JPH10242739A - Base station antenna system for mobile communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease number of antenna elements in the case of realizing a pencil beam through the use of an array configuration to prevent interference of a delay wave. SOLUTION: The system is configured to emit a strip shaped area. In this case, an amplitude phase variable device 1-3 is provided to each antenna input section, each antenna element is connected to each device 1-3 linearly orthogonal to the lengthwise direction of the strip area, the number of the antenna elements is selected to be 2 or over and 5 or below, an interval between the elements is selected to be 1 wavelength or over and 3 wavelength bands or below, and an amplitude and a phase of an input signal from each element are changed. Furthermore, an amplitude phase calculation section 1-4 is provided to calculate the amplitude and the phase of an input signal from each element so that an error between a known signal at the receiver side and a combined signal of signals received by the antenna elements is minimized. Each amplitude phase variable device 1-3 is adjusted so that the amplitude and the phase of each element obtained by the amplitude phase calculation section 1-4 is an output of the amplitude phase variable devices 1-3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device for a base station in a street microcell mobile communication, and more particularly to an antenna device which is electrically controlled to have a sharp directional characteristic and suppress a long delay wave. The present invention relates to an antenna device having a simple configuration that can be used.

[0002]

2. Description of the Related Art In micro-cell mobile communication, a base station is installed in a place having a relatively low antenna height, such as a telephone booth or the roof of a building. In such a case, especially in an urban area, the cell shape is a shape generally called a street cell along a road as shown in FIG. In FIG.
1 indicates a base station (CS), 8-2 indicates a cell, and 8-3 indicates a road. (Literature: Kozono, et.al., IEEE Trans.VT-42,
no.1, pp.103-109).

On the other hand, with the recent spread of computers,
The characteristics of signals transmitted by mobile communication have also changed from conventional voice signal centers to data transmission. Accordingly, high reliability of transmission quality and high transmission speed have been demanded in mobile communication.

In order to increase the speed of signal transmission in mobile communication, it is a major problem that a wave having a long delay time arrives due to multiple reflections on a propagation path. The transmission quality greatly depends on the delay time of the multiplex propagation path with respect to the signal transmission speed. In order to increase the speed of a transmission line for multimedia communication in the future, it is necessary to suppress delayed waves in a propagation path.

[0005] A delayed wave in a street cell arrives as reflected or scattered from a building standing along the street. FIG.
Fig. 7 shows an example of the result of measuring the arrival characteristics of a delayed wave in a street cell. In the figure, numeral 9-1 is a base station,
9-2 is a terminal, 9-3 is a building, 9-4 is a road, 9-5.
Represents the required directivity. This example is a measurement result on a base station sidewalk at a point 150 m away from the base station. As is clear from FIG. 9, the incoming wave having a particularly long delay time comes from a direction along the road.

Considering the cause of the generation of such a long delay wave from the viewpoint of the delay time and the arrangement of buildings and the like, as shown in FIG. The light is scattered and arrives at the base station (reference: chief, see IEICE 1996 Society Conference B-22).

As a method for removing such a delayed wave,
A method using a directional antenna can be considered. in this case,
As shown in FIG. 10, it is necessary to direct the main beam of the directional antenna toward the terminal and directivity null in the direction of the delay wave. In the figure, numeral 10-1 is a base station, 1
0-2 is a terminal, 10-3 is a building, 10-4 is a zone,
10-5 indicates a main beam, and 10-6 indicates a beam.

[0008] The signal strength (SNR) against noise in normal mobile communication is evaluated at 12 dB (refer to the literature: IEICE, edited by the Institute of Electronics, Information and Communication Engineers: Basics of Mobile Communication, p105), and has a particularly long delay time other than the desired wave If the level of the wave is to be suppressed to at least 12 dB or less with respect to the desired wave, the directivity gain in the facing direction of the base station becomes −12 dB with respect to the desired wave direction.
B or less.

The worst condition in which the level of the desired wave becomes the weakest is when the terminal is located at the end of the zone, and the road width in a general urban area is about 15 to 50 m. The size is 100m-3
Considering that the distance is about 00 m, the angle α from the base station to the facing zone end is about 8 degrees.

