Waveguide Internal Surface Roughness

Question

Waveguide Internal Surface Roughness

Gehr (Electrical)

(OP)

28 Apr 19 16:38

Hi there!
If anyone can clarify the relationship between propagation frequency and internal roughness level of a circular waveguide please?
Regards

VEBill (Military) · Answer 1 · 2019-04-29 12:30:10

From first principles, these are presumably all in linear proportion:

Wavelength (inverse of frequency)
Size of waveguide (closest appropriate standard size)
Roughness requirements

There are probably some factors impacting loss that would not scale in linear proportion.

Speculation Alert -^ .

A Google search of the obvious search terms shows some scholarly articles on the subject.

MacGyverS2000 (Electrical) · Answer 2 · 2019-04-29 15:18:23

Frequency sets your skin depth (e.g., 0.66 microns @ 10GHz), right? So the roughness of your surface can/will have a major effect on how far the signal of interest travels (for a rough surface and a small skin depth, it has to travel over every peak/valley in the surface). Pretty easy to ignore at 1GHz, but difficult to ignore at 100GHz.

Dan - Owner
http://www.Hi-TecDesigns.com

Gehr (Electrical) · Answer 3 · 2019-04-29 16:19:58

Thanks MacGyverS2000. Yes frequency sets the skin depth. Please say what percent of surface roughness be of skin depth not to effect the propagation or say a single digit percentage of loss?

3DDave (Aerospace) · Answer 4 · 2019-05-04 06:48:25

Depends on the length of the wave guide doesn't it? All the waveguide I've seen is extruded and very smooth, but it was for only a few feet.

MacGyverS2000 (Electrical) · Answer 5 · 2019-05-06 15:57:28

For high-efficiency guides, they'll silver coat the inside since it has a slightly lower resistivity.

Dan - Owner
http://www.Hi-TecDesigns.com

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Waveguide Internal Surface Roughness