Research On Inverse Synthetic Aperture Radar Imaging Of Ship Targets

Inverse synthetic aperture radar (ISAR) is a kind of high-resolution imaging radar, which is designed to address the imaging problems of the moving targets. It has great military and civil value. Since the motion of the ship is complicated, how to get the high-quality images of ship targets at sea has been the research focus in the field of ISAR at home and abroad. This thesis studies on how to achieve the high-resolution ISAR images of ship targets, based on the characteristics of ship imaging. This thesis mainly includes three aspects: utilizing ISAR technology to improve the quality of missile-borne synthetic aperture radar (SAR) imaging of ship targets, prediction of ISAR imaging plane of ship targets, and ISAR imaging of ship targets based on time-frequency analysis. In chapter 1, the research background, significance and developments of the ISAR are introduced firstly. Then, the principle of ISAR imaging and the technology of ISAR signal processing are presented. Lastly, the main contents of this article are outlined.In chapter 2, how to utilize ISAR technology to improve the quality of missile-borne SAR imaging of ship targets is described. According to the characteristics of ship imaging, selecting the effective methods of ISAR motion compensation for further processing after SAR imaging. Simulation results show that ISAR processing can effectively suppress the image defocusing caused by target motion, thereby improving image quality.Prediction of ISAR imaging plane of ship targets is studied in chapter 3. According to the theory of radar imaging, a computing method of imaging plane is presented firstly. On that basis, two imaging plane prediction methods——geometric projection method and range-doppler mapping method are proposed. Finally, the obtained two-dimensional projections of the ship targets in the imaging plane via these two methods are compared with the ISAR image achieved by simulating separately to verify the correctness of these two methods.In chapter 4, making use of the time-frequency analysis methods to get the ISAR images of ship targets is studied. Firstly, the principle of ISAR imaging based on time-frequency analysis is illustrated. Then, we can find that time-frequency distribution series (TFDS) method and modified smoothed pseudo Wigner-Ville distribution (MSPWD) method not only have good time-frequency concentration but also can suppress the cross-term interference effectively by comparing. These two methods can be used for ISAR imaging of non-stationary moving target. Simulation results indicate that by replacing the Fourier transform with TFDS or MSPWD for ISAR imaging of ship targets, a series of clear instantaneous images can be obtained.In chapter 5, the work of the whole thesis is concluded and the issues to be further studied are pointed out as well.