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Q-factor and Inductance Calculation from S11 parameter in 1 port mode

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maximillian

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Hello all,
I would like to calculate the Q-factor and Inductance of my inductor from the S-Parameters(in dB) which I got from the network analyzer. Could anyone help me with this?
 

I'm not sure if this is realistic (or in any case, very accurate) with a one port setup. As the above linked article implies, you need to obtain a precise termination impedance, which is not easy. Can you do a two-port setup?
 

If the inductor characteristic impedance |ωL| is e.g. in a 5 to 500 ohm range, this can work well.
 

1-port impedance load is 50 Ohm's

Qfac is straight forward calculation of XL/R i.e. reactive component divided by resistive value.
SRF depends on fixture stray capacitance and Choke self capacitance.

At resonance, return loss has negative peak where maximum the Q= f/BW for BW = width of f band for delta 3dB of the resonance band from peak.

But this includes Q of parasitic C, so Q result of C must be much better than L to get good results.

1/Q=1/QL + 1/Qc. such that 1/Q becomes 1/QL.

Hi Q caps depend on f and desired Q , such as mica or plastic caps to measure Q of L at desired operating f.
 

I used this set to measure low value inductors. I calibrated the VNA with these to 1 GHz using an S-Parameter test set set to S11 and using the Smith chart overlay. The VNA would also give you the self-resonante frequency of the inductor and also the real part, which you could use to get a good idea of the component Q. The boards measure 1.5" square and the connector is an SMA. They served me well.

https://obrazki.elektroda.pl/7541423900_1470156910.jpg

https://obrazki.elektroda.pl/2379513100_1470156911.jpg

https://obrazki.elektroda.pl/2037133200_1470156913.jpg

https://obrazki.elektroda.pl/1458046300_1470156914.jpg
 

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