This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
"Guided Wave" Absolutely should not redirect here! A guided wave is not a waveguide - especially since whatever you think otherwise about a waveguide, it is technological creation made by human beings. In other words, it is artificial.
There are lots of cases of guided electromagnetic waves that use surfaces that were not created by people. Here are some of them:
We can set up a radio transmitter that transmits at a suitable frequency on one side of Lake Superior, Lake Huron, Lake Erie, or Lake Ontario (hereafter called the "Lake") and transmit radio waves over to the other side of the Lake (U.S.A. to Canada or vice-versa). If the frequency is not too high that wave will become attached to the surface of the water at its bottom end, since the water is somewhat conductive. Specifically, its electric field will be perpendicular to the surfact of the water and (for all practical purposes), its magnetic field will be perpendicular to both its magnetic field and to the direction of propagation. In this way, the radio wave will propagate across the Lake quite efficiently, with most of its power density concentrated rather close to the surface of the water, and not dispersing upwards toward the stratosphere and outer space.
During the 1930s and 40s, there was actually some transatlantic telephone service that did not, repeat, did not, use undersea cables. Such cables were impractical at the time because the electronics technology was not good enough. (The first undersea transaltantic telephone cable did not come into seriece until 1956.)
These systems used radio back and forth actross the Atantic. Electronics technology had not progressed enough to generate the high RF power levels necessary. What they did was manufacture high frequency alternators. The alternators had fast-spinning armatures and multiple magnetic poles to generate carrier frequencies in the range 10,000 to 100,000 hertz. (10 to 100 KHz). Amplitude modulation was impressed on the carrier wave, transmitted with a vertical antenna to get the electric field vertical. Antenna arrays were used to aim the transmitted EM waves toward the British Isles, or if on that side of the Atlantic, toward the U.S.A. and Canada. The distance was much farther, but signal propagation was aided by the fact ocean water is salty and a better conductor of electricity. Transmittter power levels could be as high as 200KW. The EM waves propagated as guided waves, with the lower end of their electric fields attached to the water. The EM waves followed the surface of the water right along the curvature of the earth, and in this way, they reached Europe, rather than propagating up to the ionosphere, to outer space, or whatever the undesirable direction was. So, these guided waves not only followed the curvature of th earth, but they also kept most of their power density at a fairly-low altitude where an antenna on the other side of the ocean could collect enough of the power.
It is not necessary to use water for the substance that guides the wave. In some other systems, soil is used - but moist soil is better, of course. This is where you find systems that use what is called the "ground wave". Those just get guided along the earth's surface, as "ground waves" rather than up into the sky . Ground waves are very important to AM radio broadcasting. How good they are depends a lot on how damp the spoil is and how flat the land is. I can remeber on a long auto trip that I took, and I passed through Kansas City on my way via Lincoln, Nebraska (to get on I-80), and then out to Cheyenne, Wyoming. It was broad daylight, and while I was in the K.C. area, I picked up the radio station KCMO. Well, I listened to KCMO all the way to the southwestern corner of Iowa, and then cut west across Iowa to get to Nebraska, and then I still listened to KCMO all the way out to Lincoln, loud and clear. There was no way that I could have done this without ground waves. I was way out of the line-of-sight from K.C., and in the AM band, sky waves are no good in the daytime. So, no line-of-sight waves, no sky waves, the only thing left was ground waves. I ate dinner in Lincoln, and then drove farther west, and I think that I was still listening to KCMO.
98.81.18.144 (
talk)
TLs and WG work on different principles. For example: there's signal loss in TLs but no loss in waveguides. So how can they be the same thing?-- Light current 00:04, 22 January 2006 (UTC)
TLs operate on TEM mode. WG are TE or TM modes. TEM plane waves cannot propagagate in WG.-- Light current 05:55, 23 January 2006 (UTC)
I classify them as TLs. Predominantly TEM propagation. See here [1]-- Light current 03:35, 24 January 2006 (UTC)
I dont agree. All the books I have differentiate between the two structures.-- Light current 05:02, 24 January 2006 (UTC)
FE Terman 4 th ed treats WG and TLs in separate chapters. Also, Electromagnetism by Grant& Philips (Physics Dept Manchester Uni) pub John Wiley, treats them differently.-- Light current 18:45, 25 January 2006 (UTC)
A transmission line can act as a waveguide if excited above its WG cutoff frequency when different propagation modes are used. But TLs are overwhelmingly used in the TEM mode. I think you need to look at that book you quoted in detail (rather than just the abstract or snippet) to see what the author is really saying.-- Light current 05:08, 24 January 2006 (UTC)
Well looking at it from that point of view, I suppose you could say that any conveyor of information is a 'transmision line'. If you want to go down that path, then I would say that a waveguide is part of the larger group called 'transmission lines'.
