Real-time two-dimensional beam steering with gate-tunable materials: a theoretical investigation.

A leaky-wave antenna is proposed that furnishes two-dimensional (2-D) beam scanning in both elevation and azimuth planes via electrical control in real time, and at a single frequency. The structure consists of a graphene sheet on a metal-backed substrate. The 2-D beam-scanning performance is achieved through the proper biasing configuration of graphene. Traditional pixel-by-pixel electrical control makes the biasing network a huge challenge for chip-scale designs in the terahertz regime and beyond. The method presented here enables dynamic control by applying two groups of one-dimensional biasing on the sides of the sheet. They are orthogonal and decoupled, with one group offering monotonic impedance variation along one direction, and the other sinusoidal impedance modulation along the other direction. The conductivity profile of the graphene sheet for a certain radiation angle, realized by applying proper voltage to each pad underneath the sheet, is determined by a holographic technique and can be reconfigured electronically and desirably. Such innovative biasing design makes real-time control of the beam direction and beamwidth simple and highly integrated. The concept is not limited to graphene-based structures, and can be generalized to any available gate-tunable material system.