JPH08162845A - Reflecting mirror for parabolic antenna - Google Patents

Abstract

PURPOSE: To avoid a temperature rise of a radiator or the like due to reflection of the sun ray and to allow the reflecting mirror to have provision for a parabolic antenna with a large aperture by adhering a reflex-reflection material to a radio wave reflecting face of the reflecting mirror. CONSTITUTION: Glass beads 24 are arranged on an entire surface 22 of a reflecting mirror 21 of a parabolic antenna by using a paint 23 for a medium. In this case, the paint 23 is used for a base material but an adhesive material may be used. Thus, the sun ray 25 made incident onto a reflecting mirror 22 is reflected in the incident direction independently of the incident direction by the optical property of the glass beads 24. Thus, the regular reflecting component of the sun ray 25 is suppressed by adhering a reflex-reflecting material to the surface 22 of the reflecting mirror 21 of the parabolic antenna to avoid the sun ray from being concentrated onto a focus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parabolic antenna reflector, and more particularly, to a terrestrial and space parabolic antenna in which sunlight often comes into view of the parabolic antenna.

[0002]

2. Description of the Related Art A conventional parabolic antenna comprises, as shown in FIG. 6, a reflector 61 for reflecting radio waves and a radiator 63 installed near a focal point 62 of the reflector for radiating or receiving radio waves. You.

When the sunlight 65 is incident from the same direction as the radio wave 66, the sunlight 65 and the radio wave 66 projected on the reflecting mirror 61 are reflected by the reflecting mirror 61 as shown in the figure, and the reflected light and the reflected wave will be lost. Also focuses on the radiator 63 at the focal position 62.

Although not shown, the focus position 6
In some cases, a sub-reflector is disposed near the sub-reflector 2 and a radiator is installed near the focal point of the sub-reflector. However, sunlight 65 and radio waves 66 reflected by the sub-reflector are focused on the radiator.

[0005] The reflector of this conventional parabolic antenna has a condensing function not only for radio waves but also for sunlight, so that when the sun enters the field of view of the antenna, the radiator 3 is used.
Solar energy is concentrated on the sub-reflector and the sub-reflector, which may be damaged or deteriorate in performance due to high temperature.

The surface 61a of the reflector is usually painted,
To avoid this concentration of solar energy,
As disclosed in Japanese Patent Laid-Open No. 194805, some of them are coated with a matte paint, which is disclosed in JP-A-62-131611.
As disclosed in Japanese Unexamined Patent Publication, there is a reflector provided with irregularities such as a hairline on the surface 61a of the reflecting mirror.

[0007] A light-shielding cover 64 for shielding sunlight may be provided between the reflecting mirror 61 and the radiator 63.

[0008]

Concentration of sunlight by a reflector of a parabolic antenna is mounted on an antenna or an artificial satellite of a ground station that tracks an artificial satellite or an aircraft, where the sun often enters the field of view of the antenna. This is particularly problematic for antennas.

Further, since the amount of condensed light is proportional to the area of the parabolic surface, the problem is particularly serious in a large-diameter antenna.

In the method disclosed in Japanese Patent Application Laid-Open No. Sho 60-194805, in which a matte paint is applied to the surface of a reflecting mirror, a part of sunlight is irregularly reflected, so that the condensing on the radiator is eased. However, as the aperture of the antenna increases, the adverse effect of temperature rise due to light collection cannot be avoided.

In the method disclosed in Japanese Patent Application Laid-Open No. 62-131611, in which the surface of the reflecting mirror is provided with irregularities such as a hairline, a part of sunlight is irregularly reflected, and condensing on the radiator is reduced. However, if the aperture of the antenna is large, a rise in temperature due to light collection is inevitable, and processing is difficult and processing costs are high.

In the method of providing a light-shielding cover between the reflecting mirror and the radiator for shielding sunlight, as the aperture of the antenna becomes larger and the condensing energy increases, the heat-resistant temperature of the cover is limited. The size of the cover also increases, and the weight of the cover and its supporting structure increase.

An object of the present invention is to provide a reflector for a parabolic antenna which can overcome the above-mentioned drawbacks, avoid a rise in temperature of a radiator or the like due to the reflection of sunlight, and can cope with a large-diameter parabolic antenna. To provide.

[0014]

The reflector of the parabolic antenna of the present invention is characterized in that a retroreflective material is adhered to the surface of the radio wave reflecting surface.

The retroreflective material may be fine glass beads, or a fine corner cube having an equilateral triangular surface facing the outer surface of the parabolic antenna.

[0016]

[Function] The retroreflective material can be used regardless of the irradiation direction of light.
Since it has the property of reflecting the incident light in the irradiation direction, the sunlight irradiated on the reflector is reflected in the direction of the sun and is not focused on the focal point of the reflector.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a schematic view of a first embodiment of the present invention.
FIG. 2 is a partial sectional view of the reflecting mirror according to the first embodiment of the present invention.

As shown in FIG. 2, glass beads 24 are arrayed on the entire surface 22 of the reflecting mirror 21 of the parabolic antenna using a paint 23 as a medium. In this case, a paint is used as a substrate in this embodiment, but an adhesive may be used.