However, you have to be careful here, because one of the primary differences (apart from the modal one) is that WGs are narrowband structures (they have cutoff and go into different, unsatisfactory, propagation modes at higher frequencies) whereas TLs (coax etc) are generally thought of as wideband 'pipes' and in fact go right down to dc from say 20 GHz. WGs dont do dc or anywhere near. So, on an octave BW basis TLs are wider band than WG and I think this is one of the main differences. The other main difference is that WGs can do much higher frequencies with low attenuation than TLs can. Does this help at all?-- Light current 05:15, 25 January 2006 (UTC)
No citation because WG do have losses (my exaggeration- sorry). But much lower losses than TLs because the energy is bouncing off the walls. Highly conducting polished walls will give lower losses.-- Light current 06:03, 23 January 2006 (UTC)
I will admit to being biased/ignorant about the terminology because I, like some others, have not covered the whole gamut of WG and TLs. In fact I have never bolted pieces of hollow WG simply becuase I have never been working at those frequencies. Neither have I jointed two pieces of optical cable. However, I do agree that the subject appears to be large enough that a split based on Stephens/Photons suggestions seems sensible. I will then restrict myself to editing the electromagnetic WG and TL pages.-- Light current 17:49, 26 January 2006 (UTC)
My personal opinion concurs with the following extract that Stephen Johnson has found:
The term waveguide can be applied to all types of transmission lines in the sense that they are all used to guide energy from one point to another. However, usage has generally limited the term to mean a hollow metal tube or a dielectric transmission line. In this chapter, we use the term waveguide only to mean "hollow metal tube."
-- Light current 23:36, 26 January 2006 (UTC)
Before everyone gets too agitated about differences and similarities between WG and TLs, Im going to suggest that it seems to me there is is difference in view here between people on each side of the Atlantic due to the books they have been reading/studying.
It would seem that the USA view is that a TL is anything that can convey info: from a piece of wet string to an optical fibre and beyond. Over here (the old world), rightly or wrongly we have a more refined view of what constitutes a waveguide or a TL. So Im going to stick a globalise tag on the article just to remind people to be careful about representing a world view on this subject. -- Light current 18:52, 25 January 2006 (UTC)
Are you saying that all WG are TLs, or all TLs are WG or what?-- Light current 19:54, 25 January 2006 (UTC)
waveguide: A material medium that confines and guides a propagating electromagnetic wave. (188) Note 1: In the microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section. This type of waveguide may, under certain conditions, contain a solid or gaseous dielectric material. Note 2: In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section. In integrated optical circuits an optical waveguide may consist of a thin dielectric film. Note 3: In the rf regime, ionized layers of the stratosphere and refractive surfaces of the troposphere may also act as a waveguide.
-- Light current 23:28, 12 March 2006 (UTC)
I wrote this out as part of another discussion, then realized it wasn't very useful there, but I didn't want to throw it away since I think it is helps to clarify the nomenclature discussion.
There are apparently three ways that the the categories of "waveguides" and "transmission lines" are defined:
I find the third view is used in practice by my colleagues in the fiber optics and high-speed electronics business, but when things get nasty we are likely to say "okay, so in this situation we have to consider all of the waveguide effects in this transmission line". On the other hand, the important thing here is, what gives the clearest explanation to the reader of an encyclopedia?
-- The Photon 02:34, 13 March 2006 (UTC)
Well, its hardly written in encyclopedic style... Also, this would dominate the article if inserted now, and I will stick to my proposition that an encyclopedia is about ideas, not words, so I'd find it distracting to have it stuck in there now. But it is GFDL, so I can't forbid it. -- The Photon 03:40, 13 March 2006 (UTC)
If you or someone else would like to re-write, it's GFDL. In my opinion, including the explanations it's too long for the lead. -- The Photon 04:11, 13 March 2006 (UTC)
I came to understand transmission lines as being an idealization in circuit theory, therefore a circuit guiding waves "on paper", with the proper symbols for capacitors, coils etc. Waveguides in my opinion are the physical embodiment of such. I have no specific quote to support this, rather all references in the literature that I read conform to this view. Setreset ( talk) 08:37, 24 December 2009 (UTC)
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:
Reasons:
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)
It is a matter of terminology as evident from the long discussions of the past. My personal optinion is to use the word waveguide for any structure which confines light in 1 or 2 dimensinos not allowing it to diffract. Such confinement is always done by some "mirror". I suggest to right a general article about waveguides, distinguidhing the different geometries (slab, channel, fiber) and different mechanisms of guiding (mirrors) i.e total internal reflection, metalic, or Bragg reflection (photonic crystal waveguides). Eranus ( talk) 13:47, 2 June 2009 (UTC)
I wrote the Hebrew version of waveguide which now contains lots of material that isn't found anywhere else on wikipedia, someone might want to give it a look (the Hebrew would be difficult but there are formulae and images). I'm not doing it myself since I don't want to step on any toes, all content was removed from this article, and divided into 5 different ones, for some purpose to me unknown. Setreset ( talk) 08:37, 24 December 2009 (UTC)
The article needs an ostensive definition in the format, "x is a waveguide because it satisfies X requirements. y is not because it does not satisfy Y requirements. LokiClock ( talk) 01:10, 27 December 2009 (UTC)
I dug in the history of this article, and found that the article was split and practically deleted by User:Light current who was repeatedly blocked until permanent ban. This might be one of his early and undiscovered works. Setreset ( talk) 09:09, 7 January 2010 (UTC)
Hi, I marked some of the recent additions as dubious because they reflect a very limited perspective of waveguides.
