JP2008061085A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simply structured antenna capable of controlling directivity in a wide frequency band. <P>SOLUTION: An antenna comprises a first antenna device, multiple second antenna devices, a distributor for distributing a signal path from a feeding point to a first path leading to the first antenna device and a second path leading to the second antenna device, and a switch for selecting some of the multiple second antenna devices and connecting them to the distributor. Two adjacent second antenna devices contained in the multiple second antenna devices are positioned in a way that two straight lines connecting the two second antenna devices and the first antenna device intersect at a predefined angle except 180° and 360°. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna device that electrically controls directivity.

  There is a wireless LAN as a wireless communication system mainly used indoors. When a wireless communication system is used indoors, reflection, scattering, or diffraction of radio waves may occur or the propagation path of radio waves may be shielded by room structures or furniture. Furthermore, the fading environment of radio waves may change due to movement of people or objects. Since these cause degradation of communication quality, it is desirable to use an antenna that can reduce the influence of fading in such a wireless communication system.

  A phased array antenna is known as an antenna that can reduce the influence of fading. The phased array antenna includes a subarray antenna having a plurality of antenna elements, and a variable phase shifter and a variable amplitude adjuster (variable gain amplifier or variable attenuator) connected to each subarray antenna. Since the antenna element of each sub-array antenna outputs a radio wave having an amplitude adjusted by the variable amplitude adjuster with a phase controlled by the phase shifter, the phased array antenna can realize a desired directivity. However, since this phased array antenna includes a phase shifter and a variable amplitude adjuster for each subarray antenna, the configuration is complicated and large. Moreover, the manufacturing cost is high.

  An object of the invention described in Patent Document 1 is to provide an array antenna device having a simple configuration and low manufacturing cost and capable of controlling directivity. As shown in FIG. 12, the array antenna apparatus includes a first antenna element arranged at the center, and a plurality of second antenna element groups arranged at equal distances from the first antenna element at equal intervals. , A phase shifter 5 that changes the phase of power feeding to the first antenna element, a phase shift controller 6 that controls the phase shifter 5, and a plurality of second antenna elements that are adjacent to each other. A power feeder 7 that feeds power to each of the second antenna elements with a predetermined phase difference between the antenna elements, and a phase shifter 5 and the power feeder 7, and power distribution to the phase shifter 5 and the power feeder 7. Alternatively, it includes a distributor / combiner 8 that combines power from the phase shifter 5 and the power feeder 7. In this array antenna apparatus, the phase shifter 5 changes the directivity of the array antenna apparatus by changing the excitation phase of the first antenna element.

JP 2003-347824 A

  Although the array antenna apparatus described above has a smaller number of phase shifters than the phased array antenna, the phase shifter 5 connected to the first antenna element is necessary, and power is supplied to each of the second antenna elements. A power feeder 7 is also required. Moreover, since the array antenna apparatus described above uses the phase difference of the antenna elements to be excited, the frequency that can be used is limited. For this reason, the applicable frequency band is narrow.

  An object of the present invention is to provide an antenna device with a simple configuration that can control directivity in a wide frequency band.

  The present invention includes a first antenna element, a plurality of second antenna elements, a first path that connects a signal path from a feeding point to the first antenna element, and the plurality of second antenna elements. A distribution unit that distributes to a second path that communicates with the switch, a switching unit that selects a part of the plurality of second antenna elements and connects the selected second antenna element and the distribution unit; The two second antenna elements adjacent to each other included in the plurality of second antenna elements have two straight lines connecting each of the two second antenna elements and the first antenna element. Provided is an antenna device arranged to intersect at a predetermined angle other than 180 degrees and 360 degrees.

  In the antenna device, the plurality of second antenna elements are arranged at an equal distance from the first antenna element.

  In the antenna device, the predetermined angle is 90 degrees or 270 degrees.

  In the antenna device, the first antenna element and the plurality of second antenna elements are arranged on the same plane.

  According to the antenna device of the present invention, since no transfer device is provided, directivity can be controlled in a wide frequency band, and the configuration is simple.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing the arrangement of antenna elements included in the antenna device of the first embodiment. FIG. 2 is a top view showing the arrangement of antenna elements included in the antenna device of the first embodiment. FIG. 3 is a block diagram of the antenna device of the first embodiment. As shown in FIGS. 1 and 2, the antenna device of the first embodiment includes a first antenna element 11 and two second antenna elements 13a and 13b. The first antenna element 11 and the two second antenna elements 13a and 13b are half-wave dipole antennas.

