JP2009118368A - Dipole antenna and dipole array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dipole antenna and a dipole array antenna, capable of implementing both size reduction and turning into wide band of VSWR. <P>SOLUTION: This dipole antenna AN has a reflecting plate 30, a dipole antenna element 10 forming respective element conductors 11 and 12 of a metal plate and arranged in the form of opposing a surface of the respective element conductors 11 and 12 to the reflecting plate 30, and a parasitic element 20, formed of the metal plate and arranged adjacent to the element conductors 11 and 12, in a form opposing its surface to the surface of the element conductors 11 and 12. The dipole array antenna is constituted by arranging a plurality of dipole antennas ANs. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a directional dipole antenna and a dipole array antenna that can be suitably used as a base station antenna in a mobile communication system or the like, and more particularly to a technique for achieving a wider band and a smaller size.

  In mobile communication, the area covered by a single base station is divided into fan-shaped sectors to improve frequency use efficiency. In order to divide the area into a fan shape in this way, it is necessary to radiate radio waves only in a desired fan-shaped range using a directional antenna as a base station antenna.

  In the directional antenna as described above, a reflector is generally disposed behind the antenna element in order to block the directivity behind. When a dipole antenna element is used as the antenna element, the distance from the reflector to the antenna element (the height of the antenna element from the reflector) varies depending on the intended directivity, but generally 0.2λ (λ is It is set before and after the wavelength of the center frequency of the used frequency band.

By the way, a printed dipole antenna element is often used as an antenna element of the directional antenna for reasons such as excellent mass productivity.
For example, Patent Document 1 describes an example of the printed dipole antenna element. Hereinafter, the printed dipole antenna element will be described with reference to FIG. In FIG. 12, a dielectric substrate 100 is erected in a direction perpendicular to the reflector 200, and a printed dipole antenna element 300 and a ground conductor 400 each made of a metal foil are printed on one surface thereof.

The left and right element conductors 301 and 302 constituting the printed dipole antenna element 300 are formed so as to be inclined at a predetermined angle from the feeding point portion toward the reflector 200, and the ground conductor 400 is formed at each feeding point. It is connected.
The ground conductor 400 extends toward the reflecting plate 200, and a slit 401 extending from the antenna element 300 side toward the reflecting plate 200 side is formed at the center thereof.
On the other surface of the dielectric substrate 100, a feed line conductor 500 is printed at a portion located on the back of the ground conductor 400. The feeder line conductor 500 has a shape that extends along the slit 401 from the reflecting plate 200 side, is bent toward the reflecting plate 200 side after traversing the upper end portion of the slit 401.

The printed dipole antenna element 300 is fed by connecting an outer conductor and an inner conductor of a coaxial cable (not shown) to the base of the ground conductor 400 and the base of the feed line conductor 500, respectively. The conductor 500 functions as a balance-unbalance converter (balun).
JP 2006-352293 A

The printed dipole antenna element 300 has, for example, a distance Da from the reflecting plate 200 to its front edge (edge farthest from the reflecting plate 200) when the intended beam width of the horizontal plane directivity is around 80 °. Must be set to 0.23λ or more. The reason is described below.
The printed dipole antenna element 300 has a constant width Wa as shown in the drawing in order to widen the ratio band of VSWR (standing wave ratio). When this width Wa is provided, the front edge of the printed dipole antenna element 300 is further away from the reflector 200, and as a result, the distance Da is set to 0.23λ or more.
The width Wa of the printed dipole antenna element 300 is set to about 0.05λ to 0.15λ, although it varies depending on the operating frequency. For example, when the width Wa is set to 0.05λ, the distance Da is set to approximately 0.23λ.

On the other hand, a base station antenna used for mobile communication is desired to have good VSWR (standing wave ratio) characteristics over a wide band. Conventionally, a parasitic element has been used as means for expanding the specific band of the VSWR.
When the parasitic element is disposed adjacent to the printed dipole antenna element 300, the parasitic element 600 is often printed on the dielectric substrate 100 as shown in FIG. As described above, it is advantageous to improve the productivity by forming the parasitic element 600 on the dielectric substrate 100, but the parasitic element 600 is positioned in the same plane as the printed dipole antenna element 300. Therefore, unless the width Wb of the parasitic element 600 is set to be large, a coupling area necessary for achieving a wide band of the VSWR cannot be obtained.