In the "theoretical analysis" intro:
The "propagation modes and cutoff frequencies" section has multiple problems:
The "impedance-matching" section is misleading, because the ability to describe a waveguide mode by a single "impedance" number that completely characterizes the reflection at a junction between two waveguides is only true in effectively one-dimensional systems. Essentially, it requires that the waveguide mode pattern have only a single degree of freedom, e.g. be described (locally) everywhere by a plane wave at a fixed angle and hence a single ratio of the transverse E to H field magnitudes. For general waveguides, e.g. an inhomogeneous dielectric waveguide, this is not the case (except in certain limits, such as very low index contrast as applies to standard optical fibers). For more general waveguides, "impedance matching" is at best a heuristic description of what happens at a junction.
There is certainly a place for these kinds of approximations, stated carefully, but not in a general theoretical description of all possible waveguides.
— Steven G. Johnson ( talk) 21:18, 7 January 2010 (UTC)
Recent anonymous edits removed much information, and restricted the waveguide to its narrowest meaning. I tried in the past to improve the article by adding information, but failed. It seems that for some reason this article always will tend towards becoming a stub. I removed it from my watchlist and will not trouble you further. Setreset ( talk) 08:42, 3 August 2010 (UTC)
It's a shame that the article is still plagued by a lack of consensus regarding the terminology of "transmission line" vs. "waveguide". Some are bothered by the fact that the present waveguide article uses the term "waveguide" in the narrowest (but most common) sense, namely a hollow metal pipe waveguide. They wish it to be more clear that the term waveguide is more general. On the other hand, if one goes to the "transmission line" Wikipedia webpage, it is interesting to note that this page initially defines transmission lines in a more general sense, so that waveguides would be included as part of this set! However, the article on transmisson lines then proceeds to discuss the theory for transmission lines as they are commonly thought of in the narrowest sense -- a two-conductor system supporting a TEM mode (which can be modeled using the Telegrapher's equations). It would be good for these two articles to be coordinated with the definitions.
In my own personal experience, I have always used "transmission line" to mean a two-conductor system, such as a coaxial cable or a twin-lead line, or a microstrip line. I have usually used "waveguide" to mean a hollow metal pipe waveguide, but I also realize that the term 'waveguide" can be more general. For example, one can have a "dielectric rod waveguide". One can also have a " coplanar waveguide," which in essence is simply a transmission line (albeit not with an exactly TEM mode, but a quasi-TEM mode).
I think it is relatively uncommon to use the term "transmission line" to mean something other than a two-conductor system. Presumabley a "transmimssion line" is something that obeys "transmission line theory", and this theory is all based on the theory of a two-conductor system (i.e., the Telegrapher's equations).
I would propose that in the waveguide article continue to state, as it does now, that the term waveguide is general, but that usually in common usage it means a hollow metal pipe. The article could then state that further disacussion in the article will be confined to this special class of waveguides. A more detailed discussion of other classes of waveguides could then be found in the links to other webpages. I would also propose that the article state in the beginnning that transmission lines are a special type of waveguide that consist of two parallel conductors, which is capable of supporting the TEM mode (or quasi-TEM mode if inhomogeneously filled) and which obeys (either exactly or approximately) the Telegrapher's equations. The waveguide article would then give a link to the transmisson-line webpage.
