[SI-LIST] Shielded loop parasitic coupling

From: Douglas Smith <doug@xxxxxxxxxx>
To: emc-pstc <emc-pstc@xxxxxxxx>, SI-List <si-list@xxxxxxxxxxxxx>
Date: Wed, 04 Jun 2008 19:39:59 -0700
 Hi Everyone,
I have posted the latest Technical Tidbit on my website
http://www.dsmith.org[1].  It should be interesting to EMC folks who use
magnetic field probes and to SI people as well since magnetic loops are very
useful at finding board layout issues by signal injection thorough mutual
inductance. The link to the article is the picture at the bottom of the page
at http://www.dsmith.org[2] . I have two more Technical Tidbits coming on
shielded magnetic loops. When the series of 4 articles is finished, it will
be obvious that apart from measuring in the far field (in this case I mean
much farther from the antenna than the size of the antenna which can be much
further than the conventional definition of 1/6 wavelength) there are
seriouslimitations on shielded magnetic loops due to their lack of E field
rejection in many cases in the near field. You can also see my 1999 IEEE EMC
Symposium paper at:

Signal and Noise Measurement Techniques Using Magnetic Field Probes (~600K
pdf file)


Technical Tidbit - June 2008
The Square Shielded Loop - Part 2, Parasitic Coupling
(Electric Field Shielding of Magnetic Loops Is Not Always Effective!)

Abstract: Shielded magnetic loops are used to reduce electric field coupling
to the loop and square magnetic loops are useful for coupling signals into a
PCB or measuring noise in a circuit. However, significant electric field
coupling can still occur with shielded loops. One case of electric field
coupling between a pair of shielded loops is presented which results in a
significant resonance between the shielded loops. Such a resonance can cause
errors in signal injection used for troubleshooting circuits.

Doug
-- -------------------------------------------------------------- ___ _ Doug
Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _
TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 |
q-----() | o | Email: doug@xxxxxxxxxx[3] \ _ / ] \ _ / Web:
http://www.dsmith.org[4]
-------------------------------------------------------------- 

--- Links ---
   1 http://www.dsmith.org
   2 http://www.dsmith.org
   3 mailto:doug@xxxxxxxxxx
   4 http://www.dsmith.org
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[SI-LIST] Shielded loop parasitic coupling

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