JPH05199030A - Dual mode horn antenna - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the deterioration of the radiation pattern due to the TE ₁₂ mode which is an unnecessary mode in a multi-mode horn antenna. [Configuration] Tapered waveguide 2 at the first stage as seen from the horn opening
So that the TE ₁₂ modes occurring at both ends of
The taper angle of the two-stage tapered waveguide 3 and the length of the first-stage tapered waveguide 2 are selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horn antenna used in a microwave or millimeter wave band, and relates to a multimode horn antenna excited by using a TE ₁₁ mode which is a fundamental mode of a circular waveguide and a higher order mode. It is a thing.

[0002]

2. Description of the Related Art FIG. 2 is a cross-sectional view of a conventional flare angle type multimode horn antenna. In FIG. 2, 1 is a conical horn, 2 is a first stage tapered waveguide, 3 is a second stage tapered waveguide, Reference numeral 4 is an opening side flare, and 5 is a power feeding side flare.

FIG. 3 is a diagram showing modes of a circular waveguide.

Next, the operation will be described. Usually, when a conical horn is excited by using the TE ₁₁ mode which is the fundamental mode of a circular waveguide, there are differences in the radiation patterns on the E and H planes, and the radiation level of cross-polarized components also increases.
In order to improve this, in the flare angle type multi-mode horn antenna, a part of the TE ₁₁ mode excited from the feeding side is divided into a feeding side flare 5 and an opening side flare 4 and one of the higher modes of the circular waveguide is used. converted to a TM ₁₁ mode and the length of the conical horn 1 and the first-stage tapered waveguide 2, TM ₁₁ mode generated by the feeding side flare 5 and the opening side flare 4 in the horn aperture, both TE _The phase difference is 0 ° with respect to ₁₁ modes. As a result, the electric field distribution at the horn aperture of the multimode horn antenna is shown in FIG.
The electric field distribution of the TE ₁₁ mode shown in (a) and the electric field distribution of the TM ₁₁ mode shown in FIG. 3 (b) are combined, and the electric field of the cross polarization component is canceled as shown in FIG. 3 (c). It has an electric field distribution. As a result, good characteristics are obtained in which the radiation patterns on the E and H planes match and the radiation level of the cross polarization component is low.

[0005]

As described above, in the conventional flare angle type multi-mode horn antenna, the inclination angles θ of the first-stage tapered waveguide 2 and the second-stage tapered waveguide 3 are respectively formed. ₂ and θ ₃ are determined so that the amount of TM ₁₁ mode generated becomes a desired value, and the lengths of the first-stage tapered waveguide 2 and the conical horn 1 are the feed flare 5 and the opening flare 4
Although it is decided that the TM ₁₁ mode generated in 1) has a phase difference of 0 ° with respect to the TE ₁₁ mode at each aperture,
Fig. 3 (d), which occurs at the same time as TM ₁₁ mode in the flare part
Since there is no consideration for the TE ₁₂ mode shown in, the aperture distribution becomes different from the desired shape obtained by combining the TE ₁₁ mode and the TM ₁₁ mode, and the degree of coincidence of the radiation patterns of the E surface and the H surface deteriorates. There was a problem.

The present invention has been made in order to solve the above-described problems, and obtains a desired TM ₁₁ mode generation amount and a desired phase difference with respect to the TE ₁₁ mode at the horn opening and cancels the TE ₁₂ mode at the opening. It is intended to obtain a flared angle type multimode horn antenna.

[0007]

A flare angle type multi-mode horn antenna according to the present invention has a taper angle of a first-stage tapered waveguide 2 and a second-stage tapered waveguide 3 and a conical horn 1 and a first-stage tapered waveguide. By setting the length of the tapered waveguide 2 of 1 to such a value that the TE ₁₂ mode is canceled by the aperture,
This is the one that eliminates the deterioration of the radiation pattern due to the TE ₁₂ mode.

[0008]

In the flare angle type multi-mode horn antenna according to the present invention, the taper angles of the first-stage tapered waveguide 2 and the second-stage tapered waveguide 3 are generated by the opening-side flare 4 and the feeding-side flare 5. phase difference at TE ₁₂ the equal angular amount of generated modes, and the first stage of the length of the tapered waveguide 2, TE ₁₂ mode of the horn opening generated in the opening side flare 4 and the feeding side flare 5 Is set to 180 ° so that the TE ₁₂ mode is canceled at the horn opening.

