JPH08307142A - Dual directivity antenna and method for extending frequency band width of the antenna - Google Patents

Abstract

PURPOSE: To realize dual directivity in a horizontal plane at a wide frequency band by providing a parasitic element absorbing or reflecting a high frequency current in parallel with a radiation element for a high frequency current so as to make the outer size thin. CONSTITUTION: A reflecting element 26 made of a circular-arc conductor is arranged to a dipole antenna 21 at an interval D. An angle α of the circular-arc is represented by an angle when viewing a midpoint O of a line segment tying the dipole antenna 21 and the reflection element 26. Then an electromagnetic field emitted from the dipole antenna 21 in a direction of the point O is absorbed or reflected by the reflecting element 26. The electromagnetic field reflected by the reflecting element 26 is emitted in a direction of a point O'. Thus, a direct electromagnetic field and a reflected electromagnetic field are emitted in a direction of the point O' from the dipole antenna 21. The phase of the direct electromagnetic field and that of the reflected electromagnetic field differ based on the difference in propagation distance. Thus, the electromagnetic field emitted from the dipole antenna 21 in the direction of the point O' is weakened. Thus, the dual directivity having a strong directivity in directions of points P, P' is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical antenna used for mobile communication and the like, and more particularly to a bidirectional antenna suitable for use as an antenna of a base station and a method for expanding the frequency bandwidth of the antenna.

[0002]

2. Description of the Related Art In recent years, mobile communication has become remarkably widespread, and its applications and communication methods have come to be diversified. For example, a mobile phone called a car phone or a mobile phone is one of them, and it is needless to say that the degree of popularization of the mobile phone. Now, as an example, in the small zone system (cellular system) used in the field of mobile phones, wireless communication is performed between a mobile station having a telephone terminal and a wireless base station (fixed station) installed in each fixed area. Communicate. In this method, in order to avoid interference, the same frequency is not assigned to adjacent areas, and the frequencies are reused in an area with a certain distance.

However, in most of the conventional methods as described above, the reuse rate of radio waves is limited in order to avoid interference, and the frequency band assigned to mobile phones is currently extremely congested. Therefore, in place of the conventional small zone, a micro cell communication system having a narrower communication area has been put into practical use.

In the above-mentioned microcell communication system, the antenna of the radio base station is generally arranged at a position where the ground height is lower than the surrounding buildings. Therefore, the cell (area) is extremely narrow,
It also has a complicated shape. FIG. 8 is a plan view showing an example of the cell shape of the microcell communication system. In FIG.
1 is an antenna of a radio base station, 2 is a cell, 3 is a road, 4,
Reference numeral 4 indicates a building, and reference numerals 4a, 4a ... indicate wall surfaces of the building. As shown in this figure, in the microcell communication system, the shape of the cell 2 is limited to the buildings 4 and 4, and also the shape along the road 3.

In such a case, the gain of the antenna 1 is increased by making the horizontal directivity of the antenna 1 used for the radio base station not bidirectional, but bidirectional along the traffic direction of the road 3. be able to. That is, it is possible to raise the transmission / reception level with respect to the mobile station moving on the road 3.

By the way, since many antennas for radio base stations are installed in urban areas, it is preferable that their shapes are inconspicuous. For this reason, generally, a rod-shaped vertical antenna is often used. As an example of an antenna that achieves horizontal bidirectionality with this rod-shaped vertical antenna, there is a collinear antenna with a reflector in which a reflector in parallel with the collinear antenna is arranged.

FIG. 9 is a perspective view showing an external configuration of a conventional collinear antenna with a reflector. In FIG. 9, the radiators 11, 11, ... Are arranged in series in the radome 17,
Spacers 15, 15 are arranged in the longitudinal direction of the radiators 11, 11.
The linear reflectors 16 and 16 are attached via. Further, 12 is an inner conductor of the power supply line, 13 is an outer conductor of the power supply line, and these penetrate the radiators 11, 11 ,. In this collinear antenna with reflector 18, the distance from the center of the radiator 11 to the center of the reflector 16 is D.