  The second antenna elements 13a and 13b are arranged on the circumference of a circle having a radius of λ / 2 with the first antenna element 11 as the center. That is, the distance between the first antenna element 11 and the second antenna element 13a and the distance between the first antenna element 11 and the second antenna element 13b are both equal to λ / 2. Further, in the second antenna elements 13a and 13b, the straight line connecting the first antenna element 11 and the second antenna element 13a is orthogonal to the straight line connecting the first antenna element 11 and the second antenna element 13b. Has been placed.

  The antenna device of the present embodiment includes a distribution unit 15 and a switch unit 17 in addition to the first antenna element 11 and the second antenna elements 13a and 13b. The distribution unit 15 distributes the high-frequency signal input from the feeding point 19 into two. The distribution ratio is 1: 1. One high frequency signal distributed by the distribution unit 15 is supplied to the first antenna element 11, and the other high frequency signal is supplied to the switch unit 17. The switch unit 17 selects one of the second antenna elements 13 a and 13 b and connects the selected second antenna element and the distribution unit 15. Therefore, the high frequency signal supplied to the switch unit 17 is supplied to the selected second antenna element. The selection of the second antenna element by the switch unit 17 is controlled by a control unit (not shown).

  4 and 5 are directional characteristics diagrams on the horizontal plane (XY plane in FIG. 1) of the antenna device of the present embodiment. FIG. 4 is a directivity characteristic diagram when the second antenna element 13a is selected, and FIG. 5 is a directivity characteristic diagram when the second antenna element 13b is selected. When the second antenna element 13a is selected, a high frequency signal is radiated from the first antenna element 11 and the second antenna element 13a. The high frequency signals radiated from the first antenna element 11 and the second antenna element 13a strengthen each other in the X direction shown in FIG. 2 and weaken each other in the Y direction shown in FIG. As a result, as shown in FIG. 4, the directivity when the second antenna element 13a is selected is strong in the X direction and weak in the Y direction. Note that the half-power angle at this time is about 50 degrees.

  On the other hand, when the second antenna element 13b is selected, a high frequency signal is radiated from the first antenna element 11 and the second antenna element 13b. The high-frequency signals radiated from the first antenna element 11 and the second antenna element 13b weaken each other in the X direction and strengthen each other in the Y direction. As a result, as shown in FIG. 5, the directivity when the second antenna element 13b is selected is weak in the X direction and strong in the Y direction. Note that the half-power angle at this time is about 50 degrees.

  Thus, the high-frequency signal radiated from the first antenna element 11 and the high-frequency signal radiated from the second antenna element influence each other, and the directivity of the XY plane depends on the arrangement of the second antenna element. Change. In order to selectively realize different directivities as in the present embodiment, the two straight lines connecting each of the second antenna elements 13a and 13b and the first antenna element 11 are other than 180 degrees or 360 degrees. The second antenna elements 13a and 13b need to be arranged so as to intersect at a predetermined angle (90 degrees in this embodiment).

  As described above, according to the antenna device of the present embodiment, the directivity in the horizontal plane changes when the second antenna element that supplies a high-frequency signal is switched. Switching of the second antenna element is performed by controlling the switch unit 17. Thus, the antenna device of this embodiment does not need to include a phase shifter. Therefore, since the antenna device capable of controlling directivity can be realized with a simple configuration, the antenna device can be reduced in size. In addition, the manufacturing cost can be reduced due to the simple configuration. Further, in the antenna device of the present embodiment, it is not necessary to change the phase when supplying a signal to the antenna element, so that the frequency characteristic of the antenna element alone can be used as it is. For this reason, it can respond to a wide frequency band.

  In the present embodiment, the distance between the first antenna element 11 and the second antenna elements 13a and 13b has been described by taking λ / 2 as an example. However, the distance is not limited to λ / 2 as long as the distance is equal. .

(Second Embodiment)
FIG. 6 is a perspective view showing the arrangement of antenna elements included in the antenna device of the second embodiment. FIG. 7 is a top view showing the arrangement of antenna elements included in the antenna device of the second embodiment. The antenna device of the second embodiment is different from the antenna device of the first embodiment in the arrangement of the second antenna element. Except for this point, the second embodiment is the same as the first embodiment.

  The antenna device of the second embodiment includes a first antenna element 11 similar to that of the first embodiment, and two second antenna elements 23a and 23b. The second antenna element 23a is disposed at a position λ / 2 from the first antenna element 11, and the second antenna element 23b is disposed at a position 2λ / 5 from the first antenna element 11. Further, in the second antenna elements 23a and 23b, the straight line connecting the first antenna element 11 and the second antenna element 23a is orthogonal to the straight line connecting the first antenna element 11 and the second antenna element 23b. Has been placed.

