JPS6048603A - Antenna system - Google Patents

Abstract

PURPOSE:To narrow the beam distance by arranging a main reflection mirror and a sub-reflection mirror symmetrically around a turning center axis and arranging a horn apart from the turning center axis in comparison with the sub-reflection mirror. CONSTITUTION:A radio wave radiated from the horn 1 is irradiated to the sub- reflection mirror 7, is reflected in the direction of the main reflection mirror 3 and goes to a propagating direction 5 of the radio wave. Similarly, the radio wave from a horn 1' goes to the sub-reflection mirror 7 and the main reflection mirror 3 and goes toward the propagating direction 5' of the radio wave. Since the main reflection mirror 3 and the sub-reflection mirror 7 are arranged symmetrically to the turning center axis 4, when the horn 1 is arranged symmetrically around the turning center axis 4 to the horn 1', the radio wave from the horn 1 and the radio wave from the horn 1' behave the same operation except the final propagating direction. Since the horn is placed apart from the turning center axis 4 in comparison with the sub-reflection mirror 7, the horn is arranged easily by keeping the angle from the turning center axis 4 to a constant value, and the beam distance is narrowed by arranging the horn approached nearly to be contacted conversely.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a multiple beam antenna that can independently radiate multiple beams from one antenna, and for example, when communicating with multiple satellites as an earth station antenna for satellite communications. The present invention relates to an aperture antenna used for.

(Background Art) Conventionally, various types of antennas that radiate a plurality of beams corresponding to the primary radiation system from a single main reflecting mirror surface have been considered depending on the purpose. On the other hand, a geokin station antenna for satellite communication is an antenna that allows the spacing between each beam to be wider than the beam width of each individual beam, or in other words, when focusing on a certain root beam, it is possible to scan the beam over a wide angle. There is a need for an antenna whose characteristics do not deteriorate, and an antenna called a torus antenna, which has a structure that is axially symmetrical with respect to an axis perpendicular to the plane where the satellites are lined up, is considered effective. FIG. 1 shows the configuration of a conventional torus antenna. 1 and 1' are horns used as primary radiation systems, 2 and 2 are sub-reflectors that reflect radio waves from horns 1 and 1', respectively, and 3 is a main reflector that is commonly used for radio waves from horns 1 and 1'. , 4 indicates the central axis of rotation of the main reflecting mirror 30, and 5 and DA indicate the traveling directions of radio waves corresponding to the horns 1 and 1', respectively. Reference numeral 6 denotes the generatrix of the main reflecting mirror, which is approximately a parabola. 2 and moth are arranged outside the path of the radio waves emitted from the main reflecting mirror so as not to obstruct the path of the radio waves. The operation of this antenna will be explained using transmission as an example. Radio waves emitted from the horn 1 hit the sub-reflector 2 and are reflected in the direction of the main reflector 3. Here, the sub-reflector 2 has been mirror-finished, and functions not only to simply reflect the direction of propagation of radio waves, but also to cancel phase distortion that occurs because the main reflector is a torus mirror. The radio waves traveling from the sub-reflector 2 to the main reflector 3 are reflected by the main reflector 3 and are directed in the radio wave traveling direction 5. Similarly, the radio waves emitted from the horn 1' are sent to the sub-reflector 3 and the main reflector 3.
When it hits, it heads in the direction of the radio waves. Here, paying attention to the fact that the main reflecting mirror 3 is rotationally symmetrical with respect to the rotation center axis 4, the combination of the horn 1 and the sub-reflector 2 is rotationally symmetrical with respect to the rotation center axis 4. It is clear that if they are arranged rotationally symmetrically, the radio waves emitted from the horn 1 and the radio waves emitted from the horn 1' operate in the same way except that their final traveling directions are different. Therefore, if the main reflector is sufficiently large, even if multiple beams are arranged with a wide beam spacing compared to the beam width,
It is possible to construct an antenna without deterioration of the characteristics of each beam. This is the principle of a torus antenna. However,
A practical requirement is not simply that the beams be spaced widely apart. If the satellites are placed close together and the viewing angle of each satellite from the ground is small,
Even if the beam spacing is large compared to the beam width, a situation may arise where the beams must be arranged at narrow intervals of several degrees in terms of absolute angles. Conventional torus antennas have drawbacks in such cases. In other words, how close the beam spacing can be made depends on how narrow the angle between each sub-reflector seen from the rotation center axis can be.To narrow the beam spacing, it is necessary to place the sub-reflectors close together. Must. However, since a sub-reflector of an appropriate size is used exclusively for each beam, even if you try to narrow the beam spacing, the multiple sub-reflectors will collide with each other, resulting in
There was a drawback that the beam spacing could not be narrowed beyond a certain level. Such a problem depends on how the diameter of the sub-reflecting mirror is selected, but generally occurs when the beam spacing is set to 5 degrees or less.

(Objective of the Invention) The present invention aims to improve the above-mentioned drawbacks, and its characteristics include a main reflecting mirror, a sub-reflecting mirror, and a primary radiation system that irradiates radio waves to the sub-reflecting mirror. Using a torus mirror surface obtained by rotating a generatrix consisting of a substantially parabola around an axis located in front of the main reflector and approximately perpendicular to the direction of propagation of radio waves emitted from the main reflector, the sub-reflector In a torus antenna in which a mirror is placed outside the path of radio waves emitted from the main reflector, a torus mirror surface is used as the shape of the sub-reflector, and the rotation center axis of the torus mirror surface forming the main reflector is aligned with the sub-reflector. The antenna device is arranged such that the center axis of rotation of the l·-las mirror surface to be formed coincides with the center axis of rotation, and the -order radiation system is placed farther from the center axis of rotation than the sub-reflector.

