Low Reflection Macromodels for a Stable FDTD Scheme Operating with Highly Refined Local Meshes

We propose a new technique of incorporating macromodels into the Finite Difference Time Domain (FDTD) analysis. The technique involves combining grids with drastically different mesh densities and relies on a new interpolation algorithm which guarantees that macromodels incorporated into a standard FDTD scheme are both stable and do not cause reflections that decrease the accuracy. The proposed algorithm gives high accuracy and allows one to locally increase the grid resolution up to several orders of magnitude without significant time step reduction as illustrated on analyzed examples.