Reduction of vibration-induced artifacts in synthetic-aperture-radar imagery using the fractional fourier transform

In synthetic aperture radar (SAR) images of objects exhibiting low-level vibrations are accompanied by localized artifacts, or ghost targets, caused by the micro-Doppler present in the returned SAR signals. Conventional Fourier-transform-based SAR processing techniques are not fit to remove ghosting effects prior to image formation due to the non-stationary nature of the returned signals from vibrating objects. Recently, a method based on the discrete fractional Fourier transform (DFrFT) has been developed for estimating the instantaneous vibration accelerations and vibrating frequencies from returned SAR signals. Here, a novel image de-ghosting algorithm for vibrating targets in SAR imagery is proposed by employing the DFrFT-based vibration-estimation algorithm. The proposed de-ghosting method is applied to SAR data collected by the Lynx SAR system. Experimental results show a substantial reduction in ghosting caused by a 1.5-cm amplitude, 0.8-Hz vibration present in a test target.