Comparison of analytical predictions of the noise floor due to static charge pump mismatch in fractional-n frequency synthesizers

Interaction between the requantizer's periodic output and charge pump mismatch nonlinearity in a fractional-N frequency synthesizer causes it to exhibit an elevated inband noise floor and spurs. In this paper, we consider three leading analytical predictions from the literature. By comparing simulation results with analytical predictions, we show that the two most common approaches fail to deal correctly with offsets, while the method based on Price's theorem works well.