Improvement of Doppler central frequency estimation in existence of hard target

Estimation of Doppler central frequency has an important effect on accuracy of fixed position in the fixing approach with no reference points for ocean SAR. In this paper, the case has been studied that there are strong scatter points in the imaging area, which are scanned partly by antenna beam. A time-frequency means is proposed to filter out the strong points through WVD transform. The effect of this means is verified by simulation results lastly.