Method of directional reception using array antenna, and adaptive array antenna unit

[0002] The present invention relates to a directive reception method using an array antenna and an adaptive array antenna apparatus.

[0003] One of directivity antennas used in the digital radio communication field such as CDMA (Code Division Multiple Access) is an adaptive array antenna.

[0004] The adaptive array antenna is an antenna system that allows directivity to be changed by adaptively controlling the amplitude and phase of signals received through a plurality of antennas placed at regular intervals or signals to be transmitted through those antennas according to the communication environment. This provides effects such as enhancing the effect of eliminating interference or selectively receiving only a radio wave coming from a specific direction via a predetermined path, that is, reception based on a RAKE system.

[0005] However, implementing a practical adaptive array antenna requires overcoming numerous problems. In mobile bodies such as automobiles in particular, which change their position each moment, it is not easy to achieve high-speed and high-accuracy adaptation to a communication environment at the same time.

[0006] That is, if a mobile body on the transmitting side is moving, the receiving side must change reception directivity quickly to adapt itself to changes in the communication environment. However, the greater the variation in reception directivity per unit time by attaching importance to high-speed follow-up, the lower the accuracy of convergence to a target control value becomes. On the contrary, attaching importance to the accuracy of convergence may allow accurate convergence to a target control value, but would require longer time to converge.

[0007] Thus, when carrying out adaptive diversity reception, it is an important issue to determine the level of adaptability to the communication environment. However, a mobile body in mobile ratio communications may be stationary or moving slowly or fast and the direction of an incoming radio wave changes all the time, which makes it difficult to implement optimum follow-up to the communication environment.

[0008] It is one of the objectives of the present invention to provide a method and apparatus that will quickly follow up changes in a communication environment in mobile radio communications, etc. and realize accurate directive reception at the same time.

[0009] A directive reception method using an array antenna system of the present invention operates a plurality of diversity reception circuits with different environment follow-up characteristics placed in parallel and selects one of the outputs of the diversity reception circuits as a reception signal. Each of a group of diversity reception circuits with different communication environment follow-up characteristics operates so as to follow up the communication environment and the most appropriate one of the resultant reception signals is selected, achieving high-speed and high-accuracy directive reception.

[0010] A preferred mode of the present invention dynamically updates the environment follow-up characteristics of other diversity reception circuits based on the environment follow-up characteristic of the selected diversity reception circuit. The environment follow-up characteristics can be updated by changing parameter values that determine the environment follow-up characteristics.

[0011] In another preferred mode of the present invention, when changing the values of parameters that determine the environment follow-up characteristics, suppose the value of a basic parameter is μ1, and μA and μB that satisfy a relationship of μA<μ1<μB are obtained and at least one of μA or μB is used as a parameter value of another diversity reception circuit. It is desirable that both μA and μB be values close to μ1. This makes the follow-up performance of a plurality of diversity reception circuits adaptively change while maintaining close correlation with each other, enabling quick formation of desired directivity.

[0012] In still another preferred mode of the present invention, only a diversity reception circuit with high environment follow-up capability is operated in an initial state of directivity formation, then the environment follow-up characteristics of other non-operating diversity reception circuits are updated and their operations started based on its environment follow-up characteristic. This reduces power consumption of the circuits.

[0013] The directive reception mode using the adaptive array antenna of the present invention multiplies reception signals of a plurality of antenna elements by weighting coefficients, then uses a plurality of diversity reception circuits that combine those signals as the reception output to carry out directive reception and selects the optimum signal from the reception signals output in parallel. It is possible to update weighting coefficients step by step and change the environment follow-up characteristic of each diversity reception circuit by changing the amount of update per step. It is desirable that the amount of update per step of the weighting coefficient in a non-selected diversity reception circuit be changed based on the amount of update of the selected diversity reception circuit.

[0014] It is also possible to receive a baseband-spread signal transmitted from a mobile body using the adaptive directive reception method of the present invention and restrain the field intensity of the transmission wave to reduce interference between signals on a same frequency band.

[0015] The directivity communication method using the adaptive array antenna of the present invention not only performs high-speed reception directivity formation by selecting the outputs of a plurality of diversity reception circuits but also carries out directivity transmission using directivity formation information of a selected diversity reception circuit.

