JP2549929Y2 - Whip antenna device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertically polarized omnidirectional whip antenna device mounted on a vehicle roof, indoor ceiling, or the like in mobile communications.

[0002]

2. Description of the Related Art A conventional λ / 4 whip antenna having a vertically polarized horizontal omnidirectional antenna is configured as shown in FIG. In FIG. 5, reference numeral 1 denotes an antenna element having a length of about λ / 4.
Attached to. And the center conductor 4a of the coaxial line 4
Are connected to the antenna element 1 and the external conductor 4b is connected to the ground plate 3 to form the whip antenna 5.

The vertically polarized horizontal omnidirectional whip antenna 5 has a structure in which the center conductor 4a and the outer conductor 4b of the feeding section are open in a DC manner due to the structure thereof. When a high voltage of several tens of kilovolts is generated, there is a possibility that the radio equipment connected to the antenna is adversely affected. In order to reduce the influence of the above-mentioned induced lightning, countermeasures against induced lightning are taken as shown in FIGS.

FIG. 6 shows an arrangement in which an induced lightning prevention device 7 is added between the whip-type antenna 5 and the radio 6. FIG. 7 shows that the height of the antenna element 1 from the ground plate 3 is about λ / 4. In this manner, the end is connected to the ground plate 3 at the short point 8 by folding back from the top. By taking measures against induced lightning as described above, the induced lightning voltage can be reduced to about 10%.

[0005]

Generally, a whip-type antenna has an advantage that it can be manufactured at a low cost because of its simple structure. However, as shown in FIG. If added, it is expensive and poses a mounting space problem.

The whip antenna has a fractional band of 5%.
Although the antenna has the above broadband characteristics, when the antenna element 1 has a folded structure as shown in FIG.
Even if it is matched to a Ω or 75Ω feed line, it is extremely difficult to achieve wideband characteristics.

[0007] The present invention has been made in view of the above circumstances, while maintaining the electrical characteristics of the whip-type antenna,
It is an object of the present invention to provide an inexpensive whip-type antenna device that reduces an adverse effect on a wireless device due to induced lightning.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method having a wavelength of approximately λ / 4.
The base of the antenna element having a length is vertically
Hold the ground plate horizontally with the insulator.
In whip antenna formed by lifting, the feeding unit the central conductor than the length of the antenna element branches the plate-shaped line <br/> approximately lambda / 4 in the horizontal direction, for the above ground plate lambda / 15 or less
It is characterized by being arranged in parallel with a lower interval, and having its tip connected to the ground plate.

[0009]

The length of the antenna element is λ from the center conductor of the feeding part of the antenna element.
/ 4 line is branched and arranged in parallel with the ground plate, and the end of the line is connected to the ground plate, so that λ / 4
The high-frequency impedance when looking at the line side becomes infinite,
A short-circuit structure can be obtained in a DC manner without changing the input impedance of the antenna.

Further, by disposing the λ / 4 line close to the ground plate, radio wave radiation from the λ / 4 line is suppressed and only radio wave radiation from the antenna element is generated. Characteristic can be maintained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional front view showing a part of an antenna device according to an embodiment of the present invention, and FIG. 2 is a plan view.
As shown in FIGS. 1 and 2, the antenna element 11 having a length of about λ / 4 is insulated and supported by an insulator 12 which is an insulator, and is attached to a ground plate 13. A coaxial connector 10, which is a power supply section of the antenna element 11, is attached to a lower side of the ground plate 13. This coaxial connector 1
Numeral 0 comprises a coaxial line 14 and a plug 15. The coaxial line 14 has a center conductor 14 a connected to the antenna element 11 and an outer conductor 14 b connected to the ground plate 13. That is, in the coaxial line 14, the outer conductor 14 b is attached to the ground plate 13 together with the insulator 12 by the screw 16. The upper end of the center conductor 14a of the coaxial line 14 protrudes above the insulator 12 through the center of the insulator 12, and a screw portion 17 is formed at the protruding portion. On the other hand, the antenna element 11 has a screw groove formed in the center of the lower end, and the screw groove is formed in the screw portion 1 of the central conductor 14a.
7 is fixed to the upper part of the insulator 12 by screwing.

