Dispersive terahertz metasurface fed by a horn antenna for highly oriented 2D beam steering

Highly oriented beam steering will enhance power density and field of view (FOV) in terahertz wireless links. Metasurface can be constructed by deliberate arrangement of subwavelength meta-cells to manipulate the wavefront. This paper explores a dispersive metasurface with a specific phase gradient patterned in a 2-inch aperture, allowing for collimated beamforming and two-dimensional (2D) beam steering by a combination of frequency tuning and metasurface rotation. The metasurface is directly fed by a horn antenna, ensuring a compact integration. Simulation and experiment in the 80-110 GHz band revealed that the gain band crucial for FOV and efficiency is mainly constrained by the nonlinear phase dispersion of the meta-cells. Efforts to optimize the phase linearity resulted in a more efficient metasurface with a gain of 35.7 dBi and an efficiency of 76.6% at 400 GHz. A FOV of 22.5° in the elevation was guaranteed with gain in the 325-500 GHz band (a bandwidth of 42.4%). Imaging of two scattering balls was demonstrated at a distance of 4.1 meters by using the metasurface for 2D beam steering.