Folded Noise Prediction in Nonlinear Fractional-N Frequency Synthesizers
Abstract
The presence of nonlinearities in a fractional-N frequency synthesizer leads to the generation of an additional component of noise that appears in the output phase noise spectrum. This nonlinearity-induced noise component manifests itself as spurious tones and an elevated noise floor, also known as folded noise. This paper presents a mathematical analysis of the folded noise generated in fractional-N phase locked loops (PLL) by the interaction between the quantization noise introduced by the divider controller and a nonlinearity. The analysis is performed for different digital Delta Sigma modulators (DDSM) and nonlinearities, providing expressions that allow one to predict the folded noise. These are compared with state-of-the-art predictions and simulation results.
Publication Title
IEEE Transactions on Circuits and Systems I: Regular Papers
Recommended Citation
Mazzaro, V., & Kennedy, M. (2021). Folded Noise Prediction in Nonlinear Fractional-N Frequency Synthesizers. IEEE Transactions on Circuits and Systems I: Regular Papers, 68 (10), 4038-4048. https://doi.org/10.1109/TCSI.2021.3104275
