Passive and Active Metasurface-Enabled Mm-wave Antenna Systems

Mm-wave antennas are beginning to find marketplace applications in cutting-edge technological systems. The worldwide deployment of the 5G communications standard induces great need for mm-wave antennas both in cellular phones and in base stations. The smart car initiative requires high-performance radar sensing systems built from highly directive and steerable mm-wave antennas or antenna arrays. The proliferation of the Internet of Things greatly increases the need for small, lightweight and cost-effective antennas, which can be used on various wirelessly connected, mobile and/or wearable devices. Next generation mm-wave antennas can greatly benefit the aforementioned fields and many others.To a degree, the design of mm-wave antenna systems can be facilitated by upscaling established antenna system designs from lower frequencies. However, one faces challenges such as more stringent fabrication requirements and different material responses (in particular an increase in material loss) at higher frequencies. Traditional phased array antenna systems – which find great use in high-directivity and long distance communications – become expensive when they are scaled to mm-wave frequencies, because of the expansive cost for phase shifters at high frequencies, and because a very large number of phase shifters are needed for a mm-wave phased array. To alleviate many of the aforementioned difficulties, we propose to conduct research towards the design of mm-wave antenna systems enabled by passive and active metasurfaces.Recent works on the metasurface have demonstrated its merit as a highly flexible electromagnetic wave manipulation surface. Specifically, it can be lightweight, cost effective, and yet can be used to facilitated many antenna-related functions, like beam collimation, scanning, focusing and radiation to extreme angles. While the theoretical groundwork is largely laid, most prior works on metasurfaces have been at the microwave (low GHz) and optical frequencies, leaving the mm-wave regime, with its unique challenges and opportunities, relatively unexplored. In this regard, a recent work by the PI showed that an active metasurface can be tuned to generate an arbitrary waveform within an enclosed region of space. Preliminary results show that a minor modification can turn this device into a travelling-wave antenna which boasts a large beam steering range and a dramatic reduction in the amount of tuning elements required. The PIs’ expertise in metasurface and antenna design and the advanced fabrication and characterization facilities at the State Key Laboratory of Terahertz and Millimeter Waves at the City University of Hong Kong make this team uniquely positioned to succeed in the proposed research.