A Compact 190 GHz Push-Push Colpitts VCO in 130-nm BiCMOS with 3.5%-DC-to-RF Efficiency and 3.9-dBm Peak Output Power

A compact high-DC-to-RF-efficiency push-push Colpitts voltage-controlled oscillator (VCO) operating at 190 GHz is proposed. By introducing a second-harmonic quarter-wavelength open-circuited transmission line (QOTL) at the base of the bipolar junction transistor (BJT), more RF power is delivered to the load, and both output power and DC-to-RF efficiency are enhanced. Fabricated in a $130-\mathrm{nm}$ SiGe BiCMOS process, the VCO prototype driving a $50-\Omega$ load without additional buffer measures a frequency range from 185.3 GHz to 192.4 GHz while achieving 3.9-dBm peak output power and 3.5% DC-to-RF efficiency and occupying a core area of $180 \times 185 \mu \mathrm{~m}^{2}$.