JP2000059129A - Monopole antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized monopole antenna capable of plural frequency operations with a simple structure. SOLUTION: A disk conductor 22, a ring-like conductor 24 and the ring-like conductor 26 are arranged on the same plane and arranged concentrically in an order from an inner side. The end part of a straight conductor 21 is vertically connected to the center of the disk conductor 22 and the outer edge part of the disk conductor 22 is connected to the inner edge part of the ring-like conductor 24 through an antiresonance circuit 23. Further, the outer edge part of the ring-like conductor 24 is connected to the inner edge part of the ring-like conductor 26 through the antiresonance circuit 25. A circuit is electrically interrupted by the antiresonance circuits 23 and 25, the radio waves of a first frequency f1 are excited by a system composed of the straight conductor 21 and the disk conductor 22, the radio waves of a second frequency f2 are excited by the system from the straight conductor 21 to the ring-like conductor 24 and the radio waves of a third frequency f3 are excited by the system from the straight conductor 21 to the ring-like conductor 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monopole antenna mainly used in mobile communication, and more particularly to a monopole antenna suitable for a base station antenna.

[0002]

2. Description of the Related Art FIG. 20 shows a conventional monopole antenna composed of one antenna element and exciting radio waves of two frequencies.
2 shows an antenna. In FIG. 20, reference numeral 91 denotes a disc-shaped ground conductor, 92 denotes a feeder located at the center of the ground conductor 91, 9
Reference numeral 3 denotes an antenna element made of a linear conductor. The antenna element 93 has a coil 93a at the center thereof, and one end of the antenna element 93 is connected to a ground conductor 91.
Are electrically connected to a feeder 92 located at the center of the power supply so as to be perpendicular to the ground conductor 91.

In this case, in the antenna element 93,
A lower frequency radio wave is excited in the entire antenna element,
Radio waves of a higher frequency are excited in the same phase above and below the coil 93a by the center coil 93a. As a result, a two-frequency operating monopole that resonates at different frequencies
An antenna has been realized.

[0004]

However, in the above-mentioned conventional monopole antenna, the height of the antenna element 93 is １ ／ wavelength of the lower excitation frequency or 以上 wavelength of the higher excitation frequency. Since it is necessary, the height of the antenna element 93 is increased, and it is difficult to reduce the size. In addition, since excitation of radio waves having close frequencies is impossible in terms of structure, the frequency to be excited is limited. Practically, it is up to two-frequency operation.

When the above-described conventional monopole antenna is installed on a ceiling or the like in a room, in order to improve the efficiency of radio wave radiation of the antenna, the antenna element 93 faces a space from which radio waves are radiated. As described above, it is desirable that the antenna is suspended upside down and installed facing the floor. Further, in this case, it is desirable that there is nothing obstructing the propagation of radio waves between the antenna element 93 and all the radiation spaces, and it is desirable that all the radiation target spaces can be seen from the antenna element 93. Further, there is a demand that the monopole antenna be installed as inconspicuous as possible in view of the scenery. However, as described above, the antenna element 93 becomes a protrusion from the ceiling, and as described above, the antenna element 93 is not used in the conventional monopole antenna. Is not preferable from the viewpoint of landscape.

The present invention has been made to solve the above-mentioned problems in the prior art, and has as its object to provide a small-sized monopole antenna capable of operating at a plurality of frequencies with a simple structure.

[0007]

To achieve the above object, a first configuration of a monopole antenna according to the present invention comprises a ground conductor and one end connected to a feeder located on the surface of the ground conductor. A straight conductor, a flat conductor connected to the other end of the straight conductor, and a ring conductor whose inner edge is connected to the outer edge of the flat conductor via an anti-resonance circuit. And According to the first configuration of the monopole antenna, by setting the resonance frequency of the anti-resonance circuit to f1, the anti-resonance circuit has a high impedance at the frequency f1, and the disk conductor and the ring-shaped conductor are electrically disconnected. Therefore, the first frequency f1 can be excited by the system composed of the linear conductor and the plate-shaped conductor, and the second frequency f2 can be excited by the system from the linear conductor to the ring-shaped conductor. Here, if the flat conductor is connected vertically to the straight conductor, and the loop conductor is arranged on the same plane as the flat conductor, the height of the antenna portion composed of the straight conductor, the flat conductor, and the loop conductor is determined. Can be lowered. Therefore, according to the first configuration of the monopole antenna of the present invention, it is possible to realize a monopole antenna capable of operating at a plurality of frequencies with a compact and simple structure.

In the first configuration of the monopole antenna according to the present invention, it is preferable that at least one of the flat conductor and the annular conductor is connected to the ground conductor by a ground conductor wire. According to this preferred example,
The input impedance of the antenna at each operating frequency can be increased. As a result, the antenna input impedance at each operating frequency of the present antenna and the impedance matching state of the impedance with the feeding unit are improved, so that the characteristics of the antenna can be improved.

Further, in the first configuration of the monopole antenna according to the present invention, even if the flat conductor and the annular conductor are arranged on the same plane, the flat conductor and the annular conductor are on different planes. It may be arranged in.

Further, in the first configuration of the monopole antenna according to the present invention, the ring-shaped conductor is composed of a plurality of ring-shaped conductors, and the opposed inner edge and outer edge of the adjacent ring-shaped conductor are connected via an anti-resonance circuit. It is preferable that they are connected. According to this preferred example, a monopole antenna capable of operating at three or more frequencies can be realized. In this case, it is preferable that at least one of the flat conductor and the plurality of annular conductors is connected to the ground conductor by a ground conductor wire. In some cases, there is a ring-shaped conductor whose impedance is sufficiently matched, and in this case, it is not necessary to perform matching using a ground conductor wire. In particular, there is a possibility that the impedance matching of the innermost plate-shaped conductor, ring-shaped conductor, and the like is sufficiently achieved. Also,
In this case, the flat conductor and the plurality of annular conductors may be arranged on the same plane, or at least one of the plurality of annular conductors may be arranged on a plane different from the flat conductor.

In the first configuration of the monopole antenna according to the present invention, it is preferable that the flat conductor is a disc conductor. In this case, the feeder is located at the center of the surface of the ground conductor, one end of the straight conductor is connected to the feeder perpendicular to the ground conductor, and the other end of the straight conductor is perpendicular to the flat conductor. Are connected at the center of the flat conductor,
It is preferable that the annular conductor is arranged concentrically with the flat conductor.

Further, in the first configuration of the monopole antenna according to the present invention, it is preferable that the anti-resonance circuit is a parallel circuit of a coil and a capacitor.

In the first configuration of the monopole antenna according to the present invention, it is preferable that the anti-resonance circuit is a circuit including only a coil. According to this preferred example, the number of parts can be reduced.

In the first configuration of the monopole antenna according to the present invention, it is preferable that the flat conductor, the anti-resonance circuit, and the ring conductor are formed in a pattern on the dielectric substrate. According to this preferred example, by adjusting the anti-resonance circuit pattern, electrical cutoff can be performed at a desired frequency.

In the first configuration of the monopole antenna according to the present invention, an electrical connection is provided between the ground conductor and the ground conductor on a side opposite to the side on which the flat conductor is arranged, via a space. Preferably, a reflective conductor for effecting the coupling is provided. According to this preferred example, the following effects can be obtained. That is, electric current also flows through the reflective conductor through a space through electrical coupling, and thus radio waves are also emitted from the end of the reflective conductor. Therefore, the radiation of the radio wave from the monopole antenna is the sum of the radiation from the ground conductor, the radiation from the antenna body consisting of the straight conductor, the flat conductor and the ring conductor, and the radiation from the reflection conductor, By changing the size of the conductor and the reflective conductor, or the distance between the ground conductor and the reflective conductor,
It is possible to change the directivity of the monopole antenna. In this case, it is preferable that the reflection conductor is electrically connected to the ground conductor. According to this preferred example, the following effects can be obtained. In other words, the reflective conductor electrically connected to the ground conductor also functions as a ground conductor in addition to the function of the reflective conductor. The input impedance can be stabilized. In this case, it is preferable that the reflection conductor is composed of a plurality of reflection conductors, and at least one of the plurality of reflection conductors is electrically connected to a ground conductor. Also,
In this case, the ground conductor and the reflective conductor have a surface shape, and are arranged with their surfaces facing each other, and
Preferably, the area of the reflection conductor is larger than the area of the ground conductor. According to this preferred example, since the spatial coupling between the ground conductor and the reflective conductor is strengthened, radio waves can be efficiently emitted from the reflective conductor.

