In charge-pump phase-locked loops, the reference signal samples the phase delay between reference and feedback signal. When a frequency divider is present in the loop, the spectrum folding of the VCO phase noise caused by the inherent sub-sampling operation adds a relevant contribution to the in-band output noise. This paper elaborates the discrete-time linear model of PLLs, in order to take into account spectrum folding, and provides a simple equation for the estimation of the output noise. The closed-form expressions are validated on the basis of behavioral simulations of a third-order charge-pump PLL.

Folding of Phase Noise Spectra in Charge-Pump Phase-Locked Loops Induced by Frequency Division

LEVANTINO, SALVATORE;SAMORI, CARLO;LACAITA, ANDREA LEONARDO
2010-01-01

Abstract

In charge-pump phase-locked loops, the reference signal samples the phase delay between reference and feedback signal. When a frequency divider is present in the loop, the spectrum folding of the VCO phase noise caused by the inherent sub-sampling operation adds a relevant contribution to the in-band output noise. This paper elaborates the discrete-time linear model of PLLs, in order to take into account spectrum folding, and provides a simple equation for the estimation of the output noise. The closed-form expressions are validated on the basis of behavioral simulations of a third-order charge-pump PLL.
2010
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/571143
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