R&M Data Center Handbook

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With the “EMC” parameter “coupling attenuation” the difference between the systems becomes very clear. The
Cat 6 system deviates widely from the necessary values, while the newer UTP systems meet the requirements.
Here too, there is a clear difference between the shielded and unshielded cabling systems. In international standardization,
TCL is used as the EMC parameter in unshielded systems instead of the coupling attenuation that is
used with shielded systems. The comparison of values for TCL and coupling attenuation of Systems 0 – 2,
however, puts this practice into question. That is because the relatively small difference in TCL between System 0
and 1 or 2 makes a huge difference in the coupling attenuation (Pass for TCL, Fail for coupling attenuation).
Based on these poor results, no EMC measurements were carried out with System 0 for the remainder of the study.
As is common with all EMC investigations, cabling systems cannot be examined for EMC aspects on their own,
but only in connection with the active components as a total system. The following active components were used:
• Switch: Extreme Networks; Summit X450a-24t (Slot: XGM2-2bt)
• Server: IBM; X3550 (Intel 10gigabit AT server adapter)
Both servers, which created data traffic of 10 Gbit/s, were connected to a switch through the cabling. The figure
shows a diagram of the test set-up.
Functional diagram of the test set-up
In order to be able to test the EMC properties from all sides, all data-transmission components for the test were
installed on a turntable (d = 2.5 m) in an anechoic EMC test chamber. An anechoic test chamber is a room that
prevents electric or acoustic reflections by means of absorbing layers on the walls, and it shields the experiment
from external influences. A 19” rack containing the switches and the servers was placed in the middle of the
turntable, with an open 19” rack with patch panels on both sides. The panel and active components were
connected with 2 m patch cords. Each end of the tested 90 m installed cables was terminated to one of the RJ45
panels. To achieve a high degree of reproducibility and to have a well-known test set-up, the cables were fixed to
a wooden cablerack that was suggested as a test set-up by CENELEC TC 46X WG3. The rack was located behind
the 19” racks.
Basically, this is a system set-up that simulates the situation in a data center.
Radiated power in accordance with EN 55022
This test is mandatory in the EU’s EMC directive and thus has the force of law. The operation of equipment and
systems that do not pass this test is forbidden in the EU.
The test is designed to recognize radiated interference from the tested system that could impair the operation of
receiving equipment such as broadcast radios, TVs and telecommunication equipment.
Page 150 of 156 © 08/2011 Reichle & De-Massari AG R&M Data Center Handbook V2.0