Patent Publication Number: US-10330775-B2

Title: Transmitter, transmission method, phase adjustment device, and phase adjustment method

Description:
TECHNICAL FIELD 
     The present invention relates to a transmitter, a transmission method, a phase adjustment device, and a phase adjustment method. 
     BACKGROUND ART 
     In wireless communication, a technology of controlling the emission direction of a transmission wave emitted form an antenna has been developed. Such a technology is referred to as beam forming. In the beam forming, transmission waves the phases of which are different from one another are emitted from the respective ones of a plurality of antennas. A plurality of transmission waves emitted from the plurality of antennas strengthen one another by having the same phase in a specific direction and weaken one another by having the reverse phases to cancel one another in another direction. Using the above phenomenon, the beam forming is capable of performing control of emitting transmission waves concentrated on any desired direction or emitting no transmission wave in any desired direction. 
     In the description of the present invention, the beam forming will be described mainly from the standpoint of transmitting carrier waves. However, from the standpoint of receiving transmission waves, the beam forming is also capable of performing control of receiving a transmission wave transmitted from any desired direction in a strengthening manner and not receiving any transmission wave transmitted from another direction. 
     In the above-described beam forming, it is required to appropriately select a phase of a transmission wave transmitted from each antenna and to control the state thereof. In order to control a phase, using a transmitter including a phase shifter is conceivable. 
       FIG. 6  is a functional block diagram exemplifying a known transmitter including the phase shifter  101 . Transmitters  100   a  and  100   b  illustrated in  FIG. 6  make phase shifters  101  shift the phases of respective transmission waves generated by a signal source  109 , and, via power amplifiers  107 , supply antennas  103  with the phase-shifted transmission waves. The antennas  103  transmit the transmission waves amplified by the power amplifiers  107 . Phase shift amounts in the phase shifters  101  are determined in accordance with phase control signals output from not-illustrated control circuits. 
     Switching the emission directions of transmission waves dynamically using the transmitters  100   a  and  100   b  described above requires the phases of the transmission waves supplied to the respective antennas to be selected with high accuracy. A phase shifter that dynamically switches the phase of a transmission wave is described in, for example, NPL 1. 
     In PTL 1, detecting a phase error amount between a transmission branch and another transmission branch is disclosed. According to PTL 1, the detected phase error amount takes a maximum value when a phase difference between the transmission branch and the another transmission branch indicates the same phase and a minimum value when the phase difference indicates reverse phases. A transmission device disclosed in PTL 1, using such a phenomenon, controls the phase difference between a transmission branch and another transmission branch to the same phase or reverse phases. 
     CITATION LIST 
     Non Patent Literature 
     NPL 1: 60 GHz Active Phase Shifter using an Optimized Quadrature All-Pass Network in 45 nm CMOS, Woorim Shin, Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International. 
     Patent Literature 
     PTL 1: JP 2014-179785 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, for example, in an in-vehicle millimeter wave radar, a high frequency signal of several tens of GHz is used as a transmission carrier. In the case of a transmission system using such a high frequency, known systems have a difficulty in controlling phases with high accuracy. It has been known that, in a conventional phase shifter, the phases of transmission waves transmitted from a plurality of antennas have an error of approximately 10 degrees there among. Although measuring such an error in advance and correcting the error are conceivable, an error between phases fluctuates depending on temperature and the like. Correcting an error between phases in consideration of temperature and the like is considered to complicate the processing of correction substantially. 
     In an in-vehicle radar, it is required to correct the emission directions of a transmission wave depending on changes in the longitudinal inclination angle of the vehicle. That is, the angle of the chassis of a vehicle changes in accordance with the weight of the rear loading space and the like. In beam forming, the need arises to correct a difference between the emission directions of transmission waves before and after change in the angle of the chassis and to keep the emission direction level. In such a case, it is required to control the emission direction of a transmission wave with an accuracy of several degrees. On this occasion, although depending on the arrangement of antennas, it also is required to adjust the phase of a transmission wave with an accuracy of several degrees. 
     Achieving phase adjustment with such a high accuracy has been difficult for a transmitter including the conventional phase shifter, in particular, in the field where a transmission wave has a high frequency. 
