A CMOS 21-48GHz fractional-N synthesizer employing ultra-wideband injection-locked frequency multipliers

Higher-order LC tanks with proper design parameters are proposed to widen the phase response to enhance the frequency locking range of mm-Wave injection-locked frequency multipliers (ILFMs). Employing a chain of such ILFMs at the output, a complete ultra-wideband fractional-N frequency synthesizer is demonstrated. Fabricated using a 65nm CMOS process, the synthesizer prototype measures a continuous output frequency tuning range of 80.2% from 20.6GHz to 48.2GHz when locked to a 4.5GHz to 6.1GHz fractional-N PLL with excellent phase noise <; -107dBc/Hz at 1MHz offset while consuming 148 mW.