Sensitivity of electromagnetic waves to a heterogeneous bianisotropic structure

We study how the perturbations of a generally heterogeneous bianisotropic structure manifest themselves in the wave field, and which perturbations can be detected within a limited aperture and a limited frequency band. A short-duration broad-band incident wave field with a smooth frequency spectrum is considered. Infinitesimally small perturbations of the constitutive tensor are decomposed into Gabor functions. The wave field scattered by the perturbations is then composed of waves scattered by the individual Gabor functions. The scattered waves are estimated using the first-order Born approximation with the paraxial ray approximation.