[0009]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a conical horn, 2 is a first stage tapered waveguide, 3 is a second stage tapered waveguide, 4 is an opening side flare, and 5 is a feeding side flare.

Next, the operation of the flare angle type dual mode horn antenna according to the present invention will be described. The TM ₁₁ mode generation amount CTM ₁₁ and the TE ₁₂ mode generation amount CTE ₁₂ in the flare portion are determined by the diameter d of the flare portion, the change width Δθ of the flare portion, and the wavelength λ, as shown in Equation 2.

[0011]

[Equation 2]

The difference between the taper angle of the conical horn 1 and the taper waveguide 2 of the first stage is Δθ ₁ , the diameter of the flare 4 on the opening side is d ₁ , and the taper waveguide 2 of the first stage and the taper of the second stage are tapered. The angle difference of the waveguide 3 is Δθ ₂ and the diameter of the feeding flare 5 is d ₂
Was when the, the generation amount of TE ₁₂ mode generated by the opening side flare 4, the amount of TE ₁₂ mode generated by the power supply side flare 5 is indicated by the number 3.

[0013]

[Equation 3]

From Equation 3, the condition for equalizing the amounts of TE ₁₂ mode generated in the opening flare 4 and the power supply flare 5 is Equation 4.

[0015]

[Equation 4]

Further, the phase difference φ ₁₂ between the TE ₁₁ mode and the TE ₁₂ mode traveling in the tapered waveguide can be expressed by equation 5.

[0017]

[Equation 5]

In the flare 5 on the feeding side, the TE ₁₂ mode is TE
It occurs at a phase of -π / 2 with respect to the ₁₁ mode, and in the flare 4 on the aperture side, the TE ₁₂ mode is + π / with respect to the TE ₁₁ mode.
It occurs in the phase of 2. Thus, by a value which satisfies the number 6 a length L ₁ of the tapered waveguide 2 in the first stage, TE ₁₂ mode generated by the TE ₁₂ mode and the opening side flare 4 generated in the power feeding side flare 5 Horn The phase becomes opposite at the aperture.

[0019]

[Equation 6]

The flare angle type dual mode horn antenna according to the present invention has a desired TM _{11 at the} horn opening.
Assuming that the amount of generated modes and the phase difference with respect to the TE ₁₁ mode are obtained, the TE ₁₂ mode is almost canceled at the aperture because the size satisfies the conditions of Formulas 4 and 6 strictly or approximately.

[0021]

As described above, according to the present invention, by reducing the influence of the TE ₁₂ mode, the E plane,
A good radiation pattern with a uniform beam width on the H-plane can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a flare angle type multi-mode horn according to the present invention.

FIG. 2 is a diagram showing a configuration of a conventional flare angle type multi-mode horn.

FIG. 3 is a diagram showing an aperture distribution of a circular waveguide.

[Explanation of symbols]

 1 Conical horn 2 1st stage tapered waveguide 3 2nd stage tapered waveguide 4 Opening flare 5 Feeding flare

Claims (1)

[Claims] 1. In a multi-mode horn antenna in which two stages of tapered waveguides having different taper angles are sequentially connected to a conical horn when viewed from the horn opening side, a taper angle of the conical horn and an angle of the first stage tapered waveguide are provided. Is Δθ ₁ , the diameter of the joint is d ₁ , the angle difference between the first-stage tapered waveguide and the second-stage tapered waveguide is Δθ ₂ , the diameter of the joint is d ₂ , the first-stage. When the phase amount of the TE ₁₁ mode that changes while traveling in the tapered waveguide is φ ₁ and the phase amount of the TE ₁₂ mode is φ ₂ , the desired TM ₁₁ mode generation amount and TE ₁₁ Under the condition that the phase difference for the mode is obtained, the values of Δθ ₁ , Δθ ₂ , d ₁ , d ₂ , φ ₁ and φ ₂ are A multimode horn antenna characterized by satisfying exactly or approximately.