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Electromagnetic Interference(EMI)-Definition, Types, Causes, And Prevention

August 30, 2022
written by Adeel Abbas

There can be unwanted noise or interference in an electrical path or electric circuit caused by an outside source which is called electromagnetic interference.

What is Electromagnetic Interference?

The performance of an electrical circuit may be degraded by interference generated by an external source in the radio frequency spectrum. 

When a cell phone is placed near powered audio equipment or speakers, it can cause noise or a series of beeps to be heard. It is a common example of electromagnetic interference.

In the case of a data path, these effects can range from an increase in error rate to a complete loss of the data. AM radios are frequently affected by emissions. It can affect radio astronomy and atmospheric science, as well as mobile phones, televisions, and radios.

Causes Of EMI

The close relationship between electricity and magnetism is what leads to EMI. There is a small magnetic field produced by all electrical flow. An electrical current can be produced by a moving magnetic field. Electric motors and generators are able to work thanks to these principles.

All electrical conductors can be used to operate radio antennas. In devices far away, high-powered electrical and radio sources can give off unwanted effects. As electronics become smaller, faster, more tightly packed, and more sensitive, they become more susceptible to the effects of these effects, causing EMI.

Types of Electromagnetic Interference

There are three main types of EMI.

  • Narrowband EMI
  • Broadband EMI
  • Conducted electromagnetic interference 

Narrowband EMI

We refer to it as a narrow band of interference frequencies, or even a single interference Frequency. There is a small portion of the radio frequency spectrum occupied by narrowband signals. CW is a type of signal that can happen intermittently or continuously. It usually comes from intended transmissions, such as radio and TV stations or mobile phones.

Broadband EMI

The type of EMI that occurs over broad spectrums is referred to as broadband EMI. It is able to do this because it occupies a large part of the spectrum. It can cause permanent damage to devices if it is the type of EMI that engineers and users are concerned about. Electric power transmission lines are one of the sources of unintentional radiation.

Conducted electromagnetic interference 

Conducted interference is caused by the physical contact of the conductors as opposed to radiated interference which is caused by the conductors not having physical contact with each other. The conductor’s EM field will no longer be confined to the surface of the conductor and will be able to travel away from it. There is mutual inductance between two electromagnetic fields that will result in EMI.

Prevention of EMI

Good quality electronics from reliable suppliers are the best way to prevent the problem. In the United States, the FCC requires that all devices be tested against emission standards to prevent them from causing excessive EMI in other devices; similar rules exist in other countries.

Poorly made, cheap or counterfeit electronics may not be tested properly, making them more likely to cause interference in other devices and more susceptible to interference themselves. The effect of nearby sources can be reduced with modern error correction and filters.