Systematic Cell-by-Cell FDTD Subgridding in 3-D

The finite-element-based subgridding algorithm for the 3-D finite-difference time-domain method proposed by Chilton and Lee is shown to be closely related to the finite integration technique. This new insight permits the straightforward derivation of coupling coefficients for complex configurations without the need for arduous finite-element preprocessing. The result is a flexible cell-by-cell subgridding algorithm that allows different refinement ratios without buffer zone and that preserves highly desired physical conservation properties on the discrete level. Its accuracy is validated by the S-parameter analysis of a rectangular waveguide with a ridge discontinuity.