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One-port to two-port s-parameter conversion

buin

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Hi there,
Suppose that I have a one-port s-parameter measurement (or simulation) data of a transmission line with one side terminated open, what is the best way to estimate its two-port s-parameters?
byoung
 

volker@muehlhaus

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It is not possible to calculate the 2-port S-parameters from that single 1-port data.

If you are sure that your line is well matched (S11 close to zero), a rough estimate is that unterminated S11 is two times the lines insertion loss (S21)
 

FvM

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Generally it's not possible. You can try to fit a transmission line model with limited number of parameters (e.g. Z0, electrical length, attenuation) to the S11 measurement.
 

buin

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It is not possible to calculate the 2-port S-parameters from that single 1-port data.

If you are sure that your line is well matched (S11 close to zero), a rough estimate is that unterminated S11 is two times the lines insertion loss (S21)
Thanks for the comment! Yes, I agree to your comment. However, recently I learned that Keysight has a software that can do the estimation. Basically, it is to provide a simple way for deembedding of EVB traces. All you need is just one-port s-parameter data with one side open. I took two-port data from one-port measurement one using the tool, and then compared it with (original) two-port measurement data, and it is not perfect, but they are reasonably well matched, which surprised me. :-o I am wondering about the principle of work.
 

buin

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Generally it's not possible. You can try to fit a transmission line model with limited number of parameters (e.g. Z0, electrical length, attenuation) to the S11 measurement.
Hi FvM, thanks for your comment. I replied to Volker's comment, which can be the same feedback to you.
 

FvM

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As stated, it can work with a model based approach. You need to put in multiple s11 points to identify e.g Z0 and length. You can play around with circuit simulator and a transmission line model to see how the s11 curve depends on Z0 and length.
 

volker@muehlhaus

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However, recently I learned that Keysight has a software that can do the estimation.
Do you have more details? I am using Keysight ADS, but don't know what estimate you refer to?

edit: Do you mean the TDR front panel that allows to calculate line impedance from reflection using time domain transformation?
 

buin

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Do you have more details? I am using Keysight ADS, but don't know what estimate you refer to?

edit: Do you mean the TDR front panel that allows to calculate line impedance from reflection using time domain transformation?
Keysight's N19301B(PLTS) with N19305B AFR option can do. You can install the demo version for one month.
 

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