#005 EMI Suppression ~ Measures for noise conduction path are EMI filters and ground improvement ~

Once the noise source is identified, the first thing to consider is whether the noise source itself can be suppressed, but if it is difficult to do so, you need to consider a second option: prevent the propagation of the noise from reaching a radiating element. This can fall into three main categories: using a passive filter, using an active filter, and reviewing ground wirings.

The filter commonly used is a passive filter.

Even if it says a filter, one for EMI suppression is not a very complicated circuit; it uses either L, C, or R, or a combination of them.

The reason why ground wirings should be reviewed is because the ground cannot be ideal and always has a parasitic impedance. This can cause an electrical potential difference among the ground wirings, causing unexpected noise current to flow into a circuit. You can avoid this by reducing the impedance of the ground.


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