The Hybrid SAR/ISAR Imaging Of Sea-surface Target By Airborne Radar

Radar imaging technology mainly includes synthetic aperture radar(SAR)imaging technology and inverse synthetic aperture radar(ISAR)imaging technology.Highresolution images of targets can be obtained by both of them in all-time and all-weather conditions.SAR mainly uses the movement of the radar platform to obtain the images of the static scenes on the ground and ISAR mainly uses the movement of the targets such as aircraft and ships to obtain the images of targets themselves.With the increase of demand,more and more attention has been paid to the imaging mode that uses aerial moving radar platforms to obtain the images of moving targets on the ground or sea surface,which is also called hybrid SAR/ISAR imaging mode.This mode can not only obtain high resolution images of the background area,but also obtain the images and position of the moving targets such as ships in the background area,merge the image of moving targets and background area to provide complete situational awareness information of the target area.Due to the coupling movement between the radar platform and targets,and the complex unknown maneuver of the sea-surface targets,performing hybrid SAR/ISAR imaging of sea-surface targets by airborne radar will face problems of high order migration through resolution cell(MTRC)and space-variant of echo.And it is difficult to merge the image of moving targets and background area.This thesis focuses on the problems mentioned above,and studies the hybrid SAR/ISAR imaging method for sea-surface targets by airborne radar based on back projection(BP)algorithm.The main content is:1.The echo model of hybrid SAR/ISAR imaging for sea-surface targets by airborne radar is studied and the echo rule is analyzed.The imaging process of hybrid SAR/ISAR imaging for sea-surface targets by airborne radar is deduced based on the imaging principle of SAR and ISAR.2.Methods to detect the moving ships based on image entropy are studied,as well as methods to separate and extract the echo of them,which provides the foundation for the refocusing imaging of the moving ships targets.3.An BP-ISAR imaging method based on particle swarm optimization(PSO)algorithm is proposed,which solves the problems of high order MTRC and space-variant of echo in traditional ISAR imaging methods.The clear imaging of moving ships targets is obtained,and the images of targets and background are effectively merged.4.An BP-ISAR imaging method for multi-target based on multimodal PSO algorithm is proposed,which can effectively solve the application problems in multitarget cases.The above methods are verified by theoretical analysis and simulation experiments.The results show that they can effectively solve the problems when performing the hybrid SAR/ISAR imaging of sea-surface targets by airborne radar.