IEEE 1302-2019 pdf free.IEEE Guide for the Electromagnetic Characterization of Conductive Gaskets in the Frequency Range of DC to 40 GHz.
The ideal electromagnetic shield is an infinitely conductive enclosure with no apertures or penetrations of any kind. Functional requirements and practicalities of design and construction prevent this ideal from being realized. Penetrations for power, signals, and ventilation as well as access apertures for calibrations, controls, and adjustments could be incorporated into an enclosure preventing it from being an ideal enclosure. An enclosure should include all of the intended design features when evaluating it for its shielding effectiveness.
Electromagnetic energy exits or enters the shield at apertures, along conductive penetrations, and through imperfect seams. To restrict this coupling of energy to levels sufficiently low to comply with regulations and to permit interference-free operation, these unwanted coupling paths shall be closed. Filters are used on the penetrations: screens and covers may be used over apertures. Seams and joints require special attention, however. For shielding, metal flow processes such as welding, brazing, and soldering are the preferred methods for making joints and seams. Many situations arise, however, where these techniques cannot be used and direct metal-to-metal contact does not provide an adequate electromagnetic seal. In these cases, an electromagnetic interference (EM I) gasket should he installed in the joint.
EMI gaskets are conductive materials designed to conform to joint surfaces and provide a low-impedance path. EMI gaskets are made from a wide variety of materials: beryllium copper, galvanized steel, stainless steel, electroplated steel, aluminum, and conductively loaded polymers.
(lasket types include spring fingers, spiraled hands, perforated sheets, knitted wire mesh, conductive fabric, reinforced foil, and oriented wires. Materials added to polymeric binders to achieve conductivity include copper, silver, carbon, aluminum, and nickel as flakes, powders, wires, and coated spheres. The shapes available include sheets, strips, washers, tubes, and customized geometries.
The term “EMI gasket” is consistent with the generic industrial definition of a gasket. The electromagnetic fields being shielded impinge on the conductive materials of the enclosure. The incident field induces currents in the enclosure walls. Seams represent discontinuities in shield current paths with resulting voltage differentials across the seams. The purpose of the EMI gasket is to reduce the voltage differential across the seam because the strength of the field emanating from the scam is directly proportional to this voltage.
Depending upon function and application, electronic equipment operates in an extremely wide range of electromagnetic environments (EMEs) in terms of both intensity and frequency. The environments can vary from that of the home to the battlcficld. Because there is no “one sizetypc fits all” gasket. the challenge facing equipment designers is that of choosing the most efficient and cost-effective gasket for their particular application.
An essential parameter in this selection process is the degree to which the gasket prevents electromagnetic energy impinging on one side of the metal joint containing the gasket from coupling through the joint to the other side (i.e.. the gasket’s electromagnetic shielding capability). Many factors determine the electromagnetic seal provided by an EMI gasket, including the following:
a) Gasket material
b) Gasket construction and geometry
c) Geometry of the jointa.IEEE 1302 pdf download.