#003 EMI Suppression ~ Three factors of noise emission. Take countermeasures in upstream ~

Noise emission is caused from three factors:

  1. Noise source
  2. Conduction path
  3. Radiating element

If you take measures against any of these three, you can stop the emission.

1 includes a clock of the CPU and the switching operation of the power supply, etc.
2 can be PCB wirings or lead wires, which can also be propagated by crosstalk between adjacent wires.
For 3, PCB wirings and lead wires act as antennas, radiating noise into a space. Be careful if the wiring is λ/4 + nλ/2 in length.

Among the above three factors, you need to select the method that is easy and effective to suppress the emission. In general, the essential solution is to take measures on the upstream side. Rather than preventing the noise from being radiated, it is a better idea to prevent the noise from being transmitted to the radiating element, and even better to prevent the noise from being generated than to prevent the noise from being transmitted to the radiating element.

 

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