     The present invention is made in consideration of the above problem, and an object of the present invention is to provide a transmitter, a transmission method, a phase adjustment device, and a phase adjustment method that are capable of controlling the phase of a transmission wave to any desired value with high accuracy in a transmitter in which a high frequency signal in the order of several tens of GHz is used as a transmission wave. 
     Solution to Problem 
     In order to achieve the object mentioned above, according to an aspect of the present invention, there is provided a transmitter including: a phase shifter configured to shift a phase of an input signal and to output a shifted signal the phase of which is shifted; a first control circuit configured to change, within a predetermined range, a phase shift amount by which the phase shifter shifts the phase of the input signal; a phase difference signal output circuit configured to receive the shifted signal output by the phase shifter and a reference signal and to output a phase difference signal based on a phase difference between the shifted signal and the reference signal; an extreme value output circuit configured to, when the phase difference signal takes an extreme value while the first control circuit is changing the phase shift amount, output a value of the phase difference signal at the phase shift amount at which the phase difference signal becomes the extreme value; a target value output circuit configured to, based on an output from the extreme value output circuit, output a target value; and a second control circuit configured to control the phase shift amount of the phase shifter in such a way that a value of the phase difference signal output by the phase difference signal output circuit coincides with the target value output from the target value output circuit, wherein the phase shifter shifts the phase of the input signal in accordance with the phase shift amount controlled by the second control circuit and outputs the input signal the phase of which is shifted as a transmission wave. 
     In the above-mentioned aspect of the present invention, the second control circuit of the transmitter may receive the phase difference signal from the phase difference signal output circuit and the target value from the target value output circuit, and may control the phase shift amount of the phase shifter so that the phase difference signal coincides with the target value. 
     According to another aspect of the present invention, there is provided a transmission method including: a first phase shift step of shifting a phase of an input signal within a predetermined range of phases; a phase difference signal generation step of generating a phase difference signal based on a phase difference between the input signal the phase of which is shifted in the first phase shift step and a reference signal; an extreme value output step of, when the phase difference signal takes an extreme value while the phase of the input signal is being shifted in the first phase shift step, outputting a value of the phase difference signal at a phase shift amount at which the phase difference signal becomes the extreme value; a target value output step of outputting a target value based on the value of the phase difference signal output in the extreme value output step; a second phase shift step of shifting the phase of the input signal in such a way that a value of the phase difference signal generated in the phase difference signal generation step coincides with the target value; and outputting, as a transmission wave, the input signal the phase of which is shifted in the second phase shift step. 
     According to still another aspect of the present invention, there is provided a phase adjustment device including: a phase shifter configured to shift a phase of an input signal and to output a shifted signal the phase of which is shifted; a first control circuit configured to change, within a predetermined range, a phase shift amount by which the phase shifter shifts the phase of the input signal; a phase difference signal output circuit configured to receive the shifted signal output by the phase shifter and a reference signal and to output a phase difference signal based on a phase difference between the shifted signal and the reference signal; an extreme value output circuit configured to, when the phase difference signal takes an extreme value while the first control circuit is changing the phase shift amount, output the extreme value of the phase difference signal; a target value output circuit configured to output a target value that is set based on the extreme value output by the extreme value output circuit; and a second control circuit configured to control the phase shift amount of the phase shifter in such a way that a value of the phase difference signal output by the phase difference signal output circuit coincides with the target value output from the target value output circuit. 
     In the above-mentioned aspect of the present invention, the second control circuit of the phase adjustment device may receive the phase difference signal from the phase difference signal output circuit and the target value from the target value output circuit, and control the phase shift amount of the phase shifter in such a way that the phase difference signal coincides with the target value. 
     According to yet another aspect of the present invention, there is provided a phase adjustment method including: a first phase shift step of shifting a phase of an input signal within a predetermined range of phases; a phase difference signal generation step of generating a phase difference signal based on a phase difference between the input signal the phase of which is shifted in the first phase shift step and a reference signal; an extreme value output step of, when the phase difference signal takes an extreme value while the phase of the input signal is being shifted in the first phase shift step, outputting a value of the phase difference signal at a phase shift amount at which the phase difference signal becomes the extreme value; a target value output step of outputting a target value based on the value of the phase difference signal output in the extreme value output step; and a second phase shift step of shifting the phase of the input signal in such a way that a value of the phase difference signal generated in the phase difference signal generation step coincides with the target value. 
