Radar absorbing material design technology is a necessary technical means to obtain high-performance absorbing materials. It mainly includes the calculation of electromagnetic wave transmission characteristics in the medium, the estimation of the equivalent electromagnetic parameters of mixed media, and the optimization design. It has reached the level of engineering application. Radar absorbing materials can absorb electromagnetic waves well, and should have two basic conditions: (1) When electromagnetic waves propagate and are incident on the surface rolling layer of the material, they can maximize the penetration of electromagnetic waves into the material. In order to reduce the direct reflection of electromagnetic waves, it is required to fully consider its electrical matching characteristics when designing materials; ② Once electromagnetic waves enter the material and propagate inside, it can be quickly and almost completely attenuated. This requires Consider its attenuation characteristics when preparing materials. In terms of the absorbing principle of absorbing materials, it can be divided into two types: absorption type and resonance type. Regardless of the type, the attenuation characteristics of electromagnetic waves propagating in the material are the key to the wave absorption of composite materials.
For thin-layer absorbing materials, the absorbing mechanism of radar waves is mostly the interference of waves. For absorbing composite materials with multilayer structure, the absorbing mechanism is mainly to convert the energy of electromagnetic waves into heat and be absorbed. The absorption of electromagnetic waves is related to the dielectric properties, and the dielectric properties are related to the polarization of the medium. Under the action of electromagnetic waves, absorbing materials will also produce electronic polarization, ion polarization, steering polarization and interface polarization. Each polarization needs to consume a certain amount of energy. For absorbing materials, the interface condition is very important. It has two meanings: one is that there are many interfaces; the other is that every interface can be designed. When electromagnetic waves enter the absorbing material, there will be three main situations for every interface that electromagnetic waves propagate. That is, part of the energy is absorbed by the interface, part of the energy passes through the interface and propagates to the next interface, and part of the energy is reflected back. When the reflected part encounters the previous interface, the above three situations will also occur, but the energy at this time becomes smaller. By analogy, the process of electromagnetic waves propagating in the absorbing material is actually the back and forth propagation of multiple waves with different amplitudes. The final result is that the energy of the electromagnetic waves injected into the absorbing material is attenuated to achieve the purpose of wave absorption. These do not include the loss of electromagnetic waves due to refraction and scattering.