Wireless communication device

BACKGROUND OF THE INVENTION

1. Field of the Invention

0001The present invention relates to wireless communication devices, and more particularly, to a wireless communication device using an adaptive array antenna to perform wireless communication.

2. Description of the Related Art

0002Development of digital cellular wireless communication systems using DS-CDMA (Direct Spread Code Division Multiple Access) technology has been actively pursued since such systems are considered next-generation mobile communication systems enabling wireless multimedia communications.

0003In ordinary wireless communication systems, an adaptive array antenna system has been introduced in anticipation of increase in the subscriber capacity or expansion of the cell radius. The adaptive array antenna system is a system wherein a plurality of antennas are arrayed so that their directivities can be dynamically varied in response to changes in the electromagnetic environment.

0004<figref idref="f0007">FIG. 7</figref> illustrates a schematic configuration of an adaptive array antenna system. The illustrated adaptive array antenna system is a model showing a basic receiving operation thereof and only the elements necessary for explaining the system are shown in the figure.

0005The adaptive array antenna system 10 includes antenna branches 10-1 to 10-4 and a data demodulator 1c. The antenna branches 10-1 to 10-4 respectively comprise antennas 1-1 to 1-4, analog amplifiers 10b-1 to 10b-4, and A/D converters 10c-1 to 10c-4. The data demodulator 1c comprises multipliers 11-1 to 11-4, an adder 12, and a weighting factor setting unit 1c-1.

0006The antennas 1-1 to 1-4 receive radio signals, which are then amplified by the analog amplifiers 10b-1 to 10b-4, respectively, and the A/D converters 10c-1 to 10c-4 convert the respective amplified analog signals to digital signals d1 to d4 (other elements in the individual branches, such as frequency converters, are omitted from the figure).

0007The weighting factor setting unit 1c-1 determines weighting factors in accordance with setting information A, and the multipliers 11-1 to 11-4 respectively multiply the output signals d1 to d4 from the A/D converters 10c-1 to 10c-4 by the weighting factors W1 to W4 set by the weighting factor setting unit 1c-1. The adder 12 adds up the four weighted signals and outputs the resulting signal.

0008Suppose the antennas 1-1 to 1-4 receive a radio signal with an arrival angle φ. In this case, if the phase plane is set using the antenna 1-1 as a reference antenna, the antennas 1-2 to 1-4 receive the radio signal with phase differences λ, 2λ, and 3λ, respectively, because of path differences (the phase difference between adjacent antennas is λ).

0009For the multiplier 11-2 connected to the antenna 1-2, the weighting factor setting unit 1c-1 generates a weighting factor W2 for rotating the phase by λ and sends the factor W2 to the multiplier 11-2, so that the multiplier 11-2 multiplies the signal d2 by the weighting factor W2 to correct the phase difference λ. Also, for the multiplier 11-3 connected to the antenna 1-3, the weighting factor setting unit 1c-1 generates a weighting factor W3 for rotating the phase by 2λ and sends the factor W3 to the multiplier 11-3. Thus, the multiplier 11-3 multiplies the signal d3 by the weighting factor W3 to correct the phase difference 2λ. Further, for the multiplier 11-4 connected to the antenna 1-4, the weighting factor setting unit 1c-1 generates a weighting factor W4 for rotating the phase by 3λ and sends the factor W4 to the multiplier 11-4, whereupon the multiplier 11-4 multiplies the signal d4 by the weighting factor W4 to correct the phase difference 3λ.

0010The multiplications using the respective weighting factors make it possible to cancel out all phase differences λ between the antennas 1-1 to 1-4, allowing the multipliers 11-1 to 11-4 to output signals which are in phase with each other. The adder 12 adds up the in-phase signals, so that signal reception with high gain can be performed.

0011After reaching the antennas 1-1 to 1-4, the radio signal is subjected to analog amplification, A/D conversion, etc., as mentioned above. Nonlinear circuit elements for performing these functions have individually different characteristics, and the characteristics also vary in response to changes in temperature or other environmental conditions as well as with the lapse of time. Therefore, the phase characteristics (phase rotations) of the antenna branches 10-1 to 10-4 are not exactly the same but differ from one to another.

