An extrapolation technique for solving a class of large-body scattering problems by using the FDTD

An extrapolation technique has been devised in the frequency domain for solving a class of large, two-dimensional and body of revolution (BOR) type of scattering problems, both with and without edges and tips. In this approach, one first derives the solution for the induced current on a scatterer at two lower frequencies, where the body size is still manageable, and the problem can be treated by using conventional, numerically-rigorous techniques. Next, one decomposes the computed current distribution in terms of its constituent travelling wave components, and subsequently extrapolates the behavior of these components to frequencies that are much too high to be handled directly by the conventional techniques. The objective of this paper is two-fold. First, to take advantage of the inherent characteristics of the FDTD method that it can handle larger problems than the MoM, and that it yields the field solution over a wide band of frequencies with a single run. Hence, the extrapolation can be carried out by using a large number of lower frequency solutions to attain better accuracy than is possible with just two. Second, to demonstrate that the extrapolation is also possible for a class of three-dimensional scatterers with edges and corners, e.g., a cube, even at grazing incidence where the asymptotic methods are known to suffer from accuracy problems.