in the solution of high-frequency electromagnetic interference technology, the complete use of shielding solutions more and more can not meet the rules. Because of many equipment, port setting and ventilation, windows and other needs make the actual shielding method is not possible to form a fully shielded cage like faraday cage, port size technology is a major threat to the high frequency of equipment. In addition, there is another technology that bothers people, after the equipment has implemented an effective shielding, external interference technology, although solved, but electromagnetic wave interference technology still exists in the shielding system, even because the shielding caused interference to intensify, and even caused the equipment not to work properly. These are the technologies that shield the existence, and it is precisely because of the existence of these technologies that absorbent materials are useful.
Absorbent material refers to a kind of material that can effectively absorb the incoming electromagnetic wave and make it scatter attenuate, which converts the incoming electromagnetic wave into heat energy or other energy forms through the various loss mechanisms of the material to achieve the purpose of absorbing electromagnetic wave. Unlike shielding solutions, the efficacy is to reduce the amount of interference electromagnetic waves. Can be used alone to absorb electromagnetic waves, but also with the shielding system to improve the high-frequency efficiency of equipment.
Currently commonly used absorbent materials can deal with electromagnetic interference bands ranging from 0.72GHz to 40GHz. Of course, suction materials are also used in higher and lower frequency bands. The absorbent material can be divided into coating type, sheet type and structure type, from the absorbent structure can be divided into electric absorption type, magnetic absorption type, and from the structure can be divided into absorption type, interference type and harmonious vibration type and other absorbent structure. The suction effect of the absorbent material is determined by various electromagnetic mechanisms inside the medium, such as debai relaxation of the dielectric, resonant absorption, resonance relaxation of the interface relaxation magnetic medium wall, electron diffusion and micro-vortex.
The loss mechanism of absorbent material can be divided into the following categories: First, resistive loss, the resistivity loss related to the conductivity of such absorption mechanism and material conductivity, that is, the greater the conductivity, the greater the macrocurrent caused by the carrier (including the current caused by changes in the electric field and the eddy current caused by changes in the magnetic field), which is conducive to the conversion of electromagnetic energy into thermal energy. Second, dielectric loss, which is a kind of media loss absorption mechanism related to electrodes, that is, the "friction" effect generated by the repeated polarization of the medium converts electromagnetic energy into thermal energy consumption. The process of dielectric polarization includes: electron cloud displacement polarization, polar media electro-torque steering polarization, electro-iron field steering polarization, and wall displacement. Third, magnetic loss, such absorption mechanism is a class and ferromagnetic medium dynamic magnetization process related to magnetic loss, such loss can be refined as: hysteresis loss, rotary magnetic vortex, damping loss and magnetic after-effect effects, the main source is similar to the magnetation mechanism of magnetic field steering, magnetic field wall displacement and magnetic field natural resonance. In addition, the latest nanomaterial microwave loss mechanism is a hot spot in the analysis of absorbent materials.
Due to space restrictions, this paper only makes the most minimal description of the loss mechanism of absorbent material, and its detailed description and its structural design and the interference of structure to absorbing effect will be explained in the future article.
In short, the high-speed trend of new technology is leading the world's various lines of electrical and electronic equipment to high-frequency, miniaturization direction trend, high-frequency electromagnetic interference technology will become more prominent, absorbent materials will inevitably have more and more extensive application space.
tage: Shielding material electromagnetic shielding