Waveguide Internal Surface Roughness 1

[Gehr]

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

 

[VEBill]

From first principles, these are presumably all in linear proportion:
[ul][li]Wavelength (inverse of frequency)[/li]
[li]Size of waveguide (closest appropriate standard size)[/li]
[li]Roughness requirements[/li][/ul]

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]

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]

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]

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]

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

Dan - Owner

http://www.Hi-TecDesigns.com