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Andy Chou是一名宝德(Boyd)市场部门经理,在EMI解决方案领域拥有超过5年的工作经验。他还领导“新产品引进”团队,负责研发新兴EMI产品和应用。凭借作为全球技术工程师、大客户经理和产品经理的经验,Andy非常热衷于研究电子行业的EMI管理和随之而来的市场趋势。


简介


Electromagnetic interference (EMI) also known as radio frequency interference (RFI) when in radio frequency, is caused by undesirable radiated electromagnetic fields, or conducted voltages or current from an external source,which interferes with the safe and stable operations of an electronic device. This interference can come from any artificial or natural object that carries rapidly changing electrical currents, like an electrical circuit, the sun or the Northern Lights. This disturbance or interference may interrupt, obstruct, limit or degrade effective electronic device performance. These effects can range from simple performance degradation to a total loss of data or, at worst, devicefailure.

为避免出现这些可能的性能问题,电子设备设计通常加入好几种材料,从而在EMI存在下提高稳定性能。

图1演示了这种设计的屏蔽罩和接地垫圈的具体安装。

EMI来源

Electromagnetic interference can come from a number of different sources and be categorized in a number of different ways. EMI sources can be natural or man-made. They can be categorized by duration like continuous interference or impulse “noise” (noise meaning interference),or categorized by bandwidth (narrow or broad band). How does EMI happen? Normally EMI occurs from a coupling mechanism (or path) caused by one of the following models. The general theory of coupling is shown in Figure 2.

- Conduction by electric current effect: Conducted noise is coupled between two or more components through interconnectingwires like a power supply or ground wires. Common impedance coupling is caused when currents from twoor more circuits flow through the same component or circuit. Most conducted coupling between pieces of equipmentoccurs through AC power lines.

- Radiation by electromagnetic effect: In the near field condition, E field (electric) and H field (magnetic) coupling arediagnosed separately (mainly for electric field issues). In the far field condition, coupling is treated as a plane wave(mainly for radiated electromagnetic field issues).

-电场或磁场效应引起的感应
--电感耦合:磁场耦合由导体中的电流引起。耦合机制可以通过变压器建模。

--电容耦合:电场耦合通过导体之间的电压差引起。耦合机制可以通过电容器建模。

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