JP2001313525A - Base station antenna for mobile communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station antenna for mobile communication realizing space division multiple access that enhances the separation for users. SOLUTION: In a base station antenna for mobile communication provided with three antenna elements 31 or more, a directivity forming section that applies amplitude and phase weighting to signals of the antenna array and the antenna elements 31 to combine them thereby forming the directivity of the antenna array, a reception power detection section that detects reception power of at least one of the antenna elements 31, and an amplitude phase control section that controls the amplitude and phase weighting of the directivity forming section, the shape of the antenna array is limited so that the arrangement interval of the antenna elements 31 is equal to each other, and the arrangement interval of the antenna elements is decided so that an evaluation function expressing a square integral value of spatial correlation of two waves arriving in two different directions to the antenna array is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station antenna for mobile communication.

[0002]

2. Description of the Related Art In a base station used for mobile communication, the following method has been proposed to enable simultaneous connection of a plurality of users, and has already been introduced in a commercial system. (1) Divide the communication frequency and assign a different frequency to each user (frequency division multiple access: FDMA).

(2) A plurality of time slots are formed by dividing time, and different time slots are assigned to each user (time division multiple access: TDMA). (3) A different code is assigned to each user, and the transmitting side spreads the signal over a relatively wide frequency band using the code, and the receiving side synthesizes the spread signal using the same code as the transmitting side (code division Multiple access: CDMA).

[0004] However, due to the rapid increase in the number of users accompanying the spread of mobile communication in recent years, a call request exceeding the allowable amount of the frequency channel allocated to the mobile communication system has occurred, and problems such as difficulty in making a call have arisen. I have. Therefore, space division multiple access (SDMA) has been proposed in order to further increase the frequency utilization efficiency and achieve an increase in channel capacity. In space division multiple access, the main beam direction of the directivity of the base station antenna is directed toward the desired user, and the null direction is directed toward the other users. That is, a space is divided by the directivity of a base station antenna, and a plurality of users are separated by a difference in space.

In the example shown in FIG. 5, user # 1 and user # 1
2 exist at different positions from each other, so that two types of directivity patterns P1 and P2 are simultaneously formed. That is, in the directivity pattern P1 formed for the user # 1, a main beam is formed in the direction of the user # 1, and a null is formed in the direction of the user # 2. In the directivity pattern P2 formed for the user # 2, a main beam is formed in the direction of the user # 2.
Nulls are formed in the 1 direction. Therefore, the same frequency can be allocated to a plurality of users simultaneously.

When realizing space division multiple access as shown in FIG. 5, a receiving section of a base station is configured as shown in FIG. In FIG. 11, the signals received by each antenna element 51 are converted into baseband signals by frequency converters 52 and input to A / D (analog / digital) converters 53. The A / D converter 53 detects the received power from the input signal. The received power of each of the plurality of antenna elements 51 is input to the directivity control unit 54.

[0007] The directivity control unit 54 determines a weighting factor for the amplitude and phase of each of the plurality of antenna elements 51 and combines the plurality of weighted received signals to generate a desired signal. That is, the directivity control unit 54 determines the directivity pattern of the entire antenna array. In the example of FIG. 11, two independent directivity control units 54 (1) and 54 (2) are provided to simultaneously form different directivities for two independent users # 1 and # 2. .

[0008]

However, when an attempt is made to separate a desired user and an unnecessary user by using the directivity of the antenna as shown in FIG. 5, the actual separation characteristic depends on the arrangement and the interval of the antenna. Depending on conditions, it may not be possible to separate a plurality of users. The case of FIG. 12 will be described as a specific example. The example of FIG. 12 shows a case where the radio wave of the user # 1 arrives at the N-element linear array antenna from the 0 degree direction and the radio wave of the user # 2 arrives at the 30 degree direction. As shown in FIG. 7, when the interval between the antenna elements of the array antenna is 2λ (λ: wavelength), the path difference between the adjacent antenna elements of the wave arriving from the 30-degree direction is exactly 1λ, and thus each antenna The relative phase difference between the signals received by the elements is exactly the same as the wave arriving from the 0 degree direction.