[0016] The adaptive array antenna apparatus of the present invention comprises at least one directive reception circuit that selectively receives only radio waves passing through a specific path from among incoming radio waves via a plurality of antenna elements and a plurality of paths. The directive reception circuit comprises a plurality of diversity reception circuits operating in parallel each having a different environment follow-up characteristic and selects the most appropriate output from the outputs of those diversity reception circuits as a reception signal. It is desirable to update the environment follow-up characteristics of diversity reception circuits which have not been selected in every selection. It is also possible to operate only diversity reception circuits with higher environment follow-up performance in an initial stage of the reception directivity formation and make other diversity reception circuits non-operable, thus reducing power consumption of the circuit.

[0017] Another mode of the present invention provides a combination circuit that applies RAKE-combination to the reception outputs of a plurality of directive reception circuits. This makes it possible to increase reception power.

[0018] Still another mode of the present invention also carries out directivity transmission using information to form reception directivity. This improves the communication quality in mobile communications.

[0019] The adaptive array antenna apparatus of the present invention can be used for a CDMA-based communication apparatus and a base station apparatus for CDMA communications.

[0020] FIG. 1 is a block diagram of an embodiment of adaptive array antenna apparatus of the present invention;

[0021] FIG. 2 is a block diagram showing an internal configuration of a directive reception circuit shown in FIG. 1;

[0022] FIG. 3 is a block diagram of another example of directive reception circuit;

[0023] FIG. 4 is a flow diagram showing a characteristic operation of the directive reception circuit in FIG. 3;

[0024] FIG. 5 is a block diagram of another example of directive reception circuit;

[0025] FIG. 6 is a flow diagram showing a characteristic operation of the directive reception circuit in FIG. 5;

[0026] FIG. 7 is a block diagram showing an internal configuration example of a base station apparatus for mobile radio communications;

[0027] FIG. 8 is a flow diagram showing a characteristic operation of the directive reception circuit in FIG. 7;

[0028] FIG. 9 is a block diagram showing an internal configuration example of an adaptive array antenna apparatus with a directivity transmission function;

[0029] FIG. 10 is a flow diagram showing a characteristic operation in directivity transmission of the adaptive array antenna apparatus in FIG. 9; and

[0030] FIG. 11 is a drawing to explain the principle of directive reception of the adaptive array antenna apparatus.

[0031] With reference now to the attached drawings, the embodiments of the present invention are explained below.

[0032] (Embodiment 1)

[0033] FIG. 1 is a block diagram of an adaptive array antenna apparatus of Embodiment 1.

[0034] The adaptive array antenna apparatus outputs a signal resulting from multiplying signals received through a plurality of antenna elements by weighting coefficients Wi (i=1, 2, . . . , n) and finding a sum of them. Even if the antenna elements themselves have no directivity, it is possible to change directivity by adaptively controlling the weighting coefficients. That is, it is possible to create points (null points) without directivity in an arbitrary direction.

[0035] For example, when a desired signal arrives from the direction indicated by reference symbol 701 in FIG. 12 and an interference signal arrives from the direction indicated by reference symbol 702, if reception directivity 703 is directed toward the desired wave, the desired wave is received strongly, while the interference signal is received weakly, which makes it possible to improve the quality of the reception signal.

[0036] In FIG. 1, base station 103 plays a role of a relay in CDMA communications. Base station 103 comprises 4 antennas 104 to 107. Radio waves transmitted through antennas 101 and 102 of mobile station (e.g., automobile) 100 are received using this group of antennas. The radio waves arrive at antennas 104 to 107 via path 1 and path 2.

[0037] The received analog signals are converted to intermediate frequency signals (IF) and amplified in circuit block 108 and inputted to radio signal processing section 109. In the radio signal processing section, demodulation circuit 110 performs quadrature demodulation and the demodulated signals are converted to digital signals by A/D converter 111. The converted digital signals are inputted to directive reception circuits (adaptive diversity reception circuits) 112aand 112b.

[0038] In the present embodiment, directive reception circuit 112ais provided to selectively receive radio waves arriving from mobile station 100 via path 1 and directive reception circuit 112bis provided to selectively receive radio waves arriving from mobile station 100 via path 2.

[0039] In the present embodiment, the signals received by directive reception circuits 112aand 112bare combined by RAKE combination circuit 117 and transmitted to a switched network or another base station via interface circuit 118.

[0040] What is noted here is that directive reception circuits 112aand 112bcomprise a plurality of diversity reception circuits with different communication environment follow-up characteristics and a selector that selects the output of each diversity reception circuit.

[0041] As shown in the figure, directive reception circuit 112acomprises 3 diversity reception circuits 113, 114 and 115 with different communication environment follow-up characteristics and selector 116.

