Broadband and Omnidirectionally Matched Absorber for a Discrete Source

Abstract

Achieving an omnidirectionally matched absorption in a broad frequency band is of particular interest in electromagnetic (EM) compatibility and shielding. Conventional absorbers used to work for a far-field incidence with a predefined direction, which do not show flexibility in practical applications involving various wave incidences. Here, we investigate the absorption performance of an inhomogeneous anisotropic slab for a given discrete source and show that an omnidirectionally matched absorption can be rendered, provided that the complex constitutive parameters of the slab obey a specific spatial profile. This specific profile guarantees that the wave impinging on each small grid of the slab will be absorbed without interface reflection, relying on the impedance matching nature of the Brewster’s effect. As a proof of concept, we implement a lumped-resistor-loaded gradient planar absorber, whose constitutive parameters fulfill the desired spatial profile in a broad frequency band. Both full-wave simulations and experimental measurements validate the results. The presented design methodology is simple, robust, and scalable to any other frequencies. Our work provides a novel solution to realize ideal EM shielding for discrete sources, which may be useful in practical scenes with given EM sources.