Magnetic Metamaterial - A New Radar Absorbing Material

        Electromagnetic metamaterialElectromagnetic metamaterial is a new type of artificial composite electromagnetic material whose dielectric constant and magnetic permeability can be artificially controlled, and various parameters can be positive or negative. Electromagnetic metamaterials possess many unique properties that are completely different from typical electromagnetic materials. Firstly, when electromagnetic waves propagate in it, the electric and magnetic fields, as well as the direction of the electromagnetic wave vector, follow the left-hand rule, which is completely different from the right-hand rule in typical electromagnetic media.

As a result, the direction of electromagnetic wave energy flow is parallel to the direction of electromagnetic wave propagation, and the group velocity direction of electromagnetic waves is opposite to the phase velocity direction, thus possessing the characteristics of reverse waves and producing the reverse Doppler effect. Secondly, electromagnetic metamaterials can have a negative refractive index, forming negative refractive properties, which is a peculiar phenomenon completely opposite to the well-known refraction. In 2001, the negative refraction phenomenon in the microwave frequency band was first experimentally verified and was selected as one of the top ten scientific achievements in the world in 2003 by the American magazine Science. This can form a special lens that can break through the diffraction limit of traditional lenses, image the near-field of electromagnetic waves, and obtain super-resolution far below the wavelength.

Electromagnetic metamaterials can be applied due to their unique electromagnetic propertiesElectromagnetic wave absorbing materialsTo achieve invisibility of metal targets. For example, by utilizing the negative electromagnetic parameters of the material to construct a high impedance surface, a thin plate electromagnetic wave absorbing structure can be achieved; For example, by utilizing the electromagnetic resonance structure in the material, controllable design of its electromagnetic parameters can achieve absorption for specific frequency bands, with a material thickness of only one twentieth of the wavelength, and so on. Especially by utilizing the strong resonance loss property of electromagnetic metamaterials, by designing the electromagnetic parameters of metamaterials reasonably, their wave impedance can be matched with air, and the resonance loss of electromagnetic specific materials can be used to achieve complete absorption. The absorbing structure designed and prepared based on this can theoretically achieve 100% absorption, and the microwave absorption rate has reached 88% in experiments.

Due to the ideal absorption characteristics of electromagnetic metamaterials only in a narrow frequency band, the absorbing structure composed of metamaterials is a narrowband absorbing structure. This narrowband absorbing structure can be used to solve the low-frequency problem of absorbing materials, shield or absorb signals in specific communication or radar detection frequency bands, and is suitable for applications such as stealth for specific frequency radars, specific radar cover structures, electromagnetic interference resistance, and information security. By designing the electromagnetic parameters of electromagnetic metamaterials reasonably, the incident electromagnetic waves can be completely diffracted and propagated in the artificial electromagnetic metamaterial covering the target, thereby achieving complete invisibility of the target.

The new concept of electromagnetic wave bending diffraction propagation has been fully validated experimentally, achieving stealth of metal targets in the microwave frequency range. The new concept of electromagnetic wave stealth theory and experimental verification based on new artificial electromagnetic materials has once again been rated as one of the top ten technological breakthroughs in 2006 by the American journal Science. This new concept and application of stealth technologyAbsorbing materialThe concept of achieving stealth is different. It does not absorb radar wave energy through materials, but designs specific artificial electromagnetic materials to make radar waves bypass weapon targets without generating echoes.

Due to the fact that the absorption performance of electromagnetic metamaterials is mainly determined by the unit resonant structure, effective adjustment of the absorption spectrum can be conveniently achieved by artificially changing the resonant structure. For example, integrating adjustable devices such as varactor diodes into absorbing structures can produce absorbing structures with novel and adjustable functions.

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