I would propose that the transmisson line article state that the term 'transmission line" can sometmes be a general one, but that normally the term is restricted to mean a two-conductor waveguiding system that can support a TEM (or quasi TEM) mode, which obeys the Telegrapher's equations. It should then state clearly that all further analysis in the article will be restricted to this type of system. —Preceding unsigned comment added by Elee1l5 ( talk • contribs) 21:53, 7 October 2010 (UTC)
Thank you for pointing out this other webpage -- I didn't realize (until I read more carefully later on in the article) that there was this other webpage for electromagnetic waveguides (I agree, it probably should be called Waveguide (microwave)). In view of this, I agree with Steven, the present article should not be restricted at all to microwave waveguides (metal-pipe waveguides) but should overview all of them. However, the article should make this aspect very clear at the beginning, and give a link to the microwave waveguide webpage early on, to minimize confusion between the two webpages. If this is the intent, however, to keep the present webpage focused on more general waveguides, then some of the later material in it should probably be moved to the other webpage (on microwave waveguides) or modified in some way -- for example, the discussion on impedance matching. I believe that this is what Steven was saying early on. Depending on how general the present webpage is intended to be, the structures do not have to even be limited to those that are translationally invariant. Certainly many waveguiding structures are periodic structures. This aspect is not discussed at all. I would also still recommend the minor clarification edit to the transmmission line webpage. Elee1l5 ( talk) 00:21, 9 October 2010 (UTC)
Okay, that's fine. A periodic structure (discrete translational symmetry) will support guided waves in general, and the definition of a waveguide can be taken as a structure with such symmetry. Maybe we shouldn't say that such symmetry is required, though, in order to have a guided wave existing on a particular structure. There could be cases, for example, where the structure is not physically periodic, but electrically it behaves as a periodic one at some frequency due to the nature of the discontinuities, and thus it supports a guided wave at this frequency. Of course there are also trivial cases where the structure is not periodic but the fields are zero in the region where it is not periodic, so a guided wave exists. Elee1l5 ( talk) 19:35, 11 October 2010 (UTC)
Another interesting class of guided waves are "leaky waves," which radiate (leak power) as they propagate. They can exist on both uniform and periodic structures. In microwave terminology, a guided wave on an open structure (e.g. microstrip line) is "bound" if there is no radiation, while a leaky mode is fundamentally unbound. Normally when most people use the term "guided wave" I believe that they mean either a wave inside of a closed structure (e.g., rectangular waveguide) or a bound mode on an open structure (e.g., the HE11 mode on a cylindrical dielectric rod, or the quasi-TEM mode on a microstrip line). I'm not sure if we wish to broaden the discussion of guided waves to include leaky waves.
Back to the main issue -- editing the webpages. I am recommending minor edits to the Transmission Line and Waveguide (electromagnetism) pages, including changing the name to Waveguide (Microwave) as suggested by Catslash. For the Waveguide webpage, I suggest that you, Steven, might be the best candidate to make the changes, if you accept such a duty. Probably the highest priority, in my opinion, is to address the sections where the content is labeled as being in dispute. Do we need some kind of a consensus before proceeding? Elee1l5 ( talk) 22:11, 12 October 2010 (UTC)
In general I agree with Steven Johnson's suggestion,
But rather than breaking the article up by wave equation, which has little meaning to most people, does it make sense to refer to applications instead? Optical waveguides fall under EM but they deserve a separate subarticle because there's a wealth of applications and technologies. 206.47.231.164 ( talk) 18:36, 26 April 2011 (UTC)
This whole article is in very very poor shape, one of the worst I have come accross in Wikipedia. Quality is naturally in contrast to the length (not depth) of discussion here. It is such a fundemental component and intersting and important transmission line type. Why folks who have very little to contribute, marginally informed, take it upon themselves to edit articles I will never know. As someone who has actually designed and built transmission lines of all kinds, including waveguides, and who makes a living engineering such circuits, I would like to clean things up a little but I am afraid of wasting effort given the dedication of non-contributers to non-contribute here. What does impedance matching have anything to do with waveguides? How can an artcicle like this not include waveguide sizes and standards and frequency bands? Usually copper? Even a freshman EM book has a better explanation of propagation properties. How about countless waveguide components, from filters, to couplers, to magic tees, to loads, irises, transformers, etc.? I suppose all were busy dissecting "transmission lines"... —Preceding unsigned comment added by 173.77.162.40 ( talk) 05:06, 24 February 2011 (UTC)
a bit should be added about how the holes in the microwave oven cannot contain the frequency (a waveguide not tuned to the freq acts as a reflector), and removes most of the radiation whilst letting shorter wavelengths through like light. i do not know the term for this kind of blocking.
i wrote "most" because of the article written called "light sneaks through small holes", it can get through when its 7% of a wavelength wide. i also read that if the hole is less then 100% of a wavelength then you get attenuation. perhaps show a graph of how much gets trough depending on % of wavelength. — Preceding unsigned comment added by Charlieb000 ( talk • contribs) 02:24, 9 October 2011 (UTC)
This whole article is messed up. — Preceding unsigned comment added by 138.163.0.42 ( talk) 00:03, 1 July 2014 (UTC)
The section on mathematical waveguides references something called a "bound state", but without enough information for an inexperienced layman (me) to figure out what that means. The terminology does not appear in the 'main article' for the section, either. KE7KTO ( talk) 20:58, 15 May 2017 (UTC)
Waveguide rotary joint is a single paragraph which could benefit by moving here to give it context. -- Wtshymanski ( talk) 20:53, 6 August 2017 (UTC)
Yet another SD that has been reduced from something that makes sense to something entirely useless. Blind rule-following is so much more important than helping the reader. Spinning Spark 10:44, 8 June 2022 (UTC)
Editors should bear in mind that short descriptions are not intended to define the subject of the article. Rather, they provide a very brief indication of the field that is covered, a short descriptive annotation, and a disambiguation in searches.The SD for this article, for example, could be "Type of telecommunications equipment". – Jonesey95 ( talk) 16:15, 20 June 2022 (UTC)
What is elongate? The waveguide is longer than it is wide? They don't have to be, though that would be usual. Gah4 ( talk) 04:28, 22 June 2022 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
"Guided Wave" Absolutely should not redirect here! A guided wave is not a waveguide - especially since whatever you think otherwise about a waveguide, it is technological creation made by human beings. In other words, it is artificial.
