JP2994419B2 - Variable directional antenna - Google Patents

Description

The present invention relates to a variable directional antenna.

More specifically, the present invention provides, for example, a variable directional antenna capable of changing the directivity of a receiving antenna mounted on a broadcasting satellite in order to efficiently receive radio waves from a small earth station moving on the ground or on the sea. It relates to a directional antenna.

[Summary of the Invention] The present invention relates to a variable directional antenna, in which a mirror surface of a parabolic reflector made of a paraboloid of revolution is divided into several parts, and this divided mirror surface is perpendicular to the rotation axis of the parabola. To make a parabolic reflector group that has multiple focal points close to each other and that the antenna beam is all in the same direction by translating in the direction, and placing the feeding horn at each focal point of this parabolic reflector group By
An antenna with a large aperture is larger than the size of the aperture,
An array antenna equivalent to arranging at a much smaller interval is realized, a variable phase shifter is connected to each output terminal of the feed horn, and each output of the variable phase shifter is combined by a power combiner. This is a variable directional antenna in which the directional direction of the antenna can be changed.

[Prior Art] Conventionally, an array antenna has been used to change the directional direction of an antenna. That is, a horn or a parabola, which is an element antenna of this array antenna, is arranged adjacently, a phase shifter is connected to the output side of each element antenna, and the output of each phase shifter is connected to the element antenna by a power combiner. A structure is adopted in which the phases are taken into account and the combined output is guided to a receiver. The direction of the array antenna is changed by appropriately changing the phase of each element antenna.

[Problems to be Solved by the Invention] Generally, the larger the maximum gain of the array antenna, the better.
On the other hand, the maximum gain of the array antenna is obtained when all the element antennas are combined in the same phase, and is proportional to the gain of one element antenna and the number of element antennas. Therefore, in order to increase the gain of the array antenna, it is necessary to increase the number of element antennas or increase the gain of the element antenna alone.

When the number of element antennas is increased in this manner, many phase shifters and waveguide circuits are required for each element antenna, and the power combiner becomes complicated. Is not preferred. Therefore, to increase the maximum gain of the array antenna,
The element antenna must be enlarged to increase the gain of the element antenna alone.

However, in the conventional array antenna, the distance between the element antennas cannot be smaller than the distance determined by the size of the element antenna.

Therefore, when an element antenna having a large gain is used, the element spacing is inevitably increased, and when the directional direction of the array antenna is directed to a target direction, a grating lobe having a high gain in many directions other than that direction. And all radio waves from these directions become interference sources, deteriorating the performance of the array antenna.

Accordingly, an object of the present invention is to provide a variable directional antenna configured to increase the maximum gain of the entire antenna, reduce the number of required element antennas, and be arranged close to each other in view of the above points. It is in.

[Means for Solving the Problems] The variable directional antenna according to the present invention includes a plurality of divided parabolic parabolic reflector mirror surfaces, and each of the divided mirror surfaces is defined by the parabolic reflector mirror. A plurality of feed horns that are translated in a direction perpendicular to the rotation axis and are arranged at respective focal points of the divided mirror surfaces generated by the translation, and a variable phase shifter that is arranged in each of the feed horns; And a power combiner for combining the outputs of the variable phase shifters.

[Operation] According to the present invention, it has a plurality of close focal points, and
By creating a group of parabolic reflectors in which the antenna beams are all in the same direction, and placing the feeding horn at each focal point of this group of parabolic reflectors, an antenna with a large aperture can be made much larger than the size of the aperture. By realizing an array antenna equivalent to arranging at a small interval, connecting a variable phase shifter to each output terminal of the feed horn, and combining the outputs of the variable phase shifters with a power combiner ,
The directional direction of the antenna can be changed.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a simplified example of a variable directional antenna to which the present invention is applied. In the present embodiment, the three focal points F ₁ , F ₂ ,
Respectively feed horn 4 is disposed on the F _3, 3 pieces of arranged output circularly polarized wave generator P of each of the feed horn 4, distribution of the polarization separator OMT to the output of the circular polarizer P each By doing so, a right-handed circularly polarized wave and a left-handed circularly polarized wave are separated.

FIG. 1 shows a case where two orthogonal circularly polarized waves are received. However, a similar configuration can be used to receive linearly polarized waves or to function as a transmitting antenna instead of a receiving antenna. it can.

The right or left-handed polarization component is separated by a filter FIL for each channel (three channels are shown in the figure, but the number of channels can be increased as necessary), and the separated channels (right-hand rotation in the figure) The variable phase shifters φ ₁ , φ ₂ , φ ₃ are connected for each of the
Further, the outputs are combined by a power combiner (an example configured with two magic Ts is shown in the figure) and guided to a receiving unit.

By changing the phase shifters φ ₁ , φ ₂ , φ ₃ shown in FIG. ₁ , the directivity direction of the present antenna is directed to an arbitrary direction (in the figure, an example of the # 1 channel of the right-handed circularly polarized wave component is shown). Shown).

Further, as will be described later, the respective focal points of the split mirror reflector (in the figure, an example in which the offset parabola is divided into three) can be arranged at extremely small intervals compared to the size of the mirror surface. Since there is no generation of grating lobes that cause gain, and a mirror surface having a large area is used, a large gain can be expected from a split mirror surface that plays a role of an element antenna. It can be realized by the configuration.

