An angularly stable and optically transparent broadband conformal microwave absorber using “diamond-shaped” pattern

Abstract

The emergence of metamaterials provides a novel solution to realize high-performance optically transparent electromagnetic (EM) absorber. In this paper, an optically transparent metamaterial-based microwave absorber, which features wide operating bandwidth and angular stability, is presented both numerically and experimentally. The proposed structure is mainly composed of a transparent indium-tin-oxide (ITO) “diamond-shaped” pattern layer and a polyethylene terephthalate (PET) substrate layer. By employing the polyvinyl chloride (PVC) compensation layer with appropriate thickness, we improve the broadband impedance matching with free space. Since we use flexible conductors and dielectrics, the absorber is able to adhere closely to the object. According to the spectrometer measurements, the proposed absorber achieves an averagely high transmittance of 70.2% in the visible band. The fitness of numerical simulations and microwave measurements demonstrate that the absorption exceeds 90% in an ultra-broadband operating frequency from 8.02 to 33.91 GHz (corresponding to 123.5% fractional bandwidth) is achieved. Besides, it also demonstrates excellent absorption performance for wide-angle oblique incidence waves approaching 45°. Finally, the absorber with conformal configuration which can effectively suppresses the backscattering of the arched metal surface in the considered broadband frequency range from 8 to 32.05 GHz is also realized. The proposed wide-angle and optically transparent broadband absorber can be utilized in specific engineering scenarios, such as aircraft cockpit and solar panel.