Area-efficient and Coupling Noise Suppressive Voltage-controlled Oscillator

This letter designs an inductance-capacitance (LC) NMOS cross-coupled voltage-controlled oscillator (VCO). The VCO uses a 2-turn two-lobe 8-shaped inductor for interference noise suppression and a center-tapped coupled degenerated-source inductor to boost the voltage swing. The VCO-core 8-shaped inductor consists of one 2-turn O-shaped inductor in a twisted series. In addition, the VCO uses a tail for phase noise improvement to boost the tank Q factor dynamically. The die area of the current-biased VCO fabricated in the TSMC 0.18μm CMOS process is 0.833 ×0.782 mm². The measured oscillation frequency of the VCO is 6.979 GHz and the phase noise at 1 MHz offset is -119.329dBc/Hz. and the figure of merit (FOM) is -189.86dBc/Hz at a power consumption of 3.875mW. The tail inductor with the 8-shaped inductors forms a low-coupling coefficient transformer.