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.
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.
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?