What is electromagnetic shielding? Why shield?
发布日期 : 2021-08-25 19:40:26
Shielding is the metal isolation between two space regions to control the induction and radiation of electric field, magnetic field and electromagnetic wave from one region to another. Specifically, shielding is used to surround the interference sources of components, circuits, assemblies, cables or the whole system to prevent the outward diffusion of interference electromagnetic field; Shield the receiving circuit, equipment or system to prevent them from being affected by external electromagnetic field. Because the shielding body absorbs energy (eddy current loss), reflected energy (interface reflection of electromagnetic wave on the shielding body) and counteracts energy (electromagnetic induction generates reverse electromagnetic field on the shielding layer, which can counteract part of the interfering electromagnetic wave) to the external interfering electromagnetic wave and internal electromagnetic wave from wires, cables, components, circuits or systems, Therefore, the shield has the function of reducing interference.
(1) When the frequency of interfering electromagnetic field is high, the eddy current generated in metal materials with low resistivity is used to counteract the external electromagnetic wave, so as to achieve the shielding effect.
(2) When the frequency of interfering electromagnetic wave is low, materials with high permeability shall be used, so as to limit the magnetic line of force inside the shield and prevent it from spreading to the shielding space.
(3) In some cases, if it is required to have good shielding effect on both high-frequency and low-frequency electromagnetic fields, different metal materials are often used to form multi-layer shielding.
