JPS63215104A - Antenna for microwave - Google Patents

Abstract

PURPOSE:To eliminate the non-operating part of a sub reflection mirror generated due to the shielding of the sub reflection mirror and to enable a primary radiator to be approached to the sub reflection mirror, by arranging a main reflection mirror, the sub reflection mirror, and the primary radiator so that two offset Gregorian type antenna can be constituted. CONSTITUTION:The two offset Gregorian type antenna are constituted by combining a focal point 1 on an axis and focal points 2 and 2' off the axis. In other words, the cross section of one offset type Gregorian type antenna is formed with a part of a parabola in which the focal point 1 is set as the focal point and a part of an ellipse in which the focal point 1 and the focal point 2 are set as the focal points, and similarly, the cross section of another offset Gregorian type antenna is formed with a part of the parabola by the focal points 1 and 2', and a part of the ellipse. In such a way, it is possible to remove the shielding of the sub reflection mirror, and also, to enable the primary radiator to be approached to the sub reflection mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reflection-type microwave antenna used for antennas with frequencies in the microwave band or sub-millimeter wave band.

[Conventional technology]

A conventional microwave antenna has one or two focal points, and has a structure including a main reflecting mirror and a sub-reflecting mirror in the shape of a paraboloid, a hyperboloid, or an ellipsoid.

As an example of improvement of this Ume microwave antenna, there is a technique disclosed in Japanese Unexamined Patent Publication No. 59-15120!1.

[Problem that the invention seeks to solve]

A microwave antenna having a main reflecting mirror and a sub-reflecting mirror having the shapes of a paraboloid, a hyperboloid, or an ellipsoid as described above is called a Cassegrain type or a Gregorian type. In this Cassegrain or Gregorian antenna, due to the escape of the sub-reflector, some of the radio waves emitted from the primary radiator cannot be radiated from the main reflector, or the radio waves collected by the main and sub-reflector are not radiated to the primary radiator. There was a problem with the vessel not being able to receive damage efficiently.

No.! FIG. 1 shows the positional relationship of the primary radiator, sub-reflector, and main reflector in a conventional Cassegrain microwave antenna using an axial cross-sectional view. This microwave antenna has a main reflector 9. It is composed of a sub-reflector 10 and a primary radiator 11, and has two focal points 12 and 13. The main reflecting mirror 9 is a rotational paraboloid with a focal point 13 as its focus, and the sub-reflecting mirror 10 is a rotational hyperboloid with focal points 12 and 13 as focal points.

In the microwave antenna having such a configuration, due to the shielding by the sub-reflector 10, when a radio wave is received, there is no radio wave in the shaded area 14 considering geometric optics, and the primary radiator 11 receives the radio wave efficiently. It cannot transmit radio waves. Conversely, when transmitting radio waves from the primary radiator 11, the shaded area 1
The radio waves radiated into the sub-reflector 1 are considered from geometrical optics.
It is not transmitted from the main reflecting mirror 9 due to the shielding of the signal. Therefore,
The efficiency of the antenna will decrease.

Furthermore, when attempting to use radio waves in a wider area as seen from the primary radiator 11 by bringing the primary radiator 11 closer to the sub-reflector 10, the primary radiator 11 itself becomes a shield in the radio wave path from the sub-reflector 10. As a result, efficiency decreases,
I can't get that close. .

This problem cannot be solved simply by modifying the mirror surface of the main and sub-reflectors.

As a means to solve the above problem, JP-A-52-1312
There is a conventional technique disclosed in Japanese Patent No. 03.

However, with this technology, the aperture diameter of the primary radiator must be smaller than that of the Cassegrain type or Gregorian type.
There is a problem that it is impossible to get close to the sub-reflector, and there is also a problem that it is complicated to obtain the mirror surface shape of the sub-reflector in order to improve the efficiency of the antenna.

The purpose of the present invention is to increase the efficiency of the antenna by making it possible to use radio waves that could not be used conventionally due to the shielding of the sub-reflector.
Another object of the present invention is to provide a microwave antenna that can use a small-diameter primary radiator by easily bringing the primary radiator close to the sub-reflector.

[Means for solving problems]

The above purpose is to place focal point 1 on the axis, focal points 2 and 2' at points other than on the axis, and to The mirror surface is constructed by combining a part of a parabola with focal point 2 and a part of a parabola with focal point 2', and the sub-reflecting mirror surface is a combination of a part of an ellipse with focal points 1 and 2, and the focal point. This is achieved by combining parts of an ellipse having focal points 1 and 2'.

[Effect]

When the microwave antenna according to the invention is viewed in axial cross-section, the combination of an on-axis focus 1 and an off-axis focus 2 or 2' constitutes two offset Gregoriano antennas.

That is, the cross section of one offset Gregorian antenna is formed by a part of the parabola with focal point 1 as the focal point and a part of the ellipse with focal points 1 and 2 as focal points, and similarly, the cross section of the parabola with focal point 1 and focal point 2' is The cross section of the offset Gregoriano antenna is formed by combining the part and the part of the ellipse.

