Indium-Tin-Oxide-Based Broadband Optically Transparent Reflectarray Antenna Using a Multilayer Hybrid Dielectric Substrate and Heterogeneous Elements
Longzhu Cai, Jiaqi Zhou, Haobin Hu, Xin Xu, Zhi Hao Jiang, Wei Hong
Abstract
In this communication, an optically transparent reflectarray antenna based on indium tin oxide (ITO) material is presented. The reflectarray is composed of a patterned ITO array, two quartz glass substrates, and an ITO ground. By introducing an air gap between the quartz glass substrates, a multilayer hybrid dielectric substrate is formed, reducing the high conductor loss of the ITO material. The heterogeneous single- and combined-resonance elements are jointly utilized to achieve a wider phase variation. At the center frequency of 20 GHz, the reflectarray element owns a reflection loss of less than 1.8 dB and a phase variation of 494°. For verification, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15\times15$ </tex-math></inline-formula> -element optically transparent reflectarray with a focus-to-diameter (F/D) ratio of 0.9 is designed, simulated, and measured. The measured results demonstrate good radiation characteristics, showing a measured gain of 24.4 dBi, a 1.5-dB gain bandwidth of 20%, and an overall optical transmittance of 75%. Compared with previously reported ITO-based transparent reflectarrays, this design achieves a wide phase variation, high optical transparency, low return loss, and broad bandwidth simultaneously.