On a similar note, does anyone have a feel for what the approximate
attenuation differences are between a dual shield (foil and braid) and
one or the other as a stand alone shield?
-----Original Message-----
From: Brumbaugh, David [SMTP:[email protected]]
Sent: Friday, July 31, 1998 2:47 PM
To: 'emc-pstc list server'; 'Knighten, Jim'; DiBene, Ted
Subject: RE: Twisted Shielded Pair
The original message sounded to me like Ted was looking for
changes in
the shielding effectiveness when going from 85% to 90% coverage.
However, the answer is the same, the change is not significant.
I have commonly seen 20 dB used as a "rule of thumb" shielding
effectiveness for a TSP. However, I am the first to admit that
this can
be overly simplistic, and that the correct approach is to
determine
transfer impedance of the shield to determine coupling to and
from the
protected circuit. There are lots of papers in the open
literature (IEEE
EMC transactions and EMC symposia) over the last 30 odd years
which
address transfer impedance.
DB
