JP6593645B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device suitable for use as a base station antenna for mobile communication.

  A base station antenna for mobile communication has a plurality of antenna devices (sector antennas) corresponding to each of a plurality of cells in an area handled by the base station antenna, and each antenna device is directed to a predetermined cell. The radio wave is transmitted, and the radio wave transmitted from a predetermined cell is received.

  Each antenna device includes a container generally called a “radome”, a reflection plate, a vertical polarization element, and a horizontal polarization element housed in the container. The vertical polarization element is disposed in the vicinity of the reflection plate to transmit / receive vertical polarization, and the horizontal polarization element is disposed in the vicinity of the reflection plate to transmit / receive horizontal polarization. For example, the horizontal polarization element is erected perpendicular to one surface of the reflection plate, and a pair of vertical polarization elements are erected obliquely with respect to the one surface of the reflection plate. In other words, one horizontal polarization element is disposed between a pair of vertical polarization elements. The respective vertical polarization elements are inclined so as to be separated from each other as they are separated from one surface of the reflecting plate, and have a V shape or a Y shape as a whole.

JP, 2015-33018, A

  When a plurality of antenna devices are arranged adjacent to each other, interference between radio waves radiated from the respective antenna devices becomes a problem. There is a desired wave-to-interference wave ratio (DU ratio / Desired to Unsigned signal ratio) as one of the indexes related to such interference between radio waves.

  For example, the DU ratio for an arbitrary one (target sector antenna) of three antenna devices (sector antennas) having the same characteristics arranged at intervals of 120 degrees is obtained as follows. Using the position of the target sector antenna as a reference (0 degree), the highest radio wave level (relative gain) [dB] for each angle, the second highest radio wave level (relative gain) [dB], and the third highest radio wave level ( Relative gain) [dB] is measured. At this time, the highest radio wave level is the level of radio waves radiated from the target sector antenna, and the second and third highest radio wave levels are levels of radio waves radiated from sector antennas other than the target sector antenna. . In other words, the radio wave indicating the highest level is a desired wave, and the radio waves indicating the second and third highest levels are interference waves.

  Therefore, for each angle, the desired wave to interference wave ratio (DU ratio) is obtained by subtracting the sum of the second largest radio wave level and the third largest radio wave level from the largest radio wave level at the angle.

  As described above, the DU ratio is a value obtained by subtracting the interference wave level from the desired wave level at each angle, and a high DU ratio means that there are few interference waves at the angle. In addition, a wide angle range in which the DU ratio is higher than a predetermined value means that the antenna device exhibits good antenna characteristics over a wide range.

  Therefore, in the antenna device, it is desired to improve the DU ratio by reducing unnecessary radio waves (side lobes or the like) other than the main beam as much as possible.

  Conventionally, the DU ratio of an antenna device including a pair of vertical polarization elements that have a V-shape or a Y-shape as a whole and one horizontal polarization element disposed between the vertical polarization elements is improved. As a technique, there is a technique of adjusting the interval between the vertical polarization element and the horizontal polarization element. Specifically, the angle (opening angle) formed by the pair of vertical polarization elements is increased or decreased to bring the vertical polarization element close to or away from the horizontal polarization element.

  However, according to the above method, the DU ratio of the vertical polarization and the horizontal polarization changes simultaneously. For this reason, it is difficult or impossible to improve only the DU ratio of horizontal polarization. On the other hand, in improving the DU ratio of the antenna device, there is a case where it is desired to improve only the DU ratio of horizontal polarization without affecting the DU ratio of vertical polarization.

  An object of the present invention is to improve the DU ratio of horizontal polarization while suppressing the influence on the DU ratio of vertical polarization.

  The antenna device of the present invention is an antenna device that transmits and receives horizontal polarization and vertical polarization. The antenna device is disposed along the longitudinal direction of the first reflector on the container, the first reflector housed in the container, and on one side of the first reflector within the container. A plurality of antenna element groups, and a second reflector disposed in parallel with the first reflector on the other side of the first reflector within the container. Each of the antenna element groups includes a horizontal polarization element, a first vertical polarization element and a second vertical polarization element which are arranged on both sides of the horizontal polarization element and are opposed to each other with the horizontal polarization element interposed therebetween. An element. The second reflecting plate is provided with a plurality of slits facing the horizontally polarized wave elements included in the antenna element groups with the first reflecting plate interposed therebetween. The center in the longitudinal direction of each of the slits is located immediately below the opposing horizontal polarization element.

