JPH0284802A - Scan antenna - Google Patents

Abstract

PURPOSE:To eliminate the difference of peak width between both high and low frequency band areas by providing a part which transmits the electromagnetic wave of high frequency band area and reflects that of low frequency band area at part of the reflecting mirror of a scan antenna being shared in two or more frequency band areas in an ultra high frequency band area. CONSTITUTION:Each parallel cross-section of the reflecting mirror 3 of the scan antenna forms a cylindrical mirror surface that is part of a radiant ray and consisting of upper, middle, and lower reflecting mirrors 5, 4, and 6. Also, the focal point group of the reflecting mirror 3 is represented as a straight line P perpendicular to paper and beam width 2 of angle theta represents the radiant robe of the scan antenna. In case of using the reflecting mirror 3 in two frequency band areas, the mesh interval of a reflecting plane is set so as to reflect the electromagnetic wave of low frequency band area and to transmit that of high frequency band area by the reflecting mirrors 5 and 6. Also, the low frequency band area of the electromagnetic wave radiated from primary radiators (1a-1N) arranged on a straight line F formed by connecting the focal points of the reflecting mirror 3 is reflected on the reflecting mirrors (4-6), and the high frequency band area of the electromagnetic wave is reflected on only the reflecting mirror 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning antenna, and particularly to a scanning antenna that can be used in common in two or more frequency regions of an ultra-high frequency band.

[Conventional technology]

Conventionally, this type of scanning antenna has a zero reflector 10 that is composed of a reflector 10 and a plurality of primary radiators 11, as shown in the perspective view of FIG. 3 and the side view of FIG. teeth,
The entire surface is made of a conductive mirror surface, and the mirror surface is formed by a portion of the radiation in all cross sections parallel to the paper plane of FIG. The plurality of primary radiators 11 are arranged so that the radiation phase center is located near the focal group of the reflecting mirror 10, which is aligned with a line (F in FIG. 4) perpendicular to the plane of FIG. 4. The phase difference between the ultra-high frequencies supplied to each of the plurality of primary radiators 11 from a phase control section (not shown) is changed over time. Multiple 1s obtained from this ultra-high frequency
The electromagnetic waves radiated from the secondary radiator 11 are reflected by the reflecting mirror 10 to obtain a combined antenna secondary radiation beam. The directivity of this secondary radiation beam is approximately parallel to the mirror axis A of the reflecting mirror 10 shown in FIG. 4, and the directivity changes over time in a direction perpendicular to the plane of the paper.

Conventional scanning antennas as described above have been known.

[Problem to be solved by the invention]

In the conventional scanning antenna described above, the mirror surface of the reflecting mirror 10 is made of a conductive material over the entire surface, so that electromagnetic waves in two different frequency bands are emitted from the plurality of primary radiators 11 arranged in a row. 4, the beam width of the secondary radiation beam reflected by the reflecting mirror 10 has a disadvantage that the beam width θH in the high frequency band is narrower than the beam width θL in the low frequency band, as shown in FIG.

An object of the present invention is to provide a scanning antenna that is formed by electromagnetic waves in either the high frequency band or the low frequency band in a plane including the vertical axis X and the main axis of the beam on the paper of FIG. The object of the present invention is to provide a scanning antenna that can form the same beam width.

[Means to solve the problem]

The scanning antenna of the present invention is a cylindrical curved plate whose cross section cut parallel to one reference plane has the same parabola shape, and the entire length along the parabola is the length of both ends. Divide into three parts with length M of the sashimi and central part.
a reflecting mirror in which lengthwise portions of the end portions are formed by two curved plates made of conductive mesh, and a length M portion of the central portion is formed by a curved plate made of a conductive material; It has a plurality of primary radiators that radiate electromagnetic waves to the reflecting mirror on a line that connects the focal points of the mirrors.

〔Example〕

The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of one embodiment of the present invention, and FIG. 2 is a side view of FIG. 1. The scanning antenna of this embodiment includes a plurality of primary radiators IA to IN and a reflector 3.
is composed of an upper reflecting mirror 5 made of a conductive mesh, a lower reflecting mirror 6 similar to the upper reflecting mirror 5, and a central reflecting mirror 4 whose entire mirror surface is made of a conductive surface.

In FIG. 2, each section of the mirror surface of the reflecting mirror 6 parallel to the plane of the paper is a part of a parabola, and forms a cylindrical mirror surface consisting of the above-mentioned upper, central and lower reflecting mirrors 5, 4.6. In addition, the focal group of the reflector 3 is a straight line F perpendicular to the plane of the paper, and the beam width 2, θ, is 0, which indicates the radiation lobe of the scanning antenna of this embodiment.When the reflector 3 is shared by two frequency bands, the upper and lower The spacing between the meshes of the reflective surface is selected so that the reflecting mirror 5.6 reflects incident electromagnetic waves in a low frequency band and transmits incident electromagnetic waves in a high frequency band. On the other hand, primary radiators IA to IN are arranged on a straight line F that connects the focus of the reflecting mirror 3.
Among the electromagnetic waves emitted from the , the electromagnetic waves in the low frequency band are
Central, upper, and lower reflecting mirrors 4, 5, which constitute the reflecting mirror 3.
However, the electromagnetic waves in the high frequency band are reflected only by the central reflecting mirror 4.

For example, if the ratio of the frequencies approximately at the center of the low frequency band and the high frequency band is 10:1, the conductivity of the upper and lower reflecting mirrors 5 and 6 with respect to the wavelength λ of the electromagnetic wave in the low frequency band If the minimum spacing between the meshes is set to around λL/20, the upper and lower reflectors 5 and 6 can have the function of reflecting electromagnetic waves in the low frequency band and transmitting electromagnetic waves in the high frequency band. It will be done.

The beam width of the electromagnetic wave radiated by the reflecting mirror 3 is determined by the supplied frequency and the length L (or M) along the parabola shown in FIG.
Therefore, depending on the difference in the center frequencies of the low and high frequency bands used, the upper and lower reflectors 5,
By setting the ratio between the length of 6 and the length M of the area of the central reflecting mirror 4, it is possible to obtain the same beam width 2 in the plane including the X-axis in both the low and high ranges. Furthermore, the method of forming a scanning beam involves applying ultrahigh frequency power to the primary radiators IA to IN arranged horizontally in a row on straight line F in FIG. 1 via an external phase control section (not shown). Power and primary radiator IA
This is obtained by sequentially changing the mutual phase of the supplied power from IN to IN over time. In this example,
Although the primary radiator is a rectangular waveguide horn, it can also be configured with a helical antenna or a microstrip antenna, for example.

〔Effect of the invention〕

As explained above, the present invention provides a portion of the reflecting mirror that substantially transmits electromagnetic waves in a high frequency band and reflects electromagnetic waves in a low frequency band.
This has the effect of making it possible to share at least two or more frequency bands with one reflecting mirror, thereby realizing a scanning antenna with no difference in beam width between the image frequency bands of the high and low frequency bands.

length. X: An axis that runs perpendicular to A and is perpendicular to the plane of the paper in Figure 2.

Claims (1)

[Claims] A cylindrical curved plate whose cross sections cut parallel to one reference plane have the same parabola shape, and the entire length along the parabola is the length of both ends. It is divided into three parts with a length L and a length M at the center, and the length L at both ends is formed by two curved plates made of conductive mesh, and the length M at the center is formed by two curved plates made of conductive mesh. Scanning characterized by having a reflecting mirror formed of a curved plate of a conductive material, and a plurality of primary radiators that radiate electromagnetic waves to the reflecting mirror on a line connecting the focal points of the reflecting mirror. antenna.