Wide bandwidth Butler matrix network

Butler matrix networks, used for forming multiple beams from linear aerial arrays, are limited in their bandwidth of operation by their requirement for components with constant values of phase shift over this bandwidth. This letter describes a method for designing such networks for wide-bandwidth operation by employing particular combinations of directional couplers and hybrid tees, thus eliminating the need for separate phase shifts. Results are given for a 4×4port matrix operating over an octave range of frequency.