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29th June 2007, 21:14 #1
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sparameter inductance
Hi,
I'm trying to determine the inductance and capacitance of chip inductors/capacitors at 12 GHz from the SParameters (S11 & S21) measured on an VNA. Does anyone know what equations/methods I should use to get these values. Thank you for your help!

29th June 2007, 21:14

29th June 2007, 22:27 #2
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capacitance from s parameters
1. Find an appropriate model including the most important parasitics
2. Find some good starting component values for the I/C and their parasitics
3. Optimize the component value and parasitics (preferrably automatically) to the Sparameters match the model as good as possible.
A good starting point for inductors would be the Spice models of the Coilcraft inductors. You should be able to find something similar for the caps, but usually a series RLC circuit works fine.
http://www.coilcraft.com/models.cfm
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2nd July 2007, 06:11 #3
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s parameter inductance
Hello asubraman,
Import or read your Spareameter file to any simulator (AWR MWO or Sonnet EM)
then plot the Y parameters Then use the following equation to get the Capacitance & Indutance values
Y11 = Im(Y(1,1))
C1=1.0E12 / ( 2 * _PI * _FREQ * ( 1 / Y11 ) )
Where
L1=1.0E9 * ( 1 / Y11 ) / ( 2 * _PI * _FREQ )
L1: Effective Inductance (in nH) of a series RL network
C1: Effective Capacitance (in pF) of a series RC network
_FREQ: is project frequencies in GHz
Note: Sonnet has direct measurement option for the above...
manju
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6th April 2010, 10:53 #4
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Re: Determining Inductance/Capacitance from SParameters
dear manju,
thank you so much for the above post, it really helped me. can u tell me whether in this case, the resistance would be Re(Z(1 1)) or Re(1/Y(1 1))?
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6th April 2010, 10:53

6th April 2010, 11:15 #5
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Determining Inductance/Capacitance from SParameters
both should be equal by theory.
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6th April 2010, 11:16 #6
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Re: Determining Inductance/Capacitance from SParameters
hello,
I hope this helps you...see the attached document...
manju
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6th April 2010, 11:16

9th April 2010, 12:58 #7
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Determining Inductance/Capacitance from SParameters
Dear Manju,
In the calculation of L1, the formula you have used.... is it 1/imag(Y(1 1)) or should it be imag(1/Y(1 1))? Please reply soon... Thanks so much!
Kas

9th April 2010, 13:43 #8
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Re: Determining Inductance/Capacitance from SParameters
Hello acekas,
it is imag(1/Y11)...
Also Note that on your query Resistance calculation;
If you are looking for the equivalent series resistance then
Z11 is only equal to 1/Y11 for a oneport (or if you short circuit port 2 device).
When you have a twoport, Y and Z are matrices and you cannot just take the reciprocal of each element in the matrix.
so whatever kspalla told was theoretically not true...
I hope this helps you...!!!
manju
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9th April 2010, 13:58 #9
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Determining Inductance/Capacitance from SParameters
Thanks Manju, yeah, that helped!
Regarding what you said about short circuiting port 2, can you please tell me how I can do that on cadence?
Further, isn't the expression imag(1/Y(1 1))... valid only for circuits with the second port shortcircuited? If not, I would appreciate it tremendously if you could throw some light on how we are arriving at the expression!
Thank you once again!
Kas

3rd August 2013, 07:17 #10
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