Beam-steering capability for OAM-based reflectarray at 5G-mmWave frequencies

The ability of the reflectarray antenna (RA) to perform orbital angular momentum (OAM) beam-steering with low divergence angles at the fifth generation (5G) millimetre-wave (mmWave) bands is demonstrated. To provide steered OAM beams, it is necessary to regulate the scatterer's geometries smoothly throughout the focal area to follow the required twisted distribution. The traditional numerical method to compensate for the phase is modified to enable the 3D scanning property of OAM beams, so it is possible to avoid the feeder blockage and produce high-gain steered OAM beams. Likewise, reducing the inherent beam divergence of OAM beams can be obtained by examining the most satisfactory phase distribution of the scatterers by fitting the focal length. The simulated radiation pattern is validated by the measured radiation pattern of the fabricated RA in the frequency range between 28.5 and 31.5 GHz.