In the increasingly important stealth and electromagnetic compatibility (EMC) technology, the role and status of electromagnetic wave absorbing materials are very prominent, and they have become a magic weapon and "secret weapon" for electronic countermeasures in modern military. Its engineering applications are mainly in the following aspect.
1. Stealth technology
Coating absorbing materials on various weapons and military facilities such as aircraft, missiles, tanks, ships, warehouses, etc. can absorb reconnaissance radio waves and attenuate reflected signals, thereby breaking through the enemy’s radar defense zone. This is part of anti-radar reconnaissance. This is a powerful method to reduce the attack on the weapon system by infrared guided missiles and laser weapons. For example, because the American B-1 strategic bomber is coated with absorbing material, its effective reflection cross section is only 1/50 of that of the B-52 bomber; after coating the absorbing material on the fairing of the 0H-6 and AH-1G Cobra helicopter engines The infrared radiation of the engine can be reduced by about 90%. In the 1990 Gulf War, the F-117A aircraft that the United States entered Iraqi territory were stealth aircraft coated with absorbent materials. They effectively avoided Iraq’s radar monitoring. It is reported that the stealth warship successfully developed by the Swedish Navy has now been put into use, and the United States, Britain, Japan, Russia and other countries have developed their own stealth tanks and other stealth combat vehicles. In addition, electromagnetic wave absorbing materials can also be used to conceal landing lights and other airport navigation equipment and other ground equipment, ship masts, decks, submarine periscope brackets and air ducts and other equipment.
2. Improve the electromagnetic compatibility of the whole machine
The false signals generated by the reflection of electromagnetic waves by the aircraft fuselage may lead to false interception or false tracking of highly sensitive airborne radars; when several radars on an aircraft or a ship are working at the same time, the crosstalk between the radar transmitting and receiving antennas is sometimes very serious , The jammer on the plane or on the ship will also interfere with the radar or communication equipment that comes with it....... In order to reduce such interference, the excellent magnetic shielding of absorbing materials is commonly used abroad to improve the performance of radar or communication equipment. For example, coating the absorbing material on the fuselage, antenna and all surrounding interferences of radar or communication equipment can make them more sensitive and accurate to find the enemy target; coating the absorbing material on the surrounding wall of the opening of the radar parabolic antenna, It can reduce the side lobe's interference to the main lobe and increase the distance of the transmitting antenna, and it can reduce the interference of false target reflection on the receiving antenna; the application of absorbing materials in the satellite communication system will avoid the interference between communication lines and improve The sensitivity of the spaceborne communicator and the ground station, thereby improving the communication quality.
3. RFID antenna anti-metal isolation application
This application mainly uses the high track rate characteristics of a type of high magnetic track rate, low loss type absorbing material; when used, insert the wave absorbing plate between the 13.56MHz loop antenna and the metal substrate to increase the induced magnetic field through the wave absorbing material In itself, it reduces the chance of passing through the metal plate, "thereby reducing the induced eddy current in the metal plate, thereby reducing the loss of the induced magnetic field." At the same time, because of the insertion of the absorber, the measured parasitic capacitance will also be reduced, and the frequency offset will be reduced. It is consistent with the resonant frequency of the card reader, thereby improving the reading distance. Of course, the degree of improvement depends on the excellent degree of the characteristics of the absorbing material.
4. Security protection
Due to the application of high-power radars, communication devices, microwave heating and other equipment, preventing electromagnetic radiation or leakage and protecting the health of operators is a new and complex topic. Absorbing materials can achieve this goal. In addition, today's household appliances generally have electromagnetic radiation problems, which can be effectively suppressed through the rational use of absorbing materials and their components.
5. Microwave darkroom
The space formed by the wall surface decorated by the absorber is called a microwave anechoic chamber. An equivalent non-reflective free space (no noise zone) can be formed in the dark room, and 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 for the measurement of characteristic impedance and coupling degree of radar or communication antennas, missiles, airplanes, spacecrafts, satellites, etc., the measurement of astronauts' shoulder antenna pattern, and the installation, testing and adjustment of spacecraft, etc. It can eliminate external clutter interference and improve measurement accuracy and efficiency (indoors can work around the clock), and it can also keep secrets.