What is Electromagnetic Interference : Types and Methods To Prevent

Over the years, radio communication has significantly evolved. It is the basic method through which wireless communication is done. It transmits information wirelessly with the help of radio waves and electromagnetic waves. The waves which are generated from the transmitter will propagate through a wireless medium to reach the receiver. Antennas act as transducers that convert the electrical signals into electromagnetic signals and vice verse. One of the challenges faced by this technology is the damage caused by ‘noise signals’. Noise signals are the short duration radiofrequency signals produced externally either by man-made methods are naturally. When these signals picked up by antenna’s will cause the degradation of the communication systems. One of such disturbance is the Electromagnetic Interference.

What is Electromagnetic Interference?

The sudden discharge of electrical energy like during lightening, storms generate short-duration radio frequency waves in the atmosphere. If an antenna is operated in this environment, then these transient signals will be picked up by the antenna. Hence, they interfere with the original communication signals will cause distortions and loss of information. This is also the cause behind the crackle heard on an amplitude-modulated radio receiver during electrical storms.

When these noise signals cause damage to the electrical circuit by giving raise to electromagnetic induction or electrostatic coupling, it is called Electromagnetic Interference. The external source can be either a human-made source or a natural source. The disturbance can damage the electrical circuit or stop it’s functioning. When data signals get affected it may lead to an increase in the error rate, total loss of the data. Electromagnetic interference( EMI) can affect the AM radio, FM radios, mobile phones, televisions, radio astronomy, etc…

Different Types

Electromagnetic interference is also known as Radio-frequency interference. Based on the source and bandwidth of the external noise signal, magnetic interference is classified into four types. In terms of bandwidth, EMI is classified as Broadband EMI and Narrowband EMI. Narrowband EMI is caused due to intended transmissions such as radio stations, TV stations or mobile phones whereas, broadband EMI is caused due to unintentional radiations such as radiations from the sun where a continuous generation of the arc is observed.

Based on the source of the interference, Electromagnetic Interference is of four types. Intentional EMI, Unintentional EMI, Intrasystem EMI, Intersystem EMI.

 Intentional EMI

This EMI is generated intentionally by the equipment. Some of such equipment are Radars, radio transmitters, jammers, etc…These devices generate electromagnetic energy. Such devices are used in electronic warfares. This type of EMI is also called as Functional EMI.

 Unintentional EMI

The sources of this EMI are man-made but they are not designed to generate electromagnetic energy. Still, these devices radiate electromagnetic energy. Some of such devices are DC motors, electrical controllers, engine igniters, computers, power lines, welding machines, etc…. This type of EMI is also known as non-functional.

 Intrasystem EMI

The voltage or current spikes that appear on power cables and power harnesses cause self-jamming and undesirable emission coupling within a system. This leads to the EMI in the system.

 Intersystem EMI

This EMI can be observed in the systems that are operating within a wide frequency range from 50Hz to several GHz.

Methods to Reduce Electromagnetic Interference

In today’s era, with a developing industrial environment, electronic devices, signal processing circuits, power wirings, and other electrical devices usually interact with each other. This leads to the generating of noise and EMI in the circuits which can degrade critical measurements.

To protect the system from damages caused by EMI certain precautions are to be taken. Good grounding and shielding techniques can save signals from degradation.

To reduce the EMI in the circuits the elements to be looked after are to eliminate the noise source, eliminate or upgrade the receiving device that is affected by the noise signals, checking of coupling channel between the source and receptor.

Cable shielding is done to protect the equipment from capacitively coupled interference. Inductive coupling and twisted pairs method are used to reduce the magnetically coupled interference.

With the increase in the use of electromagnetic sources in the equipment, the concern and effects of electromagnetic interference are also increasing. Today electromagnetic interference is effecting lots of systems like the transit systems, the medical systems, train systems, communication systems, etc… Ambient electromagnetic sources affect the sensitive electronic equipment in the vicinity of the source. A high powered electromagnetic pulse source can destroy electrical or electronic equipment near the source. There is a need to consider and keep a check on the operation and interoperability of the products used in our markets. Give an example of an Electromagnetic source?