Broadband 4×4 Butler matrix in microstrip multilayer technology designed with the use of three-section directional couplers and phase correction Networks

A two-octave 4×4 Butler matrix has been presented, for the first time in multilayer microstrip asymmetric coupled-line technology. To achieve two-octave frequency band in terms of amplitude and phase responses a recently developed approach has been used in which multi-section coupled-line directional couplers and Schiffman C-sections are applied. A high-performance three-section coupled-line 3-dB microstrip directional coupler has been utilized as a basic element of the Butler matrix and two compensated microstripline Schiffman C-sections have been designed to provide appropriate differential phase characteristics. A very good performance has been achieved over two-octave frequency band in terms of amplitude and phase responses. The designed network can be easily applied in large microstrip networks as a surface mount element.