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Focusing resonance signatures in ultra-wideband SAR

Low-frequency ultra-wideband (UWB) synthetic aperture radars (SAR) provide new capabilities for target detection and classification. Resonance signatures of targets are among the most useful features for target discrimination. However, these resonance returns are normally smeared out in focused SAR images due to their late arrival time. This paper shows that these resonance signatures can be focused by postfiltering the SAR image with a special class of all-pass filters. FIR approximations to these all-pass filters can be designed with a modified radial slice approximation algorithm. We demonstrate the performance of the designed filters on synthetic data.