Subgridding with domain overriding for FDTD

The numerical simulation of electromagnetic problems often requires the use of meshes of varying sizes to capture fine geometric details locally, especially when it is computationally prohibitive to use an overall fine grid. This strategy, when based upon structured meshes, is often referred to as subgridding. We present a new methodology based on overlapped grids and domain overriding to study and optimize the reflection properties and stability of subgridding schemes. We override the subgridding region using embedded perfectly matched layers (PML) to control the direction of wave propagation. We show that subgridded interfaces have reflection properties which are analogous to the reflection of the embedded PMLs, thus it is explicitly controllable by changing the PML parameters.