JP4342542B2 - Array antenna and base station - Google Patents

Description

  The present invention relates to an array antenna and a base station.

  In a cellular system, a service area is covered using a plurality of base stations. Further, in a system using FDMA or CDMA, communication with a mobile station is performed by giving different frequencies and codes to adjacent base stations. Each base station creates a communication area called a cell. At this time, if a radio wave is radiated to an adjacent cell, it interferes with the communication channel of the adjacent cell, and the communication capacity of the entire system decreases.

In order to prevent this, the base station uses a phased antenna with an array arranged perpendicular to the ground, and radiates radio waves with the vertical beam narrower toward the cell edge with the main beam direction of the antenna narrow. Suppresses radio waves radiating to the outside. This technique is called beam tilting, and an angle from the horizontal direction to the main beam direction is generally called a tilt angle. FIG. 13 shows the relationship between the beam and the tilt angle. In the phased array antenna, the tilt angle and the side lobe can be changed by changing the values of the phase shifter and the attenuator, and adjustment is performed so as to obtain a desired service area (for example, refer to Patent Document 1). Hereinafter, the amplitude setting given by the control of the attenuator is referred to as amplitude distribution.

  However, if the beam width is narrowed in order to suppress interference with other cells, as the beam width is narrowed, many null points appear in the antenna pattern as shown in FIG. FIG. 15 shows changes in the reception level when such an antenna pattern is used. At this time, when a radio wave arrives from the null direction, there is a problem that the reception level is lowered as indicated by an arrow in FIG.

  In view of the above problems, an object of the present invention is to provide an array antenna and a base station that can prevent a decrease in reception levels of the base station and the mobile station and can maintain a good communication state. .

  In order to achieve the above object, a first feature of the present invention is an array antenna connected to a base station, which controls a specific direction by controlling at least one of the phase and amplitude of the array of the array antenna. The main beam is directed to and reciprocated in the direction perpendicular to the ground on which the base station is installed, so that the null point is reciprocated in the direction perpendicular to the ground on which the base station is installed. The gist of the present invention is an array antenna including a phase amplitude control unit.

  With the array antenna according to the first feature, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  In addition, the phase amplitude control unit of the array antenna according to the first feature uses the phase of each array when the main beam is directed in a specific direction as a reference phase, and changes the phase of all the arrays in the same direction from the reference phase. The main beam direction may be reciprocated by changing so as to reciprocate within a certain range of positive and negative.

  The second feature of the present invention is an array antenna connected to a base station, wherein the antenna pattern has different main beam directions by controlling at least one of the phase and amplitude of the array of the array antenna. A plurality of phase amplitude control units that form a pattern, and a switching device that switches connection between the plurality of phase amplitude control units and the array, each of the phase amplitude control units has a relative relationship in the main beam direction between the antenna patterns. It is an array antenna that reciprocates the null point in a direction perpendicular to the ground where the base station is installed by changing the direction of the main beam without changing and switching the connection of the switching device. And

  According to the array antenna according to the second feature, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  Further, the direction of the main beam may be changed by controlling one phase amplitude control unit among the plurality of phase amplitude control units of the array antenna according to the second feature.

  A third feature of the present invention is an array antenna connected to a base station, and at least one of a phase or amplitude of a baseband signal received by the array antenna array or a baseband signal transmitted from the base station. By controlling either of these, the main beam is directed in a specific direction, and the main beam is reciprocated in a direction perpendicular to the ground on which the base station is installed, so that the ground on which the base station is installed The gist of the present invention is an array antenna including a digital signal processing unit that reciprocally moves the null point in the vertical direction.

  According to the array antenna according to the third feature, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  The array antenna according to the third feature may further include a switching device that switches connection between each array and the digital signal processing unit.

  Moreover, the array antenna according to the first to third features may include a plurality of arrays as one block and a plurality of blocks.

  According to a fourth aspect of the present invention, there is provided a base station including an array antenna, the main beam being directed in a specific direction by controlling at least one of the phase and amplitude of the array of the array antenna, and the main beam. Is provided with a phase amplitude control unit that reciprocates the null point in a direction perpendicular to the ground on which the base station is installed by reciprocating in a direction perpendicular to the ground on which the base station is installed. It is a summary.

  According to the base station according to the fourth feature, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  The base station according to the fourth feature may include a plurality of array antennas.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the reception level of a base station and a mobile station can be prevented, and the array antenna and base station which can maintain a favorable communication state can be provided.

