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Hamilton, Joshua K.; Berry, Simon J.; Spencer, Joseph H.; Lawrence, Christopher R.; Smith, Francis C. and Drysdale, Timothy D.
(2020).
DOI: https://doi.org/10.1049/iet-map.2019.0808
Abstract
The use of orbital angular momentum (OAM) modes in radio communication is thought to enhance capacity. This work focuses on using the l = +1 mode transmitted from a 180 mm diameter, 8‐element circular antenna array. The transmitted OAM beam was collimated by using a spherical mirror and the intensity and phase were investigated. A xyz scanning stage was used to profile the propagating OAM beam in three dimensions, resulting in a detailed investigation into the effects of collimation on the OAM beam. The proposed system was shown to reduce the beam divergence from 36.6° to 1.2°, without affecting the OAM mode purity of the beam for a frequency range of 4–6 GHz. This investigation showed a step towards realising practical control over the divergence of OAM‐carrying beams.