Filtering technique to lower phase noise for 2.4GHz CMOS VCO

Abstract

With a simple analysis of phase noise in voltage-controlled oscillators, a 2.4 GHz CMOS LC VCO is designed in 0.18 ¿m CMOS technology. The proposed VCO uses three filters to remove noise from the tail current source, the reference current source, and the output node of VCO core. The VCO has a tuning range from 2.29 GHz to 2.59 GHz, while the VCO core draws 3 mA of current from 1.8 V power supply. The achieved phase noise is -138 dBc/Hz at 3 MHz offset and -103.1 dBc/Hz at 100 kHz offset frequency.