Introduction

The oscillator’s phase noise in a transmit chain results in power leakage into the adjacent channels. In the receive chain, the down-conversion of a large interferer with a noisy local oscillator causes reciprocal mixing. The trade-off between the quality factor of the switch capacitor bank that is tuning the LC oscillators and the oscillator’s tuning range is the obstacle in the wide tuning-range oscillator design. The MOS transistor switch introduces a resistance that defines the switched capacitor bank’s quality factor in on-state, consequently a lower resistance and so a larger MOS transistor is required for phase noise consideration. Most RF CMOS oscillators employ passive components such as integrated inductors, transformers, and capacitors to realize on-chip LC tanks. Generally, top thick metal layers are used for the realization of inductive components while thinner lower-level metals are exploited in the metal-oxidemetal capacitors.