Solution of the inverse electromagnetic scattering problem in the resonance case

In the scattering process of electromagnetic waves from dielectric or conducting targets, one often encounters resonances in frequency in the returned echo signals. In previous studies on the scattering of acoustic and elastic waves, analogous resonant echoes were shown to contain a wealth of information on the properties of the scattering target, permitting, in fact, the complete solution of the corresponding inverse problem. The same is recognized to be the case for the electromagnetic scattering problem considered here. For the case of dielectric or coated conducting spherical targets, the spacing and the widths of the resonances are shown to determine the dielectric constant and the coating thickness of the target in a direct fashion.