There are lots of cases of guided electromagnetic waves that use surfaces that were not created by people. Here are some of them:
We can set up a radio transmitter that transmits at a suitable frequency on one side of Lake Superior, Lake Huron, Lake Erie, or Lake Ontario (hereafter called the "Lake") and transmit radio waves over to the other side of the Lake (U.S.A. to Canada or vice-versa). If the frequency is not too high that wave will become attached to the surface of the water at its bottom end, since the water is somewhat conductive. Specifically, its electric field will be perpendicular to the surfact of the water and (for all practical purposes), its magnetic field will be perpendicular to both its magnetic field and to the direction of propagation. In this way, the radio wave will propagate across the Lake quite efficiently, with most of its power density concentrated rather close to the surface of the water, and not dispersing upwards toward the stratosphere and outer space.
During the 1930s and 40s, there was actually some transatlantic telephone service that did not, repeat, did not, use undersea cables. Such cables were impractical at the time because the electronics technology was not good enough. (The first undersea transaltantic telephone cable did not come into seriece until 1956.)
These systems used radio back and forth actross the Atantic. Electronics technology had not progressed enough to generate the high RF power levels necessary. What they did was manufacture high frequency alternators. The alternators had fast-spinning armatures and multiple magnetic poles to generate carrier frequencies in the range 10,000 to 100,000 hertz. (10 to 100 KHz). Amplitude modulation was impressed on the carrier wave, transmitted with a vertical antenna to get the electric field vertical. Antenna arrays were used to aim the transmitted EM waves toward the British Isles, or if on that side of the Atlantic, toward the U.S.A. and Canada. The distance was much farther, but signal propagation was aided by the fact ocean water is salty and a better conductor of electricity. Transmittter power levels could be as high as 200KW. The EM waves propagated as guided waves, with the lower end of their electric fields attached to the water. The EM waves followed the surface of the water right along the curvature of the earth, and in this way, they reached Europe, rather than propagating up to the ionosphere, to outer space, or whatever the undesirable direction was. So, these guided waves not only followed the curvature of th earth, but they also kept most of their power density at a fairly-low altitude where an antenna on the other side of the ocean could collect enough of the power.
It is not necessary to use water for the substance that guides the wave. In some other systems, soil is used - but moist soil is better, of course. This is where you find systems that use what is called the "ground wave". Those just get guided along the earth's surface, as "ground waves" rather than up into the sky . Ground waves are very important to AM radio broadcasting. How good they are depends a lot on how damp the spoil is and how flat the land is. I can remeber on a long auto trip that I took, and I passed through Kansas City on my way via Lincoln, Nebraska (to get on I-80), and then out to Cheyenne, Wyoming. It was broad daylight, and while I was in the K.C. area, I picked up the radio station KCMO. Well, I listened to KCMO all the way to the southwestern corner of Iowa, and then cut west across Iowa to get to Nebraska, and then I still listened to KCMO all the way out to Lincoln, loud and clear. There was no way that I could have done this without ground waves. I was way out of the line-of-sight from K.C., and in the AM band, sky waves are no good in the daytime. So, no line-of-sight waves, no sky waves, the only thing left was ground waves. I ate dinner in Lincoln, and then drove farther west, and I think that I was still listening to KCMO.
98.81.18.144 (
talk)
TLs and WG work on different principles. For example: there's signal loss in TLs but no loss in waveguides. So how can they be the same thing?-- Light current 00:04, 22 January 2006 (UTC)
TLs operate on TEM mode. WG are TE or TM modes. TEM plane waves cannot propagagate in WG.-- Light current 05:55, 23 January 2006 (UTC)
I classify them as TLs. Predominantly TEM propagation. See here [1]-- Light current 03:35, 24 January 2006 (UTC)
I dont agree. All the books I have differentiate between the two structures.-- Light current 05:02, 24 January 2006 (UTC)
FE Terman 4 th ed treats WG and TLs in separate chapters. Also, Electromagnetism by Grant& Philips (Physics Dept Manchester Uni) pub John Wiley, treats them differently.-- Light current 18:45, 25 January 2006 (UTC)
A transmission line can act as a waveguide if excited above its WG cutoff frequency when different propagation modes are used. But TLs are overwhelmingly used in the TEM mode. I think you need to look at that book you quoted in detail (rather than just the abstract or snippet) to see what the author is really saying.-- Light current 05:08, 24 January 2006 (UTC)
Well looking at it from that point of view, I suppose you could say that any conveyor of information is a 'transmision line'. If you want to go down that path, then I would say that a waveguide is part of the larger group called 'transmission lines'.
