Abstract:
The array antenna radio communication apparatus of the present invention combines the outputs of calibration desired signal generator  101  and calibration interference signal generator  102  using combination section  104.  When changing the power of the combined calibration signal, it fixes the power of calibration desired signal to avoid phase rotations due to the power control section and changes only the power of the calibration interference signal by power control section. The array antenna radio communication apparatus supplies this combined calibration signal to a plurality of radio circuits simultaneously or alternately and performs reception processing on only the calibration desired signal by received signal processing section  112  and measures reception characteristics.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to array antenna radio communication apparatuses used in radio communication systems. 
     2. Description of the Related Art 
     An array antenna includes a plurality of antennas and is capable of freely setting reception directivity by adjusting the amplitude and phase of signals received from respective antennas. Adjustments to the amplitude and phase of a received signal can be carried out by multiplying the received signal by a complex coefficient in a received signal processing section. 
     FIG. 1 is a block diagram showing the configuration of a radio communication apparatus equipped with array antennas. FIG. 1 shows an example of communication apparatus with two antenna devices. 
     When communicating with another communication apparatus, this communication apparatus operates as follows. Radio signals are received through reception antennas  4  and  5 . The received radio signals are supplied to reception radio circuits  8  and  9  via switching sections  6  and  7 . As the switching sections here, various means can be used such as cable switching, mechanical switches and electronic switches. The received radio signals are down-converted to base frequency band or intermediate frequency band signals in reception radio circuits  8  and  9  and supplied to received signal processing section  10 . Inside received signal processing section  10 , demodulation processing is performed. The configuration of received signal processing section  10  is determined accordingly by the communication system used. 
     It is possible to selectively receive a certain electromagnetic wave coming from a desired direction with stronger power than other waves by adjusting a complex coefficient to be multiplied inside received signal processing section  10  above. This is called “bearing reception directivity.” By bearing directivity it is possible to keep a reception SIR (Signal to Interference Ratio) high. 
     However, the characteristics of reception radio circuits  8  and  9  vary depending on the circuit because of variations in the characteristics of analog devices such as amplifiers. This adds to the received signal of each antenna unknown different amplitude variations and phase rotations, resulting in the formation of reception directivity different from the expected reception directivity obtained by multiplying a complex coefficient in received signal processing section  10 . 
     In order to prevent such a phenomenon, adjustments need to be made so that the characteristics of reception radio circuits  8  and  9  may be identical. However, it is extremely difficult to adjust the characteristics of analog devices such as amplifiers accurately and in a time-invariable manner. Therefore, instead of adjusting the characteristics of reception radio circuits  8  and  9 , a certain method is adopted by which the characteristics of reception radio circuits  8  and  9  are measured and stored in memory beforehand and a complex coefficient multiplied in received signal processing section  10  is determined by taking into account the fact that the amplitude and phase of the received signal change by the difference in their characteristics. Such an adjustment process is called “calibration.” 
     Calibration is carried out before starting communications to measure the characteristics of the reception radio circuits. The following is an explanation of the calibration method. 
     A calibration signal is generated using calibration signal generator  1 . Then, through power control section  2  such as an attenuator, the power of the calibration signal is controlled. The power-controlled calibration signal above is then distributed by distribution section  3 , supplied to reception radio circuits  8  and  9  via switching sections  6  and  7 . Here, distribution section  3  can be implemented using a distributor capable of supplying two-or more signals or switches that supply only one signal or cable switching. 
     The received signals of the reception radio circuits are observed by received signal processing section  10  and deviations from the expected amplitude and phase of the output signals of reception radio circuits  8  and  9  are stored in a calibration table as the characteristic differences to be corrected at the time of communications. Since the characteristic differences are measured for each reception radio circuit independently, calibration tables are also created independently by the number of reception radio circuits. The calibration tables are incorporated in recording section  11  provided inside or outside received signal processing section  10 . 
     To observe differences in the reception characteristics due to the differences in the power of received signals, their amplitudes are changed by power control section  2  and the same processing is carried out. If distribution section  3  provides only one output at a time, processing is repeated by the number of antenna branches of this communication apparatus. If distribution section  3  supplies a plurality of outputs, calibrations corresponding to a plurality of antenna branches can be carried out simultaneously. 
     Through the processing above, reception calibrations for all antenna branches are completed. Then, the inputs of the reception radio circuits are switched by the switching sections to the reception antennas and communications are started. The received signal processing section carries out processing during communications with reference to the calibration tables so that the recorded characteristic differences of the reception radio circuits may be offset. 
     However, the conventional array antenna communication apparatus above has problems as shown below. 
     In order to observe the differences in the reception characteristics due to the differences in the power of received signals, their amplitudes must be changed by the power control section. However, in the power control section such as an attenuator and variable gain amplifier, controlling the amplitudes may affect signal propagation delay times, causing unexpected phase rotations to be added to the received signals. The phase characteristics of the reception radio circuits measured here result in a combination of phase rotations produced by the reception radio circuits themselves and those produced by the power control section, causing erroneous characteristics to be stored in the calibration tables. This will cause erroneous corrections to be made to the received signals during a communication, preventing correct formation of reception directivity. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide an array antenna radio communication apparatus capable of obtaining accurate reception directivity even if the power of a received signal varies. 
     This objective is achieved by an array antenna radio communication apparatus comprising two calibration signal generators; a calibration desired signal generator and calibration interference signal generator, which controls only the output of the calibration interference signal generator through a power control section and combines this power-controlled calibration interference signal and the calibration desired signal with fixed power into a combined calibration signal using a combination section. 
     When changing the power of the combined calibration signal in this apparatus, the power of the calibration desired signal is fixed by the power control section to avoid phase rotations and only the power of the calibration interference signal is changed by the power control section. 
     This combined calibration signal is supplied to a plurality of radio circuits simultaneously or alternately and reception processing is applied only to the desired signal in the received signal processing section and its reception characteristics are measured. 
