Finite-difference time-domain modeling of frequency selective surfaces using impedance sheet conditions

Novel finite-difference time-domain (FDTD) models of frequency-selective surfaces (FSS) based on impedance sheet conditions are developed. The analytical basis of the models lies in impedance sheet conditions with general reactive grid impedances applying to a great variety of grid realizations. New models for periodic arrays of metal particles and for the complementary structures of slots in metal screen are formulated for FDTD in the case of normal incidence. The properties of the FSS are included in the grid impedance, which is implemented into FDTD, considerably simplifying the otherwise extremely cumbersome modeling task. The convergence and the accuracy of the models are assessed with numerical simulations by comparing with analytical and measured reference results.