The Researches On The Motion Compensation Of Airborne SAR

High resolution airborne synthetic aperture radar (SAR) is an important direction for SAR. Currently, the advanced countries are trying their best to develop high resolution SAR systems. SAR mode and its corresponding image formation algorithms are the main problems for high resolution airborne SAR. But as the resolution requirement increased, motion compensation becomes the critical factor to impact the improvement of resolution for airborne SAR. Motion compensation technique is a key to realization of high resolution airborne SAR. To research high resolution airborne SAR, it is necessary to carry on deep researching on motion compensation problems.My thesis work is organized as follows. First, I review the fundamental principles of SAR imaging, the model of SAR system, and echo signals, the geometry of airborne SAR and the basic compensation methods are briefly introduced, then through mathematical derivation I analyze how SAR image quality is degraded by phase errors and quantitatively derive motion errors that are induced by undesired flight during the disarrange of the synthetic time. Second, the phase error still exits after the real-time compensation by motion sensors, the compensation algorithms based on the echo data are helpful to eliminate the remained error, so the next I do my research based on the echo signals mostly, In particular, I compare four practical auto-focus techniques, such as map-drift (MD), phase difference(PD), contrast optimization, and phase gradient auto-focus(PGA). This paper especially researches on PGA and its implementation in discrete domain, analyses and summarizes some relevant problems which have well-deserved reputation for airborne high order auto-focus. Third, this paper presents an approach to intergrate the auto-focus algorithm with chirp-scaling algorithm(CSA), by this way, the advantage of CSA can be given a full play. This paper also suggests a method to combine motion compensation based on auto-focus algorithm with radar data in CSA, this method is very suitable for high-resolution airborne SAR. Forth, this paper discusses the special problems on motion compensation in real-time processing of high resolution airborne SAR.