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 isof great value both in civil and military applications. The imaging algorithm is the core of the SARsignal processing. Generally speaking, SAR deals with only static targets. A noncooperated movingtarget appears blurred in the SAR image. In this dissertation, the basic algorithm of SAR is improvedand extended to realize the imaging target of ship using SAR.Chapter1is the introduction. The history of SAR technology is introduced. Then the status ofthe latest development in China and abroad is reviewed summarily. The background and maincontents of this research are addressed. Besides the modes of SAR imaging are also outlined and theresolution of the SAR system is addressed and analyzed.Chapter2investigates the model of moving target echoes, and discusses in detail the effect ofmoving target on the conventional SAR image.Chapter3aims at the difficulties of serious range cell migration and decrease of solution in themode 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 andhigh real-time performance. In addition, the algorithm can focus stably in condition of large squintangle, and satisfy the requirements of resolution in a certain imaging area.In chapter4, the technology of digital spotlighting which is used to reduce the blurring causedby ship motion is presented. The core of the technology is to realize secondary motion compensationwith given point as reference in the digital signal processing of radar echo data. It equivalents tomaking 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 wesearch the optimal imaging velocity using the technology, we obtain the radial velocity of target. Theship-target simulations fully prove the effectiveness of the technology.Besides,for SAR imaging ofmulti-ship targets at sea,it’s difficult to generate high quality images for each ship target in real timebecause the motion characteristic of the individual target is different from others and blind in mostcases. Aiming at this problem, this paper presents a parallel signal processing scheme for airborneSAR multi-ship imaging based on the digital spotlight technique. By this method, the raw datacontaining multi-target signal is processed only once using the well-known linear range Doppleralgorithm. Then, after the coarse complex image is obtained, the digital spotlight technique is carried out to extract the each selected ship data from the wide area image and reform the motioncompensation processing to improve the focusing performance. Furthermore, the proposed signalprocessing structure and related computational burden is much convenient for parallel processing. Theanalyses of the simulation results show the validity of the methodology.In chapter5, the work is concluded and the possible problems to be further r parallel processingpointed out.