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RLC Extraction from S-Parameter

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CPW_Enlighten

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Hi there,

I am facing similar problem RLC extraction from S-Parameter. I understand that the inductance of a simple RF MEMS switch is abt 7pH for a 80um wide armature over a 60um/100um/60um CPW. However when I extract it using Sonnet with the effective inductance formula, the value is about 30pH.

Can anyone please help to enlighten me on this issue?

Thanks in advance.
 

CPW_Enlighten said:
with the effective inductance formula
Click to expand...

The effective inductance equation

-1.0E9 * imag( 1 / arg1 ) / ( TWO_PI * FREQ )

converts the series reactance into an effective inductance value. If you have an L-C parallel circuit, the calculated value increases with frequency and peaks at the resonance frequency.

If you check the effective inductance curve over frequency, do you get the expected inductance at low frequency (towards DC)?

You can also try the lumped Pi model extraction: Output > Pi-Model File

Best regards
Volker
 

Hi Volker,


I have tried doing that but the values I got was abt 60pH toward DC and getting abt 30pH for frequency >> resonant frequecy from the graphical method as well as the pi model extraction method.

This analysis is for a capacitive shunt MEMS switch.
 

Hello again,

then the difference in inductance must have a real, physical background.

My best guess, with having seen your model and port setup, is that you have significant inductance in the ground return path of your model. Inductance is always for a closed loop, so the result includes both the "signal" path through the MEMS switch AND the return path from port 1 ground to port 2 ground. Closed loop!

This ground return issue is described here, starting at page 41:
**broken link removed**

Maybe you can post a screenshot of the port configuration, or send this to Sonnet support?

Best regards
Volker
 

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