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Help in HB Simulation in an autonomous circuit with driving signal input.

Abdhkamal

Hi,

I'm simulating an oscillator with a source input to kick-start the oscillation. I tried to plot the the frequency of the output signal Vs. the control voltage. But I have read several posts saying that it couldn't be done with PSS anlaysis. Instead, it could be done using harmonic balanced simulation (HB) as it has "Semi-autonomous" mode.
I have tried HB analysis several times but there was an error :

No convergence achieved with the minimum time step specified.  Last acceptable solution computed at  0s. How to overcome this error?.

Now, knowing that the circuit works in the range [1-4 GHz] how to set-up the harmonic balance analysis correctly?



I'm using virtuoso 6.1.7
hope anyone could help me.
thanks.

  • Andrew Beckett

    Normally you wouldn't use semi-autonomous harmonic balance to kick-start the oscillator. This is used to investigate the effects of intermodulation of the driven signal with the autonomous oscillator - during the initialisation the driven signal may not even be present, so I don't think it would help.

    Normally any "kick" source wouldn't need to be periodic - you'd either define a pulse without a period, or a PWL source (again without a period). Both shooting and harmonic balance would then simulate both situations in the time domain until (at least) past this non-periodic kick has finished - often you'll want additional tstab time to allow the oscillation to grow.

    So the first thing is to make sure you can get the oscillator to start (save the initial transient, or even just run a transient) - then hopefully the PSS (shooting or hb) or hb analysis is more likely to converge.

    Not much more I can suggest given the lack of specifics in your post (I think you tried to add a picture but there's not one in the post).

    Regards,

    Andrew.

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