JP4489460B2 - Adaptive array antenna system, adaptive array antenna control method, and radio apparatus - Google Patents

Description

  The present invention relates to an adaptive array antenna system, an adaptive array antenna control method, and a radio apparatus including the adaptive array antenna system.

  Conventionally, in wireless communication, radio waves are reflected, diffracted, and scattered by obstacles such as buildings. For this reason, since the wireless propagation path becomes a multiple propagation path, multipath fading due to multiple waves occurs, and communication quality deteriorates. Therefore, in order to reduce these adverse effects, an adaptive array antenna system is provided in a radio apparatus, for example, a radio base station or a mobile station.

  The adaptive array antenna system includes an array antenna in which a plurality of antenna elements are arranged, and receives a signal received by the array antenna by forming a directivity pattern by adaptive signal processing. As a result, a reception directivity pattern can be formed in the arrival direction of the desired wave and a null of the directivity pattern can be formed in the arrival direction of the interference wave such as a delayed wave to suppress the interference wave. Communication quality has been improved. Further, if the above-described directivity pattern is applied at the time of transmission, there are advantages that interference with wireless devices other than the transmission partner can be reduced and transmission power can be reduced.

  An adaptive algorithm based on MMSE (Minimum Mean Square Error) is used for the adaptive signal processing of the adaptive array antenna system described above. Known adaptive algorithms based on MMSE include, for example, LMS (Least Mean Square) and RLS (Recursive Least-Squares). In the adaptive signal processing by this MMSE-based adaptive algorithm, an average square error is obtained from the difference between the local reference signal generated inside the wireless device and the training signal in the received signal, and the value of this error is minimized. A weight (weight coefficient) for controlling the phase and amplitude of the received signal is calculated (for example, see Non-Patent Document 1).

As an array antenna, a system using an omnidirectional antenna and a system using a directional antenna are known.
In a system using an omnidirectional antenna, each antenna element is arranged with an arrangement interval corresponding to the RF frequency band to be used. For example, when the 860 MHz band is used, an arrangement interval of the half wavelength “about 17 cm” of the 860 MHz is taken. When the 2 GHz band is used, the arrangement interval of the 2 GHz half wavelength “about 7.5 cm” is taken.

In a system that uses directional antennas, a delay profile estimator is provided for each directional antenna element to estimate the delay profile that represents the arrival time and received power of the desired wave, and the directivity pattern of the array antenna is formed. Yes.
Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing Co., Ltd., November 1998, p. 35-64

However, the conventional techniques described above have the following problems.
A system using an omnidirectional array antenna is not suitable for miniaturization because a certain interval is required when arranging each antenna element. For this reason, it is preferable to use a directional array antenna for a portable terminal or the like that is required to be downsized.

  However, in a system using a directional array antenna, it is necessary to estimate a delay profile for each directional antenna element, so that the amount of calculation increases and a large calculation capability is required. For this reason, it is difficult to secure sufficient calculation capability in a portable terminal or the like that requires cost saving and power saving, and it is difficult to apply a directional array antenna. In the mobile communication system, since radio communication is performed between an unspecified base station and a mobile station, it is impossible to distinguish between a desired wave and an interference wave in advance. Therefore, when calculating delay profiles of all incoming signals including not only the desired wave but also interference waves from other base stations, the calculation amount is enormous, and therefore, it is applied to a portable mobile terminal. It becomes very difficult.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an adaptive array antenna system and an adaptive array antenna control method suitable for miniaturization, cost saving, and power saving.

  Another object of the present invention is to provide a radio apparatus provided with the adaptive array antenna system of the present invention.

In order to solve the above problems, an adaptive array antenna system according to the present invention includes an array antenna including a plurality of directional antennas, and a selection unit that selects a desired wave based on each received signal of the plurality of antennas. Receiving control means for weighting each received signal received by each of the plurality of antennas in order to form a directivity pattern of the array antenna toward the arrival direction of the desired wave selected by the selecting means; and Transmission control means for weighting each transmission signal transmitted from each of the plurality of antennas, wherein the transmission control means is a weight for each reception for weighting each reception signal in the reception control means. Among them, the receiving weight having the maximum weighting amount and the receiving weight having the same weighting amount as the maximum weighting amount, Each weight maximum value for transmission corresponding transmission is otherwise wait for transmission so that a zero, that the weight for transmission for weighting the respective transmission signals respectively set, is the set Each transmission signal is weighted by a weight.

