Talk:Smith chart

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What the heck is 'Rafay's Chart'? I can't find any evidence of anything with this name ever exisiting.


Could we see an example with some data filled in? --Phil | Talk 11:42, Apr 8, 2005 (UTC)


A Smith Chart is more specifically a nomogram than a graph. The nomogram page can let people know that a nomogram is a kind of graph.


I'd like to put back to old picture of the smith chart. the current one does not have enough numbers to be useful. Does anyone oppose reverting back to the old one?

I would like to see the old one. At the very least any diagram of a Smith Chart will do. A picture tells a thousand words. Piercetp 01:56, 20 April 2006 (UTC)
There's already a picture in the article. Afonso Silva 08:17, 20 April 2006 (UTC)
Must be new then. There was no one when I checked last time. Piercetp 23:05, 22 April 2006 (UTC)

Substantial Additions[edit]

I have added quite a bit plus some examples. I hope everything is relevant but there may be some repetition to tidy up. I think it could benefit some constant gain/NF circles and even some screen dumps from actual VNA measurements. I just can't get the equations visually consistent for some reason, they come out in all shapes and sizes and sometimes with little tags on the ends, I will study the math help a bit more and improve if nobody else does.

Also the following might be useful additions

Examples of Test Results Displayed on Smith Chart Formats Smith Charts region greater than unity (amplifier stability etc.) Noise Figure Circles, constant gain circles ChrisAngove 09:17, 8 October 2006 (UTC)

I have introduced a paper published in 1937 which may be an evidence for who invented the Smith chart. If I am licensed, I will upload possibly world's first "Smith chart".--Forestia net (talk) 19:05, 12 November 2010 (UTC)

GA on hold[edit]

Just a few points:

  • Headings should only have the first word capitalized (unless there is a proper noun of course). See WP:MOS
  • The lead section could perhaps be expanded to two paragraphs per WP:LEAD.
  • Don't have wikilinks in titles. (WP:MOS again :))
  • A lot more references are needed for criterion 2b.

And also:

  • Try to enforce the math either being in png format for consistency. (\, at the end of each <math> should be what's needed). It makes it nicer to read really.
  • Some of those redlinks might actually be mistyped wikilinks to other pages.

Otherwise it's a good article, although technical! CloudNine 22:15, 30 October 2006 (UTC)

Möbius transform[edit]

Mathematically speaking, the transform as applied in the Smith chart is a special case of a Möbius Transformation. There should be a reference somewhere. Troelspedersen 14:09, 13 November 2006 (UTC)

Improved equations[edit]

I have just added lots of 'force .png' tags to the TeX markup and they are more consistent at least. Also some improvements in the text flow, removal of excessive words etc.ChrisAngove 12:33, 25 December 2006 (UTC)

1st time questions[edit]

  1. distributed component = distributed element = is discussed in distributed element model?
  2. The Smith Chart is used with one frequency at a time so the temporal part of the phase () is fixed.[...] Why not ?
  3. As someone seeing the Smith chart the first time, it was quite hard to figure out where these points and regions are: center of the Smith chart (), and the unitary circumference circle.

Thank you for any help. --Abdull (talk) 11:29, 10 December 2007 (UTC)

Trivia[edit]

Has anyone ever noticed that the lines you draw on a Smith Chart seem to consistently conform to Imperial units: inches and grains?! I presume it's because Americans like using English traditional units in electronics as well. I just wondered whether this was by design or just a coincidence. —Preceding unsigned comment added by 144.32.126.12 (talk) 15:13, 1 May 2008 (UTC)

you are partially correct : Americans use imperial measurements for the physical sizes of electronics components ( eg 0805 sizes of surface mount components ) which often became default standards. but I have never heard of imperial units for capacitance, inductance, impedance etc which are all derived from the SI system of units. for some reason the values of capacitors and inductors are not spaced linealy, but this is simply tradition now. the lines on the smith chart seem ok to, if you start from unit impedance values and work backwards. other wise I am not sure I undertsand what you are talking about. 86.32.232.35 (talk) 17:24, 17 August 2009 (UTC)

Capitalization[edit]

When this article (but not the title) capitalized the topic as Smith Chart, I Googled the term and it seemed like sources were divided about 50-50 between "Smith Chart" and "Smith chart." I instigated the move to Smith Chart because it appeared a hell of a lot easier than changing the C's throughout the article to match the title Smith chart; since someone else has now done that conversion, I have no objection to leaving it at this title. But I do think if it were ascertained that "Smith Chart" was in fact the proper capitalization, WP:CAPS wouldn't prevent us from putting the article at that title; if there's a specific part of the guideline that says it would, please provide a link at least for my own curiousity. Propaniac (talk) 13:55, 12 September 2009 (UTC)

You did read the first sentence of WP:CAPS, right?
Convention: For page titles, always use lowercase after the first word, and do not capitalize second and subsequent words, unless the title is a proper noun.
You can't trust google statistics for correct capitalisation, spelling or grammar. If you don't believe me, try googling "transmition" in google books and see how many textbooks get that wrong. Then try it in google scholar and see how many scholarly papers have also got it wrong. 50-50 is nowhere near solid enough to override one of the few things the MOS treats as an absolute. If we followed google, we would have to move Rubik's cube to Rubik's Cube, Theory of relativity to Theory of Relativity and Ohm's law to Ohm's Law. All 50-50 or more in favour of capitalisation. SpinningSpark 18:03, 12 September 2009 (UTC)

What is "characteristic" and what is "normalized"?[edit]


I don't understand the difference between an "impedance" and it's "characteristic impedance". What does the word "characteristic" add to the meaning?
I don't understand what it means to be "normalized". This is not explained in any Wiki. Baruchatta (talk) 21:08, 16 November 2009 (UTC)

Say you have an impedance R+jX, in complex form, it's going to be with respect to the characteristic impedance of a system, Z0. To normalize this impedance, you divide by Z0 so you can plot the now normalized impedance, r+jx, within the unit smith chart.

