JPH07297622A - Horn structure for slot array antenna - Google Patents

Abstract

PURPOSE:To improve the directivity on the vertical plane of an antenna without increasing the length of a horn nor providing a dielectric plate by placing a metallic plate in the horn to divide the electromagnetic wave propagated in the horn. CONSTITUTION:The electromagnetic wave radiated from a slot array antenna 1 undergoes the elimination of its orthogonal polarized wave component by a subpresser plate 3 and reaches a metallic plate 4. The plate 4 functions as the deformed Y branch by means of the upper and lower metallic plates 2a and 2b which construct a horn part 2. Thus the electromagnetic wave that hit the plate 4 is divided into two waves on a magnetic field surface. These divided waves reach the metallic plates 5a and 5b respectively and divided gain there. Then the divided waves are synthesized at a place near the horn opening part. The electromagnetic waves passing through between the plates 28 and 5a and between the plates 5b and 2b have the same phase and the same amplitude. The phases and amplitudes of these electromagnetic waves are approximately equalized to those of the electromagnetic wave which passes through between the metallic plates 5a and 5b by adjustment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horn structure of a slot array antenna installed to improve the directivity of a slot array antenna in a vertical plane.

[0002]

2. Description of the Related Art An antenna for outputting radio waves having a fan beam-shaped directional pattern is used in a radar device, and a typical example thereof is a slot in which one waveguide is provided with a large number of slits. There is an array antenna. The linear (one-dimensional) array antenna arranged in the horizontal plane can sharpen the directivity in the horizontal plane as is well known, but the directivity in the vertical plane cannot be sharpened as it is, and this is the same in the slot array antenna. Therefore, as an antenna used in the radar device, an antenna having a structure in which horn portions are provided by two metal plates above and below the radiation direction of the slot array antenna is often used.

FIG. 6 is a perspective view showing an example of a slot array antenna having the above-mentioned horn part. In the figure, 1 is a slot array antenna, and 2 is a horn composed of two upper and lower metal plates 2a and 2b. Parts 3 are suppressor plates that suppress orthogonal polarization components, Lh is the horn length of the horn unit 2, and A is the opening width of the horn unit 2. Next, the operation will be described. When a radar wave is input to the slot array antenna 1, the input radar wave propagates through the waveguide and is radiated toward the horn portion 2 from many slits provided on the waveguide surface. Then, the radiated radar wave propagates in the horn portion 2 while spreading in a cylindrical shape from the vicinity of the throat portion toward the opening portion and is radiated from the opening portion to the space.

In principle, as the opening width A of the horn portion 2 is increased, its directivity should be sharper. However, in order to maintain the sharp directivity, the horn length Lh is also equal to the opening width A. It needs to be set longer in proportion to the size. FIG. 7 is a diagram for explaining the relationship between the horn length and the phase distribution in the vicinity of the opening. As shown in FIG. 7, even if the horn has the same opening width, it is the same for L1 having a short horn length. The phase plane M1 becomes more curved, and the horn length is long L2.
The phase distribution of the opening is not uniform as compared with the equiphase surface M2.

FIG. 8 is a diagram showing the gain characteristic of the H-plane sectoral horn for explaining the gain characteristic of the horn unit 2 shown in FIG. 6, in which the vertical axis represents the gain G and the horizontal axis represents the wavelength of the electromagnetic wave. Is the opening width (A / λ) normalized by λ, and the solid line in the drawing shows that the normalized horn length (Lh / λ) is 6,
The gain characteristics in the case of 10, 20, and 30 are shown, and the broken line shows the gain characteristics in the ideal state in which the amplitude and the phase are uniformly distributed near the opening. As shown in FIG. 8, the horn length (Lh /
It is understood that the gain initially increases when the aperture width is increased in any of the cases where λ) is 6 to 30, but the gain decreases even when the aperture width is further increased.

The cause of this is as described above with reference to FIG.
This is because the radio wave radiated from the slot array antenna is radiated at the same speed in all directions, and the equiphase surface is curved, and the amplitude distribution is weighted in the aperture plane, and therefore the same aperture width is used. Then, if the horn length is longer, the gain G can be improved, and if the amplitude and phase distribution in the opening can be made uniform by any method, the ideal antenna shown by the broken line in FIG. 8 can be obtained. can get. As a method of making the amplitude and phase distributions in the opening as uniform as possible, in addition to the method of lengthening the horn length as described above, a dielectric plate is installed in front of the center of the opening and radio waves radiated from the center are radiated. Has been developed as a prior art.

[0007]

As described above, in the conventional slot array antenna horn structure, when the opening width of the horn portion is increased to improve the directivity of the vertical plane, the horn length is lengthened accordingly. However, it is necessary to make the amplitude and phase distribution uniform in the opening by installing a dielectric plate in front of the antenna, etc., which results in an increase in size and weight of the antenna. In addition, the support mechanism that supports and operates this antenna also becomes large. Further, there is a problem that it is not easy to store in the radome.

