Abstract:
The present invention relates to a receiving/transmitting apparatus for radiating a predetermined signal and receiving a signal arriving as a response to the radiated signal, and to a radar equipment in which the receiving/transmitting apparatus is installed. In the receiving/transmitting apparatus and the radar equipment according to the present invention, high coherency is reliably achieved without any great enlargement in hardware scale. Therefore, it is possible to realize with high reliability improvement in performance and reliability as well as price reduction, downsizing, and running cost reduction in apparatuses and systems to which the present invention is applied.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a receiving/transmitting apparatus for radiating a predetermined signal and receiving a signal arriving as a response to the radiated signal and a radar equipment in which the receiving/transmitting apparatus is installed.  
           [0003]    2. Description of the Related Art  
           [0004]    In recent years, a technique for realizing sophisticated signal processing at a high speed and at a low price has been established and such signal processing has been widely applied to various electronic apparatuses and systems.  
           [0005]    This signal processing technique has been increasingly applied to, for example, radio application equipments and navigation aids such as radar equipments, among the above-mentioned electronic apparatuses, as an indispensable element technique for achieving high performance and reliability under desirable environment conditions or for heightening added values as well as for realizing adaptability to severe demands for price reduction, downsizing, lightening, energy saving, and others.  
           [0006]    [0006]FIG. 8 is a diagram showing a first structure example of a receiving/transmitting part of a radar equipment to which the signal processing technique is applied.  
           [0007]    In FIG. 8, one output of a COHO oscillator  51  is connected to an input of a mixer  52 , and to a local-frequency input of the mixer  52 , one output of an STALO oscillator  53  is connected. An output of the mixer  52  is connected to a first aperture of a circulator  56  via a pulse modulator (SW)  54  and a power amplifier  55  which are connected in cascade. To a second aperture of the circulator  56 , a feeding point of an antenna  57  is connected, and a third aperture of the circulator  56  is connected to an input of the mixer  58 . To a local-frequency input of the mixer  58 , the other output of the STALO oscillator  53  is connected. An output of the mixer  58  is connected to an input of a quadrature demodulator  59 . To a carrier input of the quadrature demodulator  59 , the other output of the COHO oscillator  51  is connected and an output of the quadrature demodulator  59  is connected to an input of a not-shown signal processing part.  
           [0008]    In the radar equipment as structured above (hereinafter referred to as a ‘first conventional example’), the COHO oscillator  51  constantly generates a reference signal with a predetermined frequency fc. The STALO oscillator  53  also generates a local-frequency signal with a predetermined frequency fs constantly.  
           [0009]    The mixer  52  generates a transmitting signal with a frequency ft (=fc+fs) equal to the sum of the frequencies of the reference signal and the local-frequency signal. The pulse modulator  54  performs on-off keying of the transmitting signal at a predetermined duty factor to generate a transmission wave and radiates the transmission wave via the power amplifier  55 , the circulator  56 , and the antenna  57 .  
           [0010]    A reflected wave reaching the antenna  57  from a target in response to the transmission wave is fed to the mixer  58  via the circulator  56 .  
           [0011]    The mixer  58  converts the reflected wave to an intermediate frequency signal with a frequency equal to a difference fr (=ft−fs=fc) between a frequency of the reflected wave and the frequency of the local-frequency signal which is generated by the STALO oscillator  53 .  
           [0012]    The quadrature demodulator  59  quadrature-demodulates the intermediate frequency signal according to the reference signal which is given by the COHO oscillator  51  to generate demodulation signals I, Q which are in quadrature. The aforesaid signal processing part performs predetermined signal processing for the demodulation signals I, Q to realize, for example, improvement in SN ratio, MTI, and others.  
           [0013]    Incidentally, in the process of the signal processing, as long as the COHO oscillator  51  and the STALO oscillator  53  constantly generate the aforesaid reference signal and the local-frequency signal respectively with desirable precision, phases of components of the reflected wave, which arrives from the target located in a fixed relative distance, relative to a phase of the reference signal do not vary (hereinafter, to satisfy this condition is simply referred to as ‘coherency’), and therefore, the improvement in the SN ratio and so on based on integrating processing and the like is achieved with high reliability.  
           [0014]    [0014]FIG. 9 is a diagram showing a second structure example of a receiving/transmitting part of a radar equipment to which the signal processing technique is applied.  