  Therefore, for example, when the width Wa of the printed dipole antenna element 300 is set to 0.05λ, the width Wb of the parasitic element 600 is set to be as large as about 0.022λ to increase the coupling area. Become. However, when the width Wb of the parasitic element 600 is set to be large as described above, naturally, the distance Db (> Da) from the reflector 200 to the front end edge of the parasitic element 600 increases (in the above example, Db = 0). .26λ). This means that the distance between the reflecting plate 200 and the front edge of the dielectric substrate 100 is Db or more.

  In a base station antenna installed outdoors, the dielectric base 100 on which the printed dipole antenna element 300 and the parasitic element 600 are formed is housed in a dielectric cover. This dielectric cover is often formed in a cylindrical shape in order to reduce the wind pressure load. In consideration of the installation location, the base station antenna is desired to be as small as possible. However, as the protrusion length of the dielectric substrate 100 from the reflector 100 increases, a dielectric cover having a larger diameter is used. As a result, the antenna is increased in size.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a dipole antenna and a dipole array antenna capable of achieving both a reduction in size and a wide band of VSWR.

  In order to achieve the above object, a dipole antenna according to the present invention is a dipole antenna in which a reflecting plate and each element conductor are formed of a metal plate, and a surface of each element conductor faces the reflecting plate. An element and a parasitic element that is formed of a metal plate and is disposed adjacent to the element conductor in a form that faces the element conductor.

It is preferable that the parasitic element is formed such that a gap between the parasitic element and the element conductor is narrowed on the tip end side.
The dipole antenna element and the parasitic element may have a shape in which at least their both ends are inclined toward the reflector side.

  As one embodiment, the dipole antenna element and the parasitic element have a shape in which both ends thereof are inclined at an equal angle toward the reflecting plate side, and the non-inclined portion of the dipole antenna element is provided. The length is set larger than the length of the non-inclined portion of the parasitic element.

  As one embodiment, a pair of parallel grounding conductors standing on the reflecting plate are provided, and the feeding ends of one and the other element conductors of the dipole antenna element are coupled to one and the other of the pair of columns, respectively. For feeding, the central conductor of the feeding cable is connected to the feeding end of the one element conductor, and the outer conductor of the cable is connected to the other support column.

  The present invention also provides a dipole array antenna in which a plurality of dipole antennas are arranged in multiple stages. In this dipole array antenna, the plurality of dipole antennas include a reflector, and each element conductor is formed of a metal plate, and a dipole antenna element disposed in such a manner that the surface of each element conductor faces the reflector. And a parasitic element disposed adjacent to the element conductor in such a manner that the surface thereof is opposed to the surface of the element conductor.

  The plurality of dipole antennas can be used as vertical polarization antennas or horizontal polarization antennas. Further, as an example, the plurality of dipole antennas can be arranged in a staggered manner in the vertical direction across the vertical central axis, and in this case, even if the dipole antennas arranged in the staggered manner constitute a sub-array. Good.

In one embodiment, the plurality of dipole antennas include a first dipole antenna used as a vertically polarized antenna and a second dipole antenna used as a horizontally polarized antenna, The dipole antennas are arranged in a zigzag manner in the vertical direction with the vertical center axis interposed therebetween, and the second dipole antennas are arranged in a zigzag manner in the vertical direction so as not to overlap the first dipole antenna across the vertical center axis line Arranged.
Each of the first and second dipole antennas arranged in a staggered pattern may constitute a subarray.

The dipole antenna according to the present invention includes a reflector, a dipole antenna element made of a metal plate disposed in such a manner that the surface of each element conductor faces the reflector, and the surface faces the surface of the element conductor. Since it is provided with a parasitic element made of a metal plate disposed adjacent to the element conductor in the form, the size can be reduced.
In addition, since the area of the coupling surface of the parasitic element can be easily changed, the amount of coupling of the parasitic element to the dipole antenna element can be appropriately adjusted to achieve a wide band.
The dipole array antenna according to the present invention constituted by the dipole antenna also has the advantages as described above.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 are a side view and a plan view, respectively, showing an embodiment of a dipole antenna AN according to the present invention. The antenna AN includes a dipole antenna element 10, a parasitic element 20, a reflecting plate 30, and a pair of ground conductors 41 and 42 in parallel.

  The dipole antenna element 10 and the parasitic element 20 are each formed of an elongated rectangular metal plate. In the present embodiment, the width W1 of the antenna element 10 and the width W2 of the parasitic element 20 are each set to 0.043λ (λ is the wavelength of the center frequency of the used frequency band). However, the widths W1 and W2 are not limited to this size, and can be arbitrarily set according to the frequency used.

