JP2014007687A - Antenna and wireless communication device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna having a radiation pattern for suppressing radiation in the sky direction and becoming cosecant square curve in the ground direction, and having an electrical tilt while maintaining a high radiation gain, and to provide a wireless communication device including the same.SOLUTION: An antenna 10 includes a plurality of antenna elements 21, 22, ..., 2n, and feeding means 30 for feeding power having an amplitude decreasing toward both end sides of an array and a phase which advances gradually toward one end side and delays gradually toward the other end side.

Description

  The present invention relates to an antenna and a radio communication apparatus including the antenna, and more particularly to an antenna used as a base station antenna and a radio communication apparatus using the antenna.

  A base station antenna used for mobile communication is usually installed at a high place. Data is transmitted and received between the base station and the ground fixed communication terminal or mobile communication terminal by radio waves radiated from the antenna. One of the base station antennas includes a plurality of antenna elements arranged in a vertical direction and provided with a power feeding circuit that feeds each antenna element with a predetermined amplitude and phase.

  For example, Patent Document 1 discloses that a plurality of antenna elements are added with a phase obtained by combining a first phase distribution represented by an odd function and a second phase distribution represented by an even function, thereby An antenna that realizes a null-fill beam is disclosed in which direction radiation is suppressed and a cosecant square curve is formed in the ground direction.

  By suppressing the radiation in the sky direction, interference between the base station antennas and between the base station antenna and the satellite communication is reduced. In addition, by having the radiation characteristic of the cosecant square curve, the mobile terminal that communicates with the base station has a substantially constant electric field intensity on the ground regardless of the distance from the base station antenna.

JP 2009-218677 A

  Here, in order to maintain good communication quality, it is desirable that the radiation gain of the beam radiated from the antenna is not less than a predetermined level. In addition, it is desirable that the radiation angle of the main beam can be set to a predetermined angle from the antenna horizontal plane so that radio waves are radiated in a desired direction on the ground side.

  Note that the radiation angle of the main beam is set by an electrical tilt that is electrically set so that the radiation pattern from the antenna becomes a constant angle, and a mechanical tilt that is set by tilting the antenna. can do.

  The object of the present invention has been made in view of the above problems, and has an emission pattern in which the radiation in the sky direction is suppressed, has a cosecant square curve in the ground direction, and an electric tilt is maintained while maintaining a high radiation gain. It is an object of the present invention to provide an antenna and a wireless communication apparatus including the antenna.

  In order to achieve the above object, an antenna according to the present invention includes a plurality of antenna elements arranged in an array, the amplitude of the antenna elements decreasing as it goes to both ends of the array, and the advance amount as it goes to one end. And a power feeding means for feeding a phase in which the delay amount increases as going to the other end side.

  In order to achieve the above object, a wireless communication apparatus according to the present invention is a wireless communication apparatus provided with the antenna described above.

  The antenna and the wireless communication apparatus including the antenna according to the present invention have a radiation pattern that suppresses radiation in the sky direction, forms a cosecant square curve in the ground direction, and has an electric tilt while maintaining a high radiation gain.

It is (a) block block diagram and (b) electric power feeding distribution of the antenna 10 which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the installation state of the antenna 100 which concerns on the 2nd Embodiment of this invention. It is sectional drawing when the antenna 100 which concerns on the 2nd Embodiment of this invention is cut | disconnected by (a) transparent perspective view and (b) XX. It is a perspective view of the printed circuit board 500 which concerns on the 2nd Embodiment of this invention. It is the electric power feeding distribution of the antenna 100 which concerns on the 2nd Embodiment of this invention. It is a radiation characteristic of the antenna 100 which concerns on the 2nd Embodiment of this invention. It is electric power feeding distribution of the antenna 100 which concerns on the 1st modification of the 2nd Embodiment of this invention. It is a radiation characteristic of the antenna 100 which concerns on the 1st modification of the 2nd Embodiment of this invention. It is the electric power feeding distribution of the antenna 100 which concerns on the 2nd modification of the 2nd Embodiment of this invention. It is a radiation characteristic of the antenna 100 which concerns on the 2nd modification of the 2nd Embodiment of this invention. It is electric power feeding distribution of the antenna 100 which concerns on the 3rd modification of the 2nd Embodiment of this invention. It is a radiation characteristic of the antenna 100 which concerns on the 3rd modification of the 2nd Embodiment of this invention.

