Talk:Waveguide

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Reverted changes by ANom OF DUBIOUS AND AMBIGUOUS NATURE. FrankB 20:34, 14 July 2005 (UTC)

Funny how this page is so littered with 'disputed' tags when nearly every single aspect of physics' factual accuracy is disputed. Being wrong is just another step on the path to being right. —Preceding unsigned comment added by 67.98.176.66 (talk) 20:45, 7 February 2011 (UTC)

directionality

The article says ... guides waves by restricting the transmission of energy to one direction. Most waveguides are bidirectional, though some work different in the two directions. Especially there is a directional coupler. Most of the time, though, they are bidirectional. Gah4 (talk) 05:24, 6 September 2023 (UTC)

Agreed. And then there are two dimensional waveguides. And waveguides that do not completely confine the waves. And intentionally leaky waveguides. Constant314 (talk) 09:08, 6 September 2023 (UTC)

So, I think it wants something like one dimension, which would allow for two directions. I suppose there are 2D waveguides, and those could have a section. Gah4 (talk) 13:03, 6 September 2023 (UTC)

The power planes of a circuit board are 2D waveguides. A current filament between the planes produces a cylindrically expanding wave. Constant314 (talk) 15:07, 6 September 2023 (UTC)

I think of them as 2D transmission lines, but then transmission lines are a subset of waveguides. And especially, for the case you indicate, radial transmission lines. Some people only consider hollow waveguides for a waveguide article. I think this one doesn't, but would have to read carefully to see. Gah4 (talk) 20:30, 7 September 2023 (UTC)

They also support higher order modes. Constant314 (talk) 03:01, 8 September 2023 (UTC)

Unusual waveguide structures

A recent edit archives discussion of the Waveguide rotary joint. Reminds me that I know about waveguide vacuum valves, that can close off a waveguide when needed, and yet allow full power (25MW, 0.1% duty cycle) when open. I don't think that goes in this article, but maybe one article for unusual waveguide structures or devices would be worth doing. Gah4 (talk) 20:35, 7 September 2023 (UTC)

Can we remove template: "This section needs additional citations for verification"

I added many additional citations to Impedance matching section. Is there agreement to remove template: This section needs additional citations for verification? If there is agreement, please remove the template. Thanks ~~ TMM53 (talk) 21:05, 1 January 2024 (UTC)

• Done. Thanks for the improvements.

Constant314 (talk) 21:25, 1 January 2024 (UTC)

Infinite tube

"A waveguide (or tube) is defined as type of boundary condition ..." That is nonsense of course. A waveguide is not a boundary condition. Does anybody know what is intended here? Constant314 (talk) 04:09, 9 July 2025 (UTC)

Agree. I think I fixed with worst of this but it is still below par. Johnjbarton (talk) 15:44, 9 July 2025 (UTC)

I think the definition of a tube needs to be elaborated. I presume that the walls of the tube are considered to be made of conductive material like copper, gold, or silver. A hollow tube with glass walls can also be a waveguide but I guess it is ruled out as a tube since some of the can be nonzero outside of the walls. Constant314 (talk) 16:29, 9 July 2025 (UTC)

Yes, materials matter, but I guess glass could be an acoustic wave guide. I'm not clear that the EM and acoustic cases really share anything other than "waves" and "waveguide". No source cited here support having both in the same article. Johnjbarton (talk) 20:36, 9 July 2025 (UTC)

I would be in favor of restricting the article to electromagnetic topics.

And then there is a coaxial cable. Waveguide or not? And if it is a waveguide, is it a tube? Constant314 (talk) 22:54, 9 July 2025 (UTC)

I found the full text | here. Regarding the definition of a tube:

• let S be a region in three-dimensional space which is swept out by the rigid motion of a two-dimensional disc D. The disc D may have arbitrary shape and may have holes. For the theorem to apply, X) must have the additional property that the plane containing the disk D intersects the boundary of 2) normally.

That would appear to include a coaxial cable. Constant314 (talk) 23:12, 9 July 2025 (UTC)

They further require a Dirichlet boundary condition which simply requires that the boundary condition be fixed. I don't think that rules out a dielectric waveguide. Constant314 (talk) 23:18, 9 July 2025 (UTC)

Dielectric is waveguide if it is total internal reflection. I am not so sure what happens if it isn't. Coaxial cable is waveguide but not hollow waveguide. Sometimes waveguide is short for hollow waveguide. There is also a single wire metal waveguide, where the wave travels on the outside. (And sometimes unintentional in the case of coaxial cable.) Gah4 (talk) 05:00, 10 July 2025 (UTC)

Oh, yes, fiber optics duh. I'm pretty sure that coax is treated as a waveguide, lots of theory around coax feeding antenna. Jackson has this material, but I'm not near my copy now. Johnjbarton (talk) 20:19, 10 July 2025 (UTC)

I would treat all those as waveguides. Also, the majority of things we think of as waveguides would satisfy the definition of a tube. However, the reference cited is a primary reference; I haven't seen much mention of tube waveguides in other sources.

As for Mathematically, any tube with a bulge, where the width of the tube increases, admits at least one non-propagating bound state., I want to say that is common knowledge. If you dent a waveguide, you cause higher order modes to form in the vicinity of the dent. If your waveguide supports more than one propagating mode, the dent can cause them to couple. Constant314 (talk) 21:38, 10 July 2025 (UTC)

Maybe I am missing something here. The most common metal waveguide is a rectangular tube. Cylindrical waveguides exist, and maybe are closer to the usual thought for tube. Gah4 (talk) 08:00, 11 July 2025 (UTC)

What do you think that you are missing? Constant314 (talk) 13:48, 11 July 2025 (UTC)