EMI Basics

EMI is caused by unwanted, or interfering, currents and radio waves that find their way into an electronic system or device. Its effects can be disruptive, or even destructive.  And any piece of electronic equipment, from computers and small motors to radios and cellphones, can emit EMI. EMI can also be due to natural sources such as lightning.

EMI can affect our communications and power infrastructures, undermining our services and even causing failures. But many people are not aware of these effects and their connection to the day-to-day issues they may themselves be experiencing with technology. There’s a tendency instead to just accept the issues as ‘just how it is’. In many cases, systems that we depend on may be malfunctioning due to interference without us even realizing it. 

The effects of the high frequency pulsed signalling which is now typical of modern communications and control technologies can be difficult to track, measure or predict (Electromagnetic Interference Testing (EMI) Basics – Part 1 | EMC Live). Random coupling into nearby circuitries can result in corrupted data and control errors; when the errors are minor, they may remain undetected until their cumulative effects result in more obvious, and apparently inexplicable problems. Similar issues may exist in any environment in which chaotic or intermittent interference sources are present.

Our reliance on technology will continue to increase, and so there will be more and more electronic systems in closer proximity to one another, and operating at higher frequencies than ever. Everything is becoming interconnected either deliberately or unintentionally, so the effects of EMI on our technologies are being amplified more than ever before. 

The ability of digital RF devices to share a common environment without any impairments to their functionalities or inter-operability is often referred to as wireless co-existence (FDA requests attention for wireless coexistence and RF interference risks | Philips Engineering Solutions). In these cases, the effects of mutual EMI on devices need to be considered both at the physical and protocol layers. It’s not difficult to imagine why this would be a critical factor in environments such as hospitals, where high concentrations of wireless monitoring devices are present. 

A recent example of wireless co-existence issues is the USA’s FAA decision to effectively delay 5G deployments near certain US airports (5G and Aviation Safety | Federal Aviation Administration (faa.gov)). The carriers were planning to implement 5G services over the lower C-Band (3.7-3.98 Ghz) portion of the spectrum, which is to close to the upper C-Band (4.0-4.4 Ghz) used by the radar altimeters of large aircraft (5G and Aircraft Safety: How Simulation Can Help to Ensure Passenger Safety (ansys.com)). Obviously, it would be important to have confidence that a large aircraft landing in poor visibility would not become unable to read its own altitude just because someone made a cell call.

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