Page 6 - GETELEC - Products and solutions Catalog

Introduction to EMC

Electromagnetic compatibility (EMC) means the ability of a device, electric or electronic system, to function
satisfactorily in its electromagnetic environment, without introducing intolerable electromagnetic
disturbances to anything in that environment.

Electromagnetic compatibility describes a state of "being a good electromagnetic neighbour":

• Limiting undesired emissions from the device in order to not disturb radio reception or other
devices;

• Being sufficiently immune to disturbances from other devices, or the environment more generally.

1 January 1996: European Directive 89/336/CEE on EMC

26 february 2014: European Directive 2014/30/UE

Fields

An electromagnetic wave is characterised by the oscillation of an electrical field E (generated
by the potential difference between two conductors subject to an electrical current)
and a magnetic field H (generated by an electrical current flowing thought a conductor).

The wave is characterised by its frequency F or its wavelength l.

l=c/F where c = the speed of light = 300,000 km/s.

The higher the frequency (the smaller the wavelength), the more easily conductors become
transmission antennas. So, the nearer a conductor gets to the ideal dimensions
to be an antenna (a whole fraction or multiple of the wavelength), the more it radiates energy
in the form of electromagnetic waves.

Units used:

- intensity of electrical field E in V/m,
- intensity of magnetic field H in A/m.

Frequency 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 3 GHz 30 GHz 300
Frequency bands MHz GHz
Wavelength 1000 km 100 km 10 km 1 km 100 m 10 m 1 m 10 cm 10 mm 1 mm

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