0012Consequently, the antenna branches 10-1 to 10-4 involve their own phase shifts, and if these phase shifts are not removed, the phase differences cannot be completely canceled out, making it impossible to perform the in-phase addition with accuracy.

0013It is therefore necessary to carry out calibration for detecting and removing variations in the phase characteristic among the antenna branches in the system. A circuit for performing such calibration is called calibrator. The calibrator corrects the phase shifts of the individual antenna branches, whereby the antenna outputs can be weighted with accuracy in the data demodulator 1c.

0014As conventional adaptive array antenna techniques, a technique has been proposed in which beamforming is carried out to generate delay profiles for a plurality of beams and a path is detected based on the delay profiles, whereby the scale of circuitry is minimized even in cases where the number of antenna elements is increased (e.g., Unexamined <patcit id="pcit0001" dnum="JP2003283404A"><text>Japanese Patent Publication No. 2003-283404</text></patcit> (paragraph nos. [0022] to [0029], <figref idref="f0001">FIG. 1</figref>)).

0015In adaptive array antenna systems, beamforming is carried out with the beam directivity of the array antenna adaptively controlled such that a narrow beam is directed to a desired station for communication.

0016When signal is transmitted from a base station equipped with an adaptive array antenna to a terminal, the base station carries out DL (Down Link) beamforming in such a manner that the beam directivity is highest in the DoA (Direction of Arrival) which is estimated from the UL (Up Link) signal transmitted from the terminal. A circuit for estimating the arrival direction (arrival angle) at the time of DL beamforming is called adaptive array searcher.

0017Thus, adaptive array antenna systems are provided with the calibrator function and the adaptive array searcher function. In conventional systems, however, the calibrator circuit and the adaptive array searcher circuit are mounted separately, though they include equivalent functional blocks that can be shared, and the equivalent circuit elements are operated at the same time, giving rise to the problem that the scale of the circuitry as well as the power consumption increase.

0018<patcit id="pcit0002" dnum="EP1077504A"><text>European Patent Application Publication Number 1077504</text></patcit> discusses an array antenna used in a transceiver in a time division communication system such as TDD (Time Division Duplex) system, in which the amplitude and phase of each antenna element is calibrated in a transceiver itself during actual communication without using external information. It also describes a first transmitter which has means to send a transmit signal to an antenna element as well as to at least one of the receivers. Other transmitters apart from the first transmitter have means for sending a transmit signal to a related antenna element as well as to a first receiver which relates to the first transmitter. Amplitude/phase values obtained in the first receiver and amplitude/phase values obtained in other receivers, except the first receiver, provide weighted amplitude/phase values of each antenna elements according to desired radiation pattern.

0019<patcit id="pcit0003" dnum="EP0938204A"><text>European Patent Application Publication Number 0938204</text></patcit> describes an array antenna radio receive system comprising an array antenna containing a plurality of antenna elements and a plurality of radio reception units provided for said antenna elements. A calibration signal with substantially the same frequency band as a spread signal used for spread spectrum communications is passed through the radio reception units and the delay characteristic or amplitude characteristic of the radio reception units is detected from the calibration signal that has passed the radio reception units.

0020<patcit id="pcit0004" dnum="US20010031022A"><text>United States Patent Application Publication Number 2001/0031022</text></patcit> relates to a method for generating a reference signal from a modulated signal transmitted to a communications station that includes an array of antenna elements and spatial processing means including: separating from the signals received at the antenna elements a copy signal corresponding to the signal transmitted by a particular remote station using an initial spatial weight vector corresponding to the particular remote station; determining from the terminal copy signal a reference signal having substantially the same frequency offset and time alignment as the received antenna signals; and computing a new spatial weight vector by optimizing a cost function, the cost function using the received antenna signals and the reference signal. For demodulation, the method further includes extracting the symbols of the modulated signal.

