A 27.2GHz bipolar LC-VCO using class-C biasing to maximize achievable F<inf>osc</inf> in 130nm BiCMOS

A BJT based cross-coupled pair limits the maximum achievable oscillation frequency of LC-VCOs due to high parasitic capacitance in mature Si/SiGe technologies. In this work, class-C biasing is exploited to reduce cross-coupled pair parasitics, helping to enhance oscillation frequency without compromising phase noise performance. A design methodology is suggested to optimize cross-coupled pair parasitics with better phase noise performance. A dual-core architecture helps to achieve further phase noise improvement. The VCO is designed and fabricated in a 130nm BiCMOS technology using a bipolar cross-coupled pair. It achieves a maximum oscillation frequency of 27.2GHz and exhibits a measured phase noise performance of -110.7dBc/Hz @ 1MHz offset from the carrier, with an FoM of 181dBc/Hz.