A 4 GHz fractional-N frequency synthesizer

A 4 GHz fractional-N frequency synthesizer for telecommunications applications is presented. The synthesizer includes a multiple-modulus ECL prescaler capable of operating at input frequencies of up to 4.3 GHz with a power dissipation of 17.6 mW, a third-order MASH - modulator that controls the modulus of the prescaler, and a phase detector and chargepump that doesn't suffer from dead-zone problems. The synthesizer achieves a close-in phase noise of -66 dBc/Hz while dissipating only 27.7 mW from a 2.7 V supply. The synthesizer has been implemented in a 0.35 m BiCMOS technology.