Browse Prior Art Database

Cable Shielding Effectiveness Set Up

IP.com Disclosure Number: IPCOM000117698D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 94K

Publishing Venue

IBM

Related People

Dieterich, K: AUTHOR

Abstract

The performance of modern computers requires a short cycle time which prerequisite the use of very high frequency signals. Cables guiding those high frequencies must, therefore, be especially qualified.

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This is the abbreviated version, containing approximately 52% of the total text.

Cable Shielding Effectiveness Set Up

      The performance of modern computers requires a short cycle time
which prerequisite the use of very high frequency signals.  Cables
guiding those high frequencies must, therefore, be especially
qualified.

      Effective cable shielding as well as high qualified connectors
are basic requirements in cable design.  Generally HF-cables must
prevent that HF-energy will radiate from a cable or penetrate a
shielded cable by an outside source.  Cables, therefore, must react
analogues to shielded enclosures.  Mostly the correct cables and
connectors are chosen, but it was often found that the connectors
were not assembled correctly which decreases shielding effectiveness.

      The measuring set, described below, makes it possible to
evaluate shielding effectiveness of a complete HF-cable (cable with
connectors) in an easy and fast way.  The test set up can be used for
all shielded cable types, if preparations were done.  Block-diagram
(Fig. 1) shows the set up.  The cable under test (test object) is
attached to highly qualified 50 Ohm coax cables 1 and 2 via the two
adapter units 1 and 2.  Each of the two coax cables are 4 meter long.
The network analyzer, for example HP 8753A feeds, via coax cable 1
and adapter unit 1 a high frequency spectrum into the test object.
The frequency spectrum is adjustable and covers the range 30
MHz-1GHz, depending on the analyzer.  The HF-signal reaches via
adapter unit 2 and coax cable 2 the 50 Ohm terminator.  Coax cable 1
and 2 as well as the two adapter units 1 and 2 are absolutely
HF-tight and, therefore, HF-energy can only ooze at the test object
if there is a shielding leakage.

      Penetrating HF-signals will generate a voltage outside the
shield of the test object and will propagate to the two coax cables 1
and 2.  There it can be measured by a current clamp (for example MDS
21-1 clamp) which is attached to the network analyzer.  MDS 21-2 is
used to suppress signals reflecte...