Design of a broad-band novel Butler matrix

A novel broad-band Butler matrix, incorporating 180° hybrids instead of 90° couplers, is designed. Impedance-transforming 180° hybrids and Schiffman's phase shifters are employed in the circuit. The Butler matrix has been rearranged to eliminate the crossovers, achieving an excellent amplitude performance, and flat phase responses over the frequency range of 1.6–2.4 GHz.