For this reason, in the example of FIG. 12, if the directivity of the antenna is controlled so as to remove the signal of the unnecessary user, the desired signal is also removed at the same time, and the desired user and the unnecessary user can be separated. Can not. As described above,
When realizing space division multiple access, there has been a problem that a plurality of users cannot be separated due to the relationship between the arrangement of antennas and incoming waves.

[0010] It is an object of the present invention to improve the separating capability of a plurality of users in a base station antenna for mobile communication which realizes the space division multiple access as described above.

[0011]

A first aspect of the present invention is an antenna array including a plurality of antenna elements arranged on a straight line, and weighting amplitude and phase for signals of the plurality of antenna elements, respectively. A directivity forming section for performing and combining to form the directivity of the antenna array, a reception power detecting section for detecting at least one reception power of the plurality of antenna elements, and a weighting of an amplitude and a phase of the directivity forming section A base station antenna for mobile communication having an amplitude and phase control unit for controlling the distance between the plurality of antenna elements constituting the antenna array, which is approximately (0.4 + 0.5 (n-1)) times the wavelength used for communication. (N is a natural number).

When two users access the mobile communication base station at the same time, the separation capability of the two users based on the antenna directivity indicates that the two users coming to the mobile communication base station from the two users respectively.
It can be evaluated by the spatial correlation of the waves, and the lower the spatial correlation, the higher the separation ability.

For example, as shown in FIG. 4, in the case of arriving waves r1 and r2 from two users coming from directions of angles θ ₁ and θ ₂ with respect to a linear array antenna having N elements and an element spacing of d, respectively. , The spatial correlation ρ between two arriving waves if the mutual coupling between the elements is ignored is expressed by the following equation. ρ = r1 · r2 ^* = 1 + e ^jd · ^z + e ^j2d · ^z +... + e ^{j (N−1) d} · ^z (1) where z: (sin θ ₁ −sin θ ₂ ) where Assuming that the arrival direction of the arriving wave from the user is spatially uniform, the absolute value of the average spatial correlation ρ _ave of the arriving wave from the two users is expressed by the following equation (2). You.

(Equation 3) It is considered that the separation capability of the two users is maximized when the absolute value of the spatial correlation ρ _ave is minimized.
Here, in order to facilitate the integration of the equation (2), consider the integration of the square of the spatial correlation. That is, since the absolute value of the spatial correlation is a value in the range of 0 to 1, the condition for giving the minimum of the square does not change. Therefore, the mean square spatial correlation f obtained by modifying equation (2) is expressed by the following equation (3).

(Equation 4) The relationship between the spacing d between the antenna elements and the mean square spatial correlation f in the above equation (3) is as shown by a solid line (in the case of two elements) and a dotted line (in the case of four elements) in FIG. Each point in FIG. 3 represents data obtained by computer simulation. In this computer simulation, the mean square spatial correlation f was obtained for uniformly generated users.

Referring to FIG. 3, since the result of the computer simulation and the characteristic of the equation (3) are almost the same,
The validity of equation (3) can be confirmed. As is clear from FIG. 3, the mean square spatial correlation f periodically fluctuates with a change in the spacing d between the antenna elements, and the spacing d has a specific value (0.4).
λ, 0.9λ, 1.4λ, 1.9λ, 2.4λ, 2.9λ,
..) Have the minimum value of the mean square spatial correlation f.

That is, when space division multiplex access is performed, the distance d between antenna elements is set to (0.4 + 0.5) of the wavelength λ.
(N-1)), the ability to separate a plurality of users can be maximized. FIG.
As can be understood from the above, the interval d at which the mean square spatial correlation f becomes the minimum value is not affected by the number of antenna elements of the antenna array, and therefore the interval d can be determined irrespective of the number of elements.