0021<patcit id="pcit0005" dnum="US20050113042A"><text>United States Patent Application Publication Number 2005/0113042</text></patcit> relates to a wireless communication receiver which comprises an antenna structure and a joint searcher and channel estimator. The antenna structure acquires dimensionally differentiated signals which are concurrently utilized by the joint searcher and channel estimator for determining both a time of arrival and channel coefficient. The wireless communication receiver can be either a mobile terminal or a network node (e.g., a radio access network node such as a base station node, also called Node-B). In "spatial" embodiments, the antenna structure comprises an array of plural antennas. The signals acquired by different antennas of the array are dimensionally differentiated with regard to a spatial dimension, and the time of arrival and a composite channel coefficient are essentially concurrently determined by the joint searcher and channel estimator.; In "temporal" embodiments, the antenna structure comprises an antenna which provides signals for each of successive sets of pilot data received by the antenna as the dimensionally differentiated signals. In one of its aspects, the joint searcher and channel estimator comprises an antenna signal matrix, a correlator, and an analyzer. Complex values indicative of the dimensionally differentiated signal received in a sampling window are stored in the antenna signal matrix as a function of a sampling window time index and a dimensional differentiation index. The correlator locates value(s) in the antenna signal matrix for use in determining the time of arrival and the channel coefficient. The correlator can utilize non-parametric or parametric techniques for locating "tones" in the antenna signal matrix corresponding to arriving wavefronts. An analyzer uses the value (s) located by the correlator to generate the time of arrival and the channel coefficient.

SUMMARY OF THE INVENTION

0022The present invention was created in view of the above circumstances, and an object thereof is to provide a wireless communication device in which functional blocks common to both of a calibrator and an adaptive array searcher are shared by the two, thus permitting reduction in the scale of circuitry as well as in the power consumption.

0023To achieve the object, there is provided a wireless communication device using an adaptive array antenna to perform wireless communication. The wireless communication device comprises an array of antennas, and an adaptive array searcher for detecting a phase difference between the antennas and estimating a direction of arrival of received radio waves, wherein the adaptive array searcher shares part of circuitry with a calibrator which performs calibration by correcting a phase difference caused between antenna channels in the wireless communication device.

0024The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

0025<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> illustrates the principle of a wireless communication device.</li><li><figref idref="f0002">FIG. 2</figref> shows the circuit configuration of a calibrator and its peripheral elements.</li><li><figref idref="f0003">FIG. 3</figref> shows the circuit configuration of an adaptive array searcher.</li><li><figref idref="f0004">FIG. 4</figref> shows the circuit configuration of the wireless communication device.</li><li><figref idref="f0005">FIG. 5</figref> shows the configuration of a DoA information selector.</li><li><figref idref="f0006">FIG. 6</figref> shows the configuration of another DoA information selector.</li><li><figref idref="f0007">FIG. 7</figref> shows a schematic configuration of an adaptive array antenna system.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0026Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals refer to like elements throughout. <figref idref="f0001">FIG. 1</figref> illustrates the principle of a wireless communication device. The wireless communication device 1 comprises an array of antennas 1-1 to 1-n, an adaptive array searcher 1a, and a data demodulator 1c.

0027The adaptive array searcher 1a detects the phase difference between the antennas 1-1 to 1-n and estimates the direction of arrival of received radio waves. The data demodulator 1c includes a weighting factor setting unit 1c-1. The weighting factor setting unit 1c-1 sets weighting factors for weighting the outputs of the respective antennas 1-1 to 1-n so that the data demodulator 1c can demodulate received data (user data) received by the antennas 1-1 to 1-n.

0028The adaptive array searcher 1a shares part of circuitry with a calibrator 1b which performs calibration by correcting the phase difference caused between antenna channels (identical in meaning to the aforementioned antenna branches) in the wireless communication device. Thus, the adaptive array searcher 1a has a calibration function incorporated therein (details of the circuit configuration will be described later with reference to <figref idref="f0004">FIG. 4</figref>).

0029The following describes the circuit configuration and operation of the calibrator as a self-contained functional unit. <figref idref="f0002">FIG. 2</figref> shows the circuit configuration of the calibrator and its peripheral elements. The calibrator 3 is connected with a reference signal coupler 20 through receivers 23-1 to 23-4. The reference signal coupler 20 comprises a reference signal distributor (power divider) 21 and directional couplers 22-1 to 22-4.

