EMC Basics

What is EMI/EMC?

EMI/EMC is the acronym of ElectroMagnetic Interference/Compatibility. Its concern is the ability of electronic equipment to work satisfactorily in the electromagnetic environment (immunity) without introducing intolerable electromagnetic interference to that environment (emission).

Computer screen distortion caused by your cellular phone, cross-talk between phone lines, and electrostatic discharge (ESD) are some examples of EMI problems.

EMC is concerned with the generation, transmission and reception of electromagnetic energy. These three aspects of the EMC problem form the basic framework of any EMC design. A source (also referred to as an emitter) produces the emission, and a transfer or coupling path transfers the emission energy to a receptor (receiver), where it is processed, resulting in either desired or undesired behavior. Interference occurs if the received energy causes the receptor to behave in an undesired manner.

Importance of EMC

EMC has become increasingly important recently because of its wide ranging industrial and more general societal (for instance medical) implications. Meeting EMC standards is a basic requirement for any electrical and electronical device before placement on the market. EMC problems are thus main concerns of the telecommunication, electronics, automobile industry.

EMC Testing

There are four types of EMC test: radiated emission, radiated immunity, conducted emisssion and conducted immunity.

The radiated emission test system includes equipment under test (EUT), an antenna and the signal analysis device. The induced voltage from antenna is measured and the data is used to calculate the field strength by antenna factor.

An immunity test, requires an electromagnetic source to generate the desired environment. This source is linked to the EUT either by radiated or by conducted method. Additionally, a monitor is required to know if the EUT is working well.