A Nonlinear Polynomial Filter for Sidelobe Suppression of Spaceborne and Airborne Synthetic Aperture Radar (SAR) Images With High Resolution

A nonlinear polynomial filter (NPF) was proposed for the sidelobe suppression in synthetic aperture radar (SAR) imagery with high resolution. The single-sinc and multiple-sinc cases were examined. In the single-sinc case, one target existed, and the other surrounding targets were absent or weak scatterers that can be ignored. Otherwise, the cases were considered as multiple-sinc cases. A judge function was computed using the underlying sample and two adjacent samples for every sample in the image domain. This function was the basis to determine whether the related sample fell under the single-sinc case or not. If it was the single-sinc case, the judge function was also used to reduce the sidelobes. A polynomial filter was used for the sidelobe suppression in the multiple-sinc cases. Using the polynomial filtering, the energy of sidelobes was reduced by dividing a polynomial function. The unequivocal determination of sidelobe suppression was achieved for SAR data. The performance of the proposed algorithm was evaluated using acquired spaceborne SAR and airborne SAR data with high resolution. The effectiveness of the sidelobe suppression was qualitatively and quantitatively examined, and the results were satisfactory.