...Any impedance, expressed in ohms, may be normalised by dividing it by the characteristic impedance,...—Preceding unsigned comment added by 24.128.254.144 (talkcontribs)

Better chart[edit]

The chart on this page is pretty crappy looking. Maybe we can change it to this one: http://www.sss-mag.com/pdf/smithchart.pdf samadam (talk) 17:18, 22 April 2010 (UTC)

Do you have a free licence to use it? The home page of that site says "all rights reserved". SpinningSpark 21:05, 22 April 2010 (UTC)
I don't, which is why I didn't change it. But it would be a good idea for someone to look into using it here. samadam (talk) 15:51, 30 April 2010 (UTC)
If you want to use it you need to approach the copyright holder for a suitable licence. On Wikipedia, you are usually disappointed if you hope someone else will do it for you. SpinningSpark 17:26, 30 April 2010 (UTC)

3D Smith chart[edit]

Ok, someone has written a letter to the IEEE proposing this. But that's a long way from notable if it's been completely ignored by everyone else. Sounds rather impractical to me. SpinningSpark 20:09, 14 May 2011 (UTC)

It looks like there has been some development in this area, there is an application (demo) for this here: http://3dsmithchart.com/content/3d-smith-chart-demo It still seems in an early stage but the principle is demonstrated and it works. I think the demo and site should at least be added as a reference to the 3D Smith Chart section. Also an article in the IEEE is not easily accepted and should have some weight, after all it is the same IEEE MTT that in 1975 presented Philip Smith the inventor of the Smith chart with a Special Recognition Microwave Application Award for his invention and application of the Smith Chart. DizzyC (talk) 12:13, 7 December 2011 (UTC)

Letters to the editor are not peer reviewed in the same way as articles are. Nevertheless, I wouldn't object to a link to the site home page, but, per WP:EL, we should not directly link to the demo which requires java. SpinningSpark 10:57, 10 December 2011 (UTC)

Terminology[edit]

What is a "generic rectangular complex number"? Nijdam (talk) 18:01, 26 July 2012 (UTC)

I suppose it means the complex numbers are expressed in rectangular co-ordinates, as opposed to the polar coordinate form. The generic bit refers to representation by generalised variables as opposed to a specific frequency function. The phrase is probably a little redudant. SpinningSpark 17:24, 31 July 2012 (UTC)

Sign problem with formula for variation of reflection coefficient with line length to load[edit]

The problem is that the term exp(2jBl) given for the change in reflection coefficient at the presumably positive distance l from the load is wrong. It should be exp(-2jBl). See any standard reference for this, such as equation 2.42 in the 3rd edition of Pozar's Microwave Engineering. The need for the argument of the exponential to be negative can be seen from the clockwise rotation of the reflection coefficient (blue line) in the accompanying figure of this article.

The origin of the problem is that the formula Vf=A*exp(-gamma*l) assumes that l is distance measured in the direction of forward propagation away from the generator. The reflection coefficient adjustment term exp(2jBl) is therefore only correct if l is understood to be a negative quantity measured going back to the generator, away from the load. However, by convention, the parameter l in the reflection coefficient adjustment term is the positive length of line between the load and measurement point. This is reinforced by the accompanying figure description in which l is said to be the line length. The term therefore must be exp(-2jBl) to give clockwise rotation. The formula given later in the article for impedance transformation, involving tan(Bl), also only works if l is the positive line length away from the load. Does anyone have any ideas for cleaning the inconsistent meaning of l in the article? Should perhaps l be defined as the distance toward the generator, rather than away from the generator, in the entirety of the article? Brian Wowk (talk) 07:16, 1 March 2013 (UTC)

I made the figure in question and could change it if necessary ... but changing the text instead would much easier :-P (I didn't write the text by the way.)
Maybe
should be rewritten
where x is the coordinate on the line.
Then we can have text like
If the load at x=l has reflection coefficient C --- i.e. --- then the generator at x=0 sees the reflection coefficient
Do you agree? Or something like that?— Preceding unsigned comment added by Sbyrnes321 (talkcontribs)
That could work, except that the terms are also used to derive the impedance transformation equation in tan(Bl). Expressing phase variation as a function of distance x toward the load (making x necessary negative if the load is the reference point), and then explaining a conversion to positive distance l=-x back from the load to derive the usual textbook equations gets a bit awkward. I went ahead and implemented what appears to be the cleanest solution. I redefined l as the distance from the load toward the measurement point, and reversed the sign of all expressions involving l except the tan(Bl) impedance transformation which was correct as written. See what you think. Brian Wowk (talk) 20:19, 1 March 2013 (UTC)