A 7.0-to-8.6 GHz Balanced Class-F-1 VCO with a Trifilar Transformer-Based Tank Achieving 194.5 dBc/Hz FoM

This paper presents a low phase noise (PN) balanced inverse-class-F (class-F-1) voltage-controlled oscillator (VCO). The proposed trifilar transformer integrates dual symmetrical class-F-1 VCO cores without extra tank area, enabling balanced differential outputs. A harmonic shaping strategy featuring a strong second harmonic and a weak third harmonic is adopted to ensure an optimal figure of merit (FoM). Fabricated in a 65-nm CMOS process, the prototype VCO demonstrates a frequency tuning range from 7.0 GHz to 8.6 GHz with a state-of-the-art FoM of 194.5 dBc/Hz at 10MHz offset.