Radiation characteristics of flexible circular dielectric waveguides in Q-band

In the millimeter wave frequencies of the Q-band, radiation losses of flexible circular PTFE rod and tube waveguides are measured with the variations of parameters such as operating frequencies, dielectric areas of guiding cross sections, curvature radii of the bending, and bend profiles of the S- and U-bend. We determine the radiation losses of the flexible waveguides, which current theory is not able to predict in the regime of some small curvature radius, and the lower limits of the curvature radii at which additional losses are not generated. The results can be explained by the concepts of the fractional power flows in the surrounding free space region of the guides.