JPS583406B2 - Metal space frame radome - Google Patents

Description

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

A radome is used to protect a radar 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 characteristics stretched between the frames serves as a radome to prevent wind and rain. be.

Compared to conventional FRP radomes, metal space frame radomes use metal with a high modulus of elasticity as a strength member, so the block area for radio waves can be reduced.

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

The present invention relates to this metal space frame radome.

When considering it as a membrane material for metal space frame radomes, the following points must be taken into consideration: 1. Good radio wave transparency.

2. Relatively high tensile strength.

3. It has weather resistance that can withstand long-term use. 4. High modulus, low creep and elongation even when thin.

5. Easy to connect with metal frame. Furthermore, there should be no adverse effects on the membrane materials such as stress concentration at the joints.

etc. are possible. In conventional radomes, glass cloth is mainly impregnated with epoxy resin, polyester resin, etc.
The membrane material is a laminated plate with a thickness of about 2 mm.

This FRP membrane material has relatively good performance as a membrane material for radomes, such as transmitting radio waves, and has been used conventionally.

However, in order to improve performance such as radio wave characteristics, a thinner membrane material is required, and if a relatively rigid membrane 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 or the like can be considered to be only tensile force, so there is no worry about stress concentration due to bending.

Therefore, it is possible to connect the metal frame relatively easily.

Various types of rubber can be used for this rubberized fabric, but it is desirable to use one that is excellent in radio wave transparency, weather resistance, workability, and repairability.

Therefore, a rubber-coated reinforcing fabric coated with EP rubber, which has excellent radio wave transparency and weather resistance, is optimal as a membrane material for metal space frame radomes.

The present invention relates to a metal space frame radome using EP rubber.

For metal space frame radomes, the radio wave transmission loss (1-radio wave transmittance) must be approximately 15 to 20% or less, of which the transmission loss of the membrane material is approximately 4 to 5%.
Must be less than or equal to

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 usage state of the radome, it is necessary for the building to last 10 to 15 years 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 polarity, so it has good radio wave transparency and is stable, so it has excellent weather resistance and ozone resistance.

In general, EP rubber includes 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, in general, inorganic fillers 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 titanium white is an inorganic filler that is relatively effective in improving weather resistance.

The present invention is a metal space frame radome characterized by using a film in which titanium white is mixed with EPM or EPDM and coated on a woven fabric.

The experimental results of investigating the radio wave transmittance and weather resistance of EPDM sheets containing titanium white indicate that titanium white can be mixed in the range of 5 to 100 parts by weight per 100 parts by weight of the polymer. I understand.

Within this range, the radio wave characteristics of the radome will not be significantly impaired and it can be used as a membrane material with excellent weather resistance.

A more suitable blend is one in which 20 to 50 parts by weight of titanium white is blended per 100 parts by weight of the polymer.

The most suitable formulation is one containing 2 parts by weight of titanium white per 100 parts by weight of polymer.

The membrane material according to the present invention can be produced relatively easily because the method (calendering, etc.) conventionally used for producing rubberized cloth can be used as is.

It is desirable that the reinforcing cloth used for the membrane material has good radio wave transparency, high tensile strength, and low elongation.

For example, it is possible to use organic fibers with good radio wave transparency (polyester polyamide, etc.) or inorganic fibers with low elongation and high strength (glass fibers, etc.).

However, in general, the tensile modulus of organic fibers is 50 to 1.
50 g/d, and many have relatively large elongation.

In addition, inorganic fibers are generally brittle and are often easily broken by repeated bending.

Therefore, the fiber most suitable as a membrane material for a radome has a high modulus (at least 250 g/d or more is required) and has a radio wave transmittance comparable to that of organic fiber.

In other words, the optimal fiber is one that has the characteristics of both organic and inorganic fibers.

As a relatively simple method for producing such a woven fiber fabric, an almost optimal one can be obtained by blending organic fibers and inorganic fibers.

However, the most suitable fibers are various aramid fibers (Kepler 29■,
Kepler 49 DuPont, etc.).

Aramid fibers have excellent strength and modulus, some of which are twice that of glass fibers, and have good radio wave characteristics as organic fibers.

Therefore, this membrane material made of aramid fiber woven fabric is most suitable for use in radomes.

Examples of the membrane material according to the present invention will be described with reference to the drawings.

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

Example 1 Figure 1 shows EDPM (manufactured by Sumitomo Chemical, Esplen 501A Town)
This figure shows the relationship between the mixing amount and radio wave transmittance for a vulcanized sheet containing titanium white mixed with titanium white.

Example 2 FIG. 2 shows a deterioration test performed on a vulcanized sheet made by mixing EDPM (Esplen 501A, manufactured by Sumitomo Chemical) with titanium white depending on the amount of the mixture, and shows the deterioration time and elongation at break.

Deterioration is generally measured at 20% by accelerated testing using a weatherometer.
It is considered that 0 hours corresponds to 1 year outdoors.

Example 3 2 parts by weight of titanium white per 100 parts by weight of polymer was mixed with EPDM (Espren 501A, manufactured by Sumitomo Chemical), and aramid fiber (Kevlar 29, modulus 500) was mixed.
A plain weave fabric (G/D DuPont) was calender-coated on both sides to form a sheet with a thickness of about 1.2 mm.

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

This membrane material fully satisfies the performance for metal space frame radomes.

[Brief explanation of drawings]

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 titanium white added and the radio wave transmission loss of the membrane material. FIG. 2 is a graph showing the relationship between the rupture of the membrane material and the change over time.

Claims (1)

[Scope of Claims] 1. A metal space frame radome characterized by using a film in which a woven fabric is coated with ethylene propylene copolymer or a mixture of ethylene propylene diene copolymer and titanium white. 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 Metal space frame radome according to claim 1, characterized in that a woven fabric made of aramid fiber is used as the woven fabric 5 - 5 to 100 parts by weight of the polymer as titanium white
Claim 1 characterized in that 100 parts by weight is used.
Metal space frame radome. 6 20 per 100 parts by weight of polymer as titanium white
Claim 1 characterized in that ~50 parts by weight is used.
Metal space frame radome. 7 30% for 100 parts by weight of polymer as titanium white
The metal space frame radome according to claim 1, characterized in that the metal space frame radome uses a weight part.