A novel subgridding scheme based on a combination of the finite-element and finite-difference time-domain methods

A simple and versatile local mesh refinement scheme, based on the hybridization of the finite-element (FE) and the finite-difference time-domain (FDTD) algorithms, is presented. The scheme achieves considerable flexibility in subgridding by using a transition region between the coarse and fine FDTD grids, meshed according to an unstructured grid, and solved by means of the FE method in the TD. An interpolation scheme in the time domain, which allows the use of different time steps in the coarse and fine mesh regions, is included in the paper.