JPS61255106A - Antenna system - Google Patents

Abstract

PURPOSE:To improve the deterioration in a broad angle directivity due to the reflection or diffraction from a support by arranging continuously N sets of composite polygon elements each having a length longer than the wavelength of the operating radio wave, made of a radio wave absorbing material whose projected area to a main reflection mirror aperture is proper to the surface to the support for a primary radiator or the like. CONSTITUTION:The support I supporting a primary radiator or a sub reflection mirror is equipped with plural composite polygon elements 3 arranged continuously to the face of the main reflection mirror and the length L of the elements 3 in the axial direction of the support 1 is sufficiently longer than the wavelength of the operating radio wave. The length L of each element 3 is selected equal, the surface of each element 3 consists of three planes bent corresponding to the progressing direction 101 of a plane wave 102, and the radio wave absorbing element 2 is provided on the surface. The axial length of said three planes in the axial direction of the support 1 is divided into three with respect to the length L and the length of three divisions is selected to about several times of the wavelength of the operating radio wave. Thus, together with the absorbing action by the radio wave absorbing members 2, the irradiated angle is scattered to the scattered wave at the ridge not absorbed by the elements 2 and the level of the scattered wave liable to be concentrated onto a specific direction is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an antenna device, and in particular, an aperture antenna including a main reflector used in a microwave band or a quasi-ξ wave band, which is compatible with the main reflector. The present invention relates to an antenna device that improves deterioration of wide-angle directivity characteristics due to reflection and diffraction of pillars d- and the like that support a primary radiator or sub-reflector arranged as a primary radiator or a sub-reflector.

[Conventional technology]

An aperture antenna comprising a main reflector and a primary radiator or sub-reflector arranged corresponding to the main reflector is generally used as a communication antenna in the microwave band or sub-millimeter wave band due to its usefulness. It is often used. In particular, an axially symmetrical Cassegrain (or Gregorian) antenna with a sub-reflector has low noise characteristics and is therefore widely used as an antenna for earth stations for satellite communications.

In this Cassegrain antenna, the sub-reflector is located in the center of the propagation path of radio waves reflected by the main reflector and radiated in a predetermined main direction. The radio waves are reflected and diffracted by a plurality of pillars supporting the mirror, and... side a-p in a certain direction.

There is a problem in that the wide-angle directional characteristics of the Cassegrain antenna deteriorate. In general, in order to eliminate radio wave interference between systems, the wide-angle directional characteristics of antenna devices include CCIR (Co
m1te Conultatif Internat
ional T515graphique et Te
1ephonique (International Radiocommunications Advisory Committee) has recommended evaluation criteria.

What is shown in FIG. 3 is an example of a general bottle configuration of the above-mentioned Cassegrain antenna, in which the main reflector 4. Sub-reflector 5. It includes a primary radiator 6 and a plurality of struts 1. Referring to FIG. 3, the spherical wave emitted from the primary radiator 6 is reflected by the sub-reflector 5, re-reflected by the main reflector 4, and the plane wave 1
02 in the main direction. A part of this plane wave is reflected by the pillar 1, diffracted, and radiated in the direction of the scattering cone 103, causing the deterioration of the wide-angle directivity characteristics as described above. Further, a part of the above-mentioned reflected wave reflected by the sub-reflector 5 is reflected by the side surface of the main reflector side of the support 1 in the direction of the cone 104, and the wave is reflected by the main reflector 4 into an ellipse. It is radiated in the direction of the cone 105.

Conventionally, as a method for reducing the scattered waves due to reflection and diffraction from the plurality of pillars 1 (usually 3 or 4) and improving the deterioration of wide-angle directional characteristics, the main reflecting mirror of the pillar 1 of the sub-reflecting mirror 5 has been Efforts have been made to reduce the scattered waves from the support column 1 by adding a radio wave absorbing material to the support column 1. Figure 2(a).

(b) and (C1) show a part of a support in this conventional antenna device and a conceptual cross-sectional view of the support. FIG. 2 11 shows a part of one of the multiple support FIG. 6 is an enlarged diagram showing the correspondence relationship with the traveling direction of the radio waves reflected by the main reflecting mirror. In FIG. 2 (al), a radio wave absorbing material 2 is attached to the side surface of the support 1 on the main reflecting mirror side, and a part of the plane wave 102 reflected from the main reflecting mirror 4 is directed in the traveling direction 101. Arriving along,!Liquid absorbing material 2
T-one opposite! The ink is set on the post 1 attached to the base. This state is shown as a conceptual cross-sectional view in a plane including the traveling direction 101f of the plane wave 102 in the second example) and (C). In the case of Fig. 2 (B), the radio wave absorbing material 2 is provided on the side surface of the main reflecting mirror side of the column 1 with a square cross section, and in the case of Fig. 2 (C), the column with an elliptical cross section is provided. A radio wave absorbing material 2 is provided on the side surface of the main reflecting mirror 1.

