Low Power CMOS VCO Using an 8-shaped Transformer

Abstract

This letter designs an LC-type CMOS NP-crosscoupled voltage-controlled oscillator (VCO) using an S-shape transformer used to boost the P-FET and N-FET source voltage swings for low power dissipation. 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 high-coupling coefficient. The transformer topology enables symmetric transformer layout and the two lobes of the 8-shaped primary and secondary inductors radiate far-field magnetic fields to suppress the magnetic field radiation. The die area of the VCO in the TSMC 0.1S$\mu$m CMOS process is 0.762 × 0.S55 mm2. The measured phase noise of the VCO at 2. 7S GHz.