A Triple Band Polarization Independent Metamaterial Absorber for S, C and X-band Applications

This paper asserts an exploration of a compact, ultrathin triple-band metamaterial absorber (MA), which is polarization insensitive. The unit cell structure proposed comprises three different resonating structures, namely structure 1, structure 2, and structure 3. The unit cell structure consists of three layers in which resonating structures are printed on top of substrate material (FR-4), which has a thickness of 1 mm. The bottom layer of dielectric material is circumscribed with a thin layer of copper. Under normal incidence, our proposed structure presents three different absorptivity peaks of 99.89%, 99.85%, and 97.82% for 3.59GHz, 6.82GHz, and 11.96GHz, which have FWHM bandwidth of 157.38MHz (3.513-3.670GHz), 304.89MHz (6.682-6.986GHz), and 629.14MHz (11.658-12.287GHz) respectively in TE mode. The proposed structure is unconstrained on polarization by its four-fold symmetricity property. Our proposed unit cell structure provides the compactness of 0.119λ
0
× 0.119λ
0
, which provides a needle-like thickness of 0.011λ
0
, where λ
0
represents the wavelength of free space regarding the lowest peak of absorptivity at 3.59GHz. The variation of MA parameters: effective input impedance, effective permittivity and effective permeability, are shown against frequency to describe the absorption procedure for the proposed unit cell structure.