Help me understand and ADS equation for simulating C varactor response

Hi all,
I followed one document about the oscillator example to simulate C varactor response with ADS,An equation :C_varator1=-1/(2*pi*freq[0,0]*imag(Z11[0])) i can not understand and can not find in the help document:what is [0,0] in freq[0,0] and [0] in Z11[0]?and what is the defference between freq and freq[0.0],Z(1,1)[0] and Z11[0]?
Anyone kindly help me and share me some documents about the topic?Thanks

Hi

Check www.rfic.co.uk.

i checked a manual I have and I could not find anything useful there.\

The website is amazing though.

Cheers

I suppose you tried the example project MMIC_OSc.prj and Varactor_test Schematic where it has that equation.

What he does there is for a certain frequency he varies the voltage on varactor and measures the impedance from the reflection coefficient and then calculates the C.

The simulation therefore has 2 parameters , 1 is frequency and the other is Voltage, therefore every output of your S-parameters simulation is an array of [Voltage,freq]. If you click on the equation at the data display you can see the outputs and there is a button for Variable info, there you find from how many parameters your variable depends.

Another thing to note is that ADS always starts to count from 0, so if the frequency array has 41 points of voltage and 1 point of frequency, so the first point will be freq[0,0] , the 2nd point will be freq[1,0] and so on. In your case freq[1,0] is the same like freq[0,0] since you simulate in a single frequency. The formula the ADS tutorial gives tries to generalize a bit.

As far about Z11[0] and Z(1,1)[0], they are the same thing , u can use both.

basically in the array you have 2 variables, 1 is the Dependant and the other the independent etc. The independent is the frequency therefore the Z11[0] means give me the input impedance of all the Dependant voltage variables at the independent frequency variable 0.

Another way to write the same thing is Z11[::,0] which means give me all the outputs of Z11 at the frequency point 0

I just hope I have wrote them in an understandable way and actually helped you.

Thanks,it is very helpful to me.

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