JPS63240106A - Aperture antenna - Google Patents

Abstract

PURPOSE:To decrease the number of face elements without deteriorating the antenna performance by constituting a main reflecting membrane by sets of planar polygons and selecting the length of sides of the polygons placed near the circumferential ridge where the electric field applied at the spray to the main reflecting mirror is weaker longer than the length of sides near the middle part where the electric field at the spray is stronger. CONSTITUTION:In forming radially sectorial parts whose center angle is 60 deg. from the center 12 of the reflecting mirror being a component of an aperture antenna, each sector is approximated by sets of triangles 6 whose side is gamma/10 (gamma is the radius of the reflecting mirror) up to a point 5 corresponding to 60% of the radius of the reflecting mirror. In addition, triangles 7 whose side is gamma/5 are used to approximate the sectors at the outside of the point 6. Thus, the gain reduction is within a range of 0.1dB because of the effect of less number of divisions at the circumferential parts in comparison with the approximation of the entire sector by triangles whose side is gamma/10. Thus, the number of face elements is reduced and this antenna is suitable for expansion antennas for space or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to an approximate aperture antenna that is easy to manufacture and exhibits little deterioration in radiation characteristics.

(2) Prior Art In conventional antennas of this type, the main reflecting mirror was formed with a curved surface depending on the purpose. For example, a fixed pencil beam antenna uses a rotating radiation surface or a curved surface modified to obtain a desired aperture distribution based on the rotating radiation surface, and a spherical mirror is used for a multi-beam or scanning beam antenna. Therefore, it is necessary to realize a continuous change in curvature on the mirror surface and maintain its shape.

The manufacturing method relies on press molding and milling,
(i) It takes a long time to transform a flat plate into a desired curved surface. (ii) It is difficult to control the pressure in consideration of return deformation after manufacturing. (1ii) In order to make a foldable antenna, There were some drawbacks, such as the need for special measures.

Recently, an approximate reflector with planar polygons as surface elements has been proposed for the purpose of large-scale spaceborne antennas [1]
. Figure 2 shows an example in which this triangle is used as a surface element, where 1 is the periphery of the reflecting mirror, 2 is the boundary of the surface element, 3 is a flat reflective surface, and 12
is the center of the anti-r8 mirror.

If, for example, a 2 G l-1z borrowed antenna of 15 mφ is made in this format, in order to suppress the influence of approximation to a 0.1 dB gain reduction, it is necessary to divide the plane into 10 or more on the radius. Therefore, the node 4 of the surface element boundary line 2 is 3
There are 30 items, and it takes a lot of time to produce.

This becomes more noticeable as the antenna has a larger diameter and the frequency is higher.

[1] P, K, AOraWal et at,
, ”Prelimi-nary Oesign
or large reflectors wi
thF lat l”acets”, I E E
E, Trans, AP-29No, 4,
p, 688. July, 1981゜ (3) Purpose of the Invention In order to eliminate these drawbacks, the present invention changes the number of divisions of the reflecting mirror depending on the strength of the electric field blown from the -order radiator to the reflecting mirror. The purpose is to reduce the number of antenna components and manufacturing steps without compromising antenna performance.

(4) Structure and operation of the invention Figure 1 shows an embodiment of the invention, in which the reflector center 12 to 6
A sector-shaped portion of 0° is shown. The area up to point 5, which is 60% of the radius, is approximated by a triangle 6 with a side of r/10 (r: reflector radius), and the outside thereof is approximated by a triangle 7 with a side of r15.

In this case, the electric field 8 blown from the secondary radiator to the reflector is 3
As shown in the figure, the electric field strength is 065 at the center at the point 0.6r.
, 0.1 at the peripheral point. Therefore, compared to the case where the whole is approximated by a triangle of r/10, the gain reduction due to coarse division of the peripheral portion is within the range of 0.1 dB.

FIG. 4 shows the configuration of FIG. 2 with addition of surface element boundaries 9. In this case, even if the boundary line is made of strings that do not stretch, opposing forces in the radial direction are applied to the node 10, so by pulling the node from an appropriate point, tension is applied to each string, and the node position can be maintained. On the other hand, in order to hold each node with a string in the configuration shown in FIG. 2, it is necessary to make all the triangles having sides on the line segment 5-5' solid.

The above description has been about a parabolic antenna with an axially symmetrical configuration, but the same can be said of an offset parabolic antenna where the blowing angle from the primary radiator to the reflector is not at right angles. An example of this is shown in FIG. In this case, −
Since the secondary radiator is located at the bottom of the diagram, the electric field distribution on the aperture plane viewed from the antenna beam direction is biased downward. Therefore, while below the 8-8' line only fine divisions are made, above the line the number of divisions is changed.

The above explanation was about a semi-reflector antenna whose antenna consists of a primary radiator and a reflector, but the same thing applies to the main reflector of a double-reflection t11m antenna that has multiple sub-reflectors added to it. I can say that.

Further, as a plane that approximates the reflecting mirror, in addition to a triangle, a quadrilateral, a hexagon that is a close-packed figure, etc. can also be used. Regarding the number of divisions, in Figures 3, 4, and 5, the ratio between the coarse portion and the fine portion is 1:2, but other ratios may be used. Moreover, it does not necessarily have to be an integer ratio.

’ (5) Effects As explained above, without deteriorating antenna performance,
The number of surface elements that approximate the reflecting mirror can be reduced. Therefore, it is possible to contribute to reduction of steps and cost.

As for application fields, since this antenna can be made foldable, it can be used as a deployable space antenna, and it can also be used as an inexpensive communication antenna or radar antenna for use on the ground.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional reflecting mirror approximating a polyhedron, Figure 2 is an embodiment of the present invention, Figure 3 is an electric field distribution diagram on the reflector corresponding to Figure 2, and Figure 4 is another embodiment of the present invention. , 5 shows an example of application of the present invention to an offset Ambuna. 1...Periphery of the reflecting mirror 2...Boundary line of surface elements 3...Reflecting surface of plane 4...Node point of surface element boundary line 5. ... Boundary line of division method 6 ... Surface element 7 of fine division ... Surface element 8 of coarse division ... Electric field distribution curve 9 ... ... Added surface element boundary line 10 ... Added node 11-11" ... Boundary line between the area where the number of divisions is changed and the area where it is not changed 12 ... Reflection Center of the mirror 1 Figure 2 Figure 3 Figure 3 Figure 5 Figure 5' Procedural correction (method) % formula % Relationship to the case Patent applicant address 1-21-9 Hatsudai, Shibuya-ku, Tokyo Address Machida, Tokyo Ichitsurukawa 3-9-7-5, subject of amendment

Claims (1)

[Claims] The main reflector is approximated by a set of flat polygons, and the polygons near the periphery where the electric field blown onto the main reflector is weaker are made larger than the polygons near the center where the electric field blown onto the main reflector is stronger. , an aperture antenna characterized by increased side length.