JP6731148B2 - Antenna device and antenna system - Google Patents

Description

The present invention relates to an antenna device and an antenna system.

Conventionally, in an antenna system used as a mobile phone base station, a plurality of antenna devices are used to cover 360-degree omnidirectional communication. For example, three antenna devices are used to cover communication in an area of 120 degrees with each antenna device (for example, refer to Patent Document 1).

JP-A-11-225105

By the way, for example, when there is a large amount of communication in a certain area, in order to reduce the load on the antenna device corresponding to that area, the area with a large amount of communication is narrowed (the beam width is narrowed down to strong power), and It is desired to spread the load (balance the load) by expanding the area (widening the beam width to reduce the power).

However, in Patent Document 1, since all of the plurality of antenna devices are integrally rotated, the size of the area cannot be changed. It is also possible to individually rotate each antenna device and individually adjust the direction of the antenna device, but if the antenna device is rotated without changing the size of the area, the interference with the adjacent antenna devices is large. turn into.

Therefore, it is an object of the present invention to provide an antenna device and an antenna system having a variable cover area and capable of suppressing interference with an adjacent antenna device.

The present invention, for the purpose of solving the above problems, includes a plurality of antenna elements aligned in the horizontal direction, and a radio unit to which baseband signals of a plurality of systems are input, the radio unit is a base. For each band signal system and for each antenna element, a storage unit for storing a weight matrix in which a weighting coefficient for adjusting the phase and amplitude is set is provided, and the weight matrix is multiplied to the base band signal of each system. The antenna unit is also configured to generate a transmission signal to be transmitted from each of the antenna elements, and the radio unit is configured to be able to change the weight matrix to be applied.

In addition, the present invention is provided with a plurality of the antenna devices for the purpose of solving the above problems, monitors the communication amount of each of the antenna devices, and based on the communication amount, the wireless unit for each of the antenna devices. An antenna system is provided, which comprises a controller for determining the weight matrix to be applied.

According to the present invention, it is possible to provide an antenna device and an antenna system having a variable cover area and capable of suppressing interference with an adjacent antenna device.

FIG. 1A is a schematic configuration diagram of an antenna device according to an embodiment of the present invention, and FIG. 1B is a schematic configuration diagram of an antenna system using the antenna device. It is a figure explaining that a beam pattern is variable in the antenna device of Drawing 1 (a). It is a graph which shows an example of the radiation characteristic of the antenna device of FIG. (A) is a schematic block diagram of the antenna device which concerns on the modification of this invention, (b) is a graph which shows an example of the radiation characteristic. It is a graph which shows an example of a radiation characteristic when the number of antenna elements is 6 and a distributor is omitted. (A) is a schematic block diagram of the antenna device which concerns on the modification of this invention, (b) is a graph which shows an example of the radiation characteristic. (A) is a schematic block diagram of the antenna device which concerns on the modification of this invention, (b) is a graph which shows an example of the radiation characteristic.

[Embodiment]
Embodiments of the present invention will be described below with reference to the accompanying drawings.

1A is a schematic configuration diagram of an antenna device according to the present embodiment, and FIG. 1B is a schematic configuration diagram of an antenna system using the antenna device.

As shown in FIG. 1A, the antenna device 1 includes a plurality of antenna elements 2, a radio unit (RE) 3, and a radio control unit (REC) 4 that controls the radio unit 3.

The plurality of antenna elements 2 are arranged in a straight line in the horizontal direction. As the antenna element 2, for example, a dipole antenna can be used. Further, the antenna element 2 may be an array having a plurality of radiators. That is, the plurality of antenna elements arranged in an array may be treated as one antenna element 2.

Further, the plurality of antenna elements 2 are arranged at equal intervals. The interval between the antenna elements 2 is preferably about 0.5 times the signal wavelength λ transmitted and received via the antenna elements 2. More specifically, the interval between the antenna elements 2 is preferably 0.4 times or more and 0.6 times or less the signal wavelength λ transmitted/received via the antenna elements 2. By setting the spacing between the antenna elements 2 to be about 0.5λ, it is possible to suppress unnecessary side lobes and suppress interference between the antenna devices 1 whose cover areas are adjacent to each other. In the present embodiment, the four antenna elements 2a to 2d are sequentially arranged at intervals of 0.5λ.

