Talk:Waveguide (radio frequency)

Untitled

SLAC defn: A waveguide is an evacuated rectangular copper pipe. It carries electromagnetic waves from one place to another without significant loss in intensity--Light current 01:54, 31 January 2006 (UTC)

Merge Waveguide (optics) into this article?

I have suggested merging this article with optical waveguides, as optical waves are higher frequency electromagnetic waves. I think the problem could be solved if optical waveguides was made a subsection of this article. --Fred138 01:44, 11 October 2006 (UTC)

Hi. I was planning to expand the Waveguide (electomagnetism) page considerably. I've only got as far as rewriting the introduction and adding a picture, but I was intending (eventually):

• Simple analysis of rectangular guide in terms of superposed plane-waves / multiple reflections.

• Standard analysis of rectangular guide by solving Maxwell's equations by separation of variables.

• Ditto for circular guide.

• Mention of double-ridge guide etc.

• Definition of dominant mode. Uses of over-moded guide.

• Discussion of relative merits/uses of 2:1 rectangular guide, circular/square guide and two-conductor lines (coax/microstrip).

• Table of standard rectangular guide WG/WR.

• Mention of waveguide components (selection from: bends, transitions/tapers, junctions, magic-T, power-dividers, polarizers, filters, branch-couplers etc.) - with some more pictures!

• Mention of E-plane split construction of rectangular guide components.

This might make a merged page a bit long and a bit one-sided (weighted towards hollow metal guides). Of course there's no real physical distinction between microwave and optical guides, but the technology is a bit different so it's a convenient split. So I have a slight preference for separate pages. --catslash 13:34, 11 October 2006 (UTC)

Although, there is also a page on Fiber Optics and its applications here on wikipedia. Perhaps one could reference that and do away with the optical waveguide article? Then again, if you plan to make this one that in depth, then I guess it would be alright to keep them separate. They just both seem too short at present, which is why I suggested it. Perhaps making the optics one more in depth as well could help.--Fred138 14:28, 11 October 2006 (UTC)

Personally, I have no plans to make the Waveguide (optical) page more in-depth. Also, there is a speaking tube page to cover the acoustic case. So I'm persuaded that merging is a good plan. If, in the distant future, this article becomes too long, then we can think again, and (say) split dielectric guides from hollow metal guides. --catslash 14:48, 11 October 2006 (UTC)

I don't think merging them is a good idea. Hollow metal microwave guides are sufficiently different from dielectric optical waveguides to merit two articles. Whether one makes the break by wavelength or by hollow metal vs. dielectric is a matter for discussion. Note, though, that not all optical waveguides are fibers. Non-fiber optical waveguides are extremely important technologically. They are widely used in photonics and semiconductor lasers.--Srleffler 08:52, 11 November 2006 (UTC)

I think it would be a great idea to merge the Waveguide (optics) with Waveguide (electromagnetism). These topics are identical and similar treatment of these waveguides can be found in both optics and E&M texts. Waveguide (electromagnetism) should also be added to the optics category.Gfutia 22:19, 17 October 2007 (UTC)

I think that there should be one big merger into one article called waveguides. Then you start with the general waveguide going into TE, TM, and TEM waveguides, Rectangular waveguides, Coaxial transmission Line, Optical, etc... Just follow the two standard books in Electrodynamics (Giffiths and Jackson). This is the way they treat waveguides.

I agree that Waveguide (optics) should be merged into Waveguide (electromagnetism). I don't think the waveguide articles should by divided by wavelength. Perhaps one umbrella article Waveguide (electromagnetism) that contains the theory and math derivations, with hatnotes directing readers to functional articles Dielectric waveguide, Metal waveguide, Optical fiber, etc. describing the specialized types. --Chetvorno^TALK 05:20, 30 October 2010 (UTC)

Vagueness of lead section

The sentence "A wave guide is used to guide waves" assures a non Scientist/Engineer will have no idea what the rest of the article is about. Suggested change: A Waveguide is used to transport an electrical signal, prevent an electrical signal from leaking via radiation. Filter unwanted components of an electrical signal.

