A Double Fold 78 Butler Matrix Fed Multibeam Antenna with a Boresight Beam for 5G Applications

A substrate integrated waveguide multibeam antenna fed by a double-fold 7×8 Butler matrix (BM) beam-forming network (BFN) is presented. The proposed antenna is composed of a 7×8 BM feeding network and an 8×8 slot array. By merging the two central input ports of the BM into one port, the BM can provide output signals with equal phase, which can generate a boresight beam. In order to reduce the size of the antenna, the BM is folded twice into a three-layer structure. Measured results show that the proposed antenna has impedance bandwidth of 29.5 ∼ 30.5 GHz, whereas the gain lies in the range of 13.2–17.3 dBi. Seven beams, including a boresight beam, pointing from −58° to 58° are achieved. Compared with counterparts, the proposed antenna features boresight radiation and miniaturized size. It is a good candidate for the fifth-generation (5G) mobile network applications.