JP3822607B2 - Array antenna - Google Patents

Description

  The present invention relates to, for example, an array antenna used in a mobile communication system, and more particularly to an array antenna that controls directivity in a vertical plane.

  2. Description of the Related Art Conventionally, in mobile communication systems such as automobiles and mobile phones, in order to efficiently use radio waves of a limited frequency, the frequency used in one base station is divided into several types of sets, and the sets are adjacent service areas. In order not to use, it combines.

  In addition, since the number of subscribers that can be used in the set of frequencies is limited, in order to cope with the recent increase in subscribers, one service area is reduced, the number of base stations is increased, and the frequency is repeatedly used. This is addressing the increase in the number of subscribers. However, if the service area is reduced, the interval between base stations using the same frequency is reduced, and radio waves from other base stations reach, causing interference.

  Therefore, an antenna used in a base station or the like tilts the maximum radiation direction of the directivity in the vertical plane, that is, tilts, by arranging a plurality of radiating elements vertically and making a linear array and adjusting the phase and amplitude. Therefore, it corresponds to the radio wave interference described above.

Conventionally, as shown in FIG. 5, the radiating elements 14a, 14b, 14c are arranged in a straight line in one subarray block 13a perpendicular to the ground, and the subarray blocks 13a, 13b,. There is a linear array antenna arranged perpendicular to the. This linear array antenna comprises phase shifters 11a, 11b,..., 11h and amplitude control devices 12a, 12b,. The phase and amplitude are adjusted every time (for example, refer to Patent Document 1). Thus, in the conventional array antenna, in order to reduce the number of phase shifters, the phase shifters are arranged outside the subarray block.
JP 2000-349546 A (“0011” paragraph, FIG. 1)

  In the conventional array antenna shown in FIG. 5, when the desired tilt angle is away from the reference tilt angle, the side lobe level increases and the directivity gain decreases. In order to reduce the side lobe level, it is necessary to change the amplitude distribution or reduce the number of radiating elements included in the sub-array block, and finally, it is necessary to change the amplitude and phase for each radiating element. Met.

 However, since the size of the phase shifter is proportional to the size of the phase amount, the phase amount increases as the tilt increases, and the size of the phase shifter increases. For this reason, if a phase shifter is provided for each radiating element, there is a problem that the size of the array antenna increases and is not suitable for practical use.

 In view of the above problems, an object of the present invention is to provide an array antenna capable of reducing the side lobe level and reducing the size without reducing the directivity gain.

  In order to achieve the above object, the present invention is characterized in that N and M are natural numbers, N radiating elements are arranged vertically on a straight line in one subarray block, and M subarray blocks are arranged vertically on a straight line. And (b) a plurality of first phase shifters arranged outside the subarray block and (b) a plurality of second phase shifters arranged inside the subarray block. The gist is that it is an array antenna.

  According to the array antenna according to the feature of the present invention, the first phase shifter and the second phase shifter are provided, and the phase amount is adjusted in two stages. Therefore, the phase amount to be adjusted by each phase shifter is reduced. The first phase shifter and the second phase shifter can be downsized. Also, according to the array antenna according to the feature of the present invention, the side lobe level of the vertical in-plane directivity can be reduced without lowering the directivity gain when the tilt is applied.

  In the array antenna according to the feature of the present invention, the plurality of second phase shifters may change the phase amount of each of the N radiating elements so as to be symmetric at the center in one sub-array block. . According to this array antenna, the phase amount in one sub-array block is distributed in a well-balanced manner, and in particular, the side lobe level of vertical in-plane directivity can be reduced without reducing directivity gain.

  In the array antenna according to the feature of the present invention, the plurality of second phase shifters may all change the same phase amount. According to this array antenna, the movable range of the phase amount in the second phase shifter is reduced, and the second phase shifter can be downsized and the entire array antenna can be downsized.

 According to the present invention, it is possible to provide an array antenna capable of reducing the side lobe level and reducing the size without reducing the directivity gain.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Configuration of array antenna)
In the array antenna according to the present embodiment, N and M are natural numbers, N radiating elements are arranged vertically on a straight line in one subarray block, and M subarray blocks are arranged vertically on a straight line × N elements × This is a linear array antenna of an M subarray block. Each component in the present embodiment can operate in both directions, and can be used as either a transmission antenna or a reception antenna.

