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-dimensional scatterers to high frequencies, from knowledge of the solution at two or more lower frequencies, is investigated in this paper. A simple extrapolation algorithm is developed in which the current distribution is first calculated at two lower frequencies, and then split into propagating or decaying traveling wave components in the lit and shadow regions. These components are scaled to higher frequencies, by using simple operations such as stretching of the magnitude and linear extrapolation of the phase. This technique enables one to solve a class of large-body scattering problems, well beyond the range of rigorous numerical techniques. Furthermore, the extrapolated 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 geometries with rounded and sharp edges. The robustness of the technique is illustrated by considering grazing angles of incidence where the asymptotic techniques typically break down