JPH03286604A - Variable directivity antenna - Google Patents

Abstract

PURPOSE:To arrange required element antennas closely by providing plural feeding horns arranged at each focus of split mirror surfaces, variable phase shifters arranged to the feeding horns respectively, and a power synthesizer synthesizing outputs of the variable phase shifters. CONSTITUTION:A feeding horn 4 is arranged respectively to three foci of a split mirror surface reflecting mirror 2, a circular polarized wave generator P th the outputs of the three feeding horns 4 and a polarizer OMT is arranged to the output to separate clockwise and counterclockwise circular polarized waves. Variable phase shifters phi1, phi2, phi3 are connected for each split antenna to synthesize the outputs by a power combiner 10 and the result is led to a reception section 8.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a variable directional antenna.

More specifically, the present invention provides, for example, a variable directivity system that can change the directivity of a receiving antenna mounted on a broadcasting satellite in order to efficiently receive radio waves from small earth stations moving on the ground or on the sea. It concerns sexual antennae.

[Summary of the invention 1 The present invention relates to a variable directional antenna, in which the mirror surface of a parabolic reflector made of a paraboloid of revolution is divided into several parts, and the divided mirror surfaces are aligned perpendicularly to the rotation axis of the parabola. By moving parallel in the direction, a group of parabolic reflectors with multiple focal points close to each other and antenna beams all in the same direction is created, and a feeding horn is placed at each focus of this group of parabolic reflectors. By this, an array antenna equivalent to arranging antennas with large apertures at intervals much smaller than the size of the apertures was realized, and a variable phase shifter was connected to each output end of the feeding horn. Furthermore, this is a variable directivity antenna in which the directivity direction of the antenna can be changed by combining the respective outputs of the variable phase shifters using a power combiner.

[Prior Art 1] Conventionally, array antennas have been used to make the directivity of the antenna variable. That is, the horns or parabolas that are the element antennas of this array antenna are placed adjacent to each other, a phase shifter is connected to the output side of each element antenna, and the output of each phase shifter is combined with the power combiner of the element antenna. A structure is adopted in which the signals are combined in consideration of the phase and the combined output is guided to the receiver. The directivity direction of the array antenna is changed by appropriately changing the phase of each element antenna.

[Problem to be Solved by the Invention 1] Generally, the larger the maximum gain of the array antenna, the better. On the other hand, the maximum gain of an array antenna is when all 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 each element antenna.

If the number of element antennas is increased in this way, many phase shifters and waveguide circuits will be required for each element antenna, and the power combiner will also become complicated. undesirable from this point of view. Therefore,
In order to increase the maximum gain of the array antenna, the element antenna must be made larger to increase the gain of the element antenna alone.

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

For this reason, when an element antenna with a large gain is used, the element spacing inevitably becomes large, and when the array antenna is directed in the desired direction, a grating with high gain in many directions other than that direction is created. Lobes are generated, and all radio waves from these directions become sources of interference, degrading the performance of the array antenna.

Therefore, in view of the above points, 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 enable them to be arranged closely. It is in.

[Means for Solving the Problems j] The variable directional antenna according to the present invention includes a mirror surface of a paraboloid of revolution parabolic reflector divided into a plurality of parts, and a mirror surface of each of the divided mirrors of the parabolic reflector. a plurality of power feeding horns that are moved in parallel in a direction perpendicular to the rotation axis and placed at respective focal points of divided mirror surfaces produced by the parallel movement;
The present invention is characterized in that it includes a variable phase shifter disposed in each of the power feeding horns, and a power combiner that combines the outputs of each of the variable phase shifters.

[Operation j According to the present invention, a group of parabolic reflectors having a plurality of close focal points and whose antenna beams are all directed in the same direction is created, and a feeding horn is attached to each focus of this group of parabolic reflectors. This creates an array antenna equivalent to antennas with large apertures lined up at intervals much smaller than the aperture size, and a variable phase shifter is connected to each output end of the feeding horn. However, by further combining the respective outputs of the variable phase shifters using a power combiner, the directivity direction of the antenna can be changed.

[Example 1 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a simplified embodiment of a variable directivity antenna to which the present invention is applied. In this embodiment, three focal points F, .
A feeding horn 4 is placed at each of F, , F, a circularly polarized wave generator P is placed at the output of each of the three feeding horns 4, and a polarization demultiplexer is placed at the output of each circularly polarized wave generator P. By arranging the OMT, right-handed circularly polarized waves and left-handed circularly polarized waves are separated.

Although Figure 1 shows the case of receiving two orthogonal circularly polarized waves, the same configuration can also be used to receive linearly polarized waves, or to function as a transmitting antenna instead of a receiving antenna. can.

The right-handed or counter-clockwise polarized component is separated into each channel by the filter FIL (the figure shows an example of 3 channels, but the number of channels can be increased if necessary), and the separated channel (right-handed polarized component in the figure). (Only #1 channel is shown) for each variable phase shifter φ1. φ2. φ3 is connected, and the respective outputs are further combined by a power combiner (the figure shows an example configured with two magic tees) and guided to the receiving section.