     Through such a configuration and operation, the phase of the measured calibration desired received signal will no longer include phase rotations produced by the power control section. This makes it possible to measure the reception characteristics correctly when the power of the received signal varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one example is illustrated by way of example, in which; 
     FIG. 1 is a block diagram showing the configuration of a conventional array antenna radio communication apparatus; 
     FIG. 2 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 1 of the present invention; 
     FIG. 3 is a schematic to explain the operation of the received signal processing section of the array antenna radio communication apparatuses according to Embodiments 1 to 3 of the present invention; 
     FIG. 4 is a block diagram showing the configuration of an array antenna communication apparatus according to Embodiment 2 of the present invention; 
     FIG. 5 is a block diagram showing the configuration of an array antenna communication apparatus according to Embodiment 3 of the present invention; 
     FIG. 6 is a block diagram showing the configuration of an array antenna communication apparatus according to Embodiment 4 of the present invention; 
     FIG. 7 is a schematic to explain the operation of the received signal processing section of the array antenna radio communication apparatuses according to Embodiments 4 to 6 of the present invention; 
     FIG. 8 is a schematic to explain the operation of he received signal processing section of the array antenna radio communication apparatuses according to Embodiments 4 to 6 of the present invention; 
     FIG. 9 is a block diagram showing the configuration of an array antenna communication apparatus according to Embodiment 5 of the present invention; and 
     FIG. 10 is a block diagram showing the configuration of an array antenna communication apparatus according to Embodiment 6 of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the attached drawings, the embodiments of the present invention are explained in detail below. 
     (Embodiment 1) 
     FIG. 2 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 1 of the present invention. 
     The array antenna radio communication apparatus according to the present embodiment comprises calibration desired signal generator  101  and calibration interference signal generator  102 . As calibration interference signal generator  102 , a section capable of generating random noise and non-modulated sine waves, etc. can be used. Power control section  103  adjusts the amplitude of an interference signal from calibration interference signal generator  102 . Actually, an attenuator and variable gain amplifier, etc. may be used as the power control section. 
     Combination section  104  combines the calibration desired signal and calibration interference signal and distribution section  105  distributes the combined signal. As distribution section  105 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  108  and  109  switches between signal input from reception antennas  106  and  107  and calibration signal input. For example, cable switching, mechanical switches or electronic switches, etc. may be used. Reception radio circuits  110  and  111  demodulate the signals switched by switch sections  108  and  109 . Received signal processing section  112  processes the signals using difference values stored in recording section  113 . 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 1 of the present invention is explained using FIG.  2  and FIG.  3 . 
     During a calibration, switching sections  108  and  109  are set so that the output of distribution section  105  may be supplied to reception radio circuits  110  and  111 . First, reception characteristics corresponding to the power of a combined calibration signal at a certain level are measured. 
     Calibration desired signal generator  101  generates a calibration desired signal that can be demodulated by received signal processing  112 . 
     Power generated Pd is fixed at a certain value. In FIG. 3, the value of Pd is illustrated by white bar graph  201 . 
     Calibration interference signal generator  102  generates calibration interference signals such as random noise or non-modulated sine waves which can not always be demodulated by received signal processing section  112 . The power of calibration interference signals is controlled by power control section  103 . Here the signal power at the output of power control section  103  is assumed to be Pi. In FIG. 3, the value of Pi is illustrated by shaded bar graph  202 . 
     A calibration desired signal with signal power Pd and calibration interference signal with signal power Pi are combined by combination section  104  into a combined calibration signal, which in turn is supplied to reception radio circuits  110  and  111  via switching sections  108  and  109 . The power of the combined calibration signal is Pd+Pi at this time. In FIG. 3, the value Pd+Pi is represented by sum  203  of white bar graph  201  and shaded bar graph  202 . 
     Received signal processing section  112  obtains a demodulated signal by demodulating the outputs of reception radio circuits  110  and  111 . Furthermore, received signal processing section  112  operates so that only the calibration desired signal component may be demodulated. At this time, as stated above, the calibration interference signal is not the one that can not necessarily be demodulated by received signal processing section  112 , and thus the calibration interference signal component is superimposed on the demodulated signal as noise. 
     Then, received signal processing section  112  observes the demodulated signal obtained in this way and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  112  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. 
     When illustrated in a logical image drawing, this would be equivalent to placing plot  205  in calibration table  204  in which calibration signal power Pi+Pd is plotted on the horizontal axis and the characteristic difference is plotted on the vertical axis. Since measurements of the characteristic difference are performed independently for each reception radio circuit, calibration tables are also created independently by the number of reception radio circuits. Calibration tables are stored in recording section  113  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration signal. Using power control section  103 , only calibration interference signal power Pi is set to a value expressed by bar graph  206 . At this time, since calibration desired signal power Pd is not changed, Pd is expressed by white bar graph  207  as high as white bar graph  201 . At this time, the combined calibration signal power is Pd+Pi the same as above. In FIG. 3, value Pd+Pi is illustrated by sum  208  of white bar graph  207  and shaded bar graph  206 . 
     Likewise, received signal processing section  112  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  209  in calibration table  204 . 
     Thus, in this calibration method, calibrations are carried out by keeping the calibration desired signal power constant, while increasing the calibration interference signal power. That is, the power of the calibration interference signal is controlled in order to change the total power when creating a calibration table. This means that the difference in the power control section itself is included in (added to) the calibration interference signal. On the other hand, since the calibration interference signal is simply treated as noise by received signal processing section  112 , only the difference of the reception radio circuits can be detected by received signal processing section  112 . Therefore, it is possible to create an accurate calibration table that reflects only the difference of the reception radio circuits. 
     By repeating the above processing, the reception characteristics are measured for all required power of combined calibration signals and data are recorded in calibration tables. This completes the calibration processing. 
     By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  113  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  108  and  109  are set in such a way that the outputs of reception antennas  106  and  107  are supplied to reception radio circuits  110  and  111 . Received signal processing section  112  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     With such a configuration and operation, the phase of the measured calibration desired signal does not include phase rotations (differences) generated by the power control section. This makes it possible to carry out accurate measurements of the reception characteristics when the received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     (Embodiment 2) 
     FIG. 4 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 2 of the present invention. 