Dipole antenna element 10 has element conductors 11 and 12. The element conductors 11 and 12 extend in the left direction and the right direction in a form parallel to the reflecting plate 30 from the feeding end, respectively, and are then bent toward the reflecting plate 30 side. Therefore, the dipole antenna element 10 has left and right tip portions inclined toward the reflector 30 side.
The parasitic element 20 is arranged such that its surface faces and is adjacent to the antenna element 10. The parasitic element 20 is positioned at a position farther from the reflecting plate 30 than the antenna element 10 and is bent so that the left and right end portions thereof are inclined toward the reflecting plate 30 side.

In the present embodiment, the distance between the left and right bending points of the parasitic element 20 is set slightly shorter than the distance between the left and right bending points of the dipole antenna element 10, and the bending angle of the dipole antenna element 10 is The bending angles of the parasitic element 20 are the same. Therefore, the distance between the dipole antenna element 10 and the parasitic element 20 is narrow on both end portions thereof. In the present embodiment, the bending angle of the dipole antenna element 10 and the parasitic element 20 is set to 135 °.
The reflecting plate 30 bends both end portions along the width direction of the antenna element 10 toward the antenna element 10, thereby forming auxiliary reflecting portions 31 at both end portions.

The ground conductors 41 and 42 are erected on the reflector 30 in a form in which a predetermined interval is formed in the longitudinal direction of the dipole antenna element 10, and the feeding ends of the element conductors 11 and 12 of the respective top end dipole antenna elements 10 are coupled. Has been.
Power is supplied to the dipole antenna element 10 through the power supply cable 50. The power supply cable 50 has a center conductor 50 a connected to the power supply end of the element conductor 11 and an external conductor 51 connected to the ground conductor 42. The ground conductors 41 and 42 have a function as a so-called short balun.

In the dipole antenna AN according to the present embodiment, the antenna element 10 and the parasitic element 20 are formed of a metal plate, and the antenna element 10 is disposed in such a manner that the surface of the antenna element 10 faces the reflecting plate 30. The surface is arranged so as to face the antenna element 10.
Therefore, according to the dipole antenna AN according to the present embodiment, although the antenna element 10 has a predetermined width, this width increases the height dimension of the dipole antenna AN from the reflector 30. Similarly, the width of the power feeding element 20 does not cause the increase in the height dimension.

When the antenna element 10 and the parasitic element 20 are accommodated in the dielectric cover together with the reflecting plate 30, it is necessary to increase the diameter of the dielectric cover as the height dimension increases.
However, as described above, according to the dipole antenna AN according to the present embodiment, since the height dimension can be reduced, compared with the conventional antenna using the printed dipole antenna element shown in FIG. A small-diameter dielectric cover can be used, and as a result, it can be made smaller than a conventional antenna.

FIG. 3 exemplifies the dimensions of each part of the dipole antenna AN according to the present embodiment in the case where a beam width in the horizontal plane near 80 ° is realized. As shown in FIG. 3, according to the dipole antenna according to the present embodiment, the height dimension can be reduced to about 0.2λ.
The base station antenna used for mobile communication is desirably as small as possible in consideration of the installation location. Therefore, the dipole antenna AN according to the present embodiment that can be reduced in size is suitable as the base station antenna.

  By the way, the VSWR (standing wave ratio) characteristics of the dipole antenna AN according to the present embodiment vary depending on the shape of the dipole antenna element 10 and the shape of the reflector 30, but the coupling amount of the parasitic element 20 to the antenna element 10 is also different. It becomes the change factor. The amount of coupling varies depending on the width and length of the parasitic element 20 and the distance of the parasitic element 20 from the antenna element 10.

  Since the dipole antenna AN according to the present embodiment can easily adjust the coupling amount due to its configuration, it is possible to increase the bandwidth of the VSWR. Further, in the dipole antenna AN according to the present embodiment, the distance of the parasitic element 20 from the antenna element 10 (the distance between the antenna element 10 and the parasitic element 20) is left and right as compared with the central portion of the parasitic element 20. It is comprised so that it may become narrow at the front-end | tip part side. When such a configuration is employed, the amount of coupling can be adjusted so that the VSWR is further broadened. Such an effect based on the above configuration has been confirmed by experiments and the like.

