Planar Two-Dimensional Scanning Multibeam Array Antenna Based on a 3 × 3 Butler Matrix Network

In this letter, a wideband two-dimensional (2-D) scanning multibeam array antenna is proposed using a novel beamforming network (BFN). First, a novel three-beam Butler matrix (BM) network, as the core of the BFN, is proposed and described. The BM network comprises a directional coupler, T-shaped power dividers, and coupling baluns, which avoids using crossovers and lossy lumped elements as in a conventional BM network. In addition, a dual-stripline structure is employed to combine multiple components, which considerably reduces the BM network aperture. Then, six three-beam BMs are stacked and interconnected to form a complete 2-D BFN, whose scanning features of two orthogonal planes are controlled by two sets of BMs. Finally, to verify the working principle of the BFN, a 3 × 3 all-metal antenna array is designed and combined with the BFN. Notably, the low-profile antenna element achieves a wide operating bandwidth of 34.5%. Furthermore, a prototype is fabricated and tested, which shows that the antenna realizes switched beams in nine directions, indicating that an excellent 2-D scanning function is realized.