JPS63212206A - Multiple mode horn antenna - Google Patents

Abstract

PURPOSE:To attain beam shaping and suppression of side lobe nearly independently as to two orthogonal linearly polarized waves whose frequency differs by changing discontinuously independently in two axis directions where the spread angles of the inner walls are made orthogonal. CONSTITUTION:The cross section is made square, the spread angle of the inner wall is changed discontinuously at least at one position, the number of discontinuous changes at each of two pairs of inner wall pairs consisting respectively of two opposed inner walls respectively, their positions, and the changes x1, x2, y1, y2 of the spread angle at each position, at least one of them, are made different. Thus, as to two orthogonal linearly polarized waves with different frequencies, the beam shaping and side lobe suppression are attained, and the multiple mode horn antenna with ease of design and having a wide operationable frequency width in the linearly polarized waves is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-mode horn antenna, and particularly to a Cassegrain antenna for a satellite communication earth station.
The present invention relates to a multimode horn antenna suitable for the primary radiator of a parabolic antenna or a parabolic antenna.

[Conventional technology]

Antennas that combine a primary radiator consisting of a horn antenna and a Cassegrain reflector or a parabolic reflector are widely used in satellite communication earth stations and the like.

A horn antenna for linearly polarized waves for such applications has a beam width that is approximately equal in the plane in the direction of the electric field (hereinafter referred to as 8 planes) and the plane in the direction perpendicular thereto (hereinafter referred to as 8 planes); Two points are important: the level of play is low.

A pyramidal horn whose opening surface is square (square or rectangular);
For antennas and conical horn antennas, if the spread angle is uniform and there are no discontinuities, the width of the emitted linearly polarized beam is E.
It is known that there is a considerable difference between the surface and the H surface, and that the side rope level is particularly high on the E surface.

Changing the spread υ angle discontinuously, creating a step on the wall surface,
By installing an iris or attaching a dielectric material to the wall surface, a part of the fundamental mode wave in the horn (square TH wave in the case of a pyramidal horn antenna, circular TE11 wave in the case of a conical horn antenna) is converted into a mode. It converts and generates a higher-order mode wave, one of which (square TMB wave in the case of a pyramidal horn antenna, circular TM■ wave in the case of a conical horn antenna).
By combining the fundamental mode wave and the fundamental mode wave at a predetermined phase and amplitude ratio at the aperture plane, the beam width can be made almost equal in the E plane and the H plane (this is referred to as beam shaping hereinafter).
Various multi-mode horn antennas that simultaneously suppress side lobes have been proposed.

For example, Microwave Journal *1
3 [10] (1970-10) (US) P-41-4
No. 6 discloses a pyramidal multi-mode horn antenna, and JP-A-54-104759 describes a conical multi-mode horn antenna. In any of these conventional examples, the usable frequency width is narrow due to the restriction that the fundamental mode wave and the higher-order mode wave must be synthesized at a predetermined phase at the aperture surface.

By the way, in satellite communication, uplink and downlink use two waves with different frequencies with a frequency ratio of about 1.2 to 1.5, and these two waves are orthogonal to each other. Two linearly polarized waves are often used.

The above two conventional examples have a frequency ratio of 1.2 to 1.5.
It is impossible to sufficiently perform beam shaping and sidelobe suppression using two waves of different degrees.

Institute of Electronics and Communication Engineers Technical Research Report 1/P, 86-117 (1
986) describes a multimode horn antenna in which four irises are provided on a conical horn whose divergence angle is changed discontinuously at two locations. This conventional example uses a large number of 4 irises to increase the degree of freedom in design.
Beam shaping and sidelobe suppression are performed using two waves with a frequency ratio of about 1.2. However, design parameters such as the position at which the divergence angle changes, the amount of change in the divergence angle, and the position and height of each iris affect both of the two waves, making the design complicated and difficult. Also, when generating higher-order mode waves by changing the spread angle, the fundamental mode wave is hardly reflected at the change point, so the impedance characteristics are good. However, when generating higher-order mode waves at the iris, also reflects the fundamental mode wave, so when optimizing each design parameter, it is necessary to consider not only beam shaping and sidelobe suppression but also impedance characteristics. The usable frequency width at each of the two optimized frequencies is primarily constrained by impedance characteristics and becomes an extremely narrow band.

[Problem to be Solved by the Invention 3] As explained above, the conventional multimode horn antenna is complicated and difficult to perform beam shaping and sidelobe suppression for two linearly polarized waves that are orthogonal to each other and have different frequencies. The disadvantage is that it requires a detailed design, and the usable frequency width for each linearly polarized wave is narrow.

The purpose of the present invention is to enable beam shaping and sidelobe suppression for two linearly polarized waves that are orthogonal to each other and have different frequencies, to facilitate design, and to provide a wide usable frequency range for each linearly polarized wave. It is provided by a multi-mode horn antenna.

