A tunable Marchand balun at K band in silicon germanium (SiGe) technology

This paper presents the design of a switch-based, tunable Marchand balun at K band. The tunability is achieved by using pass gate CMOS structures that ideally switch in or out sections of the balun, thereby controlling its frequency response. The balun is fabricated in a high performance SiGe BiCMOS process with standard 180 nm CMOS technology. The ability to tune the response across a frequency range is demonstrated. The balun is characterized in terms of mixed signal scattering parameters. Extensive layout and simulations have been executed. The authors believe this is the first demonstration of a tunable balun using pass gate structures to change the lengths of the balun windings in the high region of the microwave range.