Spurious Tone Suppression Techniques Applied to a Wide-Bandwidth 2.4 GHz Fractional-N PLL

This paper demonstrates that spurious tones in the output of a fractional- N PLL can be reduced by replacing the DeltaSigma modulator with a new type of digital quantizer and adding a charge pump offset combined with a sampled loop filter. It describes the underlying mechanisms of the spurious tones...

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Veröffentlicht in:IEEE journal of solid-state circuits 2008-12, Vol.43 (12), p.2787-2797
Hauptverfasser: Wang, K.J., Swaminathan, A., Galton, I.
Format: Artikel
Sprache:eng
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Zusammenfassung:This paper demonstrates that spurious tones in the output of a fractional- N PLL can be reduced by replacing the DeltaSigma modulator with a new type of digital quantizer and adding a charge pump offset combined with a sampled loop filter. It describes the underlying mechanisms of the spurious tones, proposes techniques that mitigate the effects of the mechanisms, and presents a phase noise cancelling 2.4 GHz ISM-band CMOS PLL that demonstrates the techniques. The PLL has a 975 kHz loop bandwidth and a 12 MHz reference. Its phase noise has a worst-case reference spur power of - 70 dBc and a worst-case in-band fractional spur power of -64 dBc.
ISSN:0018-9200
1558-173X
DOI:10.1109/JSSC.2008.2005716