  In the array antenna according to the present embodiment, for example, as shown in FIG. 1, the radiating elements 4a, 4b, and 4c are arranged in a straight line in one subarray block 3a and perpendicular to the ground, and the subarray blocks 3a, 3b are arranged. .. 3h are arranged on a straight line perpendicular to the ground. The array antenna includes a plurality of amplitude control devices 2a, 2b,..., 2h, and sub-array blocks 3a, 3b,. A plurality of first phase shifters 1a, 1b,..., 1h arranged on the outside and a plurality of second phase shifters 5a, 5b arranged on the inside of the subarray blocks 3a, 3b,. Prepare. FIG. 1 shows a 24-element array antenna in which three radiating elements are arranged in one sub-array block 3a and eight sub-array blocks are provided.

  The radiating elements 4a, 4b and 4c are arranged at substantially equal intervals and used as antenna elements. As the radiating elements 4a, 4b, and 4c, a dipole antenna or other linear antenna, or a planar antenna such as a patch antenna or a slot antenna can be used.

  The power feeding unit 6 sets the phase difference between the transmission and reception signals of each radiating element corresponding to the beam direction formed by the plurality of radiating elements 4a, 4b, and 4c.

  The amplitude control devices 2a, 2b,..., 2h are arranged for each of the subarray blocks 3a, 3b,..., 3h, and adjust the amplitude of the subarray blocks 3a, 3b,.

  1h is arranged for each of the subarray blocks 3a, 3b,..., 3h, and adjusts the phase of the subarray blocks 3a, 3b,. In the subarray blocks 3a, 3b,..., 3h, the phase amount at the reference tilt angle is set in advance, but when the desired tilt angle (main beam direction) is set, the first phase shifter 1h adjusts the phase of the subarray blocks 3a, 3b,..., 3h.

  The second phase shifters 5a and 5b adjust the phase of the radiating elements 4a and 4c. As shown in FIG. 1, the second phase shifter 5a adjusts the phase of the radiating element 4a, and the second phase shifter 5b adjusts the phase of the radiating element 4c.

  The second phase shifters 5a and 5b change the phase amounts of the radiating elements 4a and 4c so as to be symmetric at the center in one subarray block 3a. For example, in FIG. 1, the radiating element 4a and the radiating element 4c are changed to the same phase amount with the radiating element 4b positioned at the center of the subarray block 3a as the center. When there are an even number of radiating elements in the sub-array block, for example, assuming that there are four radiating elements, the second phase shifter arranged in the first and fourth radiating elements from the top makes them in phase. A second phase shifter disposed on the th and third radiating elements changes them in phase.

  The second phase shifters 5a and 5b may all change the same phase amount. For example, in FIG. 1, the second phase shifter 5a and the second phase shifter 5b change the amount of the same phase with respect to the radiating element 4a and the radiating element 4c.

  The second phase shifters 5a and 5b change the phase amount of each of the radiating elements 4a and 4c so as to be symmetrical at the center in one subarray block 3a, and all change the same phase amount. For this purpose, as shown in FIG. 1, three elements are preferably arranged in one subarray block 3a.

  The second phase shifters 5a and 5b are small in size because the movable range of the phase amount is as small as about ± 20 ° with respect to the element (4b in FIG. 1) located at the center in the subarray block. Become.

(Operation and effect of array antenna according to this embodiment)
According to the array antenna according to the present embodiment, a plurality of first phase shifters 1a, 1b,..., 1h arranged outside the sub-array blocks 3a, 3b,. A plurality of second phase shifters 5a and 5b arranged inside 3h are provided, and the phase amount can be adjusted in two stages. For this reason, the phase amount to be adjusted by each phase shifter becomes small, and the first phase shifters 1a, 1b,..., 1h and the second phase shifters 5a, 5b can be downsized. Further, according to the array antenna according to the present embodiment, when the tilt is applied, the side lobe level of the directivity in the vertical plane can be reduced without reducing the directivity gain. Can be provided.

  Further, the second phase shifters 5a and 5b have a movable range of the phase amount as small as about ± 20 ° with respect to the element (4b in FIG. 1) located at the center in the subarray block, so that the size can be reduced. Even if the second phase shifters 5a and 5b are placed in the sub-array blocks 3a, 3b,..., 3h, the appearance does not increase so much.

  Further, according to the array antenna according to the present embodiment, the plurality of second phase shifters 5a and 5b are configured so that the phase amount of each of the radiating elements 4a, 4b and 4c is within one sub-array block 3a, 3b,. It can be changed so as to be symmetric at the center. For this reason, the phase amount in one subarray block is distributed in a well-balanced manner, and in particular, the sidelobe level of the vertical in-plane directivity can be reduced without reducing the directivity gain.

