What conditions need to be met by glass fiber as a wave-transmitting material for radome?

The wave-transmitting material for radome refers to a multifunctional dielectric material that protects the antenna system to work normally in the external environment. Its main performance requirement is to reduce the influence of the radome medium on the electromagnetic wave signal received and reflected by the antenna system. Because antenna systems working in different environments have different requirements for the performance of wave-transmitting materials, the types and structures of radome materials are also different. As the use environment of radar antennas becomes more severe, the requirements for material performance become more stringent.

For wave-transmitting materials for radomes, it is necessary to meet a series of indicators such as electrical properties, mechanical properties, and environmental resistance. Electrical properties are generally expressed by dielectric constant ε and loss tangent tanδ. Usually in the microwave range of 0.3 to 300 GHz, the wave-transmitting material should satisfy e less than 10 F/m and tanδ less than 0.01, while the excellent wave-transmitting material ε is only It is 1~4 F/m, tanδ is 0.001~0.01, and does not change significantly with temperature and frequency changes (such as temperature rise or drop by 100°C, the change is less than 1%).

On the premise of satisfying the electrical performance, good strength and modulus can make the radome less susceptible to damage when subjected to mechanical stress in the vertical and horizontal directions, thereby ensuring the working stability and mechanical reliability of the antenna system. The use environment of radar antennas is changeable, and temperature differences may affect the performance of the antenna. Therefore, good thermal shock resistance, ablation resistance, and low thermal expansion coefficient are also necessary conditions for wave-transmitting materials for radomes.

At present, some companies use glass fiber composite materials to prepare wave-transmitting materials for radomes. The glass fiber has light weight and good hoop strength; good electrical insulation, strong wave transmission (wave transmission rate up to 98%), no induction eddy current; corrosion resistance, UV resistance, aging resistance, impact resistance, at -45~ It still performs well in the harsh environment of 110℃, and can be applied to various complicated environments; it can be used to make communication covers for base station antennas, military communications, ships, high-speed rail antennas and large conference venues.

In the early 1950s, Boeing Aircraft Company used glass fiber winding to prepare the “Pomack” missile CIM-10 radome, which was successfully applied to an active homing guided missile with a Mach number equal to 3. There are many types of glass fiber. S-type glass fiber contains more alkali metal oxides. Missiles are easy to be found and tracked during operation, and they are less used in the field of radome. The D-type glass fiber has the smallest dielectric constant and loss tangent value, and is especially suitable for ultra-high precision guided missile radomes that require high electrical performance.

Both the “Hock” missile and the “SA-6″ missile of the former Soviet Union used D-type glass fiber reinforcement. Quartz fiberglass is light in weight and excellent in dielectric properties. It is mostly used in broadband and high frequency (10-20GHz) radomes. In the 1960s, General Electric Company of the United States successfully prepared a low-cost quartz fabric reinforced aluminum phosphate-based composite material, which can still be used normally at 650°C.

Radome is a necessary protective item for radar antennas. The glass fiber transmissive radome developed and produced must have the excellent characteristics of light weight and easy processing. It must be able to maintain geometric dimensions during use, without deformation, and in harsh conditions. In the natural environment, it can withstand ultraviolet radiation, intense heat and cold changes, and has good anti-aging and impact resistance, without special maintenance.

Post time: Sep-19-2020
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