Study On ISAR Motion Compensation And Imaging Technology For Ship Targets

Inverse synthetic aperture radar (ISAR) is a kind of radar which can obtain the highresolution imaging. It uses the relative motion between the radar and targets to synthesizelarge aperture, and can be able to obtain the high resolution images of non-cooperativemoving targets, such as vehicles, ships, aircrafts and satellites. The ISAR can workall-weather and all day, and has a great application prospect in military and civilianaspects.The ISAR imaging mainly includes two parts: motion compensation and imaging.Based on the study of the existing motion compensation methods, a new ISAR rangealignment method using Tsallis entropy is proposed in this thesis, and the feasibility andanti-noise of this method are analyzed in detail. The real-data processing results verify thatthis method can get better range alignment effect than the traditional envelop minimumentropy method. The ship’s motion is more complicated than the motion of the aircraft andvehicles due to the complex sea state. Thus, the ship imaging is a difficulty in ISARimaging, and it is also a research hotspot in today’s marine equipment of our country whichneed to urgently develop. Due to the lake of real data, the previous study of ship ISARimaging mainly rely on simulation data. Based on the ISAR real data of ship targets, theISAR high resolution imaging technology of ship targets is mainly studied in this thesis,and the optimal imaging time selection methods, compressed sensing methods and thecross-range scaling methods are applied to the real data to obtain the high quality ISARimages of ship targets.Chapter1is the introduction. The research background and significance of ISAR areintroduced firstly. Then, the ISAR research status both at home and abroad are elaborated,and finally the main contents of this thesis are given.In chapter2, the ISAR motion compensation technology is studied, which mainlyincludes the ISAR range alignment technology and the ISAR phase compensationtechnology. Several different range aligment methods and phase compensation methods arestudied and applied to the ISAR real data. At the same time, a new range alignment methodusing Tsallis entropy is proposed in this thesis. The implementation steps of this methodare introduced in detail and the effectiveness and anti-noise performance of this method arealso analysed and validated. Finally, the method is applied to ISAR real data and the performance is compared with the traditional envelope minimum entropy method.In chapter3, the ISAR imaging methods of ship targets based on the optimal timeselection are studied. In order to obtain high quality ISAR images of ships, the optimalimaging time needs to be selected. First of all, the ISAR received signal model of shiptargets is analysed. Then, the optimal imaging time selection methods based on the Dopplerfrequency spread estimation and the Doppler centeral frequency estimation are studied indetail, respectively. ISAR real data of ship targets are processed to demonstrate theperformance of these two methods. High quality ISAR images of ships are finally obtained.In chapter4, the ISAR imaging methods of ship targets using compressed sensingtechniques are studied. The theory of compressed sensing is applied to the ISAR imagingto obtain high quality ISAR images of ship targets. Firstly, the theory of compressedsensing and the ISAR imaging principles based on compressed sensing are analyzed. Thenseveral image reconstruction algorithms based on CS are studied. Finally, the ISAR realdata of ships are processed to get the compressed sensing imaging results of ship targets.In chapter5, the cross-range scaling methods for ISAR images of ship targets arestudied. In order to realize the identification and recognition of ship targets, a scaling ofthe ISAR images is needed. Firstly, the principle of ISAR cross-range scaling is analyzed.Then, the image cross-correlation based cross-range scaling method, the Martorellacross-range scaling method, and the multi-dominant scatterers cross-range scaling methodare studied to perform the scaling of the ISAR images of ship targets. Finally, the scaledISAR images of ship targets are obtained.Chaper6is the conclusion, which summaries this thesis, and makes a prospect for thefuture research.