The offset Gregorian antenna has the characteristics that the shielding of the sub-reflector can be eliminated and the primary radiator can be easily brought close to the sub-reflector. Since it has a shape,
It has the characteristics of the offset Gregorian antenna described above.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is an axial cross-sectional view of an embodiment of a microwave antenna according to the present invention, and FIG. 2 is a perspective view thereof.

In this embodiment, the microwave antenna has a main reflector 5.
3', a sub-reflector 4.4', and a primary radiator 5. Both the main reflection mirror @5, 3' and the sub-reflection mirror adit' are concave mirrors, and are rotationally symmetrical with respect to the axis 8. The focal point 1 is located on the axis 8. Focal point 2 and Focal point 2'
is located at a point other than on the axis 8, and is located at a point line-symmetrical to the parentheses axis 8.

The ellipse 6 is an ellipse having focal points at points 1 and 2, and the cross section of the sub-reflector 4 is formed from a part of this ellipse 6. The ellipse 7 is an ellipse having focal points at points 1 and 2', and the cross section of the sub-reflector 4' is formed partially upward of this ellipse 7.

On the other hand, the cross section of the main reflecting mirror 3 is made up of a part of a parabola with the focal point at the point 2, and from a geometric optics point of view, the light rays emitted from the focal point 2 are reflected by the main reflecting mirror 5 and are directed toward the axis 8. It has a geometric structure that moves in parallel to the direction. Similarly, the cross section of the main reflecting mirror 3' is composed of a part of a parabola with the focal point 2', and the light beam emitted from the focal point 2' is transmitted to the main reflecting mirror 3'.
It has a geometrical structure in which it is reflected by the axis 8 and travels in a direction parallel to the axis 8. Further, the primary radiator 5 is placed at a position where radio waves are emitted from the point 1 when viewed approximately.

Regarding radio wave radiation when using the above antenna configuration,
This will be explained in terms of geometrical optics.

During transmission, radio waves emitted from the focal point 1 are reflected by the sub-reflector 4 or 4' and are focused at the focal point 2 or 2' due to the geometrical properties of the ellipse. The radio waves focused on the focal point 2 or 2' are diffused again around these two points and reflected by the main reflection @5 or 3', and due to the geometrical properties of the parabola, the radio waves are parallel to the axis 8. I will move on.

In the above process, all the radio waves reflected by the sub-reflecting mirrors 4 and 4' are radiated from the main reflecting mirrors 6 and 3', so
Decrease in efficiency due to shielding of the sub-reflector can be suppressed as much as possible.

Conversely, during reception, radio waves traveling parallel to the axis 8 are reflected by the main reflecting mirror 3 or 6' at locations other than those blocked by the sub-reflectors 4 and 4'.

Depending on the nature of the parabola, it is focused at focal point 2 or 2'.

The radio waves focused at the focal point 2 or 2' are again diffused around these two points, reflected by the sub-reflector 4 or 4', and focused at the focal point 1 due to the elliptical nature.

In the above process, all the radio waves reflected by the main reflecting mirrors 6 and 6' are transmitted to the primary radiator 5 by the sub-reflecting mirrors 4 and 4', and the efficiency decreases due to the shielding of the sub-reflecting mirrors. can be suppressed as much as possible.

In this embodiment, an antenna having a geometrical structure has been described, but it is clear that the same effect can be obtained even when mirror surface correction is performed starting from the above-described structure.

〔Effect of the invention〕

As explained above, according to the present invention, when considering a microwave antenna in a cross-sectional view in the direction of the rotation axis, the focal point 1 is arranged on the axis, the focal points 2 and 2' are arranged off the axis, and the focal points 1 and 2' are arranged on the axis. ．． focus 1
By arranging the main reflector, the sub-reflector, and the primary radiator so that two offset Gregorian antennas are configured by the combination of The primary radiator can be moved closer to the sub-reflector.

[Brief explanation of the drawing]

FIG. 1 is an axial cross-sectional view of a microwave antenna according to an embodiment of the present invention, and FIG. 2 is a perspective view thereof. FIG. 3 shows an axial cross-sectional view of a conventional Cassegrain type microwave antenna. 1・・・・・・・・−・・Focus 2.2′・
......Focus 6.5'...
...Main reflector 4.4'...Sub reflector -] 5 -;' J83 Goyo 2 Fig. 53

Claims (1)

[Claims] 1. In a reflection-type microwave antenna composed of a primary radiator, a sub-reflector, and a main reflector, when the geometrical relationship of each component is expressed in an axial cross-sectional view, on the axis It has a focal point 1 and a focal point 2 and a focal point 2' at locations other than on the axis, and the main reflecting mirror is a part of a paraboloid having the focal point 2 as a focal point and a paraboloid having the focal point 2' as a focal point. The sub-reflector is constructed by combining a part of an ellipse with focal points 1 and 2 as focal points, and a part of an ellipse with focal points 1 and 2' as focal points. A microwave antenna featuring: