Radome Basics

The basic function of a radome is to form a protective cover between an antenna and the environment with minimal impact to the electrical performance of the antenna. Under ideal conditions a radome is electrically invisible. How well a radome accomplishes this depends on matching its configuration and materials composition to a particular application and RF frequency range. Radomes can be found protecting a wide range of outdoor terrestrial and shipboard communications systems and radar installations as well as airborne avionics system antennas. The proper selection of a radome for a given antenna can actually help improve overall system performance, by:

• Maintaining alignment by eliminating wind loading;
• Allowing for all weather operation by protecting the system from rain, snow, hail, sand, salt spray, insects, animals, UV damage, and wide temperature fluctuations;
• Providing shelter for installation and maintenance personnel;
• Preventing visual observation of system (security); and
• Minimizing downtime, and extending component and system operating life.

Historically, a variety of materials have been used for constructing radomes, including balsa and plywood in early structures. Modern ground based and ship based radomes are manufactured using composite materials such as fiberglass, quartz, and aramid fibers held together with polyester, epoxy, and other resins [1] such as the one shown in Figure 1. Foam and honeycomb cores are often added between inner and outer "skins" of the radome to function as a low dielectric constant spacer material providing structural strength and rigidity.

It is important that the dielectric constant of the material is low. A low dielectric constant material reduces reflections. Reduced reflections minimize impact to the radiation pattern and insertion loss. Some materials such as UHMWPE and many plastics have a dielectric constant close to 2. However, requirements such as high strength, high operating temperature, or low cost preclude them in many cases.