Study On Airborne ISAR Imaging Of Ship Targets And Estimation Methods Of Its Heading Angles

Inverse synthetic aperture radar(ISAR) is a high resolution imaging radar, its main purpose is to solve the imaging problem of moving target with non-cooperation. ISAR has significant application value in military and civil fields due to the characteristics of long range detection, all-weather and all-day work capability. This thesis mainly studies the signal processing methods; the imaging plane prediction methods for airborne ISAR imaging of ship target and the heading rotation angle estimation method of targets in ISAR image as well. The main contributions are shown as follows:Chapter 1 introduces the status and development of ISAR, presents the research background and significance, illustrates several ISAR radar system and the main contents of this thesis.Chapter 2 mainly studies the airborne ISAR ship target imaging signal model and imaging surface algorithm. On the basis of airborne ISAR ship target imaging mechanism, the model of ship target echo signal is discussed in detail and the mathematical formula is derived. According to the theory of SAR imaging, the target imaging surface selection method and two kinds of methods for the verification of the ISAR imaging of the point target of the ship are obtained which named Geometric Mapping Algorithm and Range Doppler Reconstruction algorithm. Finally, estimates the target imaging surface by these two algorithms. The results are compared with the traditional ISAR image and the correctness and validity of these two kinds of algorithm are proved.Chapter 3 discusses the ISAR motion compensation technology which includes the ISAR range alignment technology and phase compensation technology. On the basis of ISAR turntable imaging's principle, studied several airborne ISAR ship target imaging range alignment and phase compensation methods respectively, applies these methods to two groups of ship target measured data, the advantages and disadvantages of these methods of the imaging of ships in airborne ISAR are concluded by analyzing the results with three quantization criteria for the quality of ISAR images.Chapter 4 mainly studies the airborne ISAR ship target imaging rotation heading angle of rotation estimation algorithm. Based on the ship point target in ISAR imaging, using characteristic properties of Fourier transform in two-dimensional space and the mapping relations after the polar coordinate transform, proposes a heading angle of rotation estimation algorithm based on polar coordinates transform. Using Radon transform in two-dimensional ISAR image to convert the plane parameters results in a heading angle of rotation estimation algorithm based on Radon transform can be obtained. Finally, we process the data of ship target simulation and the effectiveness of these two kinds of algorithm is verified.Chapter 5 summarizes the work of this paper and prospects the future research directions.