  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.

  In this embodiment, a base station constituting a service area in a mobile communication system will be described. Further, the base station according to the present embodiment includes an array antenna.

(First embodiment)
As shown in FIG. 1, the base station according to the first embodiment is connected to an array antenna 100 including an antenna pattern control unit 10 and an antenna array 20.

  The antenna array 20 is arranged in a direction perpendicular to the ground where the base station is installed. The antenna array 20 includes radiating elements that are arranged at substantially equal intervals and used as antenna elements. As the radiating element, a planar antenna such as a dipole antenna, a linear antenna, a patch antenna, or a slot antenna can be used.

  The control PC 30 is a PC that is connected to a phase amplitude control unit 13 described later and can change the setting of the phase amplitude control unit 13.

  The antenna pattern control unit 10 includes a phase shifter 11, an attenuator 12, a phase amplitude control unit 13, and a power feeding unit 14.

  The phase shifter 11 is arranged for each antenna array 20 and controls the phase of each antenna array 20.

  The attenuator 12 is arranged for each antenna array 20 and controls the amplitude of each antenna array 20.

  The power feeding unit 14 sets the phase difference between the transmission / reception signals of each antenna array 20 corresponding to the beam direction formed by the antenna array 20.

  The phase amplitude control unit 13 controls at least one of the phase and the amplitude of the antenna array 20 by controlling at least one of the phase shifter 11 and the attenuator 12. Then, the phase amplitude control unit 13 directs the main beam in a specific direction, and reciprocates the main beam in a direction perpendicular to the ground where the base station is installed, so that the base station is installed. A null point is reciprocated in a direction perpendicular to the ground.

In FIG. 3, the relationship between the distance between the base station and the mobile station and the reception level when there is no null point control is shown by a solid line. Here, it is assumed that radio waves arrive from the null point direction of the arrow. As described above, when radio waves arrive from the null point direction, the reception level decreases. At this time, if the mobile station continues to be stopped and there is no change in the arrival direction of the radio wave, the reception level is stagnated as shown in FIG.

  In the phase amplitude control unit 13 according to the first embodiment, the main beam is reciprocated in a vertical direction from a specific direction, and the null point is reciprocated in the vertical direction as shown in FIG. When the reception level pattern 1 indicated by the dotted line is reciprocated between the reception level patterns 2 via the pattern without null point control, the reception level changes as shown in FIG. From this figure, comparing the average value of the reception level when the null point is controlled and the average value without the null point control, it is higher when the null point is controlled, and it is compensated for the decrease in the reception level. I understand.

  Next, a method of reciprocating the main beam in the vertical direction and reciprocating the null point in the vertical direction will be described.

  This method can be realized by operating the phase of the array according to a certain law. A specific phase control method will be described below.

  As shown in FIG. 1, consider a case where the array antenna is installed with the array number i = 0 on the lower side and the array number i = n on the upper side. At this time, if the amplitude is set to a certain value, the main beam direction can be directed from the horizontal direction to θ degrees by setting the phase of each array as shown in the following equation. Here, θ represents the tilt angle described above. Also, here, when θ is a positive value, it represents a direction below the horizontal direction.

w (i) = e− ^{j * 2π / λ * di * sinθ} Formula (1)
In equation (1), λ is the wavelength and d is the array spacing. Here, if the phase of each array is controlled so that θ reciprocates up and down, the main beam direction can be operated in the vertical direction, and the null point can be operated in the vertical direction accordingly.

  The main beam may be moved so as to reciprocate within a certain range in the positive and negative directions from the direction in which the main beam is first directed. Further, it may be moved so as to reciprocate within a certain range in the positive direction. On the contrary, it may be moved so as to reciprocate within a certain range in the negative direction. Increasing the amount of rotation of the phase increases the width of movement of the main beam, and accordingly, the width of movement of the null point also increases. Therefore, the amount of rotation may be determined according to the required characteristics. Further, since the speed at which the null point changes depends on the speed at which the phase is rotated, the rotational speed may be determined freely so that the desired speed can be obtained.

