Design of Cylindrical Surface Waveguides with Dielectric and Magnetic Coating

The paper deals with wires whose coating has both dielectric and magnetic properties. Approximate formulae are given for the field concentration, propagation time, group velocity, power distribution, characteristic impedance, losses and maximum transmissible power for such coated wires. The magnetic coat concentrates the field more strongly than does the dielectric one. The field concentration increases quickly with increase of permeability and hardly depends on permittivity. The attenuation is due to the conductive, dielectric and magnetic losses of the guide. The dielectric loss depends also on permeability, and vice versa. The total loss of a given transmission line as a function of field concentration has a minimum, which can be achieved by a coating of appropriate thickness. To determine the maximum transmissible power, two formulae can be used. One determines the maximum transmissible power from the highest permissible value of electric field strength, and the other from the highest permissible degree of overheating. The paper concludes with a description of design procedure for surface waveguides, illustrated by an example.