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Why PSS gives OScillation to Free Running VCO without any initial condition but NOT transient ?

RFStuff

Dear All,

I simulated a LC oscillator in PSS in Oscillator mode even if I have not given any initial condition (Convergence Aid).

While if I run the same oscillator in TRAN  without any initial condition it never oscillates.

Could anybody please tell me what is the reason behind this ?

Kind Regards,

Parents

  • Almost certainly this is because the default option when enabling oscillator mode in PSS is "Calculate initial conditions (ic) automatically":

    I don't know which IC subversion you're using but this is from IC616 (recent ISR) - it's been there for a while though. Before that it use to be called something like "use linear osc ic" or something helpful like that. It's a mode that computes the initial condition for you for oscillators.

    This is also available for transient, but since transient doesn't know that it's an oscillator - and a linear oscillator at that - you have to tell it. Again, from the transient options form in IC616 ISR14:

    If you click on the Calculate ic automatically "yes", you can then specify the estimated frequency.

    If you're stuck with an older version of the IC environment (but are using an MMSIM version from MMSIM12.1 onwards), then you can add the relevant parameters in manually, via the additionalParams field on the Misc tab of the transient options. For example: linearic=yes oscfreq=2G


    Regards,

    Andrew.

Reply

  • Almost certainly this is because the default option when enabling oscillator mode in PSS is "Calculate initial conditions (ic) automatically":

    I don't know which IC subversion you're using but this is from IC616 (recent ISR) - it's been there for a while though. Before that it use to be called something like "use linear osc ic" or something helpful like that. It's a mode that computes the initial condition for you for oscillators.

    This is also available for transient, but since transient doesn't know that it's an oscillator - and a linear oscillator at that - you have to tell it. Again, from the transient options form in IC616 ISR14:

    If you click on the Calculate ic automatically "yes", you can then specify the estimated frequency.

    If you're stuck with an older version of the IC environment (but are using an MMSIM version from MMSIM12.1 onwards), then you can add the relevant parameters in manually, via the additionalParams field on the Misc tab of the transient options. For example: linearic=yes oscfreq=2G


    Regards,

    Andrew.

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