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2

Electromagnetic compatibility (EMC)

2.1

Introduction

For as long as electronic transmission equipment such as radio, television, and telephone has been

in existence, it has had a history of susceptibility to interference from other electronic devices. Legal

regulations on interference suppression (electromagnetic and radio frequency interference, EMI

and RFI) have been in existence since 1928. These regulations protect transmission paths and re-

ception equipment by limiting the emitted interference.

In view of the increasing number of electrical and electronic appliances in use, not only the princi-

ples of interference suppression must be observed, but also, in the sense of electromagnetic com-

patibility (EMC), it must be ensured that all equipment is able to operate simultaneously without

problems. EMC is defined as the ability of electrical equipment to function satisfactorily in its elec-

tromagnetic environment without affecting other equipment in this environment to an impermissible

extent.

The European Communities’ EMC Directive (89/336/EEC) came into force on the 1. 1. 1996. It has

been transformed into corresponding legislation in the individual EU (European Union) member

states. With this, it has become mandatory to design electronic equipment to comply with the pro-

tection objectives of this Directive; i.e. to meet the requirements for electromagnetic emission and

electromagnetic immunity as laid down in the corresponding EN standards (European Standards).

The concept of EMC includes both electromagnetic emission (EME) and electromagnetic immunity/

susceptibility (EMS), see fig. 3.

Fig. 3

EMC terms

An interference source may generate conducted or radiated electromagnetic energy, i.e. conducted

emission (CE) or radiated emission (RE). This also applies to the propagation paths and to the elec-

tromagnetic susceptibility of disturbed equipment.

In order to work out economical solutions, it is necessary consider both phenomena, i.e. propaga-

tion and susceptibility, to an equal extent, and not just one aspect, e.g. conducted emission.

EMC = Electromagnetic

compatibility

EME = Electromagnetic

emission

EMS = Electromagnetic

immunity/susceptibility

CE

= Conducted emission

CS

= Susceptibility to

conducted emission

RE

= Radiated emission

RS

= Susceptibility to

radiated emission

EMC

EME

EMS

CE

CS

RE

RS

Emission

Susceptibility

Conducted

Radiated

Interference

source

Disturbed

equipment

Propagation

General Technical Information