Entropy-Based Doppler Centroid Estimation and Speckle Noise Reduction for Spaceborne SAR Imaging

TL;DR

This paper introduces an entropy-based method for estimating Doppler centroid frequency and a speckle noise reduction technique to enhance spaceborne SAR image quality, validated with RADARSAT-1 data.

Contribution

It proposes a novel entropy-based Doppler centroid estimation method and an effective speckle noise reduction approach for spaceborne SAR imaging.

Findings

Improved image focus through accurate Doppler estimation

Significant noise reduction in reconstructed images

Validation with real satellite data confirms effectiveness

Abstract

In this paper, we present strip-map mode spaceborne Synthetic Aperture Radar (SAR) imaging with the focus on Doppler centroid frequency estimation. The non-zero Doppler centroid frequency is the result of non-zero squint angle which if it is not compensated it can de-focus the image. We present an efficient method based on the entropy of the reconstructed image to estimate the fractional part of the Doppler centroid frequency. Furthermore, we discuss the speckle noise, which degrades the quality of the reconstructed images considerably, and attempt to alleviate its effect efficiently. Following the implementation of the speckle noise reduction algorithm, a significant improvement in the quality of the reconstructed images is achieved. Finally, we utilize the experimental data gathered from the RADARSAT-1 satellite of Vancouver Canada to verify the accuracy and effectiveness of the proposed techniques.