EMC/EMI Shielding Explained

Last Updated on April 13, 2022 by Electricalvolt

EMC/EMI Shielding is a method used to safeguard a sensitive signal from external electromagnetic signals. There is a chance of leaking out of the stronger signal during transmission and may link to the weaker signal. Thus, the leaked signal may interfere with surrounding electronics circuitry.

The EMC shielding hinders the EMI/RFI interference between stronger and weaker signals. EMC shielding covers the electronic devices such as IC chips and active components mounted on PCB(Printed Circuit Board).

EMC stands for Electromagnetic Compatibility. A circuit that has EMC compatibility means that a circuit has shielding that prevents EMI interference.

EMC/EMI Shielding Explained

Electromagnetic frequencies can interfere with sensitive electronics and can cause various problems in the electronic system. The EMI affects the communication circuit and also affects the functioning of the electronics circuit. The electromagnetic interference adversely affects all consumer electronics, industrial electronics, and military electronics equipment. Therefore, the shielding of sophisticated electronic circuits is a must for reliable operation.

How Does EMC Shielding Work?

The main objective of the EMC shielding is to prevent electromagnetic interference ( EMI ) and radio frequency interference( RFI ) for the protection of sensitive electronics. In EMC/EMI shielding, a metallic screen absorbs the interferences transmitted through the air. The metallic screen absorbs the RFI & EMI signal and causes the flow of electric current in the screen. The screen has a connection with the earth which provide a low impedance path. Thus, the screen current sinks into the earth.

The screen of the EMI shielding absorbs these transmitted signals before reaching the sensitive circuitry. Therefore, the protected signal is free from electromagnetic interference, thus maximizing shielding effectiveness. For example. smartphones have EMC/EMI shielding, and EMI/RFI interferences do not affect smartphone operation.

Materials used for EMC/EMI shielding

We can use the different types of materials for EMC shielding. The design of the shielding system & its efficacy depends on the type of electronics and frequencies involved. The amount of EMI/ RFI signal reduction and blocking depends on the following factors.

  • Type of screen material used
  • The size of the shielded volume
  • Material thickness

The degree of absorption of EMI/RFI depends on the above factors as each of these factors affects the range and strength of frequencies.

Examples of EMC/EMI shielding

  • Coaxial cable has metallic foil or plaited braid shield built into the wire construction, underneath an outer insulation layer. Further, the other wire bundles can be wrapped in foil. We can also use a ready-made cable braid over the whole construction of the coaxial cable. The connector at both ends of the wire has a metallic cover and braiding or foil connected to the metal to give total coverage.
  • For shielding on PCBs, shielding typically consists of a PCB with a ground plane built into it, and a metal box ( shield can) placed over the sensitive or transmitting elements. The components are then completely surrounded by a Faraday cage arrangement.
  • In devices such as audio speakers, you can see an inner metallic casing used for successfully blocking EMI produced by nearby transmitting devices (such as microwaves and TVs).
  • Shielded twisted pair cable– The shield of the STP cable prevents the EMI/RFI noise.

When magnetic fields are below the 100kHz range, we can use conductive paints and magnetic materials. Sheet metal, metal foam, conductive plastics, and mesh-metal screening are the other methods used for EMC shielding.

It is important to understand which part of the electronic circuit is vulnerable to the electromagnetic frequency spectrum. Then, the screen design must be in accordance with a particular application. The EMC shield can have a solid screen or can have the regularly placed holes or even wire fencing, all of these depend on the frequency of the EMI/ RFI signal.

Applications of EMC/EMI Shielding

We use EMC shielding across a broad range of applications.

  • EMC shielding is very important for safeguarding medical and laboratory equipment because these types of equipment are potentially life-saving, and must be free from any sorts of interference. The EMC shielding is a must for AM/FM emergency service transmission and other telecommunications, data communications, theatre, and ward patient monitoring equipment, and even in-body medical devices such as pacemakers.
  • EMC shielding for RFID Chips
  • Embedded electronics
  •  Electronic system for military, government, and financial systems.

Finally, shielding is indispensable for any sensitive electronic element that requires isolation from the surrounding electromagnetic fields. With advancements in technology, we are using electronics in every field and now, every piece of electronics needs EMI/RFI protection.

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About Satyadeo Vyas

Satyadeo Vyas, M.Tech,M.B.A. is an electrical engineer and has more than 36 years of industrial experience in the operation, maintenance, and commissioning of electrical and instrumentation projects. He has good knowledge of electrical, electronics, and instrumentation engineering.

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