Meaning
Electromagnetic interference mitigation relies on sheets or coatings that convert stray radiation into heat through magnetic loss. A magnetic absorber consists of a polymer matrix filled with iron or ferrite particles. These materials are placed directly on noise sources to reduce emissions or on sensitive components to protect them from external fields.
Unlike conductive shields that reflect energy, these absorbers dissipate it.
Attenuation Mechanism
Magnetic loss occurs when the alternating field of an electromagnetic wave interacts with the dipoles in the material. A magnetic absorber converts this energy into thermal energy. This process is effective across a wide range of frequencies depending on the permeability of the filler.
Integration Placement
Physical location determines the effectiveness of the treatment in a compact device. Applying a magnetic absorber to the surface of a high speed microprocessor reduces the radiated noise that could interfere with nearby antennas. In cellular phones, these sheets prevent the battery from coupling with the radio frequency circuits.
Thermal Loading
Dissipating energy as heat adds to the overall temperature of the enclosure. Designers must verify that the magnetic absorber does not cause a component to exceed its maximum operating temperature. While the amount of heat is usually small, it can be significant in airless environments.
The material itself must also be able to withstand the heat without degrading. Adhesives used to attach the sheets are often the first point of failure if the temperature rises too high.
