Question

What is the difference between conducted and radiated EMI?

Answer 1

EMI stands for Electromagnetic Interference, which can cause disruptions in the normal operation of electrical and electronic systems. There are two main types of EMI: conducted EMI and radiated EMI. Here's the difference between them:

1. Conducted EMI:

1. Definition: This is interference that travels through conductors (wires or cables). It happens when unwanted signals or noise flow along the power supply lines, signal lines, or ground paths of a system.
   

1. Cause: Conducted EMI can be generated by devices such as motors, switching power supplies, or any equipment that operates at high frequencies. These devices may emit electrical noise, which travels along the power or signal cables to other equipment.
   

1. Path of Interference: The noise travels through the cables and can affect nearby equipment that is connected to the same electrical network.
   

1. Example: A power supply that creates noise on the power line, affecting other devices connected to the same electrical circuit.
   

2. Radiated EMI:

1. Definition: This is interference that is emitted in the form of electromagnetic waves and travels through the air. The noise can spread out and affect nearby electronic devices.
   

1. Cause: Radiated EMI occurs when an electronic device emits electromagnetic energy that propagates through space. It could be caused by high-frequency signals or poor shielding of electronic circuits.
   

1. Path of Interference: The noise is radiated into the air, and it can interfere with any nearby equipment that is sensitive to electromagnetic waves. It does not need to travel through a physical conductor.
   

1. Example: A poorly shielded device emitting signals that affect nearby radio receivers or other sensitive equipment.
   

Key Differences:

1. Path: Conducted EMI travels through wires or cables, while radiated EMI spreads through the air.
   

1. Effect on Equipment: Conducted EMI interferes directly with equipment connected to the same electrical network, whereas radiated EMI can affect nearby devices without direct electrical connections.
   

1. Mitigation: Conducted EMI can be reduced using filters, while radiated EMI can be minimized using shielding and proper grounding.
   

In short, conducted EMI travels via conductors (wires), while radiated EMI spreads through the air as electromagnetic waves. Both need to be controlled to ensure the proper functioning of electronic devices.