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questions in simulating jitter performance of crystal osc +squaring buffer (Read 2301 times)
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Shanghai
questions in simulating jitter performance of crystal osc +squaring buffer
Dec 01st, 2014, 5:50pm
 
Hello,

These days I was working on crystal osc +squaring buffer. I care about the jitter performance mostly. I have searched many literature and forum, but still have some questions here.
the mmsim is 10.1, the ADE is 5.1.41.

when simulating the jitter performance.
1, since the most noise contribution is from the squaring buffer, (the output of crystal osc is a nearly pure sine wave) . I simulate the buffer separately with a isin from analogLib (to mimic the output of crystal). So I choose pss +pnoise (jitter mode, PM). and set the threshold value to vdd/2. and calculate the jitter from Jee curve.
jitter= sqrt(integ(Jee^2, 10k, 1M))
it's about 100fs. and the most contribution (90%) is Rf from the first stage.

2, I simulate crystal +buffer together. now it's a autonomous circuit, I can't choose pnoise jitter mode(PM), so I choose pnoise source mode.
and calculate the jitter from phase noise curve.
jitter=sqrt(2*integ(10^(phase noise/10) 10k, 1M))/(2*pi*fosc)
it's about 30fs, and no Rf contribution in noise summary.

I can't explain which is correct. For the application, I certainly care about the threshold crossing jitter. but I can't simulate that for crystal +buffer together.


[img][/img]

since I need to know which simulation give the real-world jitter performance, then I can do the trade-off in deciding the parameters for each component.
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Re: questions in simulating jitter performance of crystal osc +squaring buffer
Reply #1 - Dec 1st, 2014, 5:55pm
 
this pic is for simulating buffer separately with pnoise jitter mode. [img][/img]
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Re: questions in simulating jitter performance of crystal osc +squaring buffer
Reply #2 - Apr 7th, 2018, 11:16am
 
Hello,

I also design almost the same circuit this period and i face the same problem...

more specifically i measure the phase noise at the output of the pierce oscillator which is equal to -145dBc/Hz and then i measure the phase noise at the output of the sine to square which is equal to -160dBc/Hz which is not a reasonable result...

i use spectre and mmsim15.01 for my simulations...  

Did you finally managed to solve this simulation problem??
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