JPH09199937A - Dual reflection mirror paraboloidal antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensitivity and durability by devising the shape of a feedome covering a tip of a primary radiator so as to minimize the effect of the feedome. SOLUTION: The antenna system is provided with a main reflection mirror 1, a sub reflection mirror 2 located in the vicinity of the focus of the sub reflecting mirror and a circular waveguide feeder 3 whose tip is located in the vicinity of the focus of the sub reflection mirror 2. The system incorporates the sub reflection mirror 2 and a partial spherical shell structure around the focus of the main reflection mirror 1 is adopted for a part of a nonconductive feedome 10 covering the tip of the feeder 3 to which a reflected wave from at least the main reflection mirror 1 passes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-reflecting mirror type parabolic antenna device, and more particularly to a double-reflecting mirror type parabolic antenna device for receiving satellite broadcasting and satellite communication.

[0002]

2. Description of the Related Art FIG. 4 shows the overall structure of a conventional parabolic antenna device having multiple reflectors, FIG. 5 shows the primary radiator portion thereof, and FIG. 6 shows how a reflected wave from a main reflector enters the primary radiator. FIG. 7 is an enlarged view of the situation. As shown in these figures, the conventional double-reflection parabolic antenna device has a main reflecting mirror 1, a sub-reflecting mirror 2 placed near the focus f of the main reflecting mirror 1, and a focus f of the sub reflecting mirror 2. 'A circular waveguide feeder 3 as a power feeding means placed so as to open near. Usually, the circular waveguide feeder 3 is fixed to the main reflecting mirror 1 side, and the sub-reflecting mirror 2 is fixed to the main reflecting mirror 1 or the circular waveguide feeder 3 by some method (in FIG. 4 to FIG. (Fixed through), the tip end opening portion of the circular waveguide feeder 3 and the sub-reflecting mirror 2 constitute a primary radiator.

[0003]

By the way, the primary radiator of the double-reflection parabolic antenna device must satisfy the following conditions.

(1) When the sub-reflecting mirror is attached to the waveguide feeder, the sub-reflecting mirror must be fixed to the waveguide feeder by a method that has little influence on electromagnetic waves.

(2) In the parabolic antenna device which is often used outdoors, the tip of the primary radiator must have a waterproof structure.

Therefore, in the conventional double-reflection parabolic antenna device shown in FIGS. 4 and 5, if a material that transmits a low dielectric constant electromagnetic wave well is used for the fidome 4 which is the cover of the tip of the primary radiator, Conditions (1) and (2) can be satisfied to some extent. However, although the fidome 4 is actually composed of a molded product of synthetic resin, since the actual synthetic resin has a higher dielectric constant than the dielectric constant in the atmosphere (air), the property is different from that in the case without the fidome. Comes out. In this type of parabolic antenna device, it is particularly important to accurately concentrate the electromagnetic waves collected from the main reflecting mirror at its focal point, but in the case of the conventional structure shown in FIG. The synthetic resin wall surface of the fidome 4 is positioned obliquely with respect to the path, and the electromagnetic wave is refracted when entering and passing through the fidome 4, and the course of the electromagnetic wave is as shown in the enlarged views of FIGS. 6 and 7. Deviation (dotted line in the figure indicates the path of the electromagnetic wave when there is no fidom, solid line indicates the path of the electromagnetic wave deviated by the fidome), and as a result, the focus is blurred and the sensitivity decreases. The deviation of the course due to the refraction of the electromagnetic wave becomes more remarkable as the thickness of the synthetic resin wall of the fidome 4 increases and the dielectric constant of the synthetic resin increases.

In Japanese Utility Model Publication No. 60-22655, a structure is proposed in which the sub-reflecting mirror is fixed to the main reflecting mirror with a synthetic resin cover. In this case as well, when electromagnetic waves pass through the synthetic resin cover. The adverse effect of refraction occurs.

In view of the above points, the present invention devises the shape of the fidome covering the tip portion of the primary radiator to minimize the influence of the fidome and to improve the performance even if the thickness of the fidome is increased to some extent. An object of the present invention is to provide a parabolic antenna device of the double-reflecting mirror type, which is not deteriorated so much as to improve the sensitivity as compared with the conventional device, and has increased durability, high performance and robustness.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0010]

In order to achieve the above object, a parabolic antenna device of a double-reflecting mirror type according to the present invention comprises a main reflecting mirror and a sub-reflecting mirror located near the focal point of the main reflecting mirror.
In a structure having a power feeding means whose tip is located near the focal point of the sub-reflecting mirror, a wave reflected by at least the main reflecting mirror of a non-conductive fidome that contains the sub-reflecting mirror and covers the tip of the power feeding means. Is a partial spherical shell-like structure centered on the focal point of the main reflecting mirror.

