JPS63107207A - Composite mode horn antenna - Google Patents

Abstract

PURPOSE:To obtain excellent radiation characteristics and to decrease a standing wave ratio by interposing a straight tapered waveguide which feeds a basic mode smoothly without generating an unnecesary high-order mode between a feed waveguide and a high-order mode generation part. CONSTITUTION:The internal diameter of a TM11 mode generation part 2 on the side of the feed waveguide 3 is set larger than the internal diameter of the feed waveguide 3 and smaller than 1.22 times as large as the wavelength at the highest frequency of, for example, an in-use frequency band, and the straight tapered waveguide 7 which connects the internal walls of the feed waveguide 3 and TM11 mode generation part smoothly is interposed between both. Consequently, the generation of a TM11 mode at both-end discontinuous parts is suppressed and while the influence upon the generation quantity and phase quantity of the specific TM11 mode is suppressed, the discontinuity of the connection part between the feed waveguide and straight tapered waveguide and the connection part between the straight tapered waveguide and TM11 mode generation part is made small and the reflection of the TE11 mode is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is used as the primary horn of a reflector antenna or as a single horn antenna, and is used as a primary horn of a reflecting mirror antenna or as a single horn antenna. This invention relates to a multi-mode horn antenna that is excited by a plurality of modes.

[Prior Art] FIGS. 3 and 4 are side sectional views showing the configuration of a conventional multi-mode horn antenna as disclosed in, for example, Japanese Patent Publication No. 56-9047. In the figures, (1) is a conical horn, (2) is a TM1□ mode generator connected to this conical horn, and (3) is a feeding waveguide connected to this TM machine and mode generator. FIG. 3 is a side cross-sectional view of the flare type multi-mode horn antenna in which the mode generating section (2) is constituted by a straight circular waveguide (4) and a flare (5). Figure 4 shows a flare iris in which the TM11 mode generating section (2) is composed of a straight circular waveguide (4), a flare (5), and an iris (6) provided on the inner wall of the straight circular waveguide (4). FIG. 2 is a side sectional view of a multi-mode horn antenna.

A conventional multi-mode horn antenna is constructed as described above. For example, in the flare-type multi-mode horn antenna shown in FIG. Part of the flare (5)
and the connection part of the straight circular waveguide (4) and the straight circular waveguide (
4) and the conical horn (1) at the discontinuous part
11 mode. The dimensions of the conical horn (1) are determined by obtaining a desired radiation pattern, and the inner diameter of the straight circular waveguide (4) is determined by minimizing the generation of unnecessary higher-order modes. Therefore, by optimally selecting the length of the straight circular waveguide (4) and the angle of the flare (5), it is possible to obtain the desired generation amount and phase amount of the TM□□ mode. A radiation pattern with small components can be obtained.

Further, in the flare iris type multi-mode horn antenna shown in FIG. 4, in addition to the flare type antenna described above, the TM11 mode is generated from each iris (6). The TM1□ mode propagated from the iris (6) in the direction of the 1-conical horn (1) and the direction of the flare (5), respectively, and
) and then propagates in the direction of the conical horn (1). Therefore, by selecting these dimensions,
A desired amount of T M11 mode generation and phase can be obtained over a wide frequency band. A flare iris type multimode horn antenna is characterized in that it can obtain better radiation characteristics within a wide frequency band compared to a flare type multimode horn antenna.

[Problems to be Solved by the Invention] In such a multi-mode horn antenna, the angle of the flare (5) of the TM Yu□ mode generating section (2) connected to the feeding waveguide (3) is set at a desired angle. Since it is determined by obtaining the generation amount and phase amount of the TMo mode, if the flare angle is large, the matching with the feeding waveguide (3) will be poor, and the standing wave ratio will be poor. Furthermore, if the angle of the flare (5) is made small in order to improve the standing wave ratio, there is a problem in that the desired amount and phase of the T M 1□ mode cannot be obtained.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a multi-mode horn antenna having good radiation characteristics and a small standing wave ratio.

[Means for Solving the Problems] The multi-mode horn antenna according to the present invention has an inner diameter of the feeding waveguide side of the TM construction and mode generation section larger than the inner diameter of the feeding waveguide, and a TM11 mode. A size that does not allow propagation, for example, 1.2 of the wavelength of the highest frequency in the frequency band used
The diameter of the feeding waveguide and the TM, !
A linear tapered waveguide is inserted between the mode generating portions to smoothly connect the inner walls of the two.

[Function] In this invention, the inner diameter of the linear tapered waveguide is TM□
Since the size is such that the □ mode does not propagate, the generation of the TM1□ mode at the discontinuous portions at both ends is suppressed, and the power supply conduction is maintained while minimizing the influence on the amount and phase of the predetermined TM1□ mode. It is possible to reduce the size of discontinuity at the connection portion between the wave tube and the linear taper waveguide and the connection portion between the linear taper waveguide and the TML, mode generation section,
As a result, the reflection of the TEL mode becomes smaller.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a side cross-sectional view showing one embodiment in which the present invention is applied to a flare type multi-mode horn antenna, and Fig. 2 is another embodiment in which the present invention is applied to a flare iris type multi-mode horn antenna. FIG. In the figure, (1) to (6) are similar to the conventional multi-mode horn antenna shown in Figs. 3 and 4, and (7) is the structure of the feeding waveguide (3) and flare (5). A straight tapered waveguide is inserted between the two.

