Images of urban areas by a synthetic aperture radar simulator

An urban scene is a very complex variety of length scales ranging from much bigger to much smaller than the wavelength of the radiation emitted by a Synthetic Aperture Radar (SAR). The exact solution to this scattering problem requires the solution of Maxwell's equations for the combination of source and scattering objects present in the scene, which for any reasonable size target area is computational too large to be realistic. Hence while a 'numerically exact' solution is ruled out but as is usual in electromagnetic problems some form of appropriate modeling scheme is used. In this case we assume that the major contributors to the scattering are the planar surfaces which are generally many times larger than the wavelength of the radiation used. A geometrical optics ray-tracing approach is employed to calculate the incident field on each surface illuminated by the radar system whether by direct or indirect illumination (multiple bounces within the target environment geometry). In this way the large amount of multiple scatter that arises from the combination of dihedral and trihedral corners associated with buildings is taken into account. The strength or amplitude and polarization characteristics of the radiation returning to the radar can be calculated by applying the Rayleigh-Rice scattering theory at each surface.