Conducted Emission
Conducted emission is the high frequency noise produced by a device being carried out over the supply and signal cables. From that point on the cable is both a route distributing the noise through the plant and an antenna putting it into the air. The countermeasure is to stop the noise with a filter at a point close to the source.
In a switching circuit the current is cut and restored rapidly every cycle. This fast change produces a wideband noise current on the supply line, which spreads along the cables. The noise travels in two forms:
- Differential mode: it flows in opposite directions in the outgoing and return conductors; it is suppressed with capacitors placed at the input.
- Common mode: it flows in the same direction in both conductors and returns via the chassis; it is suppressed with a common mode choke and a ferrite.
For a wireless remote control the equivalent is range, directly. If the receiver supply comes from a noisy line, the noise is carried right up to the receiver board and raises the noise floor. Practical measures: separate the receiver supply from the noisy driver line, put a filter at the supply input, add a ferrite to the cable and do not leave the cable unnecessarily long. The closer the filter is placed to the source, the less noise gets onto the cable.
Context where this term is used: Wireless remote control installation: pairing, relay, safety