Comparison between FDTD and UTD for the two dimensional case of a lossy dielectric wedge

Limits of validity of the uniform theory of diffraction when applied in non-standard conditions are investigated through the use of an exact method (FDTD) which has been previously adapted. Both methods are implemented for the calculation of diffraction by a lossy dielectric wedge. First we report a new expression of the diffracted field. Then we outline the adaptation needed to the classic FDTD grid calculation to isolate only one edge diffraction. We present the results obtained through a parametric study concerning the conductivity, the permittivity, the observation distance and the apex angle of the wedge. Agreement is very good in most cases, whatever the complex permittivity, and in particular the relevance of the new diffraction coefficient is demonstrated. A very interesting result as well is that the closer the observation point to the apex the better is the agreement between UTD and FDTD.