A 7 × 8 Butler Matrix-Fed Multibeam Antenna Based on Substrate Integrated Waveguide Technology

Abstract

In this letter, a novel 7 × 8 Butler matrix (BM) operating in the millimeter-wave band is presented. It is composed of a 3 × 4 BM, two 3 × 4-like BM, two phase shifters and two couplers, achieving equal amplitude output distribution and seven output phase differences (0°, ±45°, ±90°, ±135°). The proposed 7 × 8 BM can be realized by dual-layer substrate integrated waveguide structure easily, which is difficult for merging the two central ports of the traditional 8 × 8 BM. To verify the concept, a multibeam antenna fed by the proposed BM is designed and fabricated, achieving seven beams in the frequency range of 26.5–29.5 GHz. Compared with counterparts, the proposed antenna features compact size, broadside radiation, and relatively wide bandwidth.