Miniaturized broadband 4 × 4 Butler matrix designed with the use of quasi-lumped coupled-line couplers

The design of a miniaturized broadband 4 × 4 Butler matrix has been presented. The designed Butler matrix utilizes the developed single-section coupled-line 3-dB/90° directional couplers designed with the use of a quasi-lumped element technique. The broadband 45° phase shifters have been realized as a tandem connection of two such couplers providing simultaneously transmission-line crossover. The measurement results of the developed miniaturized broadband 4 × 4 Butler matrix operating in the frequency range 1.6-1.6 GHz are shown.