A Beam-Steering Solution With Highly Transmitting Hybrid Metasurfaces and Circularly Polarized High-Gain Radial-Line Slot Array Antennas

• Published in: IEEE transactions on antennas and propagation 2022-01, Vol.70 (1), p.365-377
• Main Authors: Afzal, Muhammad U., Esselle, Karu P., Koli, Mst Nishat Yasmin
• Format: Article
• Language: English
• Subjects: Antenna arrays; Antennas; Aperture field; Beam steering; Circular polarization; circularly polarized (CP); communication on the move (COTM); consumer terminal; Continuous beams; Dielectrics; Elevation angle; flat lens; flat panel; frequency-selective surface (FSS); geostationary orbit (GEO); High gain; lens antenna; low earth orbit (LEO); Luneburg; medium earth orbit (MEO); Metals; Metasurfaces; Near fields; phase shifting surface; phase transformation; Power consumption; Power management; prisms; Prototypes; radial-line slot array (RLSA); reconfigurable antenna; reflectarray; Reflector antennas; Risley; SATCOM; satellite on the move (SOTM); satellite terminal; satellite tracking; Slot antennas; space Internet; Transmission; transmitarray; Transmitting antennas
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2021.3111522

A continuous beam-steering solution for circularly polarized (CP) radial-line slot array (RLSA) antennas is presented and demonstrated with a fabricated prototype. The solution is based on the near-field meta-steering (NFMS) method, which is implemented through a pair of highly transmitting hybrid metasurfaces (HMs) that are placed above a high-gain CP RLSA antenna in the near-field region. Cells in HMs, unlike conventional metasurfaces (CMs), can provide exact or close to exact phase shift with transmission magnitude larger than −1 dB. This is achieved by combining the nonoverlapping phase ranges of two dramatically different phase-shifting cells. The RLSA is stationary, while the two HMs are rotated to steer the beam in a 2-D (azimuth and elevation) space. The measured results of the prototype demonstrate that the system can steer its beam to a maximum elevation angle of 40.6° with a maximum gain of 30.9 dBic. The axial ratio remained less than 3 dB in the 3 dB beamwidth even when the beam is steered. The height of the system is only 4.5 cm, which is much less than mechanically steered reflector antennas. Unlike electronically steered high-gain antenna arrays, this system requires only few watts of power only when rotating HMs and has zero power consumption when the beam is stationary.