Glossary of terms

Technical terms

In many of our pages, we talk about conducted emissions and radiated emissions. What do we mean?

Conducted Emissions

Conducted Emissions is a term for radio frequency current that flows on one or more conductors connected to an electric circuit, or alternatively, radio frequency voltage between conductors connected to an electric circuit. Generally, conducted emissions voltage is specified as the voltage that develops when conducted emissions current encounters a 50 ohm impedance.

Why 50 ohms? Most test equipment used in performing radio frequency EMI measurements has an input impedance of 50 ohms.

For the purposes of EMI analysis, conducted emissions are generally of interest over the frequency range 150kHz to 30MHz, because this is the frequency range over which most regulatory agencies specify conducted emissions limits.

External link  In depth reading on conducted emissions  PDF

Radiated Emissions

Radiated Emissions refers to the unintentional release of electromagnetic energy from an electronic device or apparatus. Any electronic device may generate Electromagnetic fields that unintentionally propagate away from the device’s structure. In general, radiated emissions are usually associated with non-intentional radiators, but intentional radiators can also have unwanted emissions at frequencies outside their intended transmission frequency band.

The allowable radiated emissions from electronic devices and apparatus are regulated by various organisations and agencies. Electronic devices that have significant amounts of radiated emissions may interfere with their normal operation or the normal operation of other devices in close proximity. For these reasons, it is important to understand the concepts behind the origins of radiated emissions so that fundamental design techniques can be used to minimise the emissions.

External link  In depth reading on radiated emissions  PDF

Acronyms and abbreviations

Term Definition
dB External link Decibels - a logarithmic unit of measurement
dBm External link Decibel relative to 1 milli Watt
dBuV Decibel relative to 1 micro Volt
EMC Electromagnetic Compatibility
EMI Electromagnetic Interference
LED Light Emitting Diode
CFL Compact Fluorescent Lamp
REIN Repetitive Electrical Impulse Noise
RFI Radio Frequency Interference
SMPS Switched Mode Power Supply

Page updated: 15th August 2021

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