An approach for circuit modeling of a multiband resonators based planar metamaterial absorber

In this article, a metamaterial absorber structure is analyzed using the transmission line method (TLM) considering the normal incidence of the wave. The unit cell of the presented absorber structure is a composite geometry providing dual-band absorption. Peak absorptivities of 95.02% and 99.84% are obtained at 4.215 GHz and 10.95 GHz, respectively. The experimentally validated simulated reflection response is used as a reference to validate the analytical response of the absorber structure. To obtain the equivalent circuit model, the frequency selective surface (FSS) forming the absorber top layer is considered as a combination of two simpler FSS. The individual absorbers formed by two such FSS are correctly modeled using TLM. The obtained equivalent circuits are then combined suitably by incorporating the involved coupling capacitances into the calculation. The analytical and simulated response of the presented absorber structure is found in good agreement. The presented decomposition approach for the development of a circuit model of the composite FSS is promising and it would pave the way in obtaining the good physical insight of the multiband metamaterial absorber structures.