Compact Quad-Band Polarization-Insensitive Ultrathin Metamaterial Absorber With Wide Angle Stability

In this letter, a compact ultrathin quad-band polarization-insensitive metamaterial absorber with a wide angle of absorption is proposed. The unit cell of the proposed structure comprises conductive cross dipoles loaded with split-ring resonators. The proposed absorber exhibits simulated peak absorption of 96.15%, 99.17%, 99.75%, and 98.75% at 3.68, 8.58, 10.17, and 14.93 GHz, respectively. The proposed multiband absorber is ultrathin and compact in configuration with a thickness of 0.0122 λ and a unit cell size of 0.122 λ (corresponding to the lowest frequency). Moreover, by understanding the interaction of the unit cell with incident electromagnetic radiation, a conceptual equivalent circuit model is developed, which is used to understand the influence of coupling on the quad band of absorption. The simulated response of the proposed design demonstrates that it has quad-band polarization-insensitive absorption characteristics. In addition, the proposed absorber shows high absorption for an oblique incidence angle up to 60° for both transverse-electric and transverse-magnetic polarizations.