0030The calibrator 3 comprises a reference signal generator 31, multipliers 32-1 to 32-4, matched filters 33a to 33d, a combiner 34, multipliers 35a to 35c, a calibration timing calculator 36, a synchronization timing determiner 37, a buffer 38, and an averaging unit 39.

0031The reference signal generator 31 outputs a reference signal which is used as a basis for performing calibration. For the reference signal, a spread signal (PN (Pseudo Noise) code) is used. The reference signal distributor 21 divides the power of the received reference signal into four reference signals, which are sent to the respective directional couplers 22-1 to 22-4.

0032The directional coupler 22-1 allows the reference signal to be introduced to a line L1 connected to the antenna 1-1 and outputs the reference signal to the receiver 23-1. Similarly, the directional couplers 22-2 to 22-4 allow the reference signals to enter lines L2 to L4 connected to the antennas 1-2 to 1-4, respectively, and output the reference signals to the respective receivers 23-2 to 23-4.

0033The reference signal input to each of the directional couplers 22-1 to 22-4 is a spread signal and, therefore, is only a very small noise for the radio signal received by the antennas 1-1 to 1-4. Accordingly, the reference signal, if coupled with the radio signal from the antennas 1-1 to 1-4 by the directional couplers 22-1 to 22-4, does not affect the subsequent process, permitting calibration to be performed during the operation.

0034The receivers 23-1 to 23-4 receive the reference signals and send the received signals to the respective multipliers 32-1 to 32-4. The output signal from each of the multipliers 32-1 to 32-4 is split into two, one being sent to the adaptive array searcher shown in <figref idref="f0003">FIG. 3</figref> and the other to a corresponding one of the matched filters 33a to 33d.

0035In response to a calibration timing signal tc output from the synchronization timing determiner 37, the matched filters 33a to 33d acquire synchronization between the reference signals of the respective antenna channels and the known reference signal pattern, and output demodulated signals (reference signal delay profiles) a1 to a4, respectively. The combiner 34 combines the demodulated signals a1 to a4 and provides a composite signal as its output.

0036On receiving the composite signal, the calibration timing calculator 36 calculates a timing (corresponding to despreading timing for the reference signal) at which the power of the composite signal is highest (at its peak) within a fixed interval. When supplied with the timing calculated by the calibration timing calculator 36, the synchronization timing determiner 37 generates a calibration timing signal tc for determining the reference signal with a timing that has the highest peak among the reference signal delay profiles, and sends the signal tc to the matched filters 33a to 33d for the purpose of symbol synchronization of the reference signals.

0037The multiplier 35a multiplies the demodulated signals a1 and a2 together to obtain a product signal m2 indicative of a phase difference between the phase characteristics of the channels of the antennas 1-1 and 1-2, and sends the signal m2 to the buffer 38. The multiplier 35b multiplies the demodulated signals a2 and a3 together to obtain a product signal m3 indicative of a phase difference between the phase characteristics of the channels of the antennas 1-2 and 1-3, and sends the signal m3 to the buffer 38. The multiplier 35c multiplies the demodulated signals a3 and a4 together to obtain a product signal m4 indicative of a phase difference between the phase characteristics of the channels of the antennas 1-3 and 1-4, and sends the signal m4 to the buffer 38.

0038The averaging unit 39 averages the product signals m2 to m4 supplied thereto via the buffer 38, and generates weighting factors wc2 to wc4 for calibration. The weighting factors wc2, wc3 and wc4 are sent to the multipliers 32-2, 32-3 and 32-4, respectively.

0039The multiplier 32-2 multiplies the user data by the weighting factor wc2, to correct the phase difference caused by the circuit elements in the channel of the antenna 1-2. The multiplier 32-3 multiplies the user data by the weighting factor wc3, to correct the phase difference caused by the circuit elements in the channel of the antenna 1-3. The multiplier 32-4 multiplies the user data by the weighting factor wc4, to correct the phase difference caused by the circuit elements in the channel of the antenna 1-4.

0040In the illustrated example, the phase of the antenna channel 1-1 is used as a reference phase. Specifically, the phases of the antennas 1-2 to 1-4 are made to coincide with that of the antenna 1-1, to thereby remove the phase difference between the antenna channels. Accordingly, the multiplier 32-1 is not applied with a weighting factor wc1 for phase difference correction (no phase rotation is given with respect to the antenna 1-1).