According to a second aspect of the present invention, in the mobile communication base station antenna of the first aspect, an interval between a plurality of antenna elements constituting the antenna array is set to approximately 0.9 of a wavelength used for communication.
It is characterized by doubled. In an actual antenna array, if the distance d between the antenna elements is small (for example, in the case of 0.4 wavelength), mutual coupling between adjacent antenna elements may affect the mean square spatial correlation f. However, the effect of mutual coupling can be neglected at intervals of about 0.9 wavelength, so that the ability to separate a plurality of users can be maximized.

The base station antenna for mobile communication according to claim 3 is:
An antenna array composed of a plurality of antenna elements arranged side by side on a straight line; and a directivity for weighting amplitude and phase with respect to signals of the plurality of antenna elements and combining them to form a directivity of the antenna array Mobile communication base comprising: a directivity forming unit; a received power detecting unit that detects at least one received power of the plurality of antenna elements; and an amplitude / phase control unit that controls weighting of amplitude and phase of the directivity forming unit. In the station antenna, the interval between a plurality of antenna elements constituting the antenna array is set to [(0.4 + 0.5 (n-1)) ± 0.0 of the wavelength used for communication.
5] times (n is a natural number).

Similar to claim 1, but with claim 3, the range of the interval is limited. For example, in FIG. 3, each point (d = 0.4λ, 0.
9λ, 1.4λ, 1.9λ, 2.4λ, 2.9λ, ...)
Focusing on, within the wavelength range of (minimum value ± 0.05), the variation of the value of the mean square spatial correlation f is about 0.01, and within this range, the output SINR (interference signal suppression degree) Does not substantially change and signal quality degradation can be ignored.

According to a fourth aspect of the present invention, in the mobile communication base station antenna according to the third aspect, an interval between a plurality of antenna elements constituting the antenna array is set to (0.9 ± 0.9) of a wavelength used for communication.
0.05) times. It is the same as claim 2, but in claim 4, the range of the interval is limited. For example, in FIG. 3, focusing on the point of (d = 0.9λ), within the range of the wavelength (minimum value ± 0.05), the average is 2
The variation of the value of the power spatial correlation f is about 0.01, and within this range, the output SINR (signal-to-interference-plus-noise ratio) hardly changes, and the degradation of signal quality can be ignored.

According to a fifth aspect of the present invention, an antenna array including three or more antenna elements and a directivity for forming a directivity of the antenna array by weighting amplitude and phase with respect to signals of the antenna elements and combining them. Sex forming part,
A mobile communication base station antenna comprising: a reception power detection unit that detects at least one reception power of the antenna element; and an amplitude / phase control unit that controls weighting of amplitude and phase of the directivity forming unit. Is limited to an arrangement shape in which the arrangement intervals of a plurality of antenna elements are equal, and the evaluation function representing the square integral value of the spatial correlation of two waves arriving from the antenna array in two different directions is minimized. The arrangement interval of the plurality of antenna elements is determined so as to have a value.

When two users access the mobile communication base station at the same time, the separation capability of the two users based on the antenna directivity indicates that the mobile communication base station has two separate users.
It can be evaluated by the spatial correlation of the waves, and the lower the spatial correlation, the higher the separation ability. For example, as shown in FIG.
When the incoming waves x1 and x2 from two users arrive from the directions of the angles θ ₁ and θ ₂ with respect to the array antenna in which each element is arranged at an arbitrary position on the two-dimensional plane, the mutual interference between the elements occurs. If the coupling is ignored, the spatial correlation ρ between the two arriving waves is expressed by the following equation.

(Equation 5) Here, assuming that the arrival directions of the incoming waves from the respective users are spatially uniform, the absolute value of the average spatial correlation ρ _ave of the incoming waves from the two users is calculated by the following (5) It is expressed by an equation.

(Equation 6) It is considered that the separation capability of the two users is maximized when the absolute value of the spatial correlation ρ _ave is minimized.
Here, in order to facilitate the integration of the equation (5), consider the integration of the square of the spatial correlation. That is, since the absolute value of the spatial correlation is a value in the range of 0 to 1, the condition for giving the minimum of the square does not change. Therefore, the mean square spatial correlation f obtained by modifying equation (5) is expressed by the following equation (6).