     The antenna radio communication apparatus according to the present embodiment comprises calibration desired digital modulated signal generator  301  and calibration interference digital modulated signal generator  302 . Both generators have the same configuration. Power control section  303  adjusts the amplitude of a modulated signal from calibration interference digital modulated signal generator  302 . Actually, an attenuator and variable gain amplifier, etc. may be used as the power control section. 
     Combination section  304  combines the calibration desired digital modulated signal and calibration interference digital modulated signal and distribution section  305  distributes the combined signal. As distribution section  305 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  308  and  309  receive signals from reception antennas  306  and  307 , respectively. For switching sections  308  and  309 , cable switching sections, mechanical switches and electronic switches, etc. may be used. Reception radio circuits  310  and  311  demodulate the signals switched by switch sections  308  and  309 . Received signal processing section  312  processes the signals using difference values stored in recording section  313 . 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 2 of the present invention is explained using FIG.  3  and FIG.  4 . 
     During a calibration, switching sections  308  and  309  are set so that the output of distribution section  305  may be supplied to reception radio circuits  310  and  311 . First, reception characteristics corresponding to the power of a combined calibration signal at a certain level are measured. 
     Calibration desired digital modulated signal generator  301  generates a calibration desired digital modulated signal that can be demodulated by received signal processing  312 . The totality or part of the modulation digital information of the calibration desired digital modulated signal must be known to received signal processing section  312 . Power generated Pd is fixed at a certain value. In FIG. 3, the value of Pd is illustrated by white bar graph  201 . 
     Calibration interference digital modulated signal generator  302  has the same configuration as that of calibration desired digital modulated signal generator  301  and generates calibration interference digital modulated signals different from calibration desired digital modulated signals. The power of calibration interference digital modulated signals is controlled by power control section  303 . Here the signal power at the output of power control section  303  is assumed to be Pi. In FIG. 3, the value of Pi is illustrated by shaded bar graph  202 . 
     A calibration desired digital modulated signal with signal power Pd and calibration interference digital modulated signal with signal power Pi are combined by combination section  304  into a combined calibration digital modulated signal, which in turn is supplied to reception radio circuits  310  and  311  via switching sections  308  and  309 . The power of the combined calibration signal at this time is Pd+Pi. In FIG. 3, the value Pd+Pi is represented by sum  203  of white bar graph  201  and shaded bar graph  202 . 
     Received signal processing section  312  obtains a demodulated signal by demodulating the outputs of reception radio circuits  310  and  311 . Here, only the calibration desired digital modulated signal component needs to be demodulated, but it has the calibration interference digital modulated signal component superimposed on it and it is usually impossible to demodulate it. Therefore, the demodulated signal of the combined calibration digital modulated signal is multiplied by a known modulation digital information series of the calibration interference digital modulated signal and the result is integrated. This makes the calibration interference digital modulated signal component averaged and suppressed, making it possible to extract only the calibration desired digital modulated signal component. 
     Then, received signal processing section  312  observes the demodulated signal obtained in this way and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  312  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. The calibration tables are the same as those in Embodiment 1. The calibration tables are stored in recording section  313  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration signal. Using power control section  303 , only calibration digital modulated interference signal power Pi is changed and set to a value expressed by shaded bar graph  206 . At this time, since calibration digital modulated desired signal power Pd is not changed, Pd is expressed by white bar graph  207  as high as white bar graph  201 . At this time, the combined calibration digital modulated signal power is Pd+Pi the same as above. In FIG. 3, value Pd+Pi is illustrated by sum  208  of white bar graph  207  and shaded bar graph  206 . 
     Likewise, received signal processing section  312  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  209  in calibration table  204 . 
     Thus, in this calibration method, calibrations are carried out by keeping the calibration desired digital modulated signal power constant, while increasing the calibration interference digital modulated signal power. That is, the power of the calibration interference digital modulated signal is controlled in order to change the total power when creating a calibration table. This means that the difference in the power control section itself is only included in the calibration interference digital modulated signal. On the other hand, received signal processing section  312  averages and suppresses the calibration interference digital modulated signal by multiplying the demodulated signal by a modulated digital information series and integrating it. This allows received signal processing section  312  to extract only the calibration desired digital modulated signal component, making it possible to detect the difference only from the reception radio circuits. Therefore, it is possible to create an accurate calibration table that reflects only the difference of the reception radio circuits. 
     By repeating the above processing, the reception characteristics are measured for all required power of combined calibration signals and data are recorded in calibration tables. This completes the calibration processing. 
     By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  313  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  308  and  309  are set in such a way that the outputs of reception antennas  306  and  307  are supplied to reception radio circuits  310  and  311 . Received signal processing section  312  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     With such a configuration and operation, the phase of the measured calibration desired digital modulated signal does not include phase rotations generated by the power control section. This makes it possible to carry out accurate measurements of the reception characteristics when the received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     In addition, since the calibration interference digital modulated signal generator can have the same configuration as that of the calibration desired digital modulated signal generator, it has an advantage that the transmission section inside the communication apparatus can be diverted as the calibration interference digital modulated signal generator eliminating the necessity of providing a dedicated calibration signal generator which can generate random noise. 
     (Embodiment 3) 
     FIG. 5 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 3 of the present invention. 
     The antenna radio communication apparatus according to the present embodiment comprises calibration desired spread spectrum modulated signal generator  401  and calibration interference spread spectrum modulated signal generator  402 . Both generators have the same configuration and carry out spread spectrum modulation using mutually different spreading codes. Power control section  403  adjusts the amplitude of a modulated signal from calibration interference spread spectrum modulated signal generator  402 . It is possible to use an attenuator and variable gain amplifier as the actual power control section. 
     Combination section  404  combines the calibration desired spread spectrum modulated signal and calibration interference spread spectrum modulated signal and distribution section  405  distributes the combined signal. As distribution section  405 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  408  and  409  receive signals from reception antennas  406  and  407 , respectively. For switching sections  308  and  309 , cable switching sections, mechanical switches and electronic switches, etc. may be used. Reception radio circuits  410  and  411  demodulate the signals switched by switch sections  408  and  409 . Received signal processing section  412  processes the signals using difference values stored in recording section  413 .  410  and  411  are reception radio circuits. 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 3 of the present invention is explained using FIG.  3  and FIG.  5 . 