[0042] Each of diversity reception circuits 113 to 115 multiplies a signal received by each of antenna elements 104 to 107 by a weighting coefficient and combines those signals to form desired reception directivity. Selector 116 compares the quality of the combined signals output from the diversity reception circuits and selects the signal with the highest quality.

[0043] FIG. 2 shows an internal configuration of diversity reception circuit 113. Diversity reception circuits 114 and 115 also have the same configuration.

[0044] As shown in the figure, diversity reception circuit 113 (114 and 115) comprises reception directivity control circuit 127, multipliers 120, 121, 122 and 123 that multiply a weighting coefficient output from reception directivity control circuit 127 by the input signals from antennas 104 to 107, adder 124 that combines the outputs of the multipliers, determination circuit 125 that determines the output of adder 124, error detector 126 that detects an error between the output of adder 124 and the determination result of determination circuit 125.

[0045] In diversity reception circuit 113 (114 and 115) with such a configuration, a directivity pattern is formed during reception as follows.

[0046] That is, suppose a signal from each of antennas 104 to 107 is Si(t) in vector expression and a weighting coefficient (weight) output from reception directivity control circuit 127 is Wi, then the output of adder 124 S(t) is expressed in expression (1) below. $\begin{array}{cc}\begin{array}{c}S\left(t\right)=\sum _{i=1}^4\mathrm{Si}\left(t\right)·{\mathrm{Wi}}^{*}\\ =\left[\mathrm{S1},\mathrm{S2},\mathrm{S3},\mathrm{S4}\right]\left[\begin{array}{c}{\mathrm{W1}}^{*}\\ {\mathrm{W2}}^{*}\\ {\mathrm{W3}}^{*}\\ {\mathrm{W4}}^{*}\end{array}\right]={\mathrm{S1W1}}^{*}+{\mathrm{S2W2}}^{*}+{\mathrm{S3W3}}^{*}+{\mathrm{S4W4}}^{*}\end{array}& \left(1\right)\end{array}$

[0047] The asterisk symbols added to W in expression (1) denote conjugate complex numbers.

[0048] Determination circuit 125 determines the output of adder 124. Suppose the determination result is D(t), then error detector 126 outputs the difference (error) between D(t) and S(t) and gives it to reception directivity control circuit 127. Based on this, reception directivity control circuit 127 updates the weighting coefficient (weight) values so as to reduce the error.

[0049] For example, reception directivity control circuit 127 updates the weighting coefficients as shown in expression (2) below.

[0050] W(t+1)=W(t)+μ(D(t)−S(t))*Si(t)  (2)

[0051] If expression (2) is expressed using a matrix, it is expressed as shown in expression (3) below, and therefore the value is updated for every weighting coefficient as shown in expression (4). $\begin{array}{cc}\left[\begin{array}{c}\mathrm{W1}\left(t+1\right)\\ \mathrm{W2}\left(t+1\right)\\ \mathrm{W3}\left(t+1\right)\\ \mathrm{W4}\left(t+1\right)\end{array}\right]=\left[\begin{array}{c}\mathrm{W1}\left(t\right)\\ \mathrm{W2}\left(t\right)\\ \mathrm{W3}\left(t\right)\\ \mathrm{W4}\left(t\right)\end{array}\right]+{\mu \left(D\left(t\right)-S\left(t\right)\right)}^{*}\left[\begin{array}{c}\mathrm{S1}\\ \mathrm{S2}\\ \mathrm{S3}\\ \mathrm{S4}\end{array}\right]& \left(3\right)\\ \begin{array}{c}\begin{array}{c}\mathrm{W1}\left(t+1\right)=\mathrm{W1}\left(t\right)+{\mu \left(D\left(t\right)-S\left(t\right)\right)}^{*}\mathrm{S1}\\ ⋮\end{array}\\ \mathrm{W4}\left(t+1\right)=\mathrm{W4}\left(t\right)+{\mu \left(D\left(t\right)-S\left(t\right)\right)}^{*}\mathrm{S4}\end{array}\}& \left(4\right)\end{array}$

[0052] In expressions (3) and (4), “μ” is an update coefficient of a weighting coefficient and the amount of change by one update of a weighting coefficient depends on this value “μ”. In the present embodiment, this update coefficient μ is changed between diversity reception circuits 113 and 114 that operate in parallel, making each communication environment follow-up characteristic differ. That is, μ is a parameter that decides the environment follow-up characteristic of a directive reception circuit.

