JP4987769B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device provided with a monopole antenna.

Conventionally, a monopole antenna is known as an omnidirectional antenna device for receiving or transmitting vertically polarized waves. In this monopole antenna, a cylindrical conductor having a length of ¼ of the wavelength of a radio wave is erected on a ground plate (for example, see Non-Patent Document 1).
Antenna Engineering Handbook, 50 pages, edited by IEICE, published by Ohmsha

  However, when attempting to receive or transmit radio waves of UHF (Ultra High Frequency) television broadcasting using a monopole antenna, there is a problem that the frequency band of the monopole antenna is narrow. For example, when a radio wave of 470 MHz is used as a reference, there is a problem that the height of the antenna is about 15 cm, and the size of the apparatus is increased.

  Therefore, a main object of the present invention is to provide a small and wideband antenna apparatus.

An antenna device according to the present invention includes a disk-shaped ground plate, a plurality of sub-ground plates that are arranged at equiangular intervals on a peripheral portion of the ground plate, and each provided substantially perpendicular to the ground plate, A monopole antenna erected at the center, a disk-shaped top capacitor provided at the top of the monopole antenna, and a monopole antenna disposed around the monopole antenna, each formed in a rod shape , And a plurality of conductive members that electrically connect the ground plate. The ground plate and the top capacitor are substantially the same diameter and are arranged in parallel to each other. The monopole antenna includes a plurality of antenna pieces, and each antenna piece is formed in a fan shape that becomes wider from the base end toward the tip, and the base end portions of the plurality of antenna pieces are coupled at the center portion of the ground plate. The feeding points are configured, and the tip portions thereof are arranged so as to open upward and are connected to the top capacitor body. The plurality of conductive members are respectively provided corresponding to the plurality of antenna pieces, and each conductive member is erected on the surface of the ground plate to support the corresponding antenna piece and the top capacitor.
Preferably, the plurality of sub ground plates are provided to face the plurality of antenna pieces, respectively.
Preferably, four sub-ground plates, conductive members, and antenna pieces are provided.

Further, another antenna device according to the present invention includes a disc-shaped ground plate, and a plurality of sub-ground plates that are arranged at equiangular intervals on the peripheral edge of the ground plate, each provided substantially perpendicular to the ground plate. A monopole antenna erected at the center of the ground plate, a disk-shaped top capacitor provided at the top of the monopole antenna, and a monopole antenna, each of which is formed in a rod shape A plurality of conductive members that electrically connect the top capacitor and the ground plate are provided. The ground plate and the top capacitor are substantially the same diameter and are arranged in parallel to each other. The monopole antenna is formed in a conical shape or a polygonal pyramid shape, and its apex portion is arranged at the center portion of the ground plate to form a feeding point, and its bottom peripheral edge is connected to the top capacitor body, and a plurality of conductive members Each is erected on the surface of the ground plate to support the top capacitor .

In the antenna device according to the present invention, since the disk-shaped top capacitor is provided on the monopole antenna, a large amount of charge can be stored at the top of the antenna, and the height of the antenna can be reduced. In addition, since the plurality of conductive members that electrically connect the top capacitor and the ground plate are provided, it is possible to increase the input resistance of the antenna that decreases with the installation of the top capacitor. In addition, the monopole antenna includes a plurality of antenna pieces, and each antenna piece is formed in a fan shape and arranged to open upward, so that the antenna height is lowered and the frequency band is widened. Can do. Further, since the ground plate is formed in a disc shape and the sub-ground plate is provided substantially perpendicularly to the periphery of the ground plate, the ground plate can be made small while maintaining a wide band.

In the other antenna device according to the present invention, the monopole antenna is provided with the disk-shaped top capacitor, so that a large amount of charge can be stored at the top of the antenna and the antenna height can be lowered. . In addition, since the plurality of conductive members that electrically connect the top capacitor and the ground plate are provided, it is possible to increase the input resistance of the antenna that decreases with the installation of the top capacitor. Further, since the monopole antenna is formed in a conical shape or a polygonal pyramid shape and is arranged to open upward, the antenna height can be lowered and the frequency band can be widened. Further, since the ground plate is formed in a disc shape and the sub-ground plate is provided substantially perpendicularly to the periphery of the ground plate, the ground plate can be made small while maintaining a wide band.