[0008]

FIG. 10 is a diagram showing a horizontal plane directional characteristic of a conventional vertical collinear antenna.
As shown in FIG. 10A, the directivity of a collinear antenna is generally omnidirectional about the axis O of the antenna.
On the other hand, the collinear antenna 18 with reflector is
By appropriately selecting the length of 6, horizontal bidirectionality can be realized as shown in FIG. This FIG. 10 (b)
In this case, the reflector 16 is attached from the axis O of the radiator 11 in the x direction shown in the drawing. But in this case,
The frequency bandwidth of the collinear antenna with reflector 18 depends on the distance D from the axis O of the radiator 11 to the center of the reflector 16.

FIG. 11 shows that the length of each radiator 11 is λ / 4.
FIG. 3 is a diagram showing a ratio of a distance D to a wavelength λ and a frequency bandwidth capable of maintaining bidirectional characteristics with respect to the wavelength λ when (λ is one wavelength). In FIG. 11, the solid line A is the calculated value, and the points B1 and B2 are the measured values. As can be seen from FIG. 11, when the reflector 16 is linear, the frequency bandwidth is 1% of the center frequency when the distance D is 0.11λ or less.
There is a drawback that the width becomes narrow as follows (when F / B is within ± 1 dB). However, it is desirable that the rod-shaped antenna such as the collinear antenna with a reflector 18 is thin in view of the scenery, and therefore the distance D is required to be as short as possible.
The present invention has been made in view of such a background, and provides a bidirectional antenna having a narrow external shape and capable of obtaining horizontal bidirectionality in a wide frequency band, and a method for expanding the frequency bandwidth of the antenna. It is intended to be provided.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is a bidirectional antenna having directivity in both directions, and radiates a high frequency current. It is characterized in that it is composed of a vertical radiating element and a parasitic element arranged in parallel with the radiating element, and the parasitic element is formed on an arcuate surface.

In the invention according to claim 2, in the bidirectional antenna according to claim 1, the radiating element is parallel to the antenna and the outer peripheral portion is formed in an arc shape to reduce loss. It has a spacer made of a dielectric or other insulating material, and the parasitic element is a metal paint applied to the outer peripheral portion of the spacer or a metal tape adhered to the outer peripheral portion of the spacer. .

Further, in the invention of claim 3, in the bidirectional antenna according to claim 1 or 2, the parasitic element is interlocked with a wire mesh or a metal tape or the like. It is characterized in that it is formed.

Further, in the invention described in claim 4, in the bidirectional antenna according to any one of claims 1 to 3, a dipole antenna is used as the radiating element. .

Further, in the invention described in claim 5, in the bidirectional antenna according to any one of claims 1 to 3, the radiating element is attached to the surface of the dielectric substrate. It is characterized by using a printed antenna formed of a metal film or the like.

According to a sixth aspect of the present invention, there is provided a method for expanding the frequency bandwidth of a bidirectional antenna having bidirectional directivity, comprising: a vertical radiating element for radiating a high frequency current; It is characterized in that the parasitic elements are arranged in parallel, and the parasitic elements are formed on an arcuate surface.

According to the invention described in claim 7, in the method for expanding the frequency bandwidth of a bidirectional antenna according to claim 6, the radiating element is parallel to the radiating element and has an arcuate outer peripheral portion. A spacer made of a dielectric material or other insulating material having a small loss formed is attached, and the parasitic element is constituted by a metal paint applied to the outer peripheral portion of the spacer or a metal tape attached to the outer peripheral portion of the spacer. It is characterized by doing.

Further, in the invention described in claim 8, in the method for expanding the frequency bandwidth of a bidirectional antenna according to claim 6 or 7, the parasitic element is
It is characterized in that it is formed into a blind shape by a wire net, a metal tape or the like.

[0018]

According to the present invention, a bidirectional antenna having a bidirectional directivity, which is provided with a parasitic element which is formed on an arcuate surface in parallel with a vertical radiating element which radiates a high frequency current and which is parallel to the radiating element. Expands the frequency bandwidth of the bidirectional antenna that exhibits bidirectional characteristics.

[0019]

【Example】

A. First Embodiment A bidirectional antenna according to the present invention will be described below. 1A and 1B are views for explaining the principle of the present invention. FIG. 1A is a perspective view and FIG. 1B is a top view. FIG.
In (a), 21 is a dipole antenna (half-wavelength dipole antenna), and 26 is a reflecting element formed of an arc-shaped conductor. In addition, the dipole antenna 21
The reflective element 26 is arranged at a distance of D. Here, the angle α of the arc is shown by the angle seen from the midpoint O of the line connecting the dipole antenna 21 and the reflecting element 26, as shown in FIG.

