JPH11251986A - Adaptive antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device small in size and capable of easily performing shadowing compensation with respect to the antenna device used in a radio communication system. SOLUTION: This adaptive antenna device constituted of plural antenna elements 1011-101N, a first directivity pattern formation device 103 using the output signals of the plural antenna elements 1011-101N as input signals and a first demodulator 105 using the output signals of the elements as input signals is provided with an orthogonal directivity pattern formation device 106 forming directivity orthogonal to a directivity pattern formed in the first directivity pattern formation device 103 and using the output signals of the plural antenna elements 1011-101N and the output signals of the first directivity pattern formation device 103 as input signals, a second demodulator 107 connected to the orthogonal directivity pattern formation device 106 and a synthesizer 108 for inputting the output signals of the first demodulator 105 and the output signals of the second demodulator 107, selecting one of the two signals or synthesizing the two signals and generating the output of the adaptive antenna device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device used for a small-scale radio communication system, and more particularly to an antenna device which can easily compensate for shadowing and interference.
The present invention relates to a small antenna device suitable for constructing a LAN using a wireless line.

[0002]

2. Description of the Related Art In recent years, with the spread of computers,
Computers are also used in offices on a daily basis. In general, these computers are connected to each other and a peripheral device by connecting peripheral devices with a local area network (LA) for the purpose of sharing peripheral devices such as data and a printer in an office.
N) is often used.

Conventionally, such a LAN has been constructed by laying out a connection cable in advance in a place where a computer is installed in an office, and connecting the cable to each computer. However, if a cable is used, when the position of the computer is moved, the wiring must be redone, and in the case of a computer having no permanent position, such as a portable computer, there is a problem that the wiring position cannot be determined in advance. .

As a solution to such a problem, there has been proposed a wireless LAN in which a base station is installed in a place with a good view of a room and wirelessly connects with each terminal. Wireless L
When transmitting fast data using an AN, it is necessary to minimize the propagation delay that occurs in a wireless section. Such a reduction in propagation delay can be realized by narrowing the beam width of the base station antenna or the terminal antenna.

[0005] These are described, for example, in the documents "Kazuhiro Uehara, Tomohiro Seki, Kenichi Kagoshima," Analysis of Indoor Propagation Characteristics for Arbitrary Directional Antennas by Geometrical Optics, "
II, vol. J78-B-II, no. 9, pp. 593-601, September 1995. And the like. Then, the wireless L currently commercialized
The AN device enables high-speed transmission by using sector antennas for base station antennas and terminal antennas.

[0006]

One of the major problems in a wireless LAN is the deterioration of transmission characteristics due to shadowing. This is because, for example, when a person crosses between a base station and a terminal, a strong radio wave arriving directly from the transmission side to the reception side is blocked, so that the reception level is reduced, and therefore, the transmission characteristics are greatly deteriorated. is there.

As a countermeasure against such shadowing, a configuration in which a plurality of antennas are installed and a view between transmission and reception is secured by any one of the antennas is disclosed in the document “Kurosaki, Nakamura, Aikawa,“ Shadowing. Study on the effect of diversity improvement on communication ", Proceedings of the 1996 IEICE Communication Society Conference, B-479.

FIG. 6 shows an example of the above-described conventional shadowing compensation method. In the figure, reference numeral 601 denotes a terminal station antenna, reference numeral 602 denotes a base station antenna A, and reference numeral 603.
Denotes a base station antenna B, reference numeral 604 denotes a selection diversity device, and reference numeral 605 denotes a shield.

By adopting a configuration as shown in FIG.
Base station antenna A 602 and base station antenna B 603
Even if shadowing occurs in either of the above cases, the visibility can be ensured with the other antenna. Therefore, if the switching of the antenna is performed by the selection diversity device 604, the probability of occurrence of transmission characteristic deterioration due to shadowing can be kept low. .

[0010] However, in the method using the conventional diversity system, the size of the antenna device is inevitably increased, and further, when each antenna is shadowed simultaneously,
There was a problem that the line was disconnected. Therefore, as a method of reducing the size of the antenna and improving the transmission characteristics, a plurality of antenna elements are arranged in an array, and the amplitude and phase are weighted to the signals of each antenna element, thereby adaptively directing. Adaptive antennas with variable characteristics have been proposed.

