A UHF Low-Spur, Low- Phase Noise Fractional-N Synthesizer in 0.18-μm CMOS

A fully-integrated fraction al-N synthesizer (FNS) is designed and implymented, for a single-chip UHF transceiver, using 1P6M 0.18-mu m RF CMOS process. The synthesizer provides very low phase-noise and extremely low reference spur RF source covering 880MHz to 1260MHz, incorporating on-chip active loop-filter and dual-stage charge-pump circuits. The measured phase-noise is -116dBc/Hz at 200KHz offset and -142dBc/Hz at 3.3MHz offset while maintaining 20MHz reference spur levels lowers -84dBc over the entire tuning range. The active die area is 2.2mm x 1.8mm. The chip operates over a wide range of supply voltage from 1.6 V to 2.0V and temperature from -25 degrees C to -75 degrees C respectively. The chip draws 47mA current from a +1.8V supply at +25 degrees C.