Hybridization of SBR and FEM for scattering by large bodies with cracks and cavities

High-frequency methods, such as shooting-and-bouncing-ray (SBR) [Ling et al., 1989], are very efficient for computing electromagnetic scattering from large targets whose sizes are on the order of tens or hundreds of wavelengths. However, they cannot incorporate the contributions from small features such as cracks, gaps, cavities, and microstrip patch antennas, whose smallest dimension is on the order of a fraction of a wavelength. Therefore, a high-frequency method alone cannot accurately treat large and complex targets with these small features. In the present paper, the authors present a robust hybrid technique to remove this limitation on high-frequency methods. This new technique combines a high-frequency method with a low-frequency method in such a manner that (i) it includes all significant interactions between the large target and the small features and (ii) it permits the high-frequency and low-frequency methods to be computed separately. The low-frequency method employed is the finite element method (FEM), which is well-known for its capability to model complex geometries and inhomogeneous materials.