GOALI: Transparent Beam Steering Antennas Enabled by Graphene Quantum Capacitance Varactors

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The project intends to create a revolutionary transparent beam-steering antenna technology for use in self-driving vehicles. The project utilizes the artificial impedance surface antenna which is ideally suited for integration into automobile window glass due to its low cost and simple design. The key innovation is to utilize the nanomaterial graphene to create a variable capacitance tuning element that can be integrated directly onto the antenna to enable beam steering while maintaining high performance and transparency. This work will lead to a new fundamental understanding of both the performance limits of graphene varactors as well as the novel antenna design and operation. It will provide new understanding of the frequency limits of graphene devices, and could open the door to new design concepts for transparent, steerable antennas. The project will also advance a technology of vital national importance that has the potential to minimize traffic-related deaths, reduce greenhouse gas emissions, enable unprecedented mobility for vision-impaired individuals, reduce traffic congestion, and improve business productivity. The project will also provide an ideal platform for outreach activities, with the industrial interaction providing a natural means to educate graduate students on the automotive applications of millimeter-wave components. This program will also aid in the incorporation of graphene into the undergraduate electrical engineering curriculum at Minnesota, and provides an excellent example of a cross-disciplinary problem, incorporating aspects of solid-state devices and electromagnetism. In addition, K-12 educational programs will be developed that include graphene-based hands-on activities as well as information about self-driving vehicles and automobile safety.This project will explore the creation of a transformative technology where graphene variable capacitors (varactors) are directly integrated onto artificial impedance surfaces to enable beam steering antennas operating at millimeter-wave frequencies. The project integrates two technologies that, to date, had not been previously combined: (1) artificial impedance surface antennas which have great potential for low cost and beam steering capabilities due to their simple design and (2) graphene varactors, which provide an elegant method to incorporate tuning elements for beam steering and are also transparent. The research scope and methods include the following aspects. A new fabrication process for short-channel-length graphene varactors will be developed to enable high-speed operation at millimeter-wave frequencies. A process will also be developed to monolithically integrate graphene varactors with artificial impedance surface antennas to create steerable antennas. Finally, transparent antennas will be fabricated and characterized using a metal meshing strategy and their performance will be compared to opaque antennas. The intellectual significance of this project is that it will lead to a fundamental understanding of high-speed graphene device and antenna technology. It will explore the performance limits of graphene varactors at millimeter-wave frequencies, and advance the technology with wider tuning range, higher quality factor, and improved uniformity. A new integrated platform for beam steering antennas at millimeter-wave frequencies will be created, with the potential for enhanced performance compared to conventional approaches and a path toward practical implementation in autonomous vehicles.