Calculate Q from s-parameters (RI Format)

[chiques]

Following up on the solution recommended by post 59511(https://www.edaboard.com/threads/how-to-calculate-the-q-factor-from-the-s-parameters.59511/).

I downloaded the series s-parameters for GCH1885C2A101JE01(https://ds.murata.co.jp/simsurfing/index.html?lcid=en-us).

I noticed they are already in R+jw format (according to the header)

Taking S11 at 100MHz I see:

1.0E8 0.02443218816516882 -0.15136178029257324

Therefore:

If I look at Murata’s SimSurf, the Q @ 100MHz should be 163.7.

Anybody know what I’m missing here?

 

[FvM]

S11 is unequal Z11

 

[chiques]

S11 is unequal Z11

Does this mean I should be working Z parameters instead S-Parameters?

 

[BigBoss]

Dr. Mühlhaus Consulting & Software GmbH » Inductor EM simulation: 1-port or 2-port?

Your RF EDA solution partner since 1993

muehlhaus.com

Look at the last part.

 

[chiques]

Dr. Mühlhaus Consulting & Software GmbH » Inductor EM simulation: 1-port or 2-port?

Your RF EDA solution partner since 1993

muehlhaus.com

Look at the last part.

Thanks, but this example uses an stoz() function. Do you know of any arithmetic examples?

 

[volker@muehlhaus]

Yes, you need to convert to Z-parameters or Y-parameters first.

S to h T Y Z Parameter Conversion

This table of conversion between various forms of 2-port electrical parameters is difficult to find, so once I finally located

www.rfcafe.com

The next question is what Q you want to calculate:
1) Q into port 1 with port 2 shorted
or
2) Q of the series element between ports 1 and 2 for differential excitation.

The first case is easy: impedance into port 1 with port 2 shorted is 1/Y11.
The second case would be the equation on my appnote linked above, typically used for RFIC inductors with symmetric excitation. For that you convert the 2-port data into the series 1-port between both terminals, and evaluate that differential impedance.

Good luck!
Volker

 

[FvM]

These are two-port s-parameters

!Murata Part Number: GCH1885C2A101JE01
!These Parameters are Measured in Series Mode Connection
! o--ll--o
!Port1 Port2
! o------o
!Operation Temp=25[degC], DC Bias Voltage=0[V]
!Freq. Start=100[MHz] Stop=8.5[GHz], 401[Steps]
!Data Generated on Jan 10, 2017
# Hz S RI R 50
!Freq.(Hz) S11(Real) S11(Imag) S21(Real) S21(Imag) S12(Real) S12(Imag) S22(Real) S22(Imag)
1.0E8 0.02443218816516882 -0.15136178029257324 0.9755678118348311 0.15136178029257324 0.9755678118348311 0.15136178029257324 0.02443218816516882 -0.15136178029257324

You can convert S-parameters to series impedance for the shown series connection

Zser = 2 Z0*(1 - S21)/S21

--- Updated Apr 22, 2022 ---

Using Matlab/Octave
>> s21 = 0.9755678118348311+0.15136178029257324i
s21 = 0.97557 + 0.15136i
>> z21 = 2*50*(1-s21)/s21
z21 = 0.094893 - 15.529972i
>> q=abs(imag(z21)/real(z21))
q = 163.66

 

[chiques]

These are two-port s-parameters


You can convert S-parameters to series impedance for the shown series connection

Zser = 2 Z0*(1 - S21)/S21

--- Updated Apr 22, 2022 ---

Using Matlab/Octave
>> s21 = 0.9755678118348311+0.15136178029257324i
s21 = 0.97557 + 0.15136i
>> z21 = 2*50*(1-s21)/s21
z21 = 0.094893 - 15.529972i
>> q=abs(imag(z21)/real(z21))
q = 163.66

Verified in MathCad as well. I checked 2 frequency points and the data checks out.
Thank you,