On the use of virtual ground scatterers to localize double and triple bounce scattering mechanisms for bistatic SAR

In Radar remote sensing, the electromagnetic (em) modeling of scattering contributions from natural or man-made scatterers has often to deal with coupling scattering mechanisms due to the underlying reflecting surface (ground or water). For the monostatic configuration, this contribution is commonly associated with the so-called double bounce scattering mechanism, which is also known to be located in synthetic aperture radar (SAR) images at the vertical projection of the scatterer onto the ground. To explore this phenomenon in the more general case of bistatic SAR but also for triple bounce scattering, a new formalism using virtual scatterers is introduced in this paper. Based upon image theory and on far-field assumption, these virtual points are defined by simple interaction scatterers located on the reflecting surface, and involving the same traveling wave path than the considered scattering mechanism. Depending only on the incidence and scattering angles, elegant formulae in their simplicity are highlighted to construct these fictitious scatterers. The resulting reduction of multiple to simple interaction scattering mechanisms simplifies the finding of their location within bistatic SAR images, generalizing thereby migration effects associated to coupling mechanisms in the bistatic configuration.