FIG. 7 shows an example of a conventional adaptive antenna device. In the figure, reference numerals 701 to 70N denote an antenna device, 71 denotes a directional pattern forming device, and 72 denotes a demodulator. Such an antenna is described, for example, in the document "RAMo
ngingo, et.al., Introduction toadaptive array, New Yo
rk & Sons, 1980 ". By using this antenna device, it is possible to receive a signal under the condition that the signal-to-noise ratio is maximum in a given configuration.

Therefore, the number of antenna elements for obtaining a specified transmission quality can be minimized, so that the antenna can be downsized. In such an adaptive antenna, how to determine the weight quickly when weighting each element and simplification of the control device are important issues.

As an example of a configuration for simplifying the control of the adaptive antenna, before calculating weights for weighting, first, a plurality of orthogonal beam forming processes are performed. There has been proposed a method of performing a weighting process using only the weighting process.

This method is described in, for example, "Documents" Tanaka, Miura, Karasawa, "Experiment on Interference Wave Suppression of BSCMA Adaptive Array""IEICE Technical Report, vol.95, No.53
5, pp. 49-54, 1996. FIG. 8 shows the configuration. In the figure, reference numerals 801 to 80N denote an antenna device, 81 denotes a multi-beam forming device, 82 denotes a beam selecting device, 83 denotes a directional pattern forming device, and 84 denotes a demodulator.

In the configuration shown in FIG. 8,
The orthogonal beam forming is performed by the FFT operation, and the weighting is performed only for the output having a high reception level. As a result, the number of signals to be weighted is reduced, so that high-speed operation and hardware-scale power saving can be realized.

However, even if the conventional adaptive antenna apparatus is used, when the distance between the transmitting and receiving antennas is in sight, the directivity is formed so as to receive the wave directly passing between the transmitting and receiving antennas having the highest signal strength. When shadowing occurs, there is a problem that the reception level is significantly deteriorated, the transmission characteristics are greatly deteriorated, and in the worst case, the line connection is disconnected.

In addition to the shadowing, the transmission quality deteriorates due to the occurrence of new interference from other terminal stations during communication. An object of the present invention is to increase the size of an antenna to solve problems such as line disconnection due to remarkable deterioration of transmission quality due to sudden environmental changes such as shadowing and interference during communication and transmission delay caused by retransmission of data. It is an object of the present invention to provide an antenna device that can be solved without any problem.

[0018]

According to the present invention, the above-mentioned object is solved by the means described in the claims. That is, according to the first aspect of the present invention, a plurality of antenna elements, a first directional pattern forming apparatus having output signals of the plurality of antenna elements as input signals, and an output of the first directional pattern forming apparatus are provided. In an adaptive antenna device including a first demodulator as an input signal,

The output signals of the plurality of antenna elements and the output signal of the first directional pattern forming device are used as input signals, and the directivity is orthogonal to the directional pattern formed by the first directional pattern forming device. An orthogonal directional pattern forming device, and a second demodulator connected to the orthogonal directional pattern forming device;

The output signal of the first demodulator and the output signal of the second demodulator are input, and either one of these two signals is selected or the two signals are synthesized. , An adaptive antenna device including a combining device that generates an output of the adaptive antenna device.

According to a second aspect of the present invention, in the adaptive antenna device according to the first aspect, the orthogonal directivity pattern forming device inputs the output signals of the plurality of antenna elements to the orthogonal transform device, respectively, and outputs the first directivity pattern. The orthogonal signal is converted so as to be orthogonal to the output signal of the directional pattern forming apparatus, and the converted signals are combined so that an error in the output of the orthogonal directional pattern forming apparatus is minimized.

According to a third aspect of the present invention, in the adaptive antenna device according to the second aspect, the orthogonal directional pattern forming device includes a clock for identifying the first demodulator and a clock for identifying the second demodulator. Using a clock, at the time of identification of the first demodulator, the output signals of the plurality of antenna elements are converted so as to be orthogonal to the output signals of the first directional pattern forming device, and the second demodulator And means for synthesizing the converted signals so that an error in the output of the orthogonal directivity pattern forming apparatus is minimized at the identification timing.

