Generation of Plane Spiral OAM Waves Using Traveling-Wave Circular Slot Antenna

Plane spiral orbital angular momentum (OAM) wave is a new form of OAM-carrying electromagnetic wave that propagates along the transverse direction. A traveling-wave circular slot antenna that can generate plane spiral OAM waves is developed and experimentally demonstrated in this letter. The antenna is excited by a 90° hybrid coupler. In order to ensure that the OAM waves are propagating along the transverse plane, a ring horn is added outside the antenna. A prototype with OAM states l = ±3 for 10-GHz operation is fabricated and measured. The near-field phase distributions clearly indicate the azimuth phase shifting, and the radiation patterns show the characteristic of transverse propagation, respectively. The proposed antenna provides a novel approach to implement an OAM wireless communication link that has no phase singularity or divergence problem.