(Equation 7) Since the mean square spatial correlation f in Equation (6) includes many variables, it cannot be used as it is as an evaluation function. Therefore, the shape of the antenna array is limited to an arrangement shape in which the arrangement intervals of the plurality of antenna elements are equal. This reduces the number of variables in equation (6),
An evaluation function that can be used to evaluate the separation capability of the two users is obtained.

For example, assuming that N antenna elements are arranged at equal intervals on the same circumference with a radius r, the coordinates (x _i , y _i ) of each element on a two-dimensional plane are as follows: No.
It is expressed by equation (7).

(Equation 8) In this case, the above equation (6) can be modified to the following equation (8).

(Equation 9) Since the mean square spatial correlation f in the equation (8) is determined according to the number of elements N, the radius r and the wave number k, it is desirable to evaluate the optimal configuration of the array antenna using the function in the equation (8). Radius r
And the distance between the antenna elements can be determined. Further, for example, assuming that a plurality of antenna elements are arranged at equal intervals on one straight line, the mean square spatial correlation f is expressed by the following equation (9).

(Equation 10) Since the mean square spatial correlation f in the equation (9) is determined according to the number of elements N, the interval d, and the wave number k, the optimal configuration of the array antenna is evaluated using the function in the equation (9). The distance d between the antenna elements can be determined. Claim 6
6. The mobile communication base station antenna according to claim 5, wherein a plurality of antenna elements are arranged at equal intervals on the same circumference, the radius of the circumference is represented by r, and the number of antenna elements of the antenna array is represented by N. , The wave number (2π / λ) is represented by k, and J ₀ is a kind of Bessel function as soon as 0,

[Equation 11] Is adopted as the evaluation function.

By using this evaluation function, it is possible to evaluate an optimum configuration of the array antenna when a plurality of antenna elements are arranged in a circle, and to determine a desirable radius r and an interval between the antenna elements. Claim 7 is Claim 6
In the mobile communication base station antenna, the arrangement interval of the plurality of antenna elements according to the number N of antenna elements and the radius r when the evaluation function is in a range between the minimum value and a value larger than 0.01 by the minimum value. Is determined.

For example, in the case of an array antenna in which three antenna elements are arranged at equal intervals on the same circumference, the relationship between the radius r and the mean square spatial correlation f is as shown in FIGS. . FIG. 10 shows a part of FIG. 9 in an enlarged manner.
Each point in FIGS. 9 and 10 represents data obtained by computer simulation. 9 and FIG.
Is the signal-to-noise-and-interference ratio (2) obtained by applying SDMA when signals from two users arrive uniformly.
(The worse of the users). Further, the output SINR indicates that the cumulative probability of the output SINR obtained by repeating the calculation 1000 times by generating the arrival direction of the user with a uniform probability is 30%.

Referring to FIG. 9, it can be seen that the mean square spatial correlation has a local minimum periodically. Also, SDM
The characteristic of the output SINR when A is applied is as described in the above (10).
It can be seen that the maximum is obtained when the evaluation function of the equation has a radius r at which the minimum value is obtained. Since the plurality of antenna elements are arranged at equal intervals on the circumference, if the radius r is determined, the distance between the antenna elements is also determined. Therefore, by arranging each antenna element at a position determined by the radius r at which the evaluation function of the formula (10) becomes a minimum value, the user separation capability when SDMA is applied can be maximized.

In FIG. 10, the mean square spatial correlation f
When attention is paid to the vicinity of each point where becomes the minimum value, when the mean square spatial correlation f is within the range from the minimum value to the (minimum value +0.01), the deterioration of the output SINR from the maximum value is almost 0.5 dB. It turns out that there is no. Therefore, if the evaluation function adopts a radius r that falls within a range between the minimum value and a value larger than the minimum value by 0.01, the output SINR when SDMA is applied can be maximized, and the signal quality can be reduced. Can be the best.