     During a calibration, switching sections  408  and  409  are set so that the output of distribution section  405  may be supplied to reception radio circuits  410  and  411 . First, reception characteristics corresponding to the power of a combined calibration spread spectrum modulated signal at a certain level are measured. 
     Calibration desired spread spectrum modulated signal generator  401  generates a calibration desired spread spectrum modulated signal that can be demodulated by received signal processing  412 . The spreading codes of the calibration desired spread spectrum modulated signal must be known to received signal processing  412 . Power generated Pd is fixed at a certain value. In FIG. 3, the value of Pd is illustrated by white bar graph  401 . 
     Calibration interference spread spectrum modulated signal generator  402  has the same configuration as that of calibration desired spread spectrum modulated signal generator  401  and generates calibration interference spread spectrum modulated signals whose spreading code is different from that of calibration desired spread spectrum modulated signals. The power of calibration interference spread spectrum modulated signals is controlled by power control section  403 . Here the signal power at the output of power control section  403  is assumed to be Pi. In FIG. 3, the value of Pi is illustrated by shaded bar graph  202 . 
     A calibration desired spread spectrum modulated signal with signal power Pd and calibration interference spread spectrum modulated signal with signal power Pi are combined by combination section  404  into a combined calibration spread spectrum modulated signal, which in turn is supplied to reception radio circuits  410  and  411  via switching sections  408  and  409 . The power of the combined calibration spread spectrum modulated signal at this time is Pd+Pi. In FIG. 3, the value Pd+Pi is represented by sum  203  of white bar graph  201  and shaded bar graph  202 . 
     Received signal processing section  412  obtains a demodulated signal by demodulating the outputs of reception radio circuits  410  and  411 . Here, only the calibration desired spread spectrum modulated signal component needs to be demodulated, but since the spreading code of the calibration desired spread spectrum modulated is known to received signal processing section  412 , it is possible to extract the calibration desired spread spectrum modulated signal component by finding correlation with this spreading code and combined calibration spread spectrum modulated signal. 
     Then, received signal processing section  412  observes the demodulated signal obtained in this way and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  412  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. The calibration tables are the same as those in Embodiment 1. The calibration tables are stored in recording section  413  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration spread spectrum modulated signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration spread spectrum modulated signal. Using power control section  403 , only calibration interference signal power Pi is set to a value expressed by shaded bar graph  206 . At this time, since calibration desired spread spectrum modulated signal power Pd is not changed, Pd is expressed by white bar graph  207  as high as white bar graph  201 . At this time, the combined calibration signal power is Pd+Pi. In FIG. 3, value Pd+Pi is illustrated by sum  208  of white bar graph  207  and shaded bar graph  206 . 
     Likewise, received signal processing section  412  records the deviation from the expected value in the reception characteristics in a calibration table as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  209  in calibration table  204 . 
     Thus, in this calibration method, calibrations are carried out by keeping the power of the calibration desired spread spectrum modulated signal constant, while increasing the calibration interference spread spectrum modulated signal power. That is, the power of the calibration interference spread spectrum modulated signal is controlled in order to change the total power when creating a calibration table. This means that the difference in the power control section itself is only included in the calibration interference spread spectrum modulated signal. On the other hand, received signal processing section  412  can extract only the calibration desired spread spectrum modulated signal component by finding correlation between the spreading code and the combined calibration spread spectrum modulated signal, making it possible to detect only the difference of the reception radio circuits. Thus, it is possible to create an accurate calibration table which reflects the difference of only the reception radio circuits. 
     By repeating the above processing, the reception characteristics are measured for all required power of combined calibration spread spectrum modulated signals and data are recorded in calibration tables. This completes the calibration processing. 
     By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  413  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  408  and  409  are set in such a way that the outputs of reception antennas  406  and  407  are supplied to reception radio circuits  410  and  411 . Received signal processing section  412  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     With such a configuration and operation, the phase of the measured calibration desired spread spectrum signal does not include phase rotations generated by the power control section. This makes it possible to carry out accurate measurements of the reception characteristics when the received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     In addition, since the calibration interference spread spectrum modulated signal generator can have the same configuration as that of the calibration desired spread spectrum modulated signal generator, it has an advantage that the transmission section inside the communication apparatus can be diverted as the calibration interference spread spectrum modulated signal generator eliminating the necessity of providing a dedicated calibration signal generator which can generate random noise. 
     Furthermore, since received signal processing section  412  can suppress noise to a small value by adjusting the type and timing of a spreading code so as to reduce the correlation between the spreading code used by the calibration desired spread spectrum modulated signal generator and the spreading code used by the calibration interference spread spectrum modulated signal generator, it is possible to measure the reception characteristic for the calibration desired spread spectrum modulated signal with high precision. 
     (Embodiment 4) 
     In Embodiment 1, calibration desired signal power Pd must be fixed during a calibration. Thus, if characteristic measurement needs to be performed with small combined calibration signal power, it is necessary to set calibration desired signal power Pd to a small value. In this case, when performing characteristic measurements with large combined calibration signal power, the ratio of calibration desired signal power to the calibration interference signal power greatly deteriorates. 
     Embodiment 4 is intended to compensate this drawback so that changing calibration desired signal power Pd according to the required combination signal power may not affect characteristic measurements. 
     FIG. 6 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 4 of the present invention. 
     The array antenna radio communication apparatus according to the present embodiment comprises calibration desired signal generator  500  and calibration interference signal generator  502 . A section that can generate random noise or non-modulated sine waves can be used as calibration interference signal generator  502 . 
     Desired signal power control section  501  adjusts the amplitude of a calibration desired signal from calibration desired signal generator  500 . Interference signal power control section  503  adjusts the amplitude of a calibration interference signal from calibration interference signal generator  502 . It is possible to use an attenuator and variable gain amplifier as the actual power control section. 
