Application of Broadband Branch-Line Coupler consisting of Impedance Transformers in 4 x 4 Butler Matrices designed in PCB and MMIC technologies

In this paper, the design of a novel 4 x 4 Butler Matrix composed of broadband branch-line couplers has been presented. To enhance the operational bandwidth of the circuit, for the first time, a branch-line coupler having additional two-section impedance transformers introduced in [16] has been utilized. To verify the applicability of the proposed design, two Butler matrices have been designed: in PCB and MMIC technologies. PCB circuit operates at 2 GHz center frequency. The structure has been designed, fabricated, and measured. The MMIC version of the considered Butler Matrix has been designed in the PH10 GaAs process offered by UMS and operates at 26 GHz center frequency. The circuit has been only designed and simulated electromagnetically.