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ymax on a waveform family

ZoltanT

Hi Everyone,

I've had some nested sweeps in spectre, which resulted in waveforms families in OCEAN. ymax() does not work on some of my waveform families, but works on other ones. What could cause it? Where lays the difference? A waveform, actually any number series has to have a maximum value. I see no ambiguity here. 

What I expect: ymax takes the maximum Y value of each waveforms in the family, and it returns another waveform family which has one variable less than the original because the X-axis variable has been eliminated.

Is there any way to debug it, or even better to avoid this issue?

Thanks,

Zoltan

Parents
  • Andrew Beckett

    Hi Zoltan,

    That's how I'd expect it to behave. When you say it "does not work", how does it not work? What goes wrong? What version are you using? Some details of the problem might help to narrow it down...

    Regards,

    Andrew.

  • ZoltanT
    in reply to Andrew Beckett

    Hi Andrew,

    Sorry, for being unspecific. Sometimes I do not notice that I missed something out. ymax() returns nil in my case for some waveforms, but not for others. Below it gives nil.

    ocean> Vgain
    srrWave:0x294ee440
    ocean> ymax(Vgain)
    nil
    ocean> type(Vgain)
    other
    ocean> famIsFamily(Vgain)
    t

    But here it works as I expect him to work:

    ocean> Id0
    srrWave:0x294ed350
    ocean> ymax(Id0)
    srrWave:0x294efbc0
    ocean> famIsFamily(ymax(Id0))
    t

    The definitions:

    Vgain = v("d" ?result "sw_b_ac_gain-sweep")
    Id0 = -i("VD_DC:p" ?result "dc")

    I haven't seen any strong pattern, except that if one signal does not work for an analysis, than others might also not, but it is not analysis type dependent, i.e. one ac analysis is good, but the next one isn't.

    Is there any way I can debug this?

    Thanks,

    Zoltan

    Ps: I use ICADV 12.2-64b.500.7

  • Andrew Beckett
    in reply to ZoltanT

    Hi Zoltan,

    In this case it's because the results from an ac analysis are complex values - you get a complex number (representing the real and imaginary part) versus frequency, with a surrounding sweep around that in your case. You can't take the ymax of a complex-numbered waveform - you have to transform it to a simple value versus frequency instead. So you should be able to do:

    ymax(mag(Vgain))

    or

    ymax(db20(Vgain))

    Those should work fine. Not sure if there are other situations, but this will certainly be the reason in this case.

    Regards,

    Andrew.

Reply
  • Andrew Beckett
    in reply to ZoltanT

    Hi Zoltan,

    In this case it's because the results from an ac analysis are complex values - you get a complex number (representing the real and imaginary part) versus frequency, with a surrounding sweep around that in your case. You can't take the ymax of a complex-numbered waveform - you have to transform it to a simple value versus frequency instead. So you should be able to do:

    ymax(mag(Vgain))

    or

    ymax(db20(Vgain))

    Those should work fine. Not sure if there are other situations, but this will certainly be the reason in this case.

    Regards,

    Andrew.

Children
  • ZoltanT
    in reply to Andrew Beckett

    Thanks, Andrew! This was the problem. I am always  forgetting that, because the magnitude is plotted if nothing else is specified. It is not a bug, but a feature Slight smile

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