An adaptive array antenna system according to the present invention includes an array antenna composed of a plurality of antennas having directivity, an adding means for adding all the received signals of the plurality of antennas, and a signal resulting from the addition by the adding means. Detection means for detecting a desired wave, and each received signal received by each of the plurality of antennas to form a directivity pattern of the array antenna in the direction of arrival of the desired wave detected by the detection means And a transmission control means for weighting each transmission signal transmitted from each of the plurality of antennas, wherein the transmission control means weights the reception signals in the reception control means. Out of the receiving weights for receiving, the receiving weight that is the maximum weighting amount and the weighting equivalent to the maximum weighting amount Labeled amount and the weight for receiving comprising, in at weights maximum value for transmission corresponding respectively, it like other weight for transmission is zero, the transmission weight for weighting each of said transmission signals, respectively It sets, and weights each said transmission signal with the set transmission weight, It is characterized by the above-mentioned.

An adaptive array antenna system according to the present invention includes an array antenna including a plurality of directional antennas, one omnidirectional antenna, detection means for detecting a desired wave from a received signal of the omnidirectional antenna, Receiving control means for weighting each received signal received by each of the plurality of antennas in order to form a directivity pattern of the array antenna toward the direction of arrival of the desired wave detected by the detecting means; and Transmission control means for weighting each transmission signal transmitted from each of a plurality of antennas, wherein the transmission control means includes a weight for each reception for weighting each reception signal in the reception control means A receiving weight having a maximum weighting amount and a receiving weight having a weighting amount equivalent to the maximum weighting amount. The maximum value the weight for transmission corresponding, respectively are, as other weight for transmission is zero it the transmission weight for weighting each transmission signal respectively set by the set transmission weights Each of the transmission signals is weighted.

A wireless device according to the present invention includes any one of the adaptive array antenna systems described above, and performs wireless communication using the adaptive array antenna system.

An adaptive array antenna control method according to the present invention is directed to a process of selecting a desired wave based on each received signal of a plurality of antennas having directivity constituting an array antenna, and to the arrival direction of the selected desired wave Weighting each received signal received by each of the plurality of antennas and weighting each transmission signal transmitted from each of the plurality of antennas to form a directivity pattern of the array antenna. In the process of weighting each transmission signal , among the reception weights for weighting each reception signal, the reception weight that is the maximum weighting amount is equivalent to the maximum weighting amount. The weights for reception, which are the weights of the transmission, and the transmission weights corresponding to each of them are the maximum value, and the other transmission weights are zero. As such, the respectively set the transmission weight for weighting each transmission signal, weighting the respective transmission signal by the transmission weight that is the set, characterized in that.

An adaptive array antenna control method according to the present invention includes a process of adding all received signals of a plurality of antennas having directivity constituting an array antenna, a process of detecting a desired wave from the added signal, Weighting each received signal received by each of the plurality of antennas to form a directivity pattern of the array antenna toward the direction of arrival of the detected desired wave; and Weighting each transmission signal transmitted from each, and in the step of weighting each transmission signal , the maximum weighting amount of each reception weight for weighting each reception signal is obtained The transmission weight corresponding to each of the reception weight and the reception weight having the same weighting amount as the maximum weighting amount is the maximum value. As other weights for transmission becomes zero, the transmission weight for weighting each transmission signal set respectively, weighting the respective transmission signal by the set transmission weight, and wherein the .

An adaptive array antenna control method according to the present invention includes a process of detecting a desired wave from a received signal of one omnidirectional antenna, and forming a directivity pattern of the array antenna toward an arrival direction of the detected desired wave. Each of the plurality of antennas includes: a step of weighting each received signal received by each of the plurality of antennas; and a step of weighting each transmission signal transmitted from each of the plurality of antennas. In the process of weighting each reception signal , among the reception weights for weighting each reception signal, the reception weight having the maximum weighting amount and the reception weight having the same weighting amount as the maximum weighting amount The transmission signals are weighted so that the transmission weights corresponding to the maximum value are zero and the other transmission weights are zero. Transmission weights are set, and the transmission signals are weighted by the set transmission weights.

