A Conformal Thin Boundary Model for FDTD

Thin layer models are widely used in the finitedifference time-domain (FDTD) technique to efficiently model boundaries in multi-scale simulations as they significantly reduce simulation run-times and memory requirements. These models often utilise surface impedance boundary conditions (SIBCs) to represent the material of the boundary. Conformal meshes are a popular method of representing curved and non-aligned surfaces in FDTD. These meshes deform cells in the FDTD grid around the boundary between bulk materials so as to more accurately represent the shape of the material. Here we present an algorithm that combines the efficiency of a thin layer model with the accuracy of a conformal mesh. The algorithm is applied to three resonant cavity models and the accuracy verified using comparisons to non-conformal meshes and analytic solutions. Improvements are shown in the accuracy of the resonant frequencies and magnitude of the shielding effectiveness (SE) of the cavities. It is also shown to reduce the prevalence of extraneous features in the frequency response of the SE that are apparent when using a stair-cased mesh.