98100325

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Introduction

Radio frequency interference (RFI) and electromagnetic interference (EMI) are two of the major aspects of electrical interference that must be considered when designing circuits, electronic systems and communications systems. RFI and EMI are caused by electrical fields that are created by electrical currents, electromagnetic radiation, or electrostatic fields. Shielding and absorbing materials are materials used to protect against and reduce the effects of RFI and EMI.Generally speaking, shielding reflects or dissipates electromagnetic waves, and absorption absorbs and dissipates the energy.

98100325 Application Field and Working Principle

98100325 application field and working principle for RFI and EMI- shielding and absorbing materials mainly apply in low and high frequency electromagnetic wave, and effectively reduce the unwanted radiative emission, through reflective or absorption effect. Low frequency electromagnetic wave mainly emitted by DC electric field, induced current, and protective equipment’s sparks and high frequency electromagnetic wave mainly emitted by signal equipments, power supply and motors, and high frequency in signal.

The working principle of RFI and EMI-shielding and absorbing materials in low frequency is based on the Faraday cage and the ‘Tunnel Effect’. The Faraday cage is constructed by material mesh, and the wire splits the electric field into internal and external components, as the electric field is 180° opposed transition area. In this wound, as the current is running through, the wire generates a magnetic field which can be considered as secondary current shield around the mesh. And the current reduces the effect that sends out from electric field from outside through the mesh. In addition, the Tunnel Effect, which is the effect of whether the wave passes through the conductive plastic materials.

For high frequency, the working principle of RFI and EMI-shielding and absorbing materials is more effective. Shielding materials generally have resistive coating, and the coating surface of material is covered with thin metal film. When the electromagnetic waves move through the surface, the energy in the electric field gathered there will be conducted, and then lead to disappearance of electric field. To absorb the electric waves, the RFI and EMI-shielding and absorbing materials use conductive elastomer, which are made up of conductive particles embedded inside elastomer, which acts as dampers or springs. When the electric wave enter the material, the electrical field causes the conductive particles to vibrate, which convert the energy in the electric fields to heat, and effectively reduce the energy in the electric fields dissipated out.

Conclusion

RFI and EMI-shielding and absorbing materials play a critical role in reducing the effects of electromagnetic interference which can damage or corrupt electronic components and circuits. 98100325 application field and working principle of RFI and EMI-shielding and absorbing materials effectively reduce the unwanted radiative emission, through reflective or absorption effect. Low frequency electromagnetic wave mainly emitted by DC electric field, induced current and protective equipment sparks are reduced through the Faraday cage and Tunnel Effect while high frequency radiative emission is reduced through the absorbent materials by converting the energy in the electric field to heat.

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