(First embodiment)
An antenna according to a first embodiment of the present invention will be described. FIG. 1A shows a block configuration diagram of an antenna according to the present embodiment. 1A, the antenna 10 according to the present embodiment includes a plurality of antenna elements 21, 22,..., 2n (n is an integer of 5 or more) and a power feeding unit 30.

  In the present embodiment, the antenna 10 is used as a base station antenna, and the antenna 10 is installed vertically so that the antenna element 21 is on the ground side and the antenna element 2n is on the zenith side.

  When the antenna 10 is used as a base station antenna used for mobile communication, it is desirable to form a beam pattern with a beam width of about 6 degrees on the vertical plane and 60 to 180 degrees on the horizontal plane. In order to form a beam width of about 6 degrees on the vertical plane while maintaining a desired gain, the number of antenna elements is preferably about 12 to 14 elements. In order to obtain a beam width of 60 to 180 degrees on a horizontal plane, a reflector made of a metal plate may be disposed on the back surface of the antenna element. Further, in order to withstand an outdoor environment, the antenna 10 can be covered with a radome made of a resin such as FRP (Fiber Reinforced Plastics), PPE (poly phenylene ether), or ABS.

  Returning to the description of FIG. The plurality of antenna elements 21, 22,..., 2 n are arranged in an array, and each radiates an electromagnetic wave corresponding to the amplitude and phase fed from the power feeding means 30 and receives the electromagnetic wave from the space. In the present embodiment, the antenna elements 21, 22,..., 2n are arranged in a line at equal intervals around the antenna element 2k.

  The power feeding means 30 has an amplitude that decreases as it goes to both ends of the array, and an advance amount that increases toward the one end, and increases toward the other end, toward the antenna elements 21, 22,. The phase is fed with a delay amount that increases as it goes.

  A case where the power feeding means 30 feeds power to the seven antenna elements 21, 22, ..., 27 will be described. An example of the power distribution in this case is shown in FIG. As shown in FIG. 1 (b), the power feeding means 30 according to the present embodiment supplies power having the largest amplitude to the antenna element 24 arranged at the center, and both ends of the power feeding means 30 are line targets from the antenna element 2k. The amplitude of the electric power fed toward the antenna element 21 and the antenna element 27 arranged in the antenna is reduced.

  Further, as shown in FIG. 1B, the feeding unit 30 is arranged at the center by delaying the phase so that the amount of change increases from the antenna element 24 arranged at the center toward the antenna element 21 at the other end. The phase is advanced so that the amount of change increases from the antenna element 24 thus formed toward the antenna element 27 on one end side.

  By feeding the antenna elements 21, 22,..., 27 arranged in an array with the amplitude and phase shown in FIG. 1 (b), the radiation characteristics of the antenna 10 are suppressed, and the radiation in the sky direction is suppressed. It has a radiation pattern that becomes a cosecant square curve in the direction, and has an electrical tilt while maintaining a high radiation gain.

  Here, when the amount of decrease in amplitude is increased from the antenna element 24 toward the antenna elements 21 and 27, the radiation in the sky direction can be further suppressed. On the other hand, when the amount of decrease in amplitude from the antenna element 24 to the antenna elements 21 and 27 is made constant, a drop (null) in the radiation characteristics can be reduced.

