Comparison of Mathematical and Physical Phase Noise Performance in Fractional-N Synthesizers

Fractional-N frequency synthesizers are widely employed in wireless communications to produce sinusoidal carrier signals. Traditionally, analog synthesizers have offered the best phase noise performance whilst digital synthesizers are more flexible and have also demonstrated excellent phase noise performance. In addition, hybrid architectures have looked to combine the benefits of both analog and digital. This paper provides a qualitative analysis of the performances for each architecture with an eye towards identifying their respective performance limits.