JPS5823964B2 - horn antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horn antenna used in a microwave band or a millimeter wave band, and more particularly to a horn antenna using TEL mode and TMI mode of a circular waveguide.

Conventionally, such horn antennas include a conical horn 1, a straight circular waveguide 2, and a tapered waveguide 4, as shown in FIG.
was connected to the feeding waveguide 3, and an iris 5 was provided inside the straight circular waveguide section.

However, with this configuration, over a wide frequency band,
When trying to realize a horn antenna with good performance, TE11 reflected from the iris 5 provided in order to obtain the amount of TM11 mode generation necessary for a horn antenna.
The disadvantage is that the amount of mode reflection is large, making it difficult to obtain good characteristics over a wide band.

In order to improve this drawback, the present invention includes a first portion extending toward the tube axis instead of the iris on the inner wall of the straight circular waveguide of the horn antenna, and a first portion extending laterally from the inner end of the first portion. The conical horn is characterized by having one or more metal rings having a bent second portion, and the aperture diameter and opening angle of the conical horn are set so as to obtain the required gain, and the horn can be used over a wide frequency band. When using circularly polarized waves, there are fewer cross-polarized components, and when linearly polarized waves are used, the beam widths in the E and H planes are reduced. The purpose of this is to obtain a good radiation pattern with uniform radiation patterns, and the drawings will be explained in detail below.

FIG. 2a shows an embodiment of the present invention, in which the TM11 mode generation mechanism provided inside the straight circular waveguide 2 is made of a metal ring 7 having a T-shaped cross section, so that the TM11 mode generation mechanism is arranged in the direction of the electric field of the TEII mode. Since it has horizontal and vertical surfaces, TMI
Since the I mode is more likely to occur, the height can be made lower than that of the iris, and therefore the amount of TEII mode reflected from one metal ring 7 is reduced.

This metal ring 7 has a portion extending toward the tube axis and a portion bent toward both sides from its inner end.

When TEl is input from the feeding waveguide 3, a part of the mode is T Ml at the junction surface of the tapered waveguide 4 and the straight circular waveguide 2.
1 mode.

In addition, a TMII mode occurs in the metal ring 7 with a 1-shaped cross section, and T
M11 mode occurs.

T required to obtain good characteristics as a horn antenna
If the relative amplitude and phase of the M11 mode to the TEII mode on the aperture plane are respectively Co + φ0, then the total amplitude C1 phase φ on the aperture plane of the TMII mode generated at each of the above points satisfies the following conditions. Must be satisfied.

CeJφ=CoeJφ0 (1) In order for formula (1) to hold over a wide frequency band, the following condition must also hold.

In the above formula, f represents the frequency.

Further, in the TEII mode, reflections at both ends of the metal ring 7 must be canceled.

In the present invention, even if the aperture diameter and opening angle of the conical horn 1 are determined to obtain the required gain, the width, height, and position of the metal ring 7, the length of the straight circular waveguide 2, and the taper waveguide Since there are 5 degrees of freedom with an opening angle of 4, it is possible to satisfy all the constraint conditions necessary to obtain good characteristics as a horn antenna.

Therefore, when using circularly polarized waves, it is possible to obtain a good radiation pattern with few cross-polarized components, and when using linearly polarized waves, it is possible to obtain a good radiation pattern with uniform beam widths in the E plane and H plane.

The above explanation was given for the case where the cross section of the metal ring γ is T-shaped, but as shown in Fig. 2, c, it is also possible to
A similar effect can be obtained by using metal rings 8 and 9 having a letter-shaped cross section.

Further, as shown in FIG. 3, the same effect can be obtained by using modified examples 7' to 9' in which some or all of the corners of the metal rings γ to 9 are rounded.

As described above, according to the present invention, T
Since the amount of reflection in the E1t mode is small, circularly polarized waves have few cross-polarized components, and linearly polarized waves can obtain a good radiation pattern with uniform beam widths in the E plane and H plane, it can be used as a horn antenna. Of course, it is also effective as a primary radiator for parabolic antennas and Cassegrain antennas.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view and a side view showing the schematic structure of a conventional horn antenna, FIGS. 2 is a diagram showing a modified example in which the corners of the metal ring in FIG. 6 is an opening surface, 7 is a T-shaped metal ring, 8 is an inverted-J-shaped metal ring, and 9 is an inverted J-shaped metal ring. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1. A horn antenna used in the microwave band or millimeter wave band is composed of a conical horn, a straight circular waveguide, and a tapered waveguide, and a first antenna is provided on the inner wall of the straight circular waveguide, extending toward the tube axis. 1. A horn antenna characterized in that one or more metal rings are provided in the tube axis direction, each having a second portion bent from the inner end of the first portion to the side.