INVERSE SCATTERING ANALYSIS OF DIFFRACTION LIMITED SAR

As opposed to conventional narrow-band SAR, a theory of diffraction-limited SAR imagery is developed. Data are assumed to be collected by an airborne radar, operating at relatively low frequencies, covering a relative bandwidth approaching unity (a practical choice would be a bandwidth span 10-100 MHz). The radar antenna is required to be omnidirectional, so as to allow a very large relative Doppler bandwidth as well. In this paper, the inverse problem of reconstructing the ground topography on the basis of collected data is set up and solved analytically. The solution incorporates compensation for antenna effects—an interferometric antenna configuration provides the required discrimination between left and right hand side returns. The inversion process leads to a twodimensional Poisson equation for the ground surface angular height function, the source density of the equation corresponding to the conventional SAR ground reflectivity. Because the shape of the ground is described relative to the aircraft, there will be a certain latitude in this description, relating to aircraft motions, which will not affect radar data. Except for this, the scheme provides a unique estimate of the ground topography at a very high resolution (near 1 m for 90 MHz bandwidth). © 1990 IEEE