0041The following describes the circuit configuration and operation of the adaptive array searcher as a self-contained functional unit. <figref idref="f0003">FIG. 3</figref> shows the circuit configuration of the adaptive array searcher. The adaptive array searcher 4 comprises matched filters 4-1 to 4-4, a timing calculation controller 40, a DoA (Direction of Arrival) calculator 50, and a demodulator interface 60.

0042The timing calculation controller 40 includes a buffer 41, multipliers 42-1 to 42-4, an in-phase combiner 43, and a timing calculator 44. The DoA calculator 50 includes multipliers 51a to 51c, an in-phase combiner 52, a DoA information generator 53, a DoA profile memory 54, a DoA/weighting factor converter 55, and a DoA information selector 56.

0043The adaptive array searcher 4 is supplied with the user data of which the phase difference between the antenna channels has been canceled out by the preceding calibrator 3; therefore, the adaptive array searcher 4 may simply estimate the DoA based on the phase difference actually caused between the antennas. In order to estimate the DoA, the phase difference between the antennas has only to be detected (in <figref idref="f0007">FIG. 7</figref>, for example, detecting the phase difference λ between the antennas is equivalent to estimating the arrival direction (arrival angle φ)).

0044By matching the received user data against the known data pattern, the matched filters 4-1 to 4-4 calculate instantaneous values of user data delay profiles, to generate user data-demodulated signals b1 to b4. The demodulated signals b1 to b4 are each split into two, one being sent to the buffer 41 in the timing calculation controller 40 and the other being sent to a corresponding one of the multipliers 51a to 51c in the DoA calculator 50.

0045The multiplier 51a multiplies the demodulated signals b1 and b2 together and outputs the phase difference λ1 between the antennas 1-1 and 1-2. The multiplier 51b multiplies the demodulated signals b2 and b3 together and outputs the phase difference λ2 between the antennas 1-2 and 1-3. The multiplier 51c multiplies the demodulated signals b3 and b4 together and outputs the phase difference λ₃ between the antennas 1-3 and 1-4.

0046The in-phase combiner 52 combines the phase differences λ1 to λ3 in phase with each other and outputs a single phase difference signal. The three phase differences λ1 to λ3 between adjacent antennas ideally assume the same value λ. In practice, however, the phase differences involve error because of noise or the like, and therefore, the phase differences are combined by the in-phase combiner 52 into a single phase difference signal.

0047The DoA information generator 53 averages n phase difference signals (λ₁ to λ_n) derived in one symbol interval, to generate DoA information corresponding to one symbol of the received data. The DoA profile memory 54 stores the DoA information. The DoA/weighting factor converter 55 converts the DoA information to weighting factors.

0048The buffer 41 stores the demodulated signals b1 to b4 demodulated by the matched filters 4-1 to 4-4. The demodulated signals b1 to b4 are read from the buffer 41 after the DoA information corresponding to the demodulated signals b1 to b4 is created and then stored in the DoA profile memory 54. The multipliers 42-1 to 42-4 respectively multiply the signals output from the buffer 41 by the weighting factors received from the DoA/weighting factor converter 55 and output the resulting product signals. The in-phase combiner 43 combines the product signals in phase with each other and outputs a composite signal. The timing calculator 44 detects the timing (corresponding to despreading timing for the user data) at which the power of the composite signal is at its peak, and supplies the resulting user data timing signal td to the demodulator interface 60 and the DoA information selector 56.

0049The DoA information selector 56 selects DoA information matching the timing of the user data timing signal td, from among the DoA information received from the DoA profile memory 54, and sends the selected DoA information D1 to the demodulator interface 60. On receiving the user data timing signal td and the selected DoA information D1 (more specifically, information showing the phase difference λ between the antennas), the demodulator interface 60 sends the signal td and the information D1 to the succeeding data demodulator 1c shown in <figref idref="f0001">FIG. 1</figref>. Since the user data timing signal td shows the despreading timing for the user data, the data demodulator 1c can demodulate the received user data at that timing. Also, the weighting factor setting unit 1c-1 can calculate weighting factors based on the selected DoA information D1 (λ).

