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# Cadence simulate ring oscillator's output in frequency domain (continuous wave)

Last post Wed, Jan 2 2013 6:12 AM by Andrew Beckett. 3 replies.
 Started by chiphead 25 Nov 2012 07:59 AM. Topic has 3 replies and 1648 views
• #### Sun, Nov 25 2012 7:59 AM

• Joined on Sun, Nov 25 2012
• Posts 2
• Points 40
Cadence simulate ring oscillator's output in frequency domain (continuous wave)
 Hi,Could anyone please help me with this question?  I need to simulate my ring oscillator's output in frequency domain, showing a continuous spectrum waveform as it can be seen from spectrum analyzer in the measurement (PSS->THD is not what I want).Then I can derive Q directly from it. If there is a detailed guide, that would be very helpful.Thanks a lot.
• Post Points: 20
• #### Mon, Nov 26 2012 4:04 AM

Re: Cadence simulate ring oscillator's output in frequency domain (continuous wave)
 I suspect you're wanting to see the noise included in the spectrum? If you simulated using PSS, then the only place frequencies can come from is harmonics of the fundamental frequency of the oscillator - so it doesn't matter that it is in discrete multiples of the oscillator frequency -there would be no frequencies in between. If noise is involved (which of course it will), you could simulate a pnoise analysis after pss, and see the noise output (although you will get separate PSS and noise outputs).Maybe you can clarify precisely what it is you're after?Regards,Andrew.
• Post Points: 20
• #### Mon, Nov 26 2012 7:51 AM

• Joined on Sun, Nov 25 2012
• Posts 2
• Points 40
Re: Cadence simulate ring oscillator's output in frequency domain (continuous wave)
 hi Andrew,thanks a lot for your reply.noise and discrete harmonics are not what i want. since i need to simulate the output signal bandwidth of close loop ring oscillator, the continuous spectrum plot is needed. could i simulate it using cadence? i have tried pss+pac, following pss oscillator setup(select plus and minus output net as output). but the pac could not recgonize the output net as the output. by the way, i did not put any port at output node since it is oscillator.
• Post Points: 20
• #### Wed, Jan 2 2013 6:12 AM

Re: Cadence simulate ring oscillator's output in frequency domain (continuous wave)
 It's still not clear to me what you're trying to do, so I would suggest contacting customer support so you can share the data with us and we can help you out with full visibility rather than having to guess.Regards,Andrew.
• Post Points: 5