JPH01268204A - Reflection mirror antenna - Google Patents

Abstract

PURPOSE:To reduce the mechanical dimensions ot the title antenna by arranging a primary radiator and auxiliary reflecting mirror in such a way that the whole mapping of the primary radiator and auxiliary reflection mirror projected on a plane containing the effective area of a main reflection mirror can be in the effective ares and, at the same time, can be offset from the center of the effective area. CONSTITUTION:Since the whole mapping of the primary radiator 3 and auxiliary reflection mirror 2 projected on the plane containing the effective area of the main reflection mirror 2 is in the effective area, the mechanical dimensions of this antenna coincides with the aperture of the main reflection mirror 1. Moreover, since the radio waves radiated from the radiator 3 are radiated into the space except the part intercepted by the auxiliary mirror 2 and a support 4 in the vicinity of the opening of the radiator 3 where the intensity of the electric field is high after the radio waves are reflected by the auxiliary and main reflection mirrors 1 and 2, deterioration of the radiating characteristics by means of the mirror 2 and support 4 can be reduced. Thus the mechanical dimensions of the whole body of this antenna can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small antenna used in an earth station for terrestrial microwave communication or satellite communication.

[Prior art] Figures 3(a) and 3(b) are shown in FIG.
Vol, 48. No. 7.1974. FIG. 2 is a side view and a front view showing a schematic configuration of a conventional axially symmetrical reflector antenna disclosed in P2O3. In the figure, 1 is the main reflecting mirror, 2
is a sub-reflector, 3 is a primary radiator, and 4 is a support column that connects and holds the sub-reflector 2 with the main reflector 1.

Figures 4 (a) and (b) are shown in the example "Mitsubishi Electric Technical Report J
Vol, 54. No. 12.1980. It is a side view and a front view which show the schematic structure of the conventional offset type reflector antenna disclosed by P58.

In the figure, 1 is a main reflecting mirror, 2 is a sub-reflecting mirror, 3 is a primary radiator, and 4 is a support column that connects and holds the sub-reflecting mirror 2 with the main reflecting mirror 1.

Next, the operation of the conventional axially symmetric reflector antenna and offset reflector antenna will be described. Radio waves radiated by the primary radiator 3 are reflected by the sub-reflector 2, then reflected by the main reflector 1, and radiated into space.

[Problems to be Solved by the Invention] Since the conventional reflector antenna described above is configured as described above, first, in the case of the axially symmetric reflector antenna shown in FIGS. 3(a) and (b), Among the radio waves reflected by the main reflector 1, the radio waves near the center of the aperture where the electric field strength is high are blocked by the sub-reflector 2 and the support column 4, resulting in lower gain and side lobes. Deterioration of radiation characteristics such as an increase in the level has become a problem.Furthermore, among the radio waves emitted by the primary radiator 3, the radio waves with high electric field strength near the central axis of the primary radiator 3 are transmitted to the sub-reflector 3. There is a problem in that the VSWR (standing wave ratio) characteristic of the primary radiator 3 deteriorates because it is reflected by the radiator and enters the primary radiator 3 again.

In addition, in the case of the offset reflector antenna shown in FIGS. 4(a) and 4(b), the radiation characteristics may deteriorate due to radio wave shielding of the sub-reflector 2 and the support column 4 in the above-mentioned axially symmetric reflector antenna. , there is no problem of deterioration of VSWR characteristics due to reflection from the sub-reflector 20, but when the aperture diameters of both antennas are made the same, the mechanical dimensions of the antenna are larger in the offset reflector antenna. . moreover,
Generally, the central axis of the primary radiator 3 does not coincide with the mirror axis of the main reflecting mirror 1, which poses a problem in that the direction adjustment of the antenna becomes complicated.

This invention was made to solve the above-mentioned problems, and in addition to reducing the mechanical dimensions of the antenna, it also reduces the deterioration of radiation characteristics due to the shielding of the sub-reflector and support column.
It is an object of the present invention to obtain a reflector antenna that can reduce deterioration of vSWR characteristics due to reflection from a sub-reflector.

[Means for Solving the Problems] The reflector antenna according to the present invention has a primary radiator and a sub-reflector projected onto a plane including the aperture of the main reflector, and the entire map is within the aperture. A primary radiator and a sub-reflector are arranged offset from the center of this aperture.

[Operation] In the reflector antenna of this invention, the radio waves emitted by the primary radiator are reflected by the sub-reflector and then reflected by the main reflector, and the sub-reflector and support are formed near the periphery of the aperture where the electric field strength is small. It is radiated into space except for the part shielded by pillars. [Embodiment] Figures 1(a) and 1(b) are a side view and a front view showing a schematic configuration of a reflector antenna which is an embodiment of the present invention, and show a case of a Cassegrain antenna type. In the figure, 1 is a main reflector whose focal point is point F1, 2 is a sub-reflector whose focus is points F1 and F2, 3 is a primary radiator whose phase center is located at point F2, and 4 is a main reflector. This is a support column that connects the sub-reflector 1 and the sub-reflector 2 and holds the sub-reflector 2.

