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Impedance Plot Data from S-Parameter File

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chiques

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Is it possible to get the impedance data from an s-parameter file?

In this example I'm using Part # GQM2195C2A100GB01

I'm using the s-data from SimSurf (https://ds.murata.co.jp/software/simsurfing/en-us/index.html#
Click on Monolithic Ceramic Capacitors

The S-Data is attached.

The plot I'm looking for is:
GQM2195C2A100GB01_impedance.png
 

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  • GQM2195C2A100GB01_series.zip
    15.6 KB · Views: 6

tony_lth

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In ADS, the normal way is import S2P file and simulate with Z parameter selected, then can plot with ADS data.
But your component is a Tan capacitor, it is nonsense to plot its impedance over frequency, say 1GHz.
 

chiques

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Hawaslsh

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I did notice that plotting S11 is the same plot as |Z|. I'm just not sure why.

The two are related to one another, its the reason why smith charts were created. A neat way to display both complex reflection and impedance. Although the impedance contours aren't as easy to imagine / use as the X-Y plot you want.

S11 = (Zcap - Zo) / ( Zcap + Zo), assuming a 1 port measurement with the cap as the load of course.

Not sure if that helps,
Sami
 

biff44

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if this is a capacitor, you have to realize that the impedance is a complex quantity. i.e. it has real ohms and imaginary reactance. it might be more useful to plot the real and imaginary part on different graphs.

what are you simulating, a series capacitor between two 50 ohm lines?

Note there is some sort of resonance around 4.5 GHz, either caused by the capacitance bulk dielectric acting like a waveguide, or the lead/parasitic inductance resonating with the capacitor.
 

chiques

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The two are related to one another, its the reason why smith charts were created. A neat way to display both complex reflection and impedance. Although the impedance contours aren't as easy to imagine / use as the X-Y plot you want.

S11 = (Zcap - Zo) / ( Zcap + Zo), assuming a 1 port measurement with the cap as the load of course.

Not sure if that helps,
Sami

I get this. But I need to get the Zcap from our VNA measurements.

- - - Updated - - -

if this is a capacitor, you have to realize that the impedance is a complex quantity. i.e. it has real ohms and imaginary reactance. it might be more useful to plot the real and imaginary part on different graphs.

what are you simulating, a series capacitor between two 50 ohm lines?

Note there is some sort of resonance around 4.5 GHz, either caused by the capacitance bulk dielectric acting like a waveguide, or the lead/parasitic inductance resonating with the capacitor.

No simulation, all VNA measurements in a series-thru configuration.

Yes, the 4.5 GHz is the parallel resonance frequency. From what I understand this is where the capacitor has maximum impedance (as opposed to the SRF which is minimum impedance.).
 

volker@muehlhaus

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But I need to get the Zcap from our VNA measurements.

If the cap is in series between the two ports, the first step is to convert the 2-port data into the differential series element (1-port)

Z = stoz(S)
Zdiff = Z(1,1) – Z(1,2) – Z(2,1) + Z(2,2)

This Zdiff is the capacitor's impedance, similar to your plot.
 

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