A radome is a weatherproof, structural enclosure that confines a radar system or antenna and which minimally attenuates the electromagnetic signal transmitted or received by the antenna.
Radomes protect antenna surfaces from the elements and hide antenna electronic equipment from view. Weather radomes, air traffic control radomes, satellite communications radomes, and telemetry radomes are all examples of specialized radome producers that make radomes for a variety of applications.
When was the Radome Invented?
The first air-supported radome was built in 1946 by Walter Bird. These air-supported domes were completely spherical and resembled, as well as functioned, like a huge balloon over top of the radar system. This first radome was made possible by innovations in fabric technologies, which incorporated a neoprene-coated fibreglass cloth.
Newer materials with improved architectural characteristics opened up new possibilities for air-supported construction. Radomes were a useful tool, opening the door to what was previously thought to be impossible with fabric and air.
What Is the Purpose of a Radome When Fitted to an Antenna?
A radome is frequently used to keep ice and snow from accumulating on antennas. The radome protects the spinning radar parabolic antenna from debris and rotational variances caused by wind, as well.
Stationary Antennas
For stationary antennas, a lot of ice can de-tune the antenna to the point where its impedance at the input frequency increases dramatically, resulting in an increase in voltage standing wave ratio (VSWR). This reflected power is returned to the transmitter, where it may cause overheating.
A foldback circuit can help prevent this; however, it has the disadvantage of significantly decreasing the station’s output power, lowering its range. A radome prevents this by enclosing exposed elements of the antenna in a weatherproof, durable material such as fiberglass, keeping debris and ice away from the antenna to avoid any serious problems.
The need for radomes in World War II was one of the main driving forces behind the use of fiberglass as a structural material. When calculating wind loads, the usage of a radome greatly lowers both normal and iced wind loads. For protection from falling ice or debris, many tower sites demand or prefer the use of radomes.
In the case of an electric antenna heater, versus a radome on the ground, they may be used instead. The heaters are generally fed with direct current and do not cause any physical or electrical effects on the alternating current of radio transmission signals.
Radar Dishes
A single, big, spherical dome covering the rotational mechanism and delicate electronics is used in radar dishes to protect them from icing.
The Menwith Hill electronic surveillance station, which contains over 30 radomes, is said to intercept satellite communications on a regular basis. The radome enclosures at Menwith Hill conceal the antennas’ orientation from spectators, shielding them from knowing which satellites are being targeted. Similarly, radomes hide the antennas that operate in ECHELON installations.
During the Cold War, the United States Air Force Aerospace Defense Command oversaw and maintained dozens of air-defense radar stations throughout the United States and Alaska. The majority of the ground radars at these sites were protected by rigid or inflatable radomes.
The radomes were generally at least 15 m (50ft) in diameter and were joined to tower structures that also housed the radar transmitter, receiver, and antenna. Some of these radomes were quite big. The CW-620 was a space frame rigid radome with a maximum diameter of 46 m (150 ft) and a height of 26 m (84 ft).
The radome was made up of 590 panels and was designed to withstand winds up to 240 km/h (150 mph). The total weight of the radome, including the surface area, was 92,700 kg (204,400 lb.).
Maritime Satellites
Radomes are frequently utilized in the maritime satellite communication sector to safeguard dish antennas that are tracking constant satellites while the boat experiences pitch, roll, and yaw motions.
The radomes on large cruise ships and oil tankers may be up to 3 m in diameter and cover antennas for high-speed data, television, voice, and the Internet transmissions. Similar services from smaller installations such as the 85 cm motorized dish employed in the SES Broadband for Maritime system are possible nowadays. Radomes may be used on small boats as tiny as 26 cm in diameter for voice and low-speed data.
Planes
A composite radome is a three-layer structure comprised of a layer of stiff fiberglass, a layer of honeycomb, and another layer of fiberglass. Add some epoxy and paint for good measure. The interior layer of honeycomb is extremely strong, light, and provides little obstructive to the radar waves that the radar dish wants to detect.
