Three dimensional huygens subgridding for FDTD

The 2D HSG algorithm has been generalized to 3D. Experiments have shown that results are as accurate as in the 2D case. The late time stability seems slightly better in 3D than in 2D. And all the advantages of the HSG are preserved in 3D, i.e. large ratio of steps, small reflection from grid interface, same ratios of space and time steps, objects that can traverse the interface. In this paper, two experiments with the 3D Huygens subgridding are reported. The first one with a cavity where the energy penetrates through a thin slot. The second one with a small antenna placed within a subgrid and radiating towards a surrounding coarse grid.