#002 EMI Suppression ~ Why does noise emission occur? Suspect a parasitic component ~

Have you ever wondered why circuit noise occurs even though it was designed properly?

You thought “I was calculated by the circuit design simulator and confirmed the required specifications were satisfied”, “Frequency components of potential noise sources have also been taken into account”, and then “Now it’s perfect!”. However, when you made a prototype and measured it, there was a parade of unwanted noise emission. Have you ever had such experience?

This is because electronic circuits do not work according to the circuit diagram in the first place. And the higher the frequency goes up, the more the effect becomes remarkable.

The occurrence of the emission is deeply related to parasitic elements that are not shown in the circuit diagram.

When L, C, R, ground, and wiring resonate and become noise transmission paths or antennas, an unwanted noise is not enough suppressed and results in a conducted or a radiated emission. This means that the circuit diagram and the actual circuit behavior are different.

Therefore, the first step in EMI suppression is to identify the difference between the ideal and the reality of the operation of the circuit.

EMI: Electro-Magnetic Interference

 

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