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Electrically-Conducting Shields

October 28th Fact-of-the-Day

Both electrostatic and magnetic radio-frequency fields can be confined to small spaces by means of electrically-conducting shields. Electrostatic fields obviously are short-circuited by conducting shields. However, the means by which a nonmagnetic conducting shield can contain a magnetic field is not so obvious. Radio frequency magnetic flux is able to penetrate an electrically-conducting shield only with great difficulty, because as flux cuts into a conducting material it produces eddy currents that oppose the penetration. The effectiveness of highly-conductive shields depends on their thickness compared to the skin depth of current penetration at the frequency being shielded. Lower-frequency conducting shields must be thicker to have the same shielding effectiveness as higher-frequency shields, because lower-frequency currents penetrate further below the surface of a conductor. ©2004 Martek International All rights reserved.

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