JPH02209003A - Antenna system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna device used for satellite communication ground stations and radio astronomy.

[Conventional technology]

FIG. 3 shows, for example, the paper [Design of Dual-Refle
ctor Antennas 5m1th Arbit
rally phase and^n+ptitude
Distributions') IEEE Tran
s, A, P, V.

I Ap-12, pp403-408. July 19
FIG. 64 is an explanatory diagram of the conventional mirror-modified Cassegrain antenna shown in FIG.
) shows the amplitude 1-phase distribution at the aperture. In the figure, 11
is a normally curved surface, 1 is a mirror-treated main reflecting mirror, and
Reference numeral 2 designates a sub-reflector mirror-treated, which has the role of controlling the phase of the received wave, and has the role of controlling the amplitude of the transmitted and received waves. 3 indicates a primary radiator (horn), and 41.42 indicates a light ray path emitted from the primary radiator until it reaches the antenna aperture. Further, 5 indicates the amplitude distribution at the aperture, and 6 indicates the phase distribution at the aperture.

Next, the operation will be explained.

The light ray 41 emitted from the focal point F of the horn 3 is reflected at the focal point F on the sub-reflector 2.
3 points, reflected at point B1 on the main reflector, A1 on the aperture surface
leading to. On the other hand, the ray 42 similarly points to C1 and B! It reaches At via the point. At this time, as is well known (please refer to the above-mentioned literature), the main and sub-reflecting mirrors are mirror-modified from normal parabolic mirrors and hyperboloid mirrors, respectively, under the following three conditions. That is, (1) Snell's law (
ii) Law of conservation of energy (i ii) Law of conservation of optical path length According to this mirror modification condition, the amplitude on the aperture surface.

The phase can be designed to any value. In Figure 3(b), the amplitude/
Both the phase and the diagram illustrate a state of uniform distribution. To briefly describe this modification method, the amplitude of the spray pattern from the horn (primary radiator) is controlled by the sub-reflector so that it becomes uniformly distributed at the main reflector aperture. In other words, as shown in Figure 3,
The density of light beams toward the periphery of the main reflector is increased. Further, the phase is controlled by the main reflecting mirror so that the optical path length from the phase center F of the primary radiator to the main reflecting mirror aperture is constant.

[Problem to be solved by the invention]

Since the conventional axially symmetrical mirror-finished antenna is constructed as described above, there is a problem in that a normal parabolic mirror cannot be used as the main reflecting mirror. Furthermore, even if the antenna diameter is the same, it is necessary to change the coordinates of the main reflecting mirror for each desired amplitude distribution.

For this reason, for example, if the main reflecting mirror is manufactured by press processing, and if the mirror surface is modified, a mold is required depending on the modification expansion ratio even for antennas of the same size, which has the drawback of extremely high manufacturing costs. . Especially for ground station antennas,
Even if the same aperture distribution is given over the frequency ranges of the C band, Ku band, and Ka band, it is difficult to obtain the same mirror surface shape.

This invention was made to solve the problems of the conventional ones as described above, and it is possible to use a normal rotationally symmetrical parabolic mirror as the main reflecting mirror, making it possible to standardize antennas. The aim is to obtain an antenna device that can.

[Means to solve the problem]

In the antenna device according to the present invention, the main reflecting mirror is a paraboloid of revolution, and the sub-reflecting mirror has a phase so that a desired amplitude 9-phase distribution is obtained on the antenna aperture surface with the sub-reflecting mirror and the primary reflecting mirror. The primary radiator is configured to control the amplitude of the primary radiator.

[Effect]

In this invention, since the apparatus is configured as described above, the required antenna characteristics can be achieved without mirror-finishing the main reflecting mirror.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an antenna device according to an embodiment of the present invention,
In the figure, the same reference numerals as in FIG. 3 indicate the same parts. 111 is a main reflecting mirror with a normal rotationally symmetrical parabolic curved surface, 21 is a mirror-treated sub-reflecting mirror, which has the role of controlling the phase, and 31 is an amplitude-controlled primary radiator, which controls the amplitude. It has the role of

Moreover, FIG. 2 shows the ray path of the antenna device of FIG.
It reaches the aperture surface via Bt and At. Here the ray Cs B
t, CtBt both come out from the focal point F3 of the main reflecting mirror.

Conceptually speaking about amplitude control, the spray pattern from the sub-reflector to the main reflector is determined by the space attenuation rate (Space attenuation rate) shown in Figure 4.
Attenuation Factor; hereinafter S, A
, F) It is necessary to obtain a distribution from the primary radiator corresponding to the angle θ from the main reflector focal point Fs to the main reflector so as to correct S−A, P ” 2 / (1+cos θ). Figure 5 shows the characteristics required for the primary radiator.

