JPH09102708A - Primary radiator for parabolic antenna - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To suppress the generation of elliptical polarization generated in an electromagnetic horn portion having an elliptical aperture plane, and to provide excellent cross polarization characteristics. An elliptical aperture electromagnetic horn having an elliptical aperture surface.
In the parabolic antenna primary radiator having 5, the phase shift circuit section 24 functioning as a rotational polarization generator is provided between the elliptical opening of the elliptical aperture electromagnetic horn 25 and the feeding section 22. The phase shift circuit section 24 has a dielectric plate 23 having a dielectric constant and a shape that causes a phase difference that cancels out a propagation phase difference in each axial direction due to a difference between the major axis and the minor axis of the elliptical aperture electromagnetic horn 25. Have.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primary radiator for a parabolic antenna having an electromagnetic horn having an elliptical opening surface.

[0002]

2. Description of the Related Art Generally, in a parabolic antenna, when a reflecting mirror is formed into an ellipse or a rectangle so that the opening surface is an ellipse, the primary radiator thereof is an electromagnetic horn having an elliptical opening portion according to the shape of the reflecting mirror surface. Is used.

FIG. 3 shows the external appearance of a general parabolic antenna. FIG. 3 shows a parabolic antenna having a primary radiator provided with an electromagnetic horn 12 having an elliptic opening with respect to the reflecting mirror 11. The electromagnetic horn 12 is supported by a support arm 13 at a predetermined position which is a focus of the parabolic surface of the reflecting mirror 11.

By the way, when the electromagnetic horn 12 having an elliptical opening as shown in FIG. 3 is used as a primary radiator and the incident electric field on the electromagnetic horn 12 is linearly polarized, the plane of polarization of the incident electric field is electromagnetic. When the opening of the horn 12 is tilted with respect to the major axis or minor axis of the ellipse, elliptical polarization is generated due to the difference in propagation phase due to the difference between the major axis and the minor axis. When this elliptical polarization occurs, the cross polarization characteristics deteriorate.

[0005]

As described above, in the conventional primary radiator for parabolic antenna, when the shape of the opening portion of the electromagnetic horn is elliptical, the long axis of the opening surface having an elliptical plane of polarization with respect to the electromagnetic horn. When a linearly polarized wave that is inclined with respect to the direction or the short axis direction is incident, an elliptically polarized wave is generated due to the propagation phase difference due to the difference between the long axis and the short axis of the electromagnetic horn portion. That is, the cross polarization characteristics were significantly deteriorated by the elliptically polarized waves.

The present invention has been made in consideration of the above circumstances, and suppresses the generation of elliptical polarization generated in an electromagnetic horn portion having an elliptical aperture surface, and provides a parabolic antenna having excellent cross polarization characteristics. A primary radiator for use is provided.

[0007]

The present invention relates to a primary radiator for a parabolic antenna having an electromagnetic horn having an elliptical opening surface as a rotating polarization generator between the opening and the feeding portion of the electromagnetic horn. A feature is that a functioning phase shift circuit section is provided.

Further, the phase shift circuit portion has a dielectric constant and a shape that causes a phase difference that cancels a propagation phase difference in each axial direction due to a difference between the long axis and the short axis of the electromagnetic horn. Characterized by having a body.

According to this structure, even if a linearly polarized wave which is inclined with respect to the axial direction of the electromagnetic horn having an elliptical aperture surface is input, the propagation phase shift difference caused by the difference in the waveguide diameter of the electromagnetic horn portion is input. The generation of the elliptical polarization generated in the electromagnetic horn is suppressed by passing the phase-shifting circuit section having the function of generating the rotational polarization (circular polarization, elliptical polarization) that cancels each other.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a primary radiator for a parabolic antenna according to this embodiment.
FIG. 1 (a) is a diagram showing an opening of a primary radiator, FIG. 1 (b).
Shows a perspective view.

As shown in FIG. 1, the primary radiator for a parabolic antenna according to this embodiment has a feeding portion 22 including a feeding probe 21, a phase shift circuit portion 24 including a dielectric plate 23, and an elliptic aperture electromagnetic horn portion 25. It is composed by.

In the present embodiment, it is assumed that the power feeding portion 22 is installed so as to inject a linearly polarized wave with an inclination with respect to the major axis and the minor axis of the elliptical aperture surface 26 of the elliptical aperture electromagnetic horn 25.

