JPH0767046B2 - Molded beam reflector antenna - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a shaped beam reflector antenna that modifies a reflector shape to form a shaped reflection pattern.

(Prior Art and its Problems) In contrast to an antenna that reflects a monomodal beam, a reflector antenna in which a radiation beam is shaped into a special shape is called a shaped beam reflector antenna. As seen in radars for airports, cosecant square beam shaping in a vertical plane, satellite mounted antennas shaped into special beams to illuminate only specific areas, etc. Many are in practical use.

A specific example of a conventional shaped beam reflector antenna that radiates a single beam will be described.

FIG. 1 is an example of a shaped beam reflector antenna including a reflector 1 and a feed horn 2. The longitudinal section curve 3 (YZ in-plane curve) of the reflecting mirror 1 is a curve such that the radiation beam in the YZ plane has a predetermined shape. As an example of the shaped radiation beam shape, a cosecant square beam is shown in FIG. Such a longitudinal section curve 3
The method of determining is already well known such as the method using a differential equation. On the other hand, cross-section curve group 4n (n = 1, ... i,
... n) is composed of a group of parabolas having a focal point at the position of the feed horn 2 so as to form a monomodal beam in the horizontal plane (in the XZ plane). By using such a reflecting mirror surface, an antenna that radiates a beam formed as shown in FIGS. 1B and 1C can be obtained. As the beam shape, not only a combination of cosecant squared beam / unimodal beam as shown in FIGS. 1B and 1C but also unimodal beam /
Reflector antennas with fan beams, cosecant squared beams / fan beams or more complex beam shapes can be derived from similar considerations. However, these reflector antennas do not have a multi-beam function or a beam shift function for simultaneously radiating a plurality of antenna beams.

Next, a parabolic torus antenna shown in FIG. 2A will be described as an example of a conventional reflector antenna capable of radiating a monomodal multi-beam. The vertical section curve 13 of the reflecting mirror 11 is a parabola having a focal point at the position of the feed horn 2. This parabola 13
The curved surface of the reflecting mirror 11 is a curved surface formed when the lens is rotated about the y axis in the vertical section or the y'axis slightly inclined from the y axis as the center of rotation. That is, the cross-sectional curve 14 is a circular arc. In this antenna, since the reflecting mirror is rotationally symmetrical with respect to the y-axis or y'-axis, if the feed horn 2 is rotationally moved around its rotational axis as indicated by 2 ', the radiation beam direction is also rotationally moved. That is, the beam shift antenna is capable of beam scanning with the reflecting mirror fixed. Further, instead of rotating one feeding horn, by arranging the feeding horn at a position where it is just rotated and exciting each separately, a multi-beam antenna that radiates a plurality of beams simultaneously is obtained.

The radiation beam width in the longitudinal and transverse sections of this antenna is
It varies depending on the outer peripheral shape (aspect ratio) of the reflecting mirror 11, the radiation pattern shape of the feeding horn 2, the ratio f / R of the focal length f of the parabola 13 and the radius R of rotation of the arc 14 (OM in FIG. 2), etc. Even in the cross section, the beam has a monomodal beam shape as shown in FIGS. Therefore, it was not possible to form a special beam shape as shown in FIG.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems of the prior art, and has a function as a shaped beam antenna and a function as a single-peaked multi-beam antenna or a beam shift type antenna. An object is to provide a beam reflector antenna.

(Structure and operation of the invention) An antenna according to the present invention has a beam that is one-dimensionally shaped in a longitudinal section, emits a plurality of beams in the transverse direction, and shifts the beam in the transverse section. It can be done.

(Example) FIG. 3A shows a configuration of a shaped beam reflector antenna according to the present invention. The antenna comprises a reflector 21 and one or more feed horns 2 (2 '). Longitudinal curve 23 of reflector 21
Is a curve similar to the already known longitudinal section curve 3 of the antenna of FIG. 1 and has a predetermined shape (for example, FIG.
The beam shaped into the (cosecant square beam of (b)) is emitted. The curved surface of the reflecting mirror 21 is a curved surface formed when the vertical section curve 23 is rotationally moved about the y axis in the vertical section or the y'axis slightly inclined from the y axis as the center of rotation. That is, the cross-section curve 24 is an arc. For the cross section,
A monomodal beam as shown by the solid line in FIG. 3C is emitted. The beam width of the beam in this cross section changes depending on the positional relationship between the reflecting mirror 21, the rotation axis, and the feeding horn 2, but FIG.
It becomes the narrowest near r / R = 0.5. Here, r is the distance between the phase center F of the feed horn 2 and the y axis (or y ′ axis).

