Design of an original K-band active balun with improved broadband balanced behavior

• Published in: IEEE microwave and wireless components letters Vol. 15; no. 4; pp. 280 - 282
• Main Authors: Viallon, C., Venturin, D., Graffeuil, J., Parra, T.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2005; Institute of Electrical and Electronics Engineers
• Subjects: Active coupler; Amplifiers; Applied sciences; Balancing; balun; Baluns; BiCMOS integrated circuits; Broadband; Channels; Circuit properties; common mode rejection ratio; differential amplifier; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Errors; Exact sciences and technology; Frequency; Germanium silicon alloys; Impedance matching; Joining processes; K-band; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Noise levels; Phase measurement; Power dividers; Power measurement; Power splitters; Silicon germanides; Silicon germanium; Semiconductor alloys; Differential amplifier; K band; Two channel system; Active coupler; Microwave; Centimetric wave; Balun; Transistor; common mode rejection ratio; Implementation; Optimization; BiCMOS technology; Power divider; Wide band; Simulation; Impedance
• ISSN: 1531-1309; 1558-1764
• DOI: 10.1109/LMWC.2005.845749

This letter deals with the design of an active balun exhibiting a single-ended input and balanced outputs. We propose an original method, based on the determination of specific impedance for connecting the differential transistor pair to ground, which greatly improves the balanced behavior over a broadband frequency range. The usefulness of this method is demonstrated through a 180/spl deg/ power divider implemented on a 0.25-μm SiGe BiCMOS process. According to simulations, measurements confirm a broadband well balanced behavior, since the power splitter exhibits phase and amplitude errors between the two channels less than 4/spl deg/ and 0.5dB, respectively, from 0.2 to 22 GHz. These errors are only 0.75/spl deg//0.03 dB in a 2-GHz span around 20 GHz, in accordance with our optimization goals.