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how to calculate resistance and capacitance from s11 format data( from Frequency, magnitude and phase angle)

Question asked by srini on Jul 25, 2017
Latest reply on Jul 28, 2017 by srini

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I am using E5061B network analyser.

1. I am getting S11 data from analyser

2. How to calculate the resistance and capacitance from s11 data?

3. In s11 data..we have 3 columns with data

4.First Column : frequency

5. second Column : Magnitude

6. third Column : Phase angle

7. How to calculate the resistance and capacitance from above values.

Kindly help

Thank you.

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drkirkby Jul 27, 2017 9:29 AM
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This would be my approach.

I assume you are reading a Touchstone file, given you mention the 3 columns.

Let S11_dB be the magnitude in dB (2nd column)
1. Convert the magnitude in dB (S11_dB) so its no longer in dB, but you have the magnitude of S11. For that use |S11| = 10^(S11_dB/20). So that gives you a polar form of the complex number S11.
2. Convert the polar form to rectangular form.
3. The reflection coefficient S11 is related to the load impedance ZL by the equation ZL=Zo*(1+S11)/(1-S11), where Zo will be 50 Ohms.
4. The real part of ZL is the series resistance.
5. The imaginary part is the series reactance. If the imaginary part is positive, then its an inducive, if its zero its a pure resistance, and if the imaginary part is negative, then its capacitive.
6. Use the usual formula to convert reactance to capacitance or inductance.
Dave
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- srini @ drkirkby on Jul 28, 2017 2:04 AM
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  Dear Dave,
  
  Fantastic.
  
  Thank you very much.
  
  It was wonderful explanation and it is to the point.
  
  your answer solved our issues.
  
  Continue this valuable work..someone like us will be benefited in
  scientific community.
  
  Thank you very much for your valuable time to write this response.
  
  Best Regards
  
  Srinivasan
  
  On Thu, Jul 27, 2017 at 6:30 PM, drkirkby <moderator_forums@keysight.com>
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