As shown by 2'in the feed horn 2, the rotation axis (y
Axis or y'axis). Since the longitudinal section curve 23 'shown by the dotted line is equal to the curve 23, the radio wave radiated from the feeding horn 2'produces a shaped beam in the same way as before moving the feeding horn in the z-direction longitudinal section. That is, the beam direction moves in the horizontal plane as shown by the dotted line in FIG. 3C while maintaining the shaped beam shape in the vertical cross section as shown in FIG. 3B.

Thus, in the antenna according to the present invention, the feeding horn 2
The direction of the shaped beam can be changed by moving. Further, it is apparent from the above description that if a plurality of feed horns are arranged at positions rotationally moved around the rotation axis and excited respectively, a multi-beam antenna capable of radiating a plurality of shaped beams simultaneously can be obtained. .

An excitation method when the shaped beam antenna according to the present invention has another configuration for radiating multiple beams will be described.
FIG. 4A shows the case where each feed horn is independently excited, and in this case, a plurality of monomodal beams are radiated in the horizontal plane. When several feed horns are simultaneously excited through the power distributor 31 as shown in FIG. 4B, fan-shaped beams and unimodal beams can be mixedly radiated in the horizontal plane. As shown in FIG. 4C, it is also possible to collectively excite all the feeding horns to form a wide fan beam. Further, FIG. 5 shows an example in which a plurality of power feeding horns are fed through the power changeover switch 32, and the beam directions in the horizontal plane can be sequentially changed over by switching the switches. Although only the beam shape in the horizontal plane is schematically shown in FIGS. 4 and 5, it is needless to say that the beam shape in each vertical section is formed as shown in FIG. 3B, for example.

(Effects of the Invention) As described above, the shaped beam antenna according to the present invention has a shaped beam and further has a multi-beam function and a beam shift function.

For example, in a radar antenna for an airport, the entire antenna that radiates a beam shaped as a cosecant squared in a vertical plane is mechanically rotated to scan in a horizontal plane. According to the shaped beam antenna according to the present invention, , Because the beam can be scanned by simply moving the feeding horn without moving the reflecting mirror, or by arranging a plurality of feeding horns and electrically switching the beam formed by cosecant square shaping,
The mechanical device is simplified and high-speed scanning becomes possible.

In addition, as seen in the land mobile radio system and land subscriber radio system, in the antenna of the parent radio station (base station) that communicates with a large number of child radio stations that are distributed in a plane, the antennas that are far away in the horizontal direction can be used. It is necessary to form a beam shape in the vertical plane because it is necessary to communicate with the slave station directly below the master station. Also, it is necessary to radiate several beams in the horizontal plane to cover the whole. In such a case, if the shaped beam antenna according to the present invention is applied, several beams can be collectively emitted by one antenna, so that the number of antennas can be reduced.

[Brief description of drawings]

1A, 1B, and 1C are schematic diagrams showing a configuration of a conventional shaped beam reflector antenna and characteristic diagrams for explaining an example of a beam shape, and FIGS. 2A, 2B, and 2C are parabola. FIG. 3A, FIG. 3B, and FIG. 3C are schematic views showing a configuration of a torus antenna and characteristic diagrams for explaining an example of a beam shape, and FIGS. FIG. 4 is a characteristic diagram for explaining an example.
(A), (b), (c) and FIG. 5 are schematic diagrams for explaining the excitation method and the beam shape when the shaped beam reflector antenna according to the present invention is used in a multi-beam configuration. 1,11,21 …… Reflector, 2 …… Feeding horn, 3,23 …… Molded longitudinal section curve, 13 …… Vertical section curve (parabola), 4n…
… Cross section curve (parabola), 14,24… Cross section curve (arc), 31 …… Power distributor, 32 …… Power switch.

Claims (1)

[Claims] 1. A parabolic curve having a reflecting mirror and a feeding primary radiator, and having a focal point at the phase center of the feeding primary radiator, is shaped so as to obtain a predetermined radiation beam. A curved surface formed by rotating the obtained vertical section curve of the reflecting mirror with a vertical axis perpendicular to the axis of symmetry of the radiator curve or an axis slightly inclined from the vertical axis in the vertical section as a rotation axis. Is formed to be the curved surface of the reflecting mirror, and one feeding primary radiator is moved so as to match the position where the feeding primary radiator is rotationally moved about the rotation axis, or A plurality of feeding primary radiators are arranged at the rotationally moved position and at least one is selected from the plurality of feeding primary radiators so that desired radiation characteristics can be obtained. Shaped beam reflector antenna.