EMI EMC Tutorial:
What is EMI & EMC?
Electromagnetic Interference (EMI):
The process by which disruptive electromagnetic energy is transmitted from one electronic device to another via radiated or conducted paths (or both) is known as Electromagnetic Interference.
The capability of electrical and electronic systems, equipment, and devices to operate in their intended electromagnetic environment within a defined margin of safety and at design levels or performance without suffering or causing unacceptable degradation as a result of electromagnetic interference(EMI).
EMI & EMC Terminology:
A frequency range containing coherent EM radiation of energy useful for communication purposes - roughly the range from 9 kHz to 300GHz. This energy may be emitted as a by-product of an electronic device's operation. Radio frequency is emitted through two basic mechanisms:
- Radiated Emissions - The component of RF energy that is emitted through a medium as an EM field. Although RF energy is usually emitted through free space, other modes of field transmission may be present.
- Conducted Emissions - The component of RF energy that is emitted through a medium as a propagating wave generally through a wire or interconnect cables. Line conducted interference(LCI) refers to RF energy in a power cord or AC mains input cable. Conducted signals propagate as conducted waves.
Immunity - A relative measure of a device or system's ability to withstand EMI exposure while maintaining a predefined performance level.
Radiated Immunity - A product's relative ability to withstand EM energy that arrives via free space propagation.
Conducted Immunity - A product's relative ability to withstand Em energy that penetrates through external cables, power cords, and input-output(I/O) interconnects.
Susceptibility - A relative measure of a device or a system's propensity to be disrupted or damaged by EMI exposure to an incident field. It is due to lack of immunity.
Electrostatic Discharge(ESD): A transfer of electric charge between bodies of different electrostatic potential in proximity or through direct contact.
Line Impedance Stabilization Network(LISN): A network inserted in the supply mains load of an apparatus to be tested that provides, in a given frequency range, a specified load impedance for the measurement of disturbance voltages and which may isolate the apparatus from the supply mains in that frequency range.