Notes on Methods of Transmitting the Circular Electric Wave Around Bends

The tendency for energy to be converted out of the circular electric wave in bent round pipe may be avoided by one of three general approaches: (1) by removing the degeneracy between TE01 and TM11, (2) by converting to a normal mode of the bent guide at both ends of the bend, and (3) by utilizing dissipation in the unwanted modes to prevent power transfer to them. All three approaches are discussed. Normal attenuation in round pipe should be effective in moderating straightness requirements. Elliptical guide and special waveguide structures may be used to negotiate intentional bends; bending radii in the range one to 1,000 feet appear acceptable at 50,000 mc for waveguides 3/8-inch to 2 inches in diameter, respectively.