Diffraction by lossy dielectric wedges using both heuristic UTD formulations and FDTD

An improvement of the uniform theory of diffraction (UTD) coefficient for the case of a lossy dielectric wedge when a transmitted ray exists is presented. We elaborated two new terms that are added to the classical UTD diffraction coefficient, so that we obtain continuity of the total field. This new UTD formulation is compared to a numerical method based on finite difference time domain (FDTD). We outline the adaptation of the FDTD grid calculation, which was necessary to isolate only one edge diffraction and to treat two-dimensional (2-D) structures with two infinite sides. This comparison allows one to conclude that the new diffraction coefficient is relevant for the case of a lossy dielectric wedge. Then we present a comparison between two different versions of the UTD diffraction coefficient based on single or multiple reflection in the case of a dielectric slab. Thus, we can conclude to the significance of the multipaths for modeling dielectric structures. Finally, we analyze the results obtained with two consecutive wedge vertices in order to show that the slope diffraction related to the doubly diffracted field allows one to predict the field behind the structure when the transmitted field does not exist.