[Means for solving problems]

The multi-mode horn antenna of the present invention shapes a beam by combining a fundamental mode wave and a higher-order mode wave generated by mode converting a part of this fundamental mode wave at a predetermined phase and amplitude ratio at the aperture plane. In a multi-mode horn antenna that suppresses side ropes, the cross section is rectangular, the divergence angle of the inner wall is discontinuously changed at at least one place, and two pairs of inner walls each consisting of the two inner walls facing each other are formed. In each case, the number and each position of the discontinuous change and the bed at each n position are configured to differ by at least one of the nine angles of change.

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments.

FIG. 1 is a drawing showing a first embodiment of a multimode horn antenna of the present invention, in which (a) is a front view, (b) is a right side view, and (c) is a plan view.

1 is a feed waveguide whose cross section is square or rectangular; 2
is a square horn. The feed waveguide l feeds two mutually orthogonal fundamental mode waves (TEI (1 wave)) with different frequencies to the rectangular horn 2.The E-plane direction of each of these two TE10 waves is shown in FIG. As shown in (a), the directions are referred to as the X-axis direction and the Y-axis direction.

The spread angle of the rectangular horn 2 in the X-axis direction is discontinuously decreased by an angle x1 at a position of distance 11 from the opening surface 3, and is also discontinuously increased by an angle X- at a position of distance 12. Y
The spread angle in the axial direction is an angle y1 at a distance j3 from the opening surface 3, and an angle '/x at a distance 14.
Each decreases discontinuously.

The TE and o waves spread in the E-plane direction and generate TMl and waves due to discontinuous changes in the angle. Its amplitude is proportional to the amount of angle change, and the phase for the TE10 wave increases when the spread angle increases.
Delays by 0 degrees and advances by 90 degrees when decreasing (Micro
(See wave Journal 1 P, 41-42). H
The change in the spread angle in the plane direction is 'rMI, and the generation of waves can be ignored.

Therefore, the TE10 waves whose E plane is in the X-axis direction are each 1M1! at a distance It-It from the aperture surface 3! Waves are generated, and the phase of these 1Ml waves at the aperture surface 3 is mainly determined by the distance 1!1-12 and the sign of the spread angle. These two TMs, 2 waves (totally synthesized TMl! waves)
The distance 11°12 and the angle
By setting m, it is possible to beam-shape the linearly polarized wave emitted from the aperture surface 3 and whose E plane is in the X-axis direction, and to suppress side lobes.

Similarly, for linearly polarized waves whose E plane is in the Y-axis direction, beam shaping and side rope suppression can be achieved by setting the distance Is=It4 and the angle YtsY.

FIG. 2 is a drawing showing a second embodiment of the multimode horn antenna of the present invention, in which (a) is a front view and (b) is a right side view.

The embodiment shown in FIG. 2 is similar to the embodiment shown in FIG.
It is constructed by adding. The dielectric 4 is a rectangular horn 2
They are attached to a pair of inner walls facing each other and intersecting the X-axis so as to be symmetrical with respect to the Y-axis. The dielectric 4 mounted in this manner generates waves from 1+B, whose E plane is in the X-axis direction, TMI from waves, and TEL, whose E plane is in the Y-axis direction.
It hardly cares about the waves.

A wave 'i' M 1 is also generated by the dielectric 4 from the TE10 wave whose E plane is in the Depending on the settings? ! Thus, the degree of freedom in designing beam shaping and sidelobe suppression of linearly polarized waves in which the E axis is in the X axis direction can be increased.

The present invention has been described in detail above for the case where the υ angle spreads at two locations in the X-axis direction and in the Y-axis direction and changes discontinuously. Can be set independently to any number.

〔Effect of the invention〕

As explained in detail above, the multi-mode horn antenna of the present invention is capable of forming two straight lines that are orthogonal to each other and have different frequencies by independently and discontinuously changing the spread angle of the inner wall in two mutually orthogonal axes directions. Since beam shaping and sidelobe suppression can be performed almost independently for each polarized wave, the design is easy even when the frequency ratio of the two directly polarized waves is large. Because it generates higher-order mode waves, it has good impedance characteristics and a wide usable frequency range for each linearly polarized wave.Furthermore, it does not require complicated processing such as installing an iris. This has the effect of lower manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a first embodiment of the multi-mode horn antenna of the present invention, in which (a) is a front view, (b) is a right side view, (C) is a top view, and FIG. 2 is a drawing showing Example 2, (a)
is a front view, and Φ) is a right side view. 1... Feed waveguide, 2... Rectangular horn, 3... Opening surface. Agent Patent Attorney Susumu Uchihara 1st Figure Z Diagram

Claims (2)

[Claims] (1) Shape the beam and suppress side lobes by combining the fundamental mode wave and the higher-order mode wave generated by mode converting a part of this fundamental mode wave at a predetermined phase and amplitude ratio at the aperture plane. In the multi-mode horn antenna, the cross section is rectangular, the spread angle of the inner wall is discontinuously changed at at least one place, and the discontinuous angle is changed at each of two pairs of inner walls each consisting of the two inner walls facing each other. A multimode horn antenna characterized in that at least one of the number of changes, each position, and the amount of change in the spread angle at each position is different. (2) The multi-mode horn antenna according to claim 1, wherein a dielectric material is attached to a part of at least one of the two pairs of inner walls.