Abstract
We theoretically and experimentally proposed a new structure of ultra-wideband and thin perfect metamaterial absorber loaded with lumped resistances. The thin absorber was composed of four dielectric layers, the metallic double split ring resonators (MDSRR) microstructures and a set of lumped resistors. The mechanism of the ultra-wideband absorption was analyzed and parametric study was also carried out to achieve ultra-wideband operation. The features of ultra-wideband, polarization-insensitivity, and angle-immune absorption were systematically characterized by the angular absorption spectrum, the near electric-field, the surface current distributions and dielectric and ohmic losses. Numerical results show that the proposed metamaterial absorber achieved perfect absorption with absorptivity larger than 80% at the normal incidences within 4.52~25.42 GHz (an absolute bandwidth of 20.9GHz), corresponding to a fractional bandwidth of 139.6%. For verification, a thin metamaterial absorber was implemented using the common printed circuit board method and then measured in a microwave anechoic chamber. Numerical and experimental results agreed well with each other and verified the desired polarization-insensitive ultra-wideband perfect absorption.
Highlights
As an artificially engineered material, metamaterial has attracted significant interest because it exhibited fantastic electromagnetic properties unusual or difficult to obtain over the last decade [1–3]
The metallic split ring resonator-I (SRR-I) and split ring resonator-II (SRR-II) are respectively on the third and bottom substrate which make up the second metallic DSRR (S-metallic double split ring resonators (MDSRR)) microstructure
The angular absorption spectrum, surface current, and near electric-field distributions were explored to validate the excellent characteristics of the proposed perfect metamaterial absorber with strong coupling effects
Summary
As an artificially engineered material, metamaterial has attracted significant interest because it exhibited fantastic electromagnetic properties unusual or difficult to obtain over the last decade [1–3]. The perfect metamaterial absorber (PMA) with ultrathin profile and near-unity absorption was firstly proposed by Landy et al [6]. Metamaterial absorber, which offers great benefits of thin profile, further miniaturization, increased effectiveness, and wider. To increase the absorption bandwidth, several methods such as by using the multi-resonance mechanism [27–38], the fractal structures [39], the multilayer [40–44], the magnetic medium [45, 46], and loading the lumped elements [47–49] have been proposed in the design of gigahertz and terahertz metamaterial absorbers. A broadband polarization-insensitive perfect absorber exhibiting a bandwidth of 9.25 GHz has been designed in a single layer based on the double octagonal-ring metamaterials and lumped resistances. A gigahertz perfect metamaterial-inspired absorber was proposed which was composed of three-layer substrates, double split-serration-rings, and a metal ground [51]. A relative bandwidth of 93.5% was obtained, the absorption bandwidth is still insufficient for applications, such as electromagnetic protection, stealth, and electronic warfare
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