Flexible dielectric waveguides with powder cores

Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz using thin-wall polymer tubing filled with low-loss, high-dielectric-constant powders. Absorptive losses of the order of 10 dB/m were measured at 94 GHz. with nickel-aluminium titanate and barium tetratitanate powder in polytetrafluoroethylene (PTFE) lightweight electrical tubing. Bending losses at 94 GHz were negligible for curvature radii greater than 4 cm. M.H. Kuhn´s (1974) theory of three-region cylindrical dielectric waveguide was used to calculate dispersion curves for the lower-order modes for several combinations of dimensions and dielectric constants. Good agreement was obtained between experimental and theoretical values of guide wavelength. A scheme is proposed for classifying hybrid modes of three-region guides based on the ratio |E_z/H_z|. For two-region guides, this reduces to E. Snitzer´s (1961) familiar scheme