Figures 6(a), (C), and (e) are examples of primary radiators that provide a distribution where the electric field strength becomes stronger in the periphery.
There is. FIG. 6(a) uses a lens, and the amplitude of the spray onto the sub-reflector is controlled by the lens 7.

FIG. 2C shows an example in which a ring-focal type double reflecting mirror 8 is used as the primary radiator. The figure (e) shows an array-fed primary radiator using a variable phase shifter 9, a variable attenuator 10, and a radiator 11.

The radiation patterns for each of these systems are shown on the right side of FIG.

In the case of the lens shape shown in figure (a), lens 7 not only functions as a wavefront converter, but also functions to make the radial distribution of light rays darker as it goes greener by using it as a modification lens as shown in the figure. do.

In the case of the ring focal double reflector type shown in the same figure (C), the double reflector 8
By applying the mirror surface modification method to the auxiliary reflecting mirror 81 and providing the auxiliary reflecting mirror 82 with a phase control function, it is possible to provide the desired amplitude and phase distribution.・A primary radiator with a phase pattern can be realized.

In the case of the array feeding type (axis in the same figure), feeding point 1 of the primary radiator
A primary radiator having a desired amplitude and phase pattern can be realized by applying the input from 2 to each radiating element 21 with a desired amplitude and phase distribution through a series of variable phase shifters 9 and variable attenuators 10. Note that the mirror surface modification method for the above-mentioned double reflection mirror can be the same as the mirror surface modification method for a normal rotationally symmetric double reflection mirror.

Regarding this point, for example, the document "Transactions of the Institute of Electronics, Information and Communication Engineers J B, Vol. J71-8. NILLl, 1) p1
213-12161988-11.

In this way, according to this embodiment, by combining the primary radiator for amplitude control and the sub-reflector for phase control, the required antenna characteristics, such as high gain, can be achieved without mirror-finishing the main reflector. It is possible to obtain a uniform distribution or a tapered distribution that can realize low siderope characteristics. Therefore, the main reflecting mirror can be standardized, economical, and highly accurate, so that the antenna device can be made more economical.

In the above embodiment, FIG. 6(C) is a modification of the offset Gregorian type, but the offset Cassegrain type as shown in FIG. 7 also provides the same effect as the above embodiment. In other words, the central ray from the horn 32 is reflected by the auxiliary reflecting mirror 81 forming a part of the offset Cassegrain, and enters another auxiliary reflecting mirror 82 as if it had come out from the focal point f, and then enters the auxiliary reflecting mirror 82. It becomes a ray of light heading towards. In addition, the 8th
The figure schematically shows a Cassegrain antenna using the primary radiator shown in FIG. 7.

〔Effect of the invention〕

As described above, according to the antenna device according to the present invention,
By controlling the amplitude with the primary radiator and controlling the phase with the sub-reflector, the antenna is configured to achieve the desired antenna characteristics without having to modify the mirror surface of the main reflector.
The main reflector can be standardized and a highly accurate one can be obtained economically.

[Brief explanation of the drawing]

FIG. 1 is a basic characteristic diagram of an antenna device according to an embodiment of the present invention, FIG. 2 is a ray path diagram of the antenna device of FIG. 1,
Figure 3 is a basic characteristic diagram of a conventional antenna device, and Figure 4 is a diagram of the basic characteristics of a conventional antenna device.
An explanatory diagram showing the pace attenuation factor, FIG. 5 is a diagram showing the required amplitude/phase pattern of the primary radiator of the present invention, FIG. 6 is a diagram showing embodiments of various primary radiators of the present invention, and FIG. FIG. 8 is a diagram showing an offset Cassegrain type ring-focal double-reflection primary radiator, and FIG. 8 is a diagram showing an embodiment of the present invention using FIG. 7. In the figure, 1 is a modified mirror surface, 2.21 is a sub-reflector, and 3.
31 is the primary radiator, 41.42 is the ray path, 5 is the amplitude,
6 is a phase, 7 is a lens, 8 is a double reflecting mirror, and 111 is a main reflecting mirror which usually has a curved surface. Fig. 1 Fig. 3 Fig.
,A,F diagram

Claims (1)

[Claims] (1) In an axially symmetric Cassegrain or Gregorian antenna device, there is a main reflector consisting of a normal rotating parabolic reflector, a primary radiator for amplitude control of transmitted and received waves, and phase control of transmitted and received waves. 1. An antenna device comprising: a sub-reflector for the primary radiator and a sub-reflector for obtaining a desired aperture distribution by modifying the primary radiator and the sub-reflector.