James
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snowfiled
Posts: 32
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Dear Ken,
1, In your jitter+pnoise paper, I use the following fomulars to calculate my VCO jitter:
c=L(delta(f))*(delta(f))2/f02 J=sqroot(c*T)
my f0=200MHz, that's my VCO oscillating frequency, delta(f)=2MHz. 2MHz is the bandwidth for my PLL. T=1/200MHz (is it correct?)
from pnoise simulation in Cadence, I got L(delta(f))=-102dBc/Hz
Then I got Jitter=5.3ps. is it rms jitter or Peak to peak value?
2, in pnoise setup form, I found there is an option "jitter" in the "Noise Type" cyclic form. I thought I could get jitter by choosing this option. After simulation, I got the jitter value: rms=3.77p peak to peak=23.2986p
the exact resulet is like this: J[Second]@2e6Hz:rms=3.77p J[Second]@2e6Hz:ber=1e-3=23.2986p
I have the following questions:
1. what's ber and 1e-3 in the second jitter result? Why the calculation result and simulation result are different? Where am I wrong? ???
2. Why rms jitter is smaller than p2p jitter? I thought it should be larger than p2p jitter.
3. I also noticed that in the Result-->Main form, after choosing pnoise jitter and function as jitter, there is "modifier" with three choices: Second, UI, ppm. I should choose second I suppose, but what are the other two?
4. the reference freqency is 25MHz, divider ratio is 8, so my VCO is working at 200MHz. To get the widest bandwidth, I choose BW=1/10 reference frequency, i.e. about 2MHz. Sould I use 2MHz as delta(f) when I watching the pnoise result? In other words, should I use the bandwidth as the offset frequency?
Really appreciate your answer
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