However, you have to be careful here, because one of the primary differences (apart from the modal one) is that WGs are narrowband structures (they have cutoff and go into different, unsatisfactory, propagation modes at higher frequencies) whereas TLs (coax etc) are generally thought of as wideband 'pipes' and in fact go right down to dc from say 20 GHz. WGs dont do dc or anywhere near. So, on an octave BW basis TLs are wider band than WG and I think this is one of the main differences. The other main difference is that WGs can do much higher frequencies with low attenuation than TLs can. Does this help at all?-- Light current 05:15, 25 January 2006 (UTC)
No citation because WG do have losses (my exaggeration- sorry). But much lower losses than TLs because the energy is bouncing off the walls. Highly conducting polished walls will give lower losses.-- Light current 06:03, 23 January 2006 (UTC)
I will admit to being biased/ignorant about the terminology because I, like some others, have not covered the whole gamut of WG and TLs. In fact I have never bolted pieces of hollow WG simply becuase I have never been working at those frequencies. Neither have I jointed two pieces of optical cable. However, I do agree that the subject appears to be large enough that a split based on Stephens/Photons suggestions seems sensible. I will then restrict myself to editing the electromagnetic WG and TL pages.-- Light current 17:49, 26 January 2006 (UTC)
My personal opinion concurs with the following extract that Stephen Johnson has found:
The term waveguide can be applied to all types of transmission lines in the sense that they are all used to guide energy from one point to another. However, usage has generally limited the term to mean a hollow metal tube or a dielectric transmission line. In this chapter, we use the term waveguide only to mean "hollow metal tube."
-- Light current 23:36, 26 January 2006 (UTC)
Before everyone gets too agitated about differences and similarities between WG and TLs, Im going to suggest that it seems to me there is is difference in view here between people on each side of the Atlantic due to the books they have been reading/studying.
It would seem that the USA view is that a TL is anything that can convey info: from a piece of wet string to an optical fibre and beyond. Over here (the old world), rightly or wrongly we have a more refined view of what constitutes a waveguide or a TL. So Im going to stick a globalise tag on the article just to remind people to be careful about representing a world view on this subject. -- Light current 18:52, 25 January 2006 (UTC)
Are you saying that all WG are TLs, or all TLs are WG or what?-- Light current 19:54, 25 January 2006 (UTC)
waveguide: A material medium that confines and guides a propagating electromagnetic wave. (188) Note 1: In the microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section. This type of waveguide may, under certain conditions, contain a solid or gaseous dielectric material. Note 2: In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section. In integrated optical circuits an optical waveguide may consist of a thin dielectric film. Note 3: In the rf regime, ionized layers of the stratosphere and refractive surfaces of the troposphere may also act as a waveguide.
-- Light current 23:28, 12 March 2006 (UTC)
I wrote this out as part of another discussion, then realized it wasn't very useful there, but I didn't want to throw it away since I think it is helps to clarify the nomenclature discussion.
There are apparently three ways that the the categories of "waveguides" and "transmission lines" are defined:
I find the third view is used in practice by my colleagues in the fiber optics and high-speed electronics business, but when things get nasty we are likely to say "okay, so in this situation we have to consider all of the waveguide effects in this transmission line". On the other hand, the important thing here is, what gives the clearest explanation to the reader of an encyclopedia?
-- The Photon 02:34, 13 March 2006 (UTC)
Well, its hardly written in encyclopedic style... Also, this would dominate the article if inserted now, and I will stick to my proposition that an encyclopedia is about ideas, not words, so I'd find it distracting to have it stuck in there now. But it is GFDL, so I can't forbid it. -- The Photon 03:40, 13 March 2006 (UTC)
If you or someone else would like to re-write, it's GFDL. In my opinion, including the explanations it's too long for the lead. -- The Photon 04:11, 13 March 2006 (UTC)
I came to understand transmission lines as being an idealization in circuit theory, therefore a circuit guiding waves "on paper", with the proper symbols for capacitors, coils etc. Waveguides in my opinion are the physical embodiment of such. I have no specific quote to support this, rather all references in the literature that I read conform to this view. Setreset ( talk) 08:37, 24 December 2009 (UTC)
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:
Reasons:
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)
It is a matter of terminology as evident from the long discussions of the past. My personal optinion is to use the word waveguide for any structure which confines light in 1 or 2 dimensinos not allowing it to diffract. Such confinement is always done by some "mirror". I suggest to right a general article about waveguides, distinguidhing the different geometries (slab, channel, fiber) and different mechanisms of guiding (mirrors) i.e total internal reflection, metalic, or Bragg reflection (photonic crystal waveguides). Eranus ( talk) 13:47, 2 June 2009 (UTC)
I wrote the Hebrew version of waveguide which now contains lots of material that isn't found anywhere else on wikipedia, someone might want to give it a look (the Hebrew would be difficult but there are formulae and images). I'm not doing it myself since I don't want to step on any toes, all content was removed from this article, and divided into 5 different ones, for some purpose to me unknown. Setreset ( talk) 08:37, 24 December 2009 (UTC)
The article needs an ostensive definition in the format, "x is a waveguide because it satisfies X requirements. y is not because it does not satisfy Y requirements. LokiClock ( talk) 01:10, 27 December 2009 (UTC)
I dug in the history of this article, and found that the article was split and practically deleted by User:Light current who was repeatedly blocked until permanent ban. This might be one of his early and undiscovered works. Setreset ( talk) 09:09, 7 January 2010 (UTC)
Hi, I marked some of the recent additions as dubious because they reflect a very limited perspective of waveguides.