The static build-up on the surface is collected by lightning diverter strips and carried to the airframe without causing sparks or electric shocks.
Types of Ground Radomes
Composite Radomes
A sandwich radome, for example, is a composite radome. A spherical dome is formed by doubly-curved panels that make up a rigid, self-supporting shell structure with two shells.
Air Supported Radomes
An air-supported radome is a flexible fabric envelope that must be inflated at all times. The operation of this device relies on non-interruptible power and blower redundancy systems. This envelope cloth has the greatest RF performance.
Space Frame Radomes
The space frame radome is a rigid, self-supporting structure formed of triangular panels that are joined into a geodesic dome. This kind of radome is most often utilized in severe weather conditions.
What Are Radomes Made Out of?
The type of material used is crucial. However, not every material is equally suited for the design of a radome. The properties of the surface at the point of contact alter radar waves’ propagation and reflection when they strike an object or person. Some materials are simple to penetrate, while others reflect or absorb them too much.
The goal of a radome is to protect the antenna while yet allowing as little loss in signal strength as possible. Metal is highly reflective, making it unsuitable for use in a radome. Even wooden radomes would present a problem, as they only offer a limited ability to allow radar pulses to pass through.
Polystyrene foams, on the other hand, are excellent for concealing the front end. They may even be placed on top of the antenna. However, because to their poor stability and sensitivity to chemicals, they may have a detrimental impact on the housing’s protective function.
Plastics are penetrated by radar waves. Radomes constructed of this material are the preferable option. However, because plastics vary considerably, several factors must be considered. They may also be improved or restricted based on their characteristics.
Other chemicals, such as carbon in the case of black plastics, can also cause measurement errors. Penetration may be decreased by coatings that are frequently applied to plastics. Accumulated water due to rough or uneven surfaces might hinder detection.
What Is the Best Material for a Radome?
In all radome applications, polyurethane foams provide a cost-effective alternative to more expensive materials that are both flexible and durable. With simple changeover, the material is readily optimized for high performance with minimal dielectric interference.
Material Thickness Is Important
Because the radar waves must enter and exit within half of a wavelength to minimize any disruption to their propagation, they must do so within half of the wavelength’s length. This implies you’ll need to choose a material thickness that is appropriate for half of the wavelength.
However, when you consider the material substance – or more precisely how the radar wave is changed by the type of material as it enters/penetrates the radome – you must also think about the material substance.
The adaptation is based on the researchable dielectric function (ε or primitivity) of the material chosen. The wavelength is shortened by penetration, an adjustment is required by the factor.
The dielectric constant of a plastic is determined by its chemical makeup, and the result will be between three and four. However, because each type of plastic has numerous variants, this number may vary significantly in practice.
Color Variations of Radomes
White radomes are used in a variety of situations, and they are the most logical choice. A white substance reflects sunlight(radiation), which may cause electronic noise in the antenna if it is not filtered.
The use of white radomes for aircraft is due to the fact that satisfactory white coatings have now been discovered, and they are used since they offer superior radiation protection than gray radomes. All benefits of conductive white radomes can be obtained, but their manufacture is more complex. They are most likely only useful for the most sensitive radar systems.
Black radomes, only used in high-speed vehicles. They’re colored thanks to antistatic carbon powder that’s used to counteract electrostatic charges produced by air friction. The use of gray radomes rather than black ones is intended to conceal radars by lowering the sky/radome contrast.
Conclusion
The power of radar has grown considerably in recent decades, and it may now be used in a variety of settings due to technological developments. Radomes (radar-domes) are used to keep radar antennae free of interference and aid in the smooth functioning of radars. They were designed to guarantee that the antennae are free from interference, whether environmental or wireless.
The importance of the radome cannot be overstated. It is critical that the antennae in areas like military defense are flawless. For example, missiles are controlled via wireless communication and any disruption to the missile’s flight path might be catastrophic.