A Design of Multibeam Antenna with 2-D Beam Steerable Capability

In this letter, a design of multibeam antenna (MBA) with two-dimensional (2-D) beam steerable capability is proposed. The proposed MBA is composed of a circular 4 × 4 butler matrix (BM) and a 2 × 4 patch antenna array. And the 2 × 4 patch antenna array consists of four two-element subarrays uniformly arranged along the E-plane. By introducing the switching diodes in the subarray and controlling the switching diodes on and off, elements of the subarray are excited through the paths with different lengths, and the beam of the subarray is steered subsequently in the H-plane. The circular 4 × 4 BM is designed as the beamforming network to excite the four subarrays uniformly arranged along the E-plane and steer the beam in the E-plane. The proposed MBA can generate 12 beams by selecting the excitation port and controlling the on-off state of the switching diodes. To validate the performance of the proposed MBA, a prototype is fabricated and measured. By design, the dimension of the designed MBA has reduced to 2.9 λ0 × 1.3 λ0. The designed MBA operates at 5.7 GHz, and the results show that the beams of the MBA can cover the range of ±36° in the E-plane and ±22° in the H-plane, respectively.