# What is Electromagnetic Interference and its Reduction Techniques?

Omkar Phatak
Last Updated: Mar 19, 2018
You may not know what is electromagnetic interference, but you have certainly encountered it when conversing on your cell phone or listening to a radio. Electromagnetic interference (EMI) manifests itself as the static, random noise that you hear through your cell phone or radio. It is the causative agent of 'bad reception'. Genesis of all types of interference can be traced to the property of electromagnetic induction, caused by any type of electromagnetic waves emitted in the surrounding of any electronic circuit.
What is Electromagnetic Interference?
Telecommunication is made possible through radio waves which are traveling electromagnetic waves. Every wireless communication device, including cell phones, radio, GPS tracking devices and satellite communication devices rely on radio waves for transmission and reception of signals. What leads to electromagnetic interference is the property of these radio waves to superimpose on each other or interfere with each other.
If you know how a radio works, you'll know that its antenna is tuned to receiving a certain band of radio frequencies. All signals in that range are received by the antenna, irrespective of what source it's radiated from. Any other electric source that transmits electromagnetic radiation in those frequency bands, will cause interference in the reception of that antenna.
If your remember some elementary physics and particularly your course in electromagnetism, every changing electric field gives rise to a magnetic field and every oscillating electric field gives rise to a magnetic field. That is how electromagnetic waves travel through space. They need no transmission medium. Any received electromagnetic wave generates an emf (electromotive force) in the antenna conductor which leads to noise in the connected circuit. The absence of selectivity in reception of electromagnetic waves leads to interference. This problem plagues amplitude modulated (AM) radio broadcasts, which possess selectivity.
Types of Interferences
Depending on the frequency ranges over which an interference extends, it can be classified into two types: 'Narrow band interference' and 'Broadband interference'.
Narrowband Interference
This is electromagnetic radiation broadcasted by TV and radio stations, as well as cell phones. These types of interferences are confined to certain select frequency bands and are therefore known as narrow band interferences. Their occurrence being limited to select frequency bands, these type of interferences are easier to confine or exclude.