Series and Shunt S2P file of inductor or capacitor

[An_RF_Newbie]

Hello,
I need to get familiar with ADS software from basic questions up to a high level. and I will be grateful if you could help me.

1)I need to know why we have two different S2P files one for shunt and one for series.
2)How can I know which shunt or series S2P file is acceptable for each component in this circuit?(L1, C1,L2, C2)

Thanks

 

[volker@muehlhaus]

why we have two different S2P files one for shunt and one for series.

Who is "we", what S2P data do you refer to?

Many component manufacturers (like Murata) only provide the S2P file measured in series configuration. That is enough, and can be wired in ADS for shunt connection if necessary.

But just in general for measuring components: if you have very low impedance thru path, this might be more exact in measurement if you place it in shunt configuration. This way, the depth of a transmission zero from a shunt component can be evaluated and you can easily see if impedance is 0.1 Ohm or 0.2 Ohm. Such a value would be difficult to measure precisely in series configuration. Is this what your question was about?

 

[BigBoss]

General rule of thumb : If a component will be used in parallel mode, s-parameters may be parallel measured.
Otherwise series s-parameters are used.
It does not mean that "can absolutely not be used..". They can also be used but parasitic elements such as Pad capacitance to GND and Inductance to series etc. may vary some characteristics at Very High Frequencies.
Very High Frequencies start from5-6 GHz.
There is practically no difference @ 1GHz.\
For instance; There is a slight difference between two s-parameter dataset of Murata LQP03TN2N2B02 2.2nH,0.603) As you see;

 

[volker@muehlhaus]

But these are different use cases, of course the circuit will have different S-parameters when used in series and shunt configuration.

 

[An_RF_Newbie]

I really appreciate your help BigBoss and volker@muehlhaus.

I have tried to read many times to understand well your explanation and I need to clarify your comment much better.

for example in this configuration

I need to know your definition, for example, which components do you consider parallel or series?
(Can C3 or C2 be a parallel or series?)

Thanks

 

[volker@muehlhaus]

There is a lot of "smallprint" to get all the details corect for special case, but your question seems to be very basic?

You did not answer my question where you found S2P data measured in shunt configuration? They are somewhat special purpose/special interest. I think you worry about a non-issue here.

As written above: for general use, we prefer S2P model measured in series configuration because only that has series path and shunt elements on both sides. This is what you also find in ADS component libraries.

In circuit simulator we can wire that in series and shunt configuration - that is what I always do and it works just fine, with excellent agreement to measurements.

--- Updated May 23, 2022 ---

For instance; There is a slight difference between two s-parameter dataset of Murata LQP03TN2N2B02 2.2nH,0.603) As you see;

I'm till confused what you are trying to show here. An inductor shorted to ground behaves different from a series inductors? Yeah, true, what a surprise...

Of course we need to wire both S2P sets for the same effective configuration (=shunt) to evaluate any difference.

 

[BigBoss]

I'm till confused what you are trying to show here. An inductor shorted to ground behaves different from a series inductors? Yeah, true, what a surprise...

Of course we need to wire both S2P sets for the same effective configuration (=shunt) to evaluate any difference.

The question here is not to compare series and shunt configuration of an inductor. If you do the math of series to parallel conversion at a certain frequency by using supplied s-parameters the slight difference is coming from "additional" elements that should normally not be there. This small difference diverges by frequency.
This is my interpretation.

 

[volker@muehlhaus]

Can you upload the S2P files that you compared? I would like to do Pi model extraction of both, to see what configuration they describe.

To me, the SHUNT file looks as if it was measured in shunt configuration: almost short at DC, then getting high impedance at high frequencies so that we can see the 50 Ohm at port 2, with just some parasitic capacitance from the device.

The question is how much the series S2P file would be different if you connect it as shunt configuration.

Personally, I don't like the shunt S2P because nobody knows how much shunt path length/via inductance is included there. For accurate results, I prefer to include any actual shunt path in my EM Model for MY ACTUAL GEOMETRY, and then just plug in regular "series" S2P data across the pads.

 

[BigBoss]

OK, here are;

 

[volker@muehlhaus]

As expected: if we wire them both for shunt configuration, results are visually identical.
It is perfectly sufficient to use the series S2P data and wire that as needed, in series or to ground.