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

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.