A novel 4 × 4 butler matrix with continuously tunable phase covering 360° range and application for 1-D and 2-D beam scanning array

A novel 4 × 4 Butler Matrix (BM) with continuously tunable phase covering phase range from −180° to 180° is proposed using substrate integrated waveguide technology. The proposed BM consists of two H-plane hybrid couplers, two E-plane hybrid couplers and four 180° tunable phase shifters. With this simple configuration, the proposed BM can realise a continuously tunable progressive phase difference from −180° to 180° in a one-dimensional (1-D) or two-dimensional (2-D) form. For demonstration, the proposed BM has been fabricated to feed a 1 × 4 or 2 × 2 broadband microstrip antenna arrays. The fabricated prototype has a 16.7% fractional impendence bandwidth centred at 6 GHz. The measured pattern for the 1-D array showed a continuous beam scanning range from −39° to 39° in H-Plane, while the measured radiation patterns for the 2-D array showed continuous beam range from −27° to 30° in elevation and 0°–180° in azimuth. The measurement results were in good agreement with the simulation results.