The antenna AN according to the present invention shown in FIG. 1 exhibits a return loss characteristic as shown in FIG. 4 and a directivity in a horizontal plane as shown in FIG. 5 when the center frequency f ₀ of the used frequency band is 900 MHz. As is apparent from these drawings, according to the antenna AN according to the present invention, a wide specific band 23.7 satisfying a return loss of −13.9 dB (VSWR <1.5) despite being miniaturized. %, And excellent horizontal directivity can be realized. Note that the lower limit frequency f ₁ and the upper limit frequency f ₂ of the specific band shown in FIG. 4 are 794 MHz and 1008 MHz, respectively.

6 and 7 show the return loss characteristic and the horizontal plane directivity of the conventional antenna shown in FIG. 13, respectively.
As is clear from each figure, in the conventional antenna, the ratio band satisfying the return loss of −13.9 dB (VSWR <1.5) is as narrow as 15%, and the directivity in the horizontal plane is also the same directivity as shown in FIG. Somewhat inferior. Note that the lower limit frequency f ₁ and the upper limit frequency f ₂ of the specific band shown in FIG. 6 are 833.5 MHz and 969 MHz, respectively.

  As is clear from the above comparison, the antenna AN according to the present invention is highly practical because it can realize a good VSWR characteristic and excellent directivity in a horizontal plane while achieving downsizing. Therefore, it can be suitably used particularly as the base station antenna.

FIGS. 8 to 11 are conceptual diagrams showing first to fourth embodiments of the dipole array antenna according to the present invention configured using the antenna AN, respectively.
The dipole array antenna shown in FIG. 8 has a configuration in which the antennas AN used as vertically polarized antennas are arranged in a staggered pattern in the vertical direction with the vertical center axis L interposed therebetween. Since the array antenna according to the present embodiment can increase the distance between the individual antennas AN, the electrical interference between them can be suppressed, and a good VSWR (standing wave ratio) characteristic and horizontal plane orientation can be achieved. Can be realized

The array antenna shown in FIG. 9 uses a subarray in which the antennas AN are arranged at predetermined intervals in the vertical direction, and this subarray is arranged in a staggered pattern in the vertical direction across the vertical center axis L. Have.
Note that the number of antennas AN constituting the sub-array is not limited to 2, and can be set to any number of 2 or more.

The array antenna shown in FIG. 10 arranges the antennas AN used as vertically polarized antennas in a zigzag manner in the vertical direction across the vertical center axis L, and the antennas AN used as horizontally polarized antennas are It has a configuration that is arranged in a staggered manner so as not to overlap with the antenna AN used as the vertically polarized antenna.
According to the antenna according to the present embodiment, in addition to the effect of the antenna shown in FIG. 8, the effect that the horizontally polarized wave and the vertically polarized wave can be shared is obtained.

The array antenna shown in FIG. 11 includes a first subarray in which the antennas AN used as vertical polarization antennas are arranged at predetermined intervals in the vertical direction, and the antenna AN used as horizontal polarization antennas. Are arranged in a vertical direction with a predetermined interval, and the first subarray is arranged in a staggered pattern in the vertical direction across the vertical central axis L, and the second subarray is The first subarray is arranged in a staggered manner so as not to overlap the first subarray.
The number of antennas AN that constitute the first and second subarrays is not limited to two, and can be set to any number of two or more.

The present invention is not limited to the configuration of the above embodiment, and includes various modifications. That is, in the embodiment shown in FIG. 1, the bending angle of the antenna element 10 and the parasitic element 20 is the same, but the individual bending angles may be different. It is also possible to bend only one of the antenna element 10 and the parasitic element 20 or to prevent both the antenna element 10 and the parasitic element 20 from being folded. Furthermore, the bending directions of the antenna element 10 and the parasitic element 20 are not limited to the bending directions shown in FIGS.
Further, in the antenna AN shown in FIG. 1, only the tip portions of the element conductors 11 and 12 are inclined by bending the middle of the element conductors 11 and 12 of the antenna element 10. You may comprise so that the whole may be inclined. The parasitic element 20 can also be bent at the left and right midpoint positions.

On the other hand, each antenna AN in the dipole array antenna shown in FIGS. 8 and 9 is used as a vertically polarized antenna. However, the antenna AN may be arranged to be used as a horizontally polarized antenna. Is possible.
In configuring the dipole array antenna, the antennas AN may be simply arranged at predetermined intervals in the vertical direction as shown on the left side or the right side of the vertical center axis L in FIG. The same applies to the subarray shown in FIG.
Similarly, in configuring the dipole array antenna, as shown on the left side or the right side of the vertical center axis L in FIG. 10, the vertical polarization antenna AN and the horizontal polarization antenna AN are simply set in the vertical direction. Alternatively, they may be alternately arranged at predetermined intervals. The same applies to the subarray shown in FIG.
In addition, although the antenna AN which comprises an array antenna may have the reflecting plate 30 shown in FIG. 1 separately, you may integrate the reflecting plate of each antenna AN.

