Design of an optically-transparent ultra-broadband microwave absorber

Abstract

The optical window of the low-observable platform needs to be compatible with ultra-broadband absorption, hence an optically-transparent absorber with ultra-broadband absorption is designed and analyzed in this paper. The transparent materials indium-tin-oxide (ITO) film and polymethylmethacrylate (PMMA) are selected as the lossy layer and the supporting dielectric layer, respectively. The optically-transparent ultra-broadband absorber (OT-UBA) is composed of three layers of ITO square patterns, three layers of PMMA dielectric and a uniform ITO plane. The ITO square patterns can realize arbitrary equivalent series RC (resistor & capacitor) circuit, so that three layers of ITO square patterns together with the ITO plane can achieve ultra-broadband absorption based on the equivalent circuit optimization. Measured results shows that the 90%-absorption bandwidth covers 2-17 GHz while the light transmittance achieves 59.6% with the total thickness of only 12.9 mm.