SEM representation of transient scattering from conducting planar objects in layered media

The scattering of a plane wave from conducting planar objects in layered media has been analysed by a frequency-domain method of moments (MoM) with rooftop basis functions and Galerkin´s procedure. Green´s functions for layered media involved in the computation of the matrix elements are evaluated using the closed-form expressions obtained from the robust approach using the generalised pencil-of-function (GPOF) method. The time-domain scattered field from the scatterer illuminated by an electromagnetic pulse is obtained from its frequency-domain data via the inverse fast Fourier transform (FFT). The poles and residues of the time-domain response are then extracted via the GPOF method. The singularity expansion method (SEM) representation of the time-domain response using the poles and residues is finally obtained. The pole locations in a complex frequency plane as a function of the substrate thickness, relative dielectric permittivity and dielectric loss are also investigated. Complex natural resonances for a microstrip dipole and patch are sufficiently diverse for identification purposes, thus demonstrating that only pole and residue information is required for target characterisation