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 the magic weapon and "secret weapon" of electronic countermeasures in modern military . Its engineering applications are mainly in the following aspects.
1.1 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 enemy radar defenses. This is a kind of anti-radar reconnaissance A powerful means to reduce the weapon system from being attacked 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 cowl of the 0H-6 and AH-1G Cobra helicopter engines It can reduce the infrared radiation of the engine by about 90%. In the 1990 Gulf War, the first US F-117A aircraft that entered Iraq were stealth aircraft coated with absorbent materials . They effectively avoided Iraq’s radar monitoring.
It is reported that the world's first stealth warship successfully developed by the Swedish Navy has been put into use. The United States, Britain, Japan, Russia and other countries have all 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.
1.2 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 board or on the ship will also interfere with the radar or communication equipment on board... 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. If the radar or communication equipment fuselage, antenna and all surrounding interferences are coated with absorbing material, it can make them more sensitive and accurate to find the enemy target; coating the absorbing material on the surrounding walls 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 ground station, thereby improving the communication quality.
1.3 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 wave absorbing material; when used, insert the wave absorber 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, due to 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 quality of the absorbing material.
1.4 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, there is a widespread problem of electromagnetic radiation in today's household appliances, which can be effectively suppressed through the rational use of absorbing materials and components.
1.5 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 a dark room. 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 of radar or communication antennas, missiles, aircraft, spacecraft, 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 keep secrets.