           [0015]    The radar equipment shown in FIG. 9 is characterized in that:  
           [0016]    a variable frequency oscillator  61  is provided to substitute for the COHO oscillator  51 ;  
           [0017]    a coupler  62  is provided to substitute for the mixer  52 ;  
           [0018]    neither the pulse modulator  54  nor the STALO oscillator  53  is provided; and  
           [0019]    the power amplifier  55  has a control terminal to which a later-described control signal is given together with a control input of the variable frequency oscillator  61 .  
           [0020]    Note that the same numerals and symbols are used to designate elements having the same functions as those of the elements shown in FIG. 8 and explanations thereof are omitted here.  
           [0021]    In the radar equipment as structured above (hereinafter referred to as a ‘second conventional example’), the variable frequency oscillator  61  alternately generates two signals having the same frequencies as those of the aforesaid transmitting signal and the local-frequency signal respectively (hereinafter referred to as a ‘transmission wave signal’ and a ‘receiving local-frequency signal’ respectively) according to logical values of a binary control signal which gives the aforesaid duty factor.  
           [0022]    Note that periods during which the transmission wave signal and the receiving local-frequency signal are generated by the variable frequency oscillator  61  are hereinafter referred to as ‘transmitting time’ and ‘receiving time’ respectively for simplification.  
           [0023]    The coupler  62  processes the following based on a difference between the frequency of the transmission wave signal and the frequency of the receiving local-frequency signal which are thus generated by the variable frequency oscillator  61 .  
           [0024]    to send the transmission wave signal to the power amplifier  55  but prevent its feeding to the mixer  58   
           [0025]    to send the receiving local-frequency signal to the mixer  58  but prevent its feeding to the power amplifier  55   
           [0026]    The power amplifier  55  amplifies the transmission wave signal to be fed via the coupler  62  within the transmitting time which is given as the logical value of the aforesaid control signal and radiates the transmission wave signal as a transmission wave via the circulator  56  and the antenna  57 .  
           [0027]    The mixer  58  generates an intermediate frequency signal with a frequency equal to a difference between the frequency of the reflected wave, which reaches the antenna  57  during the above receiving time and is fed thereto via the circulator  56 , and the frequency of the receiving local-frequency signal, which is fed thereto via the coupler  62  during the receiving time, and feeds the intermediate frequency signal to the quadrature demodulator  59 .  
           [0028]    In other words, the variable frequency oscillator  61  is commonly used for generating the receiving local-frequency signal during the receiving time and generating the transmission wave signal during the transmitting time while securing isolation between a transmitting part and a receiving part.  
           [0029]    Therefore, in the second conventional example, where neither the pulse modulator  54  nor the STALO oscillator  53  shown in FIG. 8 is provided, the hardware structure is simplified compared with that in the first conventional example.  
           [0030]    Incidentally, the same processing as in the first conventional example is performed by the quadrature demodulator  59  and the signal processing part which is provided on a subsequent stage of the quadrature demodulator  59  and therefore, explanations thereof are omitted here.  
           [0031]    Note that the reference signal and the local-frequency signal are constantly generated in the above-described first conventional example.  
           [0032]    Consequently, though the aforesaid coherence is secured, it is necessary to provide some hardware such as electromagnetic shielding and others for preventing cross-talk of the reference signal (given to the mixer  52  also during the period in which the reflected wave is to be received), the transmission wave signal, and the transmission wave to the mixer  58  and its subsequent stages from the mixer  52  via the pulse modulator  54  and the power amplifier  55 , in order to avoid mis-detection which may possibly be caused particularly because the transmission wave and the reflected wave have the same frequency.  
           [0033]    Therefore, the first conventional example requires an enlarged hardware scale and does not satisfy restrictions on cost, mountability, and others.  
           [0034]    Meanwhile, in the second conventional example, since the frequencies of the aforesaid receiving local-frequency signal and the transmission wave signal are set at different values from each other, no electromagnetic shielding mentioned above is required but the variable frequency oscillator  61  oscillates the receiving local-frequency signal and the transmission wave signal alternately during the transmitting time and the receiving time.  
           [0035]    Consequently, in the second conventional example, a phase difference between the transmission wave signal and the receiving local-frequency signal fluctuates in every new transmitting time and receiving time, as shown in FIG. 10( a ) so that the coherency is not secured and the components of the reflected wave are integrated by the signal processing part, for example, as shown in FIG. 10( b ).  
