A 1.8 GHz CMOS VCO with reduced phase noise

A 2 V, 6 mA, 15% tuning range, 1.8 GHz VCO implemented in a standard 0.35 /spl mu/m CMOS process is presented. The phase noise of the VCO has been greatly reduced by means of on-chip filters and one off-chip low frequency inductor. The phase noise measured at 3 MHz offset from the carrier is between -141.5 dBc/Hz and -138.5 dBc/Hz over the whole tuning range.