  According to the present invention, since an array antenna having directivity can be used, it is possible to cope with downsizing. Furthermore, since a desired wave is detected from the sum signal of the output signals of a plurality of antennas having directivity or the output signal of one omnidirectional antenna, there is no need to obtain a delay profile for each antenna element. As a result, an increase in the amount of computation can be prevented, and cost and power savings can be accommodated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an adaptive array antenna system according to the first embodiment of the present invention. The adaptive array antenna system shown in FIG. 1 is provided in a mobile station of a CDMA (Code Division Multiple Access) (IS-95, etc.) mobile communication system in a wireless communication system. In the mobile station of the CDMA mobile communication system, the adaptive array antenna system according to the present embodiment includes a plurality of antenna elements 1-1 to N having different directivities for radio signals transmitted from the base station. It received using array antenna (antenna unit 1), was synthesized by weighting the received signals x ₁ ~x _N in weight vector a for forming a directivity pattern toward the arrival direction of the desired wave, array output A signal y is generated. The transmission signal is transmitted after the weight vector A used for the received signals x _{1 to} x _N is weighted with the corrected weight vector B.

  In FIG. 1, the antenna unit 1 includes the antenna elements 1-1 to N arranged so as to cover all directions by the directivity directions of the plurality of antenna elements 1-1 to N having different directivities. Yes. For example, as shown in FIG. 2, eight antenna elements 1-1 to 8 are used, and the eight antenna beams P1 to P8 are overlapped to cover all directions.

The reception outputs of the antenna elements 1-1 to N are input to the down / up converter 2 and converted into baseband signals by the down converter. The baseband signal is converted into a digital signal and then output as received signals x _{1 to} x _N. These received signals x _{1 to} x _N correspond to the antenna elements 1-1 to _N , respectively. That is, the reception signal x ₁ ~x _N is the signal received from each of the directivity direction by the antenna elements 1-1 to 1-N (each directional output signal of the array antenna).

Received signals x _{1 to} x _N are input to array weight control unit 3, weighting synthesis unit 4, and addition unit 5, respectively.
Array weight controller 3 is for performing adaptive signal processing using an adaptive algorithm such as MMSE, such as LMS algorithm, the weight w _r1 to w _rN for forming a directivity pattern toward the arrival direction of the desired wave (Weight vector A) is calculated. The weight vector A is input to the weighting synthesis unit 4 and the weight correction unit 11.
Weighting combining unit 4 has a structure shown in FIG. 3, after weighting by multiplying the corresponding weights w _r1 to w _rN by the respective multipliers 21 to the received signal x ₁ ~x _N, adders 22 is added and synthesized. The combined signal is output as an array output signal y.

The adder 5 adds all the received signals x _{1 to} x _N and outputs the result. The output signal of the adding unit 5 includes reception signals from all directions. The output signal of the adder 5 is input to the searcher 6. The searcher 6 extracts information such as a transmission signal from a surrounding base station, a PN offset of a PN spreading code, a path timing (finger), and received power from the output signal of the adder 5. The structure of the searcher is publicly known, and is described, for example, in “Takuro Sato,“ From Basics to Applications of CDMA Technology ”, Realize Inc., pp138-142, December 1997”.

  As described above, the output signal of the adder 5 includes information on all signals arriving from all directions. Therefore, if information extraction is performed only on the output signal of the adder 5, information from all directions can be extracted. Thereby, the information extraction calculation for every antenna element 1-1 to N becomes unnecessary. As a result, the amount of calculation can be reduced to 1 / N compared to the case where the information extraction calculation is performed for each of N antenna elements 1-1 to N having different directivities.

  Information extracted by the searcher unit 6 is input to the control unit 7. The control unit 7 selects a desired wave based on the extracted information. Specifically, for example, it is determined that the signal having the maximum received power is the received signal (desired signal) of the desired wave. Then, the desired signal information such as the PN offset and path timing of the desired signal is output to the reference signal generation unit 8.

