Introduction and History of Electromagnetic Interference
– Interference from intentional and unintentional transmissions has been a problem since the early days of radio communications.
– The International Electrotechnical Commission (IEC) established the International Special Committee on Radio Interference (CISPR) in 1933 to address EMI.
– The FCC in the US imposed legal limits on electromagnetic emissions from digital equipment in 1979.
– The European Union adopted the EMC Directive in the mid-1980s to standardize technical requirements for products.
– Many countries now have similar requirements for electromagnetic compatibility (EMC) regulation.
Types and Coupling Mechanisms of Electromagnetic Interference
– EMI can be human-made (artificial) or natural.
– Types of EMI include continuous wave (CW) interference, audio frequency interference, radio frequency interference (RFI), and broadband noise.
– The four basic coupling mechanisms of EMI are conductive, capacitive, magnetic or inductive, and radiative.
– Conductive coupling occurs through physical contact of conductors.
– Capacitive coupling happens when electric fields induce interference.
– Magnetic or inductive coupling occurs when magnetic fields induce interference.
– Radiative coupling is caused by the radiation of electromagnetic fields.
Effects and Sources of Electromagnetic Interference
– EMI can degrade the performance of electrical circuits or even cause them to stop functioning.
– In data paths, EMI can lead to an increase in error rate or a total loss of data.
– AM radios, mobile phones, FM radios, televisions, and observations for radio astronomy and atmospheric science can be affected by EMI.
– Changing electrical currents and voltages from both human-made and natural sources can cause EMI.
– Examples of human-made sources include ignition systems, cellular networks, and industrial equipment.
– Natural sources of EMI include lightning, solar flares, and auroras.
EMI in Specific Applications
– Older radio technologies and analogue amplitude modulation are more susceptible to interference.
– Digital radio systems incorporate techniques to improve resistance to interference.
– Interference to consumer devices can be caused by a variety of sources such as transmitters, transformers, and wireless devices.
– EMI in integrated circuits can be reduced through various techniques such as coupling energy to larger objects and using bypass capacitors.
– RF immunity and testing involve the use of filters, special layouts, and anechoic chambers to reduce interference.
– RFI in radio astronomy is a major concern due to transmitters on and around Earth, as well as natural sources of interference.
– RFI on environmental monitoring, such as weather radar operations, can be caused by adjacent transmissions or insufficiently regulated 5G adoption.
Regulations and Standards for Electromagnetic Compatibility
– Regulations and standards exist to ensure the proper functioning of electronic devices in the presence of EMI.
– The International Telecommunication Union (ITU) defines interference and classifies it as permissible, accepted, or harmful.
– The FCC in the US regulates the susceptibility of consumer electronic equipment to RFI and EMI.
– Techniques such as ferrite core noise suppressors and integrated power factor correction can help suppress EMI.
– Frequency bands important for radio astronomy are protected by regulation, but concerns about interference still exist.
– The introduction of Wi-Fi and 5G has raised concerns about interference and the need for stricter regulations. Source: https://en.wikipedia.org/wiki/Electromagnetic_interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both human-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares, and auroras (northern/southern lights). EMI frequently affects AM radios. It can also affect mobile phones, FM radios, and televisions, as well as observations for radio astronomy and atmospheric science.
EMI can be used intentionally for radio jamming, as in electronic warfare.
