A 3 to 5 GHz low-phase-noise fractional-N frequency synthesizer with adaptive frequency calibration for GSM/PCS/DCS/WCDMA transceivers

A low-phase-noise S-A fractional-TV frequency synthesizer for GSM/PCS/DCS/WCDMA transceivers is presented.The voltage controlled oscillator is designed with a modified digital controlled capacitor array to extend the tuning range and minimize phase noise.A high-resolution adaptive frequency calibration technique is introduced to automatically choose frequency bands and increase phase-noise immunity.A prototype is implemented in 0.13μm CMOS technology.The experimental results show that the designed 1.2 V wideband frequency synthesizer is locked from 3.05 to 5.17 GHz within 30μs,which covers all five required frequency bands.The measured in-band phase noise are -89,-95.5 and -101 dBc/Hz for 3.8 GHz,2 GHz and 948 MHz carriers,respectively, and accordingly the out-of-band phase noise are -121,-123 and -132 dBc/Hz at 1 MHz offset,which meet the phase-noise-mask requirements of the above-mentioned standards.