Further, for a delayed wave having a long delay time shown in FIG. 9 (a wave arriving after arriving on the opposite side to the base station), the angle α becomes smaller, but the free space depends on the propagation distance. Since the propagation loss increases, the relationship between the free space propagation loss and the arrival angle α of the arriving wave with a long delay time as viewed from the base station is illustrated in FIG. 11, where the loss increases as the angle α decreases.

Here, the propagation loss in FIG. 11 is based on the propagation loss of the wave arriving from the facing zone end (point A in FIG. 10). Therefore, considering this loss, the beam shape for irradiating the terminal direction is approximated by a function of cos ⁿ α, and when α = 0 degree direction is the terminal direction (desired wave), the arrival direction of the delayed wave having a long delay time In order to make the directivity gain of -12 dB or less, a pencil beam (n = 168) having a directivity gain in the 8-degree direction of -15 dB or less is required as shown in FIG.

Further, since the position of the terminal always moves, a function is required that can change the directivity according to the movement of the terminal. One method of realizing the variable directivity function is to mechanically change the directional antenna. However, a microcell system usually uses a frequency multiplexing or time division multiplexing method to realize a system that allows simultaneous communication with multiple terminals, so if a mechanically variable structure is used, directivity is always radiated in the direction of the terminal. To do this, you must rotate the antenna very quickly.

Therefore, it is difficult to introduce such an antenna into a base station antenna using a multiplexing system. As another method of changing the directivity, there is a method in which a plurality of antennas are configured in an array and the amplitude and phase of each antenna are electrically controlled. With this method, the directivity can be electrically changed instantaneously.

[0014]

As a method of realizing the pencil beam as described above using an array configuration, a method of arranging omnidirectional antennas at half-wavelength intervals has been generally used. FIG. 13 shows the relationship between the number of elements and the angle α between the main beam and the direction in which the directional gain drops from the main beam by 15 dB when the omnidirectional antennas are arranged on a straight line at half-wavelength intervals and excited in phase. Angle α from FIG.
It is understood that the number of antenna elements needs to be about 12 in order for the angle to be 8 degrees.

As described above, when 12 antenna elements are used, if an amplitude / phase control unit is prepared for each element,
There was a problem that the hardware was very large and complicated. SUMMARY OF THE INVENTION An object of the present invention is to reduce the hardware scale as much as possible and to simplify the case where the above-described pencil beam is realized using an array configuration.

[0016]

According to the invention, the above-mentioned object is solved by the means described in the claims.

That is, the invention of claim 1 is a base station antenna apparatus for mobile communication which irradiates a band-like area,
The antenna elements are arranged in a linear shape orthogonal to the longitudinal direction of the band-shaped region, have a number of elements of 2 to 5 elements, an interval between each element is 1 to 3 wavelengths, Having an amplitude and phase variable device capable of changing the amplitude and phase of the input signal of each of the antenna input units,

The receiving side has an amplitude / phase calculator for calculating the amplitude and phase of each antenna input signal so as to minimize the error between the signal known in advance and the composite signal of the signal received by each antenna element. A mobile communication base station antenna device having a structure for adjusting each amplitude / phase variable unit such that the amplitude and phase of each element obtained by the amplitude / phase calculation unit become the output of the amplitude / phase variable unit. is there.

According to a second aspect of the present invention, there is provided a base station antenna apparatus for mobile communication which irradiates a band-like area, wherein the antenna elements are arranged in a straight line perpendicular to the longitudinal direction of the band-like area, and two or more elements are arranged. The number of elements is equal to or less than the number of elements, and the interval between the elements is not less than 1 wavelength and not more than 3 wavelengths. In the department,

As the transmission signal, a modulated signal such as a phase-modulated signal having a certain property such as a constant amplitude is used. An amplitude / phase calculator for calculating the amplitude and phase of each antenna input signal that minimizes the deviation; the amplitude and phase of each element obtained by the amplitude / phase calculator are output from the amplitude / phase variable device; This is a mobile communication base station antenna device having a structure for adjusting each amplitude / phase variable device so that

According to a third aspect of the present invention, there is provided a base station antenna apparatus for mobile communication which irradiates a band-like area, wherein the antenna elements are arranged in a straight line orthogonal to the longitudinal direction of the band-like area, and two or more elements are arranged. The number of elements is equal to or less than the number of elements, and the interval between the elements is not less than 1 wavelength and not more than 3 wavelengths. In the department,

Calculate the amplitude and phase of each antenna input signal which minimizes the error between the signal processed by the demodulator and the signal before the judgment on the synthesized signal of the signal received by each antenna element. A structure that has an amplitude / phase calculator and adjusts each amplitude / phase variable device so that the amplitude and phase of each element obtained by the amplitude / phase calculator becomes the output of the amplitude / phase variable device. Mobile communication base station antenna device.

