A Thin Electromagnetic Absorber for Wide Incidence Angles and Both Polarizations

TL;DR

This paper presents a planar electromagnetic absorber with wide-angle and polarization-insensitive performance, utilizing high-permittivity substrates and vias to enhance bandwidth and absorption efficiency.

Contribution

It demonstrates the practical use of an additional resonance in high-impedance surfaces caused by wire medium plasma frequency proximity, improving absorber performance.

Findings

High-permittivity substrates are essential for operation.

Vias influence TM absorption at oblique angles.

Proper via design enlarges bandwidth and absorption.

Abstract

In this paper a planar electromagnetic absorber is introduced whose performance is maintained over a wide change of the incidence angle for both TE and TM polarization. The absorber comprises an array of patches over a grounded dielectric slab, with clear advantage in terms of manufacturability. It is shown that a high value of the relative permittivity of the substrate is essential for the operation of the absorber. The main contribution of the paper is to demonstrate and practically use the presence of an additional resonance of high-impedance surfaces when the plasma frequency of the wire medium comprising metallic vias in the dielectric substrate is close to the original resonance of the high-impedance surface. The presence of the vias between FSS and the ground plane is discussed both for the case of a high-permittivity absorber and for a low permittivity one. The radius of the vias influences the oblique incidence TM absorption, and when properly designed, the insertion of the vias result in bandwidth enlargement and higher absorption.