JPH0461403A - Offset type antenna - Google Patents

Abstract

PURPOSE:To reduce the cost of the antenna, to attain effective utilization of a space and to make the antenna compact by replacing an auxiliary reflecting mirror whose mirror surface is to be corrected with a correction dielectric lens. CONSTITUTION:The antenna consists of a main reflecting mirror 1 whose mirror surface is not corrected, a sub reflecting mirror 2 whose mirror surface is corrected to control the amplitude distribution in aperture distributions 6, 7, a primary radiator 3, and a correction dielectric lens 4 placed in the vicinity of the focus of the main reflecting mirror. The phase quantity and the output direction of a radio wave of the correction dielectric lens 4 are corrected by changing the shape and an optical length is controlled so that the phase distribution of the aperture is uniformized to obtain the aperture efficiency. Thus, the compact offset antenna whose manufacture cost is low and whose space is utilized effectively is realized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an earth station antenna used in the fields of satellite communication and radio astronomy, which is an offset type antenna that obtains high aperture efficiency and low sidelobe characteristics. It is.

[Conventional technology]

Figure 5 is a cross section Z showing a conventional off-cellar I-type antenna shown in Japanese Patent Application Laid-Open No. 49-52953, etc. In the figure, (11) is a main reflecting mirror whose rotational quadric surface has been mirror-finished, (2) ) Sub-reflector with mirror-finished rotational quadratic surface, (
3) is a −order radiator.

Next, the operation will be explained.

In such a sub-reflector antenna, in order to obtain high aperture efficiency and low sidelobe characteristics, a -order radiator (3rd
) The 2ffl rotating quadratic curved mirrors (the main reflecting mirror (11) and the sub-reflecting mirror (2)) are mirror-finished so that an optimal aperture distribution can be obtained when a radiation pattern of 2 ffl is given.

There are several methods for mirror surface modification, but they are numerically based on the principles of geometric optics: firstly, the energy within a single beam remains unchanged; secondly, the aperture is adjusted from the phase center of the primary radiator. The mirror coordinates of the two sets of mirrors are determined based on three conditions: that the optical path lengths up to the mirrors are equal, and thirdly, that the law of reflection is added for each mirror.

[The problem that the invention attempts to solve]

Since the conventional mirror surface modification type offset antenna is constructed as described above, the manufacturing cost of the mirror surface becomes a problem when the main reflecting mirror becomes large. Generally, in an antenna having a diameter of 5 m or more, the mirror surface is formed by a reflecting mirror panel that is divided in the circumferential direction (as the mirror surface becomes larger, it is necessary to divide it in the radial direction as well). The mirror-modified main reflecting mirror is non-rotationally symmetrical because it is an offset antenna, and each divided panel has a different mirror surface. This results in very high panel manufacturing costs. On the other hand, the main reflecting mirror that uses a rotating quadratic curved surface without mirror surface modification can be constructed with the same panel mirror surface in the circumferential direction if one mold is made, and the manufacturing cost of the five panels can be reduced.

As an offset type antenna that solves these problems, for example, in the 6th country, as shown in Figure 7, an auxiliary reflector (5
) and the auxiliary reflector (2) are being considered, but this would require space to place an auxiliary reflector that is about the same size as the auxiliary reflector, and the structure would be complicated. There were other problems.

This invention was made to solve the above-mentioned problems, and aims to effectively utilize space and obtain a compact offset antenna.

[Means to solve the problem]

In the offset antenna according to the present invention, the main reflecting mirror is not mirror-finished, but only the sub-reflecting mirror is mirror-modified to control the amplitude distribution in the aperture distribution, and the phase is corrected by the modified dielectric lens. It is something.

[Effect]

In the modified dielectric lens of this invention, the phase amount and radio wave output direction are corrected by changing its shape, and the optical FI8 length is controlled so that the phase distribution of the aperture surface is uniform in order to obtain high aperture efficiency. do.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the district, (1) is the main reflector that has not been mirror-finished;
(2) is a sub-reflector whose mirror surface has been modified to control the amplitude distribution in the aperture distribution, (3) is a -order radiator, (
4) is a modified Mt body lens placed near the focal point of the main reflecting mirror, (6) is the amplitude distribution on the aperture surface, and (7) is the phase distribution on the aperture surface.

Next, the operation will be explained. In order to obtain high aperture efficiency and low sidelobe characteristics, −
It is necessary to construct a mirror system that can obtain an optimal aperture distribution when given the radiation pattern of the secondary radiator (3). Conventionally, two sets of rotating quadratic curved mirrors (main reflector (11) and sub-reflector (2)) are mirror-finished, but in one embodiment of the antenna, the main reflector (1) is mirror-finished with fs adjustment. Therefore, it is necessary to change the direction of the radio waves from the mirror-modified sub-reflector and correct the phase amount in order to keep the optical path length constant.The modified dielectric lens (4) is used as a converter for this purpose. It was constructed using

By placing this modified dielectric lens (4) near the focal point of the main reflection R(1), the size can be reduced and a compact offset antenna can be constructed.

In addition, in the above embodiment, the main reflecting mirror (1) and the sub-reflecting mirror (2)
The modified dielectric lens (4) is placed between the main reflector (1), which has a rotating quadratic curved surface, as shown in Figure 2.
In a sub-reflector antenna consisting of a sub-reflector (21), an auxiliary reflector M (5) whose mirror surface is adjusted to fs as a rotating quadratic curved surface, and a -order radiator (3), the sub-reflector (21) and the auxiliary Even if a modified dielectric lens (4) is inserted between the reflecting mirror (5), the same effect as in the above embodiment can be obtained.

Also, the 3rd [N, 4th], which is one of the multi-beam earth stations,
The main reflecting mirror (1), the sub-reflecting mirror (21), and the auxiliary reflecting mirror (5a) with a 2M mirror surface, as shown in Fig.
, (5b) and -order radiators (3a), (3b), the sub-reflector (
By inserting modifying dielectric lenses (4a) and (4b) between 21) and the auxiliary reflecting mirrors (5a) and (5b), 2
Both beams have high efficiency and low sidelobe characteristics.

〔Effect of the invention〕

As described above, according to the present invention, since the auxiliary reflecting mirror that needs to be mirror-finished is replaced with a repairing dielectric lens, the device can be made at low cost, space can be used effectively, and the device can be compact. There are benefits to be gained.

[Brief explanation of drawings]

FIG. 1 is a mold side view showing an offset antenna according to one embodiment of the present invention, FIG. 2 is a sectional side view showing an offset antenna according to another embodiment of the invention, and FIG. 3 is another embodiment. FIG. 4 is a cross-sectional plan view showing the dual beam antenna, and FIGS. 5, 6, and 7 are cross-sectional side views showing a conventional offset antenna. In the figure, (1) is the main reflecting mirror that has not been mirror-finished;
(11) is the mirror-treated main reflector, (2) is the mirror-treated sub-reflector, (21) is the non-specular sub-reflector, (3) is the -order radiator, and (4) is the modified dielectric body lens, (5) is the auxiliary reflector with mirror finishing, (6) is the amplitude distribution on the aperture plane, and (7) is the phase distribution on the aperture plane. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a sub-reflector antenna consisting of a main reflector with a rotating quadratic surface, a sub-reflector whose mirror surface is modified with a rotating quadratic surface, and a primary radiator, the direction of radio waves and An offset antenna characterized by being constructed by including a modified dielectric lens that changes the phase.