     Combination section  504  combines the calibration desired signal and calibration interference signal and distribution section  505  distributes the combined signal. As distribution section  505 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  508  and  509  receive signals from reception antennas  506  and  507 , respectively. For the switching sections, cable switching sections, mechanical switches and electronic switches, etc. may be used. Reception radio circuits  510  and  511  demodulate the signals switched by switch sections  508  and  509 . Received signal processing section  512  processes the signals using difference values stored in recording section  513 . 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 4 of the present invention is explained using FIG. 6 to FIG.  8 . 
     During a calibration, switching sections  508  and  509  are set so that the output of distribution section  505  may be supplied to reception radio circuits  510  and  511 . First, reception characteristics corresponding to the power of a combined calibration signal at a certain level are measured. 
     Calibration desired signal generator  500  generates a calibration desired signal that can be demodulated by received signal processing  512 . Power generated Pd is fixed at a certain value using power control section  501 . In FIG. 7, the value of Pd is illustrated by white bar graph  601 . 
     Calibration interference signal generator  502  generates calibrations interference signals such as random noise and non-modulated sine waves that can not necessarily be demodulated by received signal processing section  512 . The power of calibration interference signals is controlled by power control section  503 . Here the signal power at the output of power control section  503  is assumed to be Pi. In FIG. 7, the value of Pi is illustrated by shaded bar graph  602 . 
     A calibration desired signal with signal power Pd and calibration interference signal with signal power Pi are combined by combination section  504  into a combined calibration signal, which in turn is supplied to reception radio circuits  510  and  511  via switching sections  508  and  509 . The power of the combined calibration signal at this time is Pd+Pi. In FIG. 7, the value Pd+Pi is represented by sum  603  of white bar graph  601  and shaded bar graph  602 . 
     Received signal processing section  512  obtains a demodulated signal by demodulating the outputs of reception radio circuits  510  and  511 . Received signal processing section  512  operates so that only the calibration desired signal component may be demodulated. The calibration interference signal component is superimposed on the demodulated signal as noise. 
     Then, received signal processing section  512  observes the demodulated signal and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  512  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. 
     When illustrated in a logical image drawing, this would be equivalent to placing plot  605  in calibration table A 604  in which calibration signal power Pi+Pd is plotted on the horizontal axis and the characteristic difference is plotted on the vertical axis. Since measurements of the characteristic difference are performed independently for each reception radio circuit, calibration table A 604  is also created independently by the number of reception radio circuits. Calibration table A 604  is stored in recording section  513  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration signal. Using power control section  503 , calibration interference signal power Pi is changed and set to a value expressed by shaded bar graph  602 . At this time, since calibration desired signal power Pd is not changed, Pd is expressed by white bar graph  607  as high as white bar graph  601 . At this time, the combined calibration signal power is Pd+Pi. In FIG. 7, value Pd+Pi is illustrated by sum  608  of white bar graph  607  and shaded bar graph  606 . 
     Likewise, received signal processing section  512  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  609  in calibration table A 604 . 
     Repeating the above processing, the reception characteristic for the required combined calibration signal power with switching point power (Psw)  610  or less is measured and calibration table A 604  is recorded. This completes calibration table A 604 . 
     After calibration table A 604  is completed, the settings of power control section  501  and  503  are changed. Here, combined calibration signal power (Pd+Pi) is set equal to aforementioned switching point power (Psw)  610 . For example, the calibration desired signal power (Pd) which was small until then is increased and the calibration desired signal power (Pd) which was large until then is decreased. Then, in the same way as when calibration table A 604  was created, only the setting of power control section  503  is changed and by changing only the calibration interference signal power, measurements of the reception characteristics are repeated and calibration table B 612  is created in recording section  513 . 
     At this time, combined calibration signal power (Pd+Pi) is not set to the value used when calibration table A 604  was created except switching point power (Psw)  610 . It is naturally possible to provide a recording section apart from recording section  513  in which calibration table A 604  was stored and store calibration table B 612 . The above processing completes calibration table B 612 . 
     Finally, calibration table A 604  and calibration table B 612  are combined into a combined calibration table. The combination method is explained using FIG. 8 below. 
     When calibration table A 701  and calibration table B 702  are superimposed on a same graph, switching point power (Psw) in calibration table A 701  and Psw in calibration table B 702  are shifted. This shift, that is, the difference of the overlapping plots on the vertical axis value is calculated and stored as W. This W is a characteristic variation that appears by changing the setting of power control section  501  on the calibration desired received signal side, not the characteristics of reception radio circuits  510  and  511  and thus it should be compensated and deleted. 
     Combination calibration table  703  is completed by carrying out a parallel translation of all plots of combination calibration table  703  by W. The characteristic curve in the corrected combination calibration table becomes a continuous curve without abrupt drops or falls. 
     As shown above, this calibration method carries out calibrations by increasing the calibration interference signal while keeping the calibration desired signal constant (with power switching). That is, the power of the calibration interference signal is controlled to change the total power when creating a calibration table. Therefore, the difference of the power control section itself is included in the calibration interference signal. On the other hand, since the calibration interference signal is simply handled as noise by received signal processing section  112 , received signal processing section  112  can detect only the difference of the reception radio circuits. Therefore, it is possible to create an accurate calibration table which reflects only the difference of the reception radio circuits. 
     This embodiment showed an example of creating a calibration table by dividing it into two stages A and B, but it is obvious that it is also possible to create a calibration table by dividing it into three stages. 
     This completes the calibration processing. By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  513  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  508  and  509  are set in such a way that the outputs of reception antennas  506  and  507  are supplied to reception radio circuits  510  and  511 . Received signal processing section  512  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     In this embodiment, the phase of the measured calibration desired signal does not include phase rotations generated by the power control section even if the calibration desired signal power is changed. Furthermore, when measuring characteristics with large combined calibration signal power, it is possible to prevent the ratio of calibration desired signal power to the calibration interference signal power from drastically deteriorating. 
