Talk:Scattering parameters

message: The page titled "s parameters" should probably be merged into this one.
I have just added quite a bit more from some of the classic references especially Pozar and Gonzalez and the infamous Agilent application notes. I hope this is a good start, the problem being avoiding rambling on for too long. Definitely should be merged with s parameters because this is just an abbreviation of the correct full descriptionChrisAngove 21:58, 11 April 2006 (UTC)
replies: text: The merge was a good idea. Needed to be done. --Thesilmarilion 18:38, 26 October 2006 (UTC)
thread_title: Merge [[s-parameters]] into [[scattering parameters]]

message: They are of course the same subject. People less familiar with RF engineering often ask what the S stands for so the better title is the full name with redirection from s-parameters. I have read S-parameters and added a few things I had overlooked in scattering parameters. Now please can we have some more comments from the huge numbers of electrical/RF engineers who must surely read this. ChrisAngove 20:39, 19 September 2006 (UTC)
replies: text: The merge was a good idea. Needed to be done. --Thesilmarilion 18:38, 26 October 2006 (UTC)
thread_title: Why I have merged [[s-parameters]] into [[scattering parameters]]

message: I think it would be useful to explain the difference between 'spatial' and 'temporal' phases in the General S-Parameter Matrix section. As the text stands at present the terms are used without explanation or reference. --Thesilmarilion 18:13, 26 October 2006 (UTC)
thread_title: Spatial/temporal phase

message: I have forced png rendering in the math tags using the \, characters to make the equations consistent. Also started to shorten sentences as the article is apparently somewhat long. May be possible to split it to say a definition and a measurement article.ChrisAngove 16:28, 1 January 2007 (UTC)
thread_title: math improvements, shortening

message: In the text S\cdot S^* \leq I was used, this is valid in most cases, since for a lossless reciprocal network S_{i,j} = S_{j,i}. However to be correct, the following should be used S^H\cdot S \leq I, where \{\}^H indicates the hermetian matrix (complex conjugate transpose). This way it will also be valid for non-reciprocal network, like circulators. Btw: The hermetian should be the first term.
Erik, 212.187.90.11 20:36, 19 February 2007 (UTC)
thread_title: Lossy/Lossless networks

message: I added the Agilent link at the bottom of the page as a hyper-ref in good faith. It's a commercial site, but the application note is general and well written. I think I'm missing something about Wikipedia's linking policy, but why was it removed as spam? Surely a link just saves a Google search? Thanks, Arthurtech 14:22, 5 May 2007 (UTC)
thread_title:  Agilent link 

message: Added a short section on 4-port S-parameters and differential s-parameters.  Correct and expand on as necessary.
DrillDriver (talk) 23:04, 13 February 2009 (UTC)
thread_title:  4-Port S-Parameters 

message: I suspect there is some confusion between the power S11 parameter and the voltage s11 parameter.  I rederived the whole thing.  If rho is the voltage transmission coefficient, then the scaled reflected power goes as rho^2, and the scaled transmitted power goes as (1-rho^2).  This would be if a short square-wave pulse for instance impacts the discontinuity.  See  "Advanced Engineering Electromagnetics", by Copnstantine A. Balanis p. 182 , where the field derivation is made (which assumes continuity of the E field, like voltage, and H-field, like current at the boundary) 82.166.221.34 (talk) 12:18, 15 March 2011 (UTC)
replies: text: It comes as a surprise to me that there are two kinds of S parameter.  I thought there was only one kind as measured by network analysers. SpinningSpark 19:14, 15 March 2011 (UTC)

text: That only works if Zref is the same at both ports, which is why that is not the definition of S-parameters. SpinningSpark 09:16, 31 May 2012 (UTC)
replies: text: This does need to be clarified -- I'm pretty sure most modern network analyzers (Aligent, etc) and textbooks (Pozar, etc) use the voltage definition of scattering parameters.  The way the article currently stands it introduces them as power ratios, but most of the formulas are for voltages which is probably confusing a lot of people.  a13ean (talk) 18:24, 18 October 2012 (UTC)

text: Not just clarified. It is completely wrong to say 'You get the same value no matter if you ratio the power waves b/a or the voltage waves', regardless of Zref. b/a is different to b^2/a^2. In addition, the article defines S-parameters as 'power ratios' but all the math shown assumes they are voltage ratios (which is correct).  — Preceding unsigned comment added by 75.140.140.189 (talk) 18:48, 22 March 2018 (UTC)
replies: text: The article does not define the S-parameters as 'power ratios', but as the ratio of [the amplitude of] 'power waves', i.e. as the ratios of square-roots-of-powers.  The article fails to make this clear - possibly out of concern for handling the arcane case where the port impedances are not taken to be real.  S-parameters are voltage ratios only between ports of equal impedance.  For ports of different impedance, there will be a different constant of proportionality between the voltage and the square root of the power at each one.  Consequently the s-parameter linking two ports of different impedance is not equal to the voltage transmission coefficient between them. --catslash (talk) 00:47, 23 March 2018 (UTC)

text: In my experience voltage scattering parameters are often used with transmission line (as opposed to waveguide) networks. When the port impedances are all the same, these are identical with "true" scattering parameters, but when the impedances differ, the matrix becomes asymmetric. Conversion between the two is simply a matter of dividing the columns and multiplying the rows (or vice-versa), by the square root of the impedance of the corresponding port. However, last time I looked, I could not find any mention of these voltage scattering parameters in any textbook, so they probably shouldn't appear in WP either. --catslash (talk) 21:51, 19 October 2012 (UTC)

text: What it is perhaps, is that we calculate a set of voltage reflection and transmission coefficients, and then informally in an abuse of terminology refer to these as scattering parameters or voltage scattering parameters for want of a more suitable term. --catslash (talk) 23:22, 19 October 2012 (UTC)
thread_title: Voltage and power parameters

message: You can measure S-parameters without a VNA, but I would agree that a VNA is usually the most appropite instrument for the job. But I fail to see the need to go into length about a VNA. A sentence or two should be sufficient. Instead we have needless information about VNA error correction, and systematic errors. That should be (and is), in the article about VNAs. The block diagram has been copied from that too. 
Surely the purpose of this should be to teach someone about S-parameters, not a VNA. For a VNA, there's a separate entry in Wikipedia. I don't see the need to copy a significant fraction of that. 
Much more useful would be a discussion of other ways of measuring S-parameters.  Drkirkby (talk) 21:46, 10 May 2017 (UTC)
thread_title:  Why so much detail about a Vector network analyzer?  

message: The article mentions the following:
Contrary to popular belief, the quantities are not measured in terms of power (except in now-obsolete six-port network analyzers).
Can someone elaborate on this, as I think it is a bit confusing without context? What kind of six-port network analyzer measures S-parameters as power, and why are six-port analyzers now obsolete?  — Preceding unsigned comment added by 185.34.132.200 (talk) 08:16, 3 June 2022 (UTC)
thread_title:  Elaboration on measurement unit and six-port network analyzers