A -90dBc@10kHz phase noise fractional-N frequency synthesizer with accurate loop bandwidth control circuit

This paper describes a -90dBc@10kHz phase noise fractional-N frequency synthesizer of 110-180MHz output with accurate loop bandwidth control. Stable phase noise is achieved by controlling the bandwidth correctly, even if the PLL uses a noisy but small ring oscillator. Digital controller adjusts VCO gain and time constant of the loop filter. Analog controller compensates temperature variance. Test chip fabricated on 0.13/spl mu/m CMOS process shows stable and good phase noise performance against process and environmental variations.