JPS6028402B2 - metal space frame radome - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a metal space frame radome.

The radome is used to protect the cedar antenna from wind, rain, snow, etc. Its performance is evaluated by radio wave transmission, radio wave deviation, durability, etc., and its characteristics are determined by the constituent materials and structure of the radome. .

In recent years, a metal space frame radome has been newly developed with the aim of improving radome performance. In other words, the strength of the entire radome is made as small as possible by using a metal frame with a high modulus of elasticity, and a membrane material with good radio wave properties stretched between the frames serves as a radome to protect against wind and rain. . Compared to conventional FRP radomes, metal space frame radomes use metal with a high elastic modulus as a strength member, so the block area for radio waves can be reduced.

Therefore, radio wave loss and dragon wave deviation are significantly improved compared to FRP radomes.

The present invention relates to this metal space frame radome.

When considering the membrane material for metal space frame radomes, the following points must be taken into consideration: 1. Good radio wave transparency, 2. 3. Tensile strength is relatively high. It has the durability to withstand long-term use.

4. High modulus, thin, little cleave, elongation, etc.
case.

5. Easy to connect with metal frame.

Furthermore, there should be no adverse effect on the membrane structure such as stress concentration at the joint. etc. are possible. In conventional radomes, the membrane is mainly made of glass cloth impregnated with epoxy resin, polyester resin, etc. and laminated to a thickness of about 1 to 2 sides.

This FRP membrane material has good performance as a membrane material for a radome that transmits radio waves and has been used conventionally. However, in order to improve performance such as radio wave characteristics, a thinner material is required, and if a relatively rigid film material such as FRP is used, stress will be concentrated at the joint with the metal frame. This may cause cracks, etc. Therefore, to improve this point, it is effective to use a rubber-coated fabric made of rubber reinforced with fibers.

When rubber-coated cloth is used as a membrane material for a radome, the force generated on the membrane material by wind etc. can be considered to be only tensile force, so there is no worry about stress concentration due to bending.Therefore, there is no need to worry about stress concentration due to bending. Various types of rubber can be used for this rubber-coated fabric, but it is desirable to use one that has excellent radio wave transmittance, weather resistance, and good workability and repairability.

Therefore, a rubberized fabric made by coating a reinforcing fabric with EP rubber, which has excellent radio wave transparency and weather resistance, is optimal as a membrane for metal space frame radomes. The present invention relates to a metal space frame radome using EP rubber. Regarding metal space frame radomes,
Radio wave transmission loss (1-radio wave transmittance) is approximately 15-2
0% or less is required, and within this, the permeation loss of the membrane material must be approximately 4 to 5% or less. Therefore, it is thought that a coating material with a transmission loss of 2 to 2.5% or less is required. On the other hand, considering the state of use of the radome, it is necessary for the building to last 10 to 13 hours while being directly affected by weather such as rain and wind. Therefore, the rubber material used for the membrane must have an elongation at break of 100% or more during this period.

EP used in the metal space frame radome of the present invention
Rubber has a chemical structure with few side chains and low magnetism, so it has good radio wave transparency and is stable, so it has excellent weather resistance and ozone resistance. In general, EP rubbers include a random copolymer of ethylene and propylene (EPM) and a copolymer of ethylene, propylene, and a third component (EPDM), and EPDM is more advantageous from the viewpoint of processing. When using EP rubber for metal space frame radomes, it is necessary to add inorganic fillers to ensure weather resistance.

However, inorganic fillers generally reduce radio wave transmittance, and the optimum amount to be added must be determined depending on radio wave characteristics and weather resistance. Experiments have shown that carbon black is an inorganic filler that is relatively effective in improving aging resistance. The present invention is a frame radome characterized by using a film in which carbon black is mixed with EPM or EPDM and coated on a woven fabric.

The results of an experiment investigating the relationship between radio wave transmittance and weather resistance for EPDM sheets to which carbon black has been added indicate that carbon black should be added at 1 to 2 parts by weight per 100 parts by weight of the polymer.
It was found that it is possible to mix in the range of parts by weight of . Within this range, the radio wave characteristics of the radome will not be significantly impaired.
It can be used as a membrane material with excellent weather resistance.