     This makes it possible to accurately measure the reception characteristics when received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     (Embodiment 5) 
     In Embodiment 2, calibration desired digital modulated signal power Pd must be fixed during a calibration. Thus, if characteristic measurement needs to be performed with small combined calibration digital modulated signal power, it is necessary to set calibration desired digital modulated signal power Pd to a small value. In this case, when performing characteristic measurements with large combined calibration digital modulated signal power, the ratio of calibration desired digital modulated signal power to the calibration interference digital modulated signal power greatly deteriorates. 
     Embodiment 5 is intended to compensate this drawback so that changing calibration desired digital modulated signal power Pd according to the required combined calibration digital modulated signal power may not affect characteristic measurements. 
     FIG. 9 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 5 of the present invention. 
     The array antenna radio communication apparatus according to the present embodiment comprises calibration desired digital modulated signal generator  800  and calibration interference digital modulated signal generator  802 . Calibration desired digital modulated signal generator  800  and calibration interference digital modulated signal generator  802  have the same configuration. 
     Desired signal power control section  801  adjusts the amplitude of a calibration desired digital modulated signal from calibration desired digital modulated signal generator  800 . Interference digital modulated signal power control section  803  adjusts the amplitude of a calibration interference digital modulated signal from calibration interference digital modulated signal generator  802 . It is possible to use an attenuator and variable gain amplifier as the actual power control section. 
     Combination section  804  combines the calibration desired digital modulated signal and calibration interference digital modulated signal and distribution section  805  distributes the combined signal. As distribution section  805 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  808  and  809  receive signals from reception antennas  806  and  807 , respectively. For switching sections, cable switching sections, mechanical switches and electronic switches, etc. may be used. Reception radio circuits  810  and  811  demodulate the signals switched by switch sections  808  and  809 . Received signal processing section  812  processes the signals using difference values stored in recording section  813 . 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 5 of the present invention is explained using FIG. 7 to FIG.  9 . 
     During a calibration, switching sections  808  and  809  are set so that the output of distribution section  805  may be supplied to reception radio circuits  810  and  811 . First, reception characteristics corresponding to the power of a combined calibration signal at a certain level are measured. 
     Calibration desired digital modulated signal generator  800  generates a calibration desired digital modulated signal that can be demodulated by received signal processing  812 . The totality or part of the modulation digital information of the calibration desired digital modulated signal needs to be known to received signal processing section  812 . Power generated Pd is fixed at a certain value using power control section  801 . In FIG. 7, the value of Pd is illustrated by white bar graph  601 . 
     Calibration interference digital modulated signal generator  802  has the same configuration as that of calibration desired digital modulated signal generator  800  and generates calibrations interference digital modulated signals whose modulation digital information is different from that of the calibration desired digital modulated signal. The power of calibration interference digital modulated signals is controlled by power control section  803 . Here the signal power at the output of power control section  803  is assumed to be Pi. In FIG. 7, the value of Pi is illustrated by shaded bar graph  602 . 
     A calibration desired digital modulated signal with signal power Pd and calibration interference digital modulated signal with signal power Pi are combined by combination section  804  into a combined calibration signal, which in turn is supplied to reception radio circuits  810  and  811  via switching sections  808  and  809 . The power of the combined calibration signal at this time is Pd+Pi. In FIG. 7, the value Pd+Pi is represented by sum  603  of white bar graph  601  and shaded bar graph  602 . 
     Received signal processing section  812  obtains a demodulated signal by demodulating the outputs of reception radio circuits  810  and  811 . Here, it is required that only the component of the calibration desired digital modulated signal be demodulated, but it has the calibration interference digital modulated signal component superimposed on it and it is usually impossible to demodulate it. Therefore, the demodulated signal of the combined calibration digital modulated signal is multiplied by a known modulation digital information series of the calibration interference digital modulated signal and the result is integrated. This makes the calibration interference digital modulated signal component averaged and suppressed, making it possible to extract only the calibration desired digital modulated signal component. 
     Then, received signal processing section  812  observes the demodulated signal obtained in this way and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  812  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. 
     When illustrated in a logical image drawing, this would be equivalent to placing plot  605  in calibration table A 604  in which calibration digital modulated signal power Pi+Pd is plotted on the horizontal axis and the characteristic difference is plotted on the vertical axis. Since measurements of the characteristic difference are performed independently for each reception radio circuit, calibration table A 604  is also created independently by the number of reception radio circuits. Calibration table A 604  is stored in recording section  813  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration digital modulated signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration digital modulated signal. Using the power control section, calibration interference digital modulated signal power Pi is changed and set to a value expressed by shaded graph  602 . At this time, since calibration desired digital modulated signal power Pd is not changed, Pd is expressed by white bar graph  607  as high as white bar graph  601 . The combined calibration signal power at this time is Pd+Pi. In FIG. 7, value Pd+Pi is illustrated by sum  608  of white bar graph  607  and shaded bar graph  606 . 
     Likewise, received signal processing section  812  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  609  in calibration table A 604 . 
     Repeating the above processing, the reception characteristic for the required combined calibration digital modulated signal power with switching point power (Psw)  610  or less is measured and calibration table A 604  is recorded. This completes calibration table A 604 . 
     After calibration table A 604  is completed, the settings of power control section  801  and  803  are changed. Here, combined calibration digital modulated signal power (Pd+Pi) is set equal to aforementioned switching point power (Psw)  610 . For example, the calibration desired digital modulated signal power (Pd) which was small until then is increased and the calibration digital modulated desired signal power (Pd) which was large until then is decreased. Then, in the same way as when calibration table A 604  was created, only the setting of power control section  803  is changed and by changing only the calibration interference digital modulated signal power, measurements of the reception characteristics are repeated and calibration table B 612  is created in recording section  813 . 
     At this time, combined calibration digital modulated signal power (Pd+Pi) is not set to the value used when calibration table A 604  was created except switching point power (Psw)  610 . It is naturally possible to provide a recording section apart from recording section  813  in which calibration table A 604  was stored and store calibration table B 612 . The above processing completes calibration table B 612 . 
