JPH0752807B2 - Horn antenna - Google Patents

Description

TECHNICAL FIELD The present invention relates to a horn antenna having a radiating element fed by a coaxial line, a strip line, or the like.

[Prior Art] Generally, radiating elements such as a helical antenna and a microstrip antenna that are fed through a coaxial line have circular polarization characteristics, so that an antenna for wireless communication, that is, a parabola. Widely used as the primary radiator of an antenna.

[Problems to be Solved by the Invention] However, when a radiating element such as a helical antenna is downsized and used, the beam directivity deteriorates, and thus it cannot be used as it is, for example, as a primary radiator of a parabolic antenna.

Therefore, for example, a helical horn antenna in which the radiation directivity of a radiating element including a helical antenna is limited by a horn antenna is considered.

Figure 5 shows the configuration of the helical horn antenna.
In the figure, 11 is a coaxial line, 12 is a central conductor of this coaxial line 11, and 13 is an outer conductor. Then, 14 is a helical radiating element connected to the tip of the central conductor 12 in the coaxial line 11, 15 is a bottomed cylindrical horn reflector surrounding the circumference of the helical radiating element 14, 16 is the horn reflector 15 It is a reflector of the helical radiating element 14 formed on the bottom surface.

In this case, by combining the horn reflector 15 with the helical radiating element 14 and varying the inner diameter and the length of the horn reflecting surface of the horn reflector 15, the radiation directional characteristics of the helical radiating element 14 can be changed to desired characteristics. Although it can be set, on the other hand, it causes deterioration of circular polarization characteristics, that is, deterioration of axial ratio.

FIG. 6 shows a helical horn antenna in which a cone-shaped horn reflector 17 is used and the inner diameter of the horn reflecting surface is changed to a large diameter toward the tip opening surface. In the case of this helical horn antenna as well. In the same manner as above, the axial ratio is deteriorated.

FIG. 7 shows the frequency-axial ratio characteristics (broken line B) of the helical horn antenna when a horn reflector is not used (solid line A).
If the horn reflector is not used, the axial ratio shows good characteristics within 1 dB at frequencies of 11.7 to 12.0 GHz, but if the horn reflector is used, the axial ratio will be
It gets worse than 2 dB.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a horn antenna capable of obtaining a desired directional characteristic without deteriorating the circular polarization characteristic.

[Means for Solving the Problems] A horn antenna according to the present invention includes a feed line, a radiating element connected to the feed line, a circular reflector centering around the feeding section of the radiating element, and A horn reflector, which has a reflector surface as a bottom surface and surrounds the radiating element in a circumferential shape, and a peripheral groove formed in an outer peripheral portion of a bottom reflector of the horn reflector in a direction perpendicular to the reflector surface. It is prepared and configured.

[Operation] That is, the radiation directivity can be set by the horn reflector, and the circular polarization characteristic can be improved by the circumferential groove formed on the outer peripheral portion of the reflector.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a side sectional structure of a helical horn antenna. In the figure, 11 is a coaxial line and 12 is this coaxial line.
11 is a central conductor, 13 is an outer conductor, 14 is a helical radiating element of about 2 to 3 turns which is continuously connected to the central conductor 12 in the coaxial line 11, and 16 is a feeding portion of the helical radiating element 14. Is a helical reflection plate which is formed in a circular plane shape and serves as the bottom surface of a horn reflector 17 which surrounds the helical radiating element 14 in a conical shape.

In this case, the inner diameter of the horn reflecting surface of the horn reflector 17 gradually increases from the reflecting plate toward the tip opening position in order to set the radiation directivity of the helical radiating element 14 in correspondence with the parabolic antenna. Is formed as.

A peripheral groove 18 is formed on the outer peripheral portion of the helical reflection plate 16 and is perpendicular to the plate surface of the helical reflection plate 16.

Here, the design frequency of the above helical horn antenna is 1
If the frequency is 1.7 to 12.0 GHz, the diameter of the helical radiating element 14 is about
10 mm, the inner diameter of the bottom of the horn reflector 17 is about 26 mm, the inner diameter of the tip opening surface is about 36 mm, and the horn length is 13 mm.
The outer diameter of the circumferential groove 18 is about 26 mm, which is the same as the inner diameter of the bottom surface of the horn reflector 17, and its depth is about 8 mm.
Is.

That is, in the helical horn antenna having the above configuration, the horn reflector 17 is combined with the helical radiating element 14,
And by forming the circumferential groove 18 in the helical reflector 16 thereof,
The following characteristics are obtained.

FIG. 2 shows the directional characteristics (solid line A) of the helical horn antenna in comparison with the case where only the helical radiating element 14 is used (broken line B). It can be seen that the radiation directivity is sharpened by the effect.

