An Enhanced Class-F Dual-Core VCO With Common-Mode-Noise Self-Cancellation and Isolation Technique

In this article, an enhanced class-F voltage-controlled oscillator (VCO) with common-mode-noise self-cancellation (CM-NC) and common-mode-noise isolation (CM-NI) technique is proposed. With the proposed CM-NC technique, the common-mode-noise current of the drain coil and that of the nearby source coil are in the opposite direction. Therefore, the magnetic fields generated by the two coils cancel each other, which reduces the noise injected into the VCO from power supply and the ground node. Moreover, the principle of decoupling between the two inductors is also employed to eliminate the influence of the common-mode tail inductor on the differential mode. By winding the gate coil into a double-turn structure, the coupling noise from the drain inductor to the gate is opposite to the induced current of the gate coil, thereby cutting off the noise coupling path from the drain to the gate. Thanks to the dual-core 8-shaped inductor structure, the phase noise (PN) is improved without increasing the area, compared with existing methods using separated and dedicated tail filtering inductors. The VCO is fabricated in a 65-nm complementary metal–oxide–semiconductor (CMOS) technology. The measured tuning range is 21.7% from 11.5 to 14.3 GHz. The PN and figure of merit (FoM) at 1-MHz offset are $-$ 119.2 and 192.8 dBc/Hz, respectively. The power consumption across the frequency tuning range is 5.6–10 mW. The core area is 0.065 mm $^{2}$ and the total area is 0.26 mm $^{2}$ .