FDTD analysis of axially symmetric artifically soft structures

In this work, the finite-difference time-domain method was applied to analyze the EM response of a corrugated, soft circular disc, when it is illuminated by a vertical electric dipole. Two different time-varying excitations were considered: a Gaussian pulse signal and a sinusoidal wave. The steady-state analysis for the sinusoidal excitation allows the prediction of the fields distribution all over in the space while the transient analysis allows a wide-band characterization of the artificially soft properties and then the exploration of a few application possibilities. The analysis was carried out in a cylindric coordinate system where, taking advantages from the rotational symmetry, the 3D problem reduces to an exact 2D one. Proper absorbing boundary conditions were enforced on the external boundary of the grid.