Wandering spur suppression in a 4.9-GHz fractional-N frequency synthesizer

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Mai, Dawei
Donnelly, Yann
Kennedy, Michael Peter
Tulisi, Stefano
Breslin, James
Griffin, Patrick
Connor, Michael
Brookes, Stephen
Shelly, Brian
Keaveney, Mike
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Institute of Electrical and Electronics Engineers (IEEE)
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Fractional-N frequency synthesizers that use a digital Δ-Σ modulator (DDSM) to control the feedback divider can exhibit spurious tones that move about in the frequency domain; these are known colloquially as ``walking'' or wandering spurs. Building upon a theoretical explanation of the origin of wandering spurs, this article presents two methods to suppress them. It describes a 4.9-GHz 180-nm SiGe BiCMOS charge-pump phase-locked loop (CP-PLL) fractional-N frequency synthesizer platform with a divider controller that can function as: 1) a standard MASH 1-1-1; 2) a MASH 1-1-1 with high-amplitude dither; and 3) a MASH 1-1-1 with a modified third stage. Measurements confirm the effectiveness of the wandering spur suppression strategies.
Divider controller , Fractional-N frequency synthesizers , Phase noise , Phase-locked loops (PLLs) , Quantization noise , Spurious tones , MASH digital Δ-Σ modulator (DDSM)
Mai, D., Donnelly, Y., Kennedy, M. P., Tulisi, S., Breslin, J., Griffin, P., Connor, M., Brookes, S., Shelly, B. and Keaveney, M. (2022) 'Wandering spur suppression in a 4.9-GHz fractional-N frequency synthesizer', IEEE Journal of Solid-State Circuits. doi: 10.1109/JSSC.2022.3163080
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