  As described above, the antenna 10 according to this embodiment has a plurality of antenna elements arranged in an array with an amplitude that decreases as it goes to both ends of the array, and an advance amount that increases as it goes to one end. A phase where the delay amount increases as it goes to the other end side is fed. In this case, the radiation characteristics of the antenna 10 are such that the radiation in the sky direction is suppressed, has a radiation pattern that becomes a cosecant square curve in the ground direction, and has an electric tilt while maintaining a high radiation gain.

  When the antenna 10 according to the present embodiment is applied to a base station antenna, the interference between the base station antennas and between the base station antenna and the satellite communication device can be reduced by suppressing the radiation in the sky direction. In addition, by having a radiation pattern that is a cosecant square curve in the ground direction, a mobile terminal that communicates with a base station can obtain radiation characteristics with a substantially constant electric field strength independent of the distance from the base station antenna. it can. Further, by suppressing nulls, it is possible to reduce an area with low communication quality.

  Further, when the antenna 10 is applied to a base station antenna, the electric field strength in the vicinity of the base station can be maintained at a desired strength by having an electric tilt while maintaining a high radiation gain.

(Second Embodiment)
A second embodiment will be described. FIG. 2 shows a perspective view when the antenna according to this embodiment is attached to the antenna attachment pole. In FIG. 2, the antenna 100 according to the present embodiment is fixed to the antenna mounting pole 800 via two mounting brackets 700 so that the longitudinal direction is the vertical direction.

  FIG. 3A is a transparent perspective view of the antenna 100 according to this embodiment, and FIG. 3B is a cross-sectional view when the antenna 100 of FIG. 3A is cut along line XX. 3A and 3B, the antenna 100 according to this embodiment includes a housing 200, 13 radiating elements 300 a to 300 m, 13 center poles 400 a to 400 m, and a printed circuit board 500.

  The housing 200 includes a main body 210 and a cover 220. The main body 210 is a long box formed by bending a metal plate. The main body 210 includes a rectangular space with a low profile and an open top. Inside this space, the radiating elements 300a to 300m, the center poles 400a to 400m, and the printed circuit board 500 are arranged.

  The cover 220 is a metal plate, and is disposed above the main body 210 to cover the space where the radiating elements 300a to 300m, the center poles 400a to 400m, and the printed circuit board 500 are disposed. In order to protect the antenna 100, the housing 200 may be disposed in a resin case such as FRP (Fiber Reinforced Plastics) or PPC (polypropylene carbonate).

  The radiating elements 300a to 300m are connected to the radiating elements 510a to 510m formed on the printed circuit board 500 via the center poles 400a to 400m, respectively. In the present embodiment, the radiating elements 300a to 300m and the radiating elements 510a to 510m are connected via the center poles 400a to 400m to constitute the patch antennas 600a to 600m.

  Center poles 400a to 400m connect radiating elements 300a to 300m and radiating elements 510a to 510m formed on printed circuit board 500, respectively. By connecting the radiating elements 300a to 300m and the radiating elements 510a to 510m with the center poles 400a to 400m, the band of the patch antennas 600a to 600m can be increased.

  The printed circuit board 500 is formed of a dielectric or the like, and is disposed inside the main body 210 of the housing 200. A perspective view when the printed circuit board 500 is arranged in the main body 210 is shown in FIG. As shown in FIG. 4, a printed circuit board 500 according to the present embodiment is fixed to a main body 210, and 13 radiating elements 510a to 510m, feeding points 520 and 530, and feeding circuits 540 and 550 are formed on an upper surface. Yes.

  The radiating elements 510a to 510m are formed in one row on the upper surface of the printed circuit board 500 at a predetermined interval. As described above, the radiating elements 510a to 510m are connected to the radiating elements 300a to 300m via the center poles 400a to 400m, respectively, thereby configuring the patch antennas 600a to 600m.

  The feeding points 520 and 530 supply power to the radiating elements 510a to 510m through the feeding circuits 540 and 550.

