Low Phase Noise CMOS Using a Voltage Boosting 3:1 8-Shaped Transformer Resonator

This brief presents an LC-type CMOS NP-cross-coupled voltage-controlled oscillator (VCO). The VCO utilizes a new 8-shaped transformer to enhance the P-core MOSFETs source voltage swing, achieving low power dissipation and improved phase noise performance. The transformer uses two 3-turn coils twisted in series as the primary, and the layout method reduces the number of crossing metal lines and parasitic capacitance. The one-turn 8-shaped secondary interleaves with the primary to get a high coupling coefficient. The 3:1 transformer topology enables a symmetric transformer layout, and the two lobes of the 8-shaped transformer radiate far-field magnetic fields to suppress the magnetic field radiation. The die area of the VCO in the TSMC 0.18 μm CMOS process is 0.798 × 0.762 mm². The measured phase noise of the VCO at 2.99 GHz is -124.9 dBc/Hz, it achieves one of the best FOMs in sub-mW VCOs. The VCO figure of merit (FOM) is -198.05 dBc/Hz.