JPS5943005B2 - circularly polarized antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circularly polarized antenna having a circularly polarized wave generator, and particularly to an improvement in a circuit for preventing deterioration of elliptical polarization.

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a conventional circularly polarized antenna. In the figure, 1 is a conical horn, 2 is a circularly polarized wave generator, 3 is a circular waveguide, and 4 is a circular waveguide 3. The radio wave absorber plate 5 inserted in the center is a rectangular-circular waveguide converter.

Assuming that the electromagnetic wave input to the rectangular-circular waveguide converter 5 is a linearly polarized electromagnetic wave whose electric field has a plane of polarization in the direction shown by the arrow 6 in FIG. 1, this electric field is a radio wave. Since the electric field is perpendicular to the absorber plate 4, it is guided to the circularly polarized wave generator 2 with almost no loss, and becomes, for example, a right-handed circularly polarized wave, which is radiated from the conical horn 1.

By the way, in general, electromagnetic waves are reflected at the connection point between the circularly polarized wave generator 2 and the conical horn 1 and at the open end of the conical horn 1, and the reflected electromagnetic waves are transmitted to the circularly polarized wave generator 2 and the circular guide, contrary to the incident electromagnetic wave. The wave tube 3 advances in the direction of the rectangular-circular waveguide blue tube device 5.

This reflected wave then returns to the circular waveguide 3 as a linearly polarized wave (referred to as a cross-polarized wave component) having a polarization plane perpendicular to the polarization plane of the incident wave as shown by the arrow 6 by the circularly polarized wave generator 2. It is effectively absorbed by the radio wave absorber plate 4.

If there is no radio wave absorber plate 4, this cross-polarized wave component will be reflected again by the rectangular-circular waveguide converter 5 and the circular conductor tube 3.
The circularly polarized wave is turned by the circularly polarized wave generator 2 in the direction opposite to the direction of rotation of the main circularly polarized wave (left rotation in the above embodiment), and is radiated from the conical horn 1 with an elliptical polarization rate. deteriorate.

If the reflection coefficient at the output point of the circularly polarized wave generator 2, that is, the reflection coefficient seen from the input point of the conical horn 1, is Fl, and the reflection coefficient in the input direction of the circularly polarized wave generator 2 is F2, then the elliptical polarization coefficient is obtained. The deterioration ΔAR of is expressed as .

In the configuration shown in Fig. 1, for example, 7'1 = 0.1 (standing wave rate VSWR = 1.22),
In addition, the circuit of the rectangular-circular waveguide converter 5 is cut off for crossed polarization components and complete reflection occurs, so F2-1
Then, from equation (1), △AR=0.87 (d, b
).

Since recent high-performance antennas are required to have a ΔAR of 0.4 db or less, the radio wave absorber plate 4, which is a circuit that prevents deterioration of the elliptical polarization factor, is essential.

As the radio wave absorber plate 4, an absorber plate with a resistive film coated on a dielectric substrate such as mica with a thickness of about 0, ix to 2 mm is usually used, so that it is inserted even for the main polarized wave component. In addition, since all reflected waves are absorbed, there are inconveniences such as burning of the absorber plate when used with high power, and when applied to satellite antennas, there is a risk of shock and vibration during launch. It has been difficult to select a durable absorber plate and how to attach it, resulting in a decrease in reliability.

The purpose of this invention is to eliminate the above-mentioned drawbacks of conventional antennas, and to achieve this purpose, a polarization splitter loaded with a radio wave absorber is used. Explain.

FIG. 2 is a schematic sectional view showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same or corresponding parts and perform the same operations.

7 is a polarization splitter composed of 7at7b*7c;
7b is provided in the main waveguide section Ia, has a polarization plane perpendicular to the polarization plane shown by arrow 6, and is directed from the direction of the circularly polarized wave generator 2 toward the main waveguide section 7a. 7c is a branching waveguide portion of the polarization splitter 7, 8 is a lid of the branching waveguide portion 7c, and 9 is a radio wave absorber.

The electromagnetic waves that are reflected and input from the conical horn 1 to the conical wave generator 2 in the same manner as explained with reference to FIG. However, this cross-polarized wave component is reflected by the metal shorting plate 7b at the center of the main waveguide 7a and is transmitted to the branch conductor tube 7c.
It is absorbed by the radio wave absorber 9.

As explained above, according to the present invention, there is no need to provide an absorber in the waveguide through which the main polarized wave component passes, so insertion loss is reduced, and a large block can also be used for the radio wave absorber. This makes it possible to use large amounts of power.

Also, when used onboard a satellite, if a glue-like material made of magnetic powder hardened with resin is used as a radio wave absorber, it can be attached with screws and adhesive, so it has sufficient strength and reliability. This enables a circuit configuration with high performance.

As described above, the circularly polarized antenna of the present invention has extremely excellent performance, especially as an antenna mounted on an artificial satellite.

In the embodiment shown in FIG. 2, a case has been described in which the output of the circularly polarized wave generator 2 is directly connected to the conical horn 1, but an arbitrary waveguide device may be connected between the circularly polarized wave generator 2 and the electromagnetic horn. radiates circularly polarized waves from an antenna system that uses the electromagnetic horn as a primary radiator and has a reflector that focuses and reflects radio waves from the electromagnetic horn. Needless to say, this invention can also be used in such cases.

Furthermore, it is clear that similar effects can be obtained in the case of a dual mode horn antenna in which, for example, a higher-order mode generator or the like is inserted between the circularly polarized wave generator 2 and the conical horn 1.

Further, in the above description, the case where the circularly polarized antenna shown in FIG. 2 is used for transmitting radio waves has been described, but it goes without saying that it can be used similarly for receiving radio waves.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of the configuration of a conventional circularly polarized antenna, and FIG. 2 is a schematic sectional view showing an embodiment of the present invention. In the figure, 1 is a conical horn, 2 is a circularly polarized wave generator, 5 is a rectangular-circular waveguide converter, 7 is a polarization splitter, 7a is the main waveguide part of the polarization splitter 7, and 7b is a short circuit plate. , 7c is a branch waveguide portion of the polarization splitter 7, 8 is a lid, and 9 is a radio wave absorber. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A circularly polarized wave generator that inputs a linearly polarized electromagnetic wave having a predetermined plane of polarization and converts it into a circularly polarized wave having a predetermined turning force direction, and an electromagnetic horn connected to the output side of this circularly polarized wave generator. ,
The polarization splitter is connected to the input end of the circularly polarized wave generator, and the polarization splitter includes a short circuit plate that reflects linearly polarized electromagnetic waves having a polarization plane perpendicular to the predetermined polarization plane. What is claimed is: 1. A circularly polarized wave antenna comprising: a main waveguide section; and a branch waveguide section, wherein a branch waveguide section is provided with a radio wave absorber that absorbs electromagnetic waves reflected by the short circuit plate.