Attenuation in corrugated circular waveguides. Part 2: Experiment

Measurements of the attenuation characteristics of corrugated circular waveguides in the frequency range 8¿11 GHz are described which support the theory given in Pt. 1 of the paper (see p. 1173). Both cavity techniques and waveguide measurements are deployed, and these lead to attenuation values which are about 40% above the predicted value for an ideal corrugated waveguide. However, it is believed that the discrepancy may be explained by the surface roughness of the metal and other imperfections. The actual measured value of the attenuation of the HE11 mode is just below the theoretical value for the TE010 mode in a comparable smooth-wall waveguide, emphasising the low values being measured. A new method is described for suppressing modes, which is based on the principle of the monomode optical waveguide.