Journal of Applied Physics · 1950 · 659 citations · 0 references
EngineeringElectrical EngineeringElectromagneticsMicrowave EngineeringPropagationMicrowave PropagationMicrowave Transmission LinesPropagation In ConductorsPropagation In Dielectric MediaTransmission LinesCoaxial Transmission LinesFinite Conductivity EffectsLossy Transmission LinesSurface Wave LossesSurface WavesTransmission Line DesignTransmission Line LossesTransmission Losses
Two surface wave types are examined: Sommerfeld’s wave guided by a finite‑conductivity cylindrical conductor, which has low attenuation but a very large field extension, and a new wave type not previously studied. The study investigates the applicability of non‑radiating surface waves for transmission lines, focusing on the novel wave type. The novel wave is guided by a conductor coated or threaded with a dielectric layer, producing a field similar to Sommerfeld’s but with controllable extension, and the paper provides design data and validates loss predictions against measurements. While Sommerfeld’s wave offers low loss, its large field limits practical use and requires very high frequencies; the new wave enables low‑loss transmission lines above 100 MHz, with theoretical loss estimates matching measured values.
In this paper the applicability of non-radiating surface waves for transmission lines is investigated. Two types of waves are considered. The first one, originally studied by A. Sommerfeld, is guided by a cylindrical conductor of finite conductivity. Although this wave type has (under comparable conditions) much lower attenuation than the waves in coaxial cables or rigid wave guides, its practical application is restricted by the fact that the extension of the field is very large. Efficient excitation and undisturbed propagation of this wave mode are feasible only for very high frequencies. The other wave type considered in this paper has not been treated in the literature. It is guided by a conductor which is coated with a dielectric layer or the surface of which is otherwise modified; for example, by being threaded. The field of this wave type has a structure similar to that of Sommerfeld's wave, but the extension of the field can be controlled by the surface modification. Thus low loss transmission lines on the basis of this wave type become feasible for frequencies above 100 megacycles. The information necessary for the design of such lines is given and the agreement between the theoretically expected transmission losses and the measured transmission losses is checked.