Study on ultra-thin dual frequency metamaterial absorber with retrieval of electromagnetic parameters

This paper describes the construction of ultra-thin dual frequency absorbers using metamaterials in microwave frequency (C-band). The geometrical dimensions of an electric field driven LC (ELC) structure are optimized using parametric analysis to achieve absorptions at two distinct frequencies, both in the C-band. The simulation of the proposed structure using HFSS shows that absorption occurs at two different frequencies, viz., 5.64 GHz and 6.22 GHz with absorptivities of 99.4% and 94.8% respectively. The absorption is explained by using the electric and magnetic excitations. The structure is also studied with different polarization and incidence angles. The structure is thereafter fabricated and experimental absorptivity response has been measured showing good agreement with the simulated one. After this, the backside of the structure is slightly modified by applying small cuts so that the transmission properties are little enhanced, and hence the effective constitutive parameters are retrieved. The retrieved effective permittivity and permeability are nearly equal to validate absorption.