JP2006191331A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna which has a wide parasitic element and is band-widened. <P>SOLUTION: The antenna is provided with a half-wavelength dipole antenna element and a wide parasitic element arranged on the half-wavelength dipole antenna element. When free space wavelength in center frequency to be used of the half-wavelength dipole antenna element is defined as λo, and the length of the parasitic element in a direction identical to the extended direction of the half-wavelength dipole antenna element is defined as H0, the width of the parasitic element is defined as W0, and an interval between the parasitic element and the half-wave length dipole antenna element is defined as T0, expressions: 0.1×λo≤H0≤0.5×λo, 1.0×H0≤W0≤2.5×H0, and 0.01×λo≤T0≤0.2×λo are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna, and more particularly to a base station antenna used for a mobile communication base station.

As a base station antenna for mobile communication, a corner reflector antenna using a printed dipole antenna element as a radiating element is often employed because of easy electrical adjustment and excellent mass productivity.
The base station antenna is preferably as small as possible due to tight installation space and problems with the capacity of equipment such as steel towers.
However, if the beam width is narrowed in a limited space, it is necessary to make the distance between the reflector and the radiating element closer, making it difficult to achieve matching.
In order to increase the bandwidth of the antenna, it can be realized by arranging a parasitic element in the vicinity of the antenna element.
In general, in a half-wave dipole antenna, a linear parasitic element disposed in the vicinity of the half-wave dipole antenna element is used as the parasitic element, but a corner reflector antenna using a wide parasitic element is used. It is disclosed in the following Patent Document 1.

As prior art documents related to the invention of the present application, there are the following.
Japanese Patent Laid-Open No. 2002-325016

In the corner reflector antenna described in the above-mentioned Patent Document 1, a radiating element substrate is inserted into each of the two-fold reflectors from an oblique direction, and a parasitic element formed on another dielectric substrate is placed in front of the radiating element substrate. By arranging it, the directivity is symmetric with respect to the front direction, facilitating impedance matching, enabling miniaturization, and reducing wind pressure load.
However, in the above-mentioned Patent Document 1, it is possible to increase the bandwidth by using a wide parasitic element, and furthermore, the optimum conditions (dimensions, etc.) of the wide parasitic element for achieving the broadband. Is not disclosed at all.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide an antenna having a wide parasitic element and a wide band.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
To achieve the foregoing object, the present invention provides an antenna having a half-wave dipole antenna element and a wide parasitic element disposed on the half-wave dipole antenna element, the half-wave dipole antenna element Λo is a free space wavelength at the center frequency of use, H0 is the length of the parasitic element in the same direction as the extension direction of the half-wave dipole antenna element, W0 is the width of the parasitic element, and the parasitic element and the half When the interval between the wavelength dipole antenna elements is T0, the following expression (1) is satisfied.
[Equation 1]
0.1 × λo ≦ H0 ≦ 0.5 × λo
1.0 × H0 ≦ W0 ≦ 2.5 × H0
0.01 × λo ≦ T0 ≦ 0.2 × λo (1)

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the antenna which has a wide parasitic element and aimed at broadband.

Hereinafter, embodiments in which the present invention is applied to a corner reflector antenna will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
1A and 1B are diagrams showing a corner reflector antenna according to an embodiment of the present invention. FIG. 1A is a perspective view, and FIG.
In the figure, 1 ₁ and 1 ₂ are reflectors, 2 is a dielectric substrate, 3 is a half-wave dipole antenna element, and 6 is a wide parasitic element.
In this embodiment, two sets of planar reflectors (1 ₁ , 1 ₂ ) are arranged so that the opening angle (θ in FIG. 1A) is 120 °.
Here, two pairs of flat reflecting plate ₍₁ 1, _{1 2)} the length of (H1 in FIGS. 1 (a)), two pairs of flat reflecting plate ₍₁ 1, _{1 2)} in width (FIGS. 1 (a) W1) and the distance between the center in the width direction of the half-wavelength dipole antenna element 3 and the reflector (1 ₁ , 1 ₂ ) (T1 in FIG. 1B) are values of the following equation (2): The
[Equation 2]
H1 = 2 × λo
W1 = 0.32 × λo
T1 = 0.18 × λo (2)
Note that λo is a free space wavelength at the use center frequency (fo) of the half-wave dipole antenna element 3 shown in FIG.
Further, since the corner reflector antenna is desired to have a small diameter because of problems such as installation space capacity and wind pressure load, the values of W1 and T1 described above are necessary to obtain a 90 ° horizontal beam width. Is determined as the minimum value.

