JPS59194512A - Parabolic antenna for circular polarized wave - Google Patents

Abstract

PURPOSE:To obtain an economical antenna constituting its blocking only by the center part of parabolic antenna, to be used as a simple primary radiator system and reduced at its performance deterioration by generating circular polarized waves by an elliptical waveguide and supporting the primary radiation system. CONSTITUTION:When high frequency waves are to made incident to the elliptical waveguide 9 through a converter 8, the polarized wave direction is inclined by 45 deg. from the apse line direction (x axis) of the ellipse. The incident field can be decomposed to the apse line direction (x axis) and the minor axis (y axis). The transmission speeds of both the field components are different each other, so that pi/2 phase difference can be obtained at the final end of the ellipse waveguide 9. After passing through the final end, the field components irradiate a metallic plate 10 through the other converter 8. Since the size of the field components of both the x and y axes is equal and the phases are different each other by pi/2, the irradiation is regarded as circular polarized wave irradiation. After reflected by the metallic plate 10, the field components are sent to the parabola 1 through a radome 11. Although the incident waves are converted into reversed circular polarized waves, the reversed waves are returned to the original circular polarized waves after reflected by the parabola 1. The radome 11 acts as a supportor of the metallic plate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a circularly polarized parabolic antenna consisting of a primary radiation system and a parabola.

A conventional antenna of this type is shown in Figure 1.

Parabola (1) 9 conical horn (2) 9 circularly polarized wave generator (3
), a round-angle converter (4), a rectangular waveguide (5), and a down converter (6). Note that A is the central axis of the parabola (1). Here 1 circular polarization generator (3)
Generally, a quarter-wave plate is inserted into a circular waveguide. Further, the round angle converter (4) smoothly converts the rectangular aperture of the rectangular waveguide (5) and the circular aperture of the circularly polarized wave generator (3). Further, the down converter (6) has a built-in local oscillator and converts it to an intermediate frequency. The operation of this antenna will be explained in the case of transmission.

The high frequency of the TBIO mode from the rectangular waveguide (5) is transferred to the TEII of the circular waveguide that constitutes the polarization generator (3).
After being converted into a mode and passing through a quarter-wave plate, it becomes a circularly polarized wave, which is guided to the conical horn (2), irradiates the parabola (1), and is radiated into space. In this irradiation, blocking occurs because the rectangular waveguide (5) is in the direction of propagation of the radio waves. Furthermore, this rectangular waveguide (5)
It also becomes blocking when it is reflected by the parabola fil and goes into space. In addition, when heading towards this space, use 1 conical horn (2
), the circularly polarized wave generator (3), and the round angle converter (4) will also cause blocking, but since the position of this blocking will be at the center of the parabola, the amount will be smaller than that for the rectangular waveguide (5). less than. Therefore.

Blocking due to the rectangular waveguide (5) becomes a problem.

This causes performance deterioration such as a decrease in gain and an increase in sidelobe level. For this reason, there is an antenna shown in FIG. 2 as a configuration in which the rectangular waveguide (5) can be omitted. A conical horn (2), a single circularly polarized wave generator (3), and a round angle converter (4), which constitute the -order radiation system, are supported by a stay (7). In this case, blocking by the rectangular waveguide (5) in FIG. 1 is replaced by blocking by the stay (7).

In order to reduce performance deterioration due to fluctuations in the primary radiation system during strong winds, it is necessary to increase the width of the stay (7), which will increase blocking and reduce performance deterioration as in the case of Figure 1. There were drawbacks that occurred.

In order to reduce the amount of blocking, this invention uses a rear-feed type one-order radiation system in which the blocking position is at the center of the parabola.
By changing the configuration of the circular polarization generator.

This invention relates to an improvement of a circularly polarized parabolic antenna that does not include a round angle converter, and will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention.

(1) is a parabola, (6) is a down converter, (8)
is a converter between a circular waveguide and an elliptical waveguide, and C9) is an elliptical waveguide.

(1 [ is a metal plate, (ID is a radome.
As shown in the figure, the polarization direction is tilted by 45 degrees with respect to the major axis direction (X axis in FIG. 4) of the ellipse. This incident electric field can be decomposed into a major axis direction (X-axis) and a minor axis direction (y-axis). Since these two electric field components have different propagation velocities, the elliptical waveguide (9)
A phase difference of π/2 can be obtained at the end of . Then, after passing through this termination, it passes through another converter (8),
Irradiate the metal plate FIG.

In this case, the magnitudes of the electric field components in the X-axis and y-axis directions are equal and differ by π/2, which means that the irradiation is performed with circularly polarized waves. After being reflected by the metal plate Im, it passes through the radome 111 and heads toward the parabola (1). Here, it becomes a counter-rotating circularly polarized wave, but after being reflected by the parabola (1), it returns to the original circularly polarized wave. Note that the radome 1111 also has the role of supporting the metal plate tio+. In addition, the elliptical waveguide (9) is also a metal plate f1
01, supporting the radome C1υ. Since the two transducers (8) and the elliptical waveguide 19) are symmetrical with respect to the zx plane + Y'' plane, it is advantageous to manufacture them as one piece.

As described above, according to the present invention, since nine circularly polarized waves are generated by the elliptical waveguide and the -order radiation system is supported, blocking occurs only at the central part of the parabola, and simple primary radiation This has the advantage of providing a low-cost antenna with little performance deterioration.

[Brief explanation of the drawing]

1 and 2 are schematic configuration diagrams of a conventional antenna, and FIG. 3 is a schematic configuration diagram of an embodiment of the present invention. FIG. 4 is a diagram illustrating an embodiment of the present invention. In the figure, (1) is a parabola, (6) is a down converter,
(8) is a transducer, (9) is an elliptical waveguide, +1α is a metal plate, and fill is a radome. In the drawings, the same or corresponding parts are designated by the same reference numerals. Agent Masuo Oiwa

Claims (1)

[Claims] A circularly polarized parabolic antenna in which a feeding waveguide and a horn connected to the feeding waveguide are arranged along the central axis of the parabola, and a metal reflector is provided in front of the horn. The wave tube is an elliptical waveguide. A circularly polarized parabolic antenna characterized in that the reflector is fixed to the waveguide by a radome.