The phase shifter φ1 shown in FIG. φ2. By changing φ3, the directivity of this antenna can be directed in any direction (the figure shows an example of #1 channel of the right-handed circularly polarized wave component).

In addition, the focal points of the split specular reflectors (the figure shows an example in which an offset parabola is divided into three) can be placed at extremely small intervals compared to the size of the mirror surface, as will be described later, so it is possible to Since there is no grating lobe that causes gain, and a mirror surface with a large area is used, a large gain can be expected from the split mirror surface that plays the role of an element antenna. Therefore, it is possible to easily create a variable directional antenna with a large gain. This can be achieved through configuration.

Next, the split specular reflecting mirror 2 will be explained.

First, in order to help understand the structure and operation of the divided mirror surface in this embodiment, FIG. 2 schematically shows the basic structure of a normal parabolic reflecting mirror, which is the original form of the divided mirror surface. Second
(a) shown in the figure is a side view of the parabola, and F
is the focus of the parabola. A power supply horn is placed here. (b) shown in FIG. 2 is a view of the parabolic reflecting mirror viewed from the front (the direction in which radio waves are incident or radiated), and shows the case of a circular aperture parabola. A focal point F is located at the center of the circle indicating the edge of the parabola, and the power supply horn is placed here. This figure shows the feeding horn viewed from behind.

FIG. 3 is a diagram showing how to make a split specular reflecting mirror in this embodiment, and shows a case in which 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 passes through FA, FB, and FC and is divided into three planes perpendicular to the plane of the paper. In other words, the parabolic reflector is divided into three parts, and the divided sub-mirror surfaces are d (=F, F =F, F =F3
If you move outward by F
I can do it.

FIG. 4 is a diagram explaining the above-mentioned division method more clearly, and the parabola is divided into three parts at the part marked as cut.

In FIG. 4, O indicates the intersection of the parabolic reflector and the parabolic rotation axis. OA, OB, QC in the diagram
Divide the parabolic reflector into three parts.

As shown in Fig. 3, each of the divided mirror surfaces is
,, in the direction of moving away from each other by FF2 or FF3,
Furthermore, if all of the mirrors are moved in a direction parallel to the plane of the paper, three divided mirror surfaces with diagonal lines shown in FIG. 3 are formed.

FIG. 5 shows in more detail how each divided mirror surface moves. In this figure, arrows indicate the direction of movement, and all three arrows in the figure are perpendicular to the rotation axis. By moving the original mirror surface in a direction perpendicular to the parabola rotation axis, the direction of the radio waves incident on or emitted from this mirror surface will be in the same direction as the original parabola (direction of the rotation axis). We need to focus on the points of agreement.

As is clear from FIG. 3, the focal points of the three-part parabolas (hatched portions) do not overlap, and the feeding horns can be placed at these focal points, respectively. FF shown in FIG. 3, FF2. The distance of FF3 is the distance required to arrange the power feeding horn.

The space 11i created by the movement of the divided mirror surfaces (between FIA' and FJ'' in Figure 3, and between F, B' and F, B'').

(between FsC' and F+C'') is the installation location for a metal fitting to support the split mirror surface, or is left as an air gap as an interface part with the satellite structure.Alternatively,
Either of the opposing divided mirror surfaces may be extended (each of the two opposing mirror surfaces may be extended at an appropriate ratio). In this case, a structure is created in which a step is formed at the joining portion of the divided mirror surfaces.

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

The present invention can be applied, for example, to a situation where it is determined by international agreement that two or more broadcasting satellites are placed at the same orbital position on a geostationary orbit, but far enough apart from each other to avoid collision, when viewed from the earth. It can be used as an antenna mounted on a broadcasting satellite of a 12GH 2-band broadcasting satellite system (in particular, a feeder link antenna mounted on a broadcasting satellite for receiving radio waves transmitted from an earth station).

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a variable directional antenna to which the present invention is applied. Figure 2 is the basic structure of a normal parabolic reflector used to explain the basic structure of the split specular reflector in this example. Fig. 3 is a diagram showing an example of the structure of the split specular reflecting mirror of this embodiment. Fig. 4 is a diagram showing how to divide the parabolic reflecting mirror, which is the original form of the split specular reflecting mirror of this embodiment. 5A and 5B are diagrams showing how to move the parabolic reflecting mirror, which is the original form of the split specular reflecting mirror of this embodiment, after being divided. 2... Divided specular reflector, 4... Feeding horn, 8... Receiving unit, lO... Power combiner, 20... Variable directivity antenna, [Left]... Left rotation component, [ Right]...Right-handed component, P...Circularly polarized wave generator, OMT...Polarization demultiplexer, FIL...Filter, φ...Phase shifter, Md...Magic T element , #l to #3...channels separated by filters.

Claims (1)

[Claims] 1) A mirror surface of a paraboloid of revolution type parabolic reflecting mirror divided into a plurality of parts, and each of the divided mirror surfaces being translated in a direction perpendicular to the rotation axis of the parabolic reflecting mirror, a plurality of feeding horns disposed at respective focal points of the divided mirror surfaces caused by the parallel movement; a variable phase shifter disposed in each of the feeding horns; and combining the outputs of each of the variable phase shifters. A variable directional antenna characterized by comprising a power combiner.