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In PSS, direct plot of harmonic frequency gives single frequency - i need range!

Abdhkamal

Hi,
I'm simulating injection locked oscillator, i want to plot the relation between the control voltage and the output frequency.

I know that pss is not the best choice for that but i found this solution:

"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."

Then i set-up the pss as follows:

 

Finally, this what showed up to me.

It's a single frequency. I need to see how the frequency vary while changing the control voltage.
Any help?!

Thanks in advance.

Parents
  • Andrew Beckett

    Presumably if it's injection locked, the output frequency will be the frequency you're locking to? What influence has the control voltage?

    You didn't show the top part of the pss form so it's quite hard to know what you've really done here or are expecting. With a conventional VCO you'd sweep the control voltage and then the harmonic frequency UI would show something like:

    1   934.5M - 1.115G

    or something like that - and then  you'd get a curve. Presumably your frequency is not actually changing here...

    Andrew.

  • Abdhkamal
    in reply to Andrew Beckett

    Many thanks for your reply,
    here is the top part of pss form.

    While changing the control voltage the frequency should vary but the plot gives just single frequency.
    do sizes have an influence on pss operation?!

Reply
  • Abdhkamal
    in reply to Andrew Beckett

    Many thanks for your reply,
    here is the top part of pss form.

    While changing the control voltage the frequency should vary but the plot gives just single frequency.
    do sizes have an influence on pss operation?!

Children
  • Andrew Beckett
    in reply to Abdhkamal

    Well, you have the PSS set up as a driven circuit with a PSS fundamental of 1GHz. That means that the fundamental is 1GHz... and probably it would not converge if the circuit was not operating at 1GHz. I would expect that if it was injection locked, then the output frequency would be either 1GHz or a harmonic of 1GHz.

    If it's that your oscillator fails to lock to the injecting signal with particular control voltages, then you cannot simulate that with PSS because you'd have both a driving signal tone and an autonomous frequency in the same circuit - they would not have a common period and PSS cannot simulate that (you'd have to turn on oscillator mode and you'd then see that it will complain about the fixed frequency source). Note that the resulting "beat" frequency would be chaotic in that case as the common frequency between a free-running oscillator and a driven signal is a rather non-linear function of the two frequencies which is very sensitive to small changes.

    I don't know what  you mean "do sizes have an influence on pss operation?". If you mean device sizes, then yes - of course - it's a circuit simulator simulating your circuit...

    Regards,

    Andrew.

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