The radius of curvature of the partial spherical surface, which is the inner surface of the partial spherical shell-like structure, is approximately 1/2 of the diameter of the sub-reflecting mirror.
It is desirable that the distance between the focal point of the main reflecting mirror and the focal point of the sub-reflecting mirror be approximately 1/2 of the diameter of the sub-reflecting mirror.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a parabolic reflector type parabolic antenna device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall structure of a parabolic antenna device for a double-reflecting mirror according to an embodiment of the present invention, FIG. 2 shows its primary radiator portion, and FIG. 3 shows how reflected waves are incident on the primary radiator. . As shown in these figures, the double-reflection parabolic antenna device includes a main reflecting mirror (parabolic reflecting mirror) 1
And a sub-reflecting mirror 2 placed near the focus f of the main reflecting mirror 1 (slightly front side of the focus f) and a focus f ′ of the sub-reflecting mirror 2.
A circular waveguide feeder 3 as a feeding means placed so as to open in the vicinity of the circular waveguide feeder 3; and a non-conductive fidome 10 which incorporates the sub-reflecting mirror 2 and covers the tip opening portion of the circular waveguide feeder 3. ing.

The main reflecting mirror 1 is a concave mirror formed by molding a metal plate or metallizing the surface of synthetic resin or the like. For example, in the case of a Cassegrain antenna device, the reflecting surface is a parabolic reflecting mirror. Is. The sub-reflecting mirror 2 is a convex mirror formed by molding a metal plate or metallizing the surface of synthetic resin or the like, and is a hyperboloidal reflecting mirror whose reflecting surface is a hyperboloid in the case of a Cassegrain antenna device.

The circular waveguide feeder 3 has an open tip, and the tip portion constitutes a primary horn that sends or receives an electromagnetic wave. This circular waveguide feeder 3
Is a center-feed structure that extends through the center of the main reflecting mirror 1 to reach the focal point f ′ of the sub-reflecting mirror 2.
It is preferable that the focal point f ′ is located slightly inside the opening 3 a of the circular waveguide feeder 3. The circular waveguide feeder 3 is fixed and supported by a base member 15 fixed on the back side of the main reflecting mirror 1.

As shown in FIGS. 2 and 3, the non-conductive fidome 10 provided as a cover for covering the primary radiator portion having the primary horn at the tip of the circular waveguide feeder 3 and the sub-reflecting mirror 2. It is made of a synthetic resin that is excellent in weather resistance and that allows transmission of electromagnetic waves having a low dielectric constant. Here, the fidome 10 is formed by integrally combining a main body portion 11 having a hemispherical shell-like structure and a lid body portion 12 in a watertight manner by bonding or the like.

As described in the description of the prior art, since the synthetic resin forming the fidome 10 has a dielectric constant larger than that in air, the influence of the fidome 10 on the reflected wave reflected by the main reflecting mirror 1. The following conditions (a) and (b) are desired to suppress this.

(A) The thickness of the synthetic resin wall of the fidome 10 is made as thin as possible.

(B) The influence of refraction of electromagnetic waves by the fidome 10 is eliminated as much as possible.

The condition (a) is the strength of the fidome 10,
Since there is a structural problem, the wall thickness cannot be made very thin, and it is difficult to specifically set the wall thickness of the synthetic resin wall forming the fidome 10 to 1 mm or less.

Therefore, the present inventor pays attention to the condition (b) and devises the shape of the fidome 10 so that the electromagnetic wave (reflection wave by the main reflecting mirror 1) incident on the fidome 10 always enters vertically. . That is, the focus f of the main reflecting mirror 1 is set so that all the electromagnetic waves reflected by the main reflecting mirror 1 enter the main body 11 of the fidome 10 vertically to the wall surface of the fidome.
It has a hemispherical shell-like structure centered at. By doing so, as shown in the enlarged view of FIG. 3, all the reflected waves are perpendicularly incident on the wall surface of the fidome in the portion where the reflected waves of the main body portion 11 of the fidome 11 pass, and thus, in the air and the fidome. It is possible to eliminate the influence of refraction due to the difference in dielectric constant between the ten synthetic resins. The central portion of the main body portion 11 is a cylindrical portion 11a fitted and fixed to the outer periphery of the tip end portion of the circular waveguide feeder 3.

