Design and Characterization of an Ultrabroadband Metamaterial Microwave Absorber

Abstract

This paper presents the design, simulation, fabrication, and performance of an ultrabroadband metamaterial absorber (MMA) at microwave frequencies. The unit cell of this design is composed of the combined metallic resonance structure of two overlapping squares, as well as a square split-ring at the top of an FR-4 dielectric layer and a continuous copper ground plane. The simulated results derived from CST2015 indicate that the absorption ratio of the MMA is over 83%, with a wide frequency range from 20.59 to 43.73 GHZ for a normal incidence electromagnetic (EM) wave. The proposed ultrabroadband MMA has a full width at half maximum (FWHM) absorption bandwidth of 25.64 GHZ and a relative FWHM absorption bandwidth of 79.5%. Moreover, the absorber has a thickness of 0.92 mm, which is only 0.1 λ0 at the center frequency of 32.17 GHZ. The effects on the absorption properties produced by the materials' properties and polarization angles have been investigated. The electric field and surface current distributions have been analyzed at three absorption peaks to understand the EM wave absorption mechanism. The proposed absorber has been fabricated using the laser ablation machine and tested for the normal incidence EM wave. Measured results show an agreement with the simulated results. Furthermore, the proposed design can greatly enrich the applications of MM in thermal imaging, detection, stealth technology, antenna systems, and other EM devices because of its broad frequency range, high absorption, simple fabrication, and effective cost.