     Advantageous Effects of Invention 
     According to the above-mentioned aspects of the present invention, it is possible to provide a transmitter, a transmission method, a phase adjustment device, and a phase adjustment method that are capable of controlling the phase of a transmission wave to any desired value with high accuracy in a transmitter in which a high frequency signal in the order of several tens of GHz is used as a transmission wave. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram for a description of a phase adjustment device and a transmitter of a first embodiment of the present invention; 
         FIG. 2  is a diagram illustrative of a relationship between a phase shift amount changed by a first control circuit and a phase difference signal output from a phase difference signal output circuit illustrated in  FIG. 1 ; 
         FIG. 3  is a block diagram for a description of a phase adjustment device and a transmitter of a second embodiment of the present invention; 
         FIG. 4  is a flowchart for a description of processing of phase adjustment performed by a processor illustrated in  FIG. 3 ; 
         FIG. 5  is a diagram for a description of a receiver to which the phase adjustment device of the first embodiment of the present invention is applied; and 
         FIG. 6  is a functional block diagram exemplifying a known transmitter. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A first embodiment and a second embodiment of the present invention will now be described. 
     First Embodiment 
     &lt;Transmitter&gt; 
       FIG. 1  is a block diagram for a description of a transmitter including a phase adjustment device of the first embodiment. A transmitter  1  illustrated in  FIG. 1  includes a phase adjustment device  3  and an antenna  13 . 
     Although, in the first embodiment, description will be made using a transmitter including a phase adjustment device as an example, the phase adjustment device of the first embodiment is also applicable to a receiver. 
     &lt;Phase Adjustment Device&gt; 
     The phase adjustment device  3  includes a phase shifter  11  that shifts the phase of an input signal W that is input, a first control circuit  21  that successively changes the phase shift amount of the phase shifter  11 , a distributor  15  that distributes a shift input signal WS the phase of which is shifted, a phase difference signal output circuit  12  to which the shift input signal WS, which is distributed by the distributor  15 , and a reference signal R are input and that outputs a phase difference signal based on a phase difference between the shift input signal WS and the reference signal R, an extreme value output circuit  14  that acquires and outputs an extreme value of the phase difference signal, the extreme value being obtained when the first control circuit  21  successively changes the phase shift amount of the phase shifter  11 , a target value output circuit  16  that sets and outputs a target value based on the extreme value, which the extreme value output circuit  14  outputs, and a second control circuit  22  to which the phase difference signal output by the phase difference signal output circuit  12  and the target value output by the target value output circuit  6 , are input and that controls the phase shift amount of the phase shifter  11  in such a way that the extreme value coincides with the target value. 
     The shift input signal WS the phase of which is shifted is supplied to the antenna  13  via the distributor  15  and is output to the outside as a transmission wave. 
     In the first embodiment, the input signal W is generated by a not-illustrated signal source and the reference signal R is generated by a not-illustrated signal generation unit. The signal source and the signal generation unit are assumed to be disposed in an apparatus in which the transmitter  1  is disposed. Such apparatuses include, for example, a collision prevention system mounted on a vehicle and the like. 
     Next, the respective components, illustrated in  FIG. 1 , will be described. 
     (Phase Shifter) 
     The phase shifter  11  shifts the phase of the input signal W and outputs the shift input signal WS. 
     (First Control Circuit) 
     The first control circuit  21  successively changes the phase shift amount of the phase shifter  11 . As a specific processing of changing the shift amount, for example, the first control circuit  21  sweeping the phase shift amount of the phase shifter  11  in a range of 180 degrees or more is conceivable. Alternatively, the first control circuit  21  may, for example, change the phase shift amount of the phase shifter  11  repeatedly at a fixed interval in a range from 60 degrees to 240 degrees. 