According to an eighth aspect of the present invention, in the mobile communication base station antenna of the fifth aspect, a plurality of antenna elements are arranged at equal intervals on the same straight line, and an arrangement interval of the plurality of antenna elements is set to d.
, The number of antenna elements is represented by N, and the wave number (2π / λ)
Is represented by k, and J ₀ is a Bessel function as a kind as soon as 0,

(Equation 12) Is adopted as the evaluation function.

By using this evaluation function, it is possible to evaluate the optimum configuration of the array antenna when a plurality of antenna elements are arranged at equal intervals on one straight line, and to determine a desirable distance d between the antenna elements. . Claim 9
In the base station antenna for mobile communication according to claim 8, the arrangement interval d of the plurality of antenna elements is set to [(0.4 + 0.5 (n-1)) ± 0.05] times the wavelength used for communication. Is a natural number).

As is clear from FIG. 3, the mean square spatial correlation f when the antenna elements are arranged at equal intervals on a straight line is
Periodically fluctuates with a change in the distance d between the antenna elements,
The interval d is a specific value (0.4λ, 0.9λ, 1.4λ, 1.9).
λ, 2.4λ, 2.9λ,...) have the minimum mean square spatial correlation f. In addition, the vicinity of the minimum value ±
In the range of 0.05λ, the variation of the mean square spatial correlation f is about 0.01, the output SINR hardly changes, and the deterioration of the signal quality can be ignored.

That is, when performing space division multiplex access, the distance d between antenna elements is set to (0.4 + 0.5) of the wavelength λ.
By setting the value within the range of (n-1)) times ± 0.05, the ability to separate a plurality of users can be maximized. Also, as can be seen from FIG. 3, in the case of a linear array antenna, the interval d at which the mean square spatial correlation f becomes a minimum value is not affected by the number of antenna elements of the antenna array.
The interval d can be determined independently of the number of elements.

A tenth aspect of the present invention is the mobile communication base station antenna according to the eighth aspect, wherein the plurality of antenna elements are arranged at intervals d.
Is set to (0.9 ± 0.05) times the wavelength used for communication (n is a natural number). In an actual antenna array, if the distance d between the antenna elements is small (for example, in the case of 0.4 wavelength), mutual coupling between adjacent antenna elements may affect the mean square spatial correlation f. However, the effect of mutual coupling can be neglected at intervals of about 0.9 wavelength, so that the ability to separate a plurality of users can be maximized.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) One embodiment of a mobile communication base station antenna according to the present invention will be described.
This will be described with reference to FIGS. This form is claimed in claim 1
To claim 5, claim 8 to claim 10.

FIG. 1 is a perspective view showing the configuration of the mobile communication base station antenna of this embodiment. FIG. 2 is a block diagram showing the internal configuration of the base station device. The mobile communication base station antenna shown in FIG. 1 has four antenna elements 31 and a feeder 3.
2, a base station device 33, a support 34, and a base member 35. Of course, the number of antenna elements 31 constituting the antenna array may be changed as needed.

In this example, the four antenna elements 31 supported by the base member 35 are arranged at regular intervals so as to be aligned on one straight line. Further, assuming that space division multiple access is performed, the interval between the antenna elements 31 is set to 0.9λ (λ: wavelength of a signal used for communication) as shown in FIG. As is apparent from the above-mentioned equation (3) and the contents of FIG. 3, a plurality of antenna elements 31
, The antenna element 31
Are set to specific values 0.4λ, 0.9λ, 1.4λ, 1.9.
λ, 2.4λ, 2.9λ,..., the mean square spatial correlation f has a minimum value, so that the ability to separate a plurality of users can be maximized. is there.

However, for example, the interval is set to the minimum of 0.4.
When λ is set, the distance between the adjacent antenna elements 31 is too short, so that the influence of mutual coupling between the adjacent antenna elements 31 appears, and there is a possibility that the mean square spatial correlation f does not actually become a minimum value. is there. When the interval between the antenna elements 31 is set to 0.9λ as shown in FIG. 1, the mutual coupling between the adjacent antenna elements 31 becomes negligibly small, so that the mean square spatial correlation f should be minimized. Can be. The intervals are 1.4λ, 1.9λ, 2.4λ,
The size of the entire antenna can be reduced as compared with the case defined in any of the above.

