Ultra-Wideband Polarization Insensitive Thin Absorber Based on Resistive Concentric Circular Rings

Abstract

Eliminating stray and suppressing unwanted radiation in a high frequency circuit is difficult. It becomes a challenge to achieve an ultra-wide absorption band in a thin-single-layer microwave absorber. In this article, a novel polarization-independent, ultra-wideband, light-weight, thin microwave absorber has been investigated numerically and experimentally. The proposed absorber unit cell consists of two concentric circular rings loaded with lumped resistances placed on top surface of a dielectric substrate. Unit cell size is 0.28 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> * 0.28 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> * 0.067 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> , which is compact in configuration (where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> is the wavelength corresponding to lowest frequency of operation). The proposed design provides more than 90% absorption in the frequency range of 6.7 GHz to 20.58 GHz (fractional bandwidth of 101.7%). The novelty of the proposed work lies in designing a wideband and ultra-thin absorber by using optimum unit cell geometry, resistance loading, and air column loading. Combination of these techniques results in a very wide band absorber design. Four fold structural symmetricity makes the absorber polarization insensitive. The absorber is compact, light-weight (used air as spacer), and thin (only 0.067 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> thick) and provides an alternative to construct wideband absorber for electromagnetic interference reduction.