  In one aspect of the present invention, the length of each of the slits is a length corresponding to a half wavelength of the operating frequency of the antenna device.

  In another aspect of the present invention, the width of each of the slits is 1 mm or more and 15 mm or less.

  In another aspect of the present invention, the width of each of the slits is 5 mm or more and 10 mm or less.

  According to the present invention, it is possible to improve the DU ratio of horizontal polarization while suppressing the influence on the DU ratio of vertical polarization.

1 is a perspective view showing an overall configuration of an antenna device to which the present invention is applied. It is sectional drawing which shows the whole structure of the antenna apparatus with which this invention was applied. It is sectional drawing which shows the positional relationship of an antenna element group and a 2nd reflecting plate. It is a top view of a 2nd reflecting plate. (A) is a graph showing horizontal plane directivity of horizontal polarization (H polarization) radiated from an antenna device as a comparative example, and (b) is a vertical polarization radiated from an antenna device as a comparative example. It is a graph which shows the horizontal surface directivity of a wave (V polarization). (A) is a graph which shows the horizontal plane directivity of the horizontally polarized wave (H polarized wave) radiated | emitted from the antenna apparatus to which this invention was applied, (b) is radiation | emission from the antenna apparatus to which this invention was applied. It is a graph which shows the horizontal surface directivity of vertical polarization (V polarization) to be performed.

  Hereinafter, an example of an embodiment of an antenna device of the present invention will be described in detail with reference to the drawings.

  The antenna device according to the present embodiment is an antenna device used as one of sector antennas constituting a base station antenna for mobile communication. The base station antenna includes an antenna device (sector antenna) corresponding to each cell in the area handled by the base station antenna. For example, when the area handled by the base station antenna is divided into three at 120 ° intervals in the horizontal plane, that is, when the area is divided into three cells, the base station antennas are arranged at 120 ° intervals. With two antenna devices. Each antenna device transmits and receives radio waves to and from communication terminals in the assigned cell.

  FIG. 1 is a perspective view showing an overall configuration of an antenna device 1 according to the present embodiment. The antenna device 1 shown in FIG. 1 has a cylindrical container 2 generally called a “radome”. Inside the container 2, there are two metal plates 11, 12 facing each other, a substrate 13 disposed between the two metal plates 11, 12, a plurality of antenna element groups 20, and one metal. The board 30 is accommodated.

  In FIG. 1, the antenna device 1 is shown in a lying state for the convenience of drawing. However, the antenna device 1 stands up when used as a sector antenna of a base station antenna. Specifically, the antenna device 1 is used in a standing state so that the axis of the container 2 is vertical or substantially vertical.

  The substrate 13 is formed of a dielectric material, and conductor layers (not shown) are formed on the front and back surfaces of the substrate 13, respectively. That is, the substrate 13 on which the conductor layer is formed and the pair of metal plates 11 and 12 facing each other across the substrate 13 constitute a triplate line as a whole, and this triplate line is connected to each antenna element group 20. Electrically connected. That is, each metal plate 11 and 12 functions as a ground plate constituting a triplate line. On the other hand, each of the metal plates 11 and 12 also functions as a first reflecting plate that reflects radio waves radiated from the antenna element group 20. Therefore, in the following description, the metal plate 11 shown in FIG. 1 may be referred to as “upper metal plate 11” and the metal plate 12 may be referred to as “lower metal plate 12”. Further, the upper metal plate 11 and the lower metal plate 12 may be collectively referred to as “first reflector 10”. Further, the metal plate 30 functions as a second reflecting plate that reflects radio waves radiated from the antenna element group 20. Therefore, in the following description, the metal plate 30 shown in FIG. 1 may be referred to as a “second reflector 30”.

  The first reflecting plate 10 has a substantially rectangular planar shape whose longitudinal direction is the axial direction of the container 2. The first reflector 10 is arranged at the radial center or substantially the center of the container 2 and bisects or substantially bisects the internal space of the container 2. The antenna element group 20 is provided in the container 2 and on one side of the first reflector 10, and the second reflector 30 is provided in the container 2 and on the other side of the first reflector 10. ing. That is, the antenna element group 20 and the second reflecting plate 30 are located on opposite sides of the first reflecting plate 10.

