FDTD surface impedance model for coated conductors

A new finite-difference time-domain (FDTD) model of dielectric and conductive layers on conductive surfaces is developed. The model is based on surface impedance boundary condition, allowing the coating and the conductive backing to be removed from the computational space. The proposed model extends the previous FDTD models, which are formulated for coatings on perfect electric conductors (PEC), to coatings on more general dielectric and conductive materials. On the other hand, the model can also be regarded as a generalization of models designed for conductors without coatings. The present model accounts for the first thickness resonance of the layer by modeling the singularity of the tangent function appearing in the impedance function. The proposed model is numerically verified for normal incidence in the frequency domain and for varying oblique angles of incidence in the time domain by comparison with analytical results.