Circular Waveguide Upper Cutoff Frequency?

Hi all,

Is there such a thing as an upper cut-off frequency for a circular waveguide operating in T11 mode? Some people are saying to me that due to higher order modes the S21 response of the waveguide may begin to tail off at higher frequencies. Is this correct?

Thanks!

try this link
http://www.rfcafe.com/references/ele...uide-modes.htm
http://www.rfcafe.com/references/ele.../waveguide.htm

http://www.cernex.com/PRODUCTS_NEW/T...de%20Sizes.pdf
http://www.quinstar.com/qcw_circular...d_flanges.html

pl

Yes, as you get high enough you can get more than one mode of propagation. That usually makes the signal unusable (different modes have different propagation velocities). But there are some notable exceptions. You might be passing power into a multimode cavity for industrial heating, and the pressence of more than one mode is not a problem. You might be communicating down a big pipe (like a mine shaft) and even though there is a multimoding, you can still send ~low data rate info down the "waveguide". Stuff like that.