Coupling in a dielectric-coated multicoaxial-cable system. An analysis based on a quasi-TEM model

Earlier theoretical studies for crosstalk between two coaxial cables [1, 2] and those in a system of multicoaxial cables in free space [3,4] focus attention on an ideal case where bare coaxial cables are of prime concern. Although in installations coaxial cables are always used with their dielectric jackets (mainly PVC) for obvious electrical reasons, the case of coupling between dielectric-coated coaxial cables has not been studied in the literature. Although the crosstalk methods developed for a multicoaxial-cable system in earlier studies [3, 4] can be extended to analyse complicated practical multicoaxial-cable systems, they are not applicable to this practical case unless the effects of dielectric jackets on coupling have properly been investigated and included in the analysis. In this paper a method, which uses the point-matching technique [5] in terms of harmonic expansion functions for charge densities, is employed to determine the per-unit-length parameters of the tertiary circuits. The results of these studies were used for modifying the earlier crosstalk methods [3, 4] to determine the coupling process between dielectric-coated multicoaxial cables.