Equivalent Circuit Model for the Frequency-Selective Surface Embedded in a Layer With Constant Conductivity

In this paper, an equivalent circuit model for a frequency-selective surface (FSS) embedded in a layer with constant conductivity is proposed and investigated. Because the medium surrounding the FSS is lossy, the equivalent model consists of not only inductance and capacitance elements but also resistive elements. The reflection response of a square patch FSS embedded in the conductive slab is simulated in a wideband of frequency. Then, all circuit elements are extracted by genetic algorithm optimization, when the reflection coefficient achieved from the equivalent circuit model is the same as the one obtained by numerical simulation. It is also found that the behavior of the model is consistent with that of the simulated one with a good accuracy. Values of the model elements are plotted by the variation of the conductivity and permittivity of layer, and the effects of these parameters are studied on the values of circuit elements. Moreover, it is shown that the obtained model can be applied to determine the model of FSS used in practical absorbers.