Propagation characteristics of elliptical dielectric-tube waveguides

The propagation characteristics of the elliptical dielectric-tube waveguide are investigated theoretically. Expressions are derived for power flow, energy storage and power loss using a perturbation method. Numerical results on power flow, attenuation and group velocity are presented for the dominant and some higher-order modes. Thin-wall tubes are found to have less attenuation than thick-wall tubes of the same dielectric cross-sectional area. In the case of the even dominant mode, tubes with constant dielectric area as well as constant overall area exhibit decreasing attenuation with increasing eccentricity.