In a second configuration of the monopole antenna according to the present invention, the ground conductor, a linear conductor having one end connected to a feeder located on the surface of the ground conductor, A ring-shaped conductor connected to the other end of the conductor via an anti-resonance circuit is provided.

Further, in the second configuration of the monopole antenna according to the present invention, it is preferable that the ring-shaped conductor is connected to the ground conductor by a ground conductor wire.

In the second configuration of the monopole antenna according to the present invention, the ring-shaped conductor is composed of a plurality of ring-shaped conductors, and the opposing inner edge and outer edge of the adjacent ring-shaped conductor are connected via an anti-resonance circuit. It is preferable that they are connected. In this case, it is preferable that at least one of the plurality of ring-shaped conductors is connected to the ground conductor by a ground conductor wire. In this case, the plurality of ring-shaped conductors may be arranged on the same plane, or at least one of the plurality of ring-shaped conductors may be arranged on a different plane. Further, in this case, it is preferable that the power supply unit is located at the center of the surface of the ground conductor, and the plurality of ring-shaped conductors are arranged concentrically.

In the second configuration of the monopole antenna according to the present invention, it is preferable that the anti-resonance circuit is a parallel circuit of a coil and a capacitor.

In the second configuration of the monopole antenna according to the present invention, it is preferable that the anti-resonance circuit is a circuit including only a coil.

In the second configuration of the monopole antenna according to the present invention, it is preferable that the anti-resonance circuit and the ring-shaped conductor are pattern-formed on a dielectric substrate.

Further, in the second configuration of the monopole antenna according to the present invention, an electrical connection is provided between the ground conductor and the ground conductor on the side opposite to the side where the flat conductor is disposed, via a space. Preferably, a reflective conductor for effecting the coupling is provided. In this case, it is preferable that the reflection conductor is electrically connected to the ground conductor. In this case, it is preferable that the reflection conductor is composed of a plurality of reflection conductors, and at least one of the plurality of reflection conductors is electrically connected to a ground conductor. Further, in this case, it is preferable that the ground conductor and the reflective conductor have a surface shape and are arranged with their surfaces facing each other, and that the area of the reflective conductor is larger than the area of the ground conductor. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments.

<First Embodiment> First, the first embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 1, 2, and 3. FIG.

FIG. 1 is a schematic perspective view showing a monopole antenna according to the first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a disc-shaped ground conductor, and 12 denotes a ground conductor 11.
, And 13 indicate antenna elements, respectively. The feeder 12 is located on the surface of the ground conductor 11, and the antenna element 13 is electrically connected to the feeder 12 perpendicular to the ground conductor 11.

FIG. 2 is a schematic perspective view showing the antenna element in FIG. Here, as an example, a case of a three-frequency operation monopole antenna is shown. 2, reference numeral 21 denotes a linear conductor, 22 denotes a disk conductor, 23 denotes an anti-resonance circuit, 24 denotes a ring-shaped conductor, 25 denotes an anti-resonance circuit, and 26 denotes a ring-shaped conductor. Here, the disk conductor 22, the ring-shaped conductor 24, and the ring-shaped conductor 26 are arranged on the same plane, and are arranged concentrically in order from the inside.
At the center of the disc conductor 22, the upper end of the straight conductor 21 is electrically connected vertically to the disc conductor 22.
2 is connected to the inner edge of the ring-shaped conductor 24 via the anti-resonance circuit 23. Further, the outer edge of the ring-shaped conductor 24 is connected to the inner edge of the ring-shaped conductor 26 via an anti-resonance circuit 25.

The anti-resonance circuits 23 and 25 are formed by a parallel circuit of a coil 31 and a capacitor 32, for example, as shown in FIG.

The operation of the monopole antenna having the above configuration will be described below.

First, before describing the operation of the monopole antenna (operation of a plurality of frequencies of the antenna element), a top-loading type monopole antenna which is a basic configuration of the present monopole antenna will be described.

FIG. 5A is a schematic perspective view showing a top-loading type monopole antenna, and FIG. 5B is a schematic perspective view showing the antenna element in FIG. 5A. In FIG. 5A, reference numeral 11 denotes a ground conductor, 12 denotes a feeding unit, and 13 denotes an antenna element. In FIG. 5B, reference numeral 21 denotes a linear conductor, and reference numeral 22 denotes a disk conductor.

As shown in FIG. 5B, the antenna element 13 of the top-loading type monopole antenna is composed of a straight conductor 21 and a disc conductor 22. In this case, the upper end of the linear conductor 21 is electrically connected to the center of the disc conductor 22 vertically to the disc conductor 22. It is considered that the disc conductor 22 forms a capacitor with the ground conductor 11, and the antenna element 13 in this case is equivalent to a capacitive load connected to the upper end of the linear conductor 21. . This is shown in FIG. In FIG. 6, 51 indicates an equivalent capacitor, and 52 and 53 indicate transmission lines, respectively. In FIG. 6, λ indicates a free space wavelength, f indicates a frequency, and the length h ′ of the transmission line 53 indicates the length of a portion of the antenna element 13 lowered by top loading. As shown in FIG. 6, the antenna element 13 of the top-loading monopole antenna has a capacitance C
And a normal quarter-wavelength monopole antenna element can be represented as a transmission line 52 connected to a transmission line 53 having an open-ended line length h ′. Can be. That is, the impedance when the capacitor 51 is viewed from the transmission line 52,
The length h ′ of the portion where the antenna element 13 is lowered by the top loading is determined so that the impedance when the transmission line 53 is viewed from the transmission line 52 becomes equal.
Since the capacitance C of the antenna element 13 of the top-loading type monopole antenna is proportional to the diameter of the disk conductor 22, the diameter of the disk conductor 22 and the height of the antenna element 13 when the resonance frequency is kept constant based on this concept. FIG. 7 shows the relationship between the two. As shown in FIG.
By increasing the size of the disc conductor 22, the height of the antenna element 13 can be reduced.

The monopole antenna of this embodiment is
A plurality of top-loading monopole antennas resonating at a predetermined frequency designed by the above design method are combined into one.

Excitation of the radio wave is performed in such a manner that the first frequency f 1 is a system composed of the linear conductor 21 and the disc conductor 22 and the second frequency f 1
2 is a system from the linear conductor 21 to the ring-shaped conductor 24, and the third frequency f3 is performed in a system from the linear conductor 21 to the ring-shaped conductor 26. In this case, the first frequency f1 is the highest, the second frequency f2 is the next highest, and the third frequency f3 is the highest.
Is the lowest.

In order to excite radio waves as described above,
At the first frequency f1, the annular conductors 24 and 26 are
Electrically disconnects from the system consisting of
It is necessary to electrically cut off the ring-shaped conductor 26 from the system from the linear conductor 21 to the ring-shaped conductor 24 at the frequency f2. For this reason, the anti-resonance circuit 23 is used to connect the outer edge of the disc conductor 22 and the inner edge of the ring-shaped conductor 24, and the ring-shaped conductor 2
An anti-resonance circuit 25 is used to connect the outer edge of the ring-shaped conductor 4 to the inner edge of the ring-shaped conductor 26. The resonance frequency of the anti-resonance circuit 23 is set to the first frequency f1. As a result, the anti-resonance circuit 23 has a high impedance at the first frequency f1, and the disk conductor 22 and the ring-shaped conductor 24 are electrically disconnected. Therefore, an antenna that resonates at the first frequency f1 is realized by the straight conductor 21 and the disc conductor 22. At a frequency lower than the first frequency f1, the anti-resonance circuit 23 has a low impedance, and the disk conductor 22 and the ring-shaped conductor 24 are substantially in a conductive state.

