Mm-wave Multi-Beam Antenna Array Based on Miniaturized Butler Matrix for 5G Applications

In this paper, a microstrip-based 4 ×8 Butler matrix (BM) is presented. The main benefit of the design is the miniaturization of the beamforming network (BFN) structure. To obtain this objective, a classic 4×4 BM is designed, and then extended to a 4×8 one using dual substrate structure by implementing microstrip-to-slot line transitions. As a result, six of the crossovers in the traditional 4×8 BM topology are replaced by four transitions with low loss structures. To verify the BFN, an 8-element linear antenna array is integrated with the BM. By feeding the antenna array with the proposed 4×8 BM, four beams are generated in the azimuth plane pointing at difference directions with the scanning range of ±45
^°
operating at 27.5 GHz to 28.5 GHz band. The design is verified by the simulation results. Being compact, cost efficient, low-profile, and ease of fabrication makes the reported multi-beam antenna array an ideal candidate for fifth-generation (5G) communication systems.