A new approach to synthetic aperture radar (SAR) digital image formation, based on inverse scattering theory, is derived as an alternative to the conventional method of imaging surface-scattered wave fields. The conventional image formation technique for high-resolution SAR data utilized azimuth compression using correlation in the range-Doppler domain. More recent approaches in SAR image formation algorithms exploit downward extrapolation of the wave field in the frequency–wavenumber (f–k) domain to perform not only the azimuth compression but also the range curvature correction at the same time, with improved quality of the final image. In this paper, imaging of the SAR wave field is formulated with the Born inversion approach, which includes a range-curvature-correction term that is valid at all ranges of image formation. This new inversion formula is established to exploit f–k domain computation, from which the complex backscattering coefficient, defined by the ratio of the backscattered wave field to the incident wave field, can be accurately estimated from the observed back-scattered wave field.
Quantitative measures in ISAR image formation based on time-frequency representations
