EMC Question of the Week: September 4, 2023

microcontroller on a circuit board

When evaluating the noise coupled from a microcontroller, which EM coupling mechanism is NOT likely to be significant?

  1. conducted
  2. E-field
  3. H-field
  4. radiated


The best answer is “d.” Noise can easily be conducted in or out of a microcontroller through its connections to circuit board traces. It can also couple to nearby circuits through the electric or magnetic fields. However, microcontroller packages are generally too small to be efficient sources of radiated emissions. When noise from a microcontroller shows up in a radiated emissions measurement, it is because that noise was conducted or field-coupled out the controller where it was then able to drive something larger that served as the unintentional transmitting antenna.

Various standards designed to measure the "radiated emissions" from integrated circuits (such as IEC 61967-2 and IEC 61967-3) actually measure the near-field coupling from these devices. IEC 61967-2 is a particularly good method for quantifying the field-coupling, while IEC 61967-3 provides useful information related to the conducted coupling from various component pins.

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