Circularly Polarized Multibeam Antenna Array of ME Dipole Fed by 5 × 6 Butler Matrix

A circularly polarized multibeam antenna array based on magnetoelectric (ME) dipole is proposed, which is fed by a substrate integrated waveguide 5 × 6 Butler matrix. There are two points that are key to completing the design-the wide axial-ratio (AR) beamwidth antenna element and the appropriate beamforming network. By adjusting the shape of the radiation patch of ME dipole, the amplitude of the orthogonal field becomes flatter at a wide angle, and the phase difference is maintained at 90°; hence, an antenna element with a wide 3 dB AR beamwidth can be achieved. In order to ensure the generation of normal beam, a 5 × 6 Butler matrix using the 3 × 3 Butler matrix is selected as the beamforming network. The proposed structure operates in the range of 27.5-28.5 GHz and generates five circularly polarized beams that cover the range of ±40°. The gain of all these beams is approximately 12.5 dBi.