# [SOLVED]calculate mutual inductance from two close coil from s parameters

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#### grit_fire

##### Member level 5
calculate mutual inductance of two close coils from s parameters

Hi, all,

I have two coil inductors placed with one above the other. I managed to obtain the s-parameters s11, s12, s21 and s22 using ADS momentum.

Does anyone know how to calculate the mutual inductance between them using the s-parameters obtained?

Thanks!!

#### streamlet

##### Full Member level 3
Re: calculate mutual inductance of two close coils from s parameters

First transform the S-parameter to Z-parameter.
Then mutual inductance=imag(Z12)/omega.

#### grit_fire

##### Member level 5
Re: calculate mutual inductance of two close coils from s parameters

First transform the S-parameter to Z-parameter.
Then mutual inductance=imag(Z12)/omega.
Hi, thanks for reply! Now I got it.

Conversion from s parameter to z parameter requires the Zo value, which is the characteristic impedance of transmission line? I am using ADS momentum layout to draw my two inductors. Could you tell me how do I know the Zo value? Or is it just 50ohm no matter what?

Thank you for the help!

#### streamlet

##### Full Member level 3
Re: calculate mutual inductance of two close coils from s parameters

The transformation from S-parameter to Z-parameter depends on Z0, you can refer to Tab. 4.2 in Pozar's book -- Microwave engineering.

As for the Z0 used in ADS momentum, it is believed to be 50 ohm which is the default value if you haven't changed that when exporting S-parameter.

Hi, thanks for reply! Now I got it.

Conversion from s parameter to z parameter requires the Zo value, which is the characteristic impedance of transmission line? I am using ADS momentum layout to draw my two inductors. Could you tell me how do I know the Zo value? Or is it just 50ohm no matter what?

Thank you for the help!

grit_fire

### grit_fire

points: 2

#### grit_fire

##### Member level 5
Re: calculate mutual inductance of two close coils from s parameters

Thank you! I really appreciate your help!

The transformation from S-parameter to Z-parameter depends on Z0, you can refer to Tab. 4.2 in Pozar's book -- Microwave engineering.

As for the Z0 used in ADS momentum, it is believed to be 50 ohm which is the default value if you haven't changed that when exporting S-parameter.

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