In this example, the flare (
The inner diameter of the feed waveguide side of 5) is the inner diameter of the feed waveguide (3).
) inner diameter. a linear tapered waveguide that is larger and has a diameter smaller than 1.22 times the wavelength λm of the highest frequency in the used frequency band, and that smoothly connects the in-plane wall of the feeding waveguide (3) and the flare (5); (7) is provided.

Generally, a higher-order mode that can be propagated in a straight circular waveguide whose inner shape is given by D has a wavelength λ that satisfies the following equation (1). That is, kaλ D>□ (2) π ka is the root of the characteristic equation, and is given as follows corresponding to each mode.

From these equations, we can see that the TM1□ mode is in the linear tapered waveguide (
To prevent 7) from propagating, add this and flare (5)
It can be seen that the inner diameter D of the connecting portion with the frequency band can be made smaller than ka,/π times the wavelength λm of the highest frequency in the frequency band used, that is, 1.22 times.

Therefore, the TEo mode propagating from the feeding waveguide (3) toward the conical horn (1) side is smoothly propagated to the T M x i mode generating section (2) by passing through the linear tapered waveguide (7). , reflection can be reduced.

That is, compared to the conventional structure in which the feed waveguide (3) directly propagates to the TM and mode generation section (2), the connection between the feed waveguide (3) and the straight tapered waveguide (7) The size of the discontinuity at the connection between the linear taper waveguide (7) and the flare (5) can be reduced. Since the inner diameter of the continuous portion can be increased and the flare angle can be reduced, the standing wave ratio can be improved and reflection can be reduced.

Furthermore, by making the inner diameter of the linear tapered waveguide (7) smaller than 1.22 times the wavelength of the highest frequency in the used frequency band, Since the propagation of the TM11 mode can be suppressed, the influence on the generation amount and phase amount of the TM11 mode can be reduced, and a desired radiation pattern can be obtained.

Note that, although the case where one linear taper waveguide is used has been described above, the same effect can be obtained even if a plurality of linear tapered waveguides are connected. Furthermore, although the case of a flare type or flare iris type multi-mode horn antenna has been described, similar effects can be obtained by using other types of multi-mode horn antennas.

[Effects of the Invention] According to the present invention, T Ml can be transmitted between the feeding waveguide, T Ml, and the mode generating section without generating unnecessary higher-order modes.
By inserting a linear tapered waveguide that can feed the E t 1 mode smoothly, a multi-mode horn antenna with low reflected power and a low standing wave ratio can be obtained without deteriorating the good radiation pattern. There is.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment of the invention, and FIG. 2 is a side sectional view showing another embodiment of the invention. FIG. 3 is a side sectional view showing a conventional flare type multi-mode horn antenna, and FIG. 4 is a side sectional view showing a conventional flare iris type multi-mode horn antenna. In the figure, (1) is a conical horn, (2) is a T M11 mode generator, (3) is a feeding waveguide, (4) is a straight circular waveguide, (5) is a flare, (6) is an iris, (7) is a straight tapered waveguide. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (4)

[Claims] (1) A conical horn, a feeding waveguide that feeds electromagnetic waves in the fundamental mode (TE_1_1), and a TM_1_1 mode inserted between the conical horn and the feeding waveguide and transmitting the TM_1_1 mode as a higher mode of the fundamental mode. TM_1_1 that occurs
It consists of a mode generator, a basic mode and TM_1_
In a multi-mode horn antenna excited in one mode,
The inner diameter of the feeding waveguide side of the TM_1_1 mode generating section is larger than the inner diameter of the feeding waveguide, and the TM_1_1
A multi-mode horn antenna characterized in that a linear tapered waveguide is inserted between the feeding waveguide and the TM_1_1 mode generating section, the linear tapered waveguide having a size that prevents propagation of the _1 mode, and smoothly connecting the inner walls of the two. (2) A patent claim in which the inner diameter of the feeding waveguide side of the TM_1_1 mode generating section is larger than the inner diameter of the feeding waveguide and smaller than 1.22 times the wavelength of the highest frequency in the frequency band used. A multi-mode horn antenna according to scope 1. (3) The TM_1_1 mode generating section includes a flare whose one end is connected to the linear tapered waveguide, one end of which is connected to the flare, and the other end of which is connected to the conical horn, and a straight line that propagates the fundamental mode and the TM_1_1 mode. A multi-mode horn antenna according to claim 1 or 2, which comprises a circular waveguide. (4) The multi-mode horn antenna according to claim 3, wherein the straight circular waveguide of the TM_1_1 mode generating section has an iris for generating the TM_1_1 mode on its inner wall.