Quasi-Optical Multi-Beam Antenna Technologies for B5G and 6G mmWave and THz Networks: A Review

Abstract

Multi-beam antennas are critical components in future terrestrial and non-terrestrial wireless communications networks. The multiple beams produced by these antennas will enable dynamic networking of various terrestrial, airborne and space-borne network nodes. As the operating frequency increases to the high millimeter wave (mmWave) and terahertz (THz) bands for beyond 5G (B5G) and sixth-generation (6G) systems, quasi-optical techniques are expected to become dominant in the design of high gain multibeam antennas. This paper presents a timely overview of the mainstream quasi-optical techniques employed in current and future multi-beam antennas. Their operating principles and design techniques along with those of various quasi-optical beamformers are presented. These include both conventional and advanced lens and reflector based configurations to realize high gain multiple beams at low cost and in small form factors. New research challenges and industry trends in the field, such as planar lenses based on transformation optics and metasurface-based transmitarrays, are discussed to foster further innovations in the microwave and antenna research community.

Wideband Reflectarrays for 5G/6G: A Survey

“…In addition, mobile terminals such as trains or airplanes that have high velocity poses a real challenge in terms of base stations or user demand tracking in order to meet and adapt to diverse 5G/6G traffic [8]. Therefore, beam steering and beamforming antenna architectures are inseparable design requirement of 5G/6G communication systems [5]. Furthermore, adaptive beamforming and steer-ability are required to accommodate rapidly time-varying traffic as well as the on-demand beam coverage due to the spatial evolution of the users [9].…”

“…To meet these demands, 5G/6G technologies require migration to higher frequency bands such as mm-Wave for 5G and up to 1 THz for 6G. In addition, 6G applications might be benefited by migrating from a fixed to a dynamic spectrum allocation [5].…”

Design of a Rotman Lens Operating in the Full K/Ka Band Using Ridge Waveguide Technology

“…The design of the corresponding beam forming networks (BFNs) is particularly challenging for millimetre-waves, as they become more inefficient and complex with the increase of the operation frequency and aperture size relative to the wavelength in order to compensate for higher propagation losses. For these reasons, quasi-optical beamforming solutions are considered well suited for higher frequencies [4]. In particular, the Rotman lens (RL) [5], as a true time delay BFN, offers a combination of broadband operation with low-cost, compactness and wide-angle beam steering.…”

Space-squeezing optics in the microwave spectral region

“…The issue of size becomes even more prominent at longer wavelengths in so-called quasi-optical systems common to the terahertz [1], millimetre-wave [2] and microwave domains [3]. In this regime, free-space diffraction is fundamental to the operation of antennas [4][5][6][7] and beam waveguides [8], and this can lead to very large optical systems [9].…”