  According to the array antenna 100 and the base station according to the first embodiment, by controlling at least one of the phase or amplitude of the array antenna array, the main beam is directed in a specific direction, and the main beam is directed to the base station. By reciprocating in the direction perpendicular to the ground where the station is installed, the null point can be reciprocated in the direction perpendicular to the ground where the base station is installed. For this reason, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  Further, the phase amplitude control unit 13 of the array antenna uses the phase of each array when the main beam is directed in a specific direction as a reference phase, and sets the phase of all the arrays to be constant from the reference phase in the same direction. The main beam direction may be reciprocated by changing so as to reciprocate within the range of.

(Second Embodiment)
As shown in FIG. 5, the base station according to the second embodiment includes a plurality of antenna pattern control units 10a, 10b, and 10c that form different antenna patterns in advance. Since the internal configuration of the antenna pattern control units 10a, 10b, and 10c is the same as that of the first embodiment, the description thereof is omitted here.

  Here, the antenna patterns formed by the antenna pattern control units 10a, 10b, and 10c are set so that the directions of the main beams are different and the null points are different, as in the first embodiment. For example, the antenna pattern corresponding to the antenna pattern control unit 10a is shown as antenna pattern 1 in FIG. 6, the antenna pattern corresponding to the antenna pattern control unit 10b is shown as antenna pattern 2 in FIG. 6, and the antenna pattern corresponding to the antenna pattern control unit 10c is shown in FIG. 6 antenna pattern 3. Here, the antenna pattern of FIG. 6 is obtained by projecting the antenna gain onto the distance assuming a certain tilt angle. At this time, when the antenna pattern control unit is repeatedly switched in the order of 1 → 2 → 3 → 2 → 1 using the switching devices 40 and 50, it is the same as when the null point is controlled as in the first embodiment. Effects can be obtained.

  Here, the patterns of the antenna pattern control units 10a, 10b, and 10c may be set similarly to the first embodiment. For example, the main beam can be directed in a certain direction by controlling the phase of the antenna pattern control unit 10b as shown in Expression (1). The amplitudes of the antenna pattern control unit 10a and the antenna pattern control unit 10c are set to have the same values as those of the antenna pattern control unit 10b. The phase of the antenna pattern control unit 10a is in accordance with the formula (1) so that the direction of the main beam of the antenna pattern control unit 10a is shifted in the negative direction by a certain value from the direction of the main beam formed by the antenna pattern control unit 10b. Set to be adjusted. The phase of the antenna pattern control unit 10c is expressed by the following equation (1) so that the direction of the main beam of the antenna pattern control unit 10c is deviated from the direction of the main beam formed by the antenna pattern control unit 10b by a certain value in the positive direction. Set to adjust according to. If the antenna pattern control unit is switched as described above, the same effect as that of the first embodiment can be obtained. In order to change the null point more continuously, the method of shifting the main beam direction formed by other antenna pattern control units by a certain value from the main beam direction of the antenna pattern control unit 10b is the same. Switching control may be performed by preparing a large number of antenna pattern control units with small deviations. The number of antenna pattern control units may be increased or decreased as necessary. The switching speed may be determined freely according to the required characteristics. The direction in which the upper and lower phases of the antenna pattern control unit 10a and the antenna pattern control unit 10c are shifted may be opposite to the above-described direction.

  There are several other methods for setting the pattern of the antenna pattern control unit. For example, the main beam can be directed in a certain direction by controlling the phase of the antenna pattern control unit 10a as shown in Expression (1). The amplitudes of the antenna pattern control unit 10b and the antenna pattern control unit 10c are set to have the same values as those of the antenna pattern control unit 10a. The phase of the antenna pattern control unit 10b is expressed by the following equation (1) so that the direction of the main beam of the antenna pattern control unit 10b is deviated from the direction of the main beam formed by the antenna pattern control unit 10a by a certain value in the positive direction. To be adjusted according to. The phase of the antenna pattern control unit 10c is expressed by the equation (1) so that the direction of the main beam of the antenna pattern control unit 10c is further deviated by a constant value from the direction of the main beam formed by the antenna pattern control unit 10b. ) To be adjusted according to. When the antenna pattern control unit is switched as described above and the antenna pattern control unit is switched as described above, the effect as in the first embodiment can be obtained. In order to change the null point more continuously, the method of shifting the main beam direction formed by other antenna pattern control units from the main beam direction of the antenna pattern control unit 10a by a constant value is the same, but the main beam direction Switching control may be performed by preparing a large number of antenna pattern control units with small deviations. The number of antenna pattern control units may be increased or decreased as necessary. The switching speed may be determined freely according to the required characteristics. Further, the phase may be adjusted so as to shift from the main beam direction to the negative direction as the process proceeds to the antenna pattern control unit 10b and the antenna pattern control unit 10c according to the required characteristics.