  FIG. 1A is a front view showing a configuration of an antenna device according to an embodiment of the present invention, FIG. 1B is a cross-sectional view taken along the line IB-IB in FIG. FIG. 1C is a plan view of the antenna device, and FIG. 1D is a diagram schematically showing the dimensions of the antenna device.

  1A to 1D, this antenna device includes a circular ground plate 1 that is horizontally disposed. The diameter of the ground plate 1 is, for example, 250 mm. Four sub-ground plates 2 are erected at equiangular intervals at the peripheral edge of the ground plate 1. The auxiliary grounding plate 2 is curved along the outer periphery of the grounding plate 1 and has a circumferential length of, for example, 50 mm and a height of, for example, 20 mm. The ground plate 1 and the four sub-ground plates 2 are formed, for example, by processing one copper thin plate. By providing the sub ground plate 2, it is possible to reduce the size of the ground plate 1 while maintaining a wide frequency band.

  A connector 3 for connecting a coaxial cable from below is fixed to the center of the lower surface of the ground plate 1. Connector 3 includes an external contact portion 3a to which the outer conductor of the coaxial cable is connected and an inner contact portion 3b to which the inner conductor of the coaxial cable is connected. External contact portion 3 a is mechanically and electrically coupled to the lower surface of ground plate 1. The upper end portion of the internal contact portion 3 b protrudes above the ground plate 1 through a through hole (not shown) opened in the center of the ground plate 1.

  A monopole antenna 4 is erected at the center of the ground plate 1. The monopole antenna 4 includes four antenna pieces 4a. Each antenna piece 4a is formed in a fan shape that gradually becomes wider from the base end toward the tip end. The base end portions of the four antenna pieces 4a are integrally formed to form a feeding point P, and the feeding point P is coupled to the upper end of the internal contact portion 3b. When viewed from above, the four antenna pieces 4 a are arranged at equal angular intervals around the feeding point P, and their tips are arranged to face the four sub-ground plates 2, respectively. Further, when viewed from the lateral direction, each antenna piece 4 a is disposed obliquely with respect to the ground plate 1, and its tip is bent so as to be parallel to the ground plate 1.

  The width of the tip of the antenna piece 4a is 78 mm, for example, and its height is 50 mm, for example. Further, the distance between the tips of the two antenna pieces 4a arranged to face each other is, for example, 180 mm. The monopole antenna 4 is formed, for example, by processing one copper thin plate. By adopting the monopole antenna 4 having such a shape, the frequency band can be expanded and the height can be lowered.

  A disc-shaped top capacitor 5 is provided on the top of the monopole antenna 4. The top capacitor body 5 is arranged in parallel to the ground plate 1, and the lower surface of the top capacitor body 5 is fixed to the tip portions of the four antenna pieces 4a. The top capacitor body 5 is formed of, for example, a circular copper thin plate having a diameter of 250 mm. Since a large amount of electric charge is present at the top of the monopole antenna 4, the height of the antenna can be reduced by providing the top capacitor 5 that accumulates the electric charge.

  A bar-like conductive member 6 is provided between the upper surface of the ground plate 1 and the lower surface of the tip of each antenna piece 4a. The conductive member 6 electrically connects the ground plate 1, the antenna piece 4 a, and the top capacitor body 5, and supports the antenna piece 4 a and the top capacitor body 5. The conductive member 6 is formed of, for example, a copper rod having a length of 50 mm. When the top capacitor 5 is provided, the input resistance value of the antenna device is reduced, but by providing the conductive member 6, the input resistance value can be increased. By providing the plurality of conductive members 6, the input resistance value of the antenna device can be set to a desired value.

  FIG. 2 is a diagram showing frequency characteristics of the gain and VSWR (Voltage Standing Wave Ratio) of the antenna device. From FIG. 2, it can be seen that this antenna device has a sufficiently high gain in the UHF television broadcast frequency band (470 to 770 MHz) and a sufficiently low VSWR. Moreover, Fig.3 (a)-(c) is a figure which shows the frequency characteristic of the directivity of this antenna apparatus. 3 (a) to 3 (c), it can be seen that this antenna device exhibits good omnidirectionality at 470 to 770 MHz.

