Patent Grant
9543659
The present invention relates to a reflector antenna device used for, for example, satellite communications.
As a satellite-mounted shaped beam antenna, a reflector antenna whose aperture shape, in which asperities are formed on a mirror surface, is a circular shape is generally used in order to make it possible to transmit and receive a beam according to a requested service area.
For recent satellite-mounted shaped beam antennas, there is an increasing demand for improvements in the gain, suppression of the isolation, etc. than ever before.
As a measure to meet this demand, for example, there can be provided a method of improving the degree of freedom for forming asperities on the mirror surface, and enlarging the circular aperture shape which the main reflector has.
However, because the size of an antenna which can be mounted in a satellite is limited from satellite mounting constraints due to the fairing of rockets, the degree of freedom of reflector shaping is limited.
Therefore, in order to make it possible to maximize the utilization of the aperture area under the satellite mounting constraints, it is effective to use a main reflector having a rectangular aperture shape in which the four corners of its circular aperture is enlarged as long as it can be mounted.
A main reflector having such a rectangular aperture shape is disclosed by, for example, the following nonpatent reference 1.
Because the conventional reflector antenna device is constructed as above, even if a main reflector having a rectangular aperture shape is used, the shape of the beam radiated from the primary radiator onto the main reflector is a circular shape (refer to
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a reflector antenna device that can improve the degree of freedom of reflector shaping without causing reduction in efficiency.
In accordance with the present invention, there is provided a reflector antenna device including: a main reflector that has a rectangular aperture shape; a primary radiator that radiates a circle-shaped beam; and a subreflector that converts the shape of the beam radiated by the primary radiator from the circular shape to a rectangular shape similar to the aperture shape of the main reflector and reflects the beam, and that radiates the beam having the rectangular shape onto the main reflector.
Because the reflector antenna device in accordance with the present invention is configured in such away as to include: the main reflector that has a rectangular aperture shape; the primary radiator that radiates a circle-shaped beam; and the subreflector that converts the shape of the beam radiated by the primary radiator from the circular shape to a rectangular shape similar to the aperture shape of the main reflector and reflects the beam, and that radiates the beam having the rectangular shape onto the main reflector, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency.
Hereafter, in order to explain this invention in greater detail, the preferred embodiments of the present invention will be described with reference to the accompanying drawings.
In
Referring to
A primary radiator 3 is a source of radio wave radiation that radiates a beam having a rectangular shape similar to the aperture shape 2 of the main reflector 1 onto the main reflector 1. The primary radiator 3 constructs a beam radiator.
The amplitude distribution 4 is the amplitude distribution of the beam radiated onto the main reflector 1 by the primary radiator 3.
Next, an operation will be explained.
The beam having a rectangular shape emitted from the primary radiator 3 is reflected by the main reflector 1, and the beam having the rectangular shape reflected by the main reflector 1 is radiated in a determined direction (a direction of a requested service area).
At this time, the amplitude distribution of the beam radiated onto the main reflector 1 turns into the one like the amplitude distribution 4 shown in
In the conventional reflector antenna device shown in
P1 to P12 and R1 in the horizontal axis of
Further, the vertical axis of
It has been recognized that the reflector antenna device in accordance with this Embodiment 1 increases in gain by 0.2 dB or more at each of the evaluation points P1 to P12 and R1, and also increases in isolation by about 1 dB at the evaluation point I1, as compared with the conventional reflector antenna device.
This means that the radiation of a beam having a shape similar to the aperture shape of the main reflector improves the degree of freedom of the determination of the asperities of the main reflector for forming the shaped beam, i.e., the degree of forming in the reflector shaping.
As can be seen from the above description, because the reflector antenna device in accordance with this Embodiment 1 is configured in such a way as to include the main reflector 1 that has a rectangular aperture shape 2, and the primary radiator 3 that radiates a beam having a rectangular shape similar to the aperture shape 2 of the main reflector 1 onto the main reflector 1, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency.
A multimode horn antenna 5 is a horn antenna in which a plurality of waveguide modes are combined (for example, a fundamental mode and a plurality of higher modes of a waveguide are combined), and is a primary radiator that is configured in such a way as to radiate a beam having a rectangular shape. The multimode horn antenna 5 constructs a beam radiator.
Although the example in which the fundamental mode and the plurality of higher modes of the waveguide are combined is shown, this is only an example and the shape of the waveguide and the combination of the modes are not limited to those of the example.
Although this Embodiment 2 is an embodiment in which the multimode horn antenna 5 is used as the primary radiator, abeam having a rectangular shape similar to the aperture shape 2 of a main reflector 1 can be radiated onto the main reflector 1 also in the case in which the multimode horn antenna 5 is used as the primary radiator, like in the case of above-mentioned Embodiment 1. Therefore, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency.
An active phased array antenna 6 is a primary radiator that includes an amplifier and a phase shifter for each antenna element, and is configured in such a way as to radiate a beam having a rectangular shape by properly adjusting the amplification amount of each amplifier and the phase amount of each phase shifter to optimize each excitation coefficient of the primary radiator. The active phased array antenna 6 constructs a beam radiator.
Although this Embodiment 3 is an embodiment in which the active phased array antenna 6 is used as the primary radiator, a beam having a rectangular shape similar to the aperture shape 2 of a main reflector 1 can be radiated onto the main reflector 1 also in the case in which the active phased array antenna 6 is used as the primary radiator, like in the case of above-mentioned Embodiment 1. Therefore, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency.
A subreflector 7 is a Cassegrain-type reflector which has a rectangular aperture shape and whose mirror surface is a hyperboloid of revolution.
