EMC/noise

[MANISH KUMAR BHATT]

Hello

" Why noise is cause of radiation?" What is there inside the noise which causing radiation"
Could any body give more clarification on this ?

Thanks
Manish

[qdrives]

Let my try to put it in simple terms.
Noise are high speed electrical signals. PCB traces are acting like antenna's.
Changes in electrical and magnetic field can cause radiation.
See also https://www.youtube.com/watch?v=Lf51sx6sC0I

[robertferanec]

Everything may cause radiation - also normal signals. But if you have noise, that would be extra radiation which you need to take extra care of (e.g. radiating on extra frequencies which otherwise would not be there).

[MANISH KUMAR BHATT]

Suppose I product is failing at EMC Test at particular frequency (e.g. cisper 22, radiated emission). How can I find the source of radiation in this case? I could be noise/resonance ect. anything.

[robertferanec]

MANISH KUMAR BHATT sometimes you may not find it so easily - there can be number of reasons. What sometimes may help is to power down part of your PCB (e.g. disconnect power from some local circuits, switch off some peripherals) and watch if that helped. That sometimes can help to locate part of the circuit which may be causing the problems, but not always.

[qdrives]

One of the methods I used to find sources of EMC problems at a frequency is by calculating the length of the wave (full, half, quarter) and finding the track/wire which has that length.