[Problem rate that the invention attempts to solve]

In the above-mentioned conventional antenna device, - for example, the second
(Review) or (c)K As shown, a radio wave absorbing material 2 is provided on the side surface of the main reflecting mirror side of the column 1. A part of the plane wave 102 that is sequentially reflected by the main reflecting mirror 4 reaches the pillar 1 along the traveling direction 101, but due to the presence of the radio wave absorbing material 2, compared to the case without the radio wave absorbing material 2. Although reflected waves in a specific direction are reduced by this method, it is not necessarily effective in all directions of the scattering cone 103 in FIG. For example, K as shown in FIG.

When the support column 1 has a rectangular cross section, the absorption effect of the radio wave absorbing material 2 is almost ineffective with respect to the scattered waves generated at the peripheral edges 106 and 107 of the radio wave absorbing material 2 facing the normal wave 102, and the absorption effect of the radio wave absorbing material 2 is almost ineffective. Also. As shown in Fig. 2(c)&C, when the strut 1 has an oval cross section, the strut 1
The plane wave 102 incident at 1C is as follows.

The light is incident on the radio wave absorbing material 2 almost obliquely. General: When a radio wave is obliquely incident on a radio wave absorbing material, the absorption effect of the radio wave absorbing material on the radio wave decreases, and the amount of reflected waves increases relatively. Therefore, Figure 2 (
c) In the case of the pillar shown in K, this results in an increase in the level of scattered waves due to reflected waves corresponding to the elliptical curved surface.

That is, in both cases Φ) and (C1 in FIG. 2), there is a problem in that the level of the scattered waves radiated by the pillar 1 in the direction of the scattering cone 103 cannot be suppressed to a sufficiently low level.

[Means for solving problems]

In order to solve the above-mentioned problems, an antenna device of the present invention includes a primary radiator or a sub-reflector disposed corresponding to a main reflector, in which the primary radiator or the sub-reflector is supported. A dimension Lt (i-1, 2,
3,..., N: N is a positive integer) f: has, respectively,
A radio wave absorbing material is applied to part or all of the surface, and it is formed of a composite of a flat surface and an arbitrary curved surface, and the projected area to the main reflecting mirror aperture is equal to the projected area of the pillar itself, or By arranging N relatively large composite polyhedral elements in a chain along the axial direction of the pillar,
It has the ability to irregularly change the direction of reflected waves from nine places and scattered waves from the periphery, which cannot be sufficiently attenuated by radio wave absorbing materials alone, and prevent energy from being concentrated in a specific direction.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1(a) is a diagram partially displaying one of the plurality of supports supporting the primary radiator or the sub-reflector in the antenna device of the present invention as an example.
Figure-) and (C1 are respectively the AA arrow view and the BB arrow view in Fig. 1 1al).

As shown in the first figure, the strut of this example is the strut 1
and a plurality of composite multifaceted elements 3 each having a radio wave absorbing material 2 applied to one surface thereof, which are arranged in a chain on the main reflecting mirror side surface of the pillar 1.

In FIG. 1 al, the length of the composite multifaceted element 3 arranged in a chain with respect to the support 1 is L along the axial direction of the support 1. In FIG. The value of L is selected to be sufficiently long with respect to the wavelength of radio waves used by the antenna device, but the general value does not need to be equal for each composite polyhedral element 3. Further, the height h of each element is varied by two to three times the wavelength used. The composite polyhedral element 3 can take various embodiments, but in this embodiment.

The lengths of L are selected to be equal to each other, and the surface of each composite polygonal element 3 is arranged in the traveling direction 10 of the plane wave 102.
1, it is composed of three bending planes, and a radio wave absorbing material 2 is applied to the surface thereof. FIGS. 1(b) and 1(c) show the AA arrow view and the BB arrow view in FIG. 1 1a), as described above. In Fig. 1(c)&C, the plane wave of the composite polygonal element 3 is 102K.
The opposing surfaces are composed of three bent planes as described above, and the lengths LK of these three planes in the axial direction of the supports 1 of the composite multifaceted element 3 are The dimension along is divided into three. In this case, the length divided into three parts is:

A necessary condition is to set the wavelength to at least several times the wavelength of the radio waves used.

