A two-step approach to the processing of high-resolution SAR satellite data based on the chirp z-transform

The processing of high resolution spotlight synthetic aperture radar (SAR) data suffers from Doppler spectrum aliasing because of the limited pulse repetition frequency (PRF). A modified two-step approach (TSA) based on the chirp z-transform (CZT) to high resolution spaceborne SAR data processing is proposed to deal with the spectral aliasing problem in this paper. The range frequency dependent quadratic phase function applied in modified TSA, which can remove the Doppler modulation of the signal completely, gives rise to the effect that the Doppler bin size varies with the range frequency. Thus, the extra spectrum resampling procedure is required to obtain a uniformly sampled signal spectrum. A spectrum resampling approach based on the chirp z-transform is proposed, which can overcome the range frequency dependent distortion. Experiments are performed on simulated point and experimental SAR data to validate the presented approach.