JPH0823221A - Circular antenna - Google Patents

Abstract

PURPOSE:To provide a circular antenna which can ensure its directivity suited to the shape of a radio zone while keeping the limit conditions to its attachment surface by setting plural feeding points to an exciting element that is placed on a conductor ground plate via a conductor. CONSTITUTION:The high frequency signals supplied via a feeder 11 are separately applied to the areas between the holes 451 and 452 and between the holes 121 and 122 respectively. The adverse L-shaped antennas are symmetrically formed around the axis of a cylindrical conductor 41 for an exciting element 42 and the conductor 41. If it is assumed that the phases of the high frequency signals supplied to both antennas are adverse to each other, the electromagnetic fields generated by both antennas are set vertical to a straight line connecting the holes 121 and 411 and almost offset on a surface parallel to the axis of the conductor 41 as a vector sum. In other words, the directivity in a truncated chervron shape is secured on an x-y plane that is equivalent to a horizontal surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring antenna installed in a mobile communication system to extend a wireless zone to a dead zone such as a tunnel.

[0002]

2. Description of the Related Art In recent years, mobile communication systems that provide communication services to automobiles and other mobile units have become widespread.
Many wireless base stations are installed in order to expand the wireless zone that can provide the communication service. Such a wireless zone is allocated to the 400 MHz band allocated for business communication related to vehicles, 90 allocated to car phones and others.
Although it is formed separately for the radio frequencies of the 0 MHz band and the 1500 MHz band, communication service is not provided in many tunnels because a dead zone is formed due to the rectilinearity of radio waves at these radio frequencies.

Conventionally, as a method for extending a wireless zone to such a dead zone, a booster system for directly bidirectionally relaying a wireless signal between the dead zone and a desired wireless zone has been adopted. An annular antenna is used to locally form a wireless zone.

FIG. 4 is a diagram showing a configuration example of a conventional annular antenna. In the drawing, as shown in FIG. 5, the openings at both ends of the cylindrical conductor 41 having a constant inner diameter have holes having the same inner diameter as the inner diameter, respectively, in the center, and are made of metal disks having different outer diameters. Exciting element 42 and conductor ground plate 43
However, these holes and the inner wall of the cylindrical conductor 41 are joined with their inner circumferences aligned. Here, for simplification, the outer shape of the excitation element 42 is smaller than the outer shape of the conductor ground plate 43. A hole 45 ₁ having a diameter substantially equal to that of the core wire of the power feed line 44 is formed at a point separated by a predetermined distance L from the center of the excitation element 42, and a point separated by a distance L from the center of the conductor ground plate 43 is also provided. Between the core wire of the electric wire 44 and the outer conductor, a hole 45 ₂ having a diameter substantially equal to that of the filled insulator is formed. The core wire of the power feed line 44 penetrates through the central portion of the hole 45 _{2 and} is joined to the hole 45 ₁ at its tip end by soldering or other method, and the outer conductor of the power feed line 44 is soldered to the conductor ground plate 43 by other method. To be joined. Further, the insulator of the power supply line 44 is supported while being inserted into the hole 45 ₂ .

In the annular antenna having such a configuration, the length of the cylindrical conductor 41 is set to 0.1λ or less with respect to the wavelength λ of the high frequency signal fed through the feeding line 44, and the diameter of the excitation element 42 is set. Is set to about 0.5λ. Cylindrical conductor 41
The outer surface and the excitation element 42 are inverse L-shaped antennas (or T-shaped antennas) in which a capacitor, which is considered to distribute most of the electric charge in the fed state, is arranged at the tip and grounded to the conductor ground plate 43. Operate.

Therefore, the antenna height can be suppressed to be significantly lower than that of a linear antenna having no bent portion,
The protrusion length with respect to the mounting surface and the required area of the mounting surface can be kept small.

Further, the directivity in the horizontal plane becomes non-directional, and the directivity in the vertical plane is shown in Technical Research Report AP86-56 "Resonant mode and directivity of the annular antenna" of the Institute of Electronics, Information and Communication Engineers. As described above, it has a shape of "8" similar to the half-wave dipole antenna.

That is, the propagation loss near the antenna (antenna gain due to directivity in the vertical plane) is suppressed to a small value, and the antenna gain in the distance is set large, and the polarization becomes vertical polarization perpendicular to the mounting surface. An efficient wireless transmission path is formed between the antenna mounted on the automobile.

Regarding the position where the core wire of the power feed line 44 and the outer conductor are connected, the distribution of the current on the excitation element 42 and the conductor ground plate 43 (the value becomes smaller as the distance from the junction with the cylindrical conductor 41 increases). .) Is set in advance at a point where the impedance corresponding to the characteristic impedance of the feeder line 44 matches, and impedance matching is achieved.

