JPS60182804A - Antenna system - Google Patents

Abstract

PURPOSE:To obtain an antenna system with high efficiency and low side lobe by constituting a mirror surface system so that a focus of a main reflection mirror and a sub-reflection mirror exists within the mutual focal distance. CONSTITUTION:The mirror surface system is constituted that the focii F2 and F1 of the main reflection mirror 3 and the sub-reflection mirror exist mutually within the other focal distance and the relation of (F2M)>(F1M) is maintained. Further, the aperture of the main reflection mirror 3 is expanded until the conical curve tying the surrounding of the sub-reflection mirror 2 and the focus F1 crosses the main reflection mirror 3. Through the constitution above, a radio wave 5 irradiated from the phase center F0 of a conical horn 1 through the sub- reflection mirror 2 is regarded as if it were irradiated from the focus F2 of the main reflection mirror 3 equivalently because of the wave property of the radio wave. Thus, the spillover component from the main reflection mirror 3 is almost eliminated and the entire face of the main reflection mirror 3 is irradiated effectively, then the desired purpose is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in antenna devices used in microwave relay lines and the like.

[Conventional technology]

Conventionally, an antenna device includes a primary radiator (1) having a phase center FO as shown in FIG.
) and a main reflecting mirror (3) consisting of a parabolic mirror of rotation that shares the focal point F1.

In the figure, Ml and M are the rays +41 emitted along the central axis of the primary radiator ill, which is 4! r This is the point that hits the mirror surface.

As is clear from the configuration diagram in Fig. 1, this antenna is designed based on geometric optics, so the circumferential t&number region where geometric optics is established and D/λ (Dz main reflecting mirror aperture diameter, λ:
The free-space wavelength) is very large - the antenna has constant aperture efficiency over a wide band and low side lobes. however.

In antennas that have a small-diameter main reflector with an aperture diameter of 50λ or less, or antennas that aim for high efficiency by increasing the peripheral level of the main reflector (3), the radio wave (5) is as shown by the dotted line in the figure. Because it has a wave-like spread.

There are many spillover components from the main reflecting mirror (3).

This caused the antenna's wide-angle directional characteristics to deteriorate. or.

In the figure, as is clear from the path of the radio wave (5), Fl, which is the common focus of the sub-reflector (2) and the main reflector (3), becomes F2, where F+M ) F2M fil apparently holds, Radio waves (5) appear to be radiated from this F2. Therefore, the focal length f of the main reflector
m becomes fm=j-F2M (1+cosθ0) +21, which makes it appear shorter. Here, θU is the angle formed by the incident wave 1 reflected wave of the central axis ray (4).

Therefore, in the case of a small-diameter antenna as described above, the effective aperture diameter of the main reflecting mirror when considered from the perspective of geometrical optics is the focal length fm.
Since it is proportional to 1, it is equivalently small, but not only does the wide-angle directivity characteristic deteriorate, but it also causes a decrease in aperture efficiency.

[Summary of the invention]

In order to eliminate these drawbacks, this invention uses a sub-reflector (
2) and a mirror system configured such that the focal points of the main reflecting mirror (3) are confocal, and will be described in detail below with reference to the drawings.

[Embodiments of the invention]

FIG. 2 shows an embodiment of this invention.

(1) is a conical horn serving as a -order radiator, (2) is a sub-reflector made of a rotating quadratic curved mirror, and (3) is a main reflector made of a rotating paraboloid mirror. 70. Fl is the focal point of the sub-reflector (2), and FQ is also the phase center of the conical horn.

Furthermore, F2 is the focal point of the main reflecting mirror (3). In Fig. 2, when considering geometrical optics, the points where the light ray (4) emitted along the central axis of the two-conical horn (1) hits each reflecting mirror are Ml and M in order.

FQ, Fl, F2. It is assumed that Ml and M are on the same plane, and that FIM and F2M are on the same line.

In terms of geometrical optics, the mirror system of this antenna is such that the light beam (4) emitted from the phase center FO of the two-conical horn (11) passes through the sub-reflector (2) to the focal point F1 of the sub-reflector (2). The shape of the main reflecting mirror (3) is determined to satisfy Equation (3).

F2M>FIM' +31 Also, the aperture diameter of the main reflector (3) is until the extension curve of the cone connecting the same side of the sub-reflector (2) and the focal point F2 intersects with the main reflector (3). It has been expanded.

In the antenna device configured as above.

The radio wave (5) radiated from the phase center FO of the conical horn ft) and passed through the sub-reflector (2) is radiated from the focal point F2 of the main reflector (3) in one equivalent manner due to the wave nature of the radio wave. It looks like it will be done. Therefore, the spillover component from the main reflecting mirror (3) is almost eliminated.
Since the entire surface of 3) is effectively irradiated, it is possible to achieve low side ropes and high efficiency of the antenna.

In the above description, a conical horn is used as the -order radiator, but the present invention is not limited to this, and any primary radiator having a central axis may be used.

Further, although the case where the main reflecting mirror (3) is directed downward has been described in the above two cases, the present invention can be applied even when the main reflecting mirror (3) is directed upward.

〔Effect of the invention〕

As described above, the present invention has the advantage that spillover components from the sub-reflector can be reduced and the main reflector can be efficiently irradiated, so that a highly efficient antenna with low side lobes can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a conventional antenna device, and FIG. 2 is a configuration diagram of an antenna device showing an embodiment of the present invention. In the figure, (1) is the -order radiator, (2) is the sub-reflector, +3)
is the main reflecting mirror, (4) is the light #l, and (5) is the radio wave. Note that in FIG. 1, the same or corresponding parts are designated by the same reference numerals. Agent Masuo Oiwa

Claims (1)

[Claims] A sub-reflector is arranged between the primary radiator and the main reflector. In an antenna device configured such that radio waves are focused on the focus of the main reflector by the pressure of the sub-reflector. The focal point of the 10,000 sub-reflector that coincides with the phase center of the -order radiator is Fo, and the other focal point is F'1. When considering the focal point of the main reflector as F2 and considering geometric optics, if the points where the light ray emitted along the central axis of the -order radiator hits the sub-reflector and the main reflector are Ml and M, then Po . -) F2M are on the same line, F2M)FlM until the extension curve of the cone connecting the periphery of the sub-reflector and the focal point F2 intersects the main reflector. An antenna device characterized by an enlarged aperture diameter of the main reflecting mirror.