FDTD local grid with material traverse

Often, a finite-difference time-domain (FDTD) calculation requires a relatively higher mesh resolution in only small subvolumes of the total mesh space, By locally applying finer grids (local grids) to these volumes, the necessary resolution can be obtained, Computation time and memory requirements may be far less than for an FDTD space with the smaller mesh resolution throughout, In many situations, it is important that these local-grids function when materials traverse the main-grid-local-grid (MG-LG) boundary surfaces, since the volumes that require local grids may not be isolated in a homogeneous medium, In this paper, a local-grid method, which allows dielectric and/or conducting materials to traverse the boundaries, is developed, Three different FDTD problems that utilize the local-grid method are used as validation tests, Results are compared with uniform mesh FDTD solutions.