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How to put X-axis into a variable related to the sweeping variable rather than the sweeping variable itself (by default) in the Cadence Waveform?

Alex Liao

Hi All,

I have a question related to Cadence waveform....After i do the DC sweep simulation, I want to plot 

gm/id VS id/(w/l)


Eg: If i sweep W (width) of a device and now i only can plot gm/Id vs W in a straightforward way as the W is the sweeping variable default set as the X-axis.

When w changes, the id changes. So what I want is like sweeping w, rather putting it(w) directly into X-axis, put a function [ f(w)=id/(w/l) ] into X-axis (no bother to Y-axis).



Any suggestions??

regards,

Alex.

  • Alex,

    Two ways. One is to plot the function you want as the y-axis and the function you want as the x-axis - and then do Right Mouse Button over the x-axis on the graph and then you can select which signal you want as the x-axis.

    Alternatively you can use the waveVsWave function in the calculator (it's only there in later IC616 ISRs though).

    Regards,

    Andrew.

  • Hey Andrew,

    Thanks. When I do Mouse Right Click, I tried the "Y Vs Y..." choice and it actually meet my requirement.

    I also checked my Cadence, It is Virtuoso 6.1.6. I do not know what ISRs is and if I am using an ISRs version or not. But I did not find the waveVsWave function in the calculator. In the All Function Panel, the last function in 'V' section is 'vtime' and the next one is 'x**2‘. No funtion starts with 'W'.

    Regards,

    Alex

  • Hi Alex,

    The subversion you're using can be found under Help->About in the CIW (or indeed most windows in Virtuoso). waveVsWave got added to the calculator in (I think) ISR12 - IC6.1.6.500.12. The function exists prior to that, but it wasn't in the calculator.

    Anyway, glad the YvsY does what you want!

    Regards,

    Andrew.

  • Hey Andrew,

    I have checked it again, the subversion is IC6.1.6.500.9. (Guess it is called ISR9). According to what you said, the waveVsWave should exist in the Cadence Tool, but just not added into the calculator (guess subversion 12 is later than subversion 9 and that's why I did not find it in the calculator in my subversion). So where can I find and use this waveVsWave function in the Tool? Just want to know more about Cadence, an alternative way to do things.

    Thanks,

    Alex. 

  • Alex,

    In the ViVA window (in fact any window), use Help->Contents. In the resulting window, use View->Show Navigation, and then in the search box on the left (just above where it says "Search & View Options") search for waveVsWave and you'll find the documentation on the function. You can then use this function in the calculator buffer (you'll have to type it in):

    waveVsWave(?y expr1 ?x expr2)

    where expr1 and expr2 are the calculator expressions for the x and y axes.

    Regards,

    Andrew.

  • Hey Andrew,

    I have done what you said and it worked as well as the Y Vs Y....

    The results are exact the same in terms of the shape of the waveform.

    I'll discuss with you on a related problem in another thread.

    Thank you,

    Alex

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