JP2825907B2 - Shaped beam antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is mounted on a broadcast satellite or the like, has a radiation pattern adapted to the shape of a service area, and has one horn and two horns.
The present invention relates to a shaped beam antenna for modifying a mirror surface of an antenna composed of a plurality of reflectors.

(Summary of the Invention) The present invention provides an antenna composed of one feed horn and two reflectors, and independently controls the aperture amplitude and phase distribution of the main reflector under the condition that the gain in the far field is a constraint. By optimizing and modifying the mirror surfaces of the main and sub reflectors, the optimized aperture distribution is realized,
This is to obtain a shaped beam having a required cross-sectional shape.

(Prior art) Conventionally, techniques for obtaining a shaped beam by a reflector antenna include, for example, "mirror-modified double reflector antenna,
No. 63-44208 ”, a method of obtaining an aperture amplitude / phase distribution using a virtual multi-horn and modifying two reflecting mirrors to realize the aperture distribution, and“ Synthesis of shaped-beam reflector antena patter
ns, J. Bergmann, RC Brown, PJB Clarricoats, H. Zhou, IEE Proceedings, Vol. 135, Pt. H, N
o.1, February 1988, pp. 48-53 ",
There is a method in which the shapes of two reflecting mirrors are expressed by a series, and a modified mirror surface is obtained by optimizing the undetermined coefficient of the series so as to minimize the sum of squares of the difference between the target gain and the antenna gain in the far field. is there.

Or "A Method for Producing a Shaped contour
Radiation Pattern Using a Single Shaped Reflector
and a Single feel, A, R, Cherrettee, S..W.Lee, RJAco
sta, IEEI Trans.Antennas & Propag., Vol.37, No.6, June.
1989, pp. 698-706 ", the sum of squares of the difference between the target gain and the antenna gain in the far field is minimum for the amplitude distribution given by the horn using one reflector. There is a method of obtaining a phase distribution that satisfies the following condition, and modifying the reflecting mirror so as to realize the phase distribution.

(Problems to be Solved by the Invention) In the conventional method using the virtual multi-horn, there is a problem that an abrupt step occurs in the main reflecting mirror, and a radiation pattern changes due to antenna fabrication or thermal distortion. Further, in the mirror surface modification of one reflecting mirror, since only the phase distribution is controlled, there is a limit in beam shaping.

The present invention has been made in view of the above points, and effectively solves the problems of the related art.
The amplitude distribution is also controlled to obtain a shaped beam antenna that covers with higher gain in accordance with the shape of the required service area, and to provide a shaped beam antenna having a smooth shape by eliminating the steps of the main reflecting mirror surface. Aim.

(Means for Solving the Problems) In order to achieve such an object, the present invention relates to a shaped beam antenna having a feed horn, a sub-reflecting mirror, and a main reflecting mirror sequentially provided. The shape of the mirror surface of the main reflecting mirror and the sub-reflecting mirror is modified according to the shape, and the amplitude distribution and the phase distribution on the main reflecting mirror according to the cross-sectional shape of the shaped beam have the target gain and the antenna gain in the far field. The mirror surface is modified so that the sum of squares of the difference becomes equal to the amplitude distribution and the phase distribution that minimize the difference.

(Operation) By such technical means, the present invention provides an aperture plane amplitude and a phase distribution of a main reflector under the condition that a gain in a far field of an antenna composed of one feed horn and two reflectors is a constraint. Are independently optimized, and the obtained aperture distribution is realized by modifying the mirrors of the main width reflecting mirrors, and a shaped beam having a required cross-sectional shape is obtained.

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

Fig. 1 shows a map of Japan and a gain constraint point as viewed from a satellite in a geosynchronous orbit of 110 ° east diameter. 1 is a gain constraint point in the far field, 2 is a map of Japan viewed from a geosynchronous orbit of 110 degrees east,
The constraint point 1 of the gain is overwritten on this Japan map 2, and in this embodiment, 103 constraint points are provided.