  Moreover, according to the array antenna according to the present embodiment, the plurality of second phase shifters 5a and 5b can all change the same phase amount. For this reason, the movable range of the phase amount in the second phase shifter is reduced, and the size of the second phase shifter and the size of the entire array antenna can be reduced.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

 For example, in the above-described embodiment, the array antenna of 3 elements × 8 subarray blocks has been described, but it is needless to say that the number of elements and the number of blocks are not limited thereto.

 In FIG. 1, two second phase shifters 5a and 5b are provided in one subarray block, but may be provided for all the radiating elements 4a, 4b and 4c.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

  In order to confirm the effect of the present invention, the vertical in-plane directivity was measured for the array antenna of the example to which the present invention was applied and the array antenna of the conventional example.

  The embodiment is an array antenna of 3 elements × 8 subarray blocks shown in FIG. 1, and includes a first phase shifter arranged outside the subarray block and second antennas arranged for radiating elements at both ends in the subarray block. Phase shifter. On the other hand, the conventional example is an array antenna of 3 elements × 8 subarray blocks shown in FIG. 5 and has the same configuration as that of the example (FIG. 1) except that the second phase shifter is not provided.

  In both the embodiment and the conventional example, the amplitude distribution of the amplitude control device is as follows: amplitude control device 2a, 12a = 0.3, amplitude control device 2b, 12b = 0.5, amplitude control device 2c, 12c = 0.7, amplitude control Device 2d, 12d = 1.0, amplitude control device 2e, 12e = 1.0, amplitude control device 2f, 12f = 0.7, amplitude control device 2g, 12g = 0.5, amplitude control device 2h, 12h = 0 .3.

  FIG. 2 shows the vertical in-plane directivity when the reference tilt angle is 10 ° and the main beam direction is 10 ° in the conventional example. At this time, the phase amount of the first phase shifters 11a, 11b,..., 11h was 0 °.

  FIG. 3 shows the vertical in-plane directivity when the reference tilt angle is 10 ° and the main beam direction is 15 ° in the conventional example. At this time, the phase amount of the first phase shifters 11a, 11b,..., 11h was 5 °.

  FIG. 4 shows the vertical in-plane directivity when the reference tilt angle is 10 ° and the main beam direction is 15 ° in the embodiment. At this time, the phase amount of the first phase shifters 1a, 1b,..., 1h is 5 °, and the phase amount of the second phase shifters 5a, 5b is the central element of the subarray block (4b in FIG. 2). ) To ± 20 °.

(result)
Compared to FIG. 2, FIG. 3 shows that the side lobe level is increased. As described above, in the conventional array antenna, the side lobe level increases when the desired tilt angle is away from the reference tilt angle.

  On the other hand, in FIG. 4, it can be seen that the side lobe level has not increased. As described above, the array antenna according to the embodiment includes the second phase shifter, so that the side lobe level does not increase even when the desired tilt angle is away from the reference tilt angle. The directivity gains in FIGS. 2 and 3 are 14.5 dBi and 14.1 dBi, respectively, and the directivity gain in FIG. 4 is 14.5 dBi. Therefore, the side lobe level is not lowered without reducing the directivity gain. It can be seen that

  Also, the phase difference between the reference tilt angle and the main beam direction (here, 5 °) is adjusted by the first phase shifter, and about ± 20 ° with respect to the central element of the subarray block by the second phase shifter. It can be seen that particularly good results can be obtained when the adjustment is performed.

It is a block diagram of the array antenna according to the embodiment of the present invention. It is a graph which shows the vertical in-plane directivity of a prior art example (the 1). It is a graph which shows the perpendicular in-plane directivity of a prior art example (the 2). It is a graph which shows the vertical in-plane directivity of an Example. It is a block diagram of a conventional array antenna.

Explanation of symbols

1a, 1b, ..., 1h, 11a, 11b, ..., 11h First phase shifters 2a, 2b, ..., 2h, 12a, 12b, ..., 12h Amplitude controllers 3a, 3b, ..., 3h, 13a, 13b , ..., 13h Subarray block 4a, 4b, 4c, 14a, 14b, 14c Radiating element 5a, 5b Second phase shifter

Claims (1)

An array antenna in which N and M are natural numbers, N radiating elements are arranged vertically on a straight line in one sub-array block, and the M sub-array blocks are arranged vertically on a straight line,
A plurality of first phase shifters disposed outside the subarray block;
A plurality of second phase shifters disposed inside the subarray block;
The first phase shifter adjusts a phase difference between a reference tilt angle and a main beam direction,
The array antenna is characterized in that the second phase shifter is arranged in an element other than the central element located at the center in the sub-array block, and adjusts ± 20 ° with respect to the central element .

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