SAR Imaging of Moving Target based on Knowledge-aided Two-dimensional Autofocus

TL;DR

This paper introduces a 2-D autofocus method for SAR imaging that effectively refocuses moving targets by estimating azimuth phase error and deriving residual phase errors, improving image clarity and computational efficiency.

Contribution

The paper presents a novel 2-D autofocus technique that estimates azimuth phase error directly and computes residual errors from it, enhancing SAR image focusing of moving targets.

Findings

Improved focusing of moving targets in SAR images.

Reduced computational complexity in phase error estimation.

Enhanced accuracy in 2-D phase error correction.

Abstract

Due to uncertainty on target's motion, the range cell migration (RCM) and azimuth phase error (APE) of moving targets can't be completely compensated in synthetic aperture radar (SAR) processing. Therefore, moving targets often appear two-dimensional (2-D) defocused in SAR images. In this paper, a 2-D autofocus method for refocusing defocused moving targets in SAR images is presented. The new method only requires a direct estimate of APE, while the residual 2-D phase error ( or RCM) is computed from the estimated APE by exploiting the analytical relationship between the 2-D phase error ( or RCM) and APE. Because the parameter estimation is performed in the reduced-dimension space by exploiting prior knowledge on phase error structure, the proposed approach offers clear advantages in both computational efficiency and estimation accuracy.