In the "theoretical analysis" intro:
The "propagation modes and cutoff frequencies" section has multiple problems:
The "impedance-matching" section is misleading, because the ability to describe a waveguide mode by a single "impedance" number that completely characterizes the reflection at a junction between two waveguides is only true in effectively one-dimensional systems. Essentially, it requires that the waveguide mode pattern have only a single degree of freedom, e.g. be described (locally) everywhere by a plane wave at a fixed angle and hence a single ratio of the transverse E to H field magnitudes. For general waveguides, e.g. an inhomogeneous dielectric waveguide, this is not the case (except in certain limits, such as very low index contrast as applies to standard optical fibers). For more general waveguides, "impedance matching" is at best a heuristic description of what happens at a junction.
There is certainly a place for these kinds of approximations, stated carefully, but not in a general theoretical description of all possible waveguides.
— Steven G. Johnson ( talk) 21:18, 7 January 2010 (UTC)
Recent anonymous edits removed much information, and restricted the waveguide to its narrowest meaning. I tried in the past to improve the article by adding information, but failed. It seems that for some reason this article always will tend towards becoming a stub. I removed it from my watchlist and will not trouble you further. Setreset ( talk) 08:42, 3 August 2010 (UTC)
It's a shame that the article is still plagued by a lack of consensus regarding the terminology of "transmission line" vs. "waveguide". Some are bothered by the fact that the present waveguide article uses the term "waveguide" in the narrowest (but most common) sense, namely a hollow metal pipe waveguide. They wish it to be more clear that the term waveguide is more general. On the other hand, if one goes to the "transmission line" Wikipedia webpage, it is interesting to note that this page initially defines transmission lines in a more general sense, so that waveguides would be included as part of this set! However, the article on transmisson lines then proceeds to discuss the theory for transmission lines as they are commonly thought of in the narrowest sense -- a two-conductor system supporting a TEM mode (which can be modeled using the Telegrapher's equations). It would be good for these two articles to be coordinated with the definitions.
In my own personal experience, I have always used "transmission line" to mean a two-conductor system, such as a coaxial cable or a twin-lead line, or a microstrip line. I have usually used "waveguide" to mean a hollow metal pipe waveguide, but I also realize that the term 'waveguide" can be more general. For example, one can have a "dielectric rod waveguide". One can also have a " coplanar waveguide," which in essence is simply a transmission line (albeit not with an exactly TEM mode, but a quasi-TEM mode).
I think it is relatively uncommon to use the term "transmission line" to mean something other than a two-conductor system. Presumabley a "transmimssion line" is something that obeys "transmission line theory", and this theory is all based on the theory of a two-conductor system (i.e., the Telegrapher's equations).
I would propose that in the waveguide article continue to state, as it does now, that the term waveguide is general, but that usually in common usage it means a hollow metal pipe. The article could then state that further disacussion in the article will be confined to this special class of waveguides. A more detailed discussion of other classes of waveguides could then be found in the links to other webpages. I would also propose that the article state in the beginnning that transmission lines are a special type of waveguide that consist of two parallel conductors, which is capable of supporting the TEM mode (or quasi-TEM mode if inhomogeneously filled) and which obeys (either exactly or approximately) the Telegrapher's equations. The waveguide article would then give a link to the transmisson-line webpage.
