28 GHz Multi-Beam Antenna Array Based On A Compact Wideband 8×8 Butler Matrix

In this paper, a multi-beam antenna array fed by a wideband 8×8 Butler matrix, based on low loss PCB based aperture hybrid couplers, is presented. The compact Butler matrix with the size of only 42 mm×61 mm is usable from 25 ... 30GHz. As a radiation element a 1 × 8 Vivaldi antenna array was implemented. Beam pattern measurements results are highly coincidental with the simulations showing 8 beams with different spatial angles in the range of ±61°, more than 8dB side lobe suppression and an average 13dBi radiation gain.