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 Phase noise sensitivity to tstab 

Last post Tue, May 4 2010 5:18 AM by Andrew Beckett. 2 replies.
Started by Soner 03 May 2010 08:48 PM. Topic has 2 replies and 2099 views
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  • Mon, May 3 2010 8:48 PM

    • Soner
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    • Joined on Mon, Apr 7 2014
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    • Points 295
    Phase noise sensitivity to tstab Reply

    Hi,

    I am simulating a ~25GHz LC oscillator using harmonic balance and pnoise, then calculating the phase noise at 10MHz offset (this offset is added as a specific point to pnoise). Even with the most aggressive accuracy settings (harm=40,steadyratio=1e-3,reltol=1e-6,vabstol=1e-9,iabstol=1e-12), the phase noise measurements are extremely sensitive to tstab. More specifically, the measurements are sensitive to where the oscillation begins.

    Please correct me if I am wrong BUT if I want to sweep temperature or do Monte Carlo, this initial phase will vary and add +/-0.25dBc numerical noise to my results.

    I attached to waveforms to show the problem. Figure #1 shows thelast cycles of initial transient simulation while Figure #2 shows the phase noise measurements. As you can see the measurements for 5nsec and 5.3nsec are close since the oscillations for these begin with a very similar phase. By the way, I am usingSpectre Version 7.1.1.317.isr19

     


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  • Mon, May 3 2010 8:49 PM

    • Soner
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    • Joined on Mon, Apr 7 2014
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    • Points 295
    Re: Phase noise sensitivity to tstab Reply

     Here is the second waveform.


    • Post Points: 20
  • Tue, May 4 2010 5:18 AM

    Re: Phase noise sensitivity to tstab Reply

    I would suggest contacting Customer Support on this - it will probably need taking a look at your setup in more detail. It might just need a longer tstab, but it's hard to tell without seeing the circuit and doing some experiments.

    Regards,

    Andrew.

    • Post Points: 5
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Started by Soner at 03 May 2010 08:48 PM. Topic has 2 replies.