A more suitable combination is carbon black and polymer 1.
It is blended in an amount of 2 to 5 parts by weight based on 0 parts by weight.

The most suitable formulation is one in which 2 parts by weight of carbon black is added to 10 parts by weight of polymer. The membrane material used in the metal space frame radome of the present invention can be produced by the method conventionally used for producing rubberized cloth (calendar, etc.)
can be used as is, making it relatively easy to manufacture.

It is desirable that the reinforcing cloth used for the membrane material has good radio wave transparency, high tensile strength, and little elongation. For example, organic fibers (polyester, polyamide, etc.) with good radio wave transparency or inorganic fibers (glass fiber, etc.) with low elongation and high strength may be used. However, organic fibers generally have a tensile modulus of 50 to 15 f/d, and many have relatively high elongation. In addition, inorganic fibers are generally brittle and tend to break easily after repeated bending.Therefore, fibers that are most suitable as membrane materials for radomes have a high modulus (
(need to be at least 25 thighs/d or more), and has radio wave transparency comparable to that of organic fibers.

In other words, the optimal fiber is one that has the characteristics of both organic and inorganic fibers. As a comparatively simple method for producing such a woven fiber fabric, an almost optimal one can be obtained by co-weaving organic fibers and inorganic fibers. However, the most suitable fibers are various aramid fibers (Keplar 29■, Kepler 49■, Du
Pont, etc.).

Aramid fibers are extremely superior in strength and modulus, twice that of glass fibers, and have good radio wave characteristics as organic fibers. Therefore, this membrane material made of woven aramid fibers is most suitable for use in domes.
Examples of the pus material according to the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are graphs for explaining the performance of the abscess material used in the metal space frame radome of the present invention.

Example 1 FIG. 1 shows the relationship between the amount of EDPM mixed with carbon black and the radio wave transmittance of a vulcanized sheet in which carbon black is mixed with EDPM (Espren 5oIA■, manufactured by Sumitomo Chemical).

Example 2 Figure 2 shows a vulcanized sheet made of EDPM (Espren 5oIA■, manufactured by Sumitomo Chemical) mixed with carbon black.
A deterioration test was conducted depending on the amount of mixture mixed, and it shows the deterioration time and elongation at break.

Deterioration was determined by an accelerated test using a weatherometer.
It is considered that 0 hours corresponds to 1 year outdoors. Example
3. Mix 2 parts by weight of carbon black with respect to the weight part of polymer 10 in EPDM (Espren 5oIA■, manufactured by Sumitomo Chemical), and add aramid fiber (Kepler 29■, Modulus 5).
A plain weave fabric of 00 g no.

When the radio wave transmission loss in the S band was measured for this sheet, it was 3.2%.

This material satisfies the performance requirements for metal space frame radomes.

[Brief explanation of the drawing]

Figures 1 and 2 are graphs showing the performance of the membrane material used in the metal space frame radome of the present invention, and Figure 1 is a graph showing the relationship between the amount of carbon black added and the radio wave transmission loss of the membrane material. FIG. 2 is a graph showing the relationship between the elongation of fracture of the lumber and the change over time. Figure 2

Claims (1)

[Scope of Claims] 1. A metal space frame radome characterized by using a membrane coated with woven fabric of ethylene propylene copolymer or a mixture of ethylene propylene diene copolymer and carbon black. 2. The metal space frame radome according to claim 1, wherein a woven fabric made of organic fibers having a modulus of 250 g/d or more is used as the woven fabric. 3. The metal space frame radome according to claim 1, characterized in that the woven fabric is a mixture of organic fibers and inorganic fibers. 4. The metal space frame radome according to claim 1, wherein a woven fabric made of aramid fiber is used as the woven fabric. 5. The metal space frame radome according to claim 1, wherein 1 to 20 parts by weight of carbon black is used based on 100 parts by weight of the polymer. 6. The metal space frame radome according to claim 1, wherein 2 to 5 parts by weight of carbon black is used based on 100 parts by weight of the polymer. 7. The metal space frame radome according to claim 1, wherein 2 parts by weight of carbon black is used per 100 parts by weight of the polymer.