Modified subgridding algorithm with multilevel scheme for two-dimensional finite-difference time-domain method

Finite-difference time-domain method (FDTD) has been very popular in solving electromagnetic problems. However, for those that contain small structures or strongly varying fields, very fine meshes have to be used. Since a finer mesh means longer computing time and larger memory, subgridding would be one of the ways to improve the performance of the FDTD method. To expand the power of subgridding, we develop a multilevel subgridding scheme. This new scheme can provide smoother transitions than the conventional one-level subgridding scheme, and achieve better performance.