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 injection locked oscillator phase noise simulation using pss+pnoise 

Last post Fri, May 23 2014 10:02 AM by Tawna. 8 replies.
Started by calp 15 Mar 2011 01:27 AM. Topic has 8 replies and 6178 views
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  • Tue, Mar 15 2011 1:27 AM

    • calp
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    • Points 40
    injection locked oscillator phase noise simulation using pss+pnoise Reply

    Hi all,

    I am designing an injection locked vco.  My simulation scenario for the phase noise is as follows:

    1. Run the vco without the injection signal for 2 microseconds ; let it setttle to the free running frequency; 

    2. Start the injection signal and observe the phase noise...

     Well, I need a periodic vsine source to generate the injection signal in the schematic; and this is the very source of an error in my pss simulation:

    " 'V0' is a periodic input signal, which is inconsistent with autonomous circuits. "

     this is what happens if I set cadence for phase noise simulation using the instructions given in the cadence Spectre manual.

    I know... the instructions are for a 'normal' vco; but I was hoping that it would work for my injection locking case as well.

     

    Question, as obvious it is by now :), how do we simulate the injection locked oscillator phase noise ?

    Is there a way to conceal the periodic voltage source in the circuit so as not to piss the pss off ?

     

    thanks,

    calp.

     

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    • Post Points: 35
  • Tue, Mar 15 2011 3:02 AM

    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply

    Hi Calp, If you have access to Cadence Online Support website then there is a solution on how to simulate such vco – http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11182082  

    For such oscillators you shouldn’t be using the Oscillator button in the PSS form as this is considered a driven circuit since it is driven by an injection source. That is the reason you are receiving the error message. Once you set the PSS form accordingly, set the tstab to 100 periods (and can also use the saveinit button to save the initial transient waveform before steady state). You should now be able to run the simulation. With Regards,

    Ashish

    • Post Points: 35
  • Tue, Mar 15 2011 3:19 AM

    • calp
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply

    thanks ashish.. looks like we are getting somewhere. :)

    Unfortunately, I don't have access to the link. Would you mind telling me more abt the pss/pnoise setup for these driven cct cases?

    vco free running freq : 106 MHz.

    injection freq: 111MHz.

     

    • Post Points: 5
  • Tue, Jun 21 2011 4:07 PM

    • Aprameya
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply
    Hello, I am not able to access the link. Could you kindly help?I am registered with the site. http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11182082 Thank you,
    • Post Points: 35
  • Tue, Jun 21 2011 4:13 PM

    • Tawna
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    • Snohomish, WA
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply

     Hi Aprameya,

     

    Please login to http://support.cadence.com and do a search on 11182082 .   That should take you to the solution that Ashish is referring to:

    11182082.

    I just verified this myself.

     

    best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 20
  • Wed, Jun 22 2011 8:42 AM

    • Aprameya
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply
    Got it, Thank you.
    • Post Points: 5
  • Fri, May 23 2014 2:14 AM

    • woodyrfic
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply
    hi~cap,I am facing the same problem you got,and unfortunately I don't have the access to the mentioned website for solution ,so could u kindly share the method please
    • Post Points: 5
  • Fri, May 23 2014 2:18 AM

    • woodyrfic
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply
    hi~aprameya,i am not able to access the mentioned website for solution ,so could u kindly share the solution please
    • Post Points: 20
  • Fri, May 23 2014 10:02 AM

    • Tawna
    • Top 25 Contributor
    • Joined on Thu, Jul 10 2008
    • Snohomish, WA
    • Posts 212
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    Re: injection locked oscillator phase noise simulation using pss+pnoise Reply

    Here is the article:

    When simulating an injection locked oscillator and looking at the startup waveform, you are looking for the point where the timing of the oscillator output is stable with reference to the injection source. Note that the amplitude must be at steady-state as well.

    When you set up your PSS analysis you:

    - Do NOT select the oscillator button.

    You are applying a signal (vsource) to your ring oscillator which causes the oscillator to oscillate at the injection frequency. Thus it is a driven circuit - as it is driven by the injection source. This is why you don't push the oscillator button on the PSS choosing analysis form. SpectreRF considers this a driven circuit and will error out if you select the oscillator button on the PSS choosing analyses form.

    - Set tstab to 100 periods.

    You want the circuit to be stabilized, i.e. you need to get it close enough to the final oscillation frequency so that PSS can converge. This will depend on the time constant of the circuit. A high Q oscillator will take a long time to settle. A ring oscillator is lower Q by definition, so it should not be as problematic.

    - Check the saveinit button.

    The waveforms for the initial transient before steady state are saved and you can view them with the results browser.

    - You may even want to try to run the circuit using transient analysis.

    Look at the oscillator output compared to the injection source. Look for variations in the timing of the oscillator output compared to the locking source. Hopefully, the circuit will settle fairly quickly.

    Now, once you can get PSS to successfully converge, you can look at things like pnoise jitter

    Best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 5
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Started by calp at 15 Mar 2011 01:27 AM. Topic has 8 replies.