A Wide-tuning-range VCO with Small VCO-gain Fluctuation for Multi-band W-CDMA RFIC

A novel wide-tuning-range LC-tuned voltage-controlled oscillator (LC-VCO) - featuring small VCO-gain (K
_VCO
) fluctuation - was developed. For small K
_VCO
fluctuation, a serial LC-resonator that consists of an inductor, a fine-tuning varactor, and a capacitor bank was added to a conventional parallel LC-resonator that uses a capacitor bank scheme. The resonator was applied to a 3.9-GHz VCO for multi-band W-CDMA RFIC fabricated with 0.25-mum Si-BiCMOS technology. The VCO exhibited K
_VCO
fluctuation of only 21%, which is one third that of a conventional VCO, with 34% tuning range. The VCO also exhibited a low phase noise of -121 dBc/Hz at 1-MHz offset frequency and a low current consumption of 4.0 mA