  The feed circuits 540 and 550 are lines including a distribution unit, a delay unit, and the like. The power supplied from the feed points 520 and 530 is controlled to a predetermined excitation amplitude and phase, and is supplied to the radiation elements 510a to 510m. The feeder circuits 540 and 550 are designed with the line thickness and length so that the electric power can be controlled to a desired excitation amplitude and phase. In the present embodiment, as shown in FIG. 4, the power feeding circuits 540 and 550 are configured to branch stepwise from the power feeding points 520 and 530 to the radiating elements 510a to 510m.

  In the present embodiment, the power supply circuit 540 supplies power to the radiating elements 510a to 510m from the width direction. That is, in FIG. 2, power is supplied from the horizontal direction while the antenna 100 is fixed to the antenna mounting pole 800. The patch antennas 600a to 600m radiate horizontally polarized waves having a horizontal beam width in accordance with the width of the main body 210 of the casing 200 and the characteristics of the patch antenna by feeding the radiation elements 510a to 510m from the horizontal direction. To do.

  On the other hand, the power supply circuit 550 supplies power to the radiating elements 510a to 510m from the longitudinal direction. That is, in FIG. 2, power is supplied from the vertical direction while the antenna 100 is fixed to the antenna mounting pole 800. The patch antennas 600a to 600m radiate vertically polarized waves having a beam pattern in the vertical direction corresponding to the excitation amplitude and phase of the supplied power by being fed from the vertical direction to the radiating elements 510a to 510m.

  FIG. 5 shows the excitation amplitude and phase (feeding distribution) of energy supplied to the radiating elements 510a to 510m by the feeding circuits 540 and 550 according to the present embodiment. In FIG. 5, antenna numbers a-m correspond to patch antennas 600a-600m, respectively. Further, in FIGS. 2 to 4, the patch antenna 600a is positioned downward (the ground direction), and the patch antenna 600m is positioned upward (the zenith direction).

  In FIG. 5, the power supply circuits 540 and 550 supply electric power with the largest amplitude to the central patch antenna 600g, and the amplitude of the supplied energy decreases as it goes to the ground direction and the zenith direction. Further, the amount of change in amplitude is increased as it goes in the ground direction and the zenith direction.

  Further, in FIG. 5, phase feeding power is supplied by feeding circuits 540 and 550 from the central patch antenna 600g so as to be a line target, which progresses in the zenith direction and delays in the ground direction. Further, the amount of change in phase increases as it goes in the ground direction and the zenith direction.

  The antenna 100 according to the present embodiment exhibits the radiation characteristics shown in FIG. 6 when the patch antennas 600a to 600m are supplied with the power of the excitation amplitude and phase shown in FIG. Here, Elevation Angle θ in FIG. 6 corresponds to the radiation angle in the vertical direction in front of the antenna shown in FIG. That is, the Elevation Angle θ is 0 degrees in the zenith direction, 180 degrees in the ground direction, and 90 degrees in the horizontal direction.

  In FIG. 6, the radiation characteristics of the antenna 100 according to the present embodiment are such that the sky side lobe (0 to 90 degrees) from the horizontal direction to the upward direction is suppressed to 25 dB or less. Further, the radiation angle of the main lobe is 92 degrees, and an angle of 2 degrees is initially set as the electrical tilt angle. Thereby, it is possible to efficiently radiate polarized waves to the base station side. Note that the tilt angle of the radiation pattern can also be changed by changing the mounting angle of the antenna 100 by adjusting the mounting bracket 700 in FIG.

  In FIG. 6, the antenna 100 according to the present embodiment has a cosecant square pattern of the radiation gain attenuation pattern from the horizontal direction to the ground direction (90 to 180 degrees). In this case, the electric field strength is substantially constant with respect to the distance from the antenna 100.

