Abstract: An integer-N frequency synthesizer in 0.35μm SiGe BiCMOS is presented.By implementing different building blocks with different types of devices,a high purity frequency synthesizer with excellent spur and phase noise performance has been realized.All the building blocks are implemented with differential topology except for the off-chip loop filter.To further reduce the phase noise,bonding wires are used to form the resonator in the LC-VCO.The frequency synthesizer operates from 239 to 2.72GHz with output power of about 0dBm.The measured closed-loop phase noise is -95dBc/Hz at 100kHz offset and -116dBc/Hz at 1MHz offset from the carrier.The power level of the reference spur is less than -72dBc.With a 3V power supply,the whole chip including the output buffers consumes 60mA.

Key words: SiGe BiCMOS, phase-locked loop, high purity, loop bandwidth