0050The following describes the circuit configuration and operation of the wireless communication device 1 of the present invention in which the calibrator 3 shown in <figref idref="f0002">FIG. 2</figref> is incorporated into the adaptive array searcher 4 shown in <figref idref="f0003">FIG. 3</figref>. <figref idref="f0004">FIG. 4</figref> shows the circuit configuration of the wireless communication device 1.

0051The wireless communication device 1 includes antennas 1-1 to 1-4, a reference signal coupler 20, receivers 23-1 to 23-4, an adaptive array searcher 1a, and a data demodulator 1c. The adaptive array searcher 1a comprises a reference signal generator 31, matched filters c0-1 to c0-4, multipliers 32-1 to 32-4, a timing calculation controller 40, a DoA calculator 50, a demodulator interface 60, a selector 70, a synchronization controller 71, and a calibration controller 1b-1.

0052The timing calculation controller 40 is made up of a buffer 41, multipliers 42-1 to 42-4, an in-phase combiner c2, and a timing calculator c3. The DoA calculator 50 is constituted by multipliers c1-1 to c1-3, an in-phase combiner 52, a DoA information generator 53, a DoA profile memory 54, a DoA/weighting factor converter 55, and a DoA information selector 56. The calibration controller 1b-1 comprises a calibration weight information generator 3a, a buffer 38, and an averaging unit 39.

0053Main circuit blocks that are shared by the calibrator 3 shown in <figref idref="f0002">FIG. 2</figref> and the adaptive array searcher 4 shown in <figref idref="f0003">FIG. 3</figref> are the matched filters c0-1 to c0-4, the multipliers c1-1 to c1-3 (phase difference detector), the in-phase combiner c2, and the timing calculator c3.

0054Calibration of the wireless communication device 1 will be now described. The reference signal generator 31 outputs a reference signal (spread signal) which is used as a basis for performing the calibration. The reference signal coupler 20 divides the power of the received reference signal into four reference signals corresponding in number to the antennas 1-1 to 1-4, and causes the reference signals to enter respective lines L1 to L4 by means of directional couplers included therein.

0055The receivers 23-1 to 23-4 receive the reference signals and send the received signals to the matched filters c0-1 to c0-4, respectively. The matched filters c0-1 to c0-4 acquire synchronization between the reference signals of the respective antenna channels and the known reference signal pattern, to generate demodulated reference signals (reference signal delay profiles), which are sent to the respective multipliers 32-1 to 32-4. The output signals from the multipliers 32-1 to 32-4 are each split into two, one being sent to the buffer 41 of the timing calculation controller 40 and the other being sent to a corresponding one of the multipliers c1-1 to c1-3 in the DoA calculator 50.

0056The signals output to the buffer 41 from the multipliers 32-1 to 32-4 are then sent via the multipliers 42-1 to 42-4 to the in-phase combiner c2. The in-phase combiner c2 combines the demodulated reference signals and outputs the resulting composite signal.

0057When supplied with the composite signal, the timing calculator c3 calculates the timing (corresponding to despreading timing for the reference signal) at which the power of the composite signal is highest (at its peak) in a fixed interval, and sends the resulting reference timing signal tc to the calibration weight information generator 3a.

0058On the other hand, the multiplier c1-1 multiplies the demodulated reference signals output from the multipliers 32-1 and 32-2, and sends the resulting product signal, which indicates the phase difference between the phase characteristic of the channels of the antennas 1-1 and 1-2, to the buffer 38. The multiplier c1-2 multiplies the demodulated reference signals output from the multipliers 32-2 and 32-3, and sends the resulting product signal, which indicates the phase difference between the phase characteristics of the channels of the antennas 1-2 and 1-3, to the buffer 38. The multiplier c1-3 multiplies the demodulated reference signals output from the multipliers 32-3 and 32-4, and sends the resulting product signal, which indicates the phase difference between the phase characteristics of the channels of the antennas 1-3 and 1-4, to the buffer 38.

0059In response to the reference timing signal tc output from the timing calculator c3, the calibration weight information generator 3a generates calibration weight information (calibration weighting factor Wc) on the basis of the received product signals, and sends the generated information to the DoA information selector 56. Also, in response to the reference timing signal tc, the calibration weight information generator 3a sends the product signals received from the buffer 38 to the averaging unit 39.

