*1130 PRINTER 171-241 v2 3/13/03 4:04 PM Page 58 Quietshield Shielding Products . Decades of advancing interconnections and signal conditioning technology gives Spectrum Control a uniquely effective perspective on EMI and its control. Since the best time to control noise is before it starts, we ve developed a simulation capability that helps eliminate EMI problems at your earliest design stage, prior to board fabrication. Quiet Board Noise Reduction Printed Circuit Gaskets Boards are another innovative product from Spectrum Control. These shielded printed circuit boards utilize an enhanced Copper Polymer shield to provide the noise filtering effect of discrete bypass capacitors without added inductance. This unique Quietshield D Profile Gaskets board-coating technology eliminates the frustration of failing emissions certification, without resorting to multi-layer ground planes. All at real cost savings over other board-level fixes. In combination with our Filtering, Shielding, I/O Gaskets - D and TVSS products, Spectrum Control can solve EMI problems while providing you with increased design flexibility, reduced time-to-market and peak system performance. Quietshield P Profile Gaskets Index Page Shielding Theory and Introduction .................................229 Quietshield Gaskets ............................230 Quietshield D Profile Gaskets.........231 Quietshield R Profile Gaskets Quietshield P Profile Gaskets .........231 Clips ...................................................231 Quietshield R Profile Gaskets.........232 Quietshield L Profile Gaskets .........232 Quietshield L Profile Gaskets I/O Gaskets - D...............................233 Custom Shielding Products................234 EMI Shielding Tapes...........................235 Part Number Index.............................236 EMI Shielding Tapes CERTIFIED SPECTRUM CONTROL INC. 8031 Avonia Rd. Fairview, PA 16415 Phone: 814-474-2207 Fax: 814-474-2208 Web site: www.spectrumcontrol.com 228 SPECTRUM CONTROL GmbH Hansastrasse 6 91126 Schwabach, Germany Phone: (49)-9122-795-0 Fax: (49)-9122-795-58 Gaskets & Shielding*1130 PRINTER 171-241 v2 3/13/03 4:04 PM Page 59 Shielding Theory and Introduction Shielding Theory The shield will continue to function as long as there are Electromagnetic shielding is used to prevent electromagnetic no holes in the electromagnetic shield which would allow signals such as radio signals from leaving or entering a box the currents to flow from one side of the shield to the other. or enclosure. Signals inadvertently emitted by an electronic Holes are a necessity in an electronic enclosure. Connectors, device can cause distortion or interruption in normal radio wires, and cables are needed to transmit information to and communications in a localized area. This is the basis of from electronic devices. Doors and covers are needed to most laws and regulations concerning electromagnetic get access to components to maintenance, service, and interference. In addition, normal radio signals can cause keypads may also be required. The problem is that all of unprotected electronic devices to malfunction. Depending these items cause openings in the shield which reduce the on the devices function, a malfunction in the device could performance of the shield. be a minor inconvenience such as static on a radio, or life threatening such as the malfunction of a life support system Special devices such as shielding gaskets, shielding at a hospital. ventilation panels, shielded filtered connectors, and shielded switches minimize the effect of a hole in the shield. Introduction The length of the hole and wavelength of the signal that needs to be shielded are the major factors determining the The electromagnetic shield in most cases is the electronic shielding effectiveness of an electronic enclosure. The housing itself. The housing/shield forms a metal cage around distance between spotwelds, or screws which hold a metal the electronic circuits in a device. Most of the electromagnetic housing together count as long narrow holes. Higher frequencies signal is absorbed with a small portion (3 to 10 dB) of the (lower wavelengths) flow more easily through smaller holes, signal reflected off the metal housing. Most of the absorbed and so the highest frequency needed to be shielded is the signal creates alternating currents at radio frequencies travels frequency of concern when designing shielding. on the surface of metal. This allows the electromagnetic shield to keep signals from outside the enclosure on the Aperture versus frequency charts can give a rough outside of the shield and signals from inside signals on the estimate of the shielding effectiveness of a metallic inside of the shield. electronic housing. Shielding Effectiveness 100. 40 dB 20 dB 60 dB Wavelength to 10. Frequency 80 dB 11 .01 .001 100 KHz 1 MHz 10 MHz 100 MHz 1 GHz 10 GHz 100 GHz Frequency SPECTRUM CONTROL INC. 8031 Avonia Rd. Fairview, PA 16415 Phone: 814-474-2207 Fax: 814-474-2208 Web site: www.spectrumcontrol.com 229 SPECTRUM CONTROL GmbH Hansastrasse 6 91126 Schwabach, Germany Phone: (49)-9122-795-0 Fax: (49)-9122-795-58 Aperture Length (Wavelength) - Inches Gaskets & Shielding