JP2009017346A - Antenna power feed unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna power feed unit, which has a broadband frequency characteristic and does not need huge operation for obtaining a superior return loss characteristic. <P>SOLUTION: At a view of cross section crossing at right angles with a center axis of a circle, a slanted portion of a conical dielectric supporting member from a first radiator 3 to a sub-mirror 2 has a structure in which unevenness is repeated along its circular periphery with a repeated cycle shorter than the wavelength, and an unevenness difference dimension at the slanted face is made 1/4 of unevenness inside wavelength, or a structure in which the unevenness is repeated with a repeated cycle shorter than the usage wavelength in a coaxially way with the central axis of the circle and in a direction of intersection with a plane including the central axis of the slanted portion, and the unevenness difference dimension at the slanted portion is made 1/4 of the unevenness inside wavelength. In this way, an equivalent matching layer is formed at the slanted portion of the dielectric supporting number. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention reduces reflection of an electromagnetic wave reflected by a sub-reflector at the interface between the dielectric and the space of a double reflector antenna having a sub-reflector supported by a dielectric support member from the primary radiator. It belongs to the technical field of reflection suppression.

FIG. 6 is a side sectional view of a conventional double reflector antenna. The sub-reflecting mirror 2 is supported with its reflecting surface 6 in close contact with the dielectric support member 1, and the other end of the dielectric support member 1 is inserted and held in the primary radiator 3.
The electromagnetic wave radiated from the primary radiator 3 diffuses and propagates in the dielectric support member 1 toward the sub-reflecting mirror 2, is reflected by the reflecting surface 6 of the sub-reflecting mirror 2, and is behind the primary radiator 3. It faces the main reflecting mirror 11 and is re-reflected by the main reflecting mirror 11 to be emitted into the space.

FIG. 7 is an enlarged view of a portion excluding the main reflecting mirror 11 of FIG.
The electromagnetic wave is reflected by the sub-reflecting mirror 2 and exits from the dielectric support member 1 to the space on the way to the main reflecting mirror 11. However, since the dielectric support member 1 and the space have different dielectric constants, reflection occurs at the interface R between the space and the dielectric support member 1.
This reflection is a loss (reflection loss = return loss) because a part of the electromagnetic wave to be radiated returns without being radiated.

Therefore, conventionally, the shape of the dielectric support member 1 and the shape of the reflecting surface 6 of the sub-reflecting mirror 2 have been devised so as to reduce this reflection loss and obtain a desired feeding directivity (for example, Non-patent document 1).
A.Kumar, PERFORMANCE OF REFLECTOR ANTENNAE WITH SPLASH PLATE FEED, IEEE AP-S Intl.Symp.Proceedings, USA, IEEE, 1984, vol.22, P.482-485

  However, in order to obtain both the desired directivity and low reflection loss, a large amount of computation is required to optimally design the curved surface, and the interference due to the reflected wave has frequency dependence, so that it has a wide frequency response. There was a problem that it was difficult to get.

  An object of the present invention is to realize an antenna feeding unit that does not require processing of an enormous amount of computation and has a wideband frequency characteristic in view of the problems of the above-described prior art.

The present invention has the following means to solve the above problems.
In the first configuration of the present invention, a conductor having a circular periphery and forming a reflection surface protruding from the circumference to one side of a plane including the circumference is supported with the reflection surface closely attached to a dielectric. The shape of the dielectric is circular in the cross section orthogonal to the central axis of the circle, and the diameter gradually decreases as the distance from the close contact portion of the conductor increases, and reaches the end portion to fit into the primary radiator. It is a shape, and when viewed in a cross section perpendicular to the center axis of the circle, the concave and convex portions are repeated along the circumference at a repetition interval shorter than the operating wavelength, and the unevenness difference dimension on the inclined surface is uneven. The antenna feeding unit is characterized in that it is one-fourth of the internal wavelength.

  According to a second configuration of the present invention, a conductor having a circular periphery and forming a reflection surface protruding from the circumference to one side of a plane including the circumference is supported by bringing the reflection surface into close contact with a dielectric. The shape of the dielectric is circular in the cross section orthogonal to the central axis of the circle, and the diameter gradually decreases as the distance from the close contact portion of the conductor increases, and reaches the end portion to fit into the primary radiator. It has a shape, and the concave and convex portions on the inclined surface are repeated at a repetition interval shorter than the wavelength used in the direction of the line of intersection with the surface including the central axis of the inclined portion and concentric with the central axis of the circle. The antenna feeding portion is characterized in that the difference dimension is ¼ of the wavelength in the uneven portion.