Similarly, if the resonance frequency of the anti-resonance circuit 25 is adjusted to the second frequency f2, and the ring-shaped conductor 24 and the ring-shaped conductor 26 are electrically cut off at the second frequency f2, the linear conductor 21 is changed to the ring-shaped conductor. With the system up to 24, the second frequency f
2 realizes an antenna that resonates. At a frequency lower than the second frequency f2, the anti-resonance circuit 25 has a low impedance, and the ring-shaped conductor 24 and the ring-shaped conductor 26 are substantially in a conductive state.

As described above, different frequencies f1, f2, f
A multi-frequency operating monopole antenna operating at 3 is realized.

In the monopole antenna according to the present embodiment, the feeder 12 is located at the center of the surface of the disc-shaped ground conductor 11, and the straight conductor 21 is perpendicular to the disc conductor 22. And the ring-shaped conductors 24, 26
Are arranged concentrically with the disk conductor 22,
Because of the axially symmetric structure, it is possible to radiate omnidirectional radiation in the lateral direction of the antenna.

FIG. 8 shows antenna characteristics of the monopole antenna according to the present embodiment. FIG. 8A shows the VSWR characteristics of the input impedance of the prototype antenna, and FIG. 8B shows the radiation characteristics of the prototype antenna.

As shown in FIG. 8A, the monopole
The antenna resonates at frequencies f1, f2, f3.

In FIG. 8B, as an example, the frequency f1
, F2, the radiation characteristics of a normal monopole antenna alone and the radiation characteristics of the present monopole antenna are shown for comparison. As shown in FIG. 8 (b), the present monopole antenna is operable at a plurality of frequencies, and further has characteristics equal to those of the monopole antenna alone at each operating frequency.

As described above, according to the present embodiment, it is possible to operate at a plurality of frequencies with a compact and simple structure, and to exhibit the same characteristics as those of the monopole antenna alone at each operating frequency. Monopole antenna can be realized.

Further, in the present embodiment, the anti-resonance circuits 23 and 25 are configured by a parallel circuit of the coil 31 and the capacitor 32, but the anti-resonance circuits 23 and 25 are not necessarily limited to this configuration.

Further, in this embodiment, all the anti-resonance circuits 23 and 25 are configured by a parallel circuit of the coil 31 and the capacitor 32, but the present invention is not limited to this configuration. Circuit 23 or 2
5 may be configured by a parallel circuit of a coil 31 and a capacitor 32, and the remaining anti-resonance circuit 25 or 23 may be configured by only the coil 31.

<Second Embodiment> Next, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 1, 2, and 4. FIG.

The configuration of the monopole antenna of the present embodiment is the same as that of the first embodiment (FIG. 1).
reference). Further, the configuration of the antenna unit of the present embodiment is the same as the configuration of the first embodiment (see FIG. 2).
However, in the present embodiment, the anti-resonance circuits 23, 25
Is composed of only the coil 41 as shown in FIG. 4, for example.

The operation of the monopole antenna of this embodiment is the same as the operation of the monopole antenna of the first embodiment. The high-frequency cutoff characteristics are used. That is, by selecting a coil 41 of an appropriate size, the coil 41 has a high impedance at a desired frequency, and the disc conductor 22 and the ring conductor 24 in FIG.
The ring-shaped conductor 24 and the ring-shaped conductor 26 can be substantially electrically disconnected. At lower frequencies, coil 4
1 has a low impedance and becomes almost conductive. Thereby, a monopole antenna operable at a plurality of frequencies can be realized.

Further, according to the present embodiment, the anti-resonance circuits 23 and 25 are constituted only by the coil 41, so that the number of parts can be reduced.

As described above, according to the present embodiment, it is possible to operate at a plurality of frequencies with a very simple structure.
An excellent monopole antenna exhibiting characteristics equal to those of the monopole antenna alone at each operating frequency can be realized.

In this embodiment, all the anti-resonance circuits 23 and 25 are constituted only by the coil 41. However, the present invention is not limited to this structure. And the remaining anti-resonance circuit 25 or 23 is
And a capacitor in parallel.

<Third Embodiment> Next, a third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 1, 3, and 9. FIG.

The configuration of the monopole antenna of this embodiment is the same as that of the first embodiment (FIG. 1).
reference).

FIG. 9 is a schematic perspective view showing the antenna element in FIG. Here, a case of a three-frequency operating monopole antenna is shown as an example. In FIG. 9, 2
1 is a linear conductor, 22 is a disk conductor, 23 is an anti-resonant circuit, 2
4 is an annular conductor, 25 is an anti-resonant circuit, 26 is an annular conductor, 6
1, 62 and 63 indicate ground conductor lines, respectively. Here, the disk conductor 22, the annular conductor 24, and the annular conductor 26
Are arranged on the same plane and are arranged concentrically in order from the inside. In the center of the disk conductor 22,
The ends of the linear conductors 21 are vertically connected, and the outer edges of the disk conductors 22 are connected to the inner edges of the ring-shaped conductors 24 via the anti-resonance circuit 23. Further, the outer edge of the ring-shaped conductor 24 is connected to the inner edge of the ring-shaped conductor 26 via an anti-resonance circuit 25. Further, the disk conductor 22, the ring-shaped conductor 24, and the ring-shaped conductor 26 are connected to the ground conductor 11 (see FIG.
See).

The anti-resonance circuits 23 and 25 are constituted by a parallel circuit of a coil 31 and a capacitor 32, for example, as shown in FIG.

The operation of the monopole antenna of the present embodiment is the same as the operation of the monopole antenna of the first embodiment.

In the monopole antenna according to the first embodiment, the antenna height is kept low by using the disk conductor 22 and the ring-shaped conductors 24 and 26 for the antenna element 13. However, when such a configuration is employed, the input impedance of the antenna may be reduced at each operating frequency of the antenna, and the impedance matching state with the power supply unit 12 may be deteriorated. When the impedance matching state with the power supply unit 12 deteriorates, the power supplied to the antenna element decreases, and the radiation efficiency of the antenna decreases.

In this case, by increasing the input impedance of the antenna at each operating frequency, the feeder 12
It is necessary to improve the impedance matching with the antenna and to improve the characteristics of the antenna.

For this reason, the disc conductor 22 and the ring conductor 24,
26 is connected to the ground conductor 11 by ground conductor lines 61, 62 and 63, respectively. As a result, the input impedance of the present antenna increases at each operating frequency. As a result, the matching state between the antenna input impedance at each operating frequency of the present antenna and the impedance of the feed unit 12 is improved, and the characteristics of the antenna are improved. Be improved.

As described above, according to the present embodiment, it is possible to improve the matching state between the input impedance of the antenna and the impedance of the feeder, and to obtain a monopole at a plurality of frequencies with excellent radiation efficiency of the antenna. -A monopole antenna capable of antenna operation can be realized.

In the monopole antenna according to the present embodiment, the feeder 12 is located at the center of the surface of the disc-shaped ground conductor 11, and the straight conductor 21 is perpendicular to the disc conductor 22. And the ring-shaped conductors 24, 26
Are arranged concentrically with the disk conductor 22,
Since it has an axisymmetric structure, it is possible to radiate omnidirectional radiation in the lateral direction of the antenna.

Further, in this embodiment, the anti-resonance circuits 23 and 25 are configured by a parallel circuit of the coil 31 and the capacitor 32, but the anti-resonance circuits 23 and 25 are not necessarily limited to this configuration.

Further, in this embodiment, all the anti-resonance circuits 23 and 25 are constituted by the parallel circuit of the coil 31 and the capacitor 32, but the invention is not necessarily limited to this configuration, and any one of the anti-resonance circuits Circuit 23 or 2
5 may be configured by a parallel circuit of a coil 31 and a capacitor 32, and the remaining anti-resonance circuit 25 or 23 may be configured by only the coil 31.

