Research On The Key Techniques Of Interferometric Inverse Synthetic Aperture Radar Imaging

Interferometric inverse synthetic aperture radar(InISAR) imaging is a recently developed three-dimensional(3-D) imaging method which combines interferometric technology with the inverse synthetic aperture radar.InISAR is able to carry out 3-D imaging of a far-field moving target under all-weather condition and any required time,so it has shown a wide range of prospects and practical value in the field of military and civilian applications.But at present,the realization of InISAR 3-D imaging method of complex moving targets are still facing many problems and need in-depth researching and improving.This dissertation has been launched to study and investigate the InISAR imaging methods of three typical moving targets,which are valuable for the practical application.First of all,the image registration problem of InISAR is studied.Image registration between interferometric antennas is a crucial step for InISAR 3-D image restoration.Based on the analysis of the image mismatch,two effective image registration methods which make use of the characteristics of different targets are proposed.The first method is that if the target contains only one isolated scatterer,we carry out single isolated scatterer phase-adjustment of each antenna independently to achieve image registration,which will synchronously consider the single isolated scatterer as focus center.The second one is that when there are no isolated scatters exist,after uniform radial-motion compensation,we construct compensatory phase and achieve image registration by estimating angle motion parameters of target scattering centers along two-dimensional baseline direction.Simulation results show that both methods can obtain accurate registration results.Secondly,the 3-D InISAR imaging method of high speed moving target is studied.The high radial velocity between radar and target will result in a range dispersion phenomenon which will defocuses ISAR image and seriously affect the accuracy of the interference restoration.Therefore,two effective high-resolution InISAR 3-D imaging methods for high speed moving target are proposed.One is based on the approach of velocity compensation,a precise velocity estimation method based on RWT is proposed and 3-D image can be achieved through the compensated echo.Unlike the upside approach of speed compensation,the second method is based on instantaneous range profile,which can eliminate the dispersion effects in the time-frequency slice and directly used for 3-D InISAR imaging.Simulation results show that the above-mentioned imaging methods can both achieve 3-D InISAR imaging of high-speed moving targets correctly.Thirdly,the 3-D InISAR imaging method of maneuvering targets is studied. Unlike the range dispersion caused by high speed,Target's maneuvering characteristic during imaging time will make the cross-range Doppler becoming multi-component LFM signals,by using traditional RD imaging method will cause the defocus of cross-range imaging.Under the idea of range- instantaneous Doppler(RID) imaging, a 3-D InISAR imaging method of maneuvering targets based on FRFT linear time-frequency transform is proposed firstly.Scatterers' cross-range separation can be achieved in the fractional domain and then a high-resolution 3-D image can be reconstructed.Aiming at the problem of the restrictions of bilinear time-frequency analysis method which can not retain the interferometric phase,we further proposed a 3-D InISAR imaging method based on joint cross-time-frequency distribution.This multi-antenna-based method not only can overcome the restrictions of the bilinear time-frequency transform,but also can achieve scatterers' cross-range reparation and phase interferometfic processing in one transform at the same time,which can directly used to reconstruct 3-D InISAR image.Simulation results show that both two proposed methods can effectively obtain the high-resolution 3-D InISAR image of maneuvering target.Finally,the 3-D InISAR imaging method of large size target is studied. High-resolution imaging of large size targets are not satisfied with the traditional ISAR micro-rotating approximation,the MTRC phenomenon of scatterers at the edge both seriously effect motion compensation and cross-range resolution which will decline the accuracy of InISAR imaging.A method of motion compensation which combines accumulation correlation with the curve fitting is proposed at first to increase the accuracy of motion compensation under MTRC condition.Then,the back-projection rotation angle estimation technique in the structure of multi-antenna InISAR imaging is proposed.This technique can obtain accurate estimation of the rotation angle taking the advantages of 3-D imaging,then combing with polar format algorithm,a clear 3-D InISAR image of large size target can be formed at last.