Design of dual-band branch line couplers with circuit miniaturization

Design of a dual-band branch line coupler with a very compact size is proposed. For reducing circuit area, stepped-impedance sections are used. Folded open stubs are attached to each stepped-impedance section at its both ends for the dual-band purpose. Circuit dimensions and geometrics are designed in order to achieve the best circuit miniaturization. For validation, measured results of an experimental circuit are compared with simulation data.