[0010]

By the way, such a conventional annular antenna is formed along a road such as a tunnel because the directivity in the horizontal plane is omnidirectional as described above. It was not suitable for the linear dead areas. Therefore, for example, to set the electric field level at the point farthest from the mounting surface to a desired value,
It is necessary to increase the power to be fed, as compared with the case where an antenna having a "8" -shaped directivity is used in the horizontal plane, or the level of a received wave coming from a mobile station located at such a point. In some cases, resulting in poor call quality.

An object of the present invention is to provide a toroidal antenna capable of obtaining directivity adapted to the shape of the wireless zone while maintaining the constraint condition for the mounting surface.

[0012]

According to the present invention, there is provided a conductor ground plate which is composed of a conductive plate-like body and forms a ground plate, a conductor whose one end is erected on the surface of the conductor ground plate and grounded. Radiation having a first feeding point adapted to the distribution of the current to the peripheral end, which is composed of a flexible plate and is mounted on a conductor ground plane via a conductor, and forms a top load type pole with the conductor In the ring antenna provided with the element, the radiating element has a second feeding point arranged at a position separated from the first feeding point, and has a main lobe in a predetermined direction perpendicular to the axis of the conductor. The present invention is characterized by including parallel feeding means for feeding parallel to the first and second feeding points according to the formed feeding phase and level difference.

[0013]

In the annular antenna according to the present invention, the second feeding point is added to a position on the radiating element separated from the first feeding point, and these feeding points are fed in parallel by the parallel feeding means. The radiating element acts as two independent top-loaded poles with the conductor by such parallel feeding,
Further, the feeding phase and level difference of the parallel feeding performed by the parallel feeding means are preset to values at which the main lobe is formed in a predetermined direction perpendicular to the axis of the conductor.

Therefore, by properly setting the mounting direction in advance with respect to the direction parallel to the mounting surface, the wireless zone adapted to the linearly distributed area while suppressing the increase of the required area and the protruding length of the mounting surface is efficient. Formed.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA 'in FIG. 1 and 2, parts having the same functions and configurations as those shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted here.

Phases of the configuration of this embodiment and the conventional example shown in FIG.
The difference is that instead of the power supply line 44, one end is branched into a two-way route.
An electric wire 11 is provided and a hole is provided through the center point of the excitation element 42.
45 ₁Hole 12 with the same diameter at a position symmetrical to₁Formed and led
A hole 45 is formed through the center point of the base plate 43.₂Diameter at a position symmetrical with
Same hole 12₂Is formed and the branched end of the power supply line 11
One of them has a hole 45 similar to the conventional feeder line 44.₂, 45
₁Connected to the conductor ground plane 43 and the excitation element 42 via
And the other is also hole 12₂, 12₁Through conductor ground plane 4
3 and the excitation element 42.

Regarding the correspondence relationship between this embodiment and the constituent elements described in claim 1, the conductor ground plate 43 corresponds to the conductor ground plate, the cylindrical conductor 43 corresponds to the conductor, and the excitation element 42 corresponds to the excitation element. Correspondingly, the power supply line 11 corresponds to a power supply means.

The operation of this embodiment will be described below with reference to FIGS. 1 and 2. The high-frequency signal fed via the power supply line 11 is individually provided between the holes 45 ₁ and 45 ₂ and between the holes 12 ₁ and 12 _2, and the excitation element 42 and the cylindrical conductor 41 are provided with the high-frequency signal. Two inverted L-shaped antennas symmetrically arranged about the axis of the cylindrical conductor 41 are formed.

Power is supplied to such two inverted L-shaped antennas.
Assuming that the phases of the high frequency signals are opposite to each other
And the electromagnetic field generated by these inverted L-shaped antennas is₁When
Hole 41 ₁The axis of the cylindrical conductor 41 that is perpendicular to the straight line connecting
On the plane parallel to, it is almost offset as a vector sum.

That is, from the center of the hole 45 ₂ to the cylindrical conductor 4
As shown in FIG. 3, the directivity of the xy plane corresponding to the horizontal plane with respect to the Cartesian coordinates in which the perpendicular to the axis of 1 is the x-axis and the axis is the z-axis, is shown in FIG. Becomes

The positions of the holes 12 ₁ and 12 ₂ are the same as the positions of the holes 45 ₁ and 45 _2.
Since it is determined by the impedance matching condition according to the current distribution on the conductor ground plate 43, the description thereof is omitted here.

