Metasurface-based Microwave Absorber

Abstract

Metasurfaces are periodic artificial structures with unique electromagnetic properties. They can be designed to achieve multiple functionalities such as polarization manipulation, beam splitting, RF sensing, spatial filters, gain enhancement of antennas, absorbers, to name a few. In recent years, researchers have published a lot of work on metasurface-based microwave absorbers for application such as micro-bolometers, anechoic chambers, scattering reductions, thermal sensing and energy harvesting. Broadband metamaterial absorbers (MMA) can generally be achieved using multi-layer structures, resistive sheets, or lumped elements; however, such designs become complex and bulky in size. In this perspective, low profile single layer metasurface absorbers have more potential to be employed in different applications. However, single layer absorbers are either narrowband, polarization-sensitive or not angularly stable. In this research thesis, a broadband polarization independent absorption has been tried to achieve with a single layer absorber. The proposed design is based on a metallic super-cell split ring resonators (SRR) printed on FR-4 substrate with metallic ground plane at the bottom. A good absorption rate (>90%) has been achieved over a broadband range of frequencies from 12.687-13.669 GHz achieving a total band of 983 MHz. As per author’s knowledge, this is the highest bandwidth achieved so far with a single layer metasurface without using lumped elements. Another relatively narrow band of 108 MHz has also been achieved within the frequency range of 15.307-15.415 GHz. The design has also been also analyzed for different orientations of the incident electric field and at oblique angles. The absorber exhibits the same response for both TM and TE incidence because of symmetry in the supercell structure.