  The reference signal generation unit 8 generates a reference signal r for generating a directivity pattern directed to the arrival direction of the desired wave based on the input information of the desired signal. This reference signal r corresponds to the adaptive algorithm of the array weight control unit 3. For example, when the PN sequence defined in the section “TIA / EIA-95-B 7.1.1.3.10 Quadrature Spreading” is used as a reference signal, the PN sequence is input to the PN input from the control unit 7. The reference signal r is generated by delaying by the offset and path timing.

The difference calculator 9 calculates an error signal e between the reference signal r and the array output signal y. This error signal e is input to the array weight control unit 3. Array weight controller 3, by adaptive control as square of the error signal e becomes smaller, the weight w _r1 to w _rN for forming a directivity pattern toward the arrival direction of the desired wave (weight vector A ) Is calculated.

  The adaptive algorithm employed by the array weight control unit 3 is not limited. For example, in addition to the LMS described above, various algorithms such as RLS (Recursive Least Squares) and SMI (Sample Matrix Inversion) can be used.

  Alternatively, the control unit 7 may directly control the array weight control unit 3 based on desired wave information, for example, timing information of a received signal. Accordingly, the present invention can be applied to an adaptive algorithm that does not require a reference signal.

  As described above, according to the present embodiment, even if a directional array antenna is used, an information extraction calculation for each antenna element is unnecessary, and an increase in the amount of calculation can be prevented. As a result, the directional array antenna can be adopted to achieve miniaturization, and it is possible to cope with cost saving and power saving. As a result, it can be applied to various products such as small wireless devices such as portable terminals.

Next, a configuration for weighting the transmission signal by correcting the above-described reception weights w _{r1 to} w _rN (weight vector A) will be described.
Weight correcting unit 11, based on the weight w _r1 to w _rN, it corrects weights to send only the heavy unallocated amount is large directivity direction. FIG. 4 is a flowchart showing this correction procedure.

In FIG. 4, when the weights w _{r1 to} w _rN (weight vector A) are input, the weight correction unit 11 proceeds to step S2 (step S1). Then, among the weights w _r1 to w _rN, records locate a weight which is the maximum weight amount (step S2). Next, a weight having the second largest weight is found and recorded (step S3). Then, it is initialized to zero the weight w _s1 ~w _sN for transmission. Next, the transmission weight corresponding to the weight of the maximum weight amount found in step S2 is set to the maximum value 1 (step S4). Next, the weight value of the next maximum weight amount found in step S2 is compared with the weight value of the maximum weight amount using a threshold value (step S5). As a result, if the ratio between the two is equal to or less than the threshold value, the transmission weight corresponding to the weight of the next maximum weight amount is also set to the maximum value 1 (step S7). Next, transmission weights w _{s1 to} w _sN (weight vector B) are output.

Accordingly, the weight w _s1 to w _sN for transmission, only weights corresponding to the weight weighted distribution amount is larger of the reception weights w _r1 to w _rN is 1, the other weights are set to zero.
The threshold used in step S5 is set to 1 when the number of antenna elements is small (2 to 4), and is set to 1.414 when the number of antenna elements is larger than that, for example. To do.

The weighting transmission unit 12 has the configuration shown in FIG. 5, and weights the transmission signal by multiplying the corresponding weights w _s1 to w sN by the multipliers 21, and then _assigns each weighted transmission signal to the transmission signal. Output to down / up converter 2. The up-converter of the down / up-converter 2 converts the weighted transmission signal (N branch) into a high frequency, amplifies it, and transmits it through the antenna elements 1-1 to N.

The following effects can be obtained by the weight correction described above.
Since the directivity pattern of the antenna unit 1 has already been determined at the design stage, if the reception weight is used for transmission without any correction, a transmission beam directed to the arrival direction of the desired wave should be formed. It is. However, in practice, the accuracy of the transmission beam deteriorates due to variations between transmission circuits provided corresponding to the respective antenna elements.

