AN898 Datasheet, PDF (2/4 Pages) STMicroelectronics – EMC GENERAL INFORMATION

EMC GENERAL INFORMATION
1 EMI AND EMS
Almost every electronic device emits some electromagnetic interference (EMI). These
emissions can be transmitted as electromagnetic radiation or conducted through cables
such as power cords. At the same time, most electronic devices are susceptible to emissions
generated either internally or by other devices.
Receptors susceptible to electromagnetic radiation include communication receivers such as
radio and television, radar and navigation devices or computing devices. The effect of the in-
terference on the receptor depends on several parameters: strength of the source, transmis-
sion medium, distance from the source, coupling mechanisms and degree of susceptibility of
the medium.
Figure 2. EMC Contents: EMI and EMS
EMC
Electromagnetic Compatibility
EMI
Electromagnetic
Interference
EMS
Electromagnetic
Susceptibility
Radiated
Conducted
Radiated
Conducted
VR02102B
Electromagnetic interference (EMI) tests involve measuring the frequency and amplitude of
undesirable signals emitted by the tested equipment. Signal radiated into free space are
called radiated emissions, whereas signals travelling along power cords or other intercon-
necting cables are called conducted emissions.
Electromagnetic susceptibility (EMS) testing is a way to determine the ability of the device
to operate properly in an undesirable electromagnetic environment. These tests use signal
sources and power amplifiers to generate high level fields around a device. Conducted sus-
ceptibility measurements are performed by coupling an offending signal of a specified level
onto cables to try to induce a malfunction into the tested device. Other forms of susceptibility
tests include electrostatic discharge (ESD), transient burst and voltage surge testing.
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