I would propose that the transmisson line article state that the term 'transmission line" can sometmes be a general one, but that normally the term is restricted to mean a two-conductor waveguiding system that can support a TEM (or quasi TEM) mode, which obeys the Telegrapher's equations. It should then state clearly that all further analysis in the article will be restricted to this type of system. —Preceding unsigned comment added by Elee1l5 ( talk • contribs) 21:53, 7 October 2010 (UTC)
Thank you for pointing out this other webpage -- I didn't realize (until I read more carefully later on in the article) that there was this other webpage for electromagnetic waveguides (I agree, it probably should be called Waveguide (microwave)). In view of this, I agree with Steven, the present article should not be restricted at all to microwave waveguides (metal-pipe waveguides) but should overview all of them. However, the article should make this aspect very clear at the beginning, and give a link to the microwave waveguide webpage early on, to minimize confusion between the two webpages. If this is the intent, however, to keep the present webpage focused on more general waveguides, then some of the later material in it should probably be moved to the other webpage (on microwave waveguides) or modified in some way -- for example, the discussion on impedance matching. I believe that this is what Steven was saying early on. Depending on how general the present webpage is intended to be, the structures do not have to even be limited to those that are translationally invariant. Certainly many waveguiding structures are periodic structures. This aspect is not discussed at all. I would also still recommend the minor clarification edit to the transmmission line webpage. Elee1l5 ( talk) 00:21, 9 October 2010 (UTC)
Okay, that's fine. A periodic structure (discrete translational symmetry) will support guided waves in general, and the definition of a waveguide can be taken as a structure with such symmetry. Maybe we shouldn't say that such symmetry is required, though, in order to have a guided wave existing on a particular structure. There could be cases, for example, where the structure is not physically periodic, but electrically it behaves as a periodic one at some frequency due to the nature of the discontinuities, and thus it supports a guided wave at this frequency. Of course there are also trivial cases where the structure is not periodic but the fields are zero in the region where it is not periodic, so a guided wave exists. Elee1l5 ( talk) 19:35, 11 October 2010 (UTC)
Another interesting class of guided waves are "leaky waves," which radiate (leak power) as they propagate. They can exist on both uniform and periodic structures. In microwave terminology, a guided wave on an open structure (e.g. microstrip line) is "bound" if there is no radiation, while a leaky mode is fundamentally unbound. Normally when most people use the term "guided wave" I believe that they mean either a wave inside of a closed structure (e.g., rectangular waveguide) or a bound mode on an open structure (e.g., the HE11 mode on a cylindrical dielectric rod, or the quasi-TEM mode on a microstrip line). I'm not sure if we wish to broaden the discussion of guided waves to include leaky waves.
Back to the main issue -- editing the webpages. I am recommending minor edits to the Transmission Line and Waveguide (electromagnetism) pages, including changing the name to Waveguide (Microwave) as suggested by Catslash. For the Waveguide webpage, I suggest that you, Steven, might be the best candidate to make the changes, if you accept such a duty. Probably the highest priority, in my opinion, is to address the sections where the content is labeled as being in dispute. Do we need some kind of a consensus before proceeding? Elee1l5 ( talk) 22:11, 12 October 2010 (UTC)
In general I agree with Steven Johnson's suggestion,
But rather than breaking the article up by wave equation, which has little meaning to most people, does it make sense to refer to applications instead? Optical waveguides fall under EM but they deserve a separate subarticle because there's a wealth of applications and technologies. 206.47.231.164 ( talk) 18:36, 26 April 2011 (UTC)
This whole article is in very very poor shape, one of the worst I have come accross in Wikipedia. Quality is naturally in contrast to the length (not depth) of discussion here. It is such a fundemental component and intersting and important transmission line type. Why folks who have very little to contribute, marginally informed, take it upon themselves to edit articles I will never know. As someone who has actually designed and built transmission lines of all kinds, including waveguides, and who makes a living engineering such circuits, I would like to clean things up a little but I am afraid of wasting effort given the dedication of non-contributers to non-contribute here. What does impedance matching have anything to do with waveguides? How can an artcicle like this not include waveguide sizes and standards and frequency bands? Usually copper? Even a freshman EM book has a better explanation of propagation properties. How about countless waveguide components, from filters, to couplers, to magic tees, to loads, irises, transformers, etc.? I suppose all were busy dissecting "transmission lines"... —Preceding unsigned comment added by 173.77.162.40 ( talk) 05:06, 24 February 2011 (UTC)
a bit should be added about how the holes in the microwave oven cannot contain the frequency (a waveguide not tuned to the freq acts as a reflector), and removes most of the radiation whilst letting shorter wavelengths through like light. i do not know the term for this kind of blocking.
i wrote "most" because of the article written called "light sneaks through small holes", it can get through when its 7% of a wavelength wide. i also read that if the hole is less then 100% of a wavelength then you get attenuation. perhaps show a graph of how much gets trough depending on % of wavelength. — Preceding unsigned comment added by Charlieb000 ( talk • contribs) 02:24, 9 October 2011 (UTC)
This whole article is messed up. — Preceding unsigned comment added by 138.163.0.42 ( talk) 00:03, 1 July 2014 (UTC)
The section on mathematical waveguides references something called a "bound state", but without enough information for an inexperienced layman (me) to figure out what that means. The terminology does not appear in the 'main article' for the section, either. KE7KTO ( talk) 20:58, 15 May 2017 (UTC)
Waveguide rotary joint is a single paragraph which could benefit by moving here to give it context. -- Wtshymanski ( talk) 20:53, 6 August 2017 (UTC)
Yet another SD that has been reduced from something that makes sense to something entirely useless. Blind rule-following is so much more important than helping the reader. Spinning Spark 10:44, 8 June 2022 (UTC)
Editors should bear in mind that short descriptions are not intended to define the subject of the article. Rather, they provide a very brief indication of the field that is covered, a short descriptive annotation, and a disambiguation in searches.The SD for this article, for example, could be "Type of telecommunications equipment". – Jonesey95 ( talk) 16:15, 20 June 2022 (UTC)
What is elongate? The waveguide is longer than it is wide? They don't have to be, though that would be usual. Gah4 ( talk) 04:28, 22 June 2022 (UTC)