Ships imaging based on the fractional autocorrelation

Due to the noncooperative motions of maneuvering target, as ships, the Doppler shifts of scatterers are usually timev-arying, so that the Range-Doppler algorithm becomes incapable to form synthetic aperture radar (SAR) imaging. The echo embodying such maneuvering targets is approximated as multi-components chirp signal. Thus, Doppler estimation for multi-components chirp is needed in Range-Instantaneous-Doppler imaging for maneuvering targets. To imaging noncooperative ship target at sea, a new algorithm based on fractional autocorrelation was presented in this paper. The echo from every range cell was correlated by the rotating operator in the time-frequency plane. And the doppler parameters of target were estimated accurately to get fine images, by searching the peak value in the fractional domain. The approach is verified by Radarsat data.