3D Printed Multi-Beam OAM Antenna Based On Quasi-Optical Beamforming Network

In this paper, a multi-beam orbital angular momentum (OAM) antenna is proposed. By employing 3D printed millimeter-wave quasi-optical beamforming network (BFN), the emitted OAM wave can realize passive beam scanning capability. The antenna is composed of a pillbox BFN, a slotted waveguide antenna (SWA) array, and several full-dielectric phase elements (PEs) on the top of the SWA array. The required phase distribution of the OAM beams is turned by the phase shifts of the PEs. The pillbox BFN can generate the input waves with different phase gradients for the SWA array, and thus steer the beam direction. Moreover, the folded structure of the pillbox BFN can greatly decrease the size of the antenna. The proposed topology can be easily expanded to realize more beam number, higher directivity, and other OAM modes for its periodical structure. To verify the performance of the proposed antenna, a prototype is fabricated and measured. Two types of 3D printing technology are used, i.e., selective laser melting (SLM) for the pillbox BFN and the SWA array, and fused deposition modeling (FDM) for the PEs. The application of the 3D printed method greatly helps to decrease the fabrication difficulty. The measured results show that the antenna can achieve five +1 mode beams with ±20° 3 dB beam coverage range. Moreover, due to the full-metal structure of the BFN and the SWA array, the proposed design can achieve the minimum efficiency of 83.2%, which is much better than the other printed circuit broad (PCB) based OAM antennas. The advantages of low-cost beam scanning capability and the extensibility make the proposed antenna topology a good choice for future OAM communication and sensor systems.