Research On Signal-Based Large Region High-Resolution Airborne SAR Imaging

Airborne synthetic aperture radar (Airborne SAR) is a kind of high-resolution imaging radar, Its platform is aircraft, in distance it acquires high-resolution by emitting wide-bandwidth and in azimuth by synthetic aperture principle. All image algorithms is built on ideal SAR model and that means the airplane flights in a straight line with a constant speed , but when the platform flies in a low altitude, it will be influenced inevitably by air disturbance, especially light aircraft platform, and that will deviate the platform from the ideal trajectory resulting in larger motion error. So it is necessary to compensate the motion error especially in high-resolution airborne synthetic aperture radar image, and error compensation is a very popular research topic in the field of airborne SAR.In general, two kinds of methods are used in airborne SAR motion compensation: compensation based on motion sensors and compensation based on SAR data LFM and pulse compression technique. In this paper, compensation based on SAR data will be the main content. We build the motion error model, analyze the differences in high band large aperture echo data and conventional echo data to find their own characteristics and correspondingly use different methods to compensate them. In this paper, the phase compensation methods on high band large aperture echo data are the main research. The main contents are following:1. Introduce the basic principles of SAR imaging, build the imaging model, evaluate the effect of motion errors on the imaging quality due to air disturbance. Establish the true model of the motion errors, research conventional motion errors and Aperture-Dependent errors in large synthetic aperture situation and evaluate the effect on imaging quality.2. Analyze the large aperture high-band data and conventional data, find their own characters by means of using several motion compensation methods in large aperture high-band data and conventional data, then propose the relevant motion compensation methods. In this paper, several conventional motion compensation algorithms are described in detail, and use improved MD phase compensation algorithm to process large aperture high-band data.3. In synthetic aperture radar, high azimuth resolution generally needs large synthetic aperture and large accumulation angle, when radar work in stripmap mode, the echo data will contain large residual motion error in Azimuth, this paper introduces the effect of this error, and discusses several methods to compensate the residual error.