Recommended Practice for Measurement of Shielding Effectiveness of High-Per formance Shielding Enclosures
|Publication Date:||1 January 1969|
OBJECT AND SCOPE
The object of this Recommended Practice is to provide uniform test procedures and estimation techniques to determine the relative effectiveness of room-size high performance shielding enclosures. Specifically, uniform practices are designated to determine the effectiveness of an enclosure in the usual shape of a rectangular parallelepiped with edge dimensions ranging from 1.5 to 15 meters. Test procedures are formulated to enable use of commercially available equipment for conducting tests under nonideal conditions, such as within typical facilities used to house the shielding enclosure.
A shield is defined in the IEEE Standards on Industrial Electronics as "material used to suppress the effect of an electric or magnetic field within or beyond definite regions."* A shielding enclosure is a structure composed of such a material. A high-performance shielding enclosure is generally considered to be capable of suppressing by orders of magnitude both the electric and magnetic fields. It is constructed of panels of metallic conducting sheets with provisions for continuous electric contacts between .the panels or doors. Its function may be to provide an interference-free location for the conducting of electromagnetic tests or for the operation of sensitive radio or electronic equipment where large-amplitude unwanted electromagnetic fields would otherwise be present; or it may be to confine generally high-level unwanted radiation produced by electric or electronic equipment to a limited space and thereby reduce the possibility of interference with other equipment.
Tests herein are not intended for obtaining quantitative data for the design of shielding enclosures or for evaluating the shielding effectiveness of materials, though this may be a useful by-product. This Recommended Practice does not specify construction details for shielding enclosures, nor does it suggest methods for calculating the effectiveness of such enclosures.
Uniform practices are provided to determine the effectiveness over the frequency ranges from 100 hertz to 20 megahertz, from 300 to 1000 megahertz, and from 1.7 to 12.4 gigahertz. Where it is desirable only to obtain a general estimate of the effectiveness by employing limited measurements, single-frequency tests are recommended within three standard frequency ranges: a) 14-16 kilohertz, b) 850-950 megahertz, and c) 8.5-10..5 gigahertz.