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High Q crystal oscillator PSS and Pnoise (Read 6176 times)
rfmems
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High Q crystal oscillator PSS and Pnoise
Jul 25th, 2012, 5:15am
 
I have been trying to figure out an accurate way to simulate a high Q DCXO, to get a idea of its amplitude, frequency and phase noise.

But I found the amplitude depends heavily on how the oscillation is started, give different stimulus or initial condition, the amplitude simulated are hughly different.

Can some experts tell me, what would be the right way to find out oscillation swing?  Thanks in advance.
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wave
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Re: High Q crystal oscillator PSS and Pnoise
Reply #1 - Jul 25th, 2012, 1:15pm
 
rfmems wrote on Jul 25th, 2012, 5:15am:
I have been trying to figure out an accurate way to simulate a high Q DCXO, to get a idea of its amplitude, frequency and phase noise.

But I found the amplitude depends heavily on how the oscillation is started, give different stimulus or initial condition, the amplitude simulated are hughly different.


This doesn't make sense to me.  The *initial* amplitude may vary but should stabilize.  The final ampl. should be heavily dependent on your ESR and Cap values.

The other thing is its extremely painful (long) to simulate high Q values, so de-Q-ing, with modified series L-C values will greatly speed up transient simulations.

Wink
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rfmems
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Re: High Q crystal oscillator PSS and Pnoise
Reply #2 - Jul 26th, 2012, 1:17am
 
Normally Q of crystal is extremely high. Therefore, whatever kick you give to start the oscillation would long very slowly die out (meaning very long tstab). And the change is so slow that PSS might converge to different values with different kicks (ic or stimulus).

I tried HB, it seems much better.
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Re: High Q crystal oscillator PSS and Pnoise
Reply #3 - Jul 26th, 2012, 1:21am
 
Hi Wave, I do agree de-Qing would make simulation less painful. But you might get different swing/phase noise. Is that kind of change negligible?
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