What is RF Shielding, Everything You Need to Know

As the world becomes increasingly dependent on wireless technology, the need to protect against radio frequency interference is now more important than ever. RF shielding is one of the most effective ways to do so, with its use cutting across many industries. Here, we explore the basics of RF interference shielding and its application today.

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Table of Contents

What is RF Shielding?

RF Shielding refers to the blocking of electromagnetic waves that are in the radio frequency range, which is usually between 3 kHz and 300GHz. In today’s world where technology is advancing rapidly, wireless communications have become an integral part of our lives. As a result, radio frequency (RF) signals are constantly surrounding us.

But while these signals provide us with great convenience and access to information, they can also cause interference and other problems due to their high electromagnetic fields. To combat that, RF shields are developed. These serve to protect against the resulting interference.

How Does RF Shielding Work?

An RF shield is a type of material that can block electromagnetic radiation and reduce its effects on electronic equipment and systems. RF interference shielding works by absorbing or reflecting radio frequency signals away from a designated area, as the below sections explain.

RF Reflective Material

An RF reflective material works through the principle of Faraday’s Cage. This is where an external electric field causes charges to be redistributed on the surface of a material.

RF reflection can be achieved by using electrically conductive materials such as sheet metal, aluminum foil, or wire mesh that partly or completely surrounds the shielded environment.

RF Absorptive Material

An RF absorptive material, on the other hand, practically isolation and shielding the RF signal instead of reflecting it. This is a material with high magnetic permeability, such as steel or mu-metal, and that can be used in various forms.

This type of RF barrier works by absorbing the magnetic field of the RF signal, dissipating it as heat, and thus reducing its intensity. The deeper the material is, the higher its absorption rate.

How to Shield RF Signals

How is shielding used in various industries? The application of RF blocking strategies ranges from military and aerospace to medical and telecommunication or consumer electronics. In these industries, the radio frequency shielding material is used in one of the following ways.

PCB RF Shielding

This is, by far, the most common way of using radio frequency shielding. By covering the circuit board of electronic devices with an RF shield, you can drastically reduce and contain interference caused by the radio waves.

PCB RF shielding is typically done using metal cans or boxes. It can also be in the form of painted coating, foam, conductive fabric, or conductive elastomer. The type of shielding method depends on the level of protection required, or the environment of the electronics.

RF Shielding in Transformer

RF shielding in transformer construction involves the use of various techniques such as the use of conductive metal strips to shield the primary and secondary windings, the use of copper shielding flux bands, and even the placement of metal enclosures around transformers.

This type of shielding prevents stray RF radiation from interfering with the operation of other electronic components that may be nearby. In addition to the use of shields, proper grounding is also needed when it comes to transformer shielding.

RFI Cable Shielding

When it comes to cables carrying signals, such as coaxial cables, the use of RF shielding is also very common. RF wire shielding typically involves wrapping the cable in a protective conducting layer made from metal foil or braid.

RFI cable shielding can also involve the use of specialized conduits and connectors that provide additional protection against interference. These are typically used in cases where complete RF protection is vital, such as data centers, automation systems, and aerospace facilities.

RFI Shielding for MRI

An MRI is highly sensitive medical equipment that requires effective shielding. This is typically achieved through the use of thick metal RF shielding walls and other special materials such as ferrite absorbers, which absorb the energy from radio frequency signals and dissipate it as heat.

Note that the purpose of RF shielding for MRI rooms is not only to reduce the amount of interference that MRI machines are exposed to, but also to protect persons from potential radiation exposure.

RF shielding test
RF shielding test
Resource: https://www.youtube.com/watch?v=wLo3HcW9x1g

RF Shielding Effectiveness

How effective are the mentioned techniques in containing or blocking radio frequency signals? To ensure performance and quality, RF shielding companies usually employ specialized testing procedures to measure the effectiveness of their products. This is usually indicated in dB or decibels, where the higher the dB value, the more effective the shielding.

RF Shielding Testing

In order to evaluate the performance of an RF shield, testing needs to be conducted. This normally involves using test equipment that simulates different types of radio frequency signals and measures their levels both inside and outside the shielded area.

  • Based on the data obtained during RF testing, a shielding effectiveness value is calculated and compared to industry standards for that particular type of shield.
  • In some cases, the shield may need to be modified or improved in order to achieve optimal performance.
  • RF shielding testing is essential to ensure that the shield is providing sufficient protection against interference, as well as meeting any safety or regulatory requirements, such as that of the FCC.

Shielding Effectiveness dB

The effectiveness of different RF shielding techniques is normally measured in decibels (dB): the higher the dB level, the greater the protection against interference. However, the exact amount of shielding required will depend on the environment and application.

  • For example, copper and silver shields offer excellent shielding effectiveness with higher dB levels. This can be in the form of sheet metal, braids, or screens.
  • Aluminum RF shielding offers medium to good shielding. Steel too.
  • Carbon materials provide lower shielding, and are usually used as filtering materials.
  • In some cases, a combination of different shielding materials may be required in order to achieve the desired level of protection.

Conclusion

The application of RF shielding or RF blocking strategies is widespread, and their use can be found in many different industries. By using effective shielding materials, it’s possible to reduce interference from external radio frequency signals, as well as protect sensitive equipment and even people from potential radiation exposure.

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