A switched-capacitor current-reused VCO with symmetrical differential outputs

A switching-capacitor current-reused LC-VCO with degeneration resistors and capacitors has been presented in this paper. The proposed VCO reuses the dc current and has lower power consumption as compared with those of conventional VCO topologies. The usage of two degenerated resistors at the source terminals of NMOS and PMOS transistors enhances the characteristics of symmetry of differential outputs. The topology of switching capacitor results in smaller KVCO by dividing the wanted frequency range into four bands. Hence, the phase noise is indeed improved. The proposed current-reused LC-VCO is designed for applications on 2.45-GHz communication systems. Measurement results show −104.85 and −124.6 dBc/Hz at 100-kHz and 1-MHz offset from 2.359GHz, respectively at a consumption current of 2.6mA from a 1.8-V supply. The output power is up to 4.14 dBm.