Measurement of dielectric and radiation losses for flexible circular dielectric waveguides in Q-band

Experimental results are presented for the dielectric and radiation losses from flexible circular PTFE waveguides in the Q-band. The dielectric and radiation losses from rod and tube waveguides were found to depend strongly on the design parameters, such as the operating frequency, area of the dielectric region in the guiding cross sections, and curvature radii of the bending. The dielectric losses from the straight guides showed a relatively good agreement with the theoretical results. The radiation losses with a small curvature radius, which cannot be predicted using current theories, were determined based on the differences between the measured insertion losses and the dielectric losses. The validity of the current results was confirmed based on the fractional power flow ratios in each region of the waveguides.