     (Distributor) 
     To the distributor  15 , the shift input signal WS is input. The distributor  15  distributes the input shift input signal WS to the antenna  13  and the phase difference signal output circuit  12 . 
     (Phase Difference Signal Output Circuit) 
     To the phase difference signal output circuit  12 , the shift input signal WS and the reference signal R are input. The phase difference signal output circuit  12  outputs a phase difference signal based on a phase difference between the shift input signal WS and the reference signal R. The phase difference signal output circuit of the first embodiment includes a down conversion mixer and a low pass filter disposed at a stage succeeding the down conversion mixer, both of which will be illustrated later. The phase difference signal output circuit  12 , by performing frequency conversion using the down conversion mixer, generates and outputs the phase difference signal corresponding to the phase difference between the shift input signal WS and the reference signal R. 
     In the above, the signal, which the down conversion mixer outputs, corresponding to the phase difference between the shift input signal WS and the reference signal R is expressed by the formulae (1), (2), and (3), described below. 
     The shift input signal WS and the reference signal Rare assumed to be expressed by the formulae (1) and (2), respectively, as described below. In the formulae (1) and (2), f, t, and θ respectively denote a frequency, time, and a phase difference. The frequency of the shift input signal WS is identical to the frequency of the reference signal R. 
     [Math. 1]
 
D sin(2πft+θ) . . .   formula (1)
 
     [Math. 2]
 
E sin(2πft) . . .   formula (2)
 
     Under the above-described conditions, an output V from the down conversion mixer is expressed by the formula (3) below. The output V expressed by the formula (3) is a DC signal corresponding to the phase difference θ. In addition, in the formula (3), K is a conversion gain that the down conversion mixer has, D is the power of the input signal W, and E is the power of the reference signal R. In the formula (3), a high frequency component generated as a by-product is omitted assuming that the high frequency component is removed by the low pass filter. 
     
       
         
           
             
               
                 
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     The configuration for generating a phase difference signal in the first embodiment is not limited to the configuration in which the operation expressed by the formula (3) is performed using the above-described down conversion mixer and low pass filter. The configuration for removing a high frequency component generated as a by-product is also not limited to the low pass filter and may include, for example, an averaging processing circuit. 
     (Extreme Value Output Circuit) 
     To the extreme value output circuit  14 , outputs from the phase difference signal output circuit  12  when the first control circuit  21  successively changes the phase shift amount of the phase shifter  11  are input. That is, to the extreme value output circuit  14 , values of the phase difference signal when the phase difference θ in the formula (3) is successively changed are input. The values of the phase difference signal are stored in not-illustrated memory in the extreme value output circuit  14 . 
       FIG. 2  is a diagram illustrative of a relationship between the phase shift amount changed by the first control circuit  21  and the phase difference signal output from the phase difference signal output circuit  12 . The ordinate of a graph illustrated in  FIG. 2  indicates the phase difference signal output from the phase difference signal output circuit  12  and the abscissa indicates the phase shift amount changed by the first control circuit  21 . 
     When the first control circuit  21  sweeps the phase shift amount of the phase shifter  11  in a range from 60 degrees to 240 degrees, values of the phase difference signal corresponding to phase shift amounts in the range from 60 degrees to 240 degrees indicated by a dashed line rectangular portion S illustrated in  FIG. 2  are output from the phase difference signal output circuit  12 . 
     A curve illustrated in  FIG. 2  is expressed by the formula (3). The respective coefficients in the formula (3) are unknown. Using the curve illustrated in  FIG. 2 , a point G at which the curve takes a local maximum value or a local minimum value at a certain phase is obtained. The absolute value g of the local maximum value or the local minimum value at the point G is equivalent to −K×D×E/2 in the formula (3). In the description of the present invention, a local maximum value and a local minimum value are collectively referred to as an “extreme value”. 
     The extreme value output circuit  14  obtains and outputs the absolute value g of the local maximum value or the local minimum value from values of the phase difference signal stored in the not-illustrated memory. 