According to a fourth aspect of the present invention, in the mobile communication base station antenna device according to any one of the first to third aspects, each element of the antenna has bidirectionality in a broadside direction of an array. It is configured by using elements.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below as examples. FIG. 1 shows a first embodiment of the present invention. In the figure, numeral codes 1-1 are omnidirectional antennas, 1-2 is a frequency converter, 1-3 is an amplitude / phase variable unit, 1-4 is an amplitude / phase calculation unit, and 1-5 is a modulation / demodulation unit. It represents. FIG. 13 shows an image when the present embodiment is applied to an actual place.

In FIG. 1, a signal received by an omnidirectional antenna 1-1 is converted into an intermediate frequency by a frequency converter 1-2, and an amplitude and a phase calculated by an amplitude / phase calculator 1-4 are respectively converted into an intermediate frequency. The received signal whose amplitude / phase has been set is set in the amplitude / phase variable unit 1-3 and is modulated / demodulated by the modem unit 1-5
Will be entered. The amplitude / phase value calculated by the amplitude / phase calculator 1-4 is supplied to the amplitude / phase variable unit 1-3, and the output of the amplitude / phase variable unit 1-3 is output to the amplitude / phase calculator 1- Control is performed so that the value of the calculation result of 4 is obtained.

According to the first aspect of the present invention, the content of the calculation by the amplitude / phase calculation unit 1-4 is determined by adding a signal known to the receiving side in advance,
The amplitude and phase of each antenna input signal are calculated so as to minimize the information error between the signal received and combined by each antenna element and the demodulated signal.

According to the second aspect of the present invention, the amplitude and phase of each antenna input signal which minimizes the deviation from the property of the modulated signal such as constant amplitude in the combined signal of the signals received by each antenna element is calculated.

According to the third aspect of the present invention, each antenna input signal which minimizes an error between a signal obtained by performing a determination process in a demodulation unit on a composite signal of a signal received by each antenna element and a signal before the determination is obtained. Calculate the amplitude and phase of.

FIG. 2 shows an image when the antenna of this embodiment is applied to an actual base station. In the figure, numeral 2-1 indicates an antenna, 2-2 indicates a base station apparatus, and 2-3
Represents a building such as a building, and 2-4 represents a road.

As a general antenna arrangement method, a linear arrangement and a circular arrangement can be considered. When a linear array is arranged in a street cell, a broadside array configuration in which antennas are arranged in a direction orthogonal to a road and an endfire array configuration in which antennas are arranged in parallel to a road are conceivable.

The number of elements N of the antenna is 4, the element interval s is 0.5 wavelength, and the input signal-to-noise ratio (SNR: Singlet)
FIG. 3 shows the result of comparing the error rate (BER) characteristics with respect to the Noize Ratio by changing the antenna arrangement. Here, the arrival rate distribution of the delay wave obtained by the measurement is used for the calculation of the error rate characteristic, and the arrival wave is -30 degrees from the delay wave of the maximum reception level.
A delayed wave of dB or more was used. Since each delayed wave measures power and does not have a phase component, the phase is given by a uniform random number.

The arrival wave characteristic of the delayed wave used for the calculation is 2 m on the sidewalk of the base station 150 m away from the base station.
Phases were calculated by changing the number of noise seeds ten times using five terminals whose terminals were moved at wavelength intervals. The specifications of the simulation are shown in Table 1. The transmission rate was set to 2M symbol / s as a rate at which a BER floor occurs due to delay when receiving with one element.

Each error rate characteristic curve is obtained by taking the geometric mean of the error rate characteristics under different propagation conditions. FIG.
As is clear, when the broadside arrangement is used, the same error rate characteristic is obtained in the state where the input SNR is the lowest. This is because, in the case of a broadside arrangement, the beam irradiating in the passing direction can be narrowest.

