JPH0964637A - Waveguide slop antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to radiate straight polarized wave inclined by the inclination angle of a slot element and to increase the degree of freedom in antenna mounting by inclining the slot element from the axis of a waveguide. SOLUTION: A square waveguide 1 consists of a feeding aperture 2, a short- circuit terminal 3 and plural radiation slots 12 having an angle θ from the axis of the waveguide 1 and parallel with each other. A current is allowed to flow in the width direction of the waveguide 1 on the position of each slot 12. The slot 12 is excited by a component parallel with the slot 12 out of the current and a polarized wave in the direction of an electric field vector 32 is radiated. When plural slots 12 are arranged alternately about the center axis of the waveguide 1 at the interval of 0.4 to 0.6 intra-waveguide wavelength, all the slots 12 can be excited at the same phase. When the current direction is not rectangular to the direction of the slots 12, i.e., the slots 12 are not paralell with the waveguide wall, a short-circuit terminal 3 is used. Consequenty, a straight polarized wave having a polarized face with an optional angle from the axial direction of the waveguide 1 can be radiated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide slot antenna, and more specifically to a waveguide slot antenna suitable for use in radio communication / radar, etc. using arbitrary linearly polarized waves or circularly polarized waves. Regarding

[0002]

2. Description of the Related Art A waveguide slot antenna is known in which a large number of radiation slots parallel to the tube axis are alternately arranged at half wavelength intervals in the tube axis direction with a central axis therebetween. FIG. 4 shows an instantaneous current distribution of a rectangular waveguide wide wall surface fed in TE10 mode, and FIG. 5 shows a top view of the waveguide slot antenna, that is, a wide wall surface. In FIG. 5, the rectangular waveguide 1 comprises a feed opening 2, a short-circuit termination 3 or a matching termination 4, and radiating slots 11, 11, ... Which are parallel to the tube axis. Note that in FIG. 5, for convenience of explanation of the operation principle, a fine scale is provided for each 1/4 tube wavelength, and a thick scale is provided for each 1 tube wavelength. The current distributions 21, 21, ... Of FIG. 4 are drawn so that the principle of the force lines, that is, the direction of the lines is the direction of the current, and the density of the lines is proportional to the magnitude of the current. When the waveguide 1 is short-circuited by the short-circuit terminal 3, the magnitude and the sign of the current distributions 21, 21, ... Change sinusoidally with time, and the shape of the distribution with respect to the position does not change. On the other hand, in the case where the current distributions 21, 21, ... Are matched by the matching termination 4, the current distributions 21, 21 ,. The slot element is excited by a current component in a direction orthogonal to its axis and radiates a radio wave having a polarization opposite to this current, so that the slots 11, 11, ...
Radiates polarized waves in the directions of electric field vectors 31, 31, .... Clearly from the current distributions 21, 21, ..., Slot 1
, Are alternately arranged at half-wavelength intervals with respect to the central axis to excite all slots 11, 11, ... In-phase with the polarization in the tube width direction.

[0003]

In the example of FIG. 5, there is a structure of polarization in the tube width direction. On the other hand, an automobile collision prevention radar requires an antenna that radiates a circular polarized wave or a diagonal 45-degree polarized wave.

Therefore, the present invention presents a waveguide slot antenna capable of radiating free-angle linearly polarized waves and circularly polarized waves including an oblique angle of 45 degrees by using a short circuit termination or a matching termination.

[0005]

There are three types of waveguide slot antennas of the present invention.

The first is to radiate a linearly polarized wave at an arbitrary angle by means of a short-circuit termination, in which slot elements are alternately arranged with a central axis on a wide wall surface in the tube axis direction at about 1/2 tube wavelength interval. Each slot element is arranged to be inclined by an angle θ with respect to the tube axis direction, and radiates a linearly polarized wave inclined by an angle θ with respect to the tube width direction.

The second is to radiate a linearly polarized wave of an arbitrary angle by a matching terminal, and the slot element has a wavelength interval of about 1/2 in the tube on the central axis of the wide wall surface and symmetrically on both sides of the central axis. The linearly polarized waves are arranged at positions shifted from each other in the tube axis direction by about 1/4 in-tube wavelength at intervals of about 1/2 in-tube wavelength and radiate a linearly polarized wave inclined by an angle θ from the tube width direction.