     (Target Value Output Circuit) 
     In advance of describing the target value output circuit 16, first, a method of adjusting the phase of the shift input signal WS in such a way that the phase difference thereof from the reference signal R coincides with θ will be described. The phase adjustment maybe performed by a manufacturer before shipment of the transmitter  1 . The phase adjustment may also be performed by users optionally depending on the use of and the purpose of use of the transmitter after shipment. 
     When the phase difference between the shift input signal WS and the reference signal R is θ, the phase difference signal, which the phase difference signal output circuit  12  outputs, is expressed by the formula (3). The absolute value of −K×D×E/2, which is obtained from the formula (3), coincides with the absolute value g of the local maximum value or the local minimum value at the point G. The absolute value g can be calculated by the extreme value output circuit  14  on the basis of the curve illustrated in  FIG. 2 . 
     For example, a case in which the phase difference between the shift input signal WS and the reference signal R is adjusted to θ1 is assumed. If the phase difference between the shift input signal WS and the reference signal R is θ1, the value of the phase difference signal, which is output from the phase difference signal output circuit  12 , becomes g×cosθ1. In the first embodiment, when the phase difference between the shift input signal WS and the reference signal R is desired to be adjusted to θ1, the phase shift amount of the phase shifter  11  is, using the above relation, adjusted in such a way that the value of the phase difference signal, which is output from the phase difference signal output circuit  12 , coincides with g×cosθ1. 
     The target value output circuit  16 , on the basis of the absolute value g, which the extreme value output circuit  14  outputs, and a target phase difference θ1 between the shift input signal WS and the reference signal R, generates a target value g×cosθ1 of the phase difference signal and outputs the generated target value to the second control circuit  22 . The target phase difference θ1 between the shift input signal WS and the reference signal R may be input from the outside or maybe a value that the target value output circuit  16  retains. 
     (Second Control Circuit) 
     To the second control circuit  22 , the phase difference signal, which the phase difference signal output circuit  12  outputs, and the target value, which the target value output circuit  16  has output, are input. The second control circuit  22  controls the phase shift amount of the phase shifter  11  in such a way that the phase difference signal coincides with the target value. In the embodiment, the expression “in such a way that the phase difference signal coincides with the target value” specifically means controlling a difference between the phase difference signal and the target value to a predetermined value or smaller. In the first embodiment, it is also assumed that both the phase difference signal and the target value, which are input to the second control circuit  22 , are A/D converted digital signals. 
     (Phase Shifter) 
     The phase shifter  11  shifts the phase of the input signal W in accordance with the phase shift amount, which is controlled by the second control circuit  22 . The shift of the phase causes the input signal W to become the shift input signal WS the phase of which is advanced by the target phase difference θ1 with respect to the reference signal R. The shift input signal WS is supplied to the antenna  13 . 
     (Antenna) 
     The antenna  13  outputs, as a transmission wave, the shift input signal WS the phase of which is advanced by the target phase difference θ1 with respect to the reference signal R. 
     The first embodiment described above provides an advantageous effect described below. 
     In a known transmitter, a conversion gain K of a down conversion mixer, the power D of an input signal W, and the power E of a reference signal R fluctuate in accordance with ambient temperature, and the absolute value g of an extreme value of a phase difference signal also changes in accordance with the ambient temperature. In the first embodiment, since the absolute value g corresponding to the ambient temperature can be acquired, it may be possible to control the phase of a transmission wave to any desired value with high accuracy regardless of the ambient temperature. 
     The transmitter of the first embodiment is not limited to the configuration described above. That is, in the above description, a case in which the transmitter includes one antenna and a phase difference between a transmission wave output from the one antenna and a reference signal is adjusted to a desired phase difference was described. However, the first embodiment may be applied to a case in which, in a transmitter including a plurality of antennas, a phase difference(s) between transmission waves output from the plurality of antennas is/are adjusted to a desired phase difference. 
     For example, a case is considered in which, in a transmitter including an antenna A that outputs a transmission wave w 2  and an antenna B that outputs a transmission wave W 3 , a phase difference between the transmission wave W 2 , which is output from the antenna A, and the transmission wave W 3 , which is output from the antenna B, is brought to θ2-θ3. In such a case, in the first embodiment, adjusting a phase difference between the transmission wave W 2 , which is output from the antenna A, and a reference signal R to θ2 and adjusting a phase difference between the transmission wave W 3 , which is output from the antenna B, and the reference signal R to θ3 enable the phase difference between the transmission wave from the antenna A and the transmission wave from the antenna B to be adjusted to θ2-θ3. 