  The antenna feeding portion of the first configuration of the present invention is along the circumference of the inclined portion of the dielectric support member from the primary radiator to the sub-reflecting mirror when viewed in a cross section perpendicular to the central axis of the circle. The unevenness is repeated at a repetition interval shorter than the used wavelength, and the unevenness difference dimension in the inclined portion is ¼ of the wavelength in the unevenness.

  Further, the antenna feeding portion of the second configuration of the present invention is concentric with respect to the central axis of the circle, and the central axis of the inclined portion is formed on the inclined portion of the dielectric support member from the primary radiator to the sub-reflector. In the direction of the line of intersection with the included surface, the unevenness is repeated at a repetition interval shorter than the used wavelength, and the unevenness difference dimension in the inclined portion is a quarter of the wavelength in the unevenness portion.

Both of these two configurations have irregularities as shown in FIG. 4A on the surface of the dielectric support member.
(A) is sectional drawing, and the recessed part (groove part) and the convex part are alternated. r is selected to be sufficiently shorter than the wavelength of the operating frequency at the repetition interval of the unevenness. The depth (step size) h of the concave portion is set to ¼ of the wavelength within the concave and convex portion.

In such a structure, as in the surface R of FIG. 7, when the electromagnetic wave propagates from the dielectric support member 1 side to the space, the electromagnetic wave that passes through the interface at the bottom of the concave portion and the electromagnetic wave that passes through the interface at the top of the convex portion. However, reflection into the dielectric support member occurs at each point. However, since the depth h of the concave portion is set to a quarter wavelength, the electromagnetic wave reflected on the upper surface of the convex portion is a distance closer to about a half wavelength than the reflected wave reflected on the bottom portion of the concave portion. Propagation takes place over a long distance, the phase of which is close to the opposite phase to the reflected wave reflected at the bottom of the recess, and the reflected waves cancel each other.
As a result, the number of reflected waves toward the dielectric support member 1 is reduced. That is, there is an effect that the reflection loss is reduced.

In such a structure, the portion with the thickness h on the surface of the dielectric support member 1 is configured such that the portion where the dielectric is present and the portion where the dielectric is not present are alternately configured, so that the distance r is sufficiently larger than the wavelength of the operating frequency. It can be assumed that a dielectric layer having a low dielectric constant is present by reducing the size. It can be considered that by setting h to about one-fourth of the wavelength in the dielectric layer, it becomes a matching layer that reduces reflection and suppresses reflection at the interface. This is illustrated in FIG. 4B.
That is, the electromagnetic wave from the dielectric support member 1 side is first partially reflected at the interface with the matching layer 7 and then partially reflected at the interface between the matching layer 7 and the space. Therefore, the two reflected waves are nearly out of phase and cancel each other, resulting in less reflection.

When providing the uneven structure on the inclined surface of the dielectric support member, it is not necessary to provide it on the entire surface, and it is best to provide it on the portion where the electromagnetic field is strong.
In the first configuration, it is best for the characteristics of the antenna including the main reflector to prevent the convex portion of the dielectric support member from protruding from the outer circumference of the sub-reflector when viewed from the back of the sub-reflector. It is an embodiment.

With respect to the production of the dielectric support member, mold forming is the best embodiment for mass production of the first configuration.
In the case of the structure having the concentric grooves of the second configuration, the production by rotary cutting is the best embodiment.

Hereinafter, embodiments of the antenna feeding unit of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the first configuration of the present invention. (A) is side sectional drawing, (b) is the front view which looked at (a) from the right.

FIG. 2 is a perspective view of the embodiment of FIG. The left portion of the dielectric support member 1 is inserted into and supported by the primary radiator 3, extends conically from the opening of the primary radiator 3, and has a reflecting surface 6 on the right side. The sub-reflection mirror 2 is supported by being in close contact with the reflection surface 6.
In the dielectric support member 1, a convex portion 5 having a height h extends to the circumferential portion of the sub-reflecting mirror 2 from the middle of spreading in a conical shape. A concave portion which is necessarily a space is formed between the convex portion 5 and the convex portion 5. The height h of the convex portion is about a quarter of the wavelength in the concave and convex portion.