The phase shift circuit section 24 includes the inserted dielectric plate 2
By the action of 3, an operation is performed between the elliptical aperture surface 26 of the elliptical aperture electromagnetic horn 25 and the feeding portion 22 as a rotary polarization generator. That is, the dielectric plate 23 rotates the input linearly polarized wave by rotating the polarized wave (elliptical polarized wave) in which the propagation phase difference in each axial direction due to the difference between the major axis and the minor axis of the elliptical aperture electromagnetic horn 25 is canceled. , Circularly polarized wave) and has a dielectric constant ε _r and a shape.

Next, the function and effect of the primary radiator for the parabolic antenna shown in FIG. 1 will be described. Here, it will be described as the transmitting side. The input power (linearly polarized wave) passes through the circular waveguide and proceeds to the phase shift circuit section 24. The electric power incident on the phase shift circuit section 24 is affected by the dielectric plate 23 inserted therein.

That is, the component of the electric field plane of the electric power incident on the phase shift circuit section 24 parallel to the dielectric plate 23 is affected by the dielectric constant ε _r of the dielectric plate 23, and the phase shift circuit section is affected. The in-tube wavelength when passing through 24 is converted to X times based on the dielectric constant ε _r shown below.

[0016]

(Equation 1)

Since the permittivity ε _r always takes a value larger than 1, the guide wavelength becomes short. Further, the component of the electric field surface of the electric power incident on the phase shift circuit section 24 perpendicular to the dielectric plate 23 passes through the phase shift circuit section 24 with almost no influence of the dielectric plate 23.

The two electric field components that have passed through the phase shift circuit section 24 have a certain phase difference due to the shift in the guide wavelength caused by passing through the dielectric plate 23. Therefore, elliptically polarized waves are generated by combining two orthogonal electric field components. That is, the phase shift circuit 24 includes the dielectric plate 23.
By the action of, the incident linearly polarized wave is converted into the elliptically polarized wave.

Further, the permittivity ε of the dielectric plate 23 to be inserted is
By appropriately selecting _r and the shape, it is possible to generate circularly polarized waves having a good axial ratio instead of elliptical polarized waves. The electric power that has passed through the phase shift circuit section 24 advances to an elliptic aperture electromagnetic horn 25 having an elliptical aperture surface 26. The electric power incident on the elliptical aperture electromagnetic horn 25 has different in-tube wavelengths on the plane parallel to the major axis and the plane parallel to the minor axis of the elliptical aperture electromagnetic horn 25. That is, compared with the electric field surface parallel to the major axis of the elliptical aperture electromagnetic horn portion 25, the electric field surface parallel to the minor axis has a smaller waveguide diameter related to the in-tube wavelength, so that the in-tube wavelength in the elliptical horn is longer. Become. Therefore, in the elliptical aperture electromagnetic horn 25, a propagation phase difference occurs in each axial direction due to the difference between the long axis and the short axis.

The elliptical aperture electromagnetic horn 25 is constructed so that the propagation phase difference caused by the difference in each axis cancels the phase difference generated when passing through the dielectric plate 23 in the phase shift circuit section 24. Therefore, the elliptically polarized wave from the phase shift circuit section 24 is converted into the linearly polarized wave of the same polarization plane fed by the feeding section 22.

That is, the shape of the elliptical electromagnetic horn 25 and the permittivity ε _r and shape of the dielectric plate 23 are configured so as to cancel the phase difference generated in each, so that the parabolic antenna has a primary radiator with an elliptical shape. Opening surface 2
Even if a linearly polarized wave having an electric field plane (polarization plane) inclined with respect to the long axis and the short axis of the electromagnetic horn is used, the electromagnetic wave emitted from the primary radiator is elliptical. It is possible to radiate linearly polarized waves without making them polarized waves.

In the above description, the transmission side is described. However, when the transmission side is used, the following is performed. When a linearly polarized wave is incident on the elliptical aperture electromagnetic horn 25, the polarization plane of the incident radio wave (incident electric field polarization plane 27) is on the major axis and minor axis of the elliptical aperture surface 26, as shown in FIG. When tilted with respect to each other, the electric wave that has passed through the elliptical aperture electromagnetic horn 25 has an elliptical polarization (a circular polarization in a special case) having a phase difference between the incident electric field short axis component 28 and the incident electric field long axis component 28. And enters the phase shift circuit section 24.