In this embodiment, the parasitic element 6 is provided in the vicinity of the dielectric substrate 2 on which the half-wave dipole antenna element 3 is formed. In FIG. 1, the parasitic element 6 is provided so as to be orthogonal to the dielectric substrate 2 as shown in FIG.
The parasitic element 6 is formed on a dielectric substrate different from the dielectric substrate 2 by an etching method or the like used for a printed wiring board.
Here, the length of the parasitic element 6 in the same direction as the extension direction of the half-wavelength dipole antenna element 3 (H0 in FIG. 1A), the width of the parasitic element 6 (W0 in FIG. 1A), The distance between the parasitic element 6 and the center of the half-wavelength dipole antenna element 3 in the width direction (T0 in FIG. 1B) is a value of the following equation (3).
[Equation 3]
0.1 × λo ≦ H0 ≦ 0.5 × λo
1.0 × H0 ≦ W0 ≦ 2.5 × H0
0.01 × λo ≦ T0 ≦ 0.2 × λo (3)

FIG. 2 is a diagram for explaining the half-wave dipole antenna element 3 shown in FIG.
In FIG. 2, 13 ₁ and 13 ₂ are a pair of radiating elements, 4 is a ground conductor that forms a feed circuit, and 5 is a folded conductor that forms the feed circuit.
The length of the conductor constituting the half-wave dipole antenna element 3 is λo / 2.
As shown in FIG. 2, a pair of radiating elements (13 ₁ , 13 ₂ ) and a ground conductor 4 constituting the dipole antenna element 3 are provided on one surface side (for example, the back surface side) of the dielectric substrate 2, The folded conductor 5 is provided on the other surface side (for example, the front surface side) of the dielectric substrate 2. Here, the dielectric substrate 2 has a relative dielectric constant of 3.5 (εr = 3.5) and a substrate thickness of 1.2 mm.
The pair of radiating elements (13 ₁ , 13 ₂ ), the ground conductor 4 and the folded conductor 5 are formed by an etching technique or the like used for a printed wiring board.
A longitudinal slot 21 is provided at the front end of the ground conductor 4, and each of the pair of radiating elements (13 ₁ , 13 ₂ ) of the dipole antenna element 3 is divided by the longitudinal slot 21. Is connected to the front end of the division.
The folded conductor 5 and a part of the ground conductor 4 constitute a balanced-unbalanced conversion circuit (balanced-unbalanced conversion circuit using a microstrip line).

FIG. 3 is a graph showing the VSWR characteristics of an example of the corner reflector antenna according to the present embodiment. FIG. 3 is a graph showing VSWR characteristics under the following conditions (1) to (4).
(1) The relative dielectric constant of the dielectric substrate on which the parasitic element 6 is formed is 3.5 (εr = 3.5), and the substrate thickness is 1.2 mm.
(2) The length of the parasitic element 6 (H0 in FIG. 1A) is 0.2 × λo (H0 = 0.2 × λo).
(3) The width of the parasitic element 6 (W0 in FIG. 1A) is 0.26 × λo (W0 = 0.26 × λo).
(4) The width-direction center and interval between the parasitic element 6 and the half-wavelength dipole antenna element 3 (T0 in FIG. 1B) is 0.035 × λo (T0 = 0.035 × λo).
In the graph shown in FIG. 3, the specific bandwidth satisfying VSWR ≦ 1.5 is 27.5% (0.994 ≦ f / fo ≦ 1.311).
FIG. 7 is a graph showing the VSWR characteristics in the case of a single half-wave dipole antenna element. The antenna in this case is equivalent to the structure in which the parasitic element 6 shown in FIG.
In the graph shown in FIG. 7, the specific bandwidth satisfying VSWR ≦ 1.5 is 1.3% (0.992 ≦ f / fo ≦ 1.005).
FIG. 9 shows the VSWR characteristics when a linear parasitic element 7 is arranged in the vicinity of the half-wave dipole antenna element 3 as shown in FIG.
In the graph shown in FIG. 9, the specific bandwidth satisfying VSWR ≦ 1.5 is 13.8% (0.989 ≦ f / fo ≦ 1.135).
From these graphs, it can be seen that in this embodiment, the bandwidth is increased about 21 times that of a single half-wave dipole antenna element and about twice that of the case where the linear parasitic element 7 is arranged.

