Abstract
A broadband and thin microwave absorber composed of metal-base planar metamaterials (MMs) sandwiched between two layers of flaked-shaped carbonyl iron (FCI) composites is presented. FCI powder was prepared by ball milling spherical carbonyl iron powder and then added to epoxy resin to prepare FCI composite (FCIC) samples with different weight fractions. With these electromagnetic characteristics, a broadband, polarization-insensitive and thin metamaterial absorber comprising of arrays of square spirals embedded between two different layers of FCIC is optimally designed through a genetic algorithm. The reflection loss of the measured square spiral MM absorber with a thickness of 3.4 mm can reach –26 dB at matching frequency 4.4 GHz and the absorbing bandwidth below –9.3 dB is covered from 3.6 to 18.0 GHz which almost 4 fourfold bandwidth compared to that of the FCIC without the incorporation of MM layers.
Highlights
To enhance and modify the absorption properties of magnetic absorbing materials, a microwave absorber composed of planar MM with square spiral patterns which are sandwiched between two layers of FCI composite (FCIC) absorbers is presented in this paper
The real part of complex permittivity (ε′) of all FCIC test samples were almost constant in the frequency range of 218 GHz while the imaginary part of complex permittivity (ε′′) shows frequency dispersion
We have proposed a bandwidth-enhanced and polarization insensitive metamaterial absorber which is composed of two FCIC layers sandwiched with a MM layer etched with square spiral patterns
Summary
Radar absorbing materials (RAMs) known as microwave absorbers, which can absorb and dissipate incident electromagnetic waves by converting them to thermal energy, are widely used in the fields of radar-cross section (RCS) reduction (stealth technology), electromagnetic interference (EMI) shielding for sensitive electronic equipment and human health protection from electromagnetic radiation of wireless devices, mobile phone base stations and broadcast antennas.1 Carbonyl iron powder (CIP) are metallic magnetic materials possessing relatively low electrical conductivity, high Curie temperature, and the high values of permeability due to high saturation magnetization (4πMs) in the gigahertz range.2 Such superior characteristics of CIP have attracted much attention in the use as microwave absorbing fillers which are embedded in an insulating polymer to make an effective composite magnetic absorber for higher frequencies ranging from 2 to 18 GHz. To enhance and modify the absorption properties of magnetic absorbing materials, a microwave absorber composed of planar MM with square spiral patterns which are sandwiched between two layers of FCIC absorbers is presented in this paper.
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