A Highly Compact Active Wideband Balun With Impedance Transformation in SiGe BiCMOS

A new conveyor-based single-ended to differential balun is proposed. Thanks to the quasi-absence of passive components, this is an extremely size-efficient balun (0.036 ). The use of a new impedance-matching technique makes this balun the first transistor-based solution with controllable port impedances. Fabricated in a 0.35-mum SiGe BiCMOS technology with f
_T
=45 GHz, the balun shows the following performance: wideband impedance matching at all three ports, good balance between the two outputs (better than 3 dB in amplitude and 13deg in phase) over frequency bands extending from 0 to 3 GHz, linear operation for powers up to input powers of -2 dBm, and stability against temperature and process variations.