     Although, in the above-described configuration, the first control circuit  21  and the second control circuit  22  were configured as separate components, the first embodiment is not limited to such a configuration. In the transmitter of the first embodiment, a portion of the circuits may be shared between the first control circuit  21  and the second control circuit  22 . 
     Second Embodiment 
       FIG. 3  is a block diagram for a description of a transmitter  7  of the second embodiment. In  FIG. 3 , the same components as the components illustrated in  FIG. 1  are illustrated with the same reference signs assigned thereto. The transmitter  7  of the second embodiment includes a phase adjustment device  33  and an antenna  13 . The phase adjustment device  33  differs from the phase adjustment device  3  in that, in place of the extreme value output circuit  14 , the target value output circuit  16 , the first control circuit  21 , and the second control circuit  22  in the phase adjustment device  3 , a processor  6  is included. While the extreme value output circuit  14 , the target value output circuit  16 , the first control circuit  21 , and the second control circuit  22  in the first embodiment are hardware configured with circuit elements, the processor  6  is a combination of computer hardware including a CPU and memory and a program running on the computer. 
       FIG. 4  is a flowchart for a description of phase adjustment processing that is performed by the processor  6 , illustrated in  FIG. 3 . Hereinafter, using  FIG. 4 , a method in which a program running on the processor  6  adjusts the phase of a transmission wave W from the transmitter  7  will be described. 
     In step S 81 , the processor  6  starts phase adjustment (calibration). At this time, to the processor  6 , a phase difference θ between a desired phase of the transmission wave W and a reference signal R is input. Next, in step S 82 , the processor  6  sets, at initial values, conditions in adjusting the phase difference. The items to be set include, for example, an initial value of a control signal that is initially input to the transmitter  7  and an initial phase and a range of phase change and the like that are set to the phase shifter  11  when the processor  6  is to change the phase of the phase shifter  11  by a fixed value. 
     Next, in step S 83 , the processor  6  saves a value of a phase difference signal that is output from the phase difference signal output circuit  12  in not-illustrated memory. Next, in step S 84 , the processor  6  determines whether or not, for all the phases within the range of phase change, which has been set in step S 82 , values of the phase difference signal have been recorded. When, in step S 84 , it is determined that values of a phase difference signal DC have not been recorded yet for all the phases within the range of phase change (No in step S 84 ), the processor  6  increments the phase control setting, that is, advances the phase one step, in step S 89 . Subsequently, in step S 83 , the processor  6  saves again, in the not-illustrated memory, a phase difference signal that is output with the phase having been changed. 
     When, in step S 84 , it is determined that recording of the phase difference signal DC has been completed over the entire range of phase change (Yes in step S 84 ), the processor  6 , on the basis of values of the phase difference signal DC saved in the not-illustrated memory, identifies the absolute value g of a local maximum value or a local minimum value (step S 85 ). 
     Next, in step S 86 , the processor  6  calculates a value V of g×cosθ based on the identified absolute value g and θ, which has been input in step S 81 . Subsequently, in step S 87 , the processor  6  reads a value of the phase difference signal DC that is output from the phase difference signal output circuit  12 , and, in step S 88 , determines whether or not the value of the phase difference signal DC coincides, within an acceptable tolerance, with V, which has been calculated in step S 86 . When the determination in step S 88  results in that the phase difference signal DC does not coincide with V (No in step S 88 ), in step S 90 , the processor  6  increments the phase control setting by one step. In step S 87 , the processor  6  reads a value of the phase difference signal DC that is output next from the phase adjustment device  33 . 
     On the other hand, when the determination in step S 88  results in that the phase difference signal DC coincides with V (Yes in step S 88 ), the processor  6  finishes phase adjustment of the transmission wave W from the transmitter  7 . 
