Some possibilities and limitations of graded dielectric loading. As a means of reducing loss in coaxial cables

Barlow has suggested that the attenuation coefficient of a coaxial cable might be reduced by a suitable dielectric loading. This suggestion is studied for the case of a dielectric whose permittivity is a linear function of radius. It is found that a decrease in attenuation is possible if the ratio of the outer conductor radius to the wavelength is large enough, and if the permittivity increases with increasing radius. No decrease is possible if the permittivity decreases with increasing radius.