  Both ends in the width direction of the upper metal plate 11 and the lower metal plate 12 are bent at right angles to form side walls 11a and 12a. However, the side wall 11a of the upper metal plate 11 and the side wall 12a of the lower metal plate 12 rise in opposite directions. Specifically, the side wall 11a of the upper metal plate 11 rises toward one side of the first reflector 10 on which the antenna element group 20 is provided, and the side wall 12a of the lower metal plate 12 is the second side. It rises toward the other side of the first reflector 10 on which the reflector 30 is provided. Moreover, the side wall 30a raised in the same direction as the side wall 11a is provided in the width direction both ends of the 2nd reflecting plate 30. As shown in FIG.

  As shown in FIG. 2, the plurality of antenna element groups 20 provided on one side of the first reflector 10 are arranged in a line at a predetermined pitch along the longitudinal direction of the first reflector 10. The second reflector 30 provided on the other side of the first reflector 10 is parallel to the first reflector 10. Further, the second reflector 30 is provided with a plurality of slits 31 arranged in a line at the same pitch as the antenna element group 20.

  As shown in FIG. 1, each antenna element group 20 includes one horizontal polarization element 21 that transmits and receives horizontal polarization and two vertical polarization elements (first vertical polarization elements that transmit and receive vertical polarization). 22 and a second vertical polarization element 23). As shown in FIG. 3, the horizontal polarization element 21 includes arm portions 21a and 21b extending in opposite directions, and functions as a first dipole antenna. The arm portion 21 a extends from the upper end of the horizontal polarization element 21 toward the first vertical polarization element 22, and the arm portion 21 b extends from the upper end of the horizontal polarization element 21 to the second vertical polarization element 23. It is growing towards. Also, the pair of first vertical polarization element 22 and second vertical polarization element 23 function as a second dipole antenna. That is, each antenna element group 20 including the horizontal polarization element 21, the first vertical polarization element 22, and the second vertical polarization element 23 can transmit and receive both horizontal polarization and vertical polarization. It is. Lower ends of the horizontal polarization element 21, the first vertical polarization element 22, and the second vertical polarization element 23 are connected to a conductor layer (not shown) formed in the substrate 13 through the upper metal plate 11. . That is, the horizontal polarization element 21, the first vertical polarization element 22, and the second vertical polarization element 23 are electrically connected to the above-described triplate line.

  As shown in FIG. 3, the horizontal polarization element 21 included in each antenna element group 20 is disposed at the center in the width direction of the first reflector 10. On the other hand, the first vertical polarization element 22 and the second vertical polarization element 23 included in each antenna element group 20 are arranged on both sides of the horizontal polarization element 21 included in the antenna element group 20, and the horizontal Opposite the polarization element 21.

  Further, the horizontal polarization element 21 is perpendicular to the first reflection plate 10, while the first vertical polarization element 22 and the second vertical polarization element 23 are inclined with respect to the first reflection plate 10. . Specifically, the first vertical polarization element 22 and the second vertical polarization element 23 are inclined in opposite directions so that the distance between the first vertical polarization element 22 and the second vertical polarization element 23 increases as the distance from the first reflector 10 increases. In FIG. 3, the first vertical polarization element 22 is inclined to the right side, and the second vertical polarization element 23 is inclined to the left side.

  Further, the inclination angles of the first vertical polarization element 22 and the second vertical polarization element 23 with respect to the horizontal polarization element 21 are the same. Therefore, the first vertical polarization element 22 and the second vertical polarization element 23 are symmetric about the horizontal polarization element 21.

  The second reflecting plate 30 faces the antenna element group 20 with the first reflecting plate 10 interposed therebetween. As shown in FIGS. 2 and 3, the plurality of slits 31 provided in the second reflector 30 sandwich the horizontal polarization element 21 and the first reflector 10 included in each antenna element group 20. Opposite. In other words, each slit 31 is disposed directly behind the corresponding horizontal polarization element 21 (directly below in FIGS. 2 and 3).

  As shown in FIG. 4, each slit 31 is a band-shaped through-hole extending along the longitudinal direction of the second reflecting plate 30, and the center in the longitudinal direction is located directly below the opposing horizontal polarization element 21. is doing. The length (L) of each slit 31 is a length corresponding to ½ wavelength of the use frequency of the antenna device 1. The use frequency bands of the antenna device 1 according to the present embodiment are a 700 [MHz] band and an 800 [MHz] band. Therefore, in this embodiment, the length (L) of each slit 31 is set to a length corresponding to a half wavelength of the intermediate frequency (750 [MHz]). The width (W) of each slit 31 is preferably in the range of 1 mm to 15 mm, and more preferably in the range of 5 mm to 10 mm. In addition, the width (W) of each slit 31 is preferably narrowed as the operating frequency of the antenna device 1 increases. In the present embodiment, the width (W) of each slit 31 is set to 5 mm.

