Low-reflection subgridding

The paper presents a novel three-dimensional subgridding scheme applicable to the finite-difference technique in the time and frequency domains. Transfer of fields between a main grid and a refined volume is performed using a simple linear interpolation. Very low-reflection levels from the main to local grid interface are obtained by co-location of fields used in the interpolation process. The technique allows material traverse without any special boundary treatment. The accuracy of the scheme is verified in numerical tests showing excellent performance even for high refinement factors.