The present invention has been made to solve the above problems, and it is not necessary to lengthen the horn or install a dielectric plate, and the opening width is increased to improve the directivity of the vertical surface. It is an object of the present invention to provide a horn structure of a slot array antenna which is large, small, lightweight and has good performance.

[0009]

In the horn structure of the slot array antenna according to the present invention, another metal plate is installed in the horn portion in parallel with the central axis of the horn portion, and the electromagnetic wave is once divided by the other metal plate. Then, the phase and amplitude of the divided electromagnetic waves are respectively adjusted, and then the divided electromagnetic waves near the horn opening are combined and radiated.

Further, another metal plate is installed in the horn part so as to be inclined with respect to the central axis of the horn part, the electromagnetic wave is once divided by the other metal plate, and the phase and amplitude of the divided electromagnetic wave are adjusted respectively. The structure is characterized in that the electromagnetic waves divided near the horn opening are combined and radiated.

Further, the invention is characterized in that a plurality of other metal plates are provided inside the horn portion. Further, a support plate for supporting another metal plate is installed in the horn portion.

[0012]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a perspective view showing a first embodiment of the present invention,
In the figure, 1 is a slot array antenna, 2 is upper and lower 2
The horn portion 3 composed of the metal plates 2a and 2b is a suppressor plate for suppressing orthogonal polarization components, Lh is the horn length of the horn portion 2, and A is the opening width of the horn portion 2. Further, 4 is a width L4 that divides an electromagnetic wave propagating inside the horn.
The first metal plates 5a, 5b are second metal plates having the same width L5 for further dividing each electromagnetic wave divided by the metal plate 4.

Next, the operation will be described. The suppressor plate 3 removes the orthogonal polarization component of the electromagnetic wave radiated from the slot array antenna 1, and the electric field direction of the electromagnetic wave reaches only the component perpendicular to the paper surface and reaches the metal plate 4. The metal plate 4 includes two upper and lower metal plates 2 that form the horn portion 2.
The electromagnetic waves hitting the metal plate 4 are divided into two by a and 2b which function as a modified Y branch. Then, each of the electromagnetic waves divided into two is respectively fed to the metal plate 5
a, 5b, again split by the modified Y-branch,
After that, it is synthesized near the horn opening.

Then, an electromagnetic wave (tentatively referred to as electromagnetic wave 1) passing between the metal plate 2a and the metal plate 5a (this is tentatively referred to as port 1) and between the metal plate 5b and the metal plate 2b ( This has the same phase and amplitude as an electromagnetic wave (which is tentatively referred to as electromagnetic wave 3) passing through port 3). Therefore, the phase and amplitude of the electromagnetic wave 1 and the electromagnetic wave 3, and the metal plate 5a and the metal plate 5b. And the amplitude and the amplitude of the electromagnetic wave (which is tentatively referred to as the electromagnetic wave 2) that passes through (and tentatively called the port 2) are adjusted to substantially match.
That is, since the propagation phase of the electromagnetic wave passing through the port as described above can be approximately calculated by the port width W and the port length L, the width W1 of the port 1 and the port 3 with respect to the width W2 of the port 2 described above. By appropriately setting the widths W3 and W3 and the width L5 of the metal plates 5a and 5b that are the lengths of the ports, the phases of the electromagnetic waves 1 and 3 and the electromagnetic wave 2 are matched. Also, regarding the amplitude of the electromagnetic waves that pass through each port, the impedance changes depending on the width of each port, and the electromagnetic waves are branched and divided roughly according to the impedance ratio, so if you adjust the ratio of the width of each port ( In the example, the ratio of W2 to W1 and W3) and the amplitude difference of each electromagnetic wave can be made substantially equal. Therefore,
By adjusting the width W of each port and the length L of each port, a uniform electromagnetic field distribution required for gain increase can be obtained in the horn opening.

FIG. 2 is a diagram showing the directivity characteristics of the antenna according to the first embodiment of the present invention shown in FIG. 1. The horn length Lh = 43.5 cm and the horn opening width A = shown in FIG.
It is a figure which shows the directivity characteristic measured at 36.0 cm and a frequency of 5.5 GHz, and the dotted line M in the figure is the case of the conventional antenna which is not provided with the 1st metal plate 4 and the 2nd metal plates 5a and 5b. The solid line N in the figure indicates the first metal plate 4 having a width L4 = 6 cm at a position 11 cm away from the horn throat and the width L5 at a position 16.7 cm away from the throat.
3 shows the directional characteristics of the antenna of Example 1 shown in FIG. 1 in which the metal plates 5a and 5b of 2 cm are installed 4 cm apart from the center of the opening.