Further, in this embodiment, the disk conductor 22 and the ring-shaped conductors 24 and 26 are all grounded to the ground conductor 11, but at least one of the disk conductor 22 and the ring-shaped conductors 24 and 26 is connected to the ground conductor 11. It only needs to be grounded.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 1, 4, and 9. FIG.

The configuration of the monopole antenna of the present embodiment is the same as the configuration of the first embodiment (FIG. 1).
reference). Further, the configuration of the antenna element of the present embodiment is as follows:
The configuration is the same as that of the third embodiment (see FIG. 9).

The anti-resonance circuits 23 and 25 are composed of only a coil 41, for example, as shown in FIG.

The operation of the monopole antenna according to the present embodiment is the same as the operation of the monopole antenna according to the third embodiment. The high-frequency cutoff characteristics are used. That is, by selecting a coil 41 having an appropriate size, the coil 41 has a high impedance at a desired frequency, and the disc conductor 22 and the ring conductor 24 in FIG.
The ring-shaped conductor 24 and the ring-shaped conductor 26 can be substantially electrically disconnected. At lower frequencies, coil 4
1 has a low impedance and becomes almost conductive. Thereby, a monopole antenna operable at a plurality of frequencies can be realized.

Further, according to the present embodiment, since the anti-resonance circuits 23 and 25 are constituted only by the coil 41, the number of parts can be reduced.

As described above, according to the present embodiment, it is possible to operate at a plurality of frequencies with a very simple structure.
It is possible to realize an excellent monopole antenna which exhibits characteristics equal to those of the monopole antenna alone at each operating frequency and has good radiation efficiency.

In this embodiment, the disk conductor 2
2 and the ring-shaped conductors 24 and 26 are all grounded to the ground conductor 11, but it is sufficient that at least one of the disk conductor 22 and the ring-shaped conductors 24 and 26 is grounded to the ground conductor 11.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 1, 10, and 11. FIG.

The configuration of the monopole antenna of the present embodiment is the same as the configuration of the first embodiment (FIG. 1).
reference).

FIG. 10 is a schematic perspective view showing the antenna element in FIG. Here, a case of a three-frequency operating monopole antenna is shown as an example. In FIG. 10, 21 is a linear conductor, 22 is a disk conductor, 23 is an anti-resonant circuit, 24 is a ring-shaped conductor, 25 is an anti-resonant circuit, 26 is a ring-shaped conductor, and 71 is a dielectric substrate. here,
The disk conductor 22, the ring-shaped conductor 24, and the ring-shaped conductor 26 are arranged on the same plane, and are arranged concentrically in order from the inside. The end of the linear conductor 21 is vertically connected to the center of the disc conductor 22, and the outer edge of the disc conductor 22 is connected to the inner edge of the ring-shaped conductor 24 via the anti-resonance circuit 23. Further, the outer edge of the ring-shaped conductor 24 is connected to the inner edge of the ring-shaped conductor 26 via an anti-resonance circuit 25. The disk conductor 22, the ring-shaped conductors 24 and 26, and the anti-resonance circuits 23 and 25 are pattern-formed on the dielectric substrate 71.

FIG. 11 shows the anti-resonance circuit 23 in FIG.
25 shows a metal conductor pattern on the dielectric substrate 71, and 81 shows a metal pattern on the dielectric substrate 71. The pattern of the anti-resonance circuits 23 and 25 is, for example, as shown in FIG.
As shown in the figure, the circuit is composed of a parallel circuit of a coil pattern 82 and a capacitor pattern 83. Then, the coil pattern 82 and the capacitor pattern 8
By adjusting 3, it becomes possible to electrically cut off at a desired frequency, and the present monopole antenna can be operated as a monopole antenna capable of operating at a plurality of frequencies.

As described above, according to the present embodiment, it is possible to improve the fabrication accuracy and stability of the antenna element and realize an excellent monopole antenna that can operate at a plurality of frequencies.

In this embodiment, the patterns of all the anti-resonance circuits 23 and 25 are
And the parallel pattern of the capacitor pattern 83, but is not necessarily limited to this configuration, and the pattern of one of the anti-resonance circuits 23 or 25 is replaced by the parallel circuit of the coil pattern 82 and the capacitor pattern 83. And the remaining pattern of the anti-resonance circuit 25 or 23 may be constituted only by the coil pattern 82.

Further, in this embodiment, all the anti-resonance circuits 23 and 25 are patterned on the dielectric substrate 71, but either of the anti-resonance circuits 23 or 25 is formed on the dielectric substrate 71. A configuration in which a pattern is formed and the remaining anti-resonance circuit 25 or 23 is not formed on the dielectric substrate 71 may be adopted.

In each of the first to fifth embodiments, a three-frequency monopole antenna has been described as an example, but the present invention is not necessarily limited to a monopole antenna having this configuration. Not something. For example, by using a single annular conductor, a two-frequency operating monopole
An antenna can be realized, and a multipole operating monopole antenna having four or more frequencies can be realized by using three or more ring-shaped conductors.

In each of the first to fifth embodiments, the monopole antenna provided with the disc-shaped ground conductor 11 has been described as an example. However, the present invention is not limited to the monopole antenna having this configuration.・ It is not limited to antennas. As the ground conductor, any shape such as an ellipse or a polygon such as a triangle may be used.

In each of the first to fifth embodiments, the disc-shaped conductor 22 is used as the flat conductor, and the ring-shaped conductor 2 is disposed concentrically with the disc-shaped conductor 22 as the ring-shaped conductor.
Although a monopole antenna using the antennas 4 and 26 has been described as an example, the present invention is not necessarily limited to the monopole antenna having this configuration. As the plate-shaped conductor or the ring-shaped conductor, any shape such as an ellipse or a polygon such as a triangle may be used.

In each of the first to fifth embodiments, a monopole antenna having an axisymmetric structure has been described as an example. However, the present invention is not necessarily limited to a monopole antenna having this configuration. It is not something to be done. For example,
The power supply unit 12 may be configured to be located at a point other than the center of the ground conductor 11. By employing this configuration, it is possible to cause a bias in the radiated radio waves of the antenna, and it is possible to realize a monopole antenna having strong directivity in one direction on a horizontal plane.

Further, in each of the first to fifth embodiments, the monopole antenna in which the disc conductor 22 is vertically connected to the linear conductor 21 has been described as an example. However, the present invention is not necessarily limited to this. The present invention is not limited to the monopole antenna having this configuration. For example, when the disc conductor 22 is the linear conductor 2
1 may be connected diagonally. By adopting this configuration, it is possible to change the magnitude of the input impedance and improve the matching state with the power supply unit 12.

In each of the first to fifth embodiments, the monopole antenna in which the disk conductor 22 and the ring-shaped conductors 24 and 26 are arranged on the same plane has been described as an example. The present invention is not necessarily limited to the monopole antenna having this configuration. For example, disc conductor 2
It is also possible to adopt a configuration in which 2 and the annular conductors 24 and 26 are arranged on a different plane, or a configuration in which at least one of the plurality of annular conductors 24 and 26 is arranged on a different plane from the disc conductor 22. . As a specific example, FIG.
(a) and (b) show the disk conductor 22, the annular conductor 24 and the annular conductor 2 respectively.
6 are all arranged on different planes. FIG. 12A shows that the ring-shaped conductors 24 and 26 are the disc conductors 2.
FIG. 12B shows a case where the ring-shaped conductors 24 and 26 are arranged on a plane higher than the disk conductor 22. When a support for supporting the ring-shaped conductors 24 and 26 is required, for example, a support rod made of a dielectric material such as an insulator, Teflon, or glass epoxy can be used.

