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.

中文翻译：

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准直射频轨道角动量光束的三维轮廓

在无线电通信中使用轨道角动量（OAM）模式被认为可以增强容量。这项工作着重于使用升= +1模式是从直径为180 mm的8元素圆形天线阵列发送的。使用球面镜对透射的OAM光束进行准直，并研究其强度和相位。一种y扫描台用于对传播的OAM光束进行三维剖析，从而对准直对OAM光束的影响进行了详细研究。所提出的系统被证明可以将光束发散角从36.6°减小到1.2°，而不会影响4-6 GHz频率范围内光束的OAM模式纯度。这项调查表明，朝着实现对承载OAM的光束发散的实际控制迈出了一步。