It does clearly state electromagnetic waves, but it's true that guide is a bit vague. Filtering is not relevant. --catslash (talk) 22:48, 1 June 2009 (UTC)

Pressurized guide

This is a surprising statement:

"In some waveguides, there may be a positive gas pressure internally present, allowing for the detection of potentially dangerous RF leaks. Another solution to detect RF leakage of a waveguide is to have a partial vacuum present inside. Then leaks can be detected in basically the same way."

I think there may be some confusion here. Waveguides are sometimes pressurized to inhibit arcing/multipaction, and are sometimes evacuated because they are part of evacuated systems (e.g. electron beam systems), but I've never heard of pressurization to detect breaches. Are there any references to support this claim? --catslash 23:20, 8 September 2006 (UTC)

The "pressurize to determine dangerous leaks" is the wrong answer on the beginners radar test. - Bogus, going to change it.71.110.64.173 23:11, 1 July 2007 (UTC)

You could have a horn feed for a cassegrain antenna for example that would require a weather-tight dielectric window across the aperture. You would need to make the whole waveguide system gas tight with rubber gaskets and then put in a slightly positive gas pressure of some suitably dry high breakdown gas and monitor the flow rate. If you get a small leak you can detect the increased flow rate and hopefully it will keep the rain and dust out until you can repair it. ChrisAngove 20:00, 24 November 2006 (UTC)

Bad pressurized WG info replaced. Fubartu 00:25, 2 July 2007 (UTC)

Many pressurized waveguides are pressurized for an entirely-different reason. The (dry, inert) presurized gas on the inside helps prevent water (or water vapor) from leaking inside. Keeping the water out helps prevent corrosion, and preventing corrosion maintains the high conductivity of the metal lining of the waveguide.

Even copper and silver corrode, especially in the presence of chlorine, sulfur, and/or nitrogen oxides. Sulfur and nitrogen oxides, and traces of hydrochloric acid, are found in rainwater. Lots of waveguides are outdoors, too.98.81.3.202 (talk) 02:40, 17 April 2012 (UTC)

Waveguide resistive terminations

We bady need some stuff on the dummy loads used with WG. Any offers? --Light current 23:01, 25 January 2007 (UTC)

There is some here on page 576. Otherwise, the article has much on high power waveguide use, including waveguide valves. Gah4 (talk) 19:50, 24 April 2020 (UTC)

Distinguishing between Optical, RF, EM and "Dielectric" vs "Pipe" WGs

Hi all. I'm just here disambiguating "Beam" and this isn't my field but the WG article TITLEs are a little muddled. Might I suggest that:

• "Waveguide (optics)" be retitled "Waveguide (dielectric)" or similar
• "Waveguide (electromagnetism)" be retitled "Waveguide (hollow metal pipe :-)" or similar.

Reasons:

• It's all EM
• EM in fibers is often not visible
• Optical is also a general term refering to any EM bouncing around, e.g. GO, PO and BWGs (which don't even have a reference in WP!?)

I've drop this in Waveguide, WG(em) and WG(opt) as there doesn't seem to be much overlap between the "talkers". Enjoy, Saintrain 18:03, 12 February 2007 (UTC)

Hollow-metal-pipe versus dielectric, seems a reasonable split to me - see last two paragraphs of #Merger (above).--catslash 21:13, 12 February 2007 (UTC)

Um, why would we want waveguide hollow metal pipe? If anything, there should be 1 article about waveguides that includes the math required to analyze them. If a discussion of different geometries is needed than it should be placed in a section of that article. Gfutia 19:14, 19 October 2007 (UTC)

Merging

I would recommend not merging the two pages together. Instead you may want to retitle waveguide (electromagnetism) to waveguide (RF) or waveguide (microwave). Optical waveguides are almost exclusively fiber optic based where RF/microwave/millimeter wave waveguides are almost always hollow metallic tubing. Two very different concepts. —The preceding unsigned comment was added by 199.46.200.233 (talk) 23:07, 15 March 2007 (UTC).