1 is a side view showing an embodiment of a dipole antenna according to the present invention. It is a top view of the dipole antenna shown in FIG. FIG. 2 is a side view illustrating dimensions of each part of the dipole antenna illustrated in FIG. 1. 3 is a graph illustrating the return loss characteristic of the dipole antenna shown in FIG. 1. 2 is a graph illustrating the directivity in the horizontal plane of the dipole antenna shown in FIG. 1. It is the graph which illustrated the return loss characteristic of the conventional dipole antenna. It is the graph which illustrated the directivity in the horizontal surface of the conventional dipole antenna. 1 is a conceptual diagram showing a first embodiment of a dipole array antenna according to the present invention. It is a conceptual diagram which shows 2nd Embodiment of the dipole array antenna which concerns on this invention. It is a conceptual diagram which shows 3rd Embodiment of the dipole array antenna which concerns on this invention. It is a conceptual diagram which shows 4th Embodiment of the dipole array antenna which concerns on this invention. It is the side view which illustrated the composition of the conventional dipole antenna which is not provided with a parasitic element. It is the side view which illustrated the composition of the conventional dipole antenna provided with the parasitic element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dipole antenna element 11, 12 Element conductor 20 Parasitic element 30 Reflector 41, 42 Ground conductor 50 Feed cable

Claims (12)

A reflector,
Each element conductor is formed of a metal plate, and a dipole antenna element disposed in a form in which the surface of each element conductor faces the reflecting plate;
A parasitic element formed by a metal plate, the surface of which is disposed adjacent to the element conductor in a form facing the surface of the element conductor;
A dipole antenna characterized by comprising:   The dipole antenna according to claim 2, wherein the parasitic element is formed such that an interval between the parasitic element and the element conductor is narrowed on a tip end side thereof.   The dipole antenna element and the parasitic element have a shape in which at least both ends thereof are inclined toward the reflecting plate side.   The dipole antenna element and the parasitic element have a shape in which both end portions thereof are inclined at an equal angle toward the reflector, and the length of the non-inclined portion of the dipole antenna element is the non-inclined portion. The dipole antenna according to claim 2, wherein the dipole antenna is set to be longer than the length of the non-inclined portion of the feed element.   A pair of parallel grounding conductors standing on the reflecting plate is provided, and feeding ends of one and the other element conductors of the dipole antenna element are coupled to one and the other of the pair of support columns, respectively. 2. The dipole antenna according to claim 1, wherein a conductor is connected to a feeding end of the one element conductor, and an outer conductor of the cable is connected to the other support column. A dipole array antenna in which a plurality of dipole antennas are arranged in multiple stages, wherein the plurality of dipole antennas,
A reflector,
Each element conductor is formed of a metal plate, and a dipole antenna element disposed in a form in which the surface of each element conductor faces the reflecting plate;
A parasitic element formed by a metal plate, the surface of which is disposed adjacent to the element conductor in a form facing the surface of the element conductor;
A dipole array antenna comprising:   The dipole array antenna according to claim 6, wherein the plurality of dipole antennas are used as vertically polarized antennas.   The dipole array antenna according to claim 6, wherein the plurality of dipole antennas are used as horizontally polarized antennas.   The dipole array antenna according to any one of claims 6 to 8, wherein the plurality of dipole antennas are arranged in a staggered pattern in a vertical direction across a vertical center axis.   10. The dipole array antenna according to claim 9, wherein the dipole antennas arranged in a zigzag form a subarray.   The plurality of dipole antennas include a first dipole antenna used as a vertically polarized antenna and a second dipole antenna used as a horizontally polarized antenna, and the first dipole antenna has a vertical center axis. The second dipole antennas are arranged in a zigzag pattern in the vertical direction with the vertical dipole antenna interposed therebetween, and the second dipole antennas are arranged in a zigzag pattern in the vertical direction so as not to overlap the first dipole antenna. The dipole array antenna according to claim 6.   The dipole array antenna according to claim 11, wherein each of the first and second dipole antennas constitutes a subarray.

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