Each of the four antenna elements 31 is connected to a base station device 33 via a feed line 32. As shown in FIG. 2, an independent receiving circuit and transmitting circuit are provided for each antenna element 31 inside the base station device 33. That is, the circulator 11 is provided in the base station device 33.
(1) to 11 (4), frequency converters 12 (1) to 12 (4), 13
(1) to 13 (4), A / D (analog / digital) converters 14 (1) to 14 (4), D / A (digital / analog) converters 15 (1) to 15 (4), transmission A trust directivity forming unit 16, a receiving directivity forming unit 17, and a directivity control unit 18 are provided.

Radio waves transmitted by each user are received by each of the four antenna elements 31. The reception signal of each antenna element 31 is input to the frequency converter 12 through the circulator 11. The frequency converter 12 converts a radio frequency received signal into a baseband signal.
This baseband signal is converted into a digital signal by the A / D converter 14 and input to the reception directivity forming unit 17.

The reception directivity forming unit 17 is configured to adjust the amplitude and phase of the reception signal input from each antenna element 31 in order to form reception directivity in the antenna array constituted by the four antenna elements 31. , And then combine the signals. In order to enable space division multiple access, when there are a plurality of users, the reception directivity forming unit 17 forms a plurality of types of reception directivities at the same time. Therefore, the signal synthesized according to the directivity is output for each of the plurality of types of reception directivity. That is, the reception signals independent for each user are output from the reception directivity forming unit 17 at the same time.

On the other hand, the signal transmitted by each user is input to the transmission directivity forming unit 16 and distributed to four systems.
Also, in order to form transmission directivity in the antenna array,
The signal output from the transmission directivity forming unit 16 is given a weight corresponding to the user for each system to the amplitude and phase.

The digital signal output from the transmission directivity forming unit 16 is converted into an analog baseband signal by the D / A converter 15 and input to the frequency converter 13. The frequency conversion unit 13 converts the frequency of the input baseband signal into a predetermined radio frequency and amplifies the power. The signal output from the frequency converter 13 is
And is radiated from each antenna element 31 as a radio wave.

The directivity control unit 18 calculates amplitude and phase weighting factors required to form the directivity of each of a plurality of users, and calculates the transmission directivity forming unit 16 for each user.
And the reception directivity forming unit 17. Therefore, the base station antenna for mobile communication shown in FIG. 1 forms a different directivity pattern for each user as shown in FIG. 5, for example, and a plurality of users can be separated by a difference in space.

(Second Embodiment) FIG. 7 shows another embodiment of the base station antenna for mobile communication according to the present invention.
This will be described with reference to FIG. This embodiment corresponds to claims 5 to 7. FIG. 7 is a perspective view showing the configuration of the mobile communication base station antenna of this embodiment. FIG. 8 is a block diagram showing the internal configuration of the base station apparatus of this embodiment.

This embodiment is a modification of the first embodiment. The description of the same parts as those in the first embodiment will be omitted. In this embodiment, the number of antenna elements 31 constituting the antenna array, the spacing between the elements, and the arrangement shape thereof are changed. Although the basic configuration and operation of the base station device 33 are the same as those of the first embodiment,
The number of components is changed as shown in FIG. 8 according to the change in the number of antenna elements 31.

As shown in FIG. 7, the base member 35 has a substantially horizontal triangle shape in a horizontal plane, and the antenna elements 31 are arranged near three tops of the triangle.
Also, three antenna elements 31 (1), 31 (2), 31 (3)
Are equally spaced, and the three antenna elements 31 (1),
31 (2) and 31 (3) are arranged on one circumference. The radius r of the circumference is determined to be 0.5λ (λ: wavelength used for communication).

