A 10 GHz multiphase LC VCO with a ring capacitive coupling structure

A multiphase LC voltage-controlled oscillator(VCO) with a novel capacitive coupling CL ladder filter structure is proposed in this paper and this 10 GHz eight-phase VCO is applied in clock and data recovery(CDR) circuit for 40 Gb/s optical communications system.Compared with the traditional eight-phase oscillator,this capacitive coupling structure can decrease the number of inductors to half and only of four inductors.The VCO is designed and taped out in TSMC 65 nm CMOS technology.Measurement results show the phase noise is 105.95 dBc/Hz at 1MHz offset from a carrier frequency of 10 GHz.The chip area of VCO is 480 μm×700 μm and the VCO core power dissipation is 4.8 mW with the 1.0 V supply voltage.