According to a fourth aspect of the present invention, a plurality of directional patterns are formed by using a plurality of antenna elements and output signals of the plurality of antenna elements as input signals, and a plurality of signals corresponding to the respective directional patterns are output signal signals. A first directional pattern forming apparatus having an output signal of the multi-beam forming apparatus as an input signal, and a first directional pattern forming apparatus having an output of the first directional pattern forming apparatus as an input signal. In an adaptive antenna device composed of a demodulator,

An orthogonal directional pattern forming apparatus for forming a directivity orthogonal to a directional pattern formed by the first directional pattern forming apparatus by using an output of the multi-beam forming apparatus as an input signal; The second demodulator connected to the characteristic pattern forming device, the output signal of the first demodulator, and the output signal of the second demodulator are input, and any one of these two signals is input. Select or 2
The adaptive antenna device includes a combining device that combines two signals to generate an output of the adaptive antenna device.

According to a fifth aspect of the present invention, in the adaptive antenna device according to any one of the first to fourth aspects,
During communication, when the communication quality of the output signal of the first directional pattern forming device becomes equal to or less than a predetermined threshold, the directional pattern formed by the first directional pattern forming device is not changed. Is provided with a control means.

According to the present invention, there is provided a first directional pattern forming apparatus and a first receiver (demodulator) for forming a directional pattern of an adaptive antenna from a signal of each element of an array composed of a plurality of antenna elements. In addition to the configuration having the second directivity pattern forming device, the second directivity pattern forming device includes a second directional pattern forming device that splits a signal from an antenna element and inputs the signal, and a second receiver (demodulator). Seeking a directivity orthogonal to the directivity generated by the first directivity pattern forming device, characterized by having a configuration to switch the output of the first receiver and the output of the second receiver, or to combine I have.

[0027] The prior art is that the second directional pattern forming apparatus has a second directional pattern forming apparatus and a second receiver, and the second directional pattern forming apparatus has a directional pattern formed by the first directional pattern forming apparatus. The difference is that a directivity that is orthogonal to the characteristic is formed and switched or combined with the signal of the first receiver.

Since shadowing is caused by blocking a direct wave, a large environmental change occurs in the direction of the direct wave. On the other hand, environmental fluctuations are small in directions other than the arrival direction of the direct wave. Therefore, if a directivity pattern having no directivity in the direction of the direct wave (for example, having a null point in the direction of the direct wave) is created, fluctuations in transmission characteristics before and after shadowing can be suppressed.

Also, when an interference wave from the same direction as the terminal station arrives at the base station during communication and deteriorates the transmission quality, if a pattern having no directivity in the direct wave direction is used,
The influence of interference is small. When the adaptive antenna apparatus is operated so that the square error at the output is minimized, the maximum gain direction of the directivity matches the direction of the terminal station. Therefore, by forming a directivity orthogonal to the directivity of the adaptive antenna, a directivity pattern having no directivity in the direction of the direct wave can be formed.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first example of an embodiment of the present invention, and shows a configuration in which a quadrature directional pattern forming device, a second demodulator, and a selecting device are added to a conventional adaptive antenna device. . In FIG.
Reference numerals 011 to 101N are a plurality of antenna elements, for example, constituting a planar array antenna or a cylindrical array antenna.

Reference numerals 1021 to 102N indicate first branching means connected to the antenna elements 1011 to 101N. Branch is RF, = F, baseband or A / D
Performed after conversion. When branching is performed by RF, a degradation of 3 dB occurs. In a system in which the degradation of 3 dB is a problem, a signal received by an antenna is amplified by an amplifier and then branched.

Reference numeral 103 denotes a first directional pattern forming device, which is realized, for example, by imposing a complex weight on each input signal and then combining them. As a method of imposing a complex weight, for example, there is a method using a combination of an amplifier and a phase shifter, or a method of performing A / D conversion on a received waveform of each element antenna and then performing digital signal processing.