0060On receiving the product signals sent from the calibration weight information generator 3a in response to the reference timing signal tc, the averaging unit 39 averages the product signals and generates calibration weighting factors wc2 to wc4. The weighting factor wc2 is sent to the multiplier 32-2, the weighting factor wc3 to the multiplier 32-3, and the weighting factor wc4 to the multiplier 32-4.

0061The multiplier 32-2 multiplies the user data by the weighting factor wc2 to correct the phase difference caused by the circuit elements in the channel of the antenna 1-2. The multiplier 32-3 multiplies the user data by the weighting factor wc3 to correct the phase difference caused by the circuit elements in the channel of the antenna 1-3. The multiplier 32-4 multiplies the user data by the weighting factor wc4 to correct the phase difference caused by the circuit elements in the channel of the antenna 1-4.

0062In the illustrated example, the phase of the antenna channel 1-1 is used as a reference phase. Specifically, the phases of the antenna channels 1-2 to 1-4 are made to coincide with that of the antenna channel 1-1, to thereby remove the phase difference between the antenna channels. Accordingly, the multiplier 32-1 is not applied with a weighting factor for phase difference correction.

0063DoA estimation by the wireless communication device 1 will be now described. The receivers 23-1 to 23-4 subject the radio signals received by the antennas 1-1 to 1-4 to amplification, down-conversion, etc., and supply the resulting signals to the respective matched filters c0-1 to c0-4 as user data.

0064By matching the user data against the known data pattern, the matched filters c0-1 to c0-4 calculate instantaneous values of user data delay profiles, to generate user data-demodulated signals (demodulated user signals): The demodulated user signals are sent to the respective multipliers 32-1 to 32-4 and are each split into two at the output stage of same, one being sent to the buffer 41 in the timing calculation controller 40 and the other being sent to a corresponding one of the multipliers c1-1 to c1-3 in the DoA calculator 50.

0065The multiplier c1-1 multiplies the demodulated user signals output from the multipliers 32-1 and 32-2, and outputs the phase difference λ1 between the antennas 1-1 and 1-2. The multiplier c1-2 multiplies the demodulated user signals output from the multipliers 32-2 and 32-3, and outputs the phase difference λ₂ between the antennas 1-2 and 1-3. The multiplier c1-3 multiplies the demodulated user signals output from the multipliers 32-3 and 32-4, and outputs the phase difference λ3 between the antennas 1-3 and 1-4.

0066The in-phase combiner 52 combines the phase differences λ1 to λ3 in phase with each other and outputs a single phase difference signal. The three phase differences λ1 to λ3 ideally assume the same value λ. In practice, however, the phase differences involve error because of noise or the like, and therefore, the phase differences are combined by the in-phase combiner 52 into a single phase difference signal.

0067The DoA information generator 53 averages the phase difference signals derived in one symbol interval and generates multiple items of DoA information corresponding to one symbol interval of the received data. The DoA profile memory 54 stores the DoA information. The DoA/weighting factor converter 55 converts the DoA information to weighting factors.

0068The buffer 41 stores the demodulated user signals demodulated by the matched filters c0-1 to c0-4. The demodulated user signals are output from the buffer 41 after the DoA information corresponding to the demodulated user signals is generated and then stored in the DoA profile memory 54.

0069The synchronization controller 71 (which may be implemented by the synchronization timing determiner 37 of the calibrator 3) generates, in response to an external signal, not shown, transmitted thereto from a host, a synchronization timing signal t1 for switching operation between the calibration and the DoA estimation, and sends the generated signal t1 to the selector 70. On receiving the synchronization timing signal t1 from the synchronization controller 71, the selector 70 sends the weighting factors, received from the DoA/weighting factor converter 55, to the multipliers 42-1 to 42-4.

0070The multipliers 42-1 to 42-4 respectively multiply the signals output from the buffer 41 by the weighting factors received from the DoA/weighting factor converter 55 via the selector 70, and output the resulting product signals. The in-phase combiner c2 combines the product signals in phase with each other and outputs a composite signal. The timing calculator c3 detects the timing (corresponding to despreading timing for the user data) at which the power of the composite signal is at its peak, and supplies the detected timing, as the user data timing signal td, to the demodulator interface 60 and the DoA information selector 56.