Dubious

Concerning this sentence: Waveguides are highpass filters.

I believe they are not high-pass (neither low-pass). Googling did not confirm article sentence. Kar.ma 17:54, 28 January 2009 (UTC)

It is obvious that electromagnetic waveguides (whether ractangular, circular, or elliptical) ARE highpase filters. Waveguides have a clearly-defined lower cutoff frequency, below which they pass practically nothing, and no upper cutoff frequency at all. See many different textbooks on electromagnetic fields, such as the one by Kraus and Carver. D.A.W. - BEE & MSEE.

Also, the terminology is standard: {waveguide, lowpass, bandpass, and highpass}. If you had the misfortune not to be educated in the United States or Canada, that's too bad. There are more English-speaking (as their primary language) electrical engineers in North America than in the rest of the world put together, and more books & journal articles pubilshed, so North American terminolgy must dominate. In other instances, the German word for radio is "Radio", computer is "Computer", and "transister" is "Transister".

Just so I know, wtf is a transistEr? — Preceding unsigned comment added by 62.34.228.5 (talk) 12:07, 8 October 2015 (UTC)

98.81.3.202 (talk) 02:23, 17 April 2012 (UTC)

More dubious and too many Waveguide entries

"Transmission lines such as microstrip, coplanar waveguide, stripline or coaxial may also be considered to be waveguides". No. a waveguide is a kind of transmission line, not the other way around. Transmission line is a general term that is applicable to ALL structures aimed at transporting EM energy (including optic) from one point to another. This includes twisted pairs, waveguides and optical fiber. By the way a sound pipe is NOT a waveguide.

A waveguide can act as a high pass filter or attenuator, but they are NOT filters.

Why is there another waveguide entry? Filled with much bogus and wrong info. Why can not people who have little to contribute, or not qualified to contribute keep their hands off these articles? Just asking... —Preceding unsigned comment added by 173.77.162.40 (talk) 20:02, 26 February 2011 (UTC)

Some authors (see e.g. IEEE dictionary) define a transmission line as a waveguide having a least two conductors or (nearly equivalently) as a waveguide supporting a TEM (or quasi-TEM) mode (which is my own view on the matter), while others also consider a hollow-pipe waveguide to be a type of transmission line. However I've not come across anyone arguing a that a (two wire) transmission line or a dielectric waveguide isn't a waveguide. Be that as it may, this page is about the common meaning of waveguide, i.e. one in the form of a hollow metal pipe.

I agree that the title waveguide belongs to a page describing the EM hollow-metal-pipe type, because that is the primary meaning, and anything else should get a longer title e.g. waveguide (acoustic), waveguide (dielectric) etc.. Unfortunately editors from other fields do not seem to agree.

The sentence about high-pass filters seems to have been removed a while back - I can't find it anyway.

Though there may be some other RF pages which suffer from overenthusiastic underinformed contributions; the problem on this page is lack of expert input. Perhaps you could help to remedy this? --catslash (talk) 00:34, 27 February 2011 (UTC)

Thanks for the feedback. Key point is, "waveguide" means something very specific to folks who are in the field and work with it. No two RF/MW engineers are likely to argue about what that means. Presumably anyone looking this word up in here is interested in learning what "waveguide" means to people who use it in their daily life and work. This is not exactly a sementic dilemma or a matter of opinion usually. There should not have been multiple entries for this one single word and concept and all applications could have been covered under one single heading with proper sections. As much as I appreciate the Wikipedia process and how it tries to satisfy the general public's "opinion" on various matters, sometimes the facts get lost in the shuffle. I will come back here again. Much more can be added related to waveguide components for example. Cheers.