The radio controller 4 has a modulator/demodulator 41 that generates baseband signals D1 to D4 from transmitted and received data and signals and obtains data and signals from the received baseband signals D1 to D4. The modulation/demodulation unit 41 generates baseband signals D1 to D4 of a plurality of systems (here, four systems), and outputs the generated baseband signals D1 to D4 to the wireless unit 3 via an optical fiber or the like. The modulation method in the modulation/demodulation unit 41 is not particularly limited, but for example, a phase shift keying method such as QPSK (quadrature phase shift keying) can be used. Further, each of the baseband signals D1 to D4 may be transmitted using a plurality of optical fibers, or the baseband signals D1 to D4 may be multiplexed and transmitted by one optical fiber.

The wireless unit 3 includes a weight calculation unit 5, a storage unit 6, and an amplification/frequency conversion unit (RF) 7.

The storage unit 6 is composed of a memory such as a RAM or a ROM. The storage unit 6 stores a weight matrix in which weight coefficients for adjusting the phase and the amplitude are set for each system of the baseband signals D1 to D4 and for each antenna element 2. In the present embodiment, since the number of systems of baseband signals D1 to D4 is 4 and the number of antenna elements 2 is 4, the weight matrix is represented by a matrix of 16 weighting coefficients in 4 rows and 4 columns. It

The weight calculation unit 5 multiplies the weight matrix stored in the storage unit 6 by the baseband signals D1 to D4 of each system and sends the result to the amplification/frequency conversion unit 7 corresponding to each of the antenna elements 2a to 2d. These generate the transmission signals P1 to P4 to be transmitted from the antenna elements 2a to 2d by the formula (1) shown in [Equation 1]. When the transmission signals P1 to P4 are input to the antenna elements 2a to 2d, the signals corresponding to the baseband signals D1 to D4 are output in the beam patterns shown by the symbols A1 to A4 in FIG. 1A, respectively.

W11 to W44 in the equation (1) are weighting factors and are represented by complex numbers including phase information. The weighting factor is represented as, for example, A·e ^jθ . A is a coefficient that determines the magnitude of the amplitude of the transmission signals P1 to P4, and θ is the phase. By appropriately setting the weighting factors W11 to W44 of the weighting matrix, it is possible to adjust the direction in which each of the transmission signals P1 to P4 is transmitted and the beam width (that is, adjust the beam pattern of each system). .. That is, the antenna device 1 is a multi-beam antenna device that operates as if there are four sectors in its coverage area.

In the antenna device 1 according to this embodiment, the radio unit 3 is configured to be able to change the weight matrix to be applied. Specifically, in the antenna device 1, the storage unit 6 stores a plurality of weight matrices in which different weight coefficients are set, and the weight calculation unit 5 of the wireless unit 3 can select a weight matrix to apply. Is configured. The weight matrix can be rewritten or selected from the wireless control unit 4 side by the control information signal.

In this embodiment, the wireless unit 3 is configured to store a plurality of weight matrices in the storage unit 6 and select which weight matrix to apply, but the present invention is not limited to this, and the storage unit 6 is not limited thereto. It is also possible to store only one weight matrix in, and to rewrite the weight matrix each time the wireless control unit 4 side changes the weight matrix.

The weight calculation unit 5 determines a weight matrix to be applied based on a control information signal input from the control device 11 of the antenna system 10 described later via the wireless control unit 4 to the wireless unit 3. As a method of the control information signal, for example, CPRI (Common Public Radio Interface) can be used.

As described above, by appropriately setting the weighting factors W11 to W44 of the weighting matrix, the beam pattern of each system is determined. Therefore, it is possible to switch the beam pattern by pre-storing a plurality of weighting matrices having different weighting factors and appropriately selecting the weighting matrix to be multiplied by the baseband signals D1 to D4 in the weighting calculation section 5. ..

As a result, for example, as shown in FIG. 2, the width of the beam pattern of each system is narrowed and the direction of the beam pattern of each system is brought close to each other, whereby the coverage area of the antenna device 1 can be narrowed. Although not shown, it is also possible to expand the coverage area of the antenna device 1 by expanding the width of the beam patterns of each system and separating the directions of the beam patterns of each system. Furthermore, it is possible to change the direction of the cover area by changing the direction of the beam pattern of each system.

That is, by selecting the weight matrix to be applied by the weight calculator 5, it is possible to switch to the optimum beam pattern according to the communication status. In FIGS. 1A and 2, the beam patterns corresponding to the respective systems of the baseband signals D1 to D4 are indicated by broken lines (reference symbols A1 to A4), respectively.

