An Optically Transparent Broadband High-efficiency Microwave Absorber Using Standing-up Circular Split Rings

In this letter, an optically transparent broadband high-efficiency microwave absorber has been developed. Firstly, the proposed absorber is composed of the indium tin oxide (ITO) films imprinted on a polyethylene terephthalate (PET) layer to guarantee optical transparency. In addition, the structural layer of the absorber consists of two standing-up circular split rings with the same center. Simulated results show that the absorber has 99% absorption bandwidth in the frequency ranging from 4.6 GHz to 9.3 GHz (with the relative absorption bandwidth exceeds 68%). The proposed absorber has good performance in terms of high-efficiency absorption because the design uses a standing-up structure to achieve perfect matching with the impedance of free space. Moreover, the absorption mechanism of the absorber has been investigated through an equivalent circuit model (ECM) and surface current distributions.