Good to see that you've already felt moved to contribute to this article. If you intend to make further contributions then it's well worth registering a user-name; you don't have to supply any personal information, and you get extra powers.

If you work with waveguide perhaps you could contribute some photos? I've uploaded some waveguide pictures to the Wikimedia Commons, but since my work is entirely theoretical, my own collection of waveguide bits is very small. It would be nice to have a picture of double-ridge guide, a pressurizing section (with a Schrader valve I mean) and an actual photo of a magic T. There's plenty of pictures of these things on the web of course, but we need free-license images for Wikipedia. Cheers, --catslash (talk) 16:50, 27 February 2011 (UTC)

It isn't until the mathematical analysis section that we find that non-hollow (more than one conductor) systems, such as coaxial cables, are also waveguides. Just as circles are also ellipses, and square also rectangles, coaxial cables are also waveguides. (And, as noted, pipes are acoustic waveguides, though don't belong in this article.) As with ellipses and rectangles, the less specific name is commonly used when the more specific form is not meant. It would be worth noted at the beginning of the article, that even though coaxial cables are waveguides, specifically ones that can propagate in TEM00 mode, they are (mostly) not described in this article. Also, even dielectric waveguides are probably better described in the optical fiber article. Gah4 (talk) 20:04, 24 April 2020 (UTC)

Recent additions, Helmholtz Equation

I moved this to the talk page because it could be part of the article, but it was in the wrong place and there is not a place in the article where it could be dropped in. It gives the solution for a particular wave guide, the hollow rectangular wave guide. The article was discussing wave guides in general where it was. If this was added to the article, it would need some supporting information such as variable definitions, probably a figure and needs to discuss that it pertains only to the one type of wave guide. There is no place in the article that this could be dropped in without more work.

With a Helmholtz below:

$\nabla ^{2}E+k^{2}E=0$

using the boundary conditions of z (unlimited space) which can deduce a solve:

$u(x,y,z)=(C_{1}\cos k_{x}x+D_{1}\sin k_{x}x)(C_{2}\cos k_{y}y+D_{2}\sin k_{y}y)e^{ik_{z}z}$

and using the boundary conditions of x and y, inserting the standing wave equation:

${\begin{cases}E_{x}=A_{1}\cos k_{x}x\sin k_{y}ye^{ik_{z}z}\\E_{y}=A_{2}\sin k_{x}x\cos k_{y}ye^{ik_{z}z}\\E_{z}=A_{3}\sin k_{x}x\sin k_{y}ye^{ik_{z}z}\end{cases}}\qquad {\begin{cases}k_{x}={\frac {m\pi }{L_{1}}}\\k_{y}={\frac {n\pi }{L_{2}}}\end{cases}}$

As we can know ${\textstyle \nabla \cdot E=0}$ should be an another constraint equation. So for each ${\textstyle (m,n)}$ has two modes in it which are called TE and TM modes introduced below.

Constant314 (talk) 01:55, 15 January 2016 (UTC)

TEM modes in the hollow waveguide

I believe recent posts about the existence TEM modes in hollow wave-guides are using the terminology incorrectly or confusedly. It is true that a propagating TE mode can be decomposed into the superposition of two plane waves, each of which is TEM to its own direction of propagation. However, neither plane wave is a mode of the wave-guide because neither will satisfy the boundary conditions or the wave-guide. Further, there is a statement that non-propagating TEM modes form the propagating TE modes. If the TEM modes were not propagating, then it would not extend far enough into the wave-guide to form TE modes deep in the wave-guide.Constant314 (talk) 13:08, 6 May 2016 (UTC)