In addition, the weight calculation unit 5 generates baseband signals D1 to D4 by multiplying the signals received by the antenna elements 2a to 2d by the inverse matrix of the weight matrix stored in the storage unit 6.

As shown in FIG. 1B, the antenna system 10 includes a plurality of antenna devices 1 according to this embodiment and a control device 11 that controls the antenna device 1.

In the present embodiment, the antenna system 10 includes three antenna devices 1. In the antenna system 10, when the communication load is low, the coverage area of each antenna device 1 is set to about 120 degrees, and the three antenna devices 1 are configured to cover 360-degree omnidirectional communication. There is. Note that in FIG. 1B, the cover area of each antenna device 1 is indicated by a dashed line.

The control device 11 uses the communication amount monitoring unit 11a that monitors the communication amount of each antenna device 1 and the wireless unit 3 for each antenna device 1 based on the communication amount of each antenna device 1 that is monitored by the communication amount monitoring unit 11a. And a weight matrix determination unit 11b that determines the weight matrix to be applied in step 1.

The weight matrix determination unit 11b switches the weight matrix so as to reduce the coverage area in the antenna device 1 when the communication amount in one antenna device 1 exceeds a specified amount, and other The antenna device 1 switches the weight matrix so as to expand the coverage area. As a result, the beam width is narrowed in the area where the communication load is large (to make the power high), and the beam width is widened in the area where the communication load is small (to make the power weak) to reduce the communication load (number of users) per area. It is possible to equalize and distribute the load.

Next, when the number of transmission/reception systems is 4, the optimum number of antenna elements 2 in the antenna device 1 will be examined.

The radiation characteristic of the antenna device 1 of FIG. 1A having four antenna elements 2 is as shown in FIG. As shown in FIG. 3, when the number of elements of the antenna element 2 is four, which is the same as the number of transmission/reception systems, the weight matrix is appropriately set so that the crossover between adjacent beams is about 3 dB and the side lobe is about It can be about 13 dB.

The weight matrix (weight coefficients W11 to W44) is calculated by an appropriate method so that the crossover and side lobes with adjacent beams are reduced. As a result of studies by the present inventors, it was found that when the weight matrix is adjusted to reduce the side lobes, the beam width tends to widen and the crossover tends to increase.

The antenna device 1a shown in FIG. 4A has six antenna elements 2a to 2f arranged in a horizontal direction at intervals of 0.5λ. In the antenna device 1a, the number of antenna elements 2 is larger than the number of systems for transmission/reception. Therefore, two dividers 8 are used, the transmission signal P1 is divided into two, and the transmission signal P2 is divided into two into antenna elements 2a and 2e. To transmit to the antenna elements 2b and 2f, respectively.

The radiation characteristic of the antenna device 1a using the six antenna elements 2a to 2f is as shown in FIG. As shown in FIG. 4B, it can be seen that in the antenna device 1a, the crossover and the side lobe can be reduced as compared with the antenna device 1 using four antenna elements 2.

Although the case where the two distributors 8 are used has been described here, the distributor 8 can be omitted. For example, when the antenna device 1 is used not only in the multi-beam function but also in another transmission mode, the transmission signals P1 to P6 whose amplitude and phase are adjusted for each antenna element 2 are transmitted without using the distributor 8. The wireless unit 3 may be configured to do so. In this case, a weight matrix using 24 weight coefficients in 6 rows and 4 columns is used.

However, when the distributor 8 is omitted, the configuration of the wireless unit 3 becomes complicated as the number of transmission signals P1 to P6 increases, which causes an increase in cost. By using the distributor 8, the antenna device 1a can be realized with a simpler configuration, which contributes to cost reduction.

Here, FIG. 5 shows an example of radiation characteristics when transmitting the transmission signals P1 to P6 to the antenna elements 2a to 2f without using the distributor 8. As can be seen by comparing FIG. 5 and FIG. 4B, by appropriately setting the weight matrix, substantially the same crossover and sidelobe characteristics can be obtained regardless of whether or not the distributor 8 is used.

The antenna device 1b shown in FIG. 6(a) has seven antenna elements 2a to 2g arranged in the horizontal direction at intervals of 0.5λ. In the antenna device 1b, three distributors 8 are used, the transmission signal P1 is divided into two, the transmission signals P2 are divided into two, the transmission signals P2 are divided into two antenna elements 2a and 2e, and the transmission signal P3 is divided into two. The antenna elements 2c and 2g are respectively transmitted.