[0053] In the paragraphs below, the operation of a diversity reception circuit is explained in detail also taking expressions (1) to (4) above into consideration.

[0054] Diversity reception circuits 113 to 115 each multiply the input signals from antennas 104 to 107 by weighting coefficient (weight) wi, combine them into signals S1(t) to S3(t) and output them. Update coefficients μ of weighting coefficients (weights) in diversity reception circuits 113, 114 and 115 at this time are μ1, μ2 and μ3 and the update coefficient values are values varying in size and having a relationship of μ1<μ2<μ3.

[0055] If the transmitting side (that is, mobile station 100 in FIG. 1) is stopped, output S1(t) of diversity reception circuit 113 corresponding to “μ1” whose weighting coefficient (weight) has high convergence accuracy has the best reception quality, and therefore S1(t) is selected.

[0056] However, once the transmitting side starts moving, following-up with μ1 becomes difficult, and the reception quality of output signal S2(t) of the diversity reception circuit corresponding to μ2 which is greater than μ1 is better. Therefore, selector 116 switches the signal to be selected from S1(t) to S2(t).

[0057] As the transmitting side moves faster, following-up with μ2 also becomes difficult, and output signal S3(t) of diversity reception circuit 115 corresponding to μ3 which has the highest follow-up characteristic is selected.

[0058] As shown above, in the present embodiment, a plurality of diversity reception circuits with different weight update coefficients operate independently and adaptively to the environment, output directive reception signals and select the signal with the best quality. This allows accurate formation of reception directivity adaptable to the direction of incoming radio waves not only when the transmitting side is stopped or moving slowly but also when the mobile body is moving fast and the direction of incoming radio waves changes drastically.

[0059] (Embodiment 2)

[0060] FIG. 3 is a block diagram showing a configuration of the main part of an adaptive array antenna apparatus of Embodiment 2 of the present invention.

[0061] The configuration of directive reception circuit 200 in FIG. 3 is basically the same as that of directive reception circuit 112ain FIG. 1, but directive reception circuit 200 differs in that it is provided with coefficient assignment control circuit 201.

[0062] The following is an explanation of characteristic operations of directive reception circuit 200.

[0063] In the present embodiment, every time selector 117 selects the output of one diversity reception circuit, weights and weight update coefficients of the other two diversity reception circuits are updated based on the weight and weight update coefficient of the selected diversity reception circuit and the selection continues.

[0064] That is, instead of operating in vain a diversity reception circuit which has not been selected by a first selection, its weight and weight update coefficient are adaptively changed so as to output a valid reception signal at the next selection, thus improving the reception accuracy.

[0065] The following is a detailed explanation:

[0066] Diversity reception circuits 113, 114 and 115 multiply the input signals from antennas 104 to 107 by weighting coefficients and combine them and output directive reception signals S1(t), S2(t) and S3(t).

[0067] The weights (weighting coefficients) at diversity reception circuits 113 to 115 at this time are W1, W2 and W3, and the weight update coefficients are μ1, μ2 and μ3, respectively. μ1, μ2 and μ3 have a relationship of μ1<μ2<3.

[0068] Selector 117 finds the reception quality of S1(t), S2(t) and S3(t), compares them and selects signal Si(t) (1≦i≦3) of the best reception quality.

[0069] Then, coefficient assignment control circuit 201 assigns the weight (one of W1 to W3) of the diversity reception circuit corresponding to Si(t) selected by selector 117 to a non-selected diversity reception circuit.

[0070] That is, the weight (weighting coefficients) of the non-selected diversity reception circuit is obviously inappropriate in respect of accurate follow-up to the environment compared to the weight of the selected diversity reception circuit, and as long as the weight remains the same the diversity reception circuit which has not been selected by the first selection is thought to be unable to further output appropriate reception signals. Therefore, once the first selection is made, the weight value of the selected reception circuit is set as the initial value of the weight of the other reception circuits.

[0071] Then, coefficient assignment control circuit 201 finds weight update coefficients μA and μB which have a relationship of μA<μi<μB centered on weight update coefficient μi (i=1, 2 and 3) and assigns μA and μB as the weight update coefficients of the remaining diversity reception circuits. μA and μB are approximate values.

[0072] Weights and weight update coefficients are assigned every time a selection is made. As a result, every time a signal to be selected is changed, weights and weight update coefficients in the non-selected diversity reception circuits are updated.