Next, the operation of the reflector antenna, which is an embodiment of the present invention shown in FIGS. 1(a) and 1(b) above, will be explained using the case of transmission as an example. The spherical wave with the center of curvature at point F2 emitted from the primary radiator 3 is converted into a spherical wave with the center of curvature at point F1 after being reflected by the sub-reflector 2,
Finally, after being reflected by the main reflecting mirror 1, it is converted into a plane wave and radiated in the mirror axis direction of the main reflecting mirror 1. The radio waves converted into plane waves by the main reflecting mirror 1 are partially blocked by the sub-reflecting mirror 2 and the support column 4. Here, main reflecting mirror 1
The plane wave converted by has a tapered electric field intensity distribution in which the electric field strength is strong at the center of the aperture and weak at the periphery of the aperture. Since the sub-reflector 2 and support column 4 that shield radio waves are arranged so that their images are placed near the periphery of the opening, the electric field strength of the radio waves to be shielded is lower than that of the conventional axisymmetric reflector described above. It is weaker than in the case of an antenna, and deterioration of radiation characteristics such as a decrease in gain and an increase in sidelobe level can be improved the most. Furthermore, since the entire mapping of the primary radiator 3 and the sub-reflector 2 projected onto a plane including the aperture of the main reflector 1 is within the aperture, the mechanical dimensions of the antenna are the aperture diameter of the main reflector 1. matches. Comparing this with the above-described conventional offset reflector antenna in which the aperture diameter of the main reflector t is made equal, the mechanical dimensions of the entire antenna are smaller in the former. Also, the light beam emitted along the central axis of the primary radiator 3 is at the point SL! on the sub-reflector 2! The radio wave reflected by the sub-reflector 2 enters the primary radiator 3, compared to the case of the conventional axisymmetric reflector antenna described above. Power is reduced and VSWR characteristics are improved. In the reflector antenna shown in FIGS. 1(a) and (l) explained above, the central axis direction of the primary radiator 3 coincides with the direction that equally divides the angle from point F2 to the peripheral part of the sub-reflector 2. An example is shown below.

FIGS. 2(a) and 2(b) are a side view and a front view showing a schematic configuration of a reflector antenna according to another embodiment of the present invention. Another embodiment of the invention includes a primary radiator 3
The central axis direction of the main reflecting mirror 1 is made to coincide with the mirror axis direction of the main reflecting mirror 1. In this case, since the mechanical axis of the primary radiator 3 and the electrical axis of the antenna coincide, the direction of the radiation beam of the antenna can be easily adjusted. The description of the other configurations and operations will be omitted since they are almost the same as those of the above-described embodiment.

In the above embodiment, a Cassegrain antenna type is shown in which the main reflector 1 is a parabola and the sub-reflector 2 is a hyperboloid. A Gregorian antenna format may also be used. Alternatively, the antenna may be of a mirror-finished antenna type composed of non-quadratic curved surfaces of the main reflecting mirror 1 and the sub-reflecting mirror 2.

[Effects of the Invention] As described above, according to the reflector antenna of the present invention, the primary radiator and the sub-reflector can be projected onto a plane including the aperture plane of the main reflector, or are located within the aperture plane. , and because the primary radiator and sub-reflector are arranged offset from the center of this aperture, the mechanical dimensions of the antenna can be reduced, and the shielding of radio waves by the sub-reflector and support column can be reduced. This has excellent effects such as minimizing deterioration of radiation characteristics and improving deterioration of VSWR characteristics due to waves reflected by the sub-reflector.

[Brief explanation of the drawing]

FIGS. 1(a) and (1) are side and front views showing the schematic configuration of a reflector antenna which is one embodiment of the present invention, and FIGS. 2(a) and (b) are another embodiment of the present invention. Side view and front view showing the schematic configuration of the reflector antenna as an example, Part 3
Figures (a) and (b) are side and front views showing the schematic configuration of a conventional axisymmetric reflector antenna, and Figures 4 (a) and (b) are schematic configurations of a conventional offset reflector antenna. FIG. 2 is a side view and a front view. In the figure, 1...Main reflecting mirror, 2...Sub reflecting mirror, 3
...Primary radiator, 4...Support column. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a reflector antenna composed of a main reflector, a sub-reflector, and a primary radiator, the primary radiator and sub-reflector are
The primary radiator and the sub-reflector are arranged so that the entire map projected onto a plane including the aperture of the main reflector is within the aperture and is offset from the center of the aperture. reflector antenna.