Dispersive Periodic Boundary Conditions for Finite-Difference Time-Domain Method

A dispersive periodic boundary condition (DPBC) is developed for the finite-difference time-domain method to analyze periodic structures with dispersive media on the boundaries of a unit cell. The formulation is based on the auxiliary differential equation (ADE) method with a two-term Debye model and the constant horizontal wavenumber approach. The developed formulation is easy to implement and is efficient in both memory usage and computational time. The validity of this formulation is verified through several numerical examples such as infinite dispersive slab and sandwiched composite frequency selective surface (FSS) structure.