[0073] That is, if the output of one diversity reception circuit is selected, not only the weight of the diversity reception circuit is set to the other diversity reception circuits, but also μA and μB which have a relationship of μA<μi<μB are assigned as the weight update coefficients of the remaining diversity reception circuits. Coefficient assignment control circuit 201 then detects how the quality of a reception signal changes depending on a difference in the weight update coefficients, starting with the same weight and selects the best one from them, and repeats this procedure so as to make both weights and weight update coefficients dynamically follow up changes in the communication environment.

[0074] The updating operation of weight update coefficients is summarized in FIG. 4.

[0075] That is, coefficient assignment control circuit 201 detects weight update coefficient μi (i=1, 2, 3) for selected Si(t) (step 210), finds μA and μB which satisfy a relationship of μA<μi<μB (step 211), and sets μA and μB in the non-selected diversity reception circuits (step 212).

[0076] According to the present embodiment as described above, every time the output of each diversity reception circuit is selected, it is possible to find a weight update coefficient close to the weight update coefficient centered on the optimum weight update coefficient and assign it to the remaining non-selected diversity reception circuits and make them follow up the moving condition of the transmitting side, thus making it possible to accurately update weighting coefficients.

[0077] (Embodiment 3)

[0078] FIG. 5 is a block diagram showing a configuration of the main part of an adaptive array antenna apparatus of Embodiment 3 of the present invention.

[0079] The basic configuration and operation of the circuit of the present embodiment are the same as those of the aforementioned embodiment. In the present embodiment, however, 2-stage control is performed through the function of operation control circuit 300; first control intended for high-speed convergence and second control intended for accurate convergence.

[0080] A detailed explanation is given below.

[0081] First at the start of a reception operation, operation control circuit 300 operates diversity reception circuit 115 corresponding to weight update coefficient μ3 that converges fast. In the meantime, it stops operation of remaining diversity reception circuits 113 and 114.

[0082] Selector 116 finds the reception quality of output signal S3(t) of diversity reception circuit 115. When a variation per predetermined time of the reception quality obtained is within the range of a preset threshold, control circuit 309 determines that the weight has almost converged.

[0083] Then, it sets the converged weight value as the initial value of diversity reception circuits 113 and 114 that have not been operating so far. It also finds weight update coefficients μ1 and μ2 which have a relationship of μ1<μ2<μ3 and have mutually approximating values, sets them in diversity reception circuits 113 and 114 that have not been operating and starts a directive reception operation. Selector 116 selects the output with the best quality from among the outputs of diversity reception circuits 113 to 115. In this way a directive reception signal has been obtained.

[0084] That is, at least one of a plurality of reception circuits is operated initially, and then the same weight as the weight in the operating reception circuit is set in the other reception circuits. Then, a weight update coefficient which is slightly different from the weight update coefficient of the operating reception circuit is set in the other reception circuits and a reception operation is started. Selector 116 detects how the quality of the reception signal changes depending on a difference in weight update coefficients and selects the best one from among them and repeats this procedure so as to make both weights and weight update coefficients dynamically follow up changes in the communication environment.

[0085] The weight update coefficient change operation is summarized in FIG. 6.

[0086] That is, only the diversity reception circuit with fast converging weight update coefficient μ3 is operated (step 310), and if it converges (step 311), μ1 and μ2 which satisfy a relationship of μ1<μ2<μ3 are selected (step 312), weights of the other diversity reception circuits are updated and a reception operation is started (step 313).

[0087] As shown above, even if the direction of an incoming signal varies drastically when a mobile station moves fast, the present embodiment allows high-speed weight convergence and accurate updating of weights following up changes in the communication environment. Furthermore, in the high-speed follow-up stage, only one diversity reception circuit is operated, which also allows a reduction of power consumption of the circuit.

[0088] (Embodiment 4)

[0089] The present embodiment utilizes the weight update coefficient used for the formation of reception directivity also for the formation of transmission directivity.

[0090] FIG. 7 is a block diagram showing a configuration of a diversity communication apparatus of Embodiment 4 of the present invention.

[0091] In FIG. 7, base station 103 functions as a relay for radio communications between mobile station 100aand mobile station 100b.

[0092] The configuration and operation of the section that performs reception operation are the same as those described in the aforementioned embodiment. That is, weight update coefficients in diversity reception circuits 113 to 115 are μ1, μ2 and μ3, respectively and they have a relationship of μ1<μ2<μ3.

