Abstract: An unsymmetrically corrugated TE.sub.01 mode circular waveguide bend. Unsetrical corrugations approximately one-quarter wavelength deep are utilized to suppress energy transfer to other modes inherent in smooth wall circular guide bends. The corrugations are comprised of a plurality of adjacent internal ridges and valleys having substantially parallel walls such that the distance between the parallel walls of the internal ridges are at least twice the distance between the parallel walls of the internal valleys.

Abstract: A TE.sub.01 circular mode waveguide expansion joint, tapered transition dce in which the expansion joint includes a linear tapered section, the greatest diameter of which does not exceed the cutoff diameter for the TE.sub.02 spurious mode. A second taper of the cosine or other suitable type minimizes TE.sub.02 mode generation as the guide diameter increases past the TE.sub.02 cutoff value. The expansion, transition device simultaneously performs the functions of expansion section and waveguide diameter transition for the TE.sub.01 circular mode while minimizing spurious mode generation.