Imaging Of Ship Target Using Synthetic Aperture Radar

Synthetic aperture radar (SAR) is an important technology in modern radar for its all-weather, day and night, long distance capability to provide high-resolution maps of the Earth’s surface, so it is of great value both in civil and military applications. The imaging algorithm is the core of the SAR signal processing. Generally speaking, SAR deals with only static targets. A noncooperated moving target appears blurred in the SAR image. In this dissertation, the basic algorithm of SAR is improved and extended to realize the imaging of ship target.Chapter 1 is the introduction. The modes of SAR imaging are outlined. Then the status of the latest development in China and abroad is reviewed. The background and main contents of this research are addressed.Chapter 2 aims at the difficulties of serious range cell migration and decrease of solution in the mode of squint imaging. The linear range-Doppler algorithm based on turntable imaging is presented. This algorithm can be applied in engineering, which is simple, effective, with small computation and high real-time performance. In addition, the algorithm can focus stably in condition of large squint angle, and satisfy the requirements of resolution in a certain imaging area.In chapter 3, the technology of digital spotlighting which is used to reduce the blurring caused by ship motion is presented. The core of the technology is to realize secondary motion compensation with given point as reference in the digital signal processing of radar echo data. It equivalents to making the center of radar beam aim at the target so that any interested target can be "spotlighting" illuminated. This technology improves the image quality of moving target greatly. And when we search the optimal imaging velocity using the technology, we obtain the radial velocity of target. The ship-target simulations fully prove the effectiveness of the technology.It’s an important function of synthetic aperture radar to locate the target. In the process of the imaging of ship target using SAR, the positioning accuracy of airborne SAR will be influenced by unknown error brought by the inertial navigation system. In chapter 4, the geometric model of SAR target localization is established. How the unknown error brought by the inertial navigation system influence the positioning accuracy is discussed. Then the mathematic expression is derived which is helpful to the design of positioning precision index of the SAR system.In chapter 5, the work is concluded and the possible problems to be further researched are also pointed out.