I. Introduction
Synthetic aperture radar (SAR) is a common remote sensing payload that actively emits electromagnetic waves and receives its echo to acquire Earth surface scattering information. Contributed to its waveband being less affected by atmospheric attenuation, SAR can achieve global monitoring and information collection all day and all weather [1], [2]. The energy of fully collected information scattered by ground targets disperses within the complex-valued echo, lacking the remarkable features to distinguish various targets [3]. In order to achieve clear features with sufficient resolution and signal-to-noise ratio (SNR), the echo energy needs to undergo specific processes, such as pulse compression [4] and range cell migration correction (RCMC) [5] in the complex-valued signal domain. The processed results are usually presented as real-valued intensity images, which abandon some physical signal-domain features but retain the most intuitive, basic visual features for image understanding and interpretation [6].