The central conductor 14a of the coaxial line 14 is branched from the space between the antenna element 11 and the insulator 12 into a λ / 4 line 18 having a length of approximately λ / 4. This λ /
The four lines 18 have a central conductor 1 in a through hole provided at one end.
The screw 17 of 4a is inserted and positioned above the insulator 12, and the antenna element 11 is fixed by screwing into the screw 17. The other end of the λ / 4 line 18 is bent and connected to the ground plate 13 by, for example, screws. The λ / 4 line 18 is disposed in parallel with and close to the ground plate 13, and has a central conductor 14 a of the coaxial line 14.
The distance from the connection point to the ground plate 13 is set to about λ / 4, and the distance from the ground plate 13 is set to, for example, λ / 15 or less. The λ / 4 line 18 is, for example, 800 MHz
In the case of a z-band antenna, the antenna is formed using an aluminum plate having a width of about 8 mm and a thickness of about 1.2 mm.

In the whip antenna configured as described above, the high-frequency impedance of the λ / 4 line 18 viewed from the connection point between the coaxial line 14 and the λ / 4 line 18 is as follows:
It becomes almost infinite, and the high-frequency input impedance viewed from the coaxial line 14 is not affected by the λ / 4 line 18.

On the other hand, when the above antenna is viewed from a direct current,
The antenna element 11 is connected to the ground plate 1 via the λ / 4 line 18.
3 and acts to reduce the induced lightning voltage to about 10%.

Further, by arranging the λ / 4 line 18 at a distance of about λ / 15 or less from the ground plate 13, radio wave radiation from the λ / 4 line 18 is suppressed, and only radio wave radiation from the antenna element 11 is generated. , Works well as a whip antenna.

FIG. 3 is a diagram showing the standing wave ratio characteristics of the antenna device according to the present invention, and FIG. 4 is a diagram showing the E-plane directivity characteristics. As is clear from the characteristic diagrams shown in FIGS. 3 and 4, the antenna device according to the present invention has a λ /
Even if the four lines 18 are added, the electrical characteristics of the whip antenna can be maintained without being affected by the addition.

[0018]

As described above in detail, according to the present invention, a line having a length of approximately λ / 4 is branched off from the center conductor of the feeding portion of the antenna element, and arranged in parallel with and near the ground plate. By connecting the tip to the ground plate, the high-frequency impedance looking at the line side of λ / 4 from the feeding part becomes infinite, and it is possible to make a DC short-circuit structure without changing the input impedance of the antenna. The adverse effect on the wireless device can be reduced. Therefore, there is no need to separately add a guided lightning prevention device, and it is possible to configure the device at a low cost, and no extra mounting space is required.

[Brief description of the drawings]

FIG. 1 is a cross-sectional front view of a part of an antenna device according to an embodiment of the present invention.

FIG. 2 is a plan view of the embodiment.

FIG. 3 is a diagram showing a standing wave ratio characteristic of the antenna device according to the embodiment.

FIG. 4 is a diagram showing E-plane directivity characteristics of the antenna device according to the embodiment.

FIG. 5 is a configuration diagram of a conventional whip antenna.

FIG. 6 is a diagram showing an example of a conventional induced lightning countermeasure when an induced lightning prevention device is added.

FIG. 7 is a diagram showing an example of a conventional induced lightning countermeasure when the antenna element is of a folded type.

[Explanation of symbols]

11 antenna element, 12 insulator, 13 earth plate, 14 coaxial line, 14a center conductor, 14b outer conductor, 15 plug, 17 screw part, 18 λ / 4 line.

Claims (1)

(57) [Scope of request for utility model registration] 1. An antenna element having a length of approximately λ / 4.
Hold the base vertically with an insulator and
In whip antenna comprising holding the earth plate horizontally by the body, and branching the plate line of the feed section central conductor than a length substantially lambda / 4 of the antenna elements in the horizontal direction, lambda for the above earth plate A whip-type antenna device, wherein the whip-type antenna device is arranged in parallel with a spacing of not more than / 15 , and the tip is connected to the ground plate.