  According to the array antenna 100 and the base station according to the second embodiment, by controlling at least one of the phase or the amplitude of the array antenna array, each antenna pattern has a different main beam direction. A plurality of phase amplitude control units, and a switching device for switching the connection between the plurality of phase amplitude control units and the array. By changing the direction of the beam and switching the switching device, the null point can be reciprocated in a direction perpendicular to the ground where the base station is installed. For this reason, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  Further, the direction of the main beam may be changed by controlling one of the phase amplitude control units 13 of the array antenna.

(Third embodiment)
In the third embodiment, a description will be given of performing processing performed at a radio frequency in the first embodiment in baseband.

  For example, as shown in FIG. 7, a radio frequency signal received by the array 20 of the array antenna is converted into a baseband by the down converter 70 and input to the digital signal processing device 60. The digital signal processing device 60 controls the antenna pattern by controlling the phase of the baseband signal, as in the first embodiment.

  As shown in FIG. 8, the baseband signal processing method is performed by connecting the array antenna array 20 to a switching device 80, sequentially downconverting radio frequency signals, and inputting them to a digital signal processing apparatus. The antenna pattern may be controlled as in the first embodiment by controlling the phase and amplitude of the baseband signal. The switching device 80 is switched at a high speed, and the baseband signal received by the array antenna and down-converted is stored in the digital signal processing device 60, and the phase is controlled, as in the first embodiment. The pattern can be controlled. When transmitting from the array antenna, the same effect can be obtained by switching the switching device 80 at high speed.

  According to the array antenna 100 and the base station according to the third embodiment, the baseband signal received by the array antenna array or the baseband signal transmitted from the base station is controlled at least one of phase and amplitude. By directing the main beam in a specific direction and reciprocating the main beam in a direction perpendicular to the ground on which the base station is installed, the main beam is directed in a direction perpendicular to the ground on which the base station is installed. The null point can be reciprocated. For this reason, it is possible to prevent the reception level of the base station and the mobile station from being lowered, and to maintain a good communication state.

  The array antenna may further include a switching device 80 that switches connection between each array and the digital signal processing unit.

(Fourth embodiment)
As shown in FIG. 9, the first embodiment can also be applied to a system in which a base station includes two antennas in order to perform diversity. Here, first, consider a case where the antenna patterns of the antenna 1 and the antenna 2 are the same, and the phase is adjusted to be the reception level pattern 2 shown in FIG. At this time, as in the first embodiment, the null point is controlled by phase control, and the tilt angle θ is changed in the order of the positive direction, the negative direction, and the positive direction, whereby the reception level of the antenna 1 is changed. Control is performed so that the pattern changes repeatedly in the order of 2 → 1 → 2 → 3 → 2. On the other hand, the reception level pattern of the antenna 2 is controlled to change repeatedly in the order of 2 → 3 → 2 → 1 → 2. Here, it is assumed that each reception level pattern is complemented by a pattern in the middle and continuously connected. By controlling in this way, the reception level changes as shown in FIG. 11, and a decrease in the reception level can be saved compared with the case where there is one antenna.

  There are other ways to change the reception level pattern. For example, assume that the reception level pattern of the antenna 1 is repeatedly moved in the order of 2 → 1 → 2. The reception level pattern is continuously supplemented in the same manner as described above. At this time, when the reception level pattern of the antenna 1 changes to 2, the antenna 2 starts to change in the order of 2 → 1 → 2. By doing so, the above effects can be obtained. Similarly, the same effect can be obtained even if the patterns of the antennas 1 and 2 are changed from 2 → 3 → 2.

  The number of antennas may be three or more. Even at that time, the reception level can be further prevented from lowering by moving the null points of each antenna apart so that they do not synchronize.

(Fifth embodiment)
The method in the case where there are a plurality of array antennas described in the fourth embodiment can be applied to the second embodiment. For example, in the second embodiment, the tilt angle of the antenna pattern control unit 10a is adjusted in the negative direction around the antenna pattern control unit 10b, and the tilt angle of the antenna pattern control unit 10c is adjusted in the positive direction. Think if you are. The antenna pattern control unit 10a of the antenna 1 of FIG. 5 is repeatedly switched in the order of 2 → 1 → 2 → 3 → 2 and the antenna pattern control unit 10b of the antenna 2 is repeatedly switched in the order of 2 → 3 → 2 → 1 → 2. And the same characteristic as the time of using the multiple antenna of 1st Embodiment is acquired. The method for setting each antenna pattern may be performed in the same manner as in the second embodiment.