The present invention will now be described in detail based on the drawings.

(Structure and operation of the invention) FIG. 2 shows an embodiment of the present invention, in which 7 is a sub-reflector commonly used for the radio waves emitted from the horns 1 and 1', and its mirror surface shape is the main one. Like the reflector, it has a torus mirror surface. That is, it is made of a curved surface obtained by rotating the generating line 8 of the sub-reflecting mirror around the rotation center axis 4 like the main reflecting mirror. The operation of this antenna will be explained using transmission as an example. The radio wave emitted from the horn 1 hits the sub-reflector 7, is reflected in the direction of the main reflector 3, is further reflected by the main reflector 3, and heads in the radio wave traveling direction 5. Similarly, the radio waves emitted from the horn 1' also hit the sub-reflector 7 and the main reflector 3, and are directed in the direction of propagation of the radio waves. Here, paying attention to the fact that both the main reflecting mirror 3 and the sub-reflecting mirror 7 are rotationally symmetrical about the rotational center axis 4, the horn 1 is arranged rotationally symmetrically about the rotational center axis 4 with respect to the horn l'. It is clear that the radio waves emitted from the horn 1 and the radio waves emitted from the horn 11 operate in the same way except that their final traveling directions are different.

Therefore, it is understood that the present invention operates without characteristic deterioration for beam scanning over a wide angle. In the present invention, unlike conventional torus antennas, a sub-reflector is commonly used, and it is understood that the limit of the beam spacing between each beam is determined by whether or not the horns collide. However, the horn can be placed farther from the rotation center axis than the sub-reflector.

Therefore, if the angle from the rotation center axis is constant, the arrangement of the horns becomes easier, and conversely, if the horns are brought close together until they touch, the beam spacing can be narrowed.

Although two beams have been described above as an example to simplify the explanation, the number of beams may be three or more. To increase the number of beams, simply increase the number of horns.

In the present invention, it is possible to use not only a parabola as the generatrix of the main reflecting mirror and a quadratic curve such as a hyperbola or an ellipse as the generatrix of the sub-reflector, but also a combination of curves modified according to the purpose. can. In particular, when scanning a beam for the purpose of tracking positional fluctuations of a satellite in a plane perpendicular to the plane where the beams are lined up, it is difficult to use a cross-sectional curve of a reflector called a bifocal reflector. This is effective in reducing the decrease in gain associated with this. Furthermore, using a cross-sectional curve of a highly efficient modified mirror surface as a generating line is effective in improving antenna efficiency. A bifocal reflector is capable of focusing a beam without phase distortion at each focal position, and various design methods have been studied, and any of them may be used. Furthermore, a design method for the cross-sectional curve of a highly efficient modified mirror surface has been established, and can be easily designed by engineers in the field.

FIG. 3 is a perspective view showing a primary radiation system comprising a horn 1 and a focusing reflector 9, which is an embodiment of the present invention. The -order radiation system is used in place of horn 1 or 1' in FIG. Here, 9 is a focusing reflector for canceling the phase distortion generated in the main reflector 3 and the sub-reflector 7. By using the focusing reflector 9, phase distortion can be eliminated and antenna aperture efficiency can be increased. A lens may be used instead of the focusing mirror 9. The design of these focusing mirrors 9 or lenses can be easily performed by using a conditional expression called a constant optical path length condition.

(Effects of the Invention) As explained above, according to the present invention, it is possible to narrow the beam spacing of an antenna that outputs multiple beams from one main reflecting mirror, so if this is used as an earth station antenna for satellite communication, the satellite position Since only one antenna is required even if the antennas are close to each other, it can contribute to making the system more economical.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional torus antenna, FIG. 2 is a perspective view showing an embodiment of the present invention, and FIG. 3 is a perspective view showing a primary radiation system of an embodiment of the present invention. 1.11...Horn 2,2'...Sub-reflector 3...
...Main reflecting mirror 4 ...Rotation center axis 5.5'
... Direction of radio wave travel 6 ... Generatrix of main reflector 7 ... Sub-reflector 8 ... Generatrix of sub-reflector 9 ... Focused reflection mirror

Claims (4)

[Claims] (1) Consisting of a main reflecting mirror, a sub-reflecting mirror, and a primary radiation system that irradiates radio waves to the sub-reflecting mirror, the radio waves radiated from the main reflecting mirror progress along a generatrix that is approximately a parabola as the mirror surface shape of the main reflecting mirror. In a torus antenna that uses a torus mirror surface obtained by rotating around an axis located in front of the main reflector and substantially perpendicular to the direction, the sub reflector is placed outside the path of radio waves radiated from the main reflector. A torus mirror surface is used as the reflecting mirror shape, and the center axis of rotation of the torus mirror surface forming the main reflecting mirror is made to coincide with the center axis of rotation of the torus mirror surface forming the sub reflecting mirror. An antenna device characterized by being placed farther from the rotation center axis than a mirror. (2) A claim characterized in that the curved shapes of the main reflector and the sub-reflector, which can be seen as the cross-sectional curve of the bifocal antenna mirror surface, are used as the generatrix of the torus mirror surface forming the main reflector and the sub-reflector, respectively. The antenna device according to item 1. (3) The scope of the patent characterized in that the curved shapes of the main reflecting mirror and the sub-reflecting mirror, which can be seen as the cross-sectional curves of the highly efficient modified mirror surfaces, are used as the generatrix of the torus mirror surface forming the main reflecting mirror and the sub-reflecting mirror, respectively. The antenna device according to item 1. (4) A primary radiation system comprising at least one reflecting mirror or lens whose surface has been mirror-finished so as to cancel phase distortion caused by the main reflecting mirror and the sub-reflecting mirror. The antenna device according to any one of Items 1 to 3.