Electromagnetic Interference (EMI) & Its Sources

Electromagnetic interference (EMI) is all around us. The static on your radio or the buzzing sound when a cell phone is put near audio equipment is all result of electromagnetic energy. EMI is responsible for causing radiation or induction that disrupts the signals in an electronic device. EMI or RFI primarily causes problems in industrial environments by disturbing the accuracy of instruments. However, EMI can be found all around us.

Now you may ask what exactly is the source of EMI and is it possible to control it. So, let’s find out the answer to these questions. EMI can be produced from anything- from a phone, microwave, and laptops to natural weather conditions. To reduce the impact of EMI/RFI, the shielding technique is used. EMI shields and gaskets help in minimizing the ingress and egress of EMI. Irrespective of where EMI comes from, shielding helps in preventing the disturbances it might cause to the surrounding electronic equipment. The shielding technique works on the principle of the Faraday Cage that involves using an enclosure made of conductive materials to block EMI waves. This is a great technique to reduce EMI in your PCB designs.

Answering the next question, the sources of EMI can be divided into three main categories- Man-Made, Natural, and Inherent. Now, let find out more about these sources of EMI and how they could impact the operation of products and systems we use.

Man-Made EMI

When another electrical device is responsible for causing interference, it is known as man-made EMI. Sometimes, a device malfunctions due to a nearby electronic producing unwanted signals. Likewise, the device itself can be the cause of producing EMI that impacts the performance of other devices. So, when two or more signals are nearby, this type of interference might occur. Also, when playing a radio in a car, it sometimes picks up two stations simultaneously. This happens because the device catches multiple signals at the same frequency. We use several products that can cause or suffer from interferences such as phones, computers, and automobiles. In the industries, the source of electromagnetic interference can be motor starters, heater controllers, AC and DC motors, generators, switching power supplies, power wiring, walkie-talkies, welding, electrostatic discharge, and much more. Besides accidental EMI, sometimes the military intentionally causes electromagnetic signals. The purpose of doing this is to disrupt the functioning of electronic devices in a targeted area.

Natural EMI

Natural EMI occurs naturally, which is not man-made. Natural sources such as weather disturbances often cause interferences with electronic devices. When electromagnetic emission is caused due to natural events on earth or in space, it is known as a natural source of EMI. Lightening, snowstorms, thunderstorms, and solar radiation, are the most common natural causes of EMI.

Inherent EMI

Inherent EMI, also known as Internal EMI is the internal noise or waves produced by the device itself. It happens when the device produces electromagnetic emissions that disrupt its own functioning. This could be caused due to the thermal agitation of electrons inside the circuit that disrupts the functioning of the device.