  In addition, a similar method can be considered when the tilt angle is shifted in the positive direction as the antenna pattern control unit 10a progresses from the antenna pattern control unit 10b to 10c. For example, it is assumed that the antenna pattern control unit 10a is repeatedly switched in the order of 1 → 2 → 3 → 2 → 1. At this time, when the antenna pattern control unit 10a is switched to 3 for the first time, the antenna 2 starts switching in the order of 1 → 2 → 3 → 2 → 1. By doing so, the same effect as described above can be obtained. Here, when the tilt angle is shifted in the negative direction as it proceeds from the antenna pattern control unit 10a to the antenna pattern control units 10b and 10c, a similar switching method can be used.

(Sixth embodiment)
The method in the case where there are a plurality of array antennas described in the fourth embodiment can be applied to the third embodiment. Similar effects can be obtained by controlling the phase of the baseband signal by using the digital signal processing device 60 shown in FIGS. 7 and 8 and controlling the null point as in the fourth embodiment.

(Seventh embodiment)
The methods described in the first, second, fourth, and fifth embodiments can be applied to the case where an array antenna 100 in which a plurality of arrays 20 are formed into blocks 22 is used as shown in FIG. Similar to the first embodiment, this can be realized by controlling the antenna pattern control unit 10.

It is a block diagram of the array antenna according to the first embodiment. It is a figure explaining control of the null point which concerns on 1st Embodiment. It is a figure which shows the relationship between the distance from a base station at the time of performing the null point control which concerns on 1st Embodiment, and a reception level. It is a figure which shows the comparison of the reception level when the null point control which concerns on 1st Embodiment is performed, and the case where it does not perform. It is a block diagram of the array antenna according to the second embodiment. It is a figure which shows the antenna gain corresponding to the antenna pattern control part which concerns on 2nd Embodiment. It is a block diagram of the array antenna according to the third embodiment (No. 1). It is a block diagram of the array antenna according to the third embodiment (No. 2). It is a figure explaining control of the null point concerning a 4th embodiment. It is a figure which shows the relationship between the distance from a base station at the time of performing the null point control which concerns on 4th Embodiment, and a reception level. It is a figure which shows the comparison of the reception level when the null point control which concerns on 4th Embodiment is performed, and the case where it does not perform. It is a block diagram of the array antenna according to the seventh embodiment. It is a figure for demonstrating a tilt angle. It is a figure which shows the relationship between the null point of an antenna, and an incoming wave. It is a figure which shows the relationship between the distance from the base station at the time of performing the conventional null point control, and a reception level.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a, 10b, 10c ... Antenna pattern control part 11 ... Phaser 12 ... Attenuator 13 ... Phase amplitude control part 14 ... Feeding part 20 ... Antenna array 22 ... Block 30 ... Control PC
40, 50, 80 ... switching device 60 ... digital signal processor 70 ... down converter 100 ... array antenna

Claims (1)

A first array antenna having a plurality of first antenna arrays arranged in a vertical direction and a second array antenna having a plurality of second antenna arrays arranged in a vertical direction, and performing diversity wireless communication with a mobile station A base station that
By controlling at least one of the phase or amplitude of the first and second antenna array, a phase amplitude controller for controlling an antenna pattern in which the first and second antenna array are respectively formed,
The phase and amplitude controller, regardless of the position of the mobile station, by reciprocating motion in the first speed of the first main beam of the antenna pattern of the first antenna array is formed in a vertical direction, said first antenna The first null point of the antenna pattern formed by the array is reciprocated in the vertical direction at the first speed,
The phase amplitude controller reciprocally moves the second main beam of the antenna pattern formed by the second antenna array at a second speed in the vertical direction regardless of the position of the mobile station. Reciprocating the second null point of the antenna pattern formed by the array in the vertical direction at the second speed;
When the upper side is the positive direction and the lower side is the negative direction, the phase amplitude control unit changes the tilt angle of the second main beam to the negative direction when changing the tilt angle of the first main beam to the positive direction. And changing the tilt angle of the second main beam in the positive direction when changing the tilt angle of the first main beam in the negative direction.

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