The value of each complex weight is determined by the CMA algorithm for controlling the envelope at the output to be constant, the LMS algorithm, the RLS algorithm for controlling the square of the error of the output signal with respect to the reference signal, or the like. When the arrival direction of the direct wave is known, an SM = algorithm or a DCMP algorithm that restricts the antenna gain in the direct wave direction to minimize the output is used.

Reference numeral 104 denotes a second branching unit that uses the output of the first directional pattern forming device 103 as an input signal y and branches the signal into two output signals. Reference numeral 105 denotes a first demodulator connected to one of the second branching means 104. Reference numeral 106 denotes an orthogonal directional pattern forming device, which operates, for example, as follows.

Each of the signals xl to xN input from the first branch means 1021 to 102N can be reduced by a value obtained by imposing complex weights W'1 to W'N on the input signal y from the second branch means 104. . Here, the values of the complex weights W′1 to W′N are determined to be different for each signal input from the first branching means 1021 to 102N so that the result of the subtraction becomes the smallest value. .

A signal having a high level is selected from the plurality of subtracted signals, and the selected signal is used as an output of the orthogonal directivity pattern forming apparatus. Reference numeral 107 denotes a second demodulator connected to the orthogonal directivity pattern forming device. Reference numeral 108 denotes a synthesizing device. The synthesizer receives two signals, an output of the first demodulator 105 and an output of the second demodulator 107, as inputs.

Then, the two signals are synthesized using a method such as selection, or maximum ratio synthesis, or synthesis that minimizes the square error. At the time of synthesis, since the demodulation timing is different in each demodulator, the timing is corrected. By applying this configuration, it is possible to eliminate instantaneous interruption of a line or transmission delay that occurs when shadowing occurs.

FIG. 2 is a diagram showing a second example of the embodiment of the present invention. In the orthogonal directivity pattern forming apparatus 106, the optimum point is formed under the condition that a null point is formed directly in the wave direction. 3 shows an apparatus for forming a directional pattern. In the figure, reference numerals 2011 to 201N denote orthogonal transform devices, and signals xl to xN input manually from first branching units 1021 to 102N are input signals y from second branching unit 104.
Are subtracted from the values obtained by applying the complex weights W′1 to W′N to the output.

Here, the values of the complex weights W'1 to W'N are determined so that the outputs of the orthogonal transform devices 2011 to 201N become the smallest values. Reference numeral 202 denotes a selection device, which is connected to the orthogonal transform device and receives M (<
N) signals are selected. The selection is made based on, for example, the level or the transmission quality.

Reference numeral 203 denotes a second directional pattern forming device that combines the M signals selected by the selecting device, and for example, applies complex weights W1 to WM to the M input signals and then combines the signals. Is achieved. As a method of imposing a complex weight, for example, there is a method using a combination of an amplifier and a phase shifter, or a method of performing A / D conversion on each input signal and then performing digital signal processing.

The values of the complex weights are determined by a CMA algorithm for controlling the envelope at the output to be constant, an LMS algorithm, an RLS algorithm for controlling the square of the error of the output signal with respect to the reference signal, When the arrival direction of the direct wave is known, an SM = algorithm or a DCMP algorithm that restricts the antenna gain in the direct wave direction to minimize the output is used. By using this configuration, the orthogonal pattern forming apparatus 106 can obtain an optimal directivity under the condition that it has a null point in the direct wave direction.

FIG. 3 is a diagram showing a third example of the embodiment of the present invention. In this example, a multi-beam forming apparatus 301 is used.
And a configuration for operating the orthogonal directional pattern forming apparatus 106 in feedforward. In the figure, reference numeral 301 denotes a multi-beam forming apparatus, which forms outputs of a plurality of antenna elements 1011 to 10IN as input signals and performs FFT on the input signals to form N orthogonal beams.

Reference numeral 302 denotes a beam selecting device, which is formed inside the orthogonal directivity pattern forming device. Among the input signals from the first branching means 1021 to 102N, a high-level input signal is transmitted in the direct wave direction. It is determined that the signal corresponds to a beam, and M signals excluding the input signal are output. The output signal is input to the second directional pattern forming device 203. By using this configuration, it is possible to form a directional pattern that does not directly receive a wave without an input signal from the second branching unit 104.

