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question about extraction phase noise parameters of pfd-cp and divider (Read 3345 times)
noiseless
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question about extraction phase noise parameters of pfd-cp and divider
Jul 29th, 2008, 2:41am
 
As expressed in Ken's  “Predicting the phase noise and jitter of PLL-based frequency synthesizers”, in order to simulate in the phase domain, pfd-cp and divider phase noise parameters should be extracted first, then use it to do the simulation. However, I am confused about how to do it will get right result.
1.for example, for the divider, we know use jitter option of the PNoise to do the jitter simulation. But how to do to get phase noise? I tried to use equation (35) to do the compare, which tdomain output noise as Sn(f), Jee result as SΦ(f). However, they are not equal.
2. for the pfd-cp simulation, I use PNoise to do the simulation, the script is as below
analysis('pnoise ?sweeptype "relative"  ?relharmnum "1"  ?start "100"  
           ?stop "50M"  ?dec "30"  ?maxsideband "30"  ?oprobe "/IPRB0"  
           ?iprobe ""  ?refsideband ""  )
analysis('pss ?fund "10M"  ?harms "10"  ?errpreset "moderate"  
           ?tstab "200n"  )
I use Iprobe to sense the current noise, which connected to a voltage source to bias the DC voltage. However, the result is somewhat weird (see the attached pic). There is some spurs in the black circle and there is no apparent noise bandwidth there as shown in Ken's paper. My setup is right or not? appreciate any comments
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Ken Kundert
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Re: question about extraction phase noise parameters of pfd-cp and divider
Reply #1 - Jul 29th, 2008, 1:36pm
 
2. Those peaks are associated with the harmonics of the oscillation. The phase noise is mixed up not just to the fundamental, but also to every harmonic. You sweep range overlaps several harmonics.

-Ken
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noiseless
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Re: question about extraction phase noise parameters of pfd-cp and divider
Reply #2 - Jul 29th, 2008, 6:51pm
 
Ken, appreciate your reply
for 2, do you have idea why there is no corner for the noise bandwidth?

for 1, I found that what get from Jee is not SΦ(f), which unit is sec/sqrt(Hz). So in order to get SΦ(f), SΦ(f) should be equal to (2πfo)^2*Jee. Am I right?
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Re: question about extraction phase noise parameters of pfd-cp and divider
Reply #3 - Aug 3rd, 2008, 10:17pm
 
In the Page 45 of Ken's "pnoise+jitter" papaer about matlab script for computing SΦ(Δf), cumfum function is used to compute phase. Here I am confused. periods variable is for jitter, which is random here. Fourier transform of autocorrelation of random is PSD. why do not use autocorrelation function but cumsum function?

actually, I tried autocorration function, the result seems not right. However I do not know the reason. Can anyone explain it? appreciate
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