FIG. 2 is a schematic configuration diagram of an embodiment of the shaped beam antenna according to the present invention. The shaped beam antenna 10 includes a feed horn 3, a sub-reflector 4, and a main reflector 5. Reference numeral 6 denotes a locus of a radio wave radiated from the feeding horn 3. In order to obtain the phase distribution on the opening surface of the main reflecting mirror 5,
Assuming that the amplitude distribution is uniformly distributed, the phase distribution is optimized so that the sum of squares of the difference between the target gain and the antenna gain at the far-field constraint point 1 is minimized. At this time, in order to avoid a sudden change in the phase, in the process of optimizing the phase distribution, a limit is set so that the phase difference between adjacent ones of the aperture lattice points does not exceed a required value.

FIG. 3 shows a phase distribution diagram obtained at the opening surface of the main reflecting mirror in FIG. In this embodiment, the phase distribution is restricted so that the phase difference between adjacent aperture lattice points does not exceed 89 degrees.

FIG. 4 shows an amplitude distribution diagram of the aperture surface of the main reflecting mirror.
In order to determine the amplitude distribution on the opening surface of the main reflecting mirror 5, the phase distribution determined as described above is fixed, and the sum of squares of the difference between the target gain and the antenna gain at the far-field constraint point 1 is calculated as , The amplitude distribution is optimized to be the minimum value. The magnitude of the amplitude in FIG. 4 is a relative value and is shown in dB.

FIG. 5 shows a radiation pattern obtained by combining the phase distribution of FIG. 3 and the amplitude distribution of FIG. When the diameter of the opening surface of the main reflector 5 is 2.3m (Fig. 2) and the frequency is 12GHz, the radiation pattern is an absolute gain in dBi unit and is superimposed on the Japanese map 2 viewed from a geosynchronous orbit of 110 ° east diameter. It is written. The shaped beam antenna 10 includes a feed horn 3 having one phase distribution and one amplitude distribution on the aperture surface of the optimized main reflecting mirror 5.
And the surface modification of the main and sub-reflecting mirrors 4 and 5. That is, the sub-reflector 4 is modified to convert the concentric radiation beam determined by the feed horn 3 into the amplitude distribution previously determined, and then the aperture of the main reflector 5 is modified. , The phase is adjusted to realize the phase distribution previously obtained.

(Effects of the Invention) As described above, the shaped beam antenna of the present invention uses the main reflector with the gain in the far field of the antenna composed of one feed horn and two reflectors as a constraint. The aperture plane amplitude and phase distribution are independently optimized, and the obtained aperture plane distribution is realized by modifying the surface of the two main and sub-reflecting mirrors to obtain a shaped beam having a required cross-sectional shape. The problem is effectively solved, and a radiation pattern in which the required area is covered with higher gain is obtained as compared with the conventional mirror-shaped shaped beam antenna. By adjusting not only the distribution but also the amplitude distribution, it is possible to obtain a shaped beam having a complicated shape, to eliminate a step on the main reflecting mirror surface, and to obtain a smooth shape.

[Brief description of the drawings]

1 is a map of Japan and a gain constraint point as viewed from a satellite in a geosynchronous orbit of 110 ° east diameter, FIG. 2 is a schematic configuration diagram of an embodiment of a shaped beam antenna according to the present invention, and FIG. 3 is FIG. 4, the phase distribution diagram obtained at the main reflecting mirror aperture surface, FIG. 4 is also the amplitude distribution diagram of the main reflecting mirror aperture surface, and FIG. 5 is obtained by combining the phase distribution of FIG. 3 and the amplitude distribution of FIG. FIG. 1 Gain restriction point 2 Map of Japan 3 Feeding horn 4 Sub-reflector 5 Main reflector 6 Radio track 10 Shaped beam antenna

Claims (1)

(57) [Claims] 1. A shaped beam antenna having a power feeding horn, a sub-reflecting mirror and a main reflecting mirror sequentially provided, wherein the shapes of the mirror surfaces of the main reflecting mirror and the sub-reflecting mirror are modified in accordance with the required cross-sectional shape of the shaped beam. The amplitude distribution and the phase distribution on the main reflecting mirror according to the cross-sectional shape of the shaped beam are equal to the amplitude distribution and the phase distribution at which the sum of squares of the difference between the target gain and the antenna gain in the far field is minimized. A shaped beam antenna characterized by modifying the mirror surface.