FIG. 4 is a diagram showing a fourth example of the embodiment of the present invention. This example is a configuration in a case where the present invention is applied to an environment where there are far more delayed waves than the number of antenna elements. Reference numeral 401 denotes a first identification timing reproduction circuit for reproducing the identification time in the first demodulator. Code 4
Reference numeral 02 denotes a second identification timing reproducing circuit for reproducing the identification time in the second demodulator.

In an environment such as an indoor wireless communication system, there are delayed waves far exceeding the number of antenna elements. When the number of the delayed waves becomes equal to or more than the number of elements of the antenna, the components of the delayed waves appear in the output of the first directional pattern forming device 103 except for the identification time. At this time, the input signals xl to xN from the element antenna cannot be converted so as to be orthogonal to the input signal y from the first directional pattern forming device 103 at all times.

However, in practice, the orthogonal transformation device 2011
If the direct wave component is removed at ~ 201N, the orthogonal pattern forming device 106 can form a directional pattern that reduces the antenna gain in the direction of arrival of the direct wave. Therefore, at the timing of the identification time of the first demodulator 105 where the output y of the first directional pattern forming device 103 is only the direct wave component, the orthogonal transform devices 2011 to 201N are adapted to remove the direct wave component. What is necessary is just to comprise an antenna apparatus.

The complex weights W'1 to W'N to be applied to the input signals from the first directivity pattern forming devices in the orthogonal transform devices 2011 to 201N are determined at the timing of the identification time of the first demodulator by the orthogonal transform devices. It is determined so that the outputs of 2011 to 201N are minimized. By using this configuration, even in an environment where the delay wave exceeds the number of antenna elements, it is possible to realize a directional pattern in which the antenna gain in the direct wave direction is reduced in the orthogonal pattern forming circuit.

FIG. 5 is a flow chart showing the control in the fifth example of the embodiment of the present invention. If the visibility is restored again after the occurrence of shadowing, the instantaneous interruption of the line or the transmission delay is prevented. The method of controlling is shown. Reference numerals 103 and 106 used in each section in the drawing and reference numeral 105 used in the following description correspond to FIGS. In the figure, first, the first directional pattern forming device 103 is operated so as to form an optimal directional pattern when receiving a direct wave before starting communication.

After the first directivity pattern has converged, the orthogonal directivity pattern forming device 106 is operated to start communication when an optimum directivity pattern is formed. In the system where the terminal station moves after the start of communication, for example, the peak direction of the first directivity pattern is made to coincide with the terminal station direction by controlling as follows. The clock timing reproduced inside the first demodulator 105 is fixed, and the first directivity pattern is updated in synchronization with this evening, so that the peak direction of the first directivity pattern becomes a direct wave. Direction, that is, the terminal station direction.

If the transmission quality of the first demodulator 105 deteriorates during communication, it is determined that a shadowing state has occurred, and the first directivity pattern is fixed without updating. After the transmission quality of the first demodulator 105 is restored, the first directivity pattern is updated again. When the first directivity pattern is updated at the time of occurrence of shadowing, transmission quality deteriorates at the time of line-of-sight recovery. Therefore, by using this method, it is possible to suppress deterioration of transmission characteristics at the time of line-of-sight recovery.

[0051]

As described above, according to the present invention,
Prevents instantaneous disconnection of lines due to remarkable deterioration of transmission quality caused by sudden changes in communication environment during communication, such as shadowing and newly generated interference, and transmission delay caused by retransmission of data There is an advantage that an antenna device that can be easily realized can be realized without increasing the antenna size.

FIG. 9 shows the cumulative probability of output SINR when shadowing occurs when the present invention is used and when a conventional adaptive antenna device is used. In the conventional adaptive antenna apparatus, the place where the output SINR falls to 10 dB or less is 50%, whereas the place where the present invention is used is 2%.
0% or less, without causing transmission delay,
It can be seen that communication can be performed.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a second example of the embodiment of the present invention.

FIG. 3 is a diagram showing a third example of the embodiment of the present invention.