  In order to cope with this problem, conventionally, a transmission test is performed to obtain a correction value, and calibration is performed. Further, when dealing with the secular change of the transmission circuit element, it is necessary to calibrate periodically, which is very troublesome. However, according to the weight correction of the present embodiment, only the transmission weight corresponding to the arrival direction of the desired wave is set to 1, and the other transmission weights are set to 0, thereby eliminating the influence due to the variation between the transmission circuits. It is possible to prevent deterioration of the accuracy of the transmission beam. This eliminates the need for antenna array calibration.

Next, a second embodiment will be described.
FIG. 6 is a block diagram showing a configuration of an adaptive array antenna system according to the second embodiment of the present invention. In FIG. 6, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
In the configuration of FIG. 6, a high frequency network 30 is provided in the antenna unit 1a. The RF network 30 is adapted to output as the reception output of each antenna element 1-1 to 1-N, the combined signal x ₀ has a function of combining a reception output of each antenna element 1-1 to 1-N outputs To do. The combined signal x ₀ is assumed to include a received signal from all directions. The combined signal x ₀ is input to the searcher 6 through the down converter of the down / up converter 2.

  According to the second embodiment, the high-frequency network 30 corresponds to the adding unit 5 in FIG. 1, and the adding unit 5 is not necessary.

Next, a third embodiment will be described.
FIG. 7 is a block diagram showing a configuration of an antenna unit 1b according to the third embodiment of the present invention. In the third embodiment, only the configuration of the antenna unit is different from the configuration of the second embodiment of FIG. In the configuration of FIG. 7, one omnidirectional antenna 40 is provided in addition to the plurality of antenna elements 1-1 to N having different directivities. The reception output x ₀ of the omnidirectional antenna 40 includes reception signals from all directions. Then, the reception output x ₀ of the omnidirectional antenna 40 is input to the searcher 6 via the down converter of the down / up converter 2.
Also in the third embodiment, the adding unit 5 of FIG. 1 is not necessary.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, the directional array antenna is not limited to the configuration of the above-described embodiment as long as it has a plurality of directional directions and outputs each directional output signal. For example, even when a plurality of omnidirectional antennas are appropriately arranged to form an array antenna and as a result directivity is generated in each antenna element, the array antenna according to the present invention is included.

  Further, the adaptive array antenna system according to the present invention can be applied to a radio apparatus such as a radio base station or a mobile station. As a result, the wireless device can receive or transmit a wireless signal with an appropriate directivity pattern, thereby improving communication quality. Further, downsizing, cost saving, power saving, and the like can be achieved. Examples of the mobile station include a portable wireless terminal such as a mobile phone and a wireless terminal mounted on a moving object such as a car phone.

It is a block diagram which shows the structure of the adaptive array antenna system which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the directivity pattern arrangement | positioning of each directional antenna which concerns on this invention. 3 is a block diagram illustrating a configuration of a weighting synthesis unit 4. FIG. It is a flowchart which shows the weight correction | amendment procedure based on this invention. 3 is a block diagram illustrating a configuration of a weighted transmission unit 12. FIG. It is a block diagram which shows the structure of the adaptive array antenna system which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the antenna part 1b which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a, 1b ... Antenna part, 1-1-N ... Directional antenna element, 3 ... Array weight control part, 4 ... Weighting composition part, 5 ... Adder part, 6 ... Searcher, 7 ... Control part, 8 ... reference Signal generation unit, 11 ... weight correction unit, 12 ... weighting transmission unit, 30 ... high-frequency network, 40 ... omnidirectional antenna.

Claims (7)

