An Investigation on Compact Ultra-Thin Triple Band Polarization Independent Metamaterial Absorber for Microwave Frequency Applications

Abstract

This article claims, an investigation on compact ultrathin triple band polarization independent metamaterial absorber for microwave frequency applications. The proposed absorber unit cell consist of two resonators named as Structure-A and Structure-B. Both the resonators are printed on the upper surface of dual side copper coated FR-4 epoxy glass substrate of thickness 0.8 mm. The proposed absorber structure offers three distinct absorption peaks of 99.67%, 99.48%, and 99.42% with FWHM bandwidth of 170 MHz (4.11-4.28 GHz), 350 MHz (9.17–9.52 GHz), and 480 MHz (11.24–11.72 GHz) at 4.19 GHz, 9.34 GHz, and 11.48 GHz, respectively, under normal incidence. In addition to above, the four fold symmetry of proposed absorber structure make it polarization independent. Proposed absorber structure also offers more than 80% absorptivity at different angle of incidence (up to 60°) under transvers electric and transvers magnetic polarization states. The designed absorber unit cell has compactness of $0.11~\lambda _{0} \times 0.11~\lambda _{0}$ with ultra-thin thickness of $0.0111~\lambda _{0}$ , where $\lambda _{0}$ is the free space wavelength with respect to the lowest absorption peak of 4.19 GHz. Absorption mechanism of proposed unit cell has been discussed with the help of normalized input impedance, electric field distribution, and surface current density plots. In order to discuss the metamaterial property of proposed absorber unit cell dispersion diagram has been shown.