A 3 V 4 GHz nMOS voltage-controlled oscillator with integrated resonator

There is increasing interest in implementing the key components of radio transceivers in mature silicon technologies. Submicron CMOS technology combined with low-parasitic on-chip passives is emerging as a strong candidate to implement many of these components that traditionally have been realized using GaAs. Fully-monolithic voltage-controlled oscillators (VCOs) present many challenges to any technology since they require low-parasitic high-quality passives for acceptable tuning range and phase noise levels, and low-power active devices at microwave frequencies. A 1.8 GHz CMOS VCO with a 4.5% tuning range is not fully monolithic, as it requires bonding wires as inductive elements in the tank circuit. Fully-integrated LC resonators offer the advantages of low cost and reduced sensitivity to packaging parasitics at the price of lower resonator Q values due to the losses in on-chip spiral inductors and varactor diodes. The authors present a fully-monolithic VCO based on an nMOS gain stage and an integrated tunable resonator operating at 4 GHz with a 9% tuning range. The technology is a 5-level metal 0.5 /spl mu/m BiCMOS process (BiCMOS4S+). No bipolar devices are used in the active circuitry.