In each of the first to fifth embodiments, the power supply unit 1 having one end located on the surface of the ground conductor 11 is provided.
2, a disc conductor 22 connected to the other end of the straight conductor 21, and an inner edge portion of the disc conductor 22.
An antenna element comprising a ring-shaped conductor 24 connected to the outer edge of the ring-shaped conductor via an anti-resonance circuit 23 and a ring-shaped conductor 26 having an inner edge connected to the outer edge of the ring-shaped conductor 24 via an anti-resonance circuit 25. Although the description has been given by taking the monopole antenna as an example, the present invention is not necessarily limited to the monopole antenna having this configuration. For example, as shown in FIG. 13, a linear conductor 21 having one end connected to a feeder located on the surface of a ground conductor, and a ring-shaped inner edge connected to the other end of the linear conductor 21 via an anti-resonance circuit 23. Conductor 24
The inner edge of the anti-resonant circuit 2
It is also possible to adopt a configuration provided with an antenna unit composed of a ring-shaped conductor 26 connected through the wire 5. In this case, by setting the resonance frequency of the anti-resonance circuit 23 to f1 and the resonance frequency of the anti-resonance circuit 25 to f2 (f1> f2), the frequency f1 is excited only by the straight conductor 21 and The frequency f2 can be excited in the system from the loop conductor 24 to the frequency f3 in the system from the straight conductor 21 to the loop conductor 26.

<Sixth Embodiment> Next, the sixth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

FIG. 14 is a schematic perspective view showing a monopole antenna according to the sixth embodiment of the present invention. FIG.
In 4, reference numeral 11 denotes a disc-shaped ground conductor having a finite size, 12 denotes a feeder located at the center of the ground conductor 11,
Numeral 6 denotes an antenna element made of a straight conductor, and numeral 14 denotes a disc-shaped reflective conductor. The power supply unit 12 is a ground conductor 1
1, the antenna element 16 is electrically connected to the feeder 12 perpendicularly to the ground conductor 11.
The reflective conductor 14 is parallel to the ground conductor 11 on the side opposite to the side on which the antenna element 16 is arranged, so as to cause electrical coupling via a space between the reflective conductor 14 and the ground conductor 11. And they are arranged concentrically. The ground conductor 11 and the reflective conductor 14 are connected by a support rod 15 made of, for example, an insulator or a dielectric such as Teflon or glass epoxy.

As described above, the present monopole antenna 1
Has an axially symmetric structure. For this reason, it is possible to make the antenna omnidirectional in the lateral direction of the antenna.

The operation of the monopole antenna having the above configuration will be described below.

Excitation of radio waves is performed by the antenna element 16. That is, a standing wave of the current having the resonance frequency f0 is generated in the antenna element 16, and the radio wave having the frequency f0 is radiated. At this time, a current having a reverse phase flows through the ground conductor 11, and a radio wave is also emitted from the end of the ground conductor 11. Since the monopole antenna 1 has the ground conductor 11 having a finite size, its radio wave radiation is radiated from the antenna element 16 serving as a radio wave radiation source and from the end of the ground conductor 11. With the radiation of further,
The monopole antenna 1 is opposed to the ground conductor 11 on the side opposite to the side on which the antenna element 16 is arranged, so as to cause electrical coupling via a space between the monopole antenna 1 and the ground conductor 11. Since the reflective conductors 14 are disposed in a vertical direction, a current also flows through the reflective conductors 14 by electrical coupling through a space, and a radio wave is also emitted from the end of the reflective conductors 14. Therefore, the radiation of the radio wave by the monopole antenna 1 is the sum of the radiation from the antenna element 16, the radiation from the end of the ground conductor 11, and the radiation from the end of the reflective conductor 14. For this reason, the ground conductor 11 and the reflection conductor 1
4 or the distance between the ground conductor 11 and the reflective conductor 14 is changed, so that the monopole antenna 1
Can be changed.

FIG. 15 shows the antenna characteristics of the monopole antenna 1 according to the present embodiment which was actually manufactured.
The prototype monopole antennas 1 ₁ , 1 ₂ , and 1 ′ each have an axially symmetric structure having a quarter-wavelength linear conductor as the antenna element 13, and are shown in FIGS.
Is the monopole of the present embodiment having the reflective conductor 14.
And shows the antenna 1 _1, 1 ₂ of the radiation directivity, and FIG. 15 (c) shows the radiation directivity of a conventional monopole antenna 1 'with no reflection conductor. More specifically, FIG. 15A shows a disc-shaped ground conductor 11 having a diameter of one wavelength of the resonance frequency of the antenna element 16 and a disc-shaped ground conductor 11 having a diameter of two wavelengths of the resonance frequency of the antenna element 16. A reflective conductor, and the distance between the ground conductor 11 and the reflective conductor is set to be one of the resonance frequencies of the antenna element 16.
Monopole antenna 1 of the present embodiment having 波長 wavelength
₁ shows the radiation directivity. FIG. 15 (b)
A disc-shaped ground conductor 11 having a diameter of 1.25 wavelength of the resonance frequency of the antenna element 16 and a disc-shaped reflection conductor 14 having a diameter of 2 wavelengths of the resonance frequency of the antenna element 13
With the door shows a radiation directivity distance of this embodiment having a quarter wavelength of the resonant frequency of the antenna element 16 of the monopole antenna 1 ₂ between the ground conductor 11 and the reflection conductor 14. FIG. 15C shows a disc-shaped ground conductor 1 having a diameter of two wavelengths at the resonance frequency of the antenna element 16.
1 shows the radiation directivity of a conventional monopole antenna 1 ′ provided with an antenna 1 ′. As shown in FIG. 15D, the x and y directions in the figure indicate directions parallel to the plane of the ground conductor 11 and the reflective conductor 14, and the z direction indicates a perpendicular direction of the ground conductor 11 and the reflective conductor 14. Is shown. The scale of the radiation directivity is such that one interval is 10 dB, and the unit is dBd based on the gain of the dipole antenna.

As shown in FIG.
Antenna 1 _1, the antenna top (the side where the antenna element 16 is provided), in particular shows a very strong radiation directivity in that directly above the antenna under side (reflection conductor 14 is provided), The radiation directivity is extremely weak. That is, the monopole antenna 1 _1, for example, when transmitting and receiving waves of radio waves to and from the balloon or the like and the ground floating space, or air with a spread in the height direction of the blow, such as hall and buildings It becomes suitable for. In particular, since it is possible to make the antenna omnidirectional in the lateral direction,
Excellent radiation from the sky.

As shown in FIG.
Antenna 1 ₂ shows a very strong radiation directivity antenna top (the side where the antenna element 16 is provided), the antenna lower (reflection conductor 14 is provided side), is extremely radiation directivity It is getting weaker. Further, also on the upper side of the antenna, the radiation directivity in the oblique horizontal direction is strong. In other words, the monopole antenna 1 ₂ is,
This is suitable for an indoor space having a normal lateral spread. In particular, since radiation can be omni-directional in the lateral direction of the antenna, installation in the center of the indoor ceiling provides excellent radiation to a very large space.

[0092] As shown in FIG. 15 (c), the conventional monopole antenna 1 'is compared to the monopole antenna 1 _1, 1 ₂ of the present embodiment, the antenna lower (reflecting conductor is provided The radiation directivity of the other side is also relatively high. That is, this monopole antenna 1 'has a relatively large leak of radio waves to the lower side of the antenna, and is not suitable for installation on a ceiling in a room.

[0093] As apparent from the above, the monopole antenna 1 _1, 1 ₂ provided with the reflection conductor 14, is reflected radio wave is radiated to the antenna lower side by the reflection conductor 14, the antenna upper Radiation is increasing.

When the monopole antenna 1 according to the present embodiment is mounted on a ceiling in a room, as shown in FIG.
The ground conductor 11 may be placed in contact with the surface of the ceiling 80 in a state where it is housed in the ceiling 80.
, Only the antenna element 16 protrudes toward the floor, and if the antenna element 16 made of a straight conductor is used, the antenna element 16 is less noticeable, so that it does not obstruct the view.

