work and prospects for the further research.