carlosgg123
Newbie level 1
Prescaler noise contribution to FracN PLL output noise
Hello, I am writing a program to calculate the noise contributions of various PLL components (VCO, Charge Pump, etc.) to the output. The PLL is a FracN and it uses a P/(P+1) prescaler and a delta-sigma modulator. I can simulate the noise output of the prescaler in the circuit simulator. My question: In order to *approximate* its noise transfer function, can I take the overall divide ratio
N = \[\frac{Fout }{Fref }\]
and then multiply the prescaler noise output by
\[\frac{1 }{Ndig }\]*\[\frac{G(s) }{1+H*G(s) }\]
where
Ndig = N/P
Is that a semi-decent approximation, or does it even make sense??
Thank you.
**broken link removed**
Page 49
Hello, I am writing a program to calculate the noise contributions of various PLL components (VCO, Charge Pump, etc.) to the output. The PLL is a FracN and it uses a P/(P+1) prescaler and a delta-sigma modulator. I can simulate the noise output of the prescaler in the circuit simulator. My question: In order to *approximate* its noise transfer function, can I take the overall divide ratio
N = \[\frac{Fout }{Fref }\]
and then multiply the prescaler noise output by
\[\frac{1 }{Ndig }\]*\[\frac{G(s) }{1+H*G(s) }\]
where
Ndig = N/P
Is that a semi-decent approximation, or does it even make sense??
Thank you.**broken link removed**
Page 49