Further, the repetition interval (pitch) r of the convex portion 5 is set sufficiently shorter than the wavelength. In this example, the convex portion 5 is not provided in the first portion that is conical from the opening of the primary radiator 3 because the intensity of the electromagnetic field reflected by the sub-reflecting mirror 2 is low.
By providing the convex portion 5 and the concave portion 4 as described above, the matching layer 7 described in FIG. 4B is formed, the amount of reflection on the surface R shown in FIG. 7 is reduced, and the reflection loss characteristic is reduced. Improved.

FIG. 5 is a reflection loss characteristic obtained by calculating and graphing the reflection loss for the embodiments of FIGS.
A broken line is a case without the conventional unevenness | corrugation, and a continuous line is a case of this invention Example. This shows that the reflection loss is reduced over the entire band.
The ratio d / r of the width d of the convex portion 5 to the repeating interval r of the convex portion 5 is increased when the direction of the electric field is orthogonal to the longitudinal direction of the concave portion 4 or the convex portion 5, and is decreased when the direction is parallel. The effect of reduction is increased.

FIG. 3 is a perspective view showing an embodiment of the second configuration of the present invention.
The inclined portion of the dielectric support member 10 from the primary radiator 3 to the sub-reflecting mirror 2 is concentric with respect to the central axis of the circle of the sub-reflecting mirror 2, and the line of intersection between the plane including the central axis and the inclined portion The convex portions 8 and the concave portions 9 are repeated in the direction at a repetition interval sufficiently shorter than the use wavelength, and the step size between the convex portions 8 and the concave portions 9 is about one quarter of the wavelength in the concave and convex portions.

  By providing the convex portion 8 and the concave portion 9 as described above, the matching layer 7 described in FIG. 4B is formed, and the amount of reflection on the surface R shown in FIG. 7 is reduced. Similar to the second embodiment, the reflection loss characteristic is improved.

It is a 2nd page figure showing the example of the 1st composition of the present invention. It is a perspective view of the Example of the 1st structure of this invention. It is a perspective view of the Example of the 2nd structure of this invention. It is explanatory drawing of reflection loss reduction in this invention. It is the reflection loss characteristic figure which computed the reflection loss about the Example of FIG. 1, FIG. 2, and was made into the graph. It is a sectional side view of the conventional double reflector antenna. It is an enlarged view of the part except the main reflective mirror of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric support member 2 Subreflective mirror 3 Primary radiator 4 Concave part 5 Convex part 6 Reflecting surface 7 Matching layer 8 Convex part 9 Concave part 10 Dielectric support member 11 Main reflector

Claims (2)

  A conductor having a circular periphery and forming a reflecting surface protruding from the circumference to one side of a plane including the circumference is supported by bringing the reflecting surface into close contact with the dielectric, and the shape of the dielectric is the shape of the circle The cross section perpendicular to the central axis is circular, and the diameter gradually decreases as the distance from the close contact portion of the conductor increases, reaches the end, and fits to the primary radiator. In addition, when viewed in a cross section perpendicular to the center axis of the circle, the unevenness is repeated along the circumference at a repetition interval shorter than the wavelength used, and the unevenness difference dimension on the inclined surface becomes a quarter of the wavelength in the unevenness. An antenna feeding portion characterized by that.   A conductor having a circular periphery and forming a reflecting surface protruding from the circumference to one side of a plane including the circumference is supported by bringing the reflecting surface into close contact with the dielectric, and the shape of the dielectric is the shape of the circle The cross section perpendicular to the central axis is circular, and the diameter gradually decreases as the distance from the close contact portion of the conductor increases, reaches the end, and fits to the primary radiator. In addition, unevenness is repeated at a repetition interval shorter than the operating wavelength in the direction of the line of intersection with the surface including the central axis of the inclined portion, which is concentric with respect to the central axis of the circle, and the unevenness difference dimension on the inclined surface is 4 minutes of the wavelength in the unevenness An antenna feeding portion characterized by being 1 of the above.

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