What is a standard absorbing material? Moshi Electronics pointed out that standard absorbing materials are wedge absorbing materials, pyramid absorbing materials, and mastoid absorbing materials. Here is an introduction to the shape of the absorbing material.
Wedge shape: The absorber used in the microwave anechoic chamber is often made into a wedge shape (golden tower shape), which is mainly composed of non-woven fabrics, non-flammable, polyurethane foam, and silicate plate metal film assembly types. As the frequency decreases, the length of the absorber is also greatly increased. The ordinary wedge-shaped absorber has an approximate relationship of L/λ≈1, so at 100MHz, the wedge length reaches 3000mm, which is not only difficult to achieve in technology, but also effective in microwave anechoic chambers. The available space is also greatly reduced.
Single-layer flat-plate shape: The first absorber developed abroad is a single-layer flat-plate shape, and the absorbers made later are directly attached to the metal shielding layer. It is thin and light, but the working frequency range is narrow.
Double-layer or multi-layer flat plate shape: This kind of absorber can work in a wide working frequency range and can be made into any shape.
Coating shape: Only coating-type absorbing materials can be used on the surface of the aircraft, which broaden the frequency band. Generally, composite coatings are used. For example, when the thickness of the spinel ferrite coating is 2.5mm, it can attenuate 24dB at 9GHz; when the thickness of the lithium cadmium ferrite coating is 2.5mm～5mm, it can attenuate 8.5dB in the centimeter band; the ferrite is chlorinated When the thickness of the butadiene rubber coating is 1.7mm～2.5mm, the attenuation is about 30dB at 5GHz～10GHz.
Structural shape: Mixing absorbent materials into engineering plastics makes them both absorbent and load-bearing. This is a direction for the development of absorbent materials.
Nowadays, in order to further improve the performance of absorbent materials, several complex types of absorbent bodies with a combination of shapes have been developed abroad.