Thirdly, a circularly polarized wave is radiated by short-circuiting or matching termination, and the V-shaped slot element is alternately arranged on the central axis of the wide wall surface in a reverse direction at a wavelength interval of about ½ tube and is linear. Slot elements are arranged parallel to the tube axis and alternately on both sides of the central axis at the same position in the tube axis direction as the V-shaped slots at about 1/2 tube wavelength interval, and radiate a right-handed or left-handed circularly polarized wave. To do.

[0009]

It is possible to design a slot array that synthesizes arbitrary linearly polarized waves or circularly polarized waves independently of the shape of the waveguide slot array antenna which is normally rectangular. Therefore, the degree of freedom in mounting the antenna is dramatically increased.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that although the description is for transmission for the sake of convenience of explanation, it is clear that, for reciprocity, it simply works in reverse due to the reciprocity theorem.

FIG. 1 is a top view of the first embodiment of the present invention, that is, a wide wall surface. The current distribution is FIG. 4 as in the example of FIG. In FIG. 1, a rectangular waveguide 1 is composed of a feed opening 2, a short-circuit termination 3, and radiation slots 12, 12, ... Note that, in FIG. 1 as well, for convenience of explanation, a fine scale for each quarter wavelength
There is a thick scale for each wavelength in the tube. Slot 1
At positions 2, 12, ... As shown in FIG. 4, a current flows in the tube width direction. Since the slot element is excited by a current of a component orthogonal to its axis, it is excited by a component of the current in the tube width direction which is parallel to the slots 12, 12, ..., And the direction of the electric field vectors 32, 32 ,. Emits polarized waves. From the current distributions 21, 21, ... Obviously, by arranging the slots 12, 12, ..
2, ... Can be excited in the same phase.

Slots 12, 1 as in the embodiment of FIG.
If 2, ... Are not parallel to the tube wall, it is necessary to use a short circuit termination 3. This is the direction of current flow and slots 12, 1
This is because the directions of 2, ... Are not right angles. When the matching termination 4 is used, the current distribution 21 progresses as it is toward the termination direction due to the progress of time, but the time at which the current and the slot are orthogonal to each other differs between the upper slot and the lower slot of the tube axis. Therefore, the slots are not excited in phase. Therefore, in this case, the following embodiment of FIG. 2 must be used.

FIG. 2 is a top view of the second embodiment of the present invention, that is, a wide wall surface. The current distribution is FIG. 4 as in the example of FIG. In the example of FIG. 2, the slots 13, 13, ...
Slot 1 symmetrical about the central axis at a position shifted by 4 wavelengths
4, 14, ... Are arranged. Also in FIG. 2, for convenience, 1 /
4 A thin scale is provided for each in-tube wavelength, and a thick scale is provided for each in-tube wavelength. Since the adjacent slots 13 and 13 are separated from each other by 1/2 wavelength and are fed in opposite phases to each other, the radiated electric field vectors are 33 and 33, respectively. When these electric field vectors are combined, only the component parallel to the tube width remains. On the other hand, slots 1 on both sides of the central axis
Since 4 and 14 are fed in phase, the radiated electric field vectors are 34 and 34. When these electric field vectors are combined, only the component parallel to the tube axis remains. Also,
Slots 14, 14 adjacent to each other in the axial direction of the pipe have different slot angles.
This is because the angle of is defined as the direction orthogonal to the current.
The slots 13, 13, ... And the slots 14, 14, ... Are shifted by a quarter wavelength in the tube axis direction so that the phases of the currents match each other, as can be seen from FIG. In this case, the slots 13, 13, ... And the slots 14, 14 ,.
It is possible to radiate a linearly polarized wave in an arbitrary direction as a whole by adjusting the excitation intensity of (1) according to the slot length and the angle.

