EMC Question of the Week: August 12, 2024

generic illustration of source, coupling path, and victim necessary for electromagnetic interference to occur

Three of the four electromagnetic coupling mechanisms are proportional to the source current. Which one is proportional to the source voltage?  

  1. conducted coupling
  2. electric-field coupling
  3. magnetic-field coupling
  4. radiated coupling

Answer

The best answer is “b.” Electric-field (capacitive) coupling is proportional to the source voltage. More specifically, the time rate of change of the source voltage (dV/dt).

Conducted (common impedance) coupling is proportional to the source current (times the shared impedance). Magnetic-field (inductive) coupling is proportional to the rate of change of the source current (dI/dt). Radiated fields are proportional to the currents integrated over the radiating structure.

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