[0034]

[Table 1]

FIG. 4 shows a broadside structure having 0.5 wavelength intervals.
10 adaptive adaptive antennas^-3Error rate
When the element spacing is changed based on the input SNR
10 ^-35 shows the degree of improvement of the input SNR to obtain the error rate of. FIG.
As is clear, when the number of elements is 2 or 3
If the element spacing is one wavelength or more, the error rate is 10
^-3Can be improved by 0.5 dB or more.
Recognize.

Further, even if the element interval is set to three or more wavelengths, the improvement is not improved. Increasing the element spacing increases the size of the antenna.
It is understood that it is desirable to set the wavelength to about the wavelength or less.

With respect to the number of antenna elements, the array effect cannot be used unless there are two or more elements, and if six or more elements can be used, an antenna having a small side lobe, which is a conventional design concept, has a small element spacing. 1 wavelength or less)
However, in the present invention, this can be realized with two to five elements.

Furthermore, the direction of the terminal as viewed from the base station differs depending on the position of the terminal. For example, FIG. 5 shows an example of radiation characteristics after adaptive processing on a signal from a terminal on the sidewalk on the base station side when the number of elements is 4 and the element interval is 2 wavelengths.
Shown in

In the same figure, numeral 5-1 indicates an antenna, 5-2 indicates a terminal, and 5-3 indicates a direction in which communication quality is deteriorated. When fixed to this directivity, the terminal on the sidewalk on the base station side is irradiated with the main beam, but when the terminal is located in the null part of the directivity indicated by the shadow in FIG. The level decreases and the transmission characteristics deteriorate.

Therefore, an amplitude / phase variable device capable of varying the amplitude / phase is provided for each antenna input, and an amplitude / phase calculator for calculating the amplitude / phase applied to the amplitude / phase variable device of each antenna input is provided. By calculating and giving the amplitude and phase according to the incoming wave from the terminal, the beam can always be directed to the terminal.

As a method of determining the amplitude and phase, a method is known in which a known signal is transmitted in advance together with the transmission signal, and the receiving side obtains an amplitude and phase that minimizes the error between the known signal and the received signal. It can be obtained by a method of determining the amplitude and phase using the fact that the output amplitude of the signal is constant. As described above, by adopting the structure of the present invention, a base station antenna capable of reducing the propagation delay with a small number of elements can be configured.

FIG. 6 is a diagram showing a second embodiment of the present invention. In the figure, numeral 6-1 is a slot antenna having bidirectionality, 6-2 is a three-element antenna array, 6
-3 is a base station device, 6-4 is a road, and 6-5 is a building. This example is characterized in that an antenna having bidirectionality in the broadside direction of the array is used as an antenna element.

In this example, a narrow slot antenna is used. As shown in FIG. 1, when an omni-directional antenna is used as the antenna element, a large lobe is generated in the radiation pattern in the end fire direction as shown in FIG. 5, thereby reducing the gain in the desired wave direction. .

As shown in this embodiment, by using an element having bidirectionality in the broadside direction of the array and having a null in the endfire direction, the lobe in the endfire direction in FIG. 5 can be eliminated. As a result, the gain in the desired wave direction can be increased. FIG. 7 shows a relationship between a signal-to-noise ratio (SNR) and a transmission characteristic when a bidirectional antenna is used as an element.

In FIG. 7, the element directivity is given by cos φ. As is clear from FIG. 7, it can be seen that the transmission characteristics can be improved by using the bidirectionality. on the other hand,
When a narrow slot antenna is used as a bidirectional element as in the example shown in FIG. 6, the antenna can be configured in a shape like a bar lying down, so that a configuration that is inconspicuous in a landscape can be realized.

[0046]

As described above, according to the present invention,
A base station antenna capable of reducing the influence of propagation delay with a small number of elements can be realized. As a result, a long delay wave can be suppressed in a mobile communication base station that irradiates a belt-like area such as a road, and thus there is an advantage that a high-speed and highly reliable wireless channel can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is an image diagram when the first embodiment is applied to an actual base station.

FIG. 3 is a diagram for explaining the effect of the broadside array configuration of the present invention.

FIG. 4 is a diagram showing the relationship between the element spacing and the degree of improvement in SNR.

