JPS6390902A - Double reflection mirror antenna - Google Patents

Abstract

PURPOSE:To realize a two-frequency band shared antenna without lowering the antenna efficiency, by placing a frequency selecting plate vertically to an antenna axis between a sub-reflection mirror and a primary radiator system, and attaching another primary radiator system to the center opening of the sub-reflection/mirror, as well. CONSTITUTION:The primary radiator system 41 is placed on an antenna axis being near a main reflection mirror 1. In addition to them, this antenna is provided with a frequency selecting plate 3 which has been placed vertically to the antenna axis 5 between a sub-reflection mirror 2 and the primary radiator system 41, and the primary radiator system 42 which is placed in the direction of the frequency selecting plate 3, in the center opening of the sub-reflection mirror 2 and transmits or receives a frequency being different from that of the primary reflector system 41. Therefore, an electromagnetic wave which has been radiated from the primary radiator system 41 transmits through the frequency selecting plate 3, reflected by the subreflection mirror 2, and radiated to the main reflection mirror 1. On the other hand, an electromagnetic wave which has been radiated from the primary radiator system 42 is reflected by the frequency selecting plate 3, reflected once again by the sub-reflection mirror 2, and radiated to the main reflection mirror 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-reflector antenna that can be used in three frequency bands.

[Conventional technology]

What is called a frequency selection board is used.

An example of an antenna that can be used for three frequency bands for demultiplexing using a frequency selection plate is an offset antenna shown in FIG. 2, for example. In the antenna shown in FIG. 2, a frequency selection plate 3 is placed outside the passage area of the reflected wave from the main reflecting mirror 1. For example, in the case of reception, using the frequency characteristics of the frequency selection board 3,
- Split into a transmitted wave heading towards the primary radiator system 41 and a reflected wave heading towards the primary radiator system 42. However, offset antennas are generally difficult to manufacture and have problems with radiation characteristics.

On the other hand, a double reflector antenna has one rotation symmetry.

Because they are easier to manufacture than offset antennas and have excellent axial symmetry in radiation characteristics, they are widely used in medium-sized and large-sized antennas. As a method of performing frequency demultiplexing using a frequency selection plate in a rotationally symmetric double-reflector antenna, a method as shown in FIG. 3, for example, has been proposed.

The antenna shown in FIG. 3 has a frequency selection plate 3 arranged diagonally with respect to the antenna axis 5 on the back side of the main reflector 1, and a primary radiator system 41 for the transmitted wave is placed on the antenna axis 5, and the primary 9 reflected waves are arranged on the back side of the main reflector 1. The radiator system 42 is arranged perpendicularly or obliquely to the antenna axis 5 to perform frequency separation.

[Problem that the invention seeks to solve]

However, this method requires a large space on the back side of the main reflecting mirror 1 to arrange the frequency selection plate 3 and the two primary radiator systems 41 and 42. (9) Since the focal length of the antenna must be increased, for example, if a horn antenna is used as a -order radiator, the axial length of the horn antenna must be increased, making the antenna as a whole larger and less economical. There is a drawback.

Furthermore, since the 1-frequency selection plate 3 generally has poorer characteristics such as cross-polarization characteristics for obliquely incident waves than in the case of perpendicular incidence, a special material is used for the 9-frequency selection plate. Alternatively, countermeasures such as improving manufacturing accuracy may be required, leading to an increase in price.

Another method has been proposed, as in the antenna shown in FIG. 4, in which the sub-reflector 2 is made of a frequency selection plate and the primary radiator system 41 for transmitted waves is placed on the back side of the sub-reflector 2. However, it is very difficult to manufacture a frequency selection plate that has a special curved surface and requires high surface precision, and is not very practical.

[Means for solving problems]

The present invention provides a multi-reflector antenna having a rotationally symmetrical main reflector and a sub-reflector, and a primary radiator system on the antenna axis. A selection plate is provided, and another primary radiator system is provided at a central opening of the sub-reflector facing the frequency selection plate.

[Effect]

With such a configuration, speaking of transmission.

The primary radiator system near the main reflector transmits through the frequency selection plate and irradiates the main reflector via the sub-reflector, and the primary radiator system installed on the sub-reflector emits light again after being reflected by the frequency selection plate. It is reflected by the sub-reflector and reaches the main reflector.

