A quasi-planar incident wave excitation for time-domain scattering analysis of periodic structures

Preprint, 2005

We present a quasi-planar incident wave excitation for time-domain scattering analysis of periodic structures. It uses a particular superposition of plane waves that yields an incident wave with the same periodicity as the periodic structure itself. The duration of the incident wave is controlled by means of its frequency spectrum or equivalently the angular spread in its constituting plane waves. Accuracy and convergence properties of the method are demonstrated by scattering computations for a planar dielectric half-space. Equipped with the proposed source a time-domain solver based on linear elements yields an error of roughly 1 percent for a resolution of 20 points per wavelength and second order convergence is achieved for smooth scatterers. Computations of the scattering characteristics for a sinusoidal surface and a random rough surface show similar performance.