Design and realisation of reduced-size impedance transforming uniplanar MMIC branchline coupler

Design equations for the realisation of a reduced-size impedance transforming branchline coupler are presented together with the measured results of a fabricated prototype GaAs MMIC coupler using coplanar waveguide (CPW) transmission lines. The coupler which is less than 25% of the area of the standard branchline coupler has low coupling imbalance, with good return losses, and excellent isolation.