The horizontal directivity of the dipole antenna installed vertically is essentially uniform in all directions. That is, the vertical dipole antenna is omnidirectional. However, according to the configurations shown in FIGS. 1A and 1B, the electromagnetic field emitted from the dipole antenna 21 in the direction of the point O is blocked or reflected by the reflecting element 26. The electromagnetic field reflected by the reflecting element 26 is radiated in the O'point direction. Therefore, the electromagnetic field and the reflected electromagnetic field are directly radiated from the dipole antenna 21 in the O'point direction. The direct electromagnetic field and the reflected electromagnetic field have different phases due to the difference in propagation distance. Therefore, the dipole antenna 21
The electromagnetic field radiated from the direction of O'is also weakened. As a result, the dipole antenna 21 exhibits bidirectional characteristics having strong directivity in the P point direction and the P'point direction.

FIG. 2 shows the relationship between the arc angle α of the reflecting element 26 and the frequency bandwidth having bidirectionality (when F / B is within ± 1 dB). In FIG. 2, the solid line C indicates the distance D = 0.
In the case of 15λ (λ is one wavelength), the solid line E is the distance D = 0.0.
The case of 7λ is shown. As can be seen from FIG. 2, by forming the reflecting element 26 in an arc shape and increasing the arc angle α (the limit is about α = 180 °), it is possible to widen the frequency bandwidth having the bidirectional characteristic. Recognize.

FIG. 3 is a perspective view showing a schematic configuration of the first embodiment constructed based on the principle of the present invention described above. In FIG. 3, 31-1 and 31-2 are radiating elements. In addition, a feeding line passes through the central portions of the radiating elements 31-1, 31-2, the radiating element 31-1 is connected to the inner conductor 32 of the feeding line, and the radiating element 31-2 is connected to the outer conductor 33. Then, these constitute the collinear antenna 34.

The collinear antenna 34 includes spacers 35, 35 made of a dielectric material or an insulating material having a small loss.
Arc-shaped reflecting elements 36, 36 are attached via the. Further, the collinear antenna 34, the spacers 35 and 35, and the reflecting elements 36 and 36 are housed in a cylindrical radome 37 to form a bidirectional antenna 38.

As shown in FIG. 3, generally, the radome 37 accommodating the bidirectional antenna 38 has a cylindrical shape. Therefore, the reflecting element 36 is formed in an arc shape, and the curvature of the reflecting element 36 is set to be the same as that of the radome 37. The antenna 34 can be housed.

FIG. 4 is a diagram showing horizontal directional characteristics of the bidirectional antenna 38 having the configuration shown in FIG. The figure shows a case where the reflecting elements 36, 36 are attached in the x direction shown in the figure from the axis O of the radiating elements 31-1, 31-2. In this case, needless to say, the arc angle α of the reflecting element 36
Is larger than when the reflecting element is formed in a linear shape, it is not necessary to set a large distance D between the radiating element 35 and the reflecting element 36. Therefore, the bidirectional frequency bandwidth can be widened without increasing the outer diameter of the bidirectional antenna 38.

Since the operation and characteristics of this bidirectional antenna 38 are as described above, detailed description thereof will be omitted. Although the spacers 35, 35 of this embodiment have a columnar shape, they may have a shape such as a quadrangular prism or the like that can be easily adhered to the radiating element 31-1 or the radiating element 31-2. Good.

B. Second Embodiment FIG. 5 is a perspective view showing a schematic configuration of a second embodiment of the present invention. In FIG. 5, 41-1 and 41-2 are radiating elements,
Reference numeral 42 is an inner conductor of the power feeding line connected to the radiating element 41-1 and 43 is an outer conductor of the power feeding line connected to the radiating element 41-1. The radiating elements 41-1 and 41-2 are housed in a cylindrical radome 47, and the collinear antenna 4
Make up 4.

