Introduction

Synthetic aperture radar (SAR) is a type of imaging radar that receives wideband echoes at different positions through relative movement between the loading platform and the target. SAR has covered military, civil, and scientific applications, where the platforms include unmanned aerial vehicles, helicopters, fixed‐wing manned aircraft, satellites, and missiles. SAR is similar to other types of radar systems regarding the composition of the radar equipment. However, SAR has unique features in terms of the platform loading mode, radar system, and information processing. More and more, applications show an urgent need for a wide swath, high resolution, high accuracy, real‐time acquisition and processing, and timely update of SAR observation data. Some new technologies and methods that are appearing and will appear will give new vitality to the traditional SAR system. These new technologies and methods have been widely studied.