Finite-ground coplanar-waveguide branch-line couplers

Two branch-line (BL) couplers based on finite-ground coplanar-waveguide (FGCPW) structures are proposed. The first one uses the bended structure to reduce the size of the normal quarter-wavelength two-arm BL coupler. The second one improves the bandwidth by adding external compensated networks, which are also folded for size reduction. In this study, the performances of these BL couplers are examined, theoretically and experimentally.