FIG. 4 is a diagram showing a fourth example of the embodiment of the present invention.

FIG. 5 is a flowchart showing control of a fifth example of the embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of a conventional shadowing compensation method.

FIG. 7 is a diagram illustrating an example of a conventional adaptive antenna device.

FIG. 8 is a diagram illustrating an example of an adaptive antenna device using a conventional multi-beam forming device.

FIG. 9 is a diagram showing a comparison of the cumulative probability of output SINR when shadowing occurs.

[Explanation of symbols]

 1011 to 101N Antenna elements 1021 to 102N First branching means 103 First directivity pattern forming device 104 Second branching means 105 First demodulator 106 Quadrature directivity pattern forming device 107 Second demodulator 108 Synthesizing device 2011-201N orthogonal transformation device 202 selection device 203 second directional pattern formation device 301 multi-beam formation device 302 beam selection device 401 first identification timing reproduction device 402 second identification timing reproduction device 601 terminal station antenna 602 base station Antenna A 603 Base station antenna B 604 Selection diversity device 605 Shield 7011 to 701N Antenna device 71 Directional pattern forming device 72 Demodulator 8011 to 801N Antenna device 81 Multi-beam forming device 82 Beam selecting device 83 Direction Pattern forming apparatus 84 demodulator

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuhiro Uehara 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Kentaro Nishimori 3- 19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. Japan Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. A plurality of antenna elements, a first directional pattern forming apparatus using output signals of the plurality of antenna elements as input signals, and an output of the first directional pattern forming apparatus as an input signal. In the adaptive antenna device configured by the first demodulator, the output signals of the plurality of antenna elements and the output signal of the first directional pattern forming device are input signals, and the first directional pattern forming device An orthogonal directivity pattern forming device that forms directivity orthogonal to the formed directivity pattern, a second demodulator connected to the orthogonal directivity pattern forming device, and an output signal of the first demodulator. The output signal of the second demodulator, and selecting one of these two signals or combining the two signals to generate an output of the adaptive antenna device. To do An adaptive antenna device characterized by the above-mentioned. 2. An orthogonal directional pattern forming apparatus inputs respective output signals of a plurality of antenna elements to an orthogonal transform apparatus, converts the signals so as to be orthogonal to an output signal of a first directional pattern forming apparatus, and performs conversion. 2. The adaptive antenna apparatus according to claim 1, wherein each of the obtained signals is combined so that an error in an output of the orthogonal directivity pattern forming apparatus is minimized. 3. The orthogonal directional pattern forming apparatus uses the clock of the identification timing of the first demodulator and the clock of the identification timing of the second demodulator to generate the identification timing of the first demodulator. Convert the output signals of the plurality of antenna elements so as to be orthogonal to the output signal of the first directional pattern forming device, at the time of identification of the second demodulator,
3. The adaptive antenna device according to claim 2, further comprising means for combining the converted signals so that an error in an output of the orthogonal directivity pattern forming device is minimized. 4. A multi-beam forming apparatus for forming a plurality of directional patterns using a plurality of antenna elements and output signals of the plurality of antenna elements as input signals, and using a plurality of signals corresponding to the directional patterns as output signals. A first directional pattern forming apparatus having an output signal of the multi-beam forming apparatus as an input signal, and a first demodulator having an output of the first directional pattern forming apparatus as an input signal. An adaptive antenna device, comprising: an orthogonal directional pattern forming device that forms a directivity orthogonal to a directional pattern formed by the first directional pattern forming device, using an output of the multi-beam forming device as an input signal; A second demodulator connected to the orthogonal directional pattern forming device, an output signal of the first demodulator, and an output signal of the second demodulator are input to each other. An adaptive antenna apparatus comprising: a synthesizing apparatus that selects one of the two or combines two signals to generate an output of the adaptive antenna apparatus. 5. The communication device according to claim 1, wherein the communication control unit determines whether the communication quality of the output signal of the first directivity pattern forming device is equal to or less than a predetermined threshold during communication. The adaptive antenna device according to any one of claims 1 to 4, further comprising means for controlling so as not to change.