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Method to Evaluate the Ability of Conductive Polymer Grommets to Remove RF Currents From Cable Shields

IP.com Disclosure Number: IPCOM000037099D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Petix, SM: AUTHOR [+2]

Abstract

The removal of common mode currents from cable shield can be accomplished by using a grommet made of a conductive polymer which contacts the cable's shield on the grommet's inner surface and a mounting plate on the grommet's outer surface; the RF current can then be conducted from the cable's shield to the mounting plate and ultimately frame ground, and thus preventing unwanted radiation.

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Method to Evaluate the Ability of Conductive Polymer Grommets to Remove RF Currents From Cable Shields

The removal of common mode currents from cable shield can be accomplished by using a grommet made of a conductive polymer which contacts the cable's shield on the grommet's inner surface and a mounting plate on the grommet's outer surface; the RF current can then be conducted from the cable's shield to the mounting plate and ultimately frame ground, and thus preventing unwanted radiation.

Evaluation of the RF attenuation characteristics of conductive polymers can be done directly using the following method. The measurement setup is shown in the figure. It consists of shielded cable 2 held vertically with grommet under test 3. The grommet is mounted in a plate which is attached to the ground plane
4. The cable shield is attached to the center conductor of a coaxial cable 5. The shield of cable 5 is connected to a box 6 which is connected to the ground plane
4. Coaxial cable 5 is connected to the tracking generator which is synchronized to the spectrum analyzer. The spectrum analyzer monitors antenna 7, which is mounted on a tower 8 that allows the antenna to be scanned vertically. Dimensions "h" and "d" are recommended to be 1m and 3m, respectively. They must not change throughout the duration of the test.

The tracking signal generator delivers the RF current which leaks past the grommet and up cable 2; the resulting RF field level is then picked up by the spectr...