A 15.2-to-18.2GHz Balanced Dual-Core Inverse-Class-F VCO with Q-Enhanced 2nd-Harmonic Resonance Achieving 187-to-188.1dBc/Hz FoM in 28nm CMOS

The emerging wireless systems can profit from a low-phase-noise high-frequency-band local oscillator (LO) to enable the use of dense modulation schemes over a wide signal bandwidth. When the LO frequency escalates from RF to millimeter waves, the capacitive devices (e.g., varactor and switched capacitor) tend to dominate the tank quality factor (O) of the voltage-controlled oscillator (VCO), imposing a severe trade-off between the phase noise (PN) and the frequency tuning range. Meanwhile, the technology downscaling further exacerbates this trade-off since the advanced process nodes demand more metal layers to connect transistors in a higher density, diminishing the metal thickness and thus reducing the Q of the metal-oxide-metal (MOM) capacitor. Besides, the deteriorating 1/f noise of MOS transistors in the advanced processes is another challenge faced by the VCO PN performance. Consequently, the PNs and the figure-of-merits (FoMs) of recent VCOs in 28nm CMOS [1–3] are inferior to their 65nm [4] and 40nm [5] counterparts.