Impedance-controlled wideband active balun based on current conveyors

The first active power-split balun with controllable output impedance is proposed. Its operation is wideband, with good balance characteristics from DC to 3 GHz. It takes up 0.036 mm in a 0.35 mum SiGe BiCMOS technology and is the smallest balun ever observed. Its additional properties are: excellent and wideband overall S-parameter performance; highest linearity observed for a balun; and stability against temperature and process variations.