FIG. 5 is a diagram illustrating an example of radiation directivity when amplitude and phase are calculated and amplitude and phase are given so that transmission characteristics are best.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing an effect when the characteristics of the antenna element are set to be bidirectional.

FIG. 8 is a diagram showing an image of a street cell.

FIG. 9 is a diagram illustrating an example of measurement results of arrival characteristics of a delayed wave.

FIG. 10 is a diagram illustrating a concept of removing a delayed wave by a directional antenna.

FIG. 11 is a diagram showing a relationship between a free space propagation loss of a delayed wave reflected / scattered by a building facing a base station and an angle of arrival at the base station.

FIG. 12 is a diagram showing the reception level at the base station of a face-to-face delayed wave that affects transmission characteristics in consideration of the propagation loss of the delayed wave and the beam shape of the antenna.

FIG. 13 is a diagram showing a relationship between the number of elements and an angle of 15 dB below the maximum radiation direction when the element spacing is set to a half wavelength when implementing a pencil beam by a conventional antenna array.

[Explanation of symbols]

 1-1 Non-directional antenna 1-2 Frequency converter, 1-3 A / D converter, 1-4 Directivity calculator 1-5 Modulator / demodulator 2-1, 5-1 Array antenna 2-2 Base station device 2-3, 6-5, 9-3, 10-3 Building 2-4, 6-4, 8-3, 9-4 Road 5-2, 9-2, 10-2 Terminal 5-3 Communication quality Direction 6-1 slot antenna 6-2 three-element antenna array 6-3, 8-1, 9-1, 10-1 base station 8-2 cell 9-5 required directivity 10-4 zone 10 -5 Main beam 10-6 Beam

Claims (4)

[Claims] 1. A base station antenna device for mobile communication that irradiates a band-shaped area, wherein the antenna elements are arranged in a straight line orthogonal to a longitudinal direction of the band-shaped area, and the number of elements is 2 to 5 elements. The distance between each element is not less than 1 wavelength and not more than 3 wavelengths, and each antenna input section has an amplitude / phase variable device that can change the amplitude and phase of an input signal from each element, The receiving side has an amplitude / phase calculation unit that calculates the amplitude and phase of each antenna input signal so as to minimize an error between a signal known in advance and a composite signal of a signal received by each antenna element, A mobile communication base station antenna having a structure for adjusting each amplitude / phase variable unit so that the amplitude and phase of each element obtained by the phase calculation unit become the output of the amplitude / phase variable unit; apparatus. 2. A base station antenna device for mobile communication that irradiates a band-shaped area, wherein the antenna elements are arranged in a straight line orthogonal to the longitudinal direction of the band-shaped area, and the number of elements is 2 to 5 elements. The distance between each element is not less than 1 wavelength and not more than 3 wavelengths, and each antenna input section has an amplitude / phase variable device that can change the amplitude and phase of an input signal from each element, As a transmission signal, a signal such as a phase modulation signal is a modulation signal having a certain property such as a constant amplitude, and in a combined signal of signals received by each antenna element,
An amplitude / phase calculator for calculating the amplitude and phase of each antenna input signal that minimizes the deviation from the property of the modulation signal such as constant amplitude; and the amplitude and phase of each element obtained by the amplitude / phase calculator. A mobile communication base station antenna device having a structure for adjusting each amplitude / phase variable device so that a phase becomes an output of the amplitude / phase variable device. 3. A base station antenna device for mobile communication that irradiates a band-shaped area, wherein the antenna elements are arranged in a straight line orthogonal to the longitudinal direction of the band-shaped area, and the number of elements is 2 to 5 elements. The distance between each element is not less than 1 wavelength and not more than 3 wavelengths, and each antenna input section has an amplitude / phase variable device that can change the amplitude and phase of an input signal from each element, Amplitude / phase for calculating the amplitude and phase of each antenna input signal that minimizes the error between the signal processed by the demodulation unit and the signal before the judgment on the synthesized signal of the signal received by each antenna element A calculator for adjusting each amplitude / phase variable device such that the amplitude and phase of each element obtained by the amplitude / phase calculator are output from the amplitude / phase variable device. And move Communication base station antenna device. 4. The mobile communication base station antenna according to claim 1, wherein an element having bidirectionality in a broadside direction of the array is used as each element of the antenna. .