The radiation characteristic of the antenna device 1b using the seven antenna elements 2a to 2g is as shown in FIG. 6(b). As shown in FIG. 6B, it can be seen that in the antenna device 1b, the crossover can be further reduced and the side lobe can be made smaller than the antenna device 1a using the six antenna elements 2. Further, in the antenna device 1b, side lobes outside the range of 120 degrees, which is the cover area, are reduced as compared with the above-described antenna devices 1 and 1a.

The antenna device 1c shown in FIG. 7A has eight antenna elements 2a to 2h arranged in a horizontal direction at intervals of 0.5λ. In the antenna device 1c, four distributors 8 are used, the transmission signal P1 is divided into two, the transmission signal P2 is divided into two, the transmission signal P2 is divided into two antenna elements 2a and 2e, and the transmission signal P3 is divided into two. The transmission signal P4 is divided into two by the antenna elements 2c and 2g and transmitted to the antenna elements 2d and 2h, respectively.

The radiation characteristic of the antenna device 1c using the eight antenna elements 2a to 2h is as shown in FIG. As shown in FIG. 7B, it can be seen that in the antenna device 1c, the crossover can be further reduced and the side lobe can be made smaller than the antenna device 1b using seven antenna elements 2. Further, in the antenna device 1c, as in the antenna device 1b using the seven antenna elements 2a to 2g, side lobes outside the range of 120 degrees serving as the cover area are reduced as compared with the antenna devices 1 and 1a. ing.

From the above results, it is possible to lower the crossover and reduce the side lobes as the number of antenna elements 2 increases. Further, by setting the number of antenna elements 2 to 7 or more, it is possible to reduce the side lobe outside the range of 120 degrees, which is the cover area. Therefore, when transmitting/receiving four-system signals (when four-system baseband signals D1 to D4 are input to the radio unit 3), seven or more antenna elements arranged in the horizontal direction at intervals of 0.5λ. It can be said that having 2 is more desirable.

Further, although polarization has not been mentioned in the above description, generally, two orthogonal polarizations are often used when covering a certain area, and are used for diversity and data multiplexing. Although the present embodiment has been described as one polarization, it may be extended to two orthogonal polarizations.

(Operation and Effect of Embodiment)
As described above, in the antenna device 1 according to the present embodiment, the plurality of antenna elements 2 arranged in the horizontal direction and the radio unit 3 to which the baseband signals D1 to D4 of the plurality of systems are input are provided. The radio unit 3 includes a storage unit 6 that stores a weight matrix in which weighting factors for adjusting the phase and the amplitude are set for each baseband signal system and each antenna element 2, and the weighting matrix is stored in the storage unit 6. It is configured to generate the transmission signals P1 to P4 to be transmitted from each antenna element 2 by multiplying the baseband signals D1 to D4 of each system, and the radio unit 3 is configured to change the weight matrix to be applied. ing.

By making it possible to change the weight matrix applied in the radio unit 3, it is possible to adjust the beam pattern (beam width and direction) of each system and change the coverage area in the antenna device 1. Also, by adjusting the beam pattern (beam width or direction) of each system, it is possible to adjust the interference area between adjacent beams or the interference area between adjacent areas. Therefore, according to the antenna device 1, when the antenna system 10 is configured by using the plurality of antenna devices 1, it is possible to suppress the interference with the adjacent antenna devices 1.

Further, in the present embodiment, the interval between the antenna elements 2 is set to about 0.5 times (0.4 times or more and 0.6 times or less) the signal wavelength λ transmitted/received via the antenna elements 2, and therefore unnecessary. It becomes possible to suppress the side lobes and further suppress the interference between the antenna devices 1 whose cover areas are adjacent to each other.

Further, in the case where four systems of baseband signals D1 to D4 are input to the wireless unit 3, by having seven or more antenna elements 2 arranged in the horizontal direction at intervals of 0.5λ, adjacent beams It is possible to reduce the crossover and side lobes with respect to each other and to reduce the side lobes outside the range of 120 degrees, and particularly to realize the antenna device 1 (1b, 1c) suitable for the antenna system 10 in which the cover area is divided into three. Also, by reducing the crossover and side lobes, it is possible to reduce the interference noise during communication. For example, by using 16QAM or 256QAM as the modulation method, the transmission speed can be improved compared to QPSK. It is also possible to plan.

