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Capacitance vs frequency

Question asked by mingal on Nov 6, 2006
Latest reply on Nov 7, 2006 by mingal

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This should have been simple.

I want to plot capacitance as a funciton of frequency for a varactor model. When I try

C=(-1/2/PI/im(Linear1_Data.ZIN1)/Linear1_Data.F)

I get a square matrix instead of an array.

Please help?

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pkarasev Nov 6, 2006 12:06 PM
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Hi Mark,

There's a section in the user's manual under "Using Equations" -> "Debugging Tips" that addresses this. (You need to use the ./ operator to perform element-wise division, not a matrix divide with /)

So in general to do operations like this you'd have:

dataOne.Var1./dataTwo.Var2
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mingal Nov 7, 2006 1:38 AM
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Thanks, Peter. That's a tough one to find in the index, eh?
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mingal Nov 7, 2006 6:32 AM
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OK, cool! I used the expression:

C=(-1e18/2/PI/im(Linear1_Data.ZIN1)./Linear1_Data.F)

But not cool! Now the displayed units are MHz!

Can I either change the units or turn them off, or do I have to just plain ignore them?
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mingal Nov 7, 2006 6:37 AM
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I think part of the problem is that ZIN1 in the Dataset has available dimensions, "dB, magnitude," and so on, not "Ohms." Still,

1/<magnitude>/<frequency>

should not return frequency, but time.
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pkarasev Nov 7, 2006 7:42 AM
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You can use

C=(1/2/PI/im(Filter1_Analysis_Data.ZIN1)./Filter1_Analysis_Data.F)

setunits("C","pF")

You don't need to use additional multipliers to try to manually convert units, just use the built-in setunits function that will take into account the units of vectors used in the calculation.
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mingal Nov 7, 2006 7:58 AM
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Worked!

8)

(Gotta go find this in the help section...)
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Capacitance vs frequency

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