A technique for extrapolating numerically rigorous solutions of electromagnetic scattering problems to higher frequencies and their scaling properties

The possibility of extrapolating the current distribution on two-dimensiona l scatterers to high frequencies, from the knowledge of the solution at two or more lower frequencies, is investigated in this paper. A simple extrapo lation algorithm is developed in which the current distribution is first ca lculated at two lower frequencies, and then split into propagating or decay ing traveling wave components in the lit and shadow regions, These componen ts are scaled to higher frequencies, by using simple operations such as str etching of the magnitude and linear extrapolation of the phase. This techni que enables one to solve a class of large-body scattering problems, well be yond the range of rigorous numerical techniques. Furthermore, the extrapola ted solution is rapidly constructed over a very wide range of frequencies, typically by utilizing the rigorous solution at only two lower frequencies. The application of the extrapolation algorithm is demonstrated for several examples, viz., an ellipse with a high aspect ratio, and wing-shaped geome tries with rounded and sharp edges. The robustness of the technique is illu strated by considering grazing angles of incidence where the asymptotic tec hniques typically break down.