〔Example〕

The present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view of an embodiment of the present invention. In FIG. 1, the main reflector 1 and the sub-reflector 2 are rotationally symmetrical about the antenna axis 5. For convenience, the incoming and reflected waves are shown only in the upper half of the drawing. A primary radiator system 41 is placed on the antenna axis 5 near the main reflecting mirror 1. In addition to these, the antenna of the present invention includes a frequency selection plate 3 placed perpendicularly to the antenna axis 5 between the sub-reflector 2 and the primary radiator system 41, and a sub-reflector 2.
It has a primary radiator system 42 which is placed at the center opening of the center facing the frequency selection plate 3 and which transmits or receives a frequency different from that of the -order radiator system 41 . The frequency selection plate 3 transmits the frequency band transmitted or received by the primary radiator system 41 on the side of the main reflector 1, and reflects the frequency band transmitted or received by the primary radiator system 42 on the side of the sub-reflector 2. have characteristics.

The electromagnetic waves emitted from the -order radiator system 41 pass through the frequency selection plate 3, are reflected by the sub-reflector 2, and are irradiated onto the main reflector 1. On the other hand, the electromagnetic waves radiated from the -order radiator system 42 are reflected by the frequency selection plate 3, reflected once again by the sub-reflector 2, and irradiated onto the main reflector 1.

The path of electromagnetic waves in the case of transmission has been described above, but in the case of reception, the path in the opposite direction will be explained. That is, spatial demultiplexing of two frequency bands is possible using one frequency selection plate 3, and a triple-reflector antenna that can be used for three frequency bands can be realized by the configuration of the present invention.

In the antenna of the present invention, the 9 frequency selection plates 3 are connected to the antenna axis 5.
Since the electromagnetic waves are vertically installed and the electromagnetic waves are incident perpendicularly thereto, there is an advantage that cross-polarization characteristics or circular polarization characteristics are not deteriorated. In addition, there is no need to place all nine frequency selection plates and two primary radiator systems on the back side of the main reflector, and there is no need to increase the focal length of the antenna, so it is smaller than the antenna shown in Figure 3. It's functional. In addition, in the antenna of the present invention, the center of the sub-reflector 2 is an opening for the primary radiator system 42, and the -order radiator system 4
No unnecessary direct reflection waves to 1 occur.

Furthermore, since the position of the -order radiator system 42 only needs to be a mirror image of the primary radiator system 41 with respect to the frequency selection plate 3,
There is a high degree of freedom in the positions and sizes of the -order radiator systems 41 and 42 and the frequency selection plate 3. That is, there is an advantage that electrically optimal designs can be made independently of each other. In other words, the present invention utilizes the area of the sub-reflector that is not used in normal double-reflector antennas, and the configuration of the present invention makes it possible to realize a three-frequency band antenna without reducing antenna efficiency. . In addition, the antenna of the present invention has the sub-reflector 2 and the primary radiator 42 integrated, and is mechanically similar to a normal rotationally symmetric double reflector antenna, making full use of the advantages of the 9 rotationally symmetric double reflector antenna. This realizes an antenna that can share three frequency bands.

〔Effect of the invention〕

As explained above, the present invention is achieved by placing a frequency selection plate perpendicular to the antenna axis between the sub-reflector and the primary radiator system, and by attaching another primary radiator system to the central opening of the sub-reflector. , without reducing the antenna efficiency, and also V
A three-frequency band antenna can be realized without deteriorating antenna performance such as SWR characteristics, cross-polarization characteristics, or circular polarization. In addition, the structure is simple, and the antenna as a whole does not need to be enlarged, making it possible to realize a three-frequency band antenna while taking advantage of the advantages of a 9-rotation symmetric double-reflector antenna.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of an embodiment of an offset antenna proposed so far, and FIGS. 3 and 4 are respectively. FIG. 1 is a vertical cross-sectional view of an example of a rotationally symmetric double reflector antenna that has been proposed so far. DESCRIPTION OF SYMBOLS 1... Main reflecting mirror, 2... Sub-reflecting mirrors 1, 3... Frequency selection board, 41.42... -order radiator system, 5... Antenna axis. Chaos 1 Figure 5 - - Antenna axis 2 Figure

Claims (1)

[Claims] 1. In a double-reflector antenna having a rotationally symmetrical main reflector and sub-reflector and a primary radiator system on the antenna axis,
A frequency selection plate is provided between the sub-reflector and the primary radiator system perpendicular to the antenna axis, and another primary radiator system is provided at the center opening of the sub-reflector facing the frequency selection plate. A double reflector antenna featuring: