EMC - Coupling mechanisms and counter-measures

An EM interference phenomenon may be summed up in Figure R21 below.

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Fig. R21: EM interference phenomenon

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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)