[Enlarge image]A curved self-accelerated (Airy) THz beam avoids the user’s head to deliver signal to a cell phone.
The adoption of terahertz (THz) bands (above 100 GHz) is widely seen as a critical enabling technology for future wireless communications systems.1 The THz spectrum offers abundant bandwidth for ultrahigh data rates, with experimental sub-THz systems already capable of 1-terabit-per-second performance.2
While point-to-point backhaul THz links are approaching commercial viability, realizing indoor wireless local-area networks (WLANs) remains a much greater challenge. In WLAN scenarios, systems must cope with user mobility and transient blockage events, as most common objects, including users themselves, can obstruct the line of sight and create unreliable communication links. In work published this year, we explored the use of self-accelerated Airy beams to overcome these blockage challenges in THz WLANs.3
At THz frequencies, conventional dipole antenna designs are very small, resulting in tiny effective areas for intercepting incoming signals. The solution is to increase the antenna’s aperture to produce highly directional, pencil-like beams. However, as the aperture size grows, so does the extent of the near-field region. Given submillimeter THz wavelengths, the near field can extend surprisingly far, even with small antenna structures; for example, the 300-GHz near field of a 15-cm aperture can reach 45 m. This raises the prospect that an entire room could be within the near field of a compact access point.
Prior research has highlighted challenges in operating in the near field.4 Our recent work showed how to exploit near-field physics to realize data links that employ near-field wavefronts, such as self-accelerated Airy beams, that can overcome the pervasive challenge of blockage.3 Intriguingly, these beams follow curved trajectories as they propagate in the near field. While Airy beams have been studied in the optics community for years,5 they have been much less explored in the radio frequency range, mainly because such waves do not tend to propagate paraxially along a definite axis. This changes at quasi-optical THz frequencies.
In our research, we experimentally demonstrated the viability of self-accelerated THz beams to carry data around obstacles, showing how to engineer trajectories and perform a link-budget analysis to ensure that sufficient power is delivered to the receiver. We also studied the effect of curvature on bandwidth, and discovered that different frequencies follow different trajectories—a phenomenon distinct from angular dispersion, as it also contains a radial component to the spatial dispersion.
Our findings highlight the capabilities of self-accelerated beams in expanding the range of possibilities in future physical-layer implementations at THz frequencies. We believe that wireless networks operating above 100 GHz stand to gain significant advantages from leveraging the use of such beams in near-field wavefront engineering.
Researchers
Hichem Guerboukha, University of Missouri-Kansas City, Kansas City, MO, USA
Bin Zhao and Edward Knightly, Rice University, Houston, USA
Zhaoji Fang and Daniel M. Mittleman, Brown University, Providence, RI, USA
References
1. J.M. Jornet et al. Nat. Commun. 14, 843 (2023).
2. H. Sasaki et al. IEEE J. Sel. Areas Commun. 42, 1613 (2024).
3. H. Guerboukha et al. Commun. Eng. 3, 58 (2024).
4. V. Petrov et al. Front. Commun. Networks, 4, 1151324 (2023).
5. G.A. Siviloglou et al. Phys. Rev. Lett. 99, 213901 (2007).