EMC - Coupling mechanisms and counter-measures

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An EM interference phenomenon may be summed up in Figure R29 below.

Fig. R29 – EM interference phenomenon

The different sources of disturbances are:

  • Radio-frequency emissions
    • Wireless communication systems (radio, TV, CB, radio telephones, remote controls)
    • Radar
  • Electrical equipment
    • High-power industrial equipment (induction furnaces, welding machines, stator control systems)
    • Office equipment (computers and electronic circuits, photocopy machines, large monitors)
    • Discharge lamps (neon, fluorescent, flash, etc.)
    • Electromechanical components (relays, contactors, solenoids, current interruption devices)
  • Power systems
    • Power transmission and distribution systems
    • Electrical transportation systems
  • Lightning
  • Electrostatic discharges (ESD)
  • Electromagnetic nuclear pulses (EMNP)

The potential victims are:

  • Radio and television receivers, radar, wireless communication systems
  • Analogue systems (sensors, measurement acquisition, amplifiers, monitors)
  • Digital systems (computers, computer communications, peripheral equipment)

The different types of coupling are:

  • Common-mode impedance (galvanic) coupling
  • Capacitive coupling
  • Inductive coupling
  • Radiated coupling (cable to cable, field to cable, antenna to antenna)