           [0036]    As a result, the possibility that precision in the signal processing is degraded and desirable improvement in the SN ratio and desirable performance are not achieved in the signal processing process is high compared with the first conventional example.  
         SUMMARY OF THE IN VENTION  
         [0037]    It is an object of the present invention to provide a receiving/transmitting apparatus and a radar equipment in which coherency is achieved with high reliability, without causing any great enlargement in hardware scale.  
           [0038]    It is another object of the present invention to separate the components of a reception wave at its every phase and to improve precision in signal processing which is performed for the components, without causing any great enlargement in hardware scale.  
           [0039]    It is still another object of the present invention to simplify hardware structure.  
           [0040]    It is yet another object of the present invention to stably achieve a desirable function and performance.  
           [0041]    It is yet another object of the present invention to efficiently and highly reliably measure all or a part of the characteristic, shape, size, and material of a medium through which an emission wave and a reception wave propagate, even when the reception wave is very weak.  
           [0042]    It is yet another object of the present invention to realize flexible adaptability of the structure to the frequencies of an emission wave and a reception wave.  
           [0043]    It is yet another object of the present invention to stably realize highly precise signal processing without any means for setting loose coupling or shielding coupling with means for generating a local-frequency signal which is used for receiving a reception wave.  
           [0044]    It is yet another object of the present invention to stably achieve highly precise signal processing.  
           [0045]    It is yet another object of the present invention to realize structure simplification as well as price reduction.  
           [0046]    It is yet another object of the present invention to detect a reception wave efficiently and highly reliably even when the reception wave is very weak, as long as the characteristic of a propagation path of an emission wave and a reception wave, a time required for a target to respond, and the characteristic of the target do not vary.  
           [0047]    It is yet another object of the present invention to measure all or a part of the characteristic of a medium interposed between the radar equipment and its target, a relative distance and a relative position to the target, and a relative speed and a size of the target, even when the reception wave is very weak.  
           [0048]    It is yet another object of the present invention to highly maintain reliability and precision in identifying a target.  
           [0049]    It is yet another object of the present invention to realize with high reliability improvement in performance and reliability as well as price reduction, downsizing, and running cost reduction in apparatuses and systems to which the present invention is applied.  
           [0050]    The above objects are achieved by a receiving/transmitting apparatus which alternately generates the first signal and the second signal whose frequencies are different from each other and whose phases have different fixed initial values from each other, radiates an emission wave generated based on the first signal, and heterodyne-detects, according to the second signal, a reception wave received as a response to the emission wave to separate components of the reception wave at its every phase relative to the first signal or the second signal.  
           [0051]    In the receiving/transmitting apparatus as described above, an initial value of a phase of the radiated emission wave is maintained at a fixed value every time the emission wave is transmitted, even though a signal generating section is used for both the generation of the emission wave and the heterodyne detection of the aforesaid reception wave.  
           [0052]    The above objects are also achieved by a receiving/transmitting apparatus which radiates the first signal as an emission wave.  
           [0053]    In the receiving/transmitting apparatus as described above, an initial value of a phase of the radiated emission wave is maintained at a fixed value every time the emission wave is transmitted, even though a signal generating section is used for both the generation of the emission wave and the heterodyne detection of the aforesaid reception wave.  
           [0054]    The above objects are also achieved by a receiving/transmitting apparatus which alternately performs frequency synthesis according to two different synthetic ratios, in response to a reference signal with a fixed frequency, to generate the first signal and the second signal.  
           [0055]    In the receiving/transmitting apparatus as described above, the first signal used for generating an emission wave or corresponding to the emission wave and the second signal used for receiving a reception wave are generated by performing the frequency synthesis according to the different synthetic ratios on the reference signals having a common frequency.  
           [0056]    The above objects are also achieved by a receiving/transmitting apparatus which alternately performs frequency synthesis according to a fixed synthetic ratio, in response to two reference signals with different frequencies, to generate the first signal and the second signal.  
           [0057]    In the receiving/transmitting apparatus as described above, switching frequencies of the first signal used for generating an emission wave or corresponding to the emission wave and the second signal used for receiving a reception wave is realized as updating an oscillating frequency of means for generating the reference signals.  
           [0058]    The above objects are also achieved by a receiving/transmitting apparatus which alternately performs frequency synthesis according to two different synthetic ratios, in response to two reference signals with different frequencies, to generate the first signal and the second signal.  
