Application of RFID absorbing materials

With the development of modern science and technology, the impact of electromagnetic wave radiation on the environment is increasing day by day. At airports, planes are unable to take off due to electromagnetic wave interference and are delayed; in Hospitals, mobile phones often interfere with the normal operation of various electronic diagnostic and treatment instruments. Therefore, it has become a major topic in materials science to control electromagnetic pollution and find a material that can withstand and weaken electromagnetic radiation - absorbing materials.

The so-called rfid or rf absorbing material refers to a type of material that can absorb electromagnetic wave energy projected onto its surface. In Engineering applications, in addition to requiring the absorbing material to have a high absorption rate of electromagnetic waves in a wide frequency band, it is also required to have light weight, temperature resistance, moisture resistance, corrosion resistance and other properties.

Electromagnetic radiation causes direct and indirect harm to the human body through thermal effects, non-thermal effects, and cumulative effects. Research has confirmed that ferrite absorbing materials have the best performance. They have the characteristics of high absorption frequency band, high absorption rate, and thin matching thickness. Applying this material to electronic equipment can absorb leaked electromagnetic radiation and eliminate electromagnetic interference. According to the law that electromagnetic waves propagate in the medium from low magnetic to high magnetic permeability, high magnetic permeability ferrite is used to guide electromagnetic waves. Through resonance, it absorbs a large amount of radiated energy of electromagnetic waves, and then converts the energy of electromagnetic waves into thermal energy through coupling.

In the increasingly important stealth and electromagnetic compatibility (EMC) technologies, the role and status of electromagnetic wave absorbing materials is very prominent. It has become a magic weapon and "secret weapon" for electronic countermeasures in modern military. Its applications are mainly in the following aspects.

stealth technology

By coating aircraft, missiles, tanks, ships, warehouses and other weapons and equipment and military facilities with absorbing materials, they can absorb reconnaissance waves and attenuate reflected signals, thereby breaking through the enemy radar defense zone. This is a type of anti-radar reconnaissance. A powerful means to reduce the attack of weapon systems by infrared guided missiles and laser weapons. For example, the effective reflection cross section of the U.S. B-1 strategic bomber is only 1/50 of that of the B-52 bomber because it is coated with absorbent materials; after the fairings of the 0H-6 and AH-1G Cobra helicopter engines are coated with absorbent materials, It can reduce the infrared radiation of the engine by about 90%. During the 1990 Gulf War, the first U.S. F-117A aircraft that entered Iraq were stealth aircraft coated with absorbent materials, which effectively avoided Iraqi radar monitoring.

Improve overall machine performance

False signals generated by the reflection of electromagnetic waves by the aircraft fuselage may lead to false interceptions or false tracking by highly sensitive airborne radars; when several radars on an aircraft or a ship work at the same time, the crosstalk between the radar transmitting and receiving antennas is sometimes very serious , the built-in jammer on board the aircraft or ship will also interfere with its own radar or communication equipment. In order to reduce such interference, foreign countries often use excellent magnetic shielding with absorbing materials to improve the performance of radar or communication equipment. If the radar or communication equipment fuselage, antenna and all surrounding interference objects are coated with absorbing materials, they can make them more sensitive and accurate in detecting enemy targets; coating the surrounding walls of the radar parabolic antenna opening with absorbing materials can make them more sensitive and accurate. It can reduce the interference of side lobes to the main lobe and increase the operating distance of the transmitting antenna. It can also reduce the interference of false target reflections on the receiving antenna. The application of absorbing materials in satellite communication systems will avoid interference between communication lines and improve Sensitivity of spaceborne communications machines and ground stations, thereby improving communication quality.

safety protection

Due to the application of high-power radar, communications equipment, microwave heating and other equipment, preventing electromagnetic radiation or leakage and protecting the health of operators is a new and complex topic. Absorbent materials can achieve this purpose. In addition, electromagnetic radiation problems are common in current household appliances, which can be effectively suppressed through the rational use of absorbing materials and components.

microwave anechoic chamber

The space composed of walls decorated with absorbers is called a microwave anechoic chamber. An equivalent non-reflective free space (noise-free zone) can be formed in the darkroom. The electromagnetic waves reflected from the surroundings are much smaller than the direct electromagnetic energy and can be ignored. Microwave anechoic chambers are mainly used to measure the characteristic impedance and coupling of radar or communication antennas, missiles, aircraft, spacecrafts, satellites, etc., to measure the pattern of backpack antennas used by astronauts, and to install, test and adjust spacecraft, etc. This is both It can eliminate external clutter interference and improve measurement accuracy and efficiency (can work indoors around the clock), and can also keep secrets.

RFID/NFC wireless charging magnetic isolation sheet

Absorbing materials are widely used in fields such as RFID/NFC and wireless charging to solve the problem of metal interference faced by RFID/NFC. They can be attached wherever the interference occurs, which is convenient, environmentally friendly and fast. It also solves the heating problem of wireless charging and improves the efficiency of wireless charging.

material type

1. Flexible and thin magnetically loaded rubber absorbing material: tuned frequency absorbing material

Tuned frequency absorbing materials, or resonant frequency absorbing materials, have extremely high reflection loss characteristics at discrete frequencies, usually with an attenuation of up to 20dB. Tuned frequency absorbing materials provide narrow-band absorption characteristics from 1 to 40GHz.

2. Cavity resonance absorbing material

Cavity resonant absorbing materials are designed to exhibit high loss characteristics when placed in a microwave cavity. Absorbing materials will effectively reduce the Q factor by attenuating cavity resonances, resonant frequencies or harmonics. At frequencies from 1 to 20 GHz, cavity resonant absorbing materials can absorb electromagnetic wave energy incident from normal directions and high angles.

3. Radio frequency absorbing foam materials

Surface wave absorbing materials

Surface wave absorbing material is a synthetic rubber absorbing material with the strongest magnetic load. Surface wave absorbing materials are designed to have the highest loss characteristics. This material is used to lay on conductive or metallic surfaces and absorb traveling or surface waves. Surface wave absorbing materials can absorb traveling wave or surface wave energy from 1 to 20 GHz.

Low frequency absorbing materials

Low-frequency absorbing materials have high attenuation characteristics in the sub-microwave frequency band. The material is made into magnetic particles of various shapes and exhibits high magnetic permeability in the frequency range from 1 MHz to 3 GHz.

4. Flexible dielectric foam absorbing material

Mesh foam absorbing material

The reticulated foam absorbing material is a very light conductive carbon-loaded sheet material that can significantly attenuate incident electromagnetic waves in the normal and deviated directions. The reticulated foam material is processed with a continuous gradient coating and has broadband reflection loss characteristics from 1 to 20 GHz.

Damaged foam absorbing material

Lossy foam absorbing materials are lightweight, low-cost carbon-loaded panels. It is machined with a uniform coating and has high insertion loss characteristics in the frequency range from 1 to 20 GHz.

5. Radio frequency absorbing materials

Curly foam absorbing material

Curly foam absorbers are lightweight carbon-loaded sheet materials whose geometry resembles an "egg tray." The tapered structure on the material enables high reflection loss from 1 to 20 GHz.

6. Spraying and pouring absorbing materials

Absorbent caulks, inks and coatings

Absorbent coating materials can be manufactured using a variety of application techniques, such as spraying, injection, or immersion coating. The material can be processed from one- or two-part materials of various viscosities.