Miniaturized 4×4 Butler Matrix Using Slow-Wave Ridged Half-Mode Substrate Integrated Waveguide

This brief proposes a miniaturized
$4\times4$
Butler matrix using slow-wave ridged half-mode substrate integrated waveguide (RHMSIW). By etching the metal ridge of RHMSIW with periodic grooves, slow-wave characteristic is enabled with increased phase constant, and therefore couplers in Butler matrix are miniaturized. Compared with the conventional SIW-based
${H}$
-plane
$4\times4$
Butler matrix, the electrical width and length of the proposed design are reduced by 82% and 34.3% respectively. The measured results agree well with the simulated results. The proposed miniaturized Butler matrix is promising for multibeam antennas with compact size, low cost and easy integration.