A beam radiator is comprised of a multimode horn antenna 5 and the subreflector 7.
Although the example in which a beam having a rectangular shape emitted from the multimode horn antenna 5 is radiated directly onto the main reflector 1 is shown in above-mentioned Embodiment 2, a beam having a rectangular shape emitted from the multimode horn antenna 5 can be reflected by the subreflector 7 having a rectangular aperture shape, and the beam having the rectangular shape reflected by the subreflector 7 can be radiated onto the main reflector 1. In this case, the same advantage as that provided by above-mentioned Embodiment 2 can be provided.
A subreflector 8 is a Gregorian-type reflector which has a rectangular aperture shape and whose mirror surface is an ellipsoid of revolution.
A beam radiator is comprised of a multimode horn antenna 5 and the subreflector 8.
Although the example in which a beam having a rectangular shape emitted from the multimode horn antenna 5 is radiated directly onto the main reflector 1 is shown in above-mentioned Embodiment 2, a beam having a rectangular shape emitted from the multimode horn antenna 5 can be reflected by the subreflector 8 having a rectangular aperture shape, and the beam having the rectangular shape reflected by the subreflector 8 can be radiated onto the main reflector 1. In this case, the same advantage as that provided by above-mentioned Embodiment 2 can be provided.
A primary radiator 9 is a source of radio wave radiation that radiates a circle-shaped beam.
A subreflector 10 has a mirror surface on which asperities are formed in order to form a beam, and has a rectangular aperture shape.
Further, the mirror surface of the subreflector 10 is shaped in such a way as to, when reflecting the beam radiated by the primary radiator 9, convert the shape of the beam from the circular shape to a rectangular shape, and the beam having the rectangular shape is radiated onto a main reflector 1.
The subreflector 10 is a Cassegrain-type reflector whose mirror surface before the formation of asperities is a hyperboloid of revolution, and the asperities are formed by using, for example, a non-linear optimization method in such a way that a beam having a rectangular shape can be acquired.
A beam radiator is comprised of the primary radiator 9 and the subreflector 10.
Although the example in which a beam having a rectangular shape emitted from the multimode horn antenna 5 is reflected by the subreflector 7 having a rectangular aperture shape, and the beam having the rectangular shape reflected by the subreflector 7 is radiated onto the main reflector 1 is shown in above-mentioned Embodiment 4, a beam having a circular shape emitted from the primary radiator 9 can be reflected by the subreflector 10 having a rectangular aperture shape and the shape of the beam can be converted from the circular shape to a rectangular shape when reflected, so that the beam having the rectangular shape is radiated onto the main reflector 1.
Because a beam having a rectangular shape similar to the aperture shape 2 of the main reflector 1 can be radiated onto the main reflector 1 also in this case, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency, like in the case of above-mentioned Embodiment 4.
A subreflector 11 has a mirror surface on which asperities are formed in order to form a beam, and has a rectangular aperture shape.
Further, the mirror surface of the subreflector 11 is shaped in such a way as to, when reflecting the beam radiated by the primary radiator 9, convert the shape of the beam from the circular shape to a rectangular shape, and the beam having the rectangular shape is radiated onto a main reflector 1.
The subreflector 11 is a Gregorian-type reflector whose mirror surface before the formation of asperities is an ellipsoid of revolution, and the asperities are formed by using, for example, a non-linear optimization method in such a way that a beam having a rectangular shape can be acquired.
A beam radiator is comprised of the primary radiator 9 and the subreflector 11.
Although the example in which a beam having a rectangular shape emitted from the multimode horn antenna 5 is reflected by the subreflector 7 having a rectangular aperture shape, and the beam having the rectangular shape reflected by the subreflector 7 is radiated onto the main reflector 1 is shown in above-mentioned Embodiment 4, a beam having a circular shape emitted from the primary radiator 9 can be reflected by the subreflector 11 having a rectangular aperture shape and the shape of the beam can be converted from the circular shape to a rectangular shape when reflected, so that the beam having the rectangular shape is radiated onto the main reflector 1.
Because a beam having a rectangular shape similar to the aperture shape 2 of the main reflector 1 can be radiated onto the main reflector 1 also in this case, there is provided an advantage of being able to improve the degree of freedom of reflector shaping without causing reduction in efficiency, like in the case of above-mentioned Embodiment 4.
While the invention has been described in its preferred embodiments, it is to be understood that an arbitrary combination of two or more of the above-mentioned embodiments can be made, various changes can be made in an arbitrary component in accordance with any one of the above-mentioned embodiments, and an arbitrary component in accordance with any one of the above-mentioned embodiments can be omitted within the scope of the invention.
Because the reflector antenna device in accordance with the present invention includes the main reflector that has a rectangular aperture shape, and the beam radiator that radiates a beam having a rectangular shape similar to the aperture shape of the main reflector onto the main reflector, and can improve the degree of freedom of reflector shaping without causing reduction in efficiency, the reflector antenna device is suitable for use in satellite communications and so on.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-228862 | Oct 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/058996 | 3/27/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/061293 | 4/24/2014 | WO | A |
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| International Search Report; PCT/JP2013/058996; Jun. 25, 2013. |
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| M. Sanad et al.; “A Low Wind Load Lightweight Dual Cylindrical Reflector Antenna with a Novel Feed for Direct Broadcast Satellite TV Reception”; 2010 Loughborough Antenna & Propagation Conference; Nov. 8-9, 2010; pp. 285-288; Loughborough, UK. |
| Number | Date | Country | |
|---|---|---|---|
| 20150207237 A1 | Jul 2015 | US |
