Date of Award

Spring 2018

Project Type

Thesis

Program or Major

Electrical and Computer Engineering

Degree Name

Master of Science

First Advisor

Nicholas J Kirsch

Second Advisor

Kent Chamberlin

Third Advisor

Michael J Carter

Abstract

Despite the ever-growing amount of fiber optics deployed in wireline communications networks, coaxial cable is still a significant component. It is present in the radio frequency (RF) portion of hybrid-fiber-coaxial (HFC) communications networks typically employed in cable telecommunications (CATV) systems which service the majority of US households. Sheath faults in coaxial cables are a common problem for the industry and lead to unwanted and costly ingress or egress of signals into or out of the network.

Common-mode currents have been previously identified as a source of ingress or egress for a variety of shielded cables in a number of industrial applications. This paper analyzes the electromagnetic properties of coaxial cable sheath faults to demonstrate that common-mode currents are the principal mechanism explaining the observed radiative properties of such faults, particularly in the lower frequency ranges, e.g. the 5-42 MHz upstream band employed by most U.S. cable system operators. Empirical measurements from coaxial test segments of a variety of sheath faults and configurations are shown to be consistent with results from computer simulations and analytical models of the physical samples. These results in turn are found to support conversion between common-mode and differential-mode currents as the primary causative agent.

These findings can be used to better understand the causal mechanisms and requisite conditions for ingress and egress to develop in communications networks, and thereby improve methods to detect, remediate, and prevent sources of network impairment arising from compromised coaxial sheath conductors.

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