           [0059]    In the receiving/transmitting apparatus as described above, the frequency of the first signal used for generating an emission wave or corresponding to the emission wave and the frequency of the second signal used for receiving a reception wave are determined according to the combination of an oscillating frequency of means for generating the two reference signals, and the aforesaid synthetic ratios.  
           [0060]    The above objects are also achieved by a receiving/transmitting apparatus which generates the first signal and the second signal by reading a sequence of instantaneous values of signals individually corresponding to the first signal and the second signal, during periods in which the first signal and the second signal are to be generated respectively. The sequence of the instantaneous values is stored in the storage areas of the storage section corresponding to the respective periods.  
           [0061]    In the receiving/transmitting apparatus as described above, the first signal and the second signal are generated as the sequence of the instantaneous values which are stored in the storage section in advance and read so that the first and second signals are constantly obtainable compared with a case where the first and second signals are generated by an oscillating circuit which intermittently oscillates the first signal and/or the second signal or an oscillating circuit whose oscillating frequency is alternately switched.  
           [0062]    The above objects are also achieved by a receiving/transmitting apparatus which generates the first signal and the second signal in conformity with direct frequency synthesis which does not include a frequency-mixing process.  
           [0063]    In the receiving/transmitting apparatus as described above, the first signal and the second signal are generated alternately without any means for constantly or continuously generating a local-frequency signal being provided.  
           [0064]    The above objects are also achieved by a receiving/transmitting apparatus which generates the first signal and the second signal in conformity with direct frequency synthesis which includes a frequency-mixing process and in which a leak in a local-frequency signal used for the frequency-mixing is suppressed to such an extent that the components of a reception wave can be separated with desirable precision.  
           [0065]    In the receiving/transmitting apparatus as described above, even with means for constantly or continuously generating the local-frequency signal, the first signal and the second signal are alternately generated without any means provided for setting loose coupling or shielding coupling with the means.  
           [0066]    The above objects are also achieved by a receiving/transmitting apparatus which generates the first signal and the second signal, in conformity with indirect frequency synthesis or frequency synthesis including a process of the indirect frequency synthesis.  
           [0067]    The indirect frequency has responsiveness such that the phase of the second signal is fixed with a desirable precision at the starting point of a period during which a reception wave to be separated at its every phase relative to the first signal or the second signal, arrives.  
           [0068]    In the receiving/transmitting apparatus as described above, the first signal and the second signal are generated by a low-priced, general-purpose phase lock oscillator as long as the indirect frequency synthesis is achieved in a short lock-up time where the above-described condition can be satisfied.  
           [0069]    The above objects are also achieved by a receiving/transmitting apparatus where the components of each reception wave separated at its every phase relative to the first signal or the second signal are integrated in parallel at its every phase.  
           [0070]    In the receiving/transmitting apparatus as described above, the integrating processing is performed for each group of components of the reception waves which have the same phase and are received from a target as responses to emission waves intermittently transmitted at the same phase level every time.  
           [0071]    The above objects are also achieved by a radar equipment along with the above receiving/transmitting apparatus. The radar equipment performs signal processing associated with measurement of all or a part of the characteristic of a medium interposed between the radar equipment and its target, a relative distance and a relative position to the target, and a relative speed and a size of the target, based on the components of a reception wave which is separated at its every phase relative to an emission wave by the receiving/transmitting apparatus.  
           [0072]    In the radar equipment as described above, the above signal processing is performed for each group of components of the reception wave having the same phase, based on various digital signal processing such as integration, correlation, and others.  
           [0073]    The above objects are also achieved by a radar equipment which identifies a target based on the measurement result.  
           [0074]    In the radar equipment as described above, the measurement is performed with efficiency and high reliability even when a reception wave is very weak, as long as the characteristic of a propagation path, which is interposed between the radar equipment and a target, for an emission wave and the reception wave, a time required for the target to respond, and the characteristic of the target do not vary.  
           [0075]    The above objects are also achieved by a radar equipment along with the above receiving/transmitting apparatus. The radar equipment performs signal processing associated with measurement of all or a part of the characteristic, shape, size, and material of a medium through which an emission wave and a reception wave propagate, based on the components of the reception wave which is separated at its every phase relative to the emission wave by the receiving/transmitting apparatus.  
