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Very High Speed Co-Axial Cable

IP.com Disclosure Number: IPCOM000036897D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Johnson, RA: AUTHOR [+3]

Abstract

This cable construction incorporates significant air fraction into the active dielectric cross-section of the cable, yet at the same time presenting a stable uniform cross-section with the center conductor centrally located in order to create and maintain an ideal overall geometry of a co-axial transmission line. The latter is important for Zo characteristic impedance control and stability. This significant fraction of air is beyond standard foam or porous dielectric material technologies.

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Very High Speed Co-Axial Cable

This cable construction incorporates significant air fraction into the active dielectric cross-section of the cable, yet at the same time presenting a stable uniform cross-section with the center conductor centrally located in order to create and maintain an ideal overall geometry of a co-axial transmission line. The latter is important for Zo characteristic impedance control and stability. This significant fraction of air is beyond standard foam or porous dielectric material technologies.

This new concept creates the design of a very fast co-axial cable (speed inversely related to the square root of the dielectric constant, with air/vacuum being the lowest value of one) by using a spring/braid combination shield and two spirally wrapped expanded PTFE filaments (low dielectric porous material filaments) about the signal center conductor, as per the figure. In the construction of this cable matrix, these filaments are spirally wrapped in counter- directions (and at different wrapping rates, shown as 2:1 in the figure) along the axis of the center conductor. The different wrapping rates cause multiple crossings of the filaments to occur, in the example of the figure, 4X within the period of the filament with the slower wrapping rate. This is important for creating a stable symmetrical cross- section, and at the same time guaranteeing the incorporation of a large fraction of air into the cross-section.

In addition, the rigid shield of...