This paper addresses the problem of estimating the DC (doppler centroid) for SAR (synthetic aperture radar) data, in presence of speckle and thermal noise. The main idea is to exploit a bandwidth much wider than the PRF (pulse repetition frequency), say 3-5 times, by exploiting strong point targets. Natural and isolated targets with close-to-ideal features are focused using a digital spotlight algorithm applied to stripmap acquisitions; then, accurate DC is estimated as the relative shift of

more »

... targets azimuth spectra using the ML (maximum likelihood). The Cramer-Rao bound of the estimate is shown to be lower than that of the conventional estimators based on traditional stripmap focusing of Q + 1 times for high SNR (signal-to-noise ratio) of targets, being Q the oversampling factor of the spotlight processing compared to the stripmap one. The method is applied to both simulated targets and a real dataset coming from the Cosmo SkyMed X-band constellation.