In the case of an antenna array in which three antenna elements 31 are arranged on the same circumference, the value of the evaluation function (f) expressed by the above-mentioned equation (8) is changed as shown by a dotted line in FIG. Become. That is, when the radius r of the circumference where the three antenna elements 31 are arranged is in the vicinity of 0.2 wavelength, 0.5 wavelength,..., The evaluation function (f) becomes a minimum value. Therefore, FIG.
The radius r is 0.2 wavelength, 0.5 wavelength,...
If the antenna elements 31 are arranged at equal intervals on the circumference while being determined in the vicinity of any one of the above, the average square spatial correlation f becomes a minimum value, so that the ability to separate a plurality of users can be maximized. is there.

However, for example, when the radius r is set to the minimum value of 0.
If the wavelength is set to two wavelengths, the distance between the adjacent antenna elements 31 is too short, so that the influence of mutual coupling between the adjacent antenna elements 31 appears, and the mean square spatial correlation f may not actually be the minimum value. There is also. As shown in FIG. 7, when the antenna elements 31 are arranged on a circumference where the radius r is set to 0.5 wavelength, mutual coupling between the adjacent antenna elements 31 becomes negligibly small. The square spatial correlation f can be minimized. Further, when the radius r is set near 0.5 wavelength, the size of the entire antenna can be made relatively small.

The number of elements (N) of the antenna elements 31 constituting the antenna array may be changed. However, when the number of elements (N) changes, the evaluation function (f) expressed by the equation (8) is changed. Since the radius r at which the minimum value is changed changes, it is necessary to change the radius of the circumference where the antenna elements 31 are arranged. Each of the three antenna elements 31 shown in FIG. 7 is connected to a base station device 33 via a feed line 32.

The directivity control unit 18 of the base station apparatus 33 calculates the amplitude and phase weighting factors required to form the directivity of each of a plurality of users, and calculates the transmission directivity forming unit for each user. 16 and the reception directivity forming unit 17. Therefore, the base station antenna for mobile communication shown in FIG. 7 forms a different directivity pattern for each user as shown in FIG. 5, for example, and a plurality of users can be separated by a difference in space.

[0049]

As described in detail above, according to the present invention,
When performing space division multiple access, it is possible to improve the separation characteristics of a plurality of users. Therefore, the same frequency can be used simultaneously in the same cell, and the frequency utilization efficiency of the mobile communication system can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a mobile communication base station antenna according to a first embodiment.

FIG. 2 is a block diagram illustrating an internal configuration of a base station device according to the first embodiment.

FIG. 3 is a graph illustrating a relationship between an element interval d and a mean square spatial correlation f according to the first embodiment.

FIG. 4 is a plan view showing an example of a configuration of a base station antenna and an arrangement of a plurality of users.

FIG. 5 is a perspective view showing an example of directivity of a base station antenna and arrangement of a plurality of users.

FIG. 6 is a plan view showing an example of a configuration of a base station antenna and an arrangement of a plurality of users.

FIG. 7 is a perspective view illustrating a configuration of a mobile communication base station antenna according to a second embodiment.

FIG. 8 is a block diagram illustrating an internal configuration of a base station device according to the second embodiment.

FIG. 9 is a graph showing a relationship between r, f and output SINR according to the second embodiment.

FIG. 10 is a graph showing a relationship between r, f, and output SINR according to the second embodiment.

FIG. 11 is a block diagram illustrating a configuration example of a receiving unit of a base station that implements space division multiple access.

FIG. 12 is a plan view showing an example of a configuration of a base station antenna and an arrangement of a plurality of users.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Circulator 12, 13 Frequency conversion part 14 A / D conversion part 15 D / A conversion part 16 Directivity forming part for transmission 17 Directivity forming part for reception 18 Directivity control part 31 Antenna element 32 Feeding line 33 Base station device 34 Support 35 Base member 51 Antenna element 52 Frequency converter 53 A / D converter 54 Directivity controller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kentaro Nishimori 2-3-1 Otemachi, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (72) Inventor Toshikazu Hori 2-3-1, Otemachi, Chiyoda-ku, Tokyo No. 1 Nippon Telegraph and Telephone Corporation F-term (reference) 5J021 AA03 AA04 AA05 AA06 CA06 DB02 DB03 EA04 FA14 FA15 FA16 FA17 FA20 FA26 FA29 FA32 FA35 GA02 HA05 HA10 5K067 AA03 CC01 EE10 KK02 KK03 KK17

