What are the main functions of an electromagnetic shielding room? People who are not familiar with it will naturally have questions. In fact, a shielded computer room is a building space specifically designed to attenuate and isolate energy from internal or external electric and magnetic fields. What are the absorbing materials used to isolate external electromagnetic interference? Let's take a look together~
Let me first say that different electromagnetic shielding devices use different absorbing materials. What are the different shapes of absorbers?
Single layer flat plate shape: foreign The absorbers developed early on were single-layer flat plates, while later absorbers were directly attached to metal shielding layers. They are thin and lightweight, but have a narrow operating frequency range for absorbing electromagnetic waves.
Double or multi-layer flat plate shape: This absorber can operate over a wide frequency range and can be made into any shape. If NEC Corporation in Japan uniformly disperses ferrite and metal short fibers in suitable organic polymer resins to make composite materials, the working frequency band can be expanded by 40% to 50%. Its disadvantages are large thickness, complex process, and high cost.
Wedge shape: The absorber used in the microwave anechoic chamber is often made into a wedge shape (cone shape), mainly composed of polyurethane foam type, non-woven flame retardant type, silicate plate metal film assembly type, etc. As the frequency decreases (the wavelength of electromagnetic waves increases), the length of the absorber also increases significantly. The approximate relationship between a regular sharp edged absorber and L/λ ≈ 1 is that at 100MHz, the length of the sharp edged absorber can reach 3000mm, which is not only difficult to achieve in terms of technology, but also greatly reduces the effective available space in a microwave anechoic chamber if such a size is true.
Structural form: Incorporating absorbent materials into engineering plastics to give them both absorption properties and load-bearing capacity is a new direction in the development of absorbent materials.
Coating form: Only coating type absorbing materials can be used on the surface of aircraft. To broaden the frequency band, composite material coatings are generally used. When the thickness of the lithium cadmium ferrite coating is between 2.5mm and 5mm, it can attenuate by 8.5dB in the centimeter band; when the thickness of the spinel ferrite coating is 2.5mm, it can attenuate by 26dB at 9GHz; when the thickness of the ferrite and chloroprene rubber coating is between 1.7mm and 2.5mm, it can attenuate by about 35dB at 5GHz to 10GHz.
In addition, there are several complex shaped absorbers that are designed to further improve the performance of absorbent materials. The above is the discussion about the absorbing materials for electromagnetic shielding rooms (shielding machine rooms). Hope it's helpful to everyone!
