Perfect metamaterial absorbers in the ultra-high frequency range

Metamaterial absorbers synthesized by extremely-thin High-Impedance Surfaces (HIS) are analyzed by resorting to a simple transmission line model. The equivalent circuit representation, which takes into account also the high-order Floquet modes effects, allows to interpret the absorption properties of the analyzed structure and to derive closed form relations containing all the degree of freedom involved in the design. By exploiting the guidelines achieved from the circuital analysis, a λ₀/108 thick absorber operating within the UHF RFID frequency band has been designed and tested.