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# Calculate Off Capacitance & On Resistance from S-Parameters

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#### infinite_gbps

##### Member level 3
Hi,

Is it possible to get these characteristics of a RF Switch if you have the 2-port s-parameters when the switch is open and closed?

If so, can someone provide the equations or link me to them?

Thanks.

#### pancho_hideboo

Convert {S11,S12,S21,S22} to {Y11,Y12,Y21,Y22}.

Evaluate
Gon=1/real(Y21) or 1/real(Y12)
and Coff=imag(Y21)/(2*pi*freq) or imag(Y12)/(2*pi*freq)

tony_lth

### tony_lth

Points: 2

#### kayaoo

##### Member level 5
In @DS, there is a tool "spice model generator". It can generate the spice model.

tony_lth

### tony_lth

Points: 2

#### infinite_gbps

##### Member level 3
Dumb question .... the Ron is the inverse of Gon ... correct?

#### pancho_hideboo

Dumb question .... the Ron is the inverse of Gon ... correct?
Yes, correct.

#### infinite_gbps

##### Member level 3
Yes, correct.

I figured as much but was just making sure.

Is it possible to get mutual inductance between two coils using 2-port s-parameters? Instead of dividing by 2*pi*f should I multiply? If I'm wrong then what is the proper procedure?

Thanks for the help.

#### pancho_hideboo

Is it possible to get mutual inductance between two coils using 2-port s-parameters?
There is no reason why we can't evaluate mutual inductance from 2-port S-parameters.

V1=j*omega*L1*I1 + j*omega*M12*I2
V2=j*omega*M21*I1 + j*omega*L2*I2

Z12=j*omega*M12
Z21=j*omega*M21

Instead of dividing by 2*pi*f should I multiply?
I can't understand what on earth you want to mean at all.

Last edited:

#### infinite_gbps

##### Member level 3
I can't understand what on earth you want to do at all.

I was thinking about impedance calculations and inductance. I probably mixed it all up. Forget I said that.

I have two coils that are in close proximity to each other and one port is on one coil and the other port (port 2) is on the other coil. I got 2-port S-parameters. Is there a similar way to calculate the mutual inductance between the two coils using the 2-port s-parameters?

#### pancho_hideboo

there a similar way to calculate the mutual inductance between the two coils using the 2-port s-parameters?
Again, there is no reason why we can't evaluate mutual inductance from 2-port S-parameters.

Surely read linear circuit theory text book for very beginner.

Last edited:
grit_fire

Points: 2