FIG. 3 shows the frequency vs. axial ratio characteristic (solid line A) of the helical horn antenna in comparison with the case of only the helical radiating element 14 (broken line B). The horn reflector 17 and the circumferential groove 18 are shown.
If only the helical radiating element 14 without
At 11.7 to 12.0 GHz, the axial ratio shows a good characteristic of approximately 1 dB although some fluctuation is seen, but in the case of the helical horn antenna in the present embodiment using the horn reflector 17 and the circumferential groove 18, The axial ratio can be obtained as a stable and flat characteristic near 1 dB.

In other words, the axial ratio characteristic of the helical horn antenna is deteriorated by the current generated near the bottom wall surface of the horn reflector 17 close to the helical radiating element 14, so that the axial ratio characteristic is stable if this current is not easily generated. The peripheral groove 18 is formed on the outer periphery of the helical reflection plate 16 as described above,
By setting the width and the depth to appropriate dimensions, the impedance near the wall surface of the bottom surface of the horn reflector 17 can be increased, and the generation of current there can be suppressed.

Therefore, the axial ratio characteristic of this helical horn antenna is stabilized.

Here, the size of the circumferential groove 18 depends on the frequency, and for example, its width is usually set to about 3 mm to 6 mm in the 12 GHz band from the ease of processing, while the depth is basically The wavelength is set to about ¼ of the wavelength (λ), but in practice, it is set to about 0.2λ to 0.3λ because it changes according to the width.

Therefore, a desired directional characteristic can be obtained by combining the horn reflector 17 with the helical radiating element 14, and furthermore, the deterioration of the axial ratio in the circular polarization characteristic can be compensated by forming the circumferential groove 18, For example, as a primary radiator of a parabolic antenna, a helical horn antenna having good characteristics can be realized with a simple structure.

In the above embodiment, the horn reflector 17 having a conical horn reflection surface is used. However, for example, as shown in FIG. 4, a horn reflector 15 having a cylindrical shape may be used. It is possible to obtain substantially the same antenna characteristics as those of the above-mentioned embodiment.

Further, in the above embodiment, the helical radiating element 14 is used, but the radiating element may be one having a circular polarization characteristic, and is fed by, for example, a coaxial line or a strip line equivalent thereto. A microstrip antenna having a patch shape, a spiral shape, or a slot, or a turnstile antenna having a dipole antenna may be used.

Further, the helical reflection plate 16 in the above embodiment is formed in a circular plane shape, but for example, the reflection surface of the helical radiating element 14 is formed as a part of a horn reflector in which the horn reflection surface has a rotating hyperboloid shape. May be.

[Advantages of the Invention] As described above, according to the present invention, a feeder line, a radiating element connected to the feeder line, a circular reflecting plate having a feeding portion of the radiating element as a center, and the reflecting plate. A horn reflector having a surface as a bottom surface and surrounding the radiating element in a circumferential shape; and a peripheral groove formed in an outer peripheral portion of a bottom reflector of the horn reflector in a direction perpendicular to the reflector surface. Since the radiation directivity characteristics are set by the horn reflector and the circular polarization characteristics are improved by the circumferential groove formed on the outer peripheral part of the reflector, the circular polarization characteristics are not deteriorated. Thus, it is possible to provide a horn antenna capable of obtaining desired directional characteristics.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a helical horn antenna according to an embodiment of the horn antenna of the present invention, and FIG. 2 is a directional characteristic of the helical horn antenna (solid line A) and a case where only a helical radiating element is used (broken line). FIG. 3 is a view showing a comparison with FIG. 3B), FIG. 3 is a view showing the frequency versus axial ratio characteristic (solid line A) of the helical horn antenna compared with the case where only a helical radiating element is used (broken line B), and FIG. FIG. 5 is a side sectional view showing the configuration of another embodiment of the helical horn antenna, FIGS. 5 and 6 are side sectional views showing the basic configuration of the helical horn antenna, and FIG. 7 is a frequency in the helical horn antenna having the above basic configuration. It is a figure which compares an axial ratio characteristic (broken line B) with a case where a horn reflector is not used (solid line A). 11 …… Coaxial line, 12 …… Center conductor, 13 …… Outer conductor, 14
... Helical radiating element, 15 ... Cylindrical horn reflector, 16
…… Helical reflector, 17 …… Conical horn reflector, 18…
… Girth.

Claims (3)

[Claims] 1. A power supply line, a radiating element connected to the power supply line, a circular reflecting plate having a power feeding portion of the radiating element as a center, and a radiating element which has a reflecting plate surface as a bottom surface. A horn reflector formed in a circular shape, and a peripheral groove formed in the outer peripheral portion of the bottom reflector of the horn reflector in a direction perpendicular to the reflector surface, wherein the radiating element and the horn reflector are A horn antenna characterized in that its radiation directivity is set by combination, and the axial ratio characteristics are stabilized by the circumferential groove to improve circular polarization characteristics. 2. The horn antenna according to claim 1, wherein the inside diameter of the horn reflector at the bottom reflector position is the same as the inside diameter of the tip opening face position. 3. The horn antenna according to claim 1, wherein the inside diameter of the horn reflector is gradually increased from the bottom reflector position toward the opening face position.