Furthermore, since the wireless unit 3 includes the distributor 8 that distributes the transmission signal to the two or more antenna elements 2, the configuration of the wireless unit 3 is simplified and the cost of the antenna device 1 (1a to 1c) is reduced. Contribute to.

(Summary of Embodiments)
Next, the technical idea grasped from the embodiment described above will be described with reference to the reference numerals and the like in the embodiment. However, the reference numerals and the like in the following description are not intended to limit the constituent elements in the claims to the members and the like specifically shown in the embodiments.

[1] A plurality of antenna elements (2) aligned in the horizontal direction and a radio unit (3) to which baseband signals of a plurality of systems are input are provided, and the radio unit (3) is a baseband signal. For each system and for each antenna element 2, a storage unit (6) for storing a weight matrix in which a weighting coefficient for adjusting a phase and an amplitude is set is provided, and the weight matrix is used as a baseband signal of each system. The antenna unit (1) is configured to generate a transmission signal to be transmitted from each of the antenna elements 2 by multiplying with the antenna unit, and the radio unit (3) is configured to be able to change the weight matrix to be applied. ).

[2] The storage unit (6) stores a plurality of the weight matrices to which different weight coefficients are set, and the wireless unit (3) is configured to be able to select the weight matrix to be applied. The antenna device (1) according to [1].

[3] The antenna device (1) according to [1] or [2], wherein the wireless unit (3) is configured to be able to rewrite the weight matrix by an external signal.

[4] Any of [1] to [3], wherein the distance between the antenna elements (2) is 0.4 times or more and 0.6 times or less of the signal wavelength λ transmitted/received via the antenna elements (2). An antenna device (1) according to item 1.

[5] The base unit signals of four systems are input to the radio section (3), and the radio section (3) has seven or more antenna elements (2) arranged in the horizontal direction at intervals of 0.5λ. , The antenna device (1b, 1c) according to any one of [1] to [4].

[6] The radio unit (3) according to any one of [1] to [5], including a distributor (8) that distributes a transmission signal to two or more antenna elements (2). Antenna device (1a-1c).

[7] A plurality of antenna devices (1) according to any one of [1] to [6] are provided, the communication amount of each antenna device (1) is monitored, and the antenna is based on the communication amount. An antenna system (10) comprising a control device (11) for determining the weight matrix to be applied by the radio unit (3) for each device (1).

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. Further, it should be noted that not all combinations of the features described in the embodiments are essential to the means for solving the problems of the invention.

The present invention can be appropriately modified and implemented without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1... Antenna device 2... Antenna element 3... Radio part 4... Radio control part 5... Weight calculation part 6... Storage part 7... Amplification/frequency conversion part 8... Distributor 10... Antenna system 11... Control device 11a... Communication amount monitoring Unit 11b... Weight matrix determining unit

Claims (6)

A plurality of antenna elements arranged in a horizontal direction,
A radio unit to which baseband signals of a plurality of systems are input,
The radio unit has a storage unit that stores a weight matrix in which a weight coefficient for adjusting a phase and an amplitude is set for each system of baseband signals and for each antenna element, and the weight matrix is provided for each system. Is configured to generate a transmission signal to be transmitted from each of the antenna elements by multiplying the baseband signal of
The radio unit is configured to be able to change the weight matrix to be applied , and has a distributor that distributes a transmission signal to two or more antenna elements.
Antenna device. The storage unit stores a plurality of the weight matrices to which different weight coefficients are set,
The wireless unit is configured to be able to select the weight matrix to be applied,
The antenna device according to claim 1. The wireless unit is configured to be able to rewrite the weight matrix with an external signal,
The antenna device according to claim 1 or 2. An interval between the antenna elements is 0.4 times or more and 0.6 times or less of a signal wavelength λ transmitted/received through the antenna elements,
The antenna device according to any one of claims 1 to 3. Baseband signals of four systems are input to the wireless unit,
Having seven or more antenna elements arranged in a horizontal direction at 0.5λ intervals,
The antenna device according to any one of claims 1 to 4. A plurality of antenna devices according to any one of claims 1 to 5 are provided, and
A control device is provided, which monitors the communication amount of each of the antenna devices, and determines the weight matrix to be applied to the radio unit for each antenna device based on the communication amount.
Antenna system.

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