A spacer 45 is attached to the outer circumference of the radome 47 in the longitudinal direction. The spacer 45 is formed in a circular arc shape, for example, with a dielectric material having a small loss or acryl, which is another insulating material, and a reflective layer 46 is formed on the surface thereof. The reflective layer 46 shown in FIG. 5 is composed of a metallic paint applied to the surface of the spacer 45. Therefore, the reflective layer 46 has an effect as a reflective element,
A bidirectional antenna 48 having a horizontal bidirectional characteristic is configured.

Since the operation and characteristics of this embodiment are similar to those of the first embodiment, a detailed description thereof will be omitted, but in this embodiment, the collinear antenna 44 which has been conventionally used is
A bidirectional antenna 48 that easily has a horizontal bidirectional characteristic
It is to be. That is, the directional characteristic of the horizontal plane becomes bidirectional simply by attaching the spacer 45 to the collinear antenna 44 having the cylindrical radome 47 and forming the reflective layer 46 on the surface of the spacer 45 with a metallic paint or the like.

In this embodiment, an example in which the reflective layer 46 is formed of a metallic paint has been described. But the reflective layer 4
6 may be formed by attaching a metal tape, for example. Also, without using the spacer 45,
On the inner surface of the radome 47, a reflective layer 4 made of metal paint or the like is used.
6 may be formed.

C. Third Embodiment FIG. 6 is a perspective view showing a schematic configuration of a third embodiment of the present invention. Reference numerals 51-1 and 51-2 are radiating elements that form a printed dipole antenna.
1-1 and 51-2 are composed of copper foil or the like adhered on both sides of the dielectric substrate 55 so as to sandwich the dielectric substrate 55. A high-frequency current is supplied to the radiating elements 51-1 and 51-2 via a microstrip line 52 formed on the surface of the dielectric substrate 55. Therefore, in the dielectric substrate 55, the ground 53 is formed on the symmetrical surface on which the microstrip line 52 is formed.

Radiating element 5 of the printed dipole antenna
The dielectric substrate 55 on which 1-1, 51-2 and the like are formed is housed in a cylindrical radome 57. At the position corresponding to the radiating elements 51-1 and 51-2 on the inner surface of the radome 57, a reflecting element 56 formed in an arc shape is attached along the radome 57.

As described above, this embodiment uses the printed dipole in which the radiating element is printed on the dielectric substrate,
The configuration when the bidirectional antenna 58 is configured is shown. As described above, when the printed circuit board is used, the power supply circuit can also be formed on the circuit board, so that the manufacturing can be simplified even when a complicated power supply circuit is incorporated. The reflective element 56 of the present embodiment may be, for example, a metal plate formed in an arc shape, a metal tape adhered to the inner surface of the radome 57, a metal paint applied to the inner surface of the radome 57, or the like. It may be configured by.

D. Fourth Embodiment FIG. 7 is a perspective view showing a schematic configuration of a fourth embodiment of the present invention. 61-1 and 61-2 are radiating elements, 62 is an inner conductor of a power feeding line connected to the radiating element 61-1 and 63 is an outer conductor of the power feeding line connected to the radiating element 61-1. The radiating elements 61-1 and 61-2 are provided with interdigital reflectors 66 through spacers 65 and 65 made of a dielectric material or an insulating material.
66 is attached. This interdigital reflector 66
Are formed in a wire mesh shape by an array of a plurality of thin lattices 66a.

The radiating elements 61-1 and 61-2, the spacer 65,
65, the interdigital reflectors 66, 66 are housed in a cylindrical radome 67. In addition, the interdigital reflector 6
6 and 66 are arranged in an arc shape along the inner peripheral surface of the radome 67 so that each lattice 66a faces the longitudinal direction of the radiating elements 61-1 and 61-2. In this bidirectional antenna 68, the same effect as that of the first embodiment can be obtained by appropriately selecting the spacing between the gratings 66a. Further, the operation and characteristics of this embodiment are similar to those of the first embodiment, and thus detailed description thereof will be omitted.

Although the spacers 65, 65 of this embodiment have a columnar shape, they have a shape such as a quadratic prism which is easily adhered to the radiating element 61-1 or the radiating element 61-2. It may be. Further, in the present embodiment, each of the gratings 66a of the interdigital reflector 66 may be configured by sticking a narrow metal tape. further,
Even in the above-mentioned second embodiment or third embodiment,
The reflective element may be formed into a comb shape as in the present embodiment.