An array antenna composed of a plurality of antennas having directivity;
Selection means for selecting a desired wave based on each received signal of the plurality of antennas;
Receiving control means for weighting each received signal received by each of the plurality of antennas in order to form a directivity pattern of the array antenna toward the arrival direction of the desired wave selected by the selecting means; and Transmission control means for weighting each transmission signal transmitted from each of a plurality of antennas,
The transmission control means includes
Of the reception weights for weighting the reception signals in the reception control means, the reception weight that is the maximum weighting amount and the reception weight that is the same weighting amount as the maximum weighting amount, and with a weight of maximum value for transmission corresponding respectively, it like other weight for transmission is zero, the weights for the transmission for weighting each transmission signal respectively set, is the set Weighting each transmission signal by the transmission weight
An adaptive array antenna system characterized by that. An array antenna composed of a plurality of antennas having directivity;
Adding means for adding all received signals of the plurality of antennas;
Detecting means for detecting a desired wave from the signal resulting from the addition by the adding means;
Receiving control means for weighting each received signal received by each of the plurality of antennas in order to form a directivity pattern of the array antenna toward the direction of arrival of the desired wave detected by the detecting means; and Transmission control means for weighting each transmission signal transmitted from each of the plurality of antennas,
The transmission control means includes
Of the reception weights for weighting the reception signals in the reception control means, the reception weight that is the maximum weighting amount and the reception weight that is the same weighting amount as the maximum weighting amount, The transmission weight for weighting each transmission signal is set so that the transmission weight corresponding to each of the transmission signal is the maximum value and the other transmission weights are zero, and the set transmission weight is set. Weighting each transmission signal by
An adaptive array antenna system characterized by that. An array antenna composed of a plurality of antennas having directivity;
One omnidirectional antenna,
Detecting means for detecting a desired wave from a received signal of the omnidirectional antenna;
Receiving control means for weighting each received signal received by each of the plurality of antennas in order to form a directivity pattern of the array antenna toward the direction of arrival of the desired wave detected by the detecting means; and Transmission control means for weighting each transmission signal transmitted from each of the plurality of antennas,
The transmission control means includes
Of the reception weights for weighting the reception signals in the reception control means, the reception weight that is the maximum weighting amount and the reception weight that is the same weighting amount as the maximum weighting amount, The transmission weight for weighting each transmission signal is set so that the transmission weight corresponding to each of the transmission signal is the maximum value and the other transmission weights are zero, and the set transmission weight is set. Weighting each transmission signal by
An adaptive array antenna system characterized by that. An adaptive array antenna system according to any one of claims 1 to 3 , comprising:
A wireless device that performs wireless communication by the adaptive array antenna system. Selecting a desired wave based on each received signal of a plurality of antennas having directivity constituting the array antenna;
Weighting each received signal received by each of the plurality of antennas to form a directivity pattern of the array antenna toward the direction of arrival of the selected desired wave; and Weighting each transmission signal transmitted from each of them,
In the process of weighting each transmission signal,
Of the receiving weights for weighting each received signal, the receiving weight corresponding to the maximum weighting amount and the receiving weight corresponding to the weighting amount equivalent to the maximum weighting amount are respectively supported. A transmission weight for weighting each transmission signal is set so that the transmission weight is the maximum value and the other transmission weights are zero, and each transmission signal is set according to the set transmission weight. Weight
And an adaptive array antenna control method. A process of adding all received signals of a plurality of antennas having directivity constituting an array antenna;
Detecting a desired wave from the signal resulting from the addition;
Weighting each received signal received by each of the plurality of antennas to form a directivity pattern of the array antenna toward the direction of arrival of the detected desired wave; and Weighting each transmission signal transmitted from each of them,
In the process of weighting each transmission signal,
Of the receiving weights for weighting each received signal, the receiving weight corresponding to the maximum weighting amount and the receiving weight corresponding to the weighting amount equivalent to the maximum weighting amount are respectively supported. A transmission weight for weighting each transmission signal is set so that the transmission weight is the maximum value and the other transmission weights are zero, and each transmission signal is set according to the set transmission weight. Weight
And an adaptive array antenna control method. Detecting a desired wave from the received signal of one omnidirectional antenna;
Weighting each received signal received by each of the plurality of antennas to form a directivity pattern of the array antenna toward the direction of arrival of the detected desired wave; and Weighting each transmission signal transmitted from each of them,
In the process of weighting each transmission signal,
Of the receiving weights for weighting each received signal, the receiving weight corresponding to the maximum weighting amount and the receiving weight corresponding to the weighting amount equivalent to the maximum weighting amount are respectively supported. A transmission weight for weighting each transmission signal is set so that the transmission weight is the maximum value and the other transmission weights are zero, and each transmission signal is set according to the set transmission weight. Weight
And an adaptive array antenna control method.

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