The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Measurements >> Phase Noise and Jitter Measurements >> How to calculate the PLL Jitter form VCO Jitter?
https://designers-guide.org/forum/YaBB.pl?num=1120146032

Message started by tumeda on Jun 30^th, 2005, 8:40am

Title: How to calculate the PLL Jitter form VCO Jitter?
Post by tumeda on Jun 30^th, 2005, 8:40am

Hello everybody :D
After the rightly setup in spectre RF and post calculation according to the paper "Predicting the phase nosie and jitter of PLL .....", we can ge the jitter value of VCO at an offset frequency, which should lie at a rate of -20db per decade.
The question is now: how to calculate jitter value of the whole PLL circuit, in other words, how to get the influence of the VCO to the whole PLL circuit. :-/
Are the following two methods right?
1. Input the VCO jitter value into the VCO behavioral model, and then make a transient simulation. At the PLL steady-state case, is the standard deviation of PLL output periods the PLL jitter?
2. Knowing the jitter value of VCO, could we directly use the phase noise transfer function (s-domain analysis) to calculate the PLL jitter? And at which freuency the value shoule be calculated out?

ps: The jitter value depends on the offset frequrncy. For a VCO circuit,the VCO's influence to PLL jitter is constant. If we select two different offset frequencies, so there would generate two different jitter values, which could give two different PLL Jitter values. There seem to some contradiction. ???