JPH0547122B2 - - Google Patents

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 combines the TE ₁₁ mode, which is the fundamental mode of a circular waveguide, with the higher order mode. This relates to a multi-mode horn antenna that is excited in multiple modes including:

[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.
is a conical horn, and 2 is connected to this conical horn
The TM ₁₁ mode generating section 3 is a feeding waveguide connected to this TM ₁₁ mode generating section. Figure 3 is above
FIG. 3 is a side sectional view of a flare type multi-mode horn antenna in which the TM ₁₁ mode generating section 2 is composed of a straight circular waveguide 4 and a flare 5. FIG. 4 shows the above-mentioned TM ₁₁ mode generating section 2 in 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 flare iris type multi-mode horn antenna constructed of.

A conventional multi-mode horn antenna is constructed as described above. For example, in the flare-type multi-mode horn antenna shown in _FIG . The portion is converted into the TM ₁₁ mode at the discontinuous portions at the junction between the flare 5 and the straight circular waveguide 4 and at the junction between the straight circular waveguide 4 and the conical horn 1. 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 ₁₁ mode, and to obtain a rotationally symmetric and cross-polarized wave component. A small radiation pattern can be obtained.

In addition, in the flared iris type multi-mode horn antenna shown in FIG. 4, the TM ₁₁ mode is generated from each iris 6 in addition to the above-mentioned flare type horn antenna. From the iris 6, the TM ₁₁ modes propagated in the direction of the conical horn 1 and the direction of the flare 5 are reflected inside the flare 5 and then propagated in the direction of the conical horn 1. Therefore, by selecting these dimensions, desired TM ₁₁ mode generation and phase amounts can be obtained over a wide frequency band. The flare iris type multi-mode horn antenna is different from the flare type multi-mode horn antenna.
A feature is that good radiation characteristics can be obtained within a wide frequency band.

[Problems to be Solved by the Invention] In such a multi-mode horn antenna, the angle of the flare 5 of the TM ₁₁ mode generating section 2 connected to the feeding waveguide 3 is determined so that the desired amount of TM ₁₁ mode is generated. In order to determine by obtaining the phase amount,
If the flare angle is large, matching with the feeding waveguide 3 will be poor and the standing wave ratio will be poor. Furthermore, when 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 of generation and phase of the TM ₁₁ 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 problem] The multi-mode horn antenna according to the present invention has the following features:
The inner diameter of the feeding waveguide side of the TM ₁₁ mode generation section is larger than the inner diameter of the feeding waveguide mentioned above, and the diameter is smaller than 1.22 times the wavelength of the highest frequency in the frequency band used, such as a size that does not propagate the TM ₁₁ mode. A linear tapered waveguide is inserted between the feeding waveguide and the TM ₁₁ mode generating section to smoothly connect the inner walls of the two.

[Operation] In this invention, since the inner diameter of the linear tapered waveguide is set to a size that does not allow the TM ₁₁ mode to propagate, the generation of the TM ₁₁ mode at the discontinuous portions at both ends is suppressed, and the predetermined TM ₁₁ mode is suppressed. The magnitude of the discontinuity at the connection between the feed waveguide and the linear taper waveguide and the connection between the linear taper waveguide and the TM ₁₁ mode generation section is minimized while minimizing the influence on the generation amount and phase amount. can be made smaller, thereby
Reflections in TE ₁₁ mode are reduced.

[Examples] Examples of the present invention will be described below with reference to the drawings.
FIG. 1 is a side sectional view showing an embodiment in which the present invention is applied to a flare type multi-mode horn antenna;
FIG. 2 is a side sectional view showing another embodiment in which the present invention is applied to a flare iris type multi-mode horn antenna. In the figure, 1 to 6 are the third
This antenna is similar to the conventional multi-mode horn antenna shown in FIGS.

In this embodiment, the TM ₁₁ mode generating section 2 is configured so that the inner diameter D ₁ of the flare 5 on the feeding waveguide side is larger than the inner diameter D ₀ of the feeding waveguide 3 and the wavelength λm of the highest frequency in the frequency band used. The diameter shall be smaller than 1.22 times,
A linear tapered waveguide 7 is provided that smoothly connects the inner walls of the feed waveguide 3 and the flare 5.

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

TE ₁₁ mode, ka ₀ = 1.84 TE ₁₁ mode, ka ₁ = 3.83 ... (3) From these equations, in order to prevent the TM ₁₁ mode from propagating in the linear tapered waveguide 7, this and the flare 5 must be combined. It can be seen that the inner diameter D ₁ of the connecting portion of the connecting portion may be made smaller than ka ₁ /π times, ie, 1.22 times, the wavelength λm of the highest frequency in the frequency band used.

Therefore, the TE ₁₁ mode propagating from the feeding waveguide 3 toward the conical horn 1 passes through the linear tapered waveguide 7 and is smoothly propagated to the TM ₁₁ mode generating section 2, reducing reflection. I can do it. That is, compared to the conventional structure in which the TM ₁₁ mode is directly propagated from the feed waveguide 3 to the TM 11 mode generating section 2, the connection between the feed waveguide 3 and the linear taper waveguide 7 and the connection between the linear taper waveguide 7 and the flare The size of the discontinuity at the connection part 5 can be reduced, and the inner diameter of the discontinuity part at the connection part between the linear taper waveguide 7 and the flare 5 can be increased to reduce the flare angle. It can improve the standing wave ratio and reduce reflection.

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, the TM ₁₁ mode generated at the connections at both ends of the linear tapered waveguide 7 can be reduced. Since the propagation of TM ₁₁ mode can be suppressed, the influence on the generation amount and phase amount of TM 11 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 multimode horn antenna has been described, the same effect can be obtained by using other types of multimode horn antennas.

[Effects of the Invention] According to the present invention, there is provided a linear tapered waveguide that can smoothly feed the TE ₁₁ mode between the feeding waveguide and the TM ₁₁ mode generating section without generating unnecessary higher-order modes. , it is possible to obtain a multi-mode horn antenna with low reflected power and a low standing wave ratio without deteriorating a good radiation pattern.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the present invention;
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 TM ₁₁ mode generator, 3 is a feeding waveguide, 4 is a straight circular waveguide,
5 is a flare, 6 is an iris, and 7 is a straight tapered waveguide. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A conical horn, a feeding waveguide that feeds electromagnetic waves in the fundamental mode (TE ₁₁ ), and a feeding waveguide inserted between the conical horn and the feeding waveguide to transmit electromagnetic waves from the fundamental mode to higher-order modes thereof. Generate TM ₁₁ mode as
In a multi-mode horn antenna configured with a TM ₁₁ mode generating section and excited in the fundamental mode and TM ₁₁ mode, the inner diameter of the feeding waveguide side of the TM ₁₁ mode generating section is larger than the inner diameter of the feeding waveguide. , and a linear tapered waveguide having a size that does not allow the TM ₁₁ mode to propagate and is inserted between the feeding waveguide and the TM ₁₁ mode generating section to smoothly connect the inner walls of the two. mode horn antenna. 2. Claim 1: The inner diameter of the feeding waveguide side of the TM ₁₁ 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. Multi-mode horn antenna described in Section 1. 3 The TM ₁₁ mode generating section includes a flare whose one end is connected to the linear tapered waveguide, and a straight line whose one end is connected to the flare and the other end is connected to the conical horn, and which propagates the fundamental mode and the TM ₁₁ 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 ₁₁ mode generating section has an iris for generating TM ₁₁ mode on its inner wall.