Three-dimensional profiling of collimated radio-frequency orbital angular momentum beams
- Author(s): Joshua K. Hamilton 1, 2 ; Simon J. Berry 2 ; Joseph H. Spencer 2 ; Christopher R. Lawrence 2 ; Francis C. Smith 2 ; Timothy D. Drysdale 3, 4
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View affiliations
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Affiliations:
1:
Department of Physics and Astronomy , University of Exeter , Exeter, Devon EX4 4QL , UK ;
2: QinetiQ Ltd , Cody Technology Park, Farnborough GU14 0LX , UK ;
3: The Open University , Walton Hall, Milton Keynes MK4 2BB , UK ;
4: School of Engineering, Institute for Digital Communications, University of Edinburgh , Edinburgh, Scotland EH9 3FG , UK
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Affiliations:
1:
Department of Physics and Astronomy , University of Exeter , Exeter, Devon EX4 4QL , UK ;
- Source:
Volume 14, Issue 6,
20
May
2020,
p.
547 – 550
DOI: 10.1049/iet-map.2019.0808 , Print ISSN 1751-8725, Online ISSN 1751-8733
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.
Inspec keywords: optical variables measurement; optical links; optical vortices; antenna arrays; laser beams; optical design techniques; angular momentum
Other keywords: dimensional profiling; propagating OAM beam; transmitted OAM beam; xyz scanning stage; OAM mode purity; 180 mm diameter; OAM-carrying beams; size 180.0 mm; collimated radio-frequency orbital angular momentum beams; beam divergence; 8-element circular antenna array; radio communication; orbital angular momentum modes; frequency 4.0 GHz to 6.0 GHz
Subjects: Signal processing and detection; Optical system design; Antenna arrays; Radio links and equipment; Laser beam characteristics and interactions; Free-space optical links; Single antennas; Optical variables measurement
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