As described above, according to the present embodiment, the simple structure in which the feeding point is newly added to the conventional ring antenna suppresses the increase of the required area of the mounting surface and the protruding length with respect to the mounting surface, and the inside of the tunnel. It is possible to form a wireless zone adapted to a line-shaped dead zone such as a road.

In the present embodiment, the tips of the two core wires of the power supply line 11 are connected to the holes 12 ₁ and 45 ₁ by penetrating through the central portions of the holes 12 ₂ and 45 ₂ , respectively. Is not limited to such a configuration, and if power feeding by these core wires is performed at a desired phase and power level, for example, the hole 12 _{1 is} passed through the hollow portion of the cylindrical conductor 41 or the vicinity of the outer periphery of the excitation element 42. , 45 ₁ and may not have these holes.

Further, in the present embodiment, the excitation element 42 is fed with the same impedance in the opposite phase, but the present invention is not limited to such a configuration, and the null point may be applied in a desired direction on the horizontal plane. If the above is formed, the position of the feeding point may be set by arbitrarily combining such feeding phases and impedances, or the mounting angle with respect to the direction parallel to the mounting surface may be freely set.

Further, in this embodiment, only the two core wires of the cylindrical conductor 41 and the feeder line 11 exist in the space sandwiched by the excitation element 42 and the conductor ground plate 43, but the present invention has such a configuration. However, if deterioration of gain, directivity, and other performances is suppressed to an acceptable range, for example, a dielectric may be mounted to reduce the size or facilitate impedance matching. .

Further, in the present embodiment, the outer peripheral shape of the excitation element 42 is substantially a perfect circle, but the present invention is not limited to such a configuration, and if a desired directivity can be obtained, a rectangular shape, It can also be a rhombus or other polygon.

Further, in the present embodiment, the outer peripheral shape of the conductor ground plate 43 is substantially a perfect circle, but the present invention is not limited to such a structure, and the reverse shape formed by the excitation element 42 and the cylindrical conductor 41 is used. If the grounding of the L-shaped antenna (or T-shaped antenna) is ensured, square, rectangular,
It may have a diamond shape or any other shape.

Further, in the present embodiment, the excitation element 42 and the conductor ground plate 43 are joined via the cylindrical conductor 41, but the present invention is not limited to such a structure, and for example, Instead of the cylindrical conductor, a conductive rod-shaped body having no hollow portion may be used.

Furthermore, in the present embodiment, the cylindrical conductor 41, the excitation element 42 and the conductor ground plate 43 are joined by soldering or other methods, but the present invention is not limited to such a configuration, for example, a machine tool. It is also possible to form them by integrally molding them, etc., or to divide them into a plurality of rotating bodies or other members in advance and mold them and then assemble them.

[0031]

As described above, according to the present invention, a plurality of feeding points are provided on the excitation element mounted on the conductor ground plane via the conductors, and the positions of these feeding points and the desired main lobe direction. Parallel feeding is performed with the feeding phase and level difference adapted to and.

That is, since the wireless zone is efficiently formed in the linear region while suppressing the increase of the required area of the mounting surface and the protruding length with respect to the mounting surface, the application of the present invention makes it possible to eliminate dead zones such as tunnels. In a mobile communication system with an expanded wireless zone, the electric field distance characteristic in the dead zone is improved and the service quality is enhanced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG.

FIG. 3 is a diagram showing directivity in a horizontal plane according to the present embodiment.

FIG. 4 is a diagram showing a configuration example of a conventional annular antenna.

5 is a cross-sectional view taken along the line AA ′ of FIG.

[Explanation of symbols]

 11,44 Feed line 12,45 Hole 41 Cylindrical conductor 42 Excitation element 43 Conductor ground plane

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshio Ebine Yoshio Ebine 2-10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Inc. (72) Naohisa Goto Dobashi, Miyamae-ku, Kawasaki City, Kanagawa Prefecture 6-15-1 Miyamaedaira Palm House A-514 (72) Inventor Hiroyuki Arai 615-11 Higashicho, Imajuku, Asahi-ku, Yokohama-shi, Kanagawa

Claims (1)

[Claims] 1. A conductor ground plate which is formed of a conductive plate body to form a ground plate, a conductor whose one end is erected on the surface of the conductor ground plate and grounded, and a conductive plate body. And a radiating element having a first feeding point adapted to the distribution of current to the peripheral end by forming a top load type pole together with the conductor on the conductor ground plane through the conductor. In the annular antenna, the radiating element has a second feeding point located apart from the first feeding point, and a main lobe is formed in a predetermined direction perpendicular to the axis of the conductor. An annular antenna comprising parallel feeding means for feeding parallel power to the first and second feeding points according to the feeding phase and level difference.