What is electromagnetic interference (EMI)?
What is electromagnetic interference (EMI)?
Before dealing with electromagnetic interference (EMI), one must first understand its causes to prevent it effectively. EMI is unwanted noise or interference in an electric circuit caused by an outside source during the operation of electronics. It is also known as radio frequency interference that could cause electronic devices to perform poorly, malfunction or stop working. For instance, the most common EMI is the electromagnetic leakage generated inside the electronics that interferes with their normal operations. To meet the requirements of electromagnetic compatibility (EMC), EMI should be effectively prevented or reduced so that it does not affect nearby devices or signals.
Unwanted electromagnetic (EM) waves are generated with two component fields when electrons flow through a conductor: electric fields (E-field) and magnetic fields (H-field) when circuit current is transmitted. The source of electromagnetic waves could be natural or man-made. Natural EM waves could be sunlight or lightning, while man-made EM waves could be from wireless communication base stations or radios. Unintentional electromagnetic radiation occurring during product design could also be another source.
Depending on the medium by which electromagnetic waves are transmitted, there are primarily two types of EMI: conducted and radiated.
* Conducted EMI:
interference signals are transmitted via circuits. Electronic devices connected to the same power source would be disrupted.
*Radiated EMI:
interference signals are transmitted through open space without the need for a medium, which could be harder to resolve. Typical solutions include grounding or shielding.
Common EMI regulations
International electromagnetic compatibility test specifications and standards have been formulated to classify electronics into consumer and non-consumer products. For consumer/residential electronics, it refers to the maximum electromagnetic intensity a tested product in operation can withstand/tolerate at a specific distance. As such devices are meant for home use, the limits are usually more stringent. For non-consumer electronics, i.e. industrial or commercial products, greater EMI tolerance than consumer electronics is required.
In the beginning of product design, if the EMI generated by an electronic device in operation is not handled properly, it might disrupt product stability and normal operation. Many medical research articles in recent years have continuously proposed the possible negative impacts of electromagnetic waves on the human body, which has brought many people to pay more attention to the EMI issue and thus had led to the enactment of relevant regulations. If a product cannot meet the international EMI testing standards and regulatory requirements, it will not be released to the market for sale, and hence incurs immeasurable loss.
According to the current product cycle on the market, the life cycle of electronics is getting shorter and shorter. Consumer electronics last about 2 years, and industrial equipment lasts about 5 years on average. The research and development time for a product has been greatly compressed. How to find low-cost and highly efficient solutions to address EMI issues has become a key to successful product design.
