What is Electromagnetic Interference (EMI)

Electromagnetic interference (EMI), also called as Radio Frequency interference (RFI) is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. EMI degrades or limits the effective performance and reliability of electronic circuits. EMI protection circuits are necessary in critical applications such as healthcare equipment, aerospace control systems, defense/military electronic equipment, and in automotive safety systems. EMI also affects wireless communication (transmission and reception) of AM/FM radio, cell phones, satellite internet, computers, and television reception but the effect is not severe.

What are Types of Electromagnetic Interference (EMI)

Radiated Electromagnetic interference (EMI) or radio frequency interference (RFI) are two types, Narrowband interference and Broadband interference. Narrowband EMI interference usually arises from intentional transmissions such as radio and TV stations, pager transmitters, cell phones, etc. Broadband EMI interference usually comes from incidental radio frequency emitters. These include electric power transmission lines, electric motors, thermostats, bug zappers, etc.

Broadband EMI noise is stronger at low frequencies and diminishing at higher frequencies, though this noise is often modulated, or varied, by the creating device in some way. Broadband EMI/RFI noise is very difficult to filter it effectively once it has entered the receiver chain.

Conducted electromagnetic interference is caused by the physical contact of the conductors as opposed to radiated EMI which is caused by induction (without physical contact of the conductors).

Electromagnetic Compatibility (EMC)

Electromagnetic Compatibility (EMC) is defined as the ability of an equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment.