Application of 1G-180GHz Microwave Absorbing Materials in Radar

Microwave absorbing materialsMicrowave absorbing material is a material that can absorb microwaves and electromagnetic energy with minimal reflection and scattering. Also known as radar absorbing material or radar stealth material.
The basic principle of absorbing microwaves is to convert microwave energy into other forms of motion energy through a certain physical mechanism, and convert it into thermal energy through the dissipation effect of this motion. All forms of lossy motion excited by microwaves can serve as absorption mechanisms. The common mechanisms include electrical induction, magnetic induction, electromagnetic induction, and electromagnetic scattering, which can be classified into coating type, patch type, and structural type microwave absorbing materials according to their applications; According to the working principle, microwave absorbing materials can be divided into interference type and absorption type.

1Coating type microwave absorbing material

It is made by adding absorbent in a certain proportion to polymer solutions or lotion such as resin type and rubber type through a specific process. The coatings that have been widely used currently are usually coating type absorbing materials with various ferrites, iron and its alloy micro powders as the main absorbents. Japan and the United States have developed a series of ferrite microwave absorbing materials, such as lithium cadmium ferrite, lithium zinc ferrite, nickel cadmium ferrite, and ceramic ferrite. Coating type microwave absorbing materials are easy to apply, cost-effective, and suitable for complex shaped objects; Its disadvantage is that issues such as weight, thickness, and adhesion often affect the aerodynamic characteristics of the equipment.

2Surface mount as wave absorbing material

SMT is not suitable for very complex shapes. But it can achieve complex structural design, using patches such as rubber sheets, ceramic sheets, and plastic sheets.

3Structural microwave absorbing materials

Made by adding absorbent to non-metallic composite materials as carriers. Usually, epoxy resin and thermoplastic materials are used as the matrix, filled with absorbents such as ferrite, graphite, carbon black, etc., such as carbon fiber/epoxy resin, graphite/thermoplastic material, boron fiber/epoxy resin, graphite fiber/epoxy resin, etc. This type of material can not only reduce the scattering of electromagnetic waves, but also withstand certain loads. It is lighter in weight than general metal materials, has certain strength and stiffness, and has been applied.

4Interference type wave absorbing material

Interference type microwave absorbing materials mainly interfere with electromagnetic waves, and the incident electromagnetic waves and reflected electromagnetic waves have opposite phases (phase difference of 180 °) at the center frequency point and cancel each other out. The characteristic of this type of material is a narrow frequency range, which can be used in high frequency situations, and the material can be made thinner.

Absorption type wave absorbing material

By utilizing the high dielectric and magnetic losses of incident electromagnetic waves in objects, electromagnetic energy can be converted into thermal energy or other forms of energy. Absorption type microwave absorbing materials are divided into two categories: electrical loss type and magnetic loss type. Usually, electrical loss materials have a better absorption effect on high frequencies; Magnetic loss materials are more effective in absorbing low frequencies. If the two are combined, a wide frequency range absorbing material can be made.
Electric loss type microwave absorbing material is a gradually changing dielectric performance absorbing material based on carbon powder or metal particles, prepared by varying the thickness, depth, and type of filler. Magnetic loss type microwave absorbing materials are thin layer materials filled with magnetic materials such as ferrite or carbonyl iron powder polymers, such as epoxy polysulfide, silicone rubber, urethane, and fluoroelastomer.
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