ISAR Imaging Research Based On Time-domain Electromagnetic Scattering Algorithm

Radar imaging,as a kind of all-day,all-weather active remote observation means,has been widely used in military and civil fields.As a kind of imaging radar,inverse synthetic aperture radar(ISAR)can obtain not only the high-resolution imaging results of the target,but also the size and structure of the target by using the image calibration,interpretation and recognition.Characteristic information plays an important role in military and civil fields such as space situation awareness,air defense and missile defense,and civil aviation control.From the target time-domain(TD)electromagnetic(EM)scattering mechanism of the target,this thesis deeply studies the TD EM scattering characteristics of the target in a complex background.On this basis,the ISAR radar echo simulation,the one-dimensional range of the target,as well as ISAR imaging algorithms are carried out.The main content of this thesis is as follows:1.Based on physical optics,the basic principle of TD high-frequency scattering algorithm is introduced.Combined with TD system response analysis method,the closed expression of TDPO and TDSBR far-field EM scattering is given.The closed expression is derived based on Gordon formula,which is suitable for the TD scattering analysis of electrically large size targets and rough surfaces with arbitrary polygon division.Based on the principle of multithreading,TDPO and TDSBR scattering programs are accelerated in parallel,which effectively improves the computational efficiency of TD scattering.2.A target radar echo model based on the TD high-frequency EM scattering algorithm TDPO and TDSBR is proposed.With that,the data processing of the one dimensional range image of the target is introduced,and the one dimensional range image of the target above the rough surface is simulated.3.On the basis of the turntable model,an ISAR image generation algorithm based on TD scattering echoes is proposed.TDPO and TDSBR algorithms are used to generate the original echo data matrix.Then,the ISAR image with small bandwidth and angle is obtained by using the demodulation,pulse compression and azimuth compression of the echo data.In order to improve the quality of ISAR imaging,an image processing algorithm based on nonlinear mapping is proposed.By normalizing,denoising,interpolation and nonlinear mapping of ISAR image,the noise in ISAR image is effectively suppressed and the imaging quality of ISAR image is improved.4.The process of obtaining 3D geometric model of complex target and missile launch site respectively by using commercial geometric modeling software and fractal theory are given.On this basis,the TDSBR algorithm combined with the ISAR imaging principle in Chapter4 is used to simulate the complex target and missile launch site.