Claims (10)

[Claims] An antenna array composed of a plurality of antenna elements arranged in a straight line, and weighting of amplitude and phase with respect to signals of the plurality of antenna elements, and combining the signals to obtain a directivity of the antenna array. A directivity forming unit that forms directivity, a received power detecting unit that detects at least one received power of the plurality of antenna elements, and an amplitude and phase control unit that controls weighting of amplitude and phase of the directivity forming unit. In the mobile communication base station antenna provided, the interval between a plurality of antenna elements constituting the antenna array is set to be approximately (0.4 + 0.5 (n−
1) A mobile communication base station antenna characterized in that it is set to be twice (n is a natural number). 2. The mobile communication base station antenna according to claim 1, wherein an interval between a plurality of antenna elements forming said antenna array is set to approximately 0.9 times a wavelength used for communication. Base station antenna. 3. An antenna array composed of a plurality of antenna elements arranged side by side on a straight line, and combining the signals of the plurality of antenna elements by weighting the amplitude and the phase of the signals and combining the signals. A directivity forming unit that forms directivity, a received power detecting unit that detects at least one received power of the plurality of antenna elements, and an amplitude and phase control unit that controls weighting of amplitude and phase of the directivity forming unit. In the mobile communication base station antenna provided, the interval of a plurality of antenna elements constituting the antenna array is [(0.4 + 0.5 (n−
1)) A base station antenna for mobile communication, characterized in that it is set to ± 0.05] times (n is a natural number). 4. The base station antenna for mobile communication according to claim 3, wherein an interval between a plurality of antenna elements constituting said antenna array is (0.9 ± 0.05) of a wavelength used for communication.
A base station antenna for mobile communication, characterized in that the base station antenna is doubled. 5. An antenna array comprising three or more antenna elements, and a directivity forming unit for forming a directivity of the antenna array by weighting amplitude and phase of signals of the antenna elements and combining them. A mobile communication base station antenna comprising: a reception power detection unit that detects at least one reception power of the antenna element; and an amplitude and phase control unit that controls weighting of amplitude and phase of the directivity forming unit. An evaluation function representing a square integral value of a spatial correlation of two waves arriving from two different directions with respect to the antenna array, wherein the shape of the antenna array is limited to an arrangement shape in which an arrangement interval of a plurality of antenna elements is equal. A base station antenna for mobile communication, wherein an arrangement interval of a plurality of antenna elements is determined such that is a minimum value. 6. The base station antenna for mobile communication according to claim 5, wherein a plurality of antenna elements are arranged at equal intervals on the same circumference, a radius of the circumference is represented by r, and an antenna element of the antenna array is provided. The number is represented by N, the wave number (2π / λ) is represented by k,
When J ₀ is a kind of Bessel function as soon as 0, Is adopted as the evaluation function. 7. The mobile communication base station antenna according to claim 6, wherein the number N of antenna elements and the radius r when the evaluation function is within a range between a minimum value thereof and a value larger than the minimum value by 0.01. A base station antenna for mobile communication, wherein an arrangement interval of a plurality of antenna elements is determined according to the following. 8. The mobile communication base station antenna according to claim 5, wherein a plurality of antenna elements are arranged at equal intervals on the same straight line, an arrangement interval of the plurality of antenna elements is represented by d, and the number of antenna elements is N. In the case where the wave number (2π / λ) is represented by k and J ₀ is a kind of Bessel function as soon as 0, Is adopted as the evaluation function. 9. The mobile communication base station antenna according to claim 8, wherein the arrangement interval d of the plurality of antenna elements is [(0.4 + 0.5 (n−1)) ± 0.05] of the wavelength used for communication.
A base station antenna for mobile communication, characterized in that the antenna is set to double (n is a natural number). 10. The mobile communication base station antenna according to claim 8, wherein the arrangement interval d of the plurality of antenna elements is set to (0.9 ± 0.05) times the wavelength used for communication (n is a natural number). A base station antenna for mobile communication.