The numerical values of the distances and arc angles, the materials of the dielectrics and the insulators, the shapes of the spacers and the like mentioned in each of the above-mentioned embodiments are examples, and the present invention is not limited to these. Further, although an example in which a collinear antenna or a printed dipole (half-wavelength dipole antenna) is applied to a bidirectional antenna stored in a cylindrical radome has been described, the present invention can be applied to antennas of other types. is there.

[0038]

As described above, according to the present invention, a parasitic element that is formed on an arcuate surface in parallel with a vertical radiating element that radiates a high frequency current and that absorbs or reflects the radiated high frequency current. Since the frequency bandwidth of the bidirectional antenna having the bidirectionality and having the bidirectional characteristics is expanded, the external shape is thin and horizontal bidirectionality can be obtained in a wide frequency band. The bidirectional antenna and the method for expanding the frequency bandwidth of the antenna can be realized, and further, the effect of reducing the adjustment work in mass production can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining the principle of a bidirectional antenna of the present invention and a method for expanding a frequency bandwidth of the antenna.

FIG. 2 is a diagram showing a relationship between an arc angle α and a frequency bandwidth in the configuration shown in FIG.

FIG. 3 is a perspective view showing a schematic configuration of a bidirectional antenna according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a horizontal plane directional characteristic of the bidirectional antenna of the example.

FIG. 5 is a perspective view showing a schematic configuration of a bidirectional antenna according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a schematic configuration of a bidirectional antenna according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a schematic configuration of a bidirectional antenna according to a fourth embodiment of the present invention.

FIG. 8 is a plan view showing an example of a cell shape of a micro cell communication system.

FIG. 9 is a perspective view showing an external configuration of a conventional collinear antenna with a reflector.

FIG. 10 is a diagram showing horizontal directional characteristics of a conventional vertical collinear antenna and a collinear antenna with a reflector.

11 is a diagram showing a ratio of a distance D to a wavelength λ and a frequency bandwidth capable of maintaining bidirectional characteristics with respect to the ratio in the configuration shown in FIG.

[Explanation of symbols]

 21 dipole antenna 26 reflective element 31-1, 31-2 radiating element 36 reflective element 41-1, 41-2 radiating element 46 reflective layer 51-1, 51-2 radiating element 56 reflective element 61-1, 61-2 radiating Element 66 Reflective element

Claims (8)

[Claims] 1. A bidirectional antenna having bidirectional directivity, comprising a vertical radiating element for radiating a high-frequency current and a parasitic element arranged in parallel with the radiating element. A bidirectional antenna in which the feeding element is formed on an arcuate surface. 2. The radiating element has a spacer made of a dielectric or other insulating material which is parallel to the radiating element and has an outer peripheral portion formed in an arc shape with a small loss, and the parasitic element has an outer periphery of the spacer. The bidirectional antenna according to claim 1, wherein the bidirectional antenna is a metal paint applied to the portion or a metal tape attached to the outer peripheral portion of the spacer. 3. The bidirectional antenna according to claim 1, wherein the parasitic element is formed in a comb shape by a wire net, a metal tape, or the like. 4. The dipole antenna is used as the radiating element.
The bidirectional antenna according to claim 3. 5. The printed antenna comprising a metal film or the like attached to the surface of a dielectric substrate is used as the radiating element.
The bidirectional antenna according to claim 3. 6. A method for expanding a frequency bandwidth of a bidirectional antenna having bidirectional directivity, comprising: a vertical radiating element for radiating a high frequency current; and a parasitic element arranged in parallel with the vertical radiating element. A method for expanding the frequency bandwidth of a bidirectional antenna, characterized in that the parasitic element is formed on an arcuate surface. 7. A spacer made of a dielectric or other insulating material which is parallel to the radiation element and has an outer peripheral portion formed in an arc shape to reduce loss is attached to the radiating element, and the parasitic element is attached to the outer peripheral portion of the spacer. 7. The method for expanding the frequency bandwidth of a bidirectional antenna according to claim 6, wherein the method is configured by a metal paint applied on the surface of the spacer or a metal tape attached to the outer peripheral portion of the spacer. 8. The frequency band width expansion of the bidirectional antenna according to claim 6, wherein the parasitic element is formed in a comb shape by a wire net, a metal tape, or the like. Method.