Transient scattering problems solution by surface equivalent sources

A numerical study is developed to evaluate the response of a system excited by a transient incident field. A new formulation is introduced in order to apply surface impedance boundary conditions (SIBC) while adopting the scattering formulation. The elimination of conductive regions requires the imposition of appropriate interface conditions, which are represented by equivalent current sources depending on the incident field. In the time domain the equivalent sources are described by a convolution integral in which appears the transient surface impedance derived analytically by the inverse Laplace transform. The resulting equations system is solved by applying the finite element method (FEM) in space and the Crank-Nicolson scheme in time