Pragnan Chakravorty 19:22, 6 May 2016 (UTC)
It is important to note that the edits didn’t refute the common notion of TEM being non-propagating in a waveguide. It only supported this notion in a different way. We should appreciate the fact that electromagnetic waves are intrinsically TEM in nature, had it been not so, we would have had TE or TM modes even in free space. In other words, if TEM mode doesn’t exist in a waveguide then how does it reappear when the waves come out of the guide?
If we ask ourselves that can the waves exist without propagating, then the answer is obviously yes, the examples are standing waves or evanescent waves which do exist without propagating. Inside a waveguide, if the z direction is open for wave propagation, then TEM waves along x and y axis form standing waves. These standing waves would impress either their electric fields or magnetic fields along z direction (direction of propagation) to form TM or TE modes respectively. This is how non propagating TEM waves can give rise to propagating TE or TM waves inside a waveguide. A detailed analysis of this phenomenon is given in the cited article.
Please write to me at pciitkgp@ieee.org, if you don’t have access to this article. The article has been published by a renowned publisher after it has undergone a rigorous peer review.
I understand that you may not like to get your text edited by anyone else; in that case, I would request you to read this article and include its basic idea in your text so as to provide a more holistic discourse on waveguides.Pragnan Chakravorty 19:22, 6 May 2016 (UTC)

I have written to you as requested and look forward to reading the article. The particular words that were edited were not my words and I do not have any special attachment to them. What has been written, appears, at least by my interpretation, to refute common knowledge about waveguides, hence my request for discussion. Constant314 (talk) 20:41, 6 May 2016 (UTC)

I have emailed you the article.Please also consider the following comments to better understand my point of view:
Why TEM must exist: Electromagnetic waves by their very nature are TEM. No electromagnetic wave generator can create a propagation mode other than TEM (i.e. they can’t create a stable TE or TM mode which can exist in free space or any arbitrary bound or unbound medium). It is important to note that even in the Maxwell’s equation the electric field, the magnetic field and the direction of wave motion must all be orthogonal to each other due to the curl operators, i.e. if the electric fields or magnetic fields are directed along the wave motion then Maxwell’s equation can’t be held true. In a waveguide, the very existence of TE and TM modes are attributed to the electric or magnetic fields contributed along the direction of propagation (along the open ends of a waveguide) by the standing TEM waves; if there were no TEM, even TE and TM would not exist.
Why TE and TM are only temporary impressed modes: To understand this in a simple way, we can assume that when TEM waves are launched inside a waveguide, they tend to move along all three orthogonal directions (i.e. x, y and z of Cartesian coordinate system); if z is along the open ends of the waveguide then standing waves are formed along x and y direction. But these standing waves being TEM direct their electric or magnetic fields along z; these electric and magnetic fields along z direction get impressed upon the TEM wave moving along z direction. Thus TE and TM modes are temporarily impressed due to the boundary conditions. The moment these boundaries are gone, these impressed modes are also gone; therefore, TEM waves along all three orthogonal directions remain juxtaposed with each other, within a waveguide, in a way that TE and TM modes are impressed. It is important to appreciate the fact that TE and TM are only temporary modes and they can’t exist without a waveguide.Pragnan Chakravorty182.66.12.162 (talk) 05:51, 7 May 2016 (UTC)

Accuracy of mm Dimensions in Table in "Waveguide in Practice"

We should sacrifice the little space needed to present the mm values more accurately. I've just checked WR51 which is supposed to be 12.954 mm wide but is indicated as 13.0 mm. — Preceding unsigned comment added by 153.92.184.111 (talk) 13:42, 28 November 2017 (UTC)

Change of disambiguation

@Fgnievinski: You recently changed the title disambiguation from Waveguide (electromagnetism) to Waveguide (radio frequency). I agree that "electromagnetism" is not a terribly good title, but "radio frequency" is problematic as well. Waveguides are generally used in the microwave bands (the higher microwave bands at that) and radio frequency is often used in contrast to microwave in the literature. I suggest Waveguide (microwaves) is more appropriate. The only fly in the ointment with that is that the article currently seems confused over whether it wants to include optical waveguide (which makes radio frequency even more inappropriate). The hatnote suggests that it is not included, but nevertheless, both the lead and the body discuss it. SpinningSpark 11:49, 6 November 2019 (UTC)

