Study of ISAR Imaging at SEA

Abstract: Inverse Synthetic Aperture Radar (ISAR) can provide high-resolution information of the ships through all the day, all-weather, and long-distance, monitor, track and identificate accuratelly in real-time for ship targets at sea, and provide support for human activities and navigation, when necessary, it could respond to risk objectives at sea. Therefore, ISAR imaging at sea is essential.The aim of research is processing the real ISAR data to obtain useful ISAR images, based on research and development of ISAR imaging technique, the first, we use theoretical model to simulation and analysis, and combine with the real raw data of co-operation targets, both from both theoretical and practical to discuss the impact of rotation for ISAR imaging, and also gain ship imaging characteristics statistically. According to the characteristics of ship rotation imaging, ship optimal imaging algorithm is proposed for a three-pronged process, 1) motion compensation; 2) optimal imaging interval selection; 3) imaging algorithm. The finally, using optimal imaging algorithm processes the real ship targets data.First of all, we construct the ship rotation scatter model, and process rotation imaging simulation, and then based on the theoretical analysis, we make clear for the concepts of imaging plane, the effective rotation vector imaging and other factors ,also we deepen the understanding of imaging; and then by the analysis of real ship targets data, we discuss the possibility of estimating sea conditions from the echo wave at sea, those all provide a basis to select the optimal imaging method.Optimal ship ISAR imaging is proposed in this paper, the process includes 1) motion compensation methods for multi-scatter ship model and rotation model– globle range alignment and multi-scatter auto-focus, 2) for the ship rotaion – optimal imaging interval selection is proposed based rotation vector estimation; 3) for the changing of the IPP and effective rotation vector– a general high order time-frequency analysis method is proposed for range instantaneous doppler imaging.In conclusion, measured data has been processed using the optimal ship ISAR imaging method, we has obtained identifiable ship targets ISAR images, the result has verified the validity of methods, we achieve the desired images for our research…
Key words: ship imaging; time-frequency analysis; rotation vector; instaneous imaging; rotation estimation