  The 1st reflecting plate 10 and the 2nd reflecting plate 30 which are shown by FIG. 1 are being fixed to the internal peripheral surface of the container 2 via the fixing member not shown. However, the first reflector 10 and the second reflector 30 are electrically insulated, and the second reflector 30 is electrically floating. Moreover, the space | interval of the board | substrate 13 and the upper side metal plate 11 and the space | interval of the board | substrate 13 and the lower side metal plate 12 are maintained at the predetermined space | interval by the spacer not shown.

  As described above, in the antenna device 1 according to the present embodiment, the second reflecting plate 30 including the slit 31 is disposed directly behind the horizontal polarization element 21 included in each antenna element group 20. The presence of the second reflecting plate 30 improves the DU ratio of horizontal polarization. In other words, the DU ratio of the horizontally polarized wave can be improved without substantially affecting the DU ratio of the vertically polarized wave.

  The graph shown in FIG. 5A shows 700 [MHz] band and 800 [MHz] band radiated from the antenna device (comparative example) in which the second reflector 30 shown in FIG. It is a graph which shows the simulation result regarding the horizontal surface directivity of horizontal polarization (H polarization). Moreover, the graph shown in FIG.5 (b) is a graph which shows the simulation result regarding the horizontal surface directivity of 700 [MHz] band and the 800 [MHz] band vertical polarization (V polarization) radiated | emitted from the said comparative example. It is.

  On the other hand, the graph shown in FIG. 6A shows 700 [MHz] band and 800 [MHz] band radiated from the antenna device 1, that is, the antenna device 1 of the present embodiment in which the second reflector 30 is provided. It is a graph which shows the simulation result regarding the horizontal surface directivity of horizontal polarization (H polarization). Moreover, the graph shown in FIG. 6B is a graph showing the simulation result regarding the horizontal plane directivity of 700 [MHz] band and 800 [MHz] band vertically polarized waves (V polarized waves) radiated from the antenna device 1. It is. In this simulation, the length (L) of the slit 31 shown in FIG. 4 is set to a length corresponding to a half wavelength of 700 [MHz].

  Further, the shaded portions in the graphs shown in FIGS. 5A and 5B and FIGS. 6A and 6B are unnecessary lobes (interference waves) other than the main lobe (desired wave). Indicates the region (angle range) in which. In other words, a region (angular range) between two shaded portions in each graph indicates a region (angular range) where a main lobe (desired wave) appears.

  Comparing FIG. 5A and FIG. 6A, in the antenna device 1, the gain of the interference wave decreases in both the 700 [MHz] band and the 800 [MHz] band as compared with the comparative example. You can see that That is, in the antenna device 1, compared with the comparative example, the gain of the desired wave relative to the gain of the interference wave is relatively increased, and the DU ratio (desired wave to interference wave ratio) of the horizontally polarized wave is improved. .

  On the other hand, when FIG. 5B and FIG. 6B are compared, the gain of interference waves in the 700 [MHz] band and 800 [MHz] band in the antenna apparatus 1 and the 700 [MHz] band and 800 in the comparative example are compared. The gain of the interference wave in the [MHz] band is the same. That is, the DU ratio (desired wave to interference wave ratio) of the vertically polarized wave in the antenna device 1 is the same as the DU ratio (desired wave to interference wave ratio) of the vertically polarized wave in the comparative example.

  As described above, in the antenna device 1 provided with the second reflecting plate 30 including the slit 31, the DU ratio of horizontal polarization is improved, but the DU ratio of vertical polarization is not affected.

  According to the simulation performed by the present inventors, in the antenna device 1 according to this embodiment, the angular range in which the DU ratio of horizontal polarization is greater than 25 [dB] in the 700 [MHz] band is 133.2 degrees. On the other hand, it was 86.4 degrees in the comparative example. That is, in the antenna device 1, the angular range in which the DU ratio of the horizontally polarized wave is larger than 25 [dB] in the 700 [MHz] band is increased by 46.8 degrees. Similarly, in the antenna device 1 according to the present embodiment, the angular range in which the DU ratio of horizontal polarization is greater than 25 [dB] in the 800 [MHz] band is 122.4 degrees, whereas in the comparative example, 118. It was 8 degrees. That is, in the antenna device 1, the angle range in which the DU ratio of the horizontally polarized wave is larger than 25 [dB] in the 800 [MHz] band is increased by 3.6 degrees.

