The High-Resolution Synthetic Aperture Radar System and Signal Processing Techniques: Current progress and future prospects [Review Papers]

High-resolution Synthetic Aperture Radar (SAR) systems have played an increasingly important role in remote sensing applications, such as environmental monitoring, Earth resource mapping and military investigations. With centimeter-scale resolution, SAR provides high-quality remote sensing data. To achieve high-resolution SAR imaging at the centimeter level, the ultrawide-band (UWB) signal should be precisely generated, transmitted, recorded and processed; however, these processes may be limited by hardware performance, system integration issues, challenging processing solutions, etc. Moreover, to obtain high-resolution data in the azimuth dimension, the azimuth beam steering angle should be extended to tens of degrees, and corresponding the nonlinear beam steering scheme and the varying sampling window start time (SWST) technology for efficient data acquisition are described in detail. In this work, to improve the quality of imagery, the key issues related to SAR imaging using nonlinear frequency-modulated signals are reviewed. The Aerospace Information Research Institute, Chinese Academy of Sciences (AIR-CAS) has been devoted to advancing very-high-resolution (VHR) SAR imaging techniques over the past decades. In this paper, we provide an overview of the very-high-resolution SAR techniques, processing methods, and experimental results reported by AIR-CAS.