JPH08256014A - Antenna device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an antenna device with little gain reduction and radiation characteristic deterioration. [Structure] A sub-reflector is formed on a dielectric provided on the side opposite to the main reflector in the radio wave radiation direction of the antenna. [Effect] An antenna device can be obtained in which gain reduction due to blocking and radiation characteristic deterioration due to reflection / scattering are small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device used in a microwave band or a millimeter wave band.

[0002]

2. Description of the Related Art FIG. 5 (a) is a side view of a conventional antenna device of this type, and FIG. 5 (b) is a front view of the antenna device shown in FIG. In this figure, 1 is a primary radiator, 2 is a part of a rotating hyperboloid, and a sub-reflector in which one of two focal points is aligned with the phase center of the primary radiator, 3 is a part of a rotating paraboloid , A main reflecting mirror whose focal point coincides with the other focal point of the sub-reflecting mirror, 5 is a supporting column of the sub-reflecting mirror, 6 is a shield plate, and 7 is a radome.

The operation of the Cassegrain antenna will be described. The spherical wave emitted from the primary radiator 1 is reflected by the sub-reflecting mirror 2 in the direction of the main reflecting mirror 3, and is emitted from the spherical wave by the main reflecting mirror 3 as a plane wave in the direction of the front rotation axis of the main reflecting mirror 3. It

[0004]

Since the conventional antenna device is constructed as described above, the supporting column of the sub-reflector blocks the radio waves radiated in the axial direction of the front face of the main reflector. However, there are problems that the gain is reduced and the radiation pattern is deteriorated by the scattered waves of the supporting column.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an antenna device capable of suppressing a decrease in gain and deterioration of a radiation pattern.

[0006]

An antenna device according to a first embodiment of the present invention is provided with a cylindrical shield plate which includes an outer circumference of a main reflecting mirror and is provided in a direction in which radio waves are radiated, and which is provided on a side opposite to the main reflecting mirror. A plate made of a dielectric material is attached to the plate, and a sub-reflecting mirror is formed on the plate to eliminate the supporting column of the sub-reflecting mirror.

Further, the antenna device according to the second embodiment of the present invention includes a dielectric member attached to the side opposite to the main reflecting mirror of the cylindrical shielding plate which is provided in the radiation direction of the radio wave and includes the outer periphery of the main reflecting mirror. The sub-reflecting mirror and / or the main reflecting mirror formed on the plate of No. 1 are mirror-modified.

The antenna device according to the third embodiment of the present invention is a plate made of a dielectric material provided on the side opposite to the main reflecting mirror of the cylindrical shielding plate, and a metal grid is provided in addition to the portion where the sub-reflecting mirror is formed. Is provided.

Further, in the antenna device according to the fourth embodiment of the present invention, the thickness of the dielectric provided on the opposite side of the cylindrical shield plate from the main reflecting mirror is approximately 1/2 wavelength or 1 wavelength. Is.

[0010]

According to Embodiments 1 to 4 of the present invention, a cylindrical shielding plate is provided in the direction in which the radio wave is emitted, including the outer periphery of the main reflecting mirror, and is formed of a dielectric on the side opposite to the main reflecting mirror. By forming the sub-reflector on the plate, the blocking by the sub-reflector support column on the antenna aperture surface is eliminated, the gain reduction is suppressed and the scattering by the sub-reflector support column is eliminated, and the deterioration of radiation characteristics is suppressed. be able to.

[0011]

【Example】

Example 1. 1 is a diagram showing a first embodiment of the present invention,
Reference numeral 4 is a dielectric plate on which a sub-reflecting mirror is formed. Reference numerals 1, 3 and 6 are the same as those of the conventional example shown in FIG.

In the antenna device configured as described above, the sub-reflecting mirror is formed on the dielectric provided on the opposite side of the shield plate including the outer periphery of the main reflecting mirror from the main reflecting mirror. Since there is no support pillar, the radio wave radiated from the main reflector in the axial direction of the antenna is not blocked on the aperture surface, the gain reduction is reduced, and the scattering is eliminated to suppress the deterioration of the radiation characteristics. To be

FIG. 1 shows an example of a Cassegrain antenna.
The same effect can be obtained for the Gregorian antenna, the uncrossed Cassegrain antenna, and the uncrossed Gregorian antenna.