FIG. 4 is a graph showing the directivity characteristics in the horizontal plane (XY plane shown in FIG. 1) of an example of the corner reflector antenna of this embodiment, and the beam width in the horizontal plane is 88.5 °.
FIG. 5 is a graph showing the directivity characteristics in the vertical plane (XZ plane shown in FIG. 1) of an example of the corner reflector antenna of the present embodiment, and the vertical in-plane beam width is 52.5 °. Also, in the graphs of FIGS. 4 and 5, the solid line is the positive polarization component, and the dotted line is the cross polarization component.
FIG. 6 is a perspective view showing a modification of the corner reflector antenna according to the embodiment of the present invention. FIG. 6 shows a plurality of antennas shown in FIG. 1 arranged in an array. In FIG. 6, the half-wave dipole antenna element 3 is illustrated as a linear half-wave dipole antenna element.
As described above, according to the present embodiment, it is possible to achieve a wide band by optimizing the shape of the wide parasitic element 6.
In the above description, the embodiment in which the present invention is applied to the corner reflector antenna has been described. However, the present invention is not limited to this, and for example, the shape of the reflector is a planar reflector. Alternatively, a semi-cylindrical reflector may be used.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

It is a figure which shows the corner reflector antenna of the Example of this invention. It is a figure for demonstrating the half-wavelength dipole antenna element shown in FIG. It is a graph which shows the VSWR characteristic of an example of the corner reflector antenna of the Example of this invention. It is a graph which shows the directional characteristic in the horizontal surface (XY plane shown in FIG. 1) of an example of the corner reflector antenna of the Example of this invention. It is a graph which shows the in-plane (XZ surface shown in FIG. 1) directivity characteristic of an example of the corner reflector antenna of the Example of this invention. It is a perspective view which shows the modification of the corner reflector antenna of the Example of this invention. It is a graph which shows the VSWR characteristic in the case of a half wavelength dipole antenna element single-piece | unit. It is a figure for demonstrating the half-wavelength dipole antenna element which has arrange | positioned the linear parasitic element in the vicinity. It is a graph which shows the VSWR characteristic at the time of arrange | positioning a linear parasitic element in the vicinity of a half-wave dipole antenna element.

Explanation of symbols

1 ₁ , 1 ₂ Reflecting plate 2 Dielectric substrate 3 Dipole antenna element 4 Ground conductor 5 Folded conductor 6, 7 Parasitic element 13 ₁ , 13 ₂ Radiating element 21 Longitudinal slot

Claims (1)

A half-wave dipole antenna element;
An antenna having a wide parasitic element disposed on the half-wave dipole antenna element,
The free space wavelength at the center frequency of use of the half-wave dipole antenna element is λo, the length of the parasitic element in the same direction as the extension direction of the half-wave dipole antenna element is H0, the width of the parasitic element is W0, An antenna characterized by satisfying the following expression when a distance between a parasitic element and the half-wave dipole antenna element is T0.
0.1 × λo ≦ H0 ≦ 0.5 × λo
1.0 × H0 ≦ W0 ≦ 2.5 × H0
0.01 × λo ≦ T0 ≦ 0.2 × λo

Images