  As described above, in this embodiment, the amplitude and phase shown in FIG. 5 are supplied to the patch antennas 600a to 600m by adjusting the thickness and length of the patterns of the power feeding circuits 540 and 550. In other words, the amplitude of the line target having the maximum value of the central patch antenna g is set, and the amplitude of the electric power to be supplied is reduced as going to the ground direction and the zenith direction. Also, a point-symmetric phase is set around the central patch antenna g, and the phase is advanced toward the zenith and delayed toward the ground. Furthermore, the amount of change in amplitude and phase is increased as going to the ground direction and the zenith direction. By supplying power of the above-described excitation amplitude and phase to the patch antennas 600a to 600m, as shown in FIG. 6, the radiation pattern in which the antenna 100 suppresses the radiation in the sky direction and becomes a cosecant square curve in the ground direction. And an electrical tilt while maintaining a high radiation gain.

  In the present embodiment, the round patch antenna is applied as the antenna element including the radiating elements 300a to 300m and the radiating elements 510a to 510m. However, the present invention is not limited to this. For example, a rectangular patch antenna can be applied, and antenna elements such as a dipole antenna and a slot antenna can also be applied.

  In the present embodiment, the patch antenna is fed from the horizontal direction by the feed circuit 540 and fed from the vertical direction by the feed circuit 550, so that the vertically polarized wave and the horizontally polarized wave are simultaneously radiated or received from the antenna 100. However, it is not limited to this. For example, only one of the power feeding circuit 540 and the power feeding circuit 550 can be used and only one of vertical polarization and horizontal polarization can be handled. Further, by changing the positions of the feeding points 520 and 530, for example, +45 degrees and −45 degrees of polarized waves can be emitted or received. Furthermore, although the antenna 100 according to the present embodiment uses 13 antenna elements, the number of antenna elements is not limited to 13.

(Modification of the second embodiment)
A modification of the second embodiment will be described. In the second embodiment, the center patch antenna 600g is set to the maximum value, the amplitude of the line target that decreases as it goes to the ground direction and the zenith direction is set, and the center patch antenna 600g is set as the center, and the zenith direction is advanced. A point-symmetric phase lagging toward the ground direction was set, and the amount of change in amplitude and phase was increased in the direction toward the ground and the zenith (FIG. 5). Thereby, in the radiation characteristics of the antenna 100, the radiation in the sky direction is suppressed, the radiation pattern has a cosecant square curve in the ground direction, and an electric tilt is maintained while maintaining a high radiation gain (FIG. 6).

  Here, by changing the line pattern of the feeding circuits 540 and 550 of the antenna 100 shown in FIG. 3, the amplitude and phase distribution of the power supplied to the patch antennas 600a to 600m can be changed. By changing the amplitude distribution or / and the phase distribution based on the amplitude / phase distribution shown in FIG. 5, the radiation characteristic of the antenna 100 can be adjusted according to the purpose.

  A case where the amplitude distribution is changed will be described as a first modification. FIG. 7 shows the amplitude / phase distribution according to this embodiment, and FIG. 8 shows the radiation characteristics of the antenna 100 at this time. As shown in FIG. 7, in this embodiment, the patch antennas 600a to 600m described in the second embodiment are supplied with electric power having the same phase distribution as in FIG. 5, and the central patch antenna 600g is set to the maximum value. Power is supplied with an amplitude that decreases at a constant rate as it goes to the ground and zenith directions.

  Comparing FIG. 6 and FIG. 8, by setting the amount of change in the amplitude to a constant value, the suppression of the sky sidelobe level is slightly reduced (up to about 5 dB), while in the foot direction (around θ = 150 degrees). Radiation gain increases. In this case, it is possible to reduce a decrease in electric field strength near the base station.

