Study On Key Algorithms For Isar Imaging Of Targets With Complex Motion

Inverse Synthetic Aperture Radar(ISAR)has the advantages of all-weather,long-distance detection and high-resolution image acquisition of non-cooperative moving targets,and plays an important role in the military and civil fields.ISAR imaging technology is relatively mature for stationary moving targets.With the development of radar technology and the continuous expansion of observation targets,there are still many technical problems in ISAR imaging for complex moving targets with high maneuverability,precession,nutation and three-dimensional rotation.Therefore,the research on ISAR imaging processing technology for complex moving targets has important theoretical significance and application value.Based on the above background,this thesis studies several key technologies of ISAR imaging processing for complex moving targets.The main work contents are as follows:Chapter one is the introduction.The research background and significance of this thesis are described.The development of ISAR imaging theory and technology is systematically introduced.The imaging technology of complex moving targets is summarized and analyzed,and the detailed content arrangement of this thesis is introduced.The second chapter introduces the basic of ISAR imaging.This thesis summarizes the imaging model of ISAR turntable and imaging technology,including the classical methods of pulse compression and motion compensation.By simulating the echo of aircraft scattering point model and RD algorithm,it lays a foundation for the ISAR imaging of complex moving targets in the following paragraphs.The third chapter analyzes the influence of complex motion on ISAR imaging of targets.The kinematic geometric models of various complex motions were established,and the characteristics of the target's range and slow time echo signal were quantitatively analyzed.Taking the missile with precession and spin motion characteristics as an example,the instantaneous distance variation and Doppler frequency characteristics of the complex moving target were specifically studied.The simulation echo data is obtained based on the missile model,and the correctness of the above theoretical analysis is verified by analyzing the echo spectrum and micro-Doppler spectrum.The fourth chapter studies the ISAR imaging algorithm for complex moving targets combining the method of parameter estimation based on Fractional Fourier Transform(FRFT)and generalized second-order Keystone transform.Firstly,the echo characteristics of high-speed moving targets are analyzed.Combined with the fretting characteristics of complex moving targets,the parameter estimation method based on fractional Fourier transform and generalized second-order Keystone transform are applied to the traditional RD algorithm to get a new improved algorithm.The traditional RD algorithm and the new algorithm are used to contrast and analyze the missile simulation data.The simulation results show that the new algorithm can improve the focusing effect of the ISAR image.The fifth chapter studies the ISAR imaging time selection algorithm for complex moving targets.Two optimal imaging time selection algorithms are analyzed,namely,the optimal imaging time selection algorithm based on image contrast estimation and Doppler broadening estimation.By screening the simulation echo data,the optimal imaging time is obtained,and the target is approximately stationary in the selected imaging time,meeting the conditions of ISAR imaging with RD algorithm,which can effectively increase the robustness of imaging processing.Chapter six is the conclusion,which summarizes the work done in this thesis,and makes a prospect for the future research.