Equivalent circuit modeling of an ultra-thin dual-band microwave metamaterial absorber

This paper presents the equivalent circuit modeling of an ultra-thin microwave metamaterial absorber comprising two concentric closed ring resonator (CRR) structures. The dimension of the unit cell as well as the other geometrical parameters like radii and widths of the rings are optimized so that absorptions take place at two distinct frequencies near to the middle of the FCC radar frequency spectrum. The proposed structure shows peak absorptivities of 93.4% and 99.6% at 5.50 GHz and 9.52 GHz respectively. The equivalent circuit of each CRR is proposed and the overall circuit model is developed accordingly. The simulation of the proposed equivalent circuit agrees well with the numerical simulation, thus validating the modeling. The structure is also fabricated whose results match closely.