Design of Metamaterial-Inspired Wideband Absorber at X-Band Adopting Trumpet Structures

Abstract

This letter presents two types of metamaterial-inspired absorbers adopting resistive trumpet structures at the X band. The unit cell of the first type is composed of a trumpet-shaped resonator loading a chip resistor, a metallic back plane, and a FR4 (<TEX>${\varepsilon}_r=4.4-j0.02$</TEX>) substrate between them (single-layer). The absorption rate is 99.5% at 13.3 GHz. The full width at half maximum (FWHM) is 95 % at 11.2 GHz (from 5.9 to 16.5 GHz). The size of unit cell is <TEX>$5.6{\times}5.6{\times}2.4mm^3$</TEX>. The second type has been optimized with a <TEX>$7{\Omega}$</TEX>/square uniform resistive coating, removing the chip resistors but leading to results comparable to the first type. The proposed absorbers are almost insensitive to polarizations of incident waves due to symmetric geometry.