A 2.5-GHz 860μW charge-recycling fractional-N frequency synthesizer in 130nm CMOS

A 1.2 V 2.5 GHz 860 muW fractional-N synthesizer is implemented in 130 nm CMOS. It employs charge recycling technique for implicit DC-DC conversion without using any voltage regulators, and achieves -77dBc/Hz and -113.5 dBc/Hz of phase noise at 100 kHz and 1MHz offset, respectively. Self-biased divider and VCO enables robust operation of the proposed circuit.