 Next, the split mirror reflector 2 will be described.

First, in order to facilitate understanding of the structure and operation of the split mirror surface in this embodiment, FIG. 2 is a diagram schematically showing the basic structure of a normal parabolic reflecting mirror which is the original shape of the split mirror surface. (A) shown in FIG. 2 is a view of the parabola viewed from the side,
F is the focus of the parabola. The power supply horn is arranged here. (B) shown in FIG. 2 is a diagram of the parabolic reflector viewed from the front (in a direction in which a radio wave enters or emits), and shows a case of a circular aperture parabola. The focal point F is located at the center of the circle indicating the edge of the parabola, and the feeding horn is placed here. In this drawing, a state in which the power supply horn is viewed from behind is shown.

FIG. 3 is a diagram showing how to make a split mirror reflector in this embodiment, and shows a case where a parabola is divided into three equal parts. In FIG. 3, the circle ANBPCM indicates the edge of the original parabolic reflector. This parabolic reflector is F
It passes through A, FB, and FC, and is divided into three planes perpendicular to the paper. That is, the parabolic reflector is divided into three, and the divided sub-mirror surface is By moving it only outward, a three-divided mirror surface (hatched portion in the figure) is created.

FIG. 4 is a diagram for explaining the above dividing method more easily. The parabola is divided into three parts at the portions marked as cuts. In FIG. 4, 0 indicates the intersection between the parabolic reflector and the parabola rotation axis. The parabolic reflector is divided into three parts at the portions OA, OB, and OC in the figure.

As shown in FIG. 3, each of the divided mirror surfaces is FF
_By moving in a direction away from each other by ₁ , FF ₂ or FF ₃ and in a direction parallel to the plane of the paper, three divided mirror surfaces hatched in FIG. 3 are formed.

FIG. 5 shows in more detail how to move each of the divided mirror surfaces. In this figure, the arrows indicate the direction of movement,
All three arrows in the figure are orthogonal to the rotation axis. By moving the original mirror surface in the direction perpendicular to the parabola rotation axis, the direction of radio waves incident on or radiated from this mirror surface will be in the same direction as the original parabola before movement (the direction of the rotation axis). It is necessary to pay attention to the coincidence.

As is clear from FIG. 3, the focal points of each of the above-mentioned three-segmented parabola (shaded portion) do not overlap, and the feeding horn can be arranged at these focal points. Third
The distance between FF ₁ , FF ₂ , and FF ₃ shown in the figure is the distance required to arrange the power supply horn.

The gap created by the movement of the divided mirror surface (F _{1 in} FIG. 3)
Between A 'and F ₂ A ", between F ₂ B' and F ₃ B", between F ₃ C 'and F ₁ C ")
May be used as a place for installing a bracket for supporting the split mirror surface, or may be left as an air gap as an interface with the satellite structure. Alternatively, one of the opposing split mirror surfaces may be extended (both opposing mirror surfaces may be extended at an appropriate ratio, respectively). In this case, there is a structure in which a step is formed at the junction of the divided mirror surfaces.

[Effects of the Invention] As described above, according to the present invention, by arranging element antennas having a large gain close to each other, it is possible to have a large gain and to direct the direction of the antenna beam to an arbitrary direction. By reducing the number of required element antennas, it is possible to realize a variable directional antenna in which the number of components of the entire antenna system is reduced.

For example, the present invention relates to the case where two or so points that are far from each other so as not to collide with each other but are substantially in a geosynchronous orbit when viewed from the earth.
An antenna mounted on a broadcasting satellite of the 12GHz band broadcasting satellite system, which is determined by international agreements to arrange more than two broadcasting satellites (especially for receiving radio waves transmitted from earth stations, It can be used for a feeder link antenna mounted on a broadcast satellite.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a variable directional antenna to which the present invention is applied, and FIG. 2 is a diagram showing the basic structure of a normal parabolic reflector used to explain the basic structure of a split mirror reflector in this embodiment. FIG. 3 shows an example of the structure of the split mirror reflector of the present embodiment. FIG. 4 shows how the parabolic reflector, which is the prototype of the split mirror reflector of the present embodiment, is divided. FIG. 5 is a diagram showing how the parabolic reflector, which is the original of the split mirror reflector of the present embodiment, is moved after being divided. 2 split mirror reflector 4 feed horn 8 receiver 10 power combiner 20 variable directional antenna [left] left-hand component [right] right-hand Component P: Circularly polarized wave generator, OMT: Polarized splitter, FIL: Filter, φ: Phase shifter, MT: Magic T element, # 1 to # 3: Demultiplexed by filter Channel.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01Q 21/00 H01Q 19/17

Claims (1)

(57) [Claims] 1. A mirror surface of a plurality of divided parabolic parabolic reflectors, and each of the divided mirror surfaces is translated in a direction perpendicular to the rotation axis of the parabolic reflector. A plurality of power supply horns disposed at respective focal points of the divided mirror surfaces generated by the power supply horns; variable phase shifters disposed at each of the power supply horns; and a power combiner configured to combine the outputs of the respective variable phase shifters. A variable directional antenna, comprising: