A 2.5GHz CMOS Fully-Integrated \Delta\Sigma-Controlled Fractional-N Frequency Synthesizer

The design of a fully-integrated \Delta\Sigma-controlledfractional-N frequency synthesizer is described.Using adual modulus 64/72 prescalar based on injection lockingtechnique and a novel third order digital \Delta\Sigma modulator,we achieved an extremely low power synthesizer in2.5GHz band.. Total power dissipation of the frequencysynthesizer is less than 6mW at a 1.5V supply.The loopbandwidth is optimized to achieve a -123dBc/Hz phasenoise at 3MHz offset frequency.The locking time of theloop is less than 30µs.