As shown in FIG. 2, if the same horn portion is used,
It can be seen that the embodiment shown in FIG. 1 improves the gain by about 3 dB. In order to improve the gain by about 3 dB in the conventional device without the metal plate 4 and the metal plates 5a and 5b, the horn length Lh needs to be 160 cm or more,
According to the first embodiment of the present invention, the horn length Lh is 116 cm.
By shortening the above, an antenna with the same gain can be obtained.

Example 2. 3 is a perspective view showing a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding portions, and 6 is a support plate. A support plate is generally used to support the metal plates 4 and 5a, 5b, but when the support plate is installed in the horn portion 2, the side lobe generally becomes large. Therefore, in order to suppress the side lobes, in the second embodiment, the support plate 6 is installed so as to be perpendicular to the wavefront of the electromagnetic wave passing through the metal plate 4, the metal plates 5a and 5b and the horn portion 2, and is supported. The plate 6 was installed at intervals of 5 wavelengths or more.

Example 3. In the above-described first and second embodiments, the metal plate is provided in the horn part 2 to radiate electromagnetic waves having a substantially symmetrical electromagnetic field distribution with improved gain. However, the metal plate is used as the central axis of the horn part. It may be installed asymmetrically to radiate an electromagnetic wave having a specific directional pattern. FIG. 4 shows an example in which one metal plate 7 is installed in the horn portion 2 so as to be displaced from the center of the opening so that the antenna directivity has a quasi-COSEC ² pattern.

FIG. 5 is a diagram showing the directivity characteristics of the antenna shown in FIG. 4, in which the horn length Lh of the antenna shown in FIG.
= 43.5 cm, horn opening width A = 27.0 cm, width L7 = 2c at a position 16.7 cm away from the horn throat.
It is a figure which shows the directivity characteristic which installed the metal plate 7 of m at the position of 1.5 cm below the horn opening center, and measured it at a frequency of 5.5 GHz. As shown in FIG. 5, the directivity characteristic of the quasi-COSEC ² pattern is shown. Can be obtained.

Example 4. Further, the above-mentioned Examples 1 to 3
In each of the above examples, the metal plate is installed parallel to the central axis of the horn unit 2. However, the metal plate may be installed at an angle from the central axis in order to obtain a specific directivity characteristic.

[0021]

As described above, in the horn structure of the slot array antenna of the present invention, the metal plate is installed in the horn portion, and the horn length is lengthened by controlling the amplitude and phase of the radio wave propagating inside the horn. Without increasing the antenna gain. In addition, by installing the metal plate to be displaced from the center of the horn opening or by inclining it with respect to the center axis of the horn, it is possible to easily obtain a specific directivity characteristic such as obtaining directivity of a quasi-COSEC ² pattern. There is an effect that the obtained antenna can be configured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the directivity characteristic of the antenna shown in Example 1;

FIG. 3 is a perspective view showing a second embodiment of the present invention.

FIG. 4 is a perspective view showing a third embodiment of the present invention.

FIG. 5 is a diagram showing directivity characteristics of the antenna shown in Example 3;

FIG. 6 is a perspective view showing a configuration of a conventional antenna of this type.

FIG. 7 is a diagram showing a problem of a conventional antenna of this type.

FIG. 8 is a diagram showing a problem of a conventional antenna of this type.

[Explanation of symbols]

 1 slot array antenna 2 horn part 3 suppressor plate 4 first metal plate 5a, 5b second metal plate 6 support plate 7 metal plate

Claims (4)

[Claims] 1. A horn structure of a slot array antenna, in which two metal plates are provided above and below in the radiation direction of the slot array antenna to provide a horn portion, and in the horn portion, another horn portion is provided parallel to the central axis of the horn portion. A feature is that a metal plate is installed, an electromagnetic wave is once divided by this other metal plate, the phases and amplitudes of the divided electromagnetic waves are respectively adjusted, and then the divided electromagnetic waves are combined and emitted near the horn opening. Horn structure of slot array antenna. 2. In a horn structure of a slot array antenna in which two metal plates are provided above and below in a radiation direction of the slot array antenna to provide a horn portion, the horn portion is tilted to the central axis of the horn portion to separate the horn portion. A metal plate is installed, the electromagnetic wave is divided once with this other metal plate, the phase and amplitude of the divided electromagnetic waves are adjusted respectively, and then the divided electromagnetic waves are combined and emitted near the horn opening. The horn structure of the slot array antenna. 3. The horn structure for a slot array antenna according to claim 1, wherein a plurality of different metal plates are provided inside the horn portion. 4. The horn structure for a slot array antenna according to claim 1, wherein a support plate for supporting the other metal plate is provided in the horn portion.