  In this embodiment, four sub-ground plates 2 are erected on the periphery of the ground plate 1, and the monopole antenna 4 is configured by four fan-shaped antenna pieces 4a arranged to open upward. Since the disk-shaped top capacitor body 5 is provided on the top of the monopole antenna 4 and the top capacitor body 5 and the ground plate 1 are connected by the conductive member 6, a broadband and small antenna device can be realized.

  As shown in FIGS. 4A and 4B, the monopole antenna 4 may be replaced with a conical monopole antenna 10 or as shown in FIGS. 5A and 5B. The antenna 4 may be replaced with a monopole antenna 11 having a polygonal pyramid shape (an octagonal pyramid shape in the figure). The center lines of the antennas 10 and 11 are arranged perpendicular to the ground plate 1. Each of the antennas 10 and 11 is disposed so as to open upward with the apex portion down. The apex portions of the antennas 10 and 11 constitute a feeding point P and are connected to the upper end of the internal contact portion 3 b of the connector 3, and the bottom peripheral portion thereof is connected to the top capacitor 5. Even in these modified examples, the same effect as the embodiment can be obtained.

  Further, as shown in FIG. 6A, the top capacitor body 5 may be replaced with an annular top capacitor body 12, and as shown in FIG. 6B, the top capacitor body 5 is formed in a cross shape. The top capacitor 13 may be replaced, or as shown in FIG. 6C, the top capacitor 5 may be replaced with a top capacitor 14 having a shape in which a disk and a cross shape are overlapped. Each of the top capacitors 12 to 14 is connected to the ground plate 1 through a plurality of conductive members 6, similarly to the top capacitor 5. Even in these modified examples, the same effect as the embodiment can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the antenna apparatus by one embodiment of this invention. It is a figure which shows the gain characteristic of the antenna apparatus shown in FIG. 1, and the frequency characteristic of VSWR. It is a figure which shows the frequency characteristic of the directivity of the antenna apparatus shown in FIG. It is a figure which shows the example of a change of embodiment. It is a figure which shows the other example of a change of embodiment. It is a figure which shows the further another example of a change of embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Grounding board, 2 Sub grounding board, 3 Connector, 3a External contact part, 3b Internal contact part, 4,10,11 Monopole antenna, 4a Antenna piece, 5,12-14 Top capacity body, 6 Conductive member, P feeding point.

Claims (4)

A disk-shaped ground plate;
A plurality of sub-grounding plates arranged at equiangular intervals on the periphery of the grounding plate, each provided substantially perpendicular to the grounding plate;
A monopole antenna erected at the center of the ground plate;
A disk-shaped top capacitor provided on the top of the monopole antenna;
A plurality of conductive members disposed around the monopole antenna, each of which is formed in a rod shape and electrically connects the top capacitor and the ground plate;
The ground plate and the top capacitor body are substantially the same diameter and arranged in parallel to each other,
The monopole antenna includes a plurality of antenna pieces,
Each antenna piece is formed in a fan shape that becomes wider from the base end toward the tip end.
The base end portions of the plurality of antenna pieces are coupled at the center portion of the ground plate to form a feeding point, and the tip portions thereof are arranged to open upward and connected to the top capacitor body ,
The plurality of conductive members are respectively provided corresponding to the plurality of antenna pieces, and each conductive member is erected on the surface of the ground plate to support the corresponding antenna piece and the top capacitor body. An antenna device is characterized. The antenna device according to claim 1, wherein the plurality of sub-grounding plates are provided to face the plurality of antenna pieces, respectively. The antenna device according to claim 1, wherein four each of the sub ground plate, the conductive member, and the antenna piece are provided. A disk-shaped ground plate;
A plurality of sub-grounding plates arranged at equiangular intervals on the periphery of the grounding plate, each provided substantially perpendicular to the grounding plate;
A monopole antenna erected at the center of the ground plate;
A disk-shaped top capacitor provided on the top of the monopole antenna;
A plurality of conductive members disposed around the monopole antenna, each of which is formed in a rod shape and electrically connects the top capacitor and the ground plate;
The ground plate and the top capacitor body are substantially the same diameter and arranged in parallel to each other,
The monopole antenna is formed in a conical shape or a polygonal pyramid shape, and its apex portion is arranged at the center portion of the ground plate to form a feeding point, and its bottom periphery is connected to the top capacitor ,
Each of the plurality of conductive members is erected on the surface of the ground plate to support the top capacitor body .

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