     In the second embodiment, described above, calibration of the transmitter  7  may be performed using the processor  6 . For this reason, making the program, illustrated in  FIG. 4 , operate on a general-purpose personal computer enables the transmitter  7  to be calibrated without using a dedicated control circuit. 
     [Receiver] 
     In both the first embodiment and the second embodiment, described above, an example of application of a phase adjustment device to a transmitter was described. However, the phase adjustment devices in the first embodiment and the second embodiment are not limited to the one configured as a transmitter and may be configured as a receiver. 
       FIG. 5  is a block diagram illustrative of an example in which the communication device of the first embodiment is configured as a receiver  9 . In  FIG. 5 , the same reference signs are assigned to the same components as the components illustrated in  FIG. 1  and a description of some of the components will be omitted. 
     The receiver  9  includes a reception unit  34 , a reception unit  35 , and a control circuit  5 . Each of the reception units  34  and  35  includes a phase difference signal output circuit  29  that detects a phase difference between a reference signal and a signal to be detected and generates a phase difference signal corresponding to the detected phase difference. Each phase difference signal output circuit  29  includes a down conversion mixer  195  and a low pass filter (indicated by “LPF” in the drawing)  193 . 
     Each of the reception units  34  and  35  also includes a phase shifter  11  that shifts the phase of the signal to be detected. The control circuit  5  determines phase shift amounts of the phase shifters  11  corresponding to the phase difference signals, which are generated by the phase difference signal output circuits  29 . It is assumed that, in the receiver  9 , the control circuit  5  performs functions of the extreme value output circuit  14 , the target value output circuit  16 , the first control circuit  21 , and the second control circuit  22  that are illustrated in  FIG. 1 . 
     In the receiver  9 , the signal to be detected is an input signal W that is received by antennas  13 , and a signal that is to be input to the phase difference signal output circuits  29  is a reference signal R. 
     Each of the reception units  34  and  35  also includes a distributor  15  between the phase shifter  11  and the antenna  13 . Each of the reception units  34  and  35  includes an analog-digital converter (indicated by “ADC” in the drawing)  25  between the phase difference signal output circuit  29  and the control circuit  5 . A signal output from the phase difference signal output circuit  29  is A/D converted to a DC signal. 
     The phase shifters  11  are disposed in local transmission paths in the reception units  34  and  35 . The input signals W distributed to the respective channels are transmitted to the phase shifters  11  and the distributors  15 . The input signal W distributed by each distributor  15  is input to the down conversion mixer  195  in the corresponding phase difference signal output circuit  29  in conjunction with the reference signal R. 
     Each of the down conversion mixers  195  outputs a signal corresponding to a phase difference between the input signal W and the reference signal R to the corresponding low pass filter  193 . The low pass filter  193  outputs a phase difference signal corresponding to the phase difference between the input signal W and the reference signal R to the ADC  25  connected thereto, and the ADC  25  converts the phase difference signal into a digital signal and outputs the converted digital signal to the control circuit  5  as a phase difference signal DC. 
     The control circuit  5  processes information in accordance with a predetermined known procedure and outputs necessary control signals C to the phase shifters  11  in the reception units  34  and  35 . 
     As described above, the phase adjustment device of the first embodiment may be configured as both the transmitter  1 , illustrated in  FIG. 1 , and the receiver  9 , illustrated in  FIG. 5 . Applying the phase adjustment device of the first embodiment to the receiver  9  also enables the phases of local signals that a plurality of receivers  9  receive to coincide with one another. 
     INDUSTRIAL APPLICABILITY 
     The present invention described above is suitable for a communication field in which a high frequency signal in the order of several tens of GHz is used as a transmission wave or a reception wave and the phase thereof is required to be controlled with high accuracy. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  7  Transmitter 
           3 ,  33  Phase adjustment device 
           5  Control circuit 
           6  Processor 
           9  Receiver 
           11  Phase shifter 
           12  Phase difference signal output circuit 
           13  Antenna 
           14  Extreme value output circuit 
           15  Distributor 
           16  Target value output circuit 
           21  First control circuit 
           22  Second control circuit 
           25  ADC 
           29  Phase difference signal output circuit 
           34 ,  35  Reception unit 
           193  Low pass filter 
           195  Down conversion mixer