[0093] If mobile station 100aon the transmitting side is stopped, the output of diversity reception circuit 113 corresponding to “μ1” whose weight has high convergence accuracy has the best reception quality, and therefore this is selected. However, once mobile station 100astarts moving, following-up with μ1 becomes difficult, and the output of diversity reception circuit 114 corresponding to μ2 which has a greater weight update coefficient than μ1 is selected. As mobile station 100aon the transmitting side moves faster, the following-up with μ2 also becomes difficult, and thus the output of diversity reception circuit 115 corresponding to μ3 which has the highest follow-up performance is selected. This is the operation of directive reception.

[0094] Then, the operation when directivity is transmitted to mobile station 100ausing a transmission wave with the same frequency as that of the reception wave is explained below.

[0095] In order to perform this directivity transmission, base station 103 comprises transmission signal formation section 400, D/A converter 403, quadrature modulator 404 and transmit amplifier 405.

[0096] Transmission signal formation section 400 comprises baseband spreading circuit 401 and transmit beam forming circuit 402. This transmit beam forming circuit 402 has the function of providing the transmission signal with directivity by multiplying a plurality of signals to be transmitted by weighting coefficients and controlling the amplitude and phase of each signal as in the case of diversity reception circuits 113 to 115.

[0097] In the present embodiment, this transmit beam forming circuit 402 multiplies the transmission signal by the coefficients with the same value as the weight update coefficients used in diversity reception circuits 113 to 115 selected at that time, provides it with transmission directivity so as to achieve the highest reception quality in mobile station 100aand transmits it.

[0098] That is, after the signal with the optimum reception quality is found in the reception section, transmission signal formation section 400 provides a baseband-spread transmission signal with directivity through transmit beam forming circuit 402 using the weight corresponding to the signal selected by selector 116, and transmits it from antennas 104 to 107. The transmission frequency is the same as the reception frequency.

[0099] The characteristic operation in the directivity transmission above is summarized in FIG. 8.

[0100] That is, transmission directivity is formed using the same weight (weighting coefficient) corresponding to the reception signal selected by the selector (step 406), and transmitted from a plurality of antenna elements (step 407).

[0101] As shown above, the present embodiment allows optimum reception to be performed all the time irrespective of the moving condition of the mobile station and allows transmission with the optimum directivity provided for the mobile station, which will improve the communication quality in mobile radio communications.

[0102] (Embodiment 5)

[0103] FIG. 9 is a block diagram showing a configuration of the main part of an adaptive array antenna apparatus of Embodiment 5 of the present invention.

[0104] The configuration and operation of the adaptive array antenna apparatus of the present embodiment are the same as those of the apparatus in Embodiment 4. However, when the frequency of a transmission signal is different from that of a reception signal, the present embodiment differs in that it compensates this frequency difference when providing the transmission signal with directivity.

[0105] That is, transmission signal formation section 506 in the present embodiment comprises beam form convert circuit 515, which converts weights (weighting coefficients) in selected diversity reception circuits 113 to 115 so as to compensate the frequency difference and forms transmission directivity with the converted weights (weighting coefficients).

[0106] The characteristic operation above is summarized in FIG. 10.

[0107] That is, a weight corresponding to a signal selected by the selector is subjected to conversion processing to compensate the frequency difference between the transmission signal and reception signal (step 517), directivity of the transmission signal is formed using the compensated weight (step 518), and the signal is transmitted from a plurality of antenna elements (step 519).

[0108] Even if the frequency of the transmission signal is different from that of the reception signal, this makes it possible to realize optimum reception all the time irrespective of the moving condition of the mobile station and transmit signals to the mobile station with the optimum directivity attached, which will improve the communication quality of mobile radio communications.

[0109] As described above, the present invention can adaptively change reception directivity (and transmission directivity) not only when the mobile station is stopped or moving slowly but also when the mobile station is moving fast and the direction of an incoming radio wave is drastically changing, which improves the communication quality.

[0110] Furthermore, the present invention can perform transmission/reception directivity formation adaptable to changes in the communication environment, realizing optimum reception without increasing the power of transmission radio waves. CDMA communications in which users who are assigned codes use a common frequency band are susceptible to interference. However, carrying out communications with field intensity suppressed can suppress interference of radio waves, resulting in an increase of the number of users who can communicate using the frequency band (communication capacity).

[0111] This application is based on the Japanese Patent Application No.HEI 10-33744 filed on Jan. 30, 1998, entire content of which is expressly incorporated by reference herein.

[0112] Industrial Applicability

[0113] As is obvious from the explanations above, the adaptive array antenna apparatus of the present invention is useful for mobile radio communications, particularly suited to quickly and accurately adapting transmission/reception directivity to changes in the communication environment.