  In the antenna device 1 and the comparative example according to the present embodiment, the angular range in which the DU ratio of vertically polarized waves is larger than 25 [dB] in the 700 [MHz] band is the same at 93.6 degrees. Similarly, in the antenna device 1 and the comparative example according to the present embodiment, the angular range in which the DU ratio of vertically polarized waves is larger than 25 [dB] in the 800 [MHz] band is the same at 118.8 degrees.

  According to the above simulation, in the antenna device 1, in one of the used frequency bands (700 [MHz] band), the DU ratio of horizontal polarization is greatly improved, while the DU ratio of vertical polarization is not affected. confirmed. Further, it was confirmed that the DU ratio of both the horizontally polarized waves and the vertically polarized waves was not substantially affected for the other of the used frequency bands (800 [MHz] band). In this simulation, since the length (L) of the slit 31 is set to a length corresponding to a half wavelength of 700 [MHz], only the DU ratio of horizontal polarization in the 700 [MHz] band is greatly improved. As a result.

  However, if the length (L) of the slit 31 is set to a length corresponding to a half wavelength of the intermediate frequency (750 [MHz]), the horizontal deviation is observed in both the 700 [MHz] band and the 800 [MHz] band. The DU ratio of the wave is improved. Further, if the length (L) of the slit 31 is set to a length corresponding to a half wavelength of 800 [MHz], only the DU ratio of the horizontally polarized wave in the 800 [MHz] band is greatly improved. Further, when the use frequency band is the same, the wider the width (W) of the slit 31, the greater the angular range in which the DU ratio is greater than 25 [dB].

  In this way, by adjusting the length and width of the slit 31, it is possible to improve the DU ratio of horizontal polarization in an arbitrary frequency band without affecting the DU ratio of vertical polarization.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the horizontal polarization element 21, the first vertical polarization element 22, and the second vertical polarization element 23 in the above embodiment are metal plates processed into a predetermined shape. However, these polarization elements 21, 22, and 23 can be replaced with polarization elements (antenna elements) having a dielectric substrate and a conductor pattern formed on the surface of the dielectric substrate.

  Further, the feed line for supplying power to each antenna element group 20 is not limited to the triplate line, and power may be supplied to each antenna element group 20 via a line having another structure.

  In the above embodiment, the three antenna element groups 20 are provided in the container 2, but the number of antenna element groups 20 can be increased or decreased as appropriate. Further, when the number of antenna element groups 20 is increased or decreased, the number of slits 31 is also increased or decreased accordingly.

  In the above embodiment, the upper metal plate 11 is provided with a side wall 11a, the lower metal plate 12 is provided with a side wall 12a, and the second reflecting plate 30 is provided with a side wall 30a. However, these side walls 11a, 12a, and 30a are not essential elements of the present invention, and can be appropriately omitted in consideration of desired antenna characteristics.

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Container 10 1st reflecting plate 11 Upper metal plate 12 Lower metal plates 11a, 12a, 30a Side wall 13 Substrate 20 Antenna element group 21 Horizontal polarization element 21a, 21b Arm part 22 First vertical polarization element 23 First 2 Vertical polarization element 30 Second reflector 31 Slit

Claims (4)

An antenna device for transmitting and receiving horizontal polarization and vertical polarization,
A container,
A first reflector housed in the container;
A plurality of antenna element groups arranged in the container and on one side of the first reflector along the longitudinal direction of the first reflector;
A second reflector disposed in parallel with the first reflector on the other side of the first reflector within the container,
Each of the antenna element groups includes a horizontal polarization element, a first vertical polarization element and a second vertical polarization element which are arranged on both sides of the horizontal polarization element and are opposed to each other with the horizontal polarization element interposed therebetween. An element,
The second reflector is provided with a plurality of slits opposed to the horizontal polarization element included in each antenna element group with the first reflector interposed therebetween,
The longitudinal center of each of the slits is located directly below the opposing horizontal polarization element,
Antenna device. The antenna device according to claim 1,
The length of each of the slits is a length corresponding to a half wavelength of the use frequency of the antenna device.
Antenna device. The antenna device according to claim 2, wherein
The width of each slit is 1 mm or more and 15 mm or less,
Antenna device. The antenna device according to claim 3, wherein
The width of each slit is 5 mm or more and 10 mm or less,
Antenna device.

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