Also in the phase shift circuit section 24, a phase difference occurs between a component parallel to the dielectric plate 23 inserted therein and a component perpendicular thereto. Here, the shape of the elliptical aperture electromagnetic horn 25,
When the permittivity ε _r and the shape of the dielectric plate 23 are configured so as to cancel out the phase difference generated in each, the radio wave that has passed through the phase shift circuit section 24 is eventually converted into a linearly polarized wave and is fed to the feeding section 22. Will be entered.

In the primary radiator for the parabolic antenna shown in FIG. 1, if the elliptical aperture electromagnetic horn 25 and the feeding portion 22 are not provided and the phase shifting circuit portion 24 is not provided, elliptical polarized waves are directly input to the feeding portion 22. As a result, the cross polarization characteristic is significantly deteriorated. However, as described above, by providing the phase shift circuit section 24 having the dielectric plate 23 between the elliptical aperture electromagnetic horn 25 and the power feeding section 22, the elliptical aperture electromagnetic horn 25 is provided with a biased angle with respect to the major axis and the minor axis. Even if a linearly polarized wave having a wavefront is incident, the power supply unit 22 can be input with the linearly polarized wave instead of the elliptically polarized wave, and the cross polarization characteristic is not deteriorated.

FIG. 2 shows the measurement results of the cross polarization characteristics of the primary radiator for a parabolic antenna according to the present invention. FIG.
In (a), the phase shift circuit portion 24 is not provided, and the electric field surface of the electric power incident on the power feeding portion 22 is inclined by 20 ° with respect to the major axis of the elliptical opening surface 26 of the elliptical opening electromagnetic horn 25, and the crossing at that time is performed. This is a measurement of the polarization level (conventional configuration).

From these results, it can be seen that there is a significant deterioration of about -9 dB in the 0 ° direction. This is because the major axis of the elliptical aperture surface 26 and the electric field surface of the incident electric power are inclined as described above, so that elliptical polarized waves are generated in the elliptical horn portion and are directly incident on the power feeding portion 22, so that the crossing occurs. The polarization characteristics have deteriorated.

FIG. 2 (b) is a cross polarization level measurement result of the primary radiator for the parabolic antenna according to the present invention. This measurement result is such that a phase shift circuit section 24 having a dielectric plate 23 is further provided in the configuration from which the measurement result shown in FIG. It is operated and measured.

In FIG. 2B, the cross polarization level is about −34 dB in the 0 ° direction.
It can be seen that it is significantly improved compared to the measurement result shown in (a).

[0029]

As described above in detail, according to the present invention, an electromagnetic horn having an elliptical aperture plane is used as a primary radiator of a parabolic antenna, and a plane of polarization inclined with respect to the major axis and the minor axis of the electromagnetic horn is used. Even if you input the linearly polarized wave that you have, by passing through the phase shift circuit section that has the function of generating the rotationally polarized wave that cancels the phase shift difference caused by the difference in the waveguide diameter of the electromagnetic horn section, It is possible to suppress the generation of elliptically polarized waves that occur and to obtain excellent cross polarization characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a primary radiator for a parabolic antenna according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross polarization characteristic measurement result for explaining the function and effect of the primary radiator for the parabolic antenna in the present embodiment.

FIG. 3 is a diagram showing an external configuration of a general parabolic antenna.

[Explanation of symbols]

 22 ... Feeding part 23 ... Dielectric plate 24 ... Phase shift circuit part 25 ... Elliptical aperture electromagnetic horn 26 ... Elliptical aperture surface

Claims (2)

[Claims] 1. A primary radiator for a parabolic antenna having an electromagnetic horn having an elliptical opening surface, wherein a phase shift circuit section functioning as a rotational polarization generator is provided between the opening section of the electromagnetic horn and a feeding section. A primary radiator for a parabolic antenna, which is characterized in that 2. The phase shift circuit unit has a dielectric constant and a shape that causes a phase difference that cancels a propagation phase difference in each axial direction due to a difference between a long axis and a short axis of the electromagnetic horn. The primary radiator for a parabolic antenna according to claim 1, wherein the primary radiator has a body.