Further, the antenna element 1 made of a linear conductor
Instead of 6, it is also possible to use an antenna element configured by connecting the center of a disk conductor vertically to the upper end of a straight conductor, and to connect the lower end of the straight conductor to a feed unit 12 located at the center of the ground conductor 11. is there. If such a configuration is adopted, the height of the antenna element can be reduced similarly to the inverted L antenna while maintaining the axially symmetric structure, which is more preferable in view.

As described above, according to the present embodiment, the radiation directivity of monopole antenna 1 can be changed by providing reflecting conductor 14. Further, the ground conductor 1
1 or the size of the reflective conductor 14 or the distance between the ground conductor 11 and the reflective conductor 14 is arbitrarily set.
Desired radiation directivity can be realized. Therefore, according to the present embodiment, a monopole antenna 1 having a desired radiation directivity can be realized with a simple structure. An excellent monopole antenna 1 having excellent radiation directivity can be realized.

When the configuration of the present embodiment is adopted, the input impedance can be stabilized by setting the diameter of the ground conductor 11 to a half wavelength or more of the resonance frequency of the antenna element 16. it can. Hereinafter, this will be described.

Generally, in a monopole antenna 1 having a disc-shaped ground conductor 11, if the diameter of the ground conductor 11 is smaller than 波長 of the wavelength of the resonance frequency of the antenna element 16, the antenna input section There is a characteristic that a current leaks outside the coaxial outer conductor and the input impedance becomes unstable. Therefore, in the present embodiment, the diameter of the ground conductor 11 is set to one of the resonance frequencies of the antenna element 16.
By setting the wavelength to ２ wavelength or more, current leakage to the outside of the coaxial outer conductor of the antenna input portion is prevented, the input impedance is stabilized, and the transmission operation is stabilized.

<Seventh Embodiment> Next, a seventh embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

FIG. 17 is a schematic perspective view showing a monopole antenna according to the seventh embodiment of the present invention. FIG.
In 7, 11 denotes a ground conductor, 12 denotes a feeder, 16 denotes an antenna element, 14 denotes a reflection conductor, and 27 denotes a connection conductor. Since the configuration other than the connection conductor 27 is the same as that of the sixth embodiment, members other than the connection conductor 27 are denoted by the same reference numerals as in the sixth embodiment, and detailed description thereof is omitted. . The monopole of the present embodiment
The antenna 20 is characterized in that the ground conductor 11 and the reflection conductor 14 are electrically connected by the connection conductor 27. Although various connection structures between the ground conductor 11 and the reflective conductor 14 are conceivable, in the present embodiment, a perpendicular line between the ground conductor 11 and the reflective conductor 14 is located at the center of the disc-shaped ground conductor 11 and the reflective conductor 14. By disposing the columnar connection conductor 27 along the direction, the conductors 11 and 14 are electrically connected and mechanically connected. Further, the diameter of the reflective conductor 14 is
6 is set to 以上 or more of the wavelength of the resonance frequency.

The operation of the monopole antenna having the above configuration will be described below.

The operation of the monopole antenna 20 is the same as the operation of the monopole antenna 1 of the sixth embodiment, but the monopole antenna 20 has the following operations in addition to the above operation. The following operation is also performed. That is, when the monopole antenna 20 is installed on the ceiling in the room, as described with reference to FIG. 16, the reflective conductor 14 can be housed inside the ceiling 80 (behind the ceiling). It is inevitable that the conductor 11 is exposed from the ceiling 80 to the indoor side. Therefore, if there is a demand to make the ground conductor 11 noticeable as small as possible, it is considered that the diameter of the disc-shaped ground conductor 11 becomes equal to or less than １ ／ wavelength of the resonance frequency of the antenna element 16. Can be However, with such a configuration, it is inevitable that a current leaks outside the coaxial outer conductor of the antenna input portion and the input impedance becomes unstable.

On the other hand, in the present embodiment,
The following configuration is employed.

First, the reflection conductor 14 is electrically connected to the ground conductor 11. For this reason, the reflective conductor 14 has the same function as the ground conductor 11 in addition to the function as the reflective conductor (the function of controlling the radio wave radiation direction). Thus, the reflective conductor 14 functions to suppress the leakage of the current and stabilize the input impedance while performing the original function of the reflective conductor. Therefore, the diameter of the ground conductor 11 is set to １ ／ of the resonance frequency of the antenna element 16.
Even if the wavelength is as small as the wavelength or less, it is possible to prevent the disadvantage that the leakage current occurs and the input impedance becomes unstable.

Second, the diameter of the reflecting conductor 14 is set to be at least half the wavelength of the resonance frequency of the antenna element 16. As a result, the leakage of current can be suppressed more reliably,
It is possible to further stabilize the input impedance.

For the reasons described above, even if the diameter of the ground conductor 11 is set to a value that is less than 波長 wavelength of the resonance frequency of the antenna element 13 and has a high possibility of occurrence of leakage current, The current can be reliably suppressed. Therefore, by employing the configuration of the present embodiment, it is possible to achieve both miniaturization of the ground conductor 11 and stabilization of the input impedance.

When the configuration of the present embodiment is adopted,
The reflection conductor 14 has 1 / (resonance frequency)
Although it is relatively large, that is, two or more wavelengths,
When the present monopole antenna 20 is mounted on the ceiling in a room, the reflective conductor 14 is housed inside the ceiling (behind the ceiling). The size of the antenna portion does not increase.

As described above, the monopole of the present embodiment
The antenna 20 has a feature that both the stabilization of the input impedance and the miniaturization can be achieved. Further, the antenna 20 further connects the ground conductor 11 and the reflection conductor 14 to the connection conductor 27.
By mechanically connecting the antennas, the antenna also has a feature that the structural stability of the antenna can be increased.

As described above, according to the present embodiment, it is possible to realize a monopole antenna capable of changing the radiation directivity with a very simple structure, and to improve the operation and structure of the antenna. In addition, an excellent monopole antenna having a more stable structure can be realized.

In this embodiment, a monopole circuit having a single ground conductor 11 and a single reflective conductor 14 is used.
Although the antenna 20 has been described as an example, the present invention is not necessarily limited to the monopole antenna having this configuration. A plurality of reflective conductors may be provided, and all of the plurality of reflective conductors may be electrically connected to the ground conductor 11 by the connection conductor. In addition, it has a plurality of reflective conductors,
At least one of the plurality of reflection conductors may be selectively connected to the ground conductor 11 by a connection conductor.

In the sixth or seventh embodiment, a monopole antenna having a single reflective conductor 14 and having an axially symmetric structure has been described as an example. The configuration is not necessarily limited to the monopole antenna having this configuration. A monopole having a desired radiation directivity by arbitrarily setting the shape and size of the ground conductor 11, the number and shape and size of each of the reflective conductors, and the positions of the ground conductor 11 and the reflective conductor・ An antenna can be realized.

In the sixth or seventh embodiment, the monopole antenna including the antenna element 16 made of a linear conductor has been described as an example. However, the present invention is not limited to the monopole antenna having this configuration.・ It is not limited to antennas. For example, an antenna element may be configured by connecting the center of a disc conductor to the upper end of a straight conductor, and the sum of the length of these straight conductors and the radius of the disc conductor may be set to be equal to the length of the antenna element 16. This makes it possible to further reduce the height of the monopole antenna. Further, as the antenna element, the antenna element 13 (the linear conductor 21, the disc conductor 2) of the first to fifth embodiments is used.
2, an antenna element composed of the ring-shaped conductors 24 and 26 and the anti-resonance circuits 23 and 25 or an antenna element composed of a linear conductor, a ring-shaped conductor and an anti-resonance circuit).
It is possible to realize a monopole antenna having more excellent characteristics in combination with the effect of the embodiment.

