The aim of this paper is to present a frequency domain method for synthetic aperture radar (SAR) imaging. By using two consecutive linear mappings along Doppler and frequency domains, an azimuth-dependent SAR transfer function has been discovered. Based on this new transfer function, the SAR image can be reconstructed by the proposed azimuth stacking algorithm. The new algorithm can form SAR image at each azimuth position without DFT wrap around errors. If Chirp z-transform (CZT) is applied to carry out the two consecutive mappings (since they are linear mappings), the proposed algorithm will not require interpolations and thus its reconstructed image would be free of truncation errors. The new algorithm has been validated using both simulated and experimental ultrawideband/widebeam (UWB/WB) SAR data.
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