Compact Log-Periodic Single-Port Planar Antennas for D-band Monolithic RIS Panels

• Published in: IEEE antennas and wireless propagation letters 2024-10, p.1-5
• Main Authors: Shurakov, Alexander, Razakova, Anita, Lvov, Andrey, Belikov, Ivan, Prikhodko, Anatoliy, Goltsman, Gregory
• Format: Article
• Language: English
• Subjects: 6G mobile communication; Antennas; Beam steering; Capacitance; D-band; Geometry; log-periodic spiral; planar reflectarray; reconfigurable intelligent surface; Reconfigurable intelligent surfaces; Reflection; Reflector antennas; Schottky diodes; single-port antenna; Spirals
• ISSN: 1536-1225; 1548-5757
• DOI: 10.1109/LAWP.2024.3484756

The quality of wireless connections in the sixth generation (6G) communication networks is tightly linked to the capabilities of smart antenna environments. They should enable effective routing of ultra-narrow radio beams, intrinsic to D-band channels, and make use of so-called reconfigurable intelligent surfaces (RISs). Practical RISs are seriously judged by their cost and operation efficiencies. In this paper, we report on the development of a robust single-port antenna that can be used as part of a D-band RIS panel. The antenna is presented by a grounded log-periodic spiral on thin quartz substrate. Two types of spirals are developed for either a static beamforming or dynamic beam steering in reflected light. The geometry- and load-controlled phase shifts consistently cover a 0-350^\circ range upon reflection of 140 GHz waves with the angles of incidence within \pm 75^\circ. This is achieved by changing either i) the spiral scaling factor between 0.658 and 1 in half-wave cells or ii) the spiral load capacitance between 0 fF and 20 fF in quarter-wave cells. These values are feasible for GaAs-on-quartz planar Schottky diodes. The simulation results are justified by prototyping. For a 1.3k pixel proof-of-concept reflectarray with geometrically phase-configured cells, we measure the beamwidth, side lobe and cross-polarization levels of 4^\circ, -13 dB and -26 dB, respectively. All together suggests great potential of the developed antennas as basic elements for the physical layer devices of reflection-aided 6G wireless communications.