Multi-band high-impedance surface absorbers with a single resistive sheet: Circuit theory model

We present a simple and efficient circuit model for the analysis of multi-band absorption characteristics of a stack of sub-wavelength grids (fishnets or patch arrays) in a layered environment with a single resistive sheet placed on top. It is shown that at low frequencies the resonances of total absorption occur, which are explained in terms of Fabry-Pérot resonances associated with the individual reactively loaded dielectric slabs (that are strongly coupled through the sub-wavelength grids). It is observed that the number of absorption peaks in the absorption band corresponds to the number of reactively loaded dielectric slabs. The results of the proposed analytical model are validated with the full-wave simulations, showing good agreement.