FIG. 3 is a top view of a third embodiment of the present invention, that is, a wide wall surface. The current distribution is FIG. 4 as in the example of FIG. In the example of FIG. 3, the V-shaped slots 15, 15, ... Are alternately arranged in opposite directions on the central axis at 1/2 wavelength intervals, and the V-shaped slots and the central positions are arranged at the same position in the tube axial direction. Straight slot 1 parallel to the tube axis, alternating on both sides of the axis
6, 16, ... Are arranged. Also in FIG. 3, for convenience, 1 /
4 A thin scale is provided for each in-tube wavelength, and a thick scale is provided for each in-tube wavelength. The V-shaped slot 15 radiates the electric field vectors 35, 35 from each side, so that the combined electric field has only the tube axis direction component. On the other hand, the slots 16, 16, ... Are the same as the slots 11, 11 ,.
6, 36, ... Orient in the pipe width direction. When the matching termination 4 is used, as can be seen from FIG. 4, the time at which the slots 15, 15, ... Are excited most strongly and the time at which the slots 16, 16, ... Are excited most are shifted by ¼ cycle. , Circularly polarized waves are radiated as a whole.

When the short-circuit termination 3 is used, the electric field vectors 35, 35, ... And 36, 36, ... Have the same phase as they are, and circular polarization is not radiated, but the slot 15,
, 16, and 16, 16, ... Are changed, and the electric field vector 35,
Circularly polarized radiation is possible by providing a phase difference of 90 degrees between 35, ... And 36, 36 ,.

In the above embodiment, the explanation was made in consideration of radiating the radio wave to the front of the antenna, but the beam tilt method of moving the radiation direction from the front by changing the slot interval is a known technique. In order to realize it, it is necessary to change the slot interval from the value in the above embodiment.

[0017]

As can be easily understood from the above description, according to the present invention, it is possible to radiate a linearly polarized wave and a circularly polarized wave having a plane of polarization at an arbitrary angle with respect to the tube axis direction of the waveguide. A waveguide slot antenna can be provided.

The present invention will be announced at the 1995 Society of Electronics, Information and Communication Engineers Communication Society Conference held on September 4, 1995 at the Faculty of Science and Engineering, Chuo University.

[Brief description of drawings]

FIG. 1 is a top view of an embodiment of claim 1 of the present invention.

FIG. 2 is a top view of a second embodiment of the present invention.

FIG. 3 is a top view of an embodiment of claim 3 of the present invention.

FIG. 4 is a current distribution on a wide wall of a rectangular waveguide fed in TE10 mode.

FIG. 5 is a plan view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rectangular waveguide 2 ... Feeding opening 3 ... Short-circuit termination 4 ... Matching termination 11 ... Radiation slot 12 ... Radiation slot 13 ... Radiation slot 14 ... Radiation slot 15 ... Radiation slot 16 ... Radiation slot Slot 21 ... Force line expression of current distribution 31 ... Electric field vector 32 ... Electric field vector 33 ... Electric field vector 34 ... Electric field vector 35 ... Electric field vector 36 ... Electric field vector

Claims (3)

[Claims] 1. A rectangular waveguide having a plurality of radiating slot elements, one end of which is short-circuited and terminated, wherein the slot elements are alternately arranged in a tube axial direction with a central axis on a wide wall surface. 〜0.6 In the tube wavelength interval, the slot element is inclined by an angle θ with respect to the tube axis direction to radiate a linearly polarized wave with an angle θ from the tube width direction. A waveguide slot antenna, characterized in that. 2. A rectangular waveguide having a plurality of radiating slot elements, one end of which is matched and terminated, the slot element being diagonally inclined with respect to the central axis and having 0.4 on the central axis of a wide wall surface. .About.0.6 in-tube wavelength intervals, and symmetrically on both sides with respect to the central axis in a direction oblique to the central axis, at a position offset by 0.2 to 0.3 in-tube wavelengths in the tube axis direction from the on-axis slot. A waveguide slot antenna characterized by radiating a linearly polarized wave inclined by an angle θ with respect to the tube width direction by being arranged at a wavelength interval of 4 to 0.6 in the tube. 3. A rectangular waveguide comprising a plurality of radiating slot elements, one of which is short-circuited or matched-terminated, wherein the V-shaped slot elements are arranged in opposite directions alternately on the central axis of the wide wall surface. 0.4 to 0.6 in the tube wavelength interval, the linear slot elements are arranged in parallel with the tube axis on both sides of the central axis alternately at the same position as the V-shaped slots in the tube axis direction.
0.6 A waveguide slot antenna, which radiates circularly polarized waves by being arranged at an in-tube wavelength interval.