Eight-beam wide coverage ridge waveguide slot antenna array based on 4×4 Butler matrix

Multibeam antennas fed by Butler matrices (BMs) can effectively combine passive beamforming networks with antenna arrays. However, limited structural approaches exist for BM-integrated antennas to address the issues associated with scan loss and null regions. This paper presents a ridged waveguide slot antenna array integrated with a 4 × 4 BM that generates four dual-lobe radiation patterns, thereby expanding spatial coverage without increasing hardware complexity. By strategically configuring the grating lobes with appropriate element spacing, the architecture covers eight interleaved angular directions across four beam states. To mitigate inherent beam scan loss and crossover loss, periodic groove structures are integrated between adjacent arrays to optimize the mutual coupling. Furthermore, a vertically integrated center-fed ridged waveguide configuration is employed to miniaturize the footprint and suppress beam squint. At the center frequency of 62.5 GHz, the fabricated antenna demonstrated a peak gain of 19.7 dBi. The eight interleaved beams provided a wide angular coverage of ± 79∘ with a gain imbalance of less than 1.9 dB. The prototype maintained a reflection coefficient below $$-10$$ dB over a 13.4% fractional bandwidth of 59–67.5 GHz. Thus, the proposed antenna has strong potential to be employed in future multiuser millimeter-wave wireless communication systems.