2-D Fixed-Frequency Terahertz Beam Steering With Microactuated Leaky-Wave Structure

As the demand for high-speed communications grows, terahertz waves emerge as a promising frontier for 6G and beyond, offering unprecedented bandwidths. However, their shorter wavelengths result in significantly higher diffraction losses compared to microwaves, necessitating innovative solutions for directional beam steering to counteract these losses. Conventional large-aperture phased arrays face challenges at terahertz frequencies due to the lack of practical phase shifters. To address this challenge, this study introduces a novel 2-D beam steering technique employing a microdisplacement controlled leaky-wave structure. By exploiting the dispersion relation of waves propagating between quasiparallel metal plates, we effectively manipulate the wave trajectory and launch angle via precise displacement and tilt of the plates. Our experimental demonstration achieves effective 2-D terahertz beam steering, eliminating the need for frequency sweeping. At 280 GHz, we achieve a steering range of ${\bf \pm \! 37^{\circ }}$ horizontally with a plate tilt of ${\bf \pm 0.169^\circ }$ and ${\bf 18^{\circ }}$ vertically with a plate translation of 0.2 mm, along with a 3 dB frequency bandwidth of 9.7 GHz and a 10 dB bandwidth of 17.3 GHz. This method not only circumvents the limitations posed by the lack of phase shifters but also facilitates integration into compact, planar systems without expanding the physical profile. This result paves the way for directionally agile terahertz communications, enabling real-time user and device tracking capabilities.

I. Introduction

Wireless communication using terahertz waves is promising for meeting the increasing data capacity demands of the beyond 5G/6G paradigm [1]. However, the Friis transmission formula indicates that received power decreases inversely with the square of the frequency [2], leading to significantly higher path loss for terahertz waves compared to microwaves. To counteract this path loss, employing beamforming with high-gain antennas is essential in terahertz applications, where achieving a gain of 30 dB often requires aperture sizes on the order of centimeters [3].