Example 2. 2 is a diagram showing a second embodiment of the present invention, in which 8 is a dielectric plate having a mirror-modified sub-reflector, and 9 is a mirror-reflected main reflector. Reference numerals 1 and 6 are the same as those in the first embodiment and operate in the same manner as in the first embodiment.

In the antenna configured as described above, the effect of blocking is not caused by the mirror surface modification, so that the desired gain or radiation characteristic can be achieved.

Embodiment 3. FIG. 3 is a diagram showing a third embodiment of the present invention. Reference numeral 10 is a dielectric body in which a sub-reflecting mirror is formed and a metal grid is provided in a portion other than the sub-reflecting mirror. In the figure, reference numerals 1, 3 and 6 are the same as those in the first embodiment and operate in the same manner as in the first embodiment.

In the antenna configured as described above, by providing the metal grid, the degree of distinction with respect to the radio wave having the polarized wave orthogonal to or close to the grid is improved.

Example 4. 4 is a diagram showing a fourth embodiment of the present invention, and 11 is a dielectric plate having a thickness of approximately 1/2 wavelength or 1 wavelength. In the figure, reference numerals 1, 3 and 6 are the same as those in the first embodiment and operate in the same manner as in the first embodiment.

In the antenna constructed as described above, the reflection of the radio wave radiated from the antenna can be reduced by making the dielectric approximately 1/2 wavelength or 1 wavelength thick. Gain reduction is reduced.

[0020]

As described above, according to the first embodiment of the present invention, since the sub-reflecting mirror is formed on the dielectric used as the radome, the supporting column of the sub-reflecting mirror disappears from the opening surface, so that the blocking is prevented. This is effective in suppressing gain reduction and deterioration of radiation characteristics.

Further, according to the second embodiment, the desired gain or radiation characteristic can be achieved by modifying the sub-reflecting mirror and the main reflecting mirror.

According to the third embodiment, the metal grid is provided on the dielectric plate attached to the opposite side of the main reflecting mirror of the tubular member provided in the radiation direction of the radio wave including the outer periphery of the main reflecting mirror. As a result, the degree of discrimination with respect to polarized waves orthogonal to or close to the grid is improved.

Further, according to the fourth embodiment, the thickness of the dielectric plate attached to the side opposite to the main reflecting mirror of the cylindrical member provided in the radiation direction of the radio wave including the outer circumference of the main reflecting mirror is approximate. 1/2
By setting the wavelength or one wavelength, it is possible to reduce the reflection of the radio wave radiated from the antenna, so that the gain reduction is reduced.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing Embodiment 4 of the present invention.

FIG. 5 is a diagram showing a conventional example of the present invention.

[Explanation of symbols]

1 primary radiator, 2 sub-reflecting mirror, 3 main reflecting mirror, 4 dielectric with the sub-reflecting mirror formed, 5 sub-reflecting mirror support pillar, 6 shield plate, 7 radome, 8 dielectric with sub-reflecting mirror modified Body, 9 a dielectric having a main reflecting mirror with a mirror surface modified, 10 a dielectric having a sub-reflecting mirror and a metal grid, 11 a dielectric having a wavelength of approximately 1/2 or 1 wavelength.

Claims (4)

[Claims] 1. An antenna device comprising a primary radiator, a sub-reflecting mirror, and a main reflecting mirror, wherein a cylindrical shield plate is provided in the direction of emission of radio waves, including the outer periphery of the main reflecting mirror. An antenna device characterized in that a plate made of a dielectric material is attached to the side opposite to the mirror, and a sub-reflecting mirror is formed on the plate. 2. A sub-reflecting mirror formed on a plate formed of a dielectric material, which is provided on the opposite side of the main reflecting mirror of a cylindrical shielding plate provided in the direction of emission of radio waves, including the outer periphery of the main reflecting mirror. The antenna device according to claim 1, wherein the main reflecting mirror is mirror-finished. 3. A cylindrical shield plate is provided in the direction of emission of radio waves, including the outer periphery of the main reflecting mirror, and a metal grid is provided on the plate formed by a dielectric attached to the side opposite to the main reflecting mirror. The antenna device according to claim 1 or 2, characterized in that: 4. A cylindrical shield plate is provided in a direction in which radio waves are radiated, including an outer periphery of the main reflecting mirror, and a thickness of a dielectric attached to the side opposite to the main reflecting mirror is approximately ½ wavelength. Or 1
The antenna device according to claim 1, wherein the antenna device has a wavelength.