In order for the fidome 10 to play its original role, the sub-reflecting mirror 2 and the tip of the circular waveguide feeder 3 must be housed in the fidome 10. At this time, the size of the fidome 10 that is the most compact is that, as shown in FIG. It is about 1/2 of the diameter D of the outer circumference circle. In some cases, the center of the outer circle of the sub-reflecting mirror 2 and the position of the focal point f of the main reflecting mirror 1 do not completely coincide with each other (in FIG. 2, the focal point f is located behind the center of the outer circumferential circle.
Is located), and the radius of curvature R does not always match D / 2. In any case, the central axis of the main reflecting mirror 1 and the central axis of the sub-reflecting mirror 2 are made to coincide with each other so that the sub-reflecting mirror 2 is inscribed in the hemispherical surface of the inner surface of the main body 11 (in other words, the sub-reflecting mirror). It may be set so that the hemispherical surface of the inner surface of the main body 11 contacts the mirror 2). Assuming that the fidome has a main body with a curvature radius R that is larger than necessary compared to D / 2,
The presence of the fidome with respect to the main reflecting mirror 1 causes blocking, which is not preferable.

The position of the focal point f'of the sub-reflecting mirror 2 is in the vicinity of the opening 3a of the circular waveguide feeder 3, and preferably at a position slightly inside the circular waveguide feeder 3 rather than the opening. , The electromagnetic wave reflected from the sub-reflector 2
It is necessary not to be blocked by the inner wall surface of the fidome 10 when it is focused on the focal point f ′. For this reason, the distance L between the focal point f of the main reflecting mirror 1 and the focal point f'of the sub reflecting mirror 2 is set to approximately 1/2 of the diameter D of the sub reflecting mirror 2 (substantially matched with the radius of curvature R). .). If you do this,
The focal point f'is almost located on the extension surface of the hemispherical surface of the inner surface of the main body portion 11, and the focal point f'is located near the opening of the circular waveguide feeder 3 and the reflected wave by the sub-reflecting mirror 2 is on the inner surface of the fidome. You can set it so that it is not blocked.

The overall operation of the double-reflecting mirror parabolic antenna device according to this embodiment will be described in the case of reception.

Electromagnetic waves coming from broadcasting satellites and communication satellites are reflected by the main reflecting mirror 1 toward the focal point f thereof, but the main body 11 of the fidome 10 facing the main reflecting mirror 1 is centered around the focal point f. Since it has a hemispherical shell-like structure, the reflected wave from the main reflecting mirror 1 is incident perpendicularly on the wall surface of the fidome 10, and therefore travels in a direction in which it is focused on the focal point f without being refracted. Then, it is reflected by the sub-reflecting mirror 2 toward its focal point f ′, and the reflected wave is focused in the opening of the circular waveguide feeder 3. At that time, the radius of curvature R of the hemispherical surface of the inner surface of the hemispherical shell-like structure of the main body portion 11 is set to about 1/2 of the diameter of the sub-reflecting mirror 2 (the diameter of the outer circumferential circle of the sub-reflecting mirror 2) and By setting the distance L between the focal point f of the reflecting mirror 1 and the focal point f ′ of the sub-reflecting mirror 2 to be approximately ½ of the diameter D, the blocking of the main reflecting mirror 1 due to the fidome 10 is minimized. Moreover, the reflected wave from the sub-reflecting mirror 2 can reach the opening 3a of the circular waveguide feeder 3 without being blocked by the inner surface of the fidome 10.

As the material of the fidome 10, a synthetic resin having a low dielectric constant and excellent weather resistance, such as fluororesin (Teflon), acrylic, or polycarbonate, can be selected. Further, a small protrusion or the like for positioning the sub-reflecting mirror may be formed on the inner surface of the fidome 10.

According to this embodiment, the following effects can be obtained.

(1) The main body 11 through which the reflected wave from the main reflecting mirror 1 of the non-conductive fidome 10 which contains the sub-reflecting mirror 2 and covers the tip of the circular waveguide feeder 3 as the power feeding means is Since it has a hemispherical shell-like structure with the focal point f of the main reflecting mirror 1 at the center, the reflected wave from the main reflecting mirror 1 is incident perpendicularly on the wall surface of the fidome 10 and is focused in the focal point f without being refracted. proceed. Therefore, it is possible to prevent a decrease in sensitivity due to refraction when passing through the fidome, which is a problem in the conventional parabolic antenna device, and it is possible to improve the sensitivity as compared with the conventional parabolic antenna device.

(2) The radius of curvature R of the hemispherical surface, which is the inner surface of the hemispherical shell-like structure of the fidome main body 11, is approximately 1/2 of the diameter of the sub-reflecting mirror 2 (the diameter of the outer circumferential circle of the sub-reflecting mirror 2). Since the sub-reflecting mirror 2 is inscribed and supported and fixed on the inner surface of the hemispherical shell-like structure, the shape of the fidome 10 can be minimized, and the main reflecting mirror caused by the fidome 10 is formed. Blocking for 1 can be reduced. Further, by setting the distance between the focal point f of the main reflecting mirror 1 and the focal point f'of the sub reflecting mirror 2 to be approximately 1/2 of the diameter D of the sub reflecting mirror 2, the reflected wave by the sub reflecting mirror 2 is Can reach the opening of the circular waveguide feeder 3 without being blocked by. Therefore, also in these points, the sensitivity can be improved.