0071The DoA information selector 56 selects DoA information matching the timing of the user data timing signal td, from among the DoA information received from the DoA profile memory 54, and sends the selected DoA information D1 to the demodulator interface 60. On receiving the user data timing signal td and the selected DoA information D1 (more specifically, information showing the phase difference λ between the antennas), the demodulator interface 60 generates setting information A (the contents of the setting information A will be described later with reference to <figref idref="f0005">FIGS. 5</figref> and <figref idref="f0006">6</figref>), and sends the generated information A to the data demodulator 1c. Since the user data timing signal td shows the despreading timing for the user data, the data demodulator 1c can demodulate the received user data at that timing. Also, the weighting factor setting unit 1c-1 can calculate weighting factors based on the selected DoA information D1 (λ).

0072Although not shown in <figref idref="f0004">FIG. 4</figref>, the data demodulator 1c also receives the user data (corresponding to the signals d1 to d4 in <figref idref="f0007">FIG. 7</figref>) output from the receivers 23-1 to 23-4. In accordance with the setting information A, the weighting factor setting unit 1c-1 in the data demodulator 1c weights the user data, namely, the antenna outputs.

0073The configuration of the DoA information selector 56 will be now described with reference to <figref idref="f0005">FIG. 5</figref>. As shown in the figure, the DoA information selector 56-1 includes an internal selector 56a. The internal selector 56a receives the user data timing signal (despreading timing information for the user data) td output from the timing calculator c3 as well as the DoA information output from the DoA profile memory 54, and sends the DoA information matching the timing of the user data timing signal td to the demodulator interface 60 as the selected DoA information D1. Also, the DoA information selector receives the calibration weighting factor Wc output from the calibration weight information generator 3a and passes same through to the demodulator interface 60.

0074On receiving the setting information A (selected DoA information D1 + calibration weighting factor Wc) via the demodulator interface 60, the weighting factor setting unit 1c-1 in the data demodulator 1c calculates weighting factors W1 to W4 for correcting the phase difference between the antennas 1-1 to 1-4, as shown in <figref idref="f0007">FIG. 7</figref>, and sends the weighting factors W1 to W4 to the respective multipliers 11-1 to 11-4 to correct the phase difference between the antennas.

0075<figref idref="f0006">FIG. 6</figref> shows the configuration of another DoA information selector. The DoA information selector 56-2 includes an internal selector 56a and a multiplier 56b. The internal selector 56a receives the user data timing signal (despreading timing information for the user data) td output from the timing calculator c3 as well as the DoA information output from the DoA profile memory 54, and outputs, as the selected DoA information D1, the DoA information matching the timing of the user data timing signal.

0076The multiplier 56b multiplies the selected DoA information D1 by the calibration weighting factor Wc output from the calibration weight information generator 3a to generate weighting factors W1 to W4 for correcting the post-calibration phase difference between the antennas, and sends the calculated weighting factors to the demodulator interface 60.

0077On receiving the weighting factors W1 to W4 as the setting information A via the demodulator interface 60, the weighting factor setting unit 1c-1 in the data demodulator 1c sends the weighting factors W1 to W4 to the respective multipliers 11-1 to 11-4, as shown in <figref idref="f0007">FIG. 7</figref>, to correct the phase difference between the antennas 1-1 to 1-4. In this manner, the wireless communication device may be configured such that up to the calculation of the weighting factors for correcting the phase difference between the antennas 1-1 to 1-4 is performed by the adaptive array searcher 1a and that only the calculation results are sent to the data demodulator 1c.

0078In the wireless communication device of the present invention, the adaptive array searcher for estimating the direction of arrival of received radio waves shares part of circuitry with the calibrator for correcting the phase difference caused between the antenna channels in the wireless communication device and thus has a calibration function incorporated therein. Since the calibrator and the adaptive array searcher share equivalent functional blocks, the scale of the circuitry as well as the power consumption can be cut down.

0079The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described.