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PSS predicts a wrong oscillating frequency !!! (Read 3356 times)

Alez

Guest

PSS predicts a wrong oscillating frequency !!!
Apr 06^th, 2005, 11:18pm

Hi all,

seems to have many problems from VCO simulation Shocked

I'm simulating a VCO and I found an error from PSS.

From my simulation, in transient analysis, I found that

the VCO oscillates at 2.8 GHz (by measuring the period

of the output waveform). But from PSS, it shows that

the oscillating frequency is 3.5 GHz !!! How come ???

I tried to set many different "tstab" and different time

interval (tstart tstop) in transient simulation, but PSS

always shows 3.5 GHz !!

Could anyone explain me about this problem and how

to solve it,

Thank you all in advance,

Alez

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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: PSS predicts a wrong oscillating frequency !!! Reply #1 - Apr 7^th, 2005, 1:31pm Please don't post the same question in multiple fora - it makes it harder to keep track of. I responded to this in the RF Design Forum. I suggest anyone else does so there, since it's been started there. Regards, Andrew.
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Alez Guest	Re: PSS predicts a wrong oscillating frequency !!! Reply #2 - Apr 8^th, 2005, 12:17am Andrew, not sure what you mentioned. You mean I also posted in this question in the RF Design forum .... strange ! I think I only posted it here ?? If I were wrong, meaning I did some mistake Could you bring me my question in the RF Design forum Thanks, Alez
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Andrew Beckett

Senior Fellow

Offline

Life, don't talk to
me about Life...

Posts: 1742
Bracknell, UK

Re: PSS predicts a wrong oscillating frequency !!!
Reply #3 - Apr 8^th, 2005, 6:20am

Hi Alez,

My apologies. A very similar question was posted by someone else, and I assumed it was the same person.

I should try being awake when I post...

One problem might be what I described there:

http://www.designers-guide.org/Forum/?board=rfdesign;action=display;num=11128202...

Another problem might be that when you're looking at the output waveform, I assume you're looking at the initial transient, or a separate transient run. What may happen is that this is not the final, settled, frequency.

Remember that PSS accellerates settling, and so it may be that you need to run a very long transient to see it settling on 3.5GHz.

Regards,

Andrew

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