Shielding is the isolation of metal between two space regions to control the induction and radiation of an electric field, magnetic field and electromagnetic wave from one region to another. Specifically, the interference source is used will shield components, circuit and assembly, cable or whole system surrounded by preventing electromagnetic interference shielding body outward diffusion; receiving circuit, device or system surrounded, to prevent them from the influence of external electromagnetic field. Because of shielding from external wires, cables, components, circuits or systems such as electromagnetic interference and internal electromagnetic wave plays an energy absorption (eddy current loss), reflection energy (reflection of electromagnetic waves on the interface of the shield and energy (on) offset by electromagnetic induction electromagnetic field in reverse, shielding layer can be offset the effect of electromagnetic wave interference), so the shield has the function of reducing interference. (1) when the frequency of electromagnetic interference is higher, the eddy current generated by the low resistivity metal material is used to counteract the electromagnetic wave, so as to achieve the shielding effect. (2) when the interference of electromagnetic wave in low frequency, using high permeability material, so that the magnetic shielding limit in the internal space to prevent the spread of the shield. (3) in some cases, if the high frequency and low frequency electromagnetic fields are required to have good shielding effect, different metal materials are often used to form a multi-layer shielding body.
Electromagnetic wave will interact with electronic components, resulting in interference phenomenon, known as EMI (Electromagnetic Interference). For example, the common "snowflake" on the TV screen means that the received signal is disturbed.
Electromagnetic compatibility (Electromagnetic Compatibility) abbreviation EMC, refers to an electronic device does not interfere with other devices, but also not affected by other equipment. Electromagnetic compatibility is one of the most important indicators of product quality, as well as the safety we are familiar with. The safety of people and property, and electromagnetic compatibility is related to personal and environmental protection.
