Effective minimum entropy algorithm for SAR ground moving target imaging

Ground moving target (GMT) is defocused and displaced in conventional synthetic aperture radar (SAR) image, because there exists the residual phase error of non-cooperative GMT motion. In this study, an effective minimum entropy algorithm (EMEA) for SAR ground moving target imaging (GMTIm) is proposed based on the range migration algorithm and region of interest (ROI) data. The moving target ROI data is extracted from conventional SAR image after RMA processing. Then, the image entropy function and its first-order derivative are constructed with respect to phase compensation parameter. EMEA uses the idea of bisection to shrink the parameter value range. The key point of this method is to shrink the parameter value range according to the sign of derivative of entropy function and ensure that the optimal parameter is always within the value range. When the algorithm converges, the optimal parameter occur and the refocused GMT image can be obtained using this parameter to compensate the residual phase error.