In my book, microwaves are high-frequency radio waves. Yet we have distinct articles on radio-frequency engineering and microwave engineering. So I don't oppose your proposed renaming. To help, I've edited the present article to de-emphasize optical applications while also reviving the section heading Waveguide#Electromagnetic waveguides. fgnievinski (talk) 14:52, 6 November 2019 (UTC)

Radios are going to higher and higher frequencies, but I do believe that microwaves are already a subset of radio frequencies. By the way, radio frequency goes down to at least 60kHz (the WWVB transmitter), and used to go down to 20kHz (another WWV transmitter). WiFi is now in the 5GHz range, which would have been microwave not so long ago. Gah4 (talk) 19:57, 24 April 2020 (UTC)

TEM curlE=0

@Constant314: I think the answer is as follows (but I wouldn't stake my life on it). In a TEM wave the components of curl d/dx Ez and d/dy Ez cannot exist because they a require a z component of E, and d/dx Ey and d/dy Ex cannot exist because they produce a z component of B. That just leaves d/dz Ex and d/dz Ey which result in the E field varying along the length of the guide. I don't think that can happen in a lossless guide with dimensions invariant with z. Why don't you get the cited source from the Library if you think the statement is dubious. SpinningSpark 20:55, 13 March 2020 (UTC)

I submitted the request. Due to technical problems I will have limited connectivity for the next 7 to 10 days. Please don't take my silence as anything other than communication difficulty. Constant314 (talk) 00:47, 14 March 2020 (UTC)

Rectangular waveguide maths

Hello,

I was considering adding various results about rectangular waveguides as well as the mathematical developments necessary to obtain them (a priori starting from Maxwell's equations)

1. helmotz equation (maybe using it as a starting point could be a good idea)
2. boundary conditions
3. expression of the fields in TE and TM modes
4. cut-off frequencies (lossless and lossy medium)
5. induced currents
6. losses

The whole thing would be illustrated by pictures I made.

Some of these concepts are already covered somewhere on wikipedia in a very general context. I propose to explore them specifically for rectangular waveguides. Is this interesting? Is it more appropriate to create a new page dedicated to rectangular waveguides and their analysis? Is it convenient to write the entire math development or only the main results? Or a brief and simplified reasoning with links to books and other sources?

Thanks for your advices

VK Vivien (talk) 09:42, 24 April 2020 (UTC)

I reverted your initial attempt because I didn't think it was appropriate for this article. Remember, we are writing encyclopaedia articles and should always bear in mind the understandability of an article to a general reader. We shouldn't write in the style of a textbook, or attempt to teach a subject. This is explicitly proscribed by Wikipedia policy. Long tracts of mathematics are very off-putting to the typical reader, and at the same time, many untrained readers may be interested in finding out what waveguides are all about.

I think a more appropriate place for this would be a page specifically on modes. Readers who go to such a page may be more likely to expect a mathematical treatment. Transverse mode already has a section for waveguide modes. You could expand that section, but you seem to want to write so much that a separate page might be in order. Provide a summary only here with a link for those readers interested. SpinningSpark 12:00, 24 April 2020 (UTC)

I agree that the proposed addition is too complex for this article. Constant314 (talk) 14:29, 24 April 2020 (UTC)

Hollow waveguide

It seems to me that the main subject of this article is the hollow waveguide, commonly shortened to just waveguide. I will make a redirect for it, but I suspect that hollow waveguide might be a better name for the article. Gah4 (talk) 20:35, 24 April 2020 (UTC)

Yes, this is a common problem we keep coming up against on page after page. When we started calling these things waveguides, microstrip, light pipes, finline etc just didn't exist. Pages that were originally on a narrow subject get expanded and overcomplicated over time. SpinningSpark 00:04, 25 April 2020 (UTC)