Glossary of terms
In many of our pages, we talk about conducted emissions and radiated emissions. What do we mean?
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.
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.
Acronyms and abbreviations
|dB||Decibels - a logarithmic unit of measurement|
|dBm||Decibel relative to 1 milli Watt|
|dBuV||Decibel relative to 1 micro Volt|
|LED||Light Emitting Diode|
|CFL||Compact Fluorescent Lamp|
|REIN||Repetitive Electrical Impulse Noise|
|RFI||Radio Frequency Interference|
|SMPS||Switched Mode Power Supply|
Page updated: 14th February 2014