A Note on Certain Guided Waves in Slightly Noncircular Tubes

Amongst electric waves that can be propagated inside metal tubes of circular cross section there are some with attenuation constants diminishing indefinitely with increasing frequency. The purpose of this note is to discuss what happens to these waves as the tubes are slightly deformed from perfect circularity. The conclusion is that in a deformed tube the attenuation constants of the above‐mentioned waves diminish with increasing frequency until a certain frequency is reached, depending upon the degree of departure from perfect circularity, and then they begin to increase indefinitely with further increase in frequency.