A new resonant circuit for 2.45 GHz LC VCO with linear frequency tuning

A new MOS varactor bank is proposed to implement a 2.45 Ghz SiGe BiCMOS LC-tank voltage controlled oscillator (VCO) with linear frequency tuning. Compared to a conventional VCO, the proposed technique improves the quality factor of the LC-tank while preserving the linearity of the circuit. Realized in 0.25-nm SiGe BiCMOS technology, VCO exhibits 35% VCO gain (K
VCO
) variation from 2.29 to 2.66 Ghz with a 16% tuning ratio. The VCO also exhibits a phase noise of −113 dBc/Hz at 1 Mhz offset frequency and consumes 1.7 mA from 1.8 V supply.