<Eighth Embodiment> Next, an eighth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

FIG. 18 is a schematic perspective view showing a monopole antenna according to the eighth embodiment of the present invention. FIG.
In 8, reference numeral 11 denotes a ground conductor, 12 denotes a feeding unit, 31 denotes an antenna element, and 14A and 14B denote reflection conductors. Reflective conductors 14A and 14B and antenna element 31
The other configuration is the same as that of the sixth embodiment,
Members other than the reflective conductors 14A and 14B and the antenna element 31 are denoted by the same reference numerals as in the sixth embodiment, and detailed description thereof will be omitted. The monopole antenna 30 according to the present embodiment includes an antenna element 31 that is excited at a plurality of resonance frequencies (operates at a plurality of frequencies). The antenna element 31 is electrically connected to the feeder 12 located at the center of the ground conductor 11 perpendicular to the ground conductor 11. The reflection conductors 14A and 14B are formed in a disk shape,
They are arranged in parallel with each other and also in parallel with the ground conductor 11. Further, the reflection conductors 14A and 14B are arranged coaxially with the ground conductor 11. The ground conductor 11
And reflective conductor 14A, and reflective conductor 14A and reflective conductor 14
B are connected by a support rod 15 made of, for example, an insulator or a dielectric such as Teflon or glass epoxy.

Further, in the monopole antenna 30 of the present embodiment, the antenna element 31 is excited at two resonance frequencies, and two reflecting conductors (reflecting conductors 14A and 14B) are used accordingly. ) Equipped axisymmetric structure.

The operation of the monopole antenna having the above configuration will be described below.

The operation of the monopole antenna 30 is as follows.
Basically, the operation is the same as that of the monopole antenna 1 of the sixth embodiment, but in this monopole antenna 30, the antenna element 31 excites radio waves of two resonance frequencies f0 and f1. I do. In this case, the size of the ground conductor 11 and the reflection conductors 14A and 14B with respect to the wavelength differs depending on the resonance frequency, and the radiation directivity also differs. Therefore, the shape and size of the ground conductor 11 and the reflection conductors 14A and 14B corresponding to the respective resonance frequencies f0 and f1,
The desired radiation directivity can be realized at each of the resonance frequencies f0 and f1 by arbitrarily setting the distance between the reflection conductors 14A and 14B.

Further, in this monopole antenna 30, as in the sixth embodiment, the ground conductor 11
Is smaller than the lower resonance frequency of the antenna element 31 by one.
By setting the wavelength to be equal to or longer than / 2 wavelength, the input impedance can be stabilized.

<Ninth Embodiment> Next, a ninth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

FIG. 19 is a schematic perspective view showing a monopole antenna according to the ninth embodiment of the present invention. FIG.
In 9, 11 is a ground conductor, 12 is a feeder, 31 is an antenna element, 14A and 14B are reflection conductors, 41A and 41
B indicates connection conductors. Connection conductor 41A,
Since the configuration other than 41B is the same as that of the above-described eighth embodiment, members other than the connection conductors 41A and 41B are denoted by the same reference numerals as those of the above-described eighth embodiment, and detailed description thereof is omitted. . Monopole antenna 4 of the present embodiment
0 indicates that the ground conductor 11 and the reflection conductor 14A
A, and is characterized in that the reflection conductor 14A and the reflection conductor 14B are electrically connected by the connection conductor 41B. Various connection structures between the ground conductor 11 and the reflection conductor 14A and a connection structure between the reflection conductor 14A and the reflection conductor 14B are conceivable. In the present embodiment, both the disc-shaped ground conductor 11 and the reflection conductor 14A are connected. By arranging the columnar connection conductor 41A at the center position along the perpendicular direction of the ground conductor 11 and the reflection conductor 14A, the conductors 11 and 14A are electrically connected and mechanically connected. Have been. Similarly, by disposing a columnar connection conductor 41B along the direction perpendicular to the reflection conductors 14A and 14B at the center of the disc-shaped reflection conductors 14A and 14B, the conductors 14A and 14B are electrically connected. In addition to being mechanically connected, they are also mechanically connected. Further, the larger one of the plurality of reflective conductors 41A, 41B (in FIG. 19, the reflective conductor 14A on the ground conductor 11 side).
The diameter of A) is set to be equal to or more than 波長 wavelength of the lower resonance frequency of the antenna element 31.

Hereinafter, the operation of the monopole antenna having the above configuration will be described.

The operation of the monopole antenna 40 is as follows.
Basically, the operation is the same as that of the monopole antenna 1 of the sixth embodiment. However, in the monopole antenna 40, the antenna element 41 excites the radio waves of the two resonance frequencies f0 and f1. I do. In this case, the size of the ground conductor 11 and the reflection conductors 14A and 14B with respect to the wavelength differs depending on the resonance frequency, and the radiation directivity also differs. Therefore, the shape and size of the ground conductor 11 and the reflection conductors 14A and 14B corresponding to the respective resonance frequencies f0 and f1,
The desired radiation directivity can be realized at each of the resonance frequencies f0 and f1 by arbitrarily setting the distance between the reflection conductors 14A and 14B.

In the monopole antenna 40, the reflecting conductors 14A and 14B are connected to the connecting conductors 41A and 41A.
1B, is electrically connected to the ground conductor 11, and the diameter of the larger one of the plurality of reflective conductors 41A and 41B (the reflective conductor 14A on the ground conductor 11 side in FIG. 19). Are set to 波長 wavelength or more of the lower resonance frequency of the antenna element 31. For this reason, even if the diameter of the ground conductor 11 is set to a value that is less than 波長 wavelength of the lower resonance frequency of the antenna element 31 and has a high possibility of occurrence of leakage current, the expected leakage current can be surely obtained. Can be suppressed. Therefore, by employing the configuration of the present embodiment, it is possible to achieve both miniaturization of the ground conductor 11 and stabilization of the input impedance. The reason for obtaining such an effect is the same as that described in the seventh embodiment, and a detailed description thereof will be omitted here.

In this embodiment, the ground conductor 11 and the reflection conductor 14A are mechanically connected by the connection conductor 41A, and the reflection conductor 14A and the reflection conductor 14B
Are mechanically connected by the connection conductor 41B, so that the structural stability of the antenna can be increased.

As described above, according to the present embodiment, it is possible to realize a monopole antenna capable of changing the radiation directivity with a simple structure. An excellent monopole antenna having a more stable structure can be realized.

In the present embodiment, the monopole antenna 40 having the two reflection conductors 14A and 14B and the two connection conductors 41A and 41B has been described as an example. However, the present invention is not necessarily limited to this. The configuration is not limited to the monopole antenna. Three or more reflective conductors may be provided, and all of these reflective conductors may be electrically connected to the ground conductor 11 by connection conductors. Also, 3
One or more reflective conductors, at least one of which is selectively connected to a ground conductor 11 by a connecting conductor.
May be connected electrically.

In the eighth or ninth embodiment, the antenna element 31 has two resonance frequencies f0 and f0.
1, the description has been given by taking as an example an axially symmetric monopole antenna provided with two reflecting conductors (reflecting conductors 14A and 14B). It is not limited to the monopole antenna having the configuration, and may be configured using a single reflective conductor. Even in this case, desired radiation directivity can be realized by arbitrarily setting the shape and size of each of the ground conductor 11 and the reflective conductor and the distance between the ground conductor 11 and the reflective conductor. it can. Further, the radiation directivity for each resonance frequency may be changed by a combination of a plurality of reflective conductors. For example, a desired radiation directivity can be realized by appropriately setting the number of reflection conductors and their shapes, sizes, and positions at each resonance frequency.

In the eighth or ninth embodiment, the antenna element according to the first to fifth embodiments is replaced with the antenna element 31 excited at a plurality of resonance frequencies (operating at a plurality of frequencies). If the element 13 (an antenna element composed of the linear conductor 21, the disk conductor 22, the ring conductors 24 and 26, and the antiresonance circuits 23 and 25 or an antenna element composed of a linear conductor, a ring conductor, and an antiresonance circuit) is used,
It is possible to realize a monopole antenna having more excellent characteristics in combination with the effects of the fifth embodiment.

