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The structure of antenna radome and the 5 main types
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We have already introduced the advantages of antenna radomes before, in this article we will start with the structure of radomes and discuss their main structural forms, as well as the material composition and specific use of radomes under different structures.
I, the structure design of the antenna radome
The difference between the structure of the radome and other building structures is that the design of the structure type, component size, cover wall thickness, material selection and structural details must be considered electrical characteristics.
1. Canopy wall thickness: related to the working wavelength. Electrically, in order to minimise reflections, a uniform single wall thickness or core thickness of the sandwich structure must be designed according to the working wavelength. However, the chosen wall thickness must be able to withstand the expected maximum aerodynamic load and other loads without being damaged or without producing large deformations. The specific choice of wall thickness should be based on the working wavelength, radome size and shape, environmental conditions, materials used in electrical and structural performance of each other.
2, material selection: the radome wall media materials to be considered factors are: in the working frequency of the dielectric constant and loss angle tangent to low, to have sufficient mechanical strength. Generally speaking, the inflatable radome commonly used coated with sea Palon rubber or neoprene polyester fiber film; rigid radome with glass fiber reinforced plastic; sandwich structure in the sandwich more with honeycomb core or foam. Aviation radome generally with glass fiber reinforced plastic, ceramic, glass - ceramic and laminate.
3, specific structure: the uneven part of the radome will cause high frequency energy bypass and reflection, therefore, in the radome wall where the high frequency energy through the part generally should not set reinforcement, because it may make the shell radome produce local or overall instability, or produce large deformation, thus bringing many restrictions to the structural design and cover size. In order to facilitate the manufacture, installation and transportation, must be made into a large rigid radome block type, spherical connection shall be set flange, resulting in the cover wall is not uniform.
Therefore, in the design generally through the electrical performance test and structural performance test, to find a good overall performance of the connection scheme. In addition, the metal components or metal connections used should be such that their electrical shading is minimised.
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Second, the introduction of 5 kinds of common antenna cover
1、Aerial antenna radome
Generally for shell structure. According to the specific situation, can use vertical incidence radome or streamlined large incidence angle radome. To meet the aerodynamic requirements, the radome should be made into a streamlined structure. However, when the antenna is scanned inside the radome, the incidence angle varies greatly, making it difficult to get the best electrical performance from the radome.
If not streamlined, usually designed into the incidence angle of less than 30 ° angle of the radome, its shape can be cylindrical, spherical or paraboloidal shape. The aerodynamic performance of this vertical incidence radome is poor, but the electrical performance is better.
2, ground radome
Usually is truncated spherical (about three-quarters of the ball), can be divided into two types of inflatable and rigid cover. Rigid radome is also divided into shell structure radome and space skeleton radome two kinds.
3, inflatable radome
Spherical film in the cut-off four around with pressure plate fixed in the airtight platform, around or with rope pulling tight, or with other methods of fixed, internal inflatable.
Its advantage is the cover wall thin and uniform, good electrical performance, suitable for broadband work; cover body soft and easy to fold, light weight, small size, transportation, storage, easy to install. The disadvantage is that the hood needs to be continuously inflated to maintain the shape and necessary rigidity of the hood. If the inflatable equipment fails, it will make the hood collapse and damage the antenna.
4, shell structure antenna radome
Usually the hood wall made of curved shell, structure load by shell support. Which uniform single-wall shell structure because from the work wavelength and size considerations, hood size is restricted; foam shell structure because of the material dielectric constant and loss angle tangent low, electrical allow the use of thicker hood wall to meet the structural load requirements.
The connection between the foam blocks can be glued together to form a uniform overall shell with good electrical performance, suitable for high frequency and wide frequency band work; sandwich shell structure is commonly used as A-type sandwich structure. It consists of two equal-thickness symmetrical high-strength density skins and a low-density core. Its advantage is the strength-to-weight ratio and stiffness-to-weight ratio is large, suitable for certain wavelengths of large ground radome. But the disadvantage is narrow working band, manufacturing complex, high cost.
5, space skeleton antenna radome
By the metal (or medium) spherical grid skeleton and mask on its medium sheet (or film) composition. Mainly by the grid skeleton bear structural load, the grid skeleton design principle is to make the rod cross-section in the case of mechanical properties to ensure that the electrical shading as small as possible. The strength and stiffness of metal is greater than that of dielectric materials, so the metal skeleton is mostly used.
Its advantage is suitable for high frequency and wide band work, easy to manufacture, cheaper, suitable for large ground antenna.
