Propagation of modes in curved hollow metallic waveguides for the infrared

Field configurations and attenuation constants of TE-modes in curved parallel-plate metallic waveguides are calculated numerically. It is assumed that the distance between the plates is much larger than the freespace wavelength and that the radius of curvature is much larger than the distance between the plates. For curvatures not too small the attenuation constant is shown to be inversely proportional to the radius of curvature, but independent of the plate distance. The discrepancy between theory and experimental observations existing so far is hereby resolved.