Optically Transparent Antennas and Filters: A Smart City Concept to Alleviate Infrastructure and Network Capacity Challenges

This article discusses challenges in designing optically transparent antennas and filters for smart city applications. The smart city concept seeks to alleviate urban challenges that include infrastructure and network capacity. The proposed frequencies for the next generation of wireless networks (5G) would result in shorter broadcast distances and network dead zones. Additional access points and signal repeaters embedded into the existing infrastructure, by inserting transparent antennas into windows via either meshed conductors or transparent conductive oxides (TCOs), would help to mitigate these issues. Glass-embedded frequency-selective surfaces (FSSs) can be used anywhere that requires microwave filtering and optical transparency. The cyberphysical system security in this forthcoming network also poses challenges to entities that require strict network security. This article focuses mainly on TCOs, particularly doped zinc oxide (ZnO), as promising material for transparent antennas and filters. To demonstrate the potential of ZnOs as highly transparent conductive materials for antenna and filter applications, we designed, fabricated, and tested a gallium-doped ZnO- (GZO) based optically transparent 2.4-GHz Wi-Fi antenna and two FSSs (bandpass and bandstop filters) operating in the 23-29-GHz frequency range. These results confirm the potential for ZnO-based TCOs as suitable alternatives to indium tin oxide (ITO) for microwave applications.