Analysis and design of wire-based metamaterial absorbers using equivalent circuit approach

Wire-based metamaterial absorbers, as a kind of simple but versatile artificial structures, have been widely investigated from microwave to optical frequencies. In order to completely understand how the constitutive parameters affect the absorption properties, an equivalent circuit model is developed in this paper. The analytical, numerical, and experimental results show that the absorption frequency is determined by the wire length and the spacer electromagnetic parameters, whereas the absorption level by the thickness of spacers and losses which include Ohmic loss of the metal as well as dielectric loss of the spacers. It is also explained why the small losses have hardly any effect on the absorption frequency, but can result in the near-unity absorption. Based on the circuit model, some strategies for designing broadband absorbers are discussed finally.