A Compact VCO Using Coupling-Canceling Common-Mode Resonance Expansion Achieving 120–155kHz 1/f³ Corner and 0.27dB FoM Variation Without Harmonic Tuning

This paper presents a voltage-controlled oscillator (VCO) with low flicker phase noise corner, leveraging a coupling-canceling (CC) common-mode (CM) resonance expansion technique. The design features a tail 8-shaped inductor coupled with the drain inductor to create a high-order CM resonance, enhancing the CM resonance expansion. To achieve a high and wideband CM impedance within a compact layout, staggered tap inductors are employed to mitigate the CM coupling effect, effectively addressing the notch issue in transformer-based wideband networks. Consequently, both the drain and source of the MOSFET benefit from wideband CM resonance. The proposed VCO achieves a low 120 kHz 1/f³ phase noise corner while consuming only 6 mW at 8.45 GHz. It is fabricated in a 65-nm CMOS process and occupies a core area of 0.115 mm². The measured phase noise at a 1 MHz offset frequency is -121.64 dBc/Hz, yielding a peak Figure-of-Merit (FoM) of 192.25 dBc/Hz. The FoM variation at 1 MHz offset is below 0.27 dB, and the 1/f³ corner remains below 155 kHz across the entire tuning range, without requiring manual CM tuning.