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How to get LC tank resonator Q from oneport S-parms?

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wizardz

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tank resonator

I measured some parallel connected LC tanks and get one-port S parameters with 50 Ohm port impedance.
I want to extract Q value of LC tanks, but I think the one-port S-params I get is loaded S parameters. From the measurement data, the |Z11| is approximately 50Ohm(equals port impedance) and the 20log|S21| is not sharp.

Is there any ways to get the unloaded S-params so that i can get the Q?
What is definition of Q on the 20log(|S11|) plot or on the |Z11| plot, 3dB fractional bandwidth?

Thankyou!
 

waseemsh

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i think u must power up the circuit and connect the output on the spectrum analyzer and check its resonant frequency(fo) and bandwidth between "3 db points" your unloaded Q will be fo/BW.

But this case emloys your phase center (0 deg phase) is near the fo.
 

wizardz

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what do you mean by "power up"?
what kind of signal do i get on spectrum analyzer, S21-frequency?

waseemsh said:
i think u must power up the circuit and connect the output on the spectrum analyzer and check its resonant frequency(fo) and bandwidth between "3 db points" your unloaded Q will be fo/BW.

But this case emloys your phase center (0 deg phase) is near the fo.
 

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