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Using "cross" function (or an equivalent) in AC sim

I have an AC sim, with a Design Variable Sweep at a chosen frequency.
As the Variable is swept, I get a change in the AC waveform that I'm monitoring (which is as expected).
If I plot the waveform, it shows the ac voltage in y-axis, and the Swept Design Variable in the x-axis.

To this waveform, I want to apply the cross() to extract the x-axis point at which the function crosses a value.
So: cross(VF("/LPFOUT") 750m 1 "either" nil nil nil )
... to find the value of the Design Variable for which VF("/LPFOUT") crosses 750mV.

However, when I do this, I get "expression evaluation failed" as message.
I have successfully used this method for a DC Analysis sweep, so I know it works for VS signals.

Therefore:
1) Does the cross function work for AC (VF) signals?
2) If not, is there another way I can achieve what I need - which is to extract the value of my variable at which the ac signal crosses a threshold?

Looking forward to a response!

PS: Using Virtuoso 6.1.8.

Andrew Beckett over 4 years ago

Use: cross(mag(VF("/LPFOUT") 750m 1 "either" nil nil nil ))

The VF function returns a complex waveform (real/imaginary versus frequency) which is masked by the fact that when you plot it, it automatically converts it to the magnitude. However, you can do real(VF(...)), phase(VF(...)), db20(VF(...)), so it's actually complex.

That should fix it.

Andrew
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rushil over 4 years ago in reply to Andrew Beckett

Thank you very much Andrew, for the quick solution!
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