An Optically Transparent Metantenna for RF Wireless Energy Harvesting

We propose a novel transparent metasurface antenna (metantenna) based on indium tin oxide (ITO) material for simultaneously achieving wireless energy harvesting (WEH) at radio frequency (RF) bands and efficient transmission of visible light. We adopt the design method of aperture-coupled metantenna to realize broadband and low-profile RF WEH. Then, we replace the conventional opaque metal material with an ITO coating with a sheet impedance of
$1~\Omega $
/sq to achieve the transparency of the proposed design. In order to obtain the balance between electrical performance and optical transmittivity (OT), we modify the metasurface structure to further improve the OT of the metantenna. The fabricated transparent metantenna shows an OT of more than 50%. A measured impedance bandwidth of 43.6% from 1.40 to 2.18 GHz is obtained to cover 2G and 3G wireless communication bands. Through designing the broadband rectifying circuit and the energy management circuit, we can obtain the maximum RF-dc efficiency of 65% and a stable dc output voltage of 3.4V, while the overall RF energy harvesting efficiency could reach 14.5% with the power input of 0 dBm. In addition, through the solar energy harvesting test, we can demonstrate the potential of the proposed design to work with solar panels for realizing efficient RF/solar hybrid energy harvesting.