  Next, a case where the phase distribution is changed will be described as a second modification. FIG. 9 shows the amplitude / phase distribution according to this embodiment, and FIG. 10 shows the radiation characteristics of the antenna 100 at this time. As shown in FIG. 9, in this embodiment, the patch antennas 600a to 600m described in the second embodiment are supplied with electric power having the same amplitude distribution as in FIG. 5, and from the central patch antenna 600g to the zenith direction. The electric power with the phase greatly advanced toward the ground and with the phase slightly delayed toward the ground is supplied. It should be noted that the amount of phase change is increased as it goes to the ground direction and the zenith direction.

  Comparing FIG. 6 and FIG. 10, the phase is greatly advanced toward the zenith direction and the phase is slightly delayed toward the ground direction, so that the radiation characteristics drop between the main lobe and the first side lobe (first 1 null) can be reduced. Since the first null affects the widest range such as a decrease in communication quality at a position farthest from the antenna 100, the decrease in the communication quality can be efficiently improved by reducing the first null.

  Further, in FIG. 9, the phase is greatly advanced from the central patch antenna 600g toward the zenith direction and the phase is slightly delayed toward the ground direction, but the phase is slightly advanced from the central patch antenna 600g toward the zenith direction. However, the first null can also be reduced by greatly delaying the phase toward the ground.

  As a third modification, the amplitude / phase distribution in this case is shown in FIG. 11, and the radiation characteristic of the antenna 100 at this time is shown in FIG. The radiation characteristic of FIG. 12 is the same as that of FIG. That is, the first null can be reduced by supplying the amplitude / phase distribution shown in FIG. 11 to the patch antennas 600a to 600m.

  Furthermore, in FIG. 9 and FIG. 11, the amplitude distribution shown in FIG. 7 can be applied instead of the amplitude distribution shown in FIG. That is, the patch antenna 600a-600m is fed with an amplitude that decreases at a constant rate as it goes in the ground direction and the zenith direction with the central patch antenna 600g as the maximum value. By supplying the patch antennas 600a to 600m with the power having the phase distribution shown in FIG. 9 or FIG. 11 and the amplitude distribution shown in FIG. 7, the first null can be reduced and the radiation gain in the foot direction can be increased. can do.

  Note that the present invention is not limited to the above-described embodiment, and any design change or the like within a range not departing from the gist of the present invention is included in the present invention.

DESCRIPTION OF SYMBOLS 10 Antenna 21, 22, ..., 2n Antenna element 30 Feeding means 100 Antenna 200 Case 300a-300m Radiation element 400a-400m Center pole 500 Printed circuit board 510a-510m Radiation element 520, 530 Feed point 540, 550 Feed circuit 600a-600m Patch antenna 700 Mounting bracket 800 Antenna mounting pole

Claims (10)

A plurality of antenna elements arranged in an array;
Feeding means for feeding the antenna element with an amplitude that decreases as it goes to both ends of the array, and a phase where the advance amount increases as it goes to one end side and the delay amount increases as it goes to the other end side;
With antenna. The antenna according to claim 1, wherein a decrease amount of the amplitude increases toward both ends of the array. The antenna of claim 1, wherein the amplitude decreases at a constant rate. 4. The antenna according to claim 1, wherein a change rate of the phase advance amount is larger than a change rate of the phase delay amount. 5. The antenna according to claim 1, wherein a change rate of the phase delay amount is larger than a change rate of the phase advance amount. The plurality of antenna elements are arranged in an array at equal intervals,
The antenna according to any one of claims 1 to 5, wherein the amplitude and the phase change with reference to an antenna element arranged at the center of the array. The antenna according to claim 1, wherein the antenna element is a patch antenna configured by connecting two opposing radiating elements with a center pole. 8. The power feeding unit according to claim 1, wherein the power feeding unit is a circuit pattern that connects a power feeding point formed on a substrate and the power feeding point and the plurality of antenna elements while branching in a stepped manner. 9. antenna. The antenna according to any one of claims 1 to 8, wherein the plurality of antenna elements and the feeding unit are arranged in a metal casing. A wireless communication apparatus comprising the antenna according to claim 1.

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