As shown in Figure 1), Φ) and (C1), in response to the plane wave 1024C, a multifaceted element 3 consisting of a plane having dimensions of at least several wavelengths is attached to the main reflecting mirror side surface of the support 1. By arranging a plurality of radio wave absorbing materials 2 along the axial direction of the multifaceted element 3 and applying the radio wave absorbing material 2 to each plane forming the multifaceted element 3, the absorption effect by the radio wave absorbing material 2 and the phase t-) can be achieved.
For the scattered waves at the periphery that cannot be sufficiently absorbed and suppressed by the radio wave absorbing material 2 alone, the angle of incidence of the plane wave 102 on the periphery of each composite polygonal element is irregular for each periphery. Due to its diversity, it is possible to disperse the radiation angle of the scattered waves from the periphery and reduce the level of the scattered waves that tend to concentrate in a specific direction. Furthermore, since the incident angle of the plane wave 1020 on each plane to which the radio wave absorbing material 2t, which forms each of the above-mentioned multifaceted elements 3, is applied has irregular diversity, The level of the reflected wave and its radiation angle can be dispersed together, and as a result, the scattered waves that tend to be concentrated in a specific direction due to one reflected wave can be diffused, and the level can be reduced.

In the above explanation, we have explained the simple table formed by combining simple planes as a composite polygon element, but in general, each face of a composite polygon element can be a plane or an arbitrary curved surface. By forming the surface as a three-dimensional outer composite surface consisting of, etc., it is possible to further improve the scattering effect of the scattered waves.

Furthermore, regarding the formation of the radio wave absorbing material applied to each surface of the composite multifaceted element, there are cases in which a radio wave absorber is attached to each surface, a paint that has a radio wave absorbing effect is applied, and a material that has a radio wave absorbing effect itself is used. It is clear that the present invention is applicable to cases where various methods are used, such as when forming the composite polyhedral element. Furthermore, according to the present invention, the level of scattered waves emitted in a specific direction of the elliptic cone 105 shown in FIG. 3 is significantly reduced due to the radio wave absorption effect and diffusion effect of the composite polyhedral element.

〔Effect of the invention〕

As described above in detail, the present invention is applied to an antenna device comprising a primary radiator or a sub-reflector disposed corresponding to a main reflector, and wherein the primary radiator supports the sub-reflector. The level of scattered waves generated by being reflected and diffracted by a plurality of pillars is relatively reduced through the radio wave absorption effect, and the radiation direction of the scattered waves is diffused to reduce the scattered waves concentrated in a specific direction. Suppressing the level has the effect of improving the wide-angle directional characteristics.

[Brief explanation of the drawing]

11), (b) and (C) are views showing one embodiment of the support of the primary radiator or sub-reflector in the present invention, and FIG. 2 (a), Φ) and Ic) are views showing the conventional FIG. 3 is an explanatory diagram of an example of a support in the antenna device, and FIG. 3 is a configuration diagram of a Cassegrain fist antenna. In the figure, 1... Support column, 2... Radio wave absorbing material, 3... Composite multifaceted element, 4...
・Main reflector, 5...Sub reflector, 6...
Primary radiator.

Claims (4)

[Claims] (1) In an antenna device equipped with a primary radiator or a sub-reflector arranged corresponding to a main reflector, facing the mirror surface of the main reflector of each support supporting the primary radiator or sub-reflector. A dimension L_i (i=1,
2, 3, ..., N: N is a positive integer), each has a radio wave absorbing material applied to a part or the entire surface, and is formed by a composite of a flat surface and an arbitrary curved surface, etc. An antenna device comprising N composite polyhedral elements arranged in a chain along the axial direction of the support. (2) Dimension L along the axial direction of the pillars of N composite multifaceted elements
The antenna device according to claim 1, wherein _i is defined as a predetermined irregular dispersion value. (3) Dimension L along the axial direction of the pillars of N composite multifaceted elements
The antenna device according to claim (1), wherein _i are each defined as the same predetermined value. (4) The projected area of the surface provided with the radio wave absorbing material of the composite multifaceted element disposed on the support with respect to the main reflecting mirror aperture is relative to the projected area of the main reflecting mirror with respect to the main reflecting mirror aperture of the support itself. The antenna device according to claims (1), (2), and (3), wherein the antenna device is set to a value exceeding .