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Radio Frequency Interference (RFI) and electromagnetic interference (EMI) have vast and varied possible applications. As part of a comprehensive EMI/RFI shielding solution, effective use of shielding and absorbing materials can be instrumental in mitigating many of the fields associated with these types of interference. The purpose of this article is to provide an overview of the various shielding and absorbing materials used in the protection from EMI/RFI, and how to use them effectively in order to minimize the interference.

The Nature of Electromagnetic Interference

In its simplest form, electromagnetic interference (or EMI) is any electromagnetic disturbance generated from an external source that interferes with the operation of an electronic system. Any electronic device or system using a receiver may be affected by EMI, which can cause interference or unwanted noise in the signal. Electromagnetic interference can be generated from a range of electronic sources, such as power supplies, electrical equipment, motors, and other sources of electrical and magnetic fields.

RFI (Radio Frequency Interference) is a type of EMI that occurs when radio signals generated by one device interfere with the performance of a receiver. These radio signals can occur when two devices are operating in close proximity, such as a telephone transmitter and a receiver, but they can also be caused by external sources, such as interference from another radio station or even from nearby electrical equipment.

What are Shielding and Absorbing Materials?

Shielding and absorbing materials are materials that provide protection against EMI/RFI fields by preventing the interference from reaching its intended target. These materials are designed to reflect and absorb the interference rather than allowing it to pass through. The effectiveness of shielding materials depends on their electrical properties, such as conductivity, resistivity, and surface area. The most common materials used for EMI/RFI shielding are conductive metals such as aluminum and copper, plastic films, and fabrics.

Conductive metals such as copper and aluminum are effective at blocking both EMI and RFI by creating a physical barrier between the source of interference and the device being protected. The metal is designed to act like a shield, reflecting the interference away from the device. Copper and aluminum are also used in more complex shielding materials, such as metalized plastic film or coating, which combines the benefits of a metal shield with the lightweight and formability of a plastic material.

Plastic films and fabrics are also effective against EMI and RFI interference, although they provide less protection than metal shields. Generally, these materials are less effective at blocking or deflecting the interference, but are still very useful in blocking or absorbing the energy of the interference.

Application Field and Working Principle

EMI/RFI shielding and absorbing materials have a wide range of applications, from protecting sensitive electronic components from interference, to reducing the level of interference in radio communications. In addition, these materials can be used for a variety of other applications, including shielding medical and industrial equipment from damaging levels of electromagnetic fields.

The working principle of shielding and absorbing materials is relatively simple. The material acts like a shield, reflecting or absorbing the interference and preventing it from reaching its intended target. It is important to note that shielding materials are not 100% effective, and some levels of interference may still be present. Additionally, as the frequency of the interference increases, the shielding material may become increasingly ineffective.

In addition to providing protection against EMI/RFI, shielding and absorbing materials can also be used to reduce the level of noise in a radio signal. Radio noise, also known as ‘hash’, interferes with the signal and reduces the quality of the audio. By using a suitably rated shielding and absorbing material, the interference can be reduced significantly, thereby improving the audio quality.

Conclusion

Shielding and absorbing materials are an integral part of any EMI/RFI shielding solution. These materials provide an effective method for reducing the amount of noise generated from external sources, and protecting sensitive electronics from harmful interference. As technology advances, the development of more effective shielding materials will help to ensure that systems remain resilient in the face of growing interference.

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