effect
Shielding materialFactors affecting shielding effectiveness
From the shielding effectiveness calculation formula given above, some practical guidance conclusions can be drawn for engineering. Based on these conclusions, we can decide what shielding materials to use and what issues to pay attention to. The conclusions given below may seem disorganized and impractical at first glance, but upon closer analysis of the third and fourth points above, it can be found that these conclusions are all interconnected. A deep understanding of the following conclusions is crucial for structural design.
1) The better the conductivity and magnetic conductivity of the material, the higher the shielding effectiveness. However, actual metal materials cannot balance these two aspects. For example, copper has good conductivity but poor magnetic conductivity; Iron has good magnetic conductivity, but poor electrical conductivity. What materials should be used, and whether to focus on conductivity or magnetism depends mainly on reflection loss or absorption loss for specific shielding;
2) When the frequency is low, the absorption loss is very small, and the reflection loss is the main mechanism of shielding effectiveness. It is necessary to maximize the reflection loss as much as possible;
3) Reflection loss is related to the characteristics of the radiation source, and for electric field radiation sources, reflection loss is significant; For magnetic field radiation sources, the reflection loss is very small. Therefore, the shielding of magnetic field radiation sources mainly relies on the absorption loss of materials, and materials with higher magnetic permeability should be selectedShielding material.
4) Reflection loss is related to the distance between the shielding body and the radiation source. For electric field radiation sources, the closer the distance, the greater the reflection loss; For magnetic field radiation sources, the closer the distance, the smaller the reflection loss; Correctly determining the nature of the radiation source and deciding whether it should be close to the shielding body or the principle shielding body is an important aspect of structural design.
5) When the frequency is high, absorption loss is the main shielding mechanism, which is not related to whether the radiation source is an electric field radiation source or a magnetic field radiation source.
6) Electric field waves are easy to shield, followed by plane waves, while magnetic field waves are difficult to shield. Especially low-frequency magnetic fields (below 1KHz) are difficult to shield. For low-frequency magnetic fields, high permeability materials should be used, and even materials composed of high conductivity materials and high permeability magnetic materials should be used.
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