A model of spurs for multiphase fractional PLLs

Multiphase PLLs suffer from phase errors in the generated phases of the oscillator. These errors perturbate the oscillator's control voltage and fractional spurs are generated along with the intended carrier frequency. In this brief, a simple multiphase fractional PLL is described and a model of the fractional spurs due to the phase errors is presented. Simulation results of generated spurs of the multiphase PLL considering different loop parameters match closely with the theoretical derivations. Maximum error between the spur magnitudes of the analytical and simulated results is limited to 34%.