  8 and 9 are directional characteristics diagrams on the horizontal plane (XY plane in FIG. 6) of the antenna device of the present embodiment. FIG. 8 is a directivity characteristic diagram when the second antenna element 23a is selected, and FIG. 9 is a directivity characteristic diagram when the second antenna element 23b is selected. When the second antenna element 23a is selected, a high frequency signal is radiated from the first antenna element 11 and the second antenna element 23a. The directivities at this time strengthen each other in the X direction shown in FIG. 7, and slightly weaken each other in the Y direction shown in FIG. As a result, as shown in FIG. 8, the directivity when the second antenna element 23a is selected is strong in the X direction and slightly weak in the Y direction. Note that the half-power angle at this time is about 80 degrees.

  On the other hand, when the second antenna element 23b is selected, a high-frequency signal is radiated from the first antenna element 11 and the second antenna element 23b. The high-frequency signals radiated from the first antenna element 11 and the second antenna element 23b weaken each other in the X direction and strengthen each other in the Y direction. As a result, as shown in FIG. 9, the directivity when the second antenna element 23b is selected is weak in the X direction and strong in the Y direction. Note that the half-power angle at this time is about 50 degrees.

  Thus, the half-power angle changes according to the distance of the second antenna element from the first antenna element 11. For example, by changing the distance of the second antenna element arranged in the Y direction from the first antenna element 11, the half-power angle in the directivity in the X direction of the antenna device changes. For this reason, the half-power angle can be controlled by changing the distance of the second antenna element from the first antenna element 11.

  In the first and second embodiments described above, an example in which two straight lines connecting each of the two second antenna elements and the first antenna element 11 are orthogonal to each other has been described. As described above, in order to selectively realize different directivities, the second antenna element needs to be arranged so that these two straight lines intersect at a predetermined angle other than 180 degrees or 360 degrees. . For this reason, the angle at which these two straight lines intersect is not limited to a right angle, and may be, for example, 105 degrees as shown in FIGS.

  In the first and second embodiments, half-wave dipole antennas have been described as examples of the first antenna element 11 and the second antenna elements 13a, 13b, 23a, and 23b. However, a monopole antenna, a sleeve antenna, or the like is used. The linear antenna may be used. Furthermore, although the case where the number of second antenna elements is two has been described as an example, it may be three or more. When three or more second antenna elements are provided, the number of the second antenna elements selected by the switch unit 17 and connected to the distributor 15 is not limited to one and may be plural. However, a configuration in which all the second antenna elements are connected to the distributor 15 is excluded. In this case, the plurality of second antenna elements may be divided into a plurality of groups and switched by the switch unit 17 in units of groups.

  The antenna device according to the present invention is useful as an antenna that can electrically control directivity in a wide frequency band.

The perspective view which shows arrangement | positioning of the antenna element which the antenna apparatus of 1st Embodiment has The top view which shows arrangement | positioning of the antenna element which the antenna apparatus of 1st Embodiment has Block diagram of the antenna device of the first embodiment Directional characteristic diagram in horizontal plane of antenna apparatus of first embodiment Directional characteristic diagram in horizontal plane of antenna apparatus of first embodiment The perspective view which shows arrangement | positioning of the antenna element which the antenna apparatus of 2nd Embodiment has The top view which shows arrangement | positioning of the antenna element which the antenna apparatus of 2nd Embodiment has Directional characteristic diagram in horizontal plane of antenna apparatus of second embodiment Directional characteristic diagram in horizontal plane of antenna apparatus of second embodiment The perspective view which shows arrangement | positioning of the antenna element which the antenna apparatus of other embodiment has The top view which shows arrangement | positioning of the antenna element which the antenna apparatus of other embodiment has Block diagram of a conventional array antenna device

Explanation of symbols

11 1st antenna element 13a, 13b, 23a, 23b 2nd antenna element 15 Distribution part 17 Switch part

Claims (4)

A first antenna element;
A plurality of second antenna elements;
A distribution unit that distributes a signal path from a feeding point to a first path that communicates with the first antenna element and a second path that communicates with the plurality of second antenna elements;
A switching unit that selects a part of the plurality of second antenna elements and connects the selected second antenna element and the distribution unit;
The two second antenna elements adjacent to each other included in the plurality of second antenna elements are 180 degrees with two straight lines connecting each of the two second antenna elements and the first antenna element. An antenna device arranged to intersect at a predetermined angle other than 360 degrees. The antenna device according to claim 1,
The plurality of second antenna elements are arranged equidistant from the first antenna element, respectively. The antenna device according to claim 1,
The antenna apparatus according to claim 1, wherein the predetermined angle is 90 degrees or 270 degrees. The antenna device according to claim 1,
The antenna device, wherein the first antenna element and the plurality of second antenna elements are arranged on the same plane.

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