An Analysis of Phase Noise in Realigned VCOs

This brief presents an analysis of realigned voltage-controlled oscillators (VCOs) leading to an analytical expression for their phase noise (PHN), which is of more general validity than those currently available in the literature. This brief further discusses a phenomenon that seems to have been given little attention, i.e., the increase by 3 dB of the high-frequency part of the PHN of a realigned VCO compared to the PHN of the same VCO in free running. Considerations on the impact of this effect and of the cyclostationary nature of the PHN in realigned VCOs on some typical applications are also given. The results are verified by numerical simulations.