     Finally, calibration table A 604  and calibration table B 612  are combined into combined calibration table  614 . The combination method is the same as that in Embodiment 4, and thus its explanation is omitted. 
     As shown above, this calibration method carries out calibrations by increasing the calibration interference digital modulated signal while keeping the calibration desired digital modulated signal constant (with power switching). That is, the power of the calibration interference digital modulated signal is controlled to change the total power when creating a calibration table. Therefore, the difference of the power control section itself is only included in the calibration interference digital modulated signal. On the other hand, the calibration interference digital modulated signal is averaged and suppressed by received signal processing section  812  by multiplying the modulated signal by a modulated digital information series and integrating it. This allows received signal processing section  812  to extract only the calibration desired digital modulated signal component and detect only the difference of the reception radio circuits. Therefore, it is possible to create an accurate calibration table which reflects only the difference of the reception radio circuits. 
     This embodiment showed an example of creating a calibration table by dividing it into two stages A and B, but it is obvious that it is also possible to create a calibration table by dividing it into three stages. 
     This completes the calibration processing. By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  813  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  808  and  809  are set in such a way that the outputs of reception antennas  806  and  807  are supplied to reception radio circuits  810  and  811 . Received signal processing section  812  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     In this embodiment, the phase of the measured calibration desired digital modulated signal does not include phase rotations generated by the power control section even if the calibration desired digital modulated signal power is changed. Furthermore, when measuring characteristics with large combined calibration signal power, it is possible to prevent the ratio of calibration desired digital modulated signal power to the calibration interference digital modulated signal power from drastically deteriorating. 
     This makes it possible to accurately measure the reception characteristics when received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     In addition, since the calibration interference digital modulated signal generator can have the same configuration as that of the calibration desired digital modulated signal generator, it has an advantage that the transmission section inside the communication apparatus can be diverted as the calibration interference digital modulated signal generator, eliminating the necessity of providing a dedicated calibration signal generator which can generate random noise. 
     (Embodiment 6) 
     In Embodiment 3, calibration desired spread spectrum modulated signal power Pd must be fixed during a calibration. Thus, if characteristic measurement needs to be performed with small combined calibration spread spectrum modulated signal power, it is necessary to set calibration desired spread spectrum modulated signal power Pd to a small value. In this case, when performing characteristic measurements with large combined calibration spread spectrum modulated signal power, the ratio of calibration desired spread spectrum modulated signal power to the calibration interference spread spectrum modulated signal power greatly deteriorates. 
     Embodiment 6 is intended to compensate this drawback so that changing calibration desired spread spectrum modulated signal power Pd according to the required combined spread spectrum modulated signal power may not affect characteristic measurements. 
     FIG. 10 is a block diagram showing the configuration of an array antenna radio communication apparatus according to Embodiment 6 of the present invention. 
     The array antenna radio communication apparatus according to the present embodiment comprises calibration desired spread spectrum modulated signal generator  900  and calibration interference spread spectrum modulated signal generator  902 . Calibration desired spread spectrum modulated signal generator  900  and calibration interference spread spectrum modulated signal generator  902  have virtually the same configuration and have mutually different spreading codes. 
     Desired signal power control section  901  adjusts the amplitude of a calibration desired spread spectrum modulated signal from calibration desired spread spectrum modulated signal generator  900 . Interference spread spectrum modulated signal power control section  903  adjusts the amplitude of a calibration interference spread spectrum modulated signal from calibration interference spread spectrum modulated signal generator  902 . It is possible to use an attenuator and variable gain amplifier as the actual power control section. 
     Combination section  904  combines the calibration desired spread spectrum modulated signal and calibration interference spread spectrum modulated signal and distribution section  905  distributes the combined signal. As distribution section  905 , if it is desired to supply two or more signals simultaneously a distributor may be used, and if it is desired to supply only one signal at a time either a switch or a cable switching section may be used. 
     Switching sections  908  and  909  receive signals from reception antennas  906  and  907 , respectively. For switching sections, cable switching sections, mechanical switches and electronic switches, etc. may be used. Reception radio circuits  910  and  911  demodulate the signals switched by switch sections  908  and  909 . Received signal processing section  912  processes the signals using difference values stored in recording section  913 . 
     Since the present embodiment takes as an example, an array antenna radio communication apparatus with an array antenna reception function using two antennas, there are two reception antennas, two switching sections and two reception radio circuits. 
     The operation of the array antenna radio communication apparatus according to Embodiment 6 of the present invention is explained using FIG. 7, FIG.  8  and FIG.  10 . 
     During a calibration, switching sections  908  and  909  are set so that the output of distribution section  905  may be supplied to reception radio circuits  910  and  911 . First, reception characteristics corresponding to the power of a combined calibration spread spectrum modulated signal at a certain level are measured. 
     Calibration desired spread spectrum modulated signal generator  900  generates a calibration desired spread spectrum modulated signal that can be demodulated by received signal processing  912 . The spreading code of the calibration desired spread spectrum modulated signal needs to be known to received signal processing section  912 . Power generated Pd is fixed at a certain value using power control section  901 . In FIG. 7, the value of Pd is illustrated by white bar graph  601 . 
     Calibration interference spread spectrum modulated signal generator  902  has the same configuration as that of calibration desired spread spectrum modulated signal generator  900  and generates calibrations interference spread spectrum modulated signals whose spreading code is different from that of the calibrations desired spread spectrum modulated signal. The power of calibration interference spread spectrum modulated signals is controlled by power control section  903 . Here the signal power at the output of power control section  903  is assumed to be Pi. In FIG. 7, the value of Pi is illustrated by shaded bar graph  602 . 
     A calibration desired spread spectrum modulated signal with signal power Pd and calibration interference spread spectrum modulated signal with signal power Pi are combined by combination section  904  into a combined calibration spread spectrum modulated signal, which in turn is supplied to reception radio circuits  910  and  911  via switching sections  908  and  909 . The power of the combined calibration signal at this time is Pd+Pi. In FIG. 7, the value Pd+Pi is represented by sum  603  of white bar graph  601  and shaded bar graph  602 . 