Due to the optical properties of the glass beads 24, the sunlight 25 incident on the reflecting mirror surface is reflected in the incident direction regardless of the incident direction. This principle is known as retroreflection, and paint containing glass beads is widely used as a light reflection paint for road signs and the like. Due to this action, sunlight does not converge at the focal point of the reflector.

The reflection angle θr of the glass beads is given by the following equation from the geometric relationship between refraction and reflection.

Θr = 2Sin ^-1 (r) -4Sin ^-1 (r / n) In this formula, r is the position of the incident light beam when the radius of the glass beads is normalized to 1, and n is the refractive index of the glass beads. Is.

FIG. 3 shows the relationship between the incident position r and the reflection angle θr using the refractive index n as a parameter. As shown in the figure, by selecting the refractive index n to be around 1.75, it is possible to obtain a characteristic of reflecting light incident within approximately 90% of the radius within ± 10 ° of the incident direction.

FIG. 4 is a partial sectional view of a second embodiment of the present invention, which uses a minute corner cube 44 as a retroreflective material that reflects sunlight. As shown in FIG. 4, on the surface 42 of the reflector 41 of the parabolic antenna, a corner cube 44 is disposed on the entire surface of the reflector 41 of the parabolic antenna so that the equilateral triangular surface thereof faces the outer surface of the parabolic antenna.

The equilateral triangular surface of the corner cube has a function of reflecting at an angle of reflection of 0 ° in the incident direction irrespective of the incident direction of the incident light, and a higher retroreflective performance than glass beads is obtained.

FIG. 5 is a schematic diagram showing the structure of a corner cube. The corner cube has three reflection surfaces perpendicular to each other in the shape of a cube cut off as shown in FIG. 5, light enters from the BCD surface, and is regularly reflected once on each of the three surfaces, and then again reflected from the BCD surface in the incident direction. Get out. It is also used for road signs as well as reflectors such as interferometers.

Since glass beads and corner cubes are made of glass and are a dielectric material through which radio waves are transmitted, radio waves pass through them and are reflected by the surface of the reflecting mirror. Therefore, the function and performance of the parabolic antenna are not affected except for a small transmission loss due to absorption of the dielectric. The use of quartz glass or borosilicate glass can reduce the loss factor (tan [delta), 4 × 10 ^-4 in a quartz glass, a 2 × 10 ^-2 about a borosilicate glass.

Assuming that the diameter of the glass beads is 0.3 mm and the occupation ratio of the glass beads on the reflecting mirror surface is 50%, the average thickness of the glass beads is 0.1 mm. On the other hand, the loss factor of the silicone resin paint used for coating the reflecting mirror surface, which is strong against ultraviolet rays, is about 5 × 10 ^-3 and the thickness is about 0.1 mm. Therefore, the absorption of radio waves by the glass beads is about the same as that of the silicone resin paint, and the adoption thereof does not have a great influence on the antenna performance.

Glass beads are used for road marking paints.
There is a standard of IS R3301, and a standard product with stable performance can be obtained at low cost. In addition, it is possible to utilize a wealth of know-how regarding economical construction methods that apply with paint.

[0030]

As described above, according to the present invention, since the retroreflective material is adhered to the surface of the reflector of the parabolic antenna, the regular reflection component of sunlight can be suppressed, and Sunlight can be eliminated. Since most of the incident light is reflected in the incident direction instead of the diffuse reflection, there is little reflection at the focal point, and this is also effective for a large reflecting mirror.

Glass beads, which are a kind of retroreflective material, have a long track record for use as road signs.
Because there are standards, it is possible to obtain standard products with stable performance at low cost, and it is possible to economically prevent sunlight from converging on the focal point of the parabolic antenna by utilizing the know-how of the construction method of applying it with paint.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment of the present invention.

FIG. 2 is a partial sectional view of the reflecting mirror according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between an incident position and a reflection angle using a refractive index as a parameter.

FIG. 4 is a partial sectional view of a reflecting mirror according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a structure of a corner cube.

FIG. 6 is a schematic diagram of a conventional parabolic antenna.

[Explanation of symbols]

 Reference Signs List 11 reflector 11a reflector surface 12 focal position 13 radiator 15 sunlight 16 radio wave 21 reflector 22 reflector surface 23 paint 24 glass beads 25 sunlight 41 reflector 41 reflector surface 43 base material 44 corner cube 45 sunlight 61 Reflecting mirror 61a Reflecting mirror surface 62 Focus position 63 Radiator 64 Light shielding cover 65 Sunlight 66 Radio wave

Claims (3)

[Claims] 1. A reflector for a parabolic antenna for transmitting and receiving radio waves, wherein a retroreflective material is adhered to a radio wave reflection surface. 2. The parabolic antenna reflecting mirror according to claim 1, wherein the retroreflective material is fine glass beads. 3. The reflector of a parabolic antenna according to claim 1, wherein the retroreflective material is a small corner cube.
A reflector of a parabolic antenna, wherein an equilateral triangular surface of the corner cube is arranged toward an outer surface of the parabolic antenna.