(3) Since the circular waveguide feeder 3 is used as the power feeding means, in principle, any of horizontally polarized wave, vertically polarized wave and circularly polarized electromagnetic wave can be transmitted and received.

(4) When selecting the material of the fidome 10, there is a wide range of choices for the thickness of the dielectric and the material, except that high frequency loss (tan δ) must be taken into consideration, so that there is freedom in design. Furthermore, it becomes possible to make the fidome 10 a durable structure and a robust structure.

In the above embodiment, the fidome 10 is used.
Was a combination of the main body portion 11 and the lid body portion 12 having a hemispherical shell structure, but the main body portion facing the main reflecting mirror of the fidome does not necessarily have the hemispherical shell structure, and the reflection by the main reflecting mirror is not necessary. It suffices if only the portion through which the wave passes has a spherical shell shape. That is, it is sufficient if at least the portion through which the reflected wave from the main reflecting mirror passes has a partial spherical shell-like structure with the focal point of the main reflecting mirror as the center.

Further, the circular waveguide feeder 3 used as the power feeding means in the above-mentioned embodiment may be a primary horn in which the tip portion thereof is conically widened.

Further, although the circular waveguide feeder 3 is shown as being fixed to the main reflecting mirror 1 via the base member 15, it may be directly fixed to the main reflecting mirror 1.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0036]

As described above, according to the parabolic reflector antenna device of the present invention, the main reflecting mirror, the sub-reflecting mirror located near the focal point of the main reflecting mirror, and the sub-reflecting mirror. In a configuration having a power feeding means having a tip portion located near the focal point, a portion of the non-conductive fidome that contains the sub-reflecting mirror and covers the tip portion of the power feeding means passes through at least a reflected wave by the main reflecting mirror. Since the partial spherical shell-like structure centering on the focus of the main reflecting mirror is used, the influence of the fidome can be suppressed to a minimum. That is, since the electromagnetic wave reflected by the main reflecting mirror is made incident vertically on the wall surface of the fidome and passes through,
It is possible to eliminate the influence of the refraction of electromagnetic waves caused by the difference in dielectric constant between the fidome and the air, and prevent the sensitivity from decreasing due to the presence of the fidome. As a result, the sensitivity can be improved as compared with the conventional device.

Furthermore, the material of the fidome has the advantage that the degree of freedom in design is increased because the range of choices for the thickness of the dielectric and the material is widened, except that high frequency loss (tan δ) must be taken into consideration. It can also be a robust fidome structure with excellent durability.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an overall configuration of an embodiment of a double-reflection mirror type parabolic antenna device according to the present invention.

FIG. 2 is an enlarged side sectional view showing a primary radiator portion of an embodiment according to the present invention.

FIG. 3 is a partially enlarged cross-sectional view showing how a reflected wave from a main reflecting mirror passes through a fidome in the embodiment according to the present invention.

FIG. 4 is a side sectional view showing an overall configuration of a conventional double-reflection mirror type parabolic antenna device.

FIG. 5 is an enlarged side sectional view showing a primary radiator portion of a conventional double-reflecting mirror parabolic antenna device.

FIG. 6 is an enlarged cross-sectional view showing how a reflected wave by a main reflecting mirror in a conventional double-reflecting mirror type parabolic antenna device passes through a fidome.

7 is a partially enlarged cross-sectional view showing how an electromagnetic wave is refracted when passing through a fidome in the configuration of FIG.

[Explanation of symbols]

 1 Main Reflecting Mirror 2 Sub-Reflecting Mirror 3 Circular Waveguide Feeder 4, 10 Fidome 11 Main Body 12 Lid Body

Claims (3)

[Claims] 1. A multi-reflecting mirror parabolic antenna device having a main reflecting mirror, a sub-reflecting mirror located near the focal point of the main reflecting mirror, and a power feeding means having a tip end located near the focal point of the sub-reflecting mirror. In, in the non-conducting fidome that covers the tip of the power feeding means, at least a portion through which a reflected wave from the main reflecting mirror passes is a partial spherical shell whose center is the focal point of the main reflecting mirror. A parabolic antenna device having a multi-reflecting mirror, which is characterized in that it has a shape-like structure. 2. The parabolic antenna device of a double-reflecting mirror type according to claim 1, wherein a radius of curvature of a partial spherical surface which is an inner surface of the partial spherical shell-like structure is approximately 1/2 of a diameter of the sub-reflecting mirror. 3. The parabolic antenna of double-reflecting mirror type according to claim 1 or 2, wherein the distance between the focal point of the main reflecting mirror and the focal point of the sub-reflecting mirror is approximately 1/2 of the diameter of the sub-reflecting mirror. apparatus.