[0129]

As described above, according to the present invention,
A small monopole antenna capable of operating at multiple frequencies with a simple structure can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a monopole antenna according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing an antenna element according to the first and second embodiments of the present invention.

FIG. 3 is a diagram illustrating an example of an anti-resonance circuit of the antenna element according to the first and third embodiments of the present invention.

FIG. 4 is a diagram showing an example of an anti-resonance circuit of an antenna element according to the second and fourth embodiments of the present invention.

FIG. 5A is a schematic perspective view showing an example of a top-loading type monopole antenna according to the first embodiment of the present invention, and FIG. 5B is a schematic perspective view showing the antenna element.

FIG. 6 is a diagram for explaining a reduction in height of the top-loading type monopole antenna according to the first embodiment of the present invention;

FIG. 7 is a diagram showing the relationship between the diameter of the disc conductor and the height of the antenna element when the resonance frequency of the top-loading monopole antenna according to the first embodiment of the present invention is constant.

FIG. 8 is a diagram illustrating an example of characteristics of the monopole antenna according to the first embodiment of the present invention.

FIG. 9 is a schematic perspective view showing an antenna element according to the third and fourth embodiments of the present invention.

FIG. 10 is a schematic perspective view showing an antenna element according to a fifth embodiment of the present invention.

FIG. 11 is a diagram illustrating an example of an anti-resonance circuit of an antenna element according to a fifth embodiment of the present invention.

FIG. 12 is a schematic perspective view showing an antenna element in which a disk conductor and a ring-shaped conductor are arranged on different planes.

FIG. 13 is a schematic perspective view showing an antenna element composed of a straight conductor and a ring-shaped conductor.

FIG. 14 is a schematic perspective view showing a monopole antenna according to a sixth embodiment of the present invention.

FIG. 15 is a diagram showing an example of characteristics of the monopole antenna according to the sixth embodiment of the present invention and a conventional monopole antenna.

FIG. 16 is a diagram showing an arrangement example of a monopole antenna according to a sixth embodiment of the present invention.

FIG. 17 is a schematic perspective view showing a monopole antenna according to a seventh embodiment of the present invention.

FIG. 18 is a schematic perspective view showing a monopole antenna according to an eighth embodiment of the present invention.

FIG. 19 is a schematic perspective view showing a monopole antenna according to a ninth embodiment of the present invention.

FIG. 20 is a schematic perspective view showing a monopole antenna according to the prior art.

[Explanation of symbols]

 1, 20, 30, 40 Monopole antenna 11 Ground conductor 12 Coaxial feeder 13, 16 Antenna element 14, 14A, 14B Reflector conductor 15 Support rod 21 Straight conductor 22 Disk conductor 23, 25 Anti-resonant circuit 24, 26 Ring conductor 27, 41A, 41B Connection conductor 31, 41 Coil 32 Capacitor 51 Equivalent capacitor 52, 53 Transmission line 61, 62, 63 Ground conductor wire 71 Dielectric substrate 81 Metal pattern 82 Coil pattern 83 Capacitor pattern

Claims (31)

[Claims] 1. A ground conductor, a linear conductor having one end connected to a feeder located on the surface of the ground conductor, a flat conductor connected to the other end of the straight conductor, and an inner edge portion of the flat conductor connected to the flat plate. A monopole antenna comprising a ring-shaped conductor connected to an outer edge of the ring-shaped conductor via an anti-resonance circuit. 2. The monopole antenna according to claim 1, wherein at least one of the flat conductor and the annular conductor is connected to the ground conductor by a ground conductor wire. 3. The monopole antenna according to claim 1, wherein the plate-shaped conductor and the ring-shaped conductor are arranged on the same plane. 4. The monopole antenna according to claim 1, wherein the plate-shaped conductor and the ring-shaped conductor are arranged on different planes. 5. The monopole antenna according to claim 1, wherein the ring-shaped conductor comprises a plurality of ring-shaped conductors, and opposing inner and outer edges of adjacent ring-shaped conductors are connected via an anti-resonance circuit. 6. The monopole antenna according to claim 5, wherein at least one of the flat conductor and the plurality of annular conductors is connected to the ground conductor by a ground conductor wire. 7. The monopole antenna according to claim 5, wherein the flat conductor and the plurality of ring conductors are arranged on the same plane. 8. The monopole antenna according to claim 5, wherein at least one of the plurality of annular conductors is arranged on a plane different from the flat conductor. 9. The monopole antenna according to claim 1, wherein the flat conductor is a disc conductor. 10. A power supply unit is located at the center of the surface of the ground conductor, one end of the linear conductor is connected to the power supply unit perpendicular to the ground conductor, and the other end of the linear conductor is perpendicular to the flat conductor. The monopole antenna according to claim 9, wherein the monopole antenna is connected at the center of the plate-shaped conductor, and the ring-shaped conductor is arranged concentrically with the plate-shaped conductor. 11. The monopole antenna according to claim 1, wherein the anti-resonance circuit is a parallel circuit of a coil and a capacitor. 12. The monopole antenna according to claim 1, wherein the anti-resonance circuit is a circuit including only a coil. 13. The monopole antenna according to claim 1, wherein the plate-shaped conductor, the anti-resonance circuit, and the ring-shaped conductor are patterned on a dielectric substrate. 14. The grounding conductor according to claim 1, wherein a reflection conductor is provided on a side of the grounding conductor opposite to the side on which the plate-shaped conductor is arranged, for providing an electrical connection via a space with the grounding conductor. Monopole antenna. 15. The monopole antenna according to claim 14, wherein the reflection conductor is electrically connected to the ground conductor. 16. The reflection conductor comprises a plurality of reflection conductors,
The monopole antenna according to claim 14, wherein at least one of the plurality of reflective conductors is electrically connected to a ground conductor. 17. The ground conductor and the reflective conductor have a planar shape, are arranged with their surfaces facing each other, and the area of the reflective conductor is larger than the area of the ground conductor. Monopole antenna. 18. A ring-shaped conductor having one end connected to a feeder located at the surface of the ground conductor, and one end connected to the other end of the straight conductor via an anti-resonance circuit. Monopole antenna with conductor. 19. The monopole antenna according to claim 18, wherein the ring-shaped conductor is connected to the ground conductor by a ground conductor wire. 20. A ring-shaped conductor comprising a plurality of ring-shaped conductors,
19. The monopole antenna according to claim 18, wherein opposing inner edges and outer edges of adjacent ring-shaped conductors are connected via an anti-resonance circuit. 21. The monopole antenna according to claim 20, wherein at least one of the plurality of annular conductors is connected to the ground conductor by a ground conductor wire. 22. The monopole antenna according to claim 20, wherein a plurality of ring-shaped conductors are arranged on the same plane. 23. The monopole antenna according to claim 20, wherein at least one of the plurality of annular conductors is arranged on different planes. 24. The power supply unit is located at the center of the surface of the ground conductor, and the plurality of ring-shaped conductors are arranged concentrically.
The monopole antenna according to 1. 25. The monopole antenna according to claim 18, wherein the anti-resonance circuit is a parallel circuit of a coil and a capacitor. 26. The monopole antenna according to claim 18, wherein the anti-resonance circuit is a circuit including only a coil. 27. The monopole antenna according to claim 18, wherein the anti-resonance circuit and the ring-shaped conductor are patterned on a dielectric substrate. 28. The object according to claim 18, wherein a reflection conductor for providing an electrical connection through a space between the ground conductor and the ground conductor is provided on a side of the ground conductor opposite to the side on which the ring-shaped conductor is arranged. Paul antenna. 29. The monopole antenna according to claim 28, wherein the reflection conductor is electrically connected to the ground conductor. 30. A reflective conductor comprising a plurality of reflective conductors,
29. The monopole antenna according to claim 28, wherein at least one of the plurality of reflective conductors is electrically connected to a ground conductor. 31. The ground conductor and the reflective conductor have a planar shape, are arranged with their surfaces facing each other, and the area of the reflective conductor is larger than the area of the ground conductor. Monopole antenna.