     Received signal processing section  912  obtains a demodulated signal by demodulating the outputs of reception radio circuits  910  and  911 . Here, it is required that only the component of the calibration desired spread spectrum modulated signal be demodulated, but since the spreading code of the calibration desired spread spectrum modulated signal is known to received signal processing section  912 , it is possible to extract the calibration desired spread spectrum modulated signal by finding correlation between this spreading code and combined calibration spread spectrum modulated signal. 
     Then, received signal processing section  912  observes the demodulated signal and obtains the reception characteristics. The reception characteristics include, for example, the phase and amplitude of the demodulated signal. Received signal processing section  912  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  605  in calibration table A 604  in which calibration spread spectrum modulated signal power Pi+Pd is plotted on the horizontal axis and the characteristic difference is plotted on the vertical axis. Since measurements of the characteristic difference are performed independently for each reception radio circuit, calibration table A 604  is also created independently by the number of reception radio circuits. Calibration table A 604  is stored in recording section  913  provided inside or outside the received signal processing section. 
     This completes a measurement of the reception characteristics for the power of one combined calibration spread spectrum modulated signal. 
     Then, another measurement of the reception characteristics is carried out for the power of another combined calibration spread spectrum modulated signal. Using the power control section, calibration interference spread spectrum modulated signal power Pi is changed and set to a value expressed by shaded bar graph  602 . At this time, since calibration desired spread spectrum modulated signal power Pd is not changed, Pd is expressed by white bar graph  607  as high as white bar graph  601 . The combined calibration signal power at this time is Pd+Pi. In FIG. 7, value Pd+Pi is illustrated by sum  608  of white bar graph  607  and shaded bar graph  606 . 
     Likewise, received signal processing section  912  records the deviation from the expected value in the reception characteristics in calibration table A 604  as a characteristic difference to be corrected at the time of communication. When illustrated in a logical image drawing, this would be equivalent to placing plot  609  in calibration table A 604 . 
     Repeating the above processing, the reception characteristic for the required combined calibration spread spectrum modulated signal power with switching point power (Psw)  610  or less is measured and calibration table A 604  is recorded. This completes calibration table A 604 . 
     After calibration table A 604  is completed, the settings of power control section  901  and  903  are changed. Here, combined calibration spread spectrum modulated signal power (Pd+Pi) is set equal to aforementioned switching point power (Psw)  610 . For example, the calibration desired spread spectrum modulated signal power (Pd) which was small until then is increased and the calibration spread spectrum modulated desired signal power (Pd) which was large until then is decreased. Then, in the same way as when calibration table A 604  was created, only the setting of power control section  903  is changed and by changing only the calibration interference spread spectrum modulated signal power, measurements of the reception characteristics are repeated and calibration table B 612  is created in recording section  913 . 
     At this time, combined calibration spread spectrum modulated signal power (Pd+Pi) is not set to the value used when calibration table A 604  was created except switching point power (Psw)  610 . It is naturally possible to provide a recording section apart from recording section  913  in which calibration table A 604  was stored and store calibration table B 612 . The above processing completes calibration table B 612 . 
     Finally, calibration table A 604  and calibration table B 612  are combined into combined calibration table  614 . The combination method is the same as that in Embodiment 4, and thus its explanation is omitted. 
     As shown above, this calibration method carries out calibrations by increasing the calibration interference spread spectrum modulated signal while keeping the calibration desired spread spectrum modulated signal constant (with power switching). That is, the power of the calibration interference spread spectrum modulated signal is controlled to change the total power when creating a calibration table. Therefore, the difference of the power control section itself is only included in the calibration interference spread spectrum modulated signal. On the other hand, received signal processing section  912  can extract only the calibration desired digital modulated signal component by finding correlation between the spreading code and the combined calibration spread spectrum modulated signal, making it possible to detect only the difference of the reception radio circuits. Thus, it is possible to create an accurate calibration table which reflects the difference of only the reception radio circuits. 
     This embodiment showed an example of creating a calibration table by dividing it into two stages A and B, but it is obvious that it is also possible to create a calibration table by dividing it into three stages. 
     This completes the calibration processing. By the way, if one communication is not immediately followed by another, for example, when only a measurement of the reception radio circuit characteristics is intended, a method of observing the reception characteristics directly from the received signal processing section can be adopted without the need to provide recording section  913  in the apparatus. 
     If one communication is immediately followed by another, the following processing is performed. First, switching sections  908  and  909  are set in such a way that the outputs of reception antennas  906  and  907  are supplied to reception radio circuits  910  and  911 . Received signal processing section  912  carries out such processing that the measured reception characteristics are offset by referencing the calibration tables created by the calibration processing. 
     In this embodiment, the phase of the measured calibration desired spread spectrum modulated signal does not include phase rotations generated by the power control section even if the calibration desired spread spectrum modulated signal power is changed. Furthermore, when measuring characteristics with large combined calibration spread spectrum modulated signal power, it is possible to prevent the ratio of calibration desired spread spectrum modulated signal power to the calibration interference spread spectrum modulated signal power from drastically deteriorating. 
     This makes it possible to accurately measure the reception characteristics when received signal power varies, create accurate calibration tables and obtain accurate reception directivity using those calibration tables. 
     Furthermore, since received signal processing section  912  can suppress noise to a small value by adjusting the type and timing of a spreading code so as to reduce the correlation between the spreading code used by the calibration desired spread spectrum modulated signal generator and the spreading code used by the calibration interference spread spectrum modulated signal generator, it is possible to measure the reception characteristic for the calibration desired spread spectrum modulated signal with high precision. 
     The array antenna radio communication apparatus of the present invention can be used effectively for mobile station apparatuses and base station apparatuses in radio communication systems. 
     As explained above, the array antenna radio communication apparatus of the present invention is capable of accurately measuring reception characteristics when the reception power varies drastically, making it possible to create accurate calibration tables. Therefore, it is possible to obtain accurate reception directivity using such calibration tables. 
     The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention. 
     This application is based on the Japanese Patent Application No.HEI 10-119716 filed on Apr. 28, 1998, entire content of which is expressly incorporated by reference herein.