A Concentric Array for Generating Multimode OAM Waves

Abstract

For the problem of multiplexing multimodal vortex electromagnetic waves, a double-ring concentric uniform circular array (CUCA) consisting of 12 circularly polarized antennas (4 inner rings and 8 outer rings) is proposed in this paper. A complex feeding network is solved by rotating the circularly polarized antennas at a certain angle. The antennas are rotationally symmetric and point to the center, generating orbital angular momentum (OAM) waves by feeding the same amplitude and phase signals. In addition, this paper combines millimeter wave (mm-wave) and ultra-wideband (UWB) with OAM. The proposed antenna array can generate OAM beams at 30–40 GHz with ℓ = −1, −2. When ℓ = −1 the relative bandwidth is 25.2% and the gain is 8.03 dBi; when ℓ = −2 the relative bandwidth is 27.7% and the gain is 9.43 dBi. The analysis of simulation results shows that the antenna array has UWB performance, good gain, and a standard spiral phase distribution, which can provide some practical significance for modal multiplexing of mm-wave band OAM.