           [0076]    In the radar equipment as described above, its target is identified by performing processing such as integration, correlation, and others on the phase discriminated with high precision so that reliability and precision in target identification are highly maintained. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0077]    The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by identical reference numbers, in which:  
         [0078]    [0078]FIG. 1 is a block diagram showing a principle of a receiving/transmitting apparatus according to the present invention;  
         [0079]    [0079]FIG. 2 is a block diagram showing a principle of a radar equipment according to the present invention;  
         [0080]    [0080]FIG. 3 is a diagram showing a first embodiment and a second embodiment of the present invention;  
         [0081]    [0081]FIG. 4 is a chart explaining operations of the first embodiment of the present invention;  
         [0082]    [0082]FIG. 5 is a chart explaining an effect achieved by this embodiment;  
         [0083]    [0083]FIG. 6 is a diagram showing a third embodiment of the present invention;  
         [0084]    [0084]FIG. 7 is a diagram showing processes of computation to be performed in a signal processing part;  
         [0085]    [0085]FIG. 8 is a diagram showing a first structure example of a radar equipment to which a signal processing technique is applied;  
         [0086]    [0086]FIG. 9 is a diagram showing a second structure example of the radar equipment to which the signal processing technique is applied; and  
         [0087]    [0087]FIG. 10 is a chart explaining a problem of a conventional example. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0088]    The principles of a receiving/transmitting apparatus and a radar equipment according to the present invention are first explained below with reference to FIG. 1.  
         [0089]    [0089]FIG. 1 is a block diagram showing the principle of the receiving/transmitting apparatus according to the present invention.  
         [0090]    The receiving/transmitting apparatus shown in FIG. 1 is composed of a signal generating section  11  including a controlling section  11 C and a storage section  11 M, a transmitting section  12  or  12 A, a receiving section  13  or  13 A, and an integrating section  14 .  
         [0091]    The principle of a first receiving/transmitting apparatus according to the present invention is described as follows.  
         [0092]    The signal generating section  11  alternately generates the first signal and the second signal whose frequencies are different from each other and whose phases have fixed initial values. The transmitting section  12  generates an emission wave according to the first signal and radiates the emission wave. The receiving section  13  according to the second signal, heterodyne-detects a reception wave arriving as a response to the emission wave which is radiated by the transmitting section  12  to discriminate a phase of the reception wave.  
         [0093]    In other words, an initial value of a phase of the emission wave which is radiated by the transmitting section  12  is maintained at a fixed value every time the emission wave is transmitted, even though the signal generating section  11  is commonly used for the generation of the emission wave and the heterodyne detection of the aforesaid reception wave.  
         [0094]    Consequently, it is possible to obtain the phase of the reception wave with high reliability so that the relative position, the speed, and so on of a target object are precisely computed by performing predetermined processing on the phase of the reception wave without causing any substantial enlargement in hardware scale.  
         [0095]    The principle of a second receiving/transmitting apparatus according to the present invention is described as follows.  
         [0096]    The signal generating section  11  alternately generates the first signal and the second signal whose frequencies are different from each other and whose phases have different fixed initial values. The transmitting section  12 A radiates the first signal as an emission wave. The receiving section  13 A, based on the second signal, heterodyne-detects a reception wave arriving as a response to the emission wave which is radiated by the transmitting section  12 A to discriminate a phase of the reception wave.  
         [0097]    In other words, an initial value of a phase of the emission wave which is radiated by the transmitting section  12 A is maintained at a fixed value every time the emission wave is transmitted, even though the signal generating section  11  is commonly used for the generation of the emission wave and the heterodyne detection of the aforesaid reception wave.  
         [0098]    Consequently, it is possible to obtain the phase of the reception wave with high reliability so that the relative position, the speed, and so on of a target object are precisely computed by performing predetermined processing on the phase of the reception wave without causing any substantial enlargement in hardware scale.  
         [0099]    The principle of a third receiving/transmitting apparatus according to the present invention is described as follows.  
         [0100]    The signal generating section  11  alternately performs frequency synthesis according to two different synthetic ratios, in response to reference signals with a fixed frequency to generate the first signal and the second signal respectively.  
         [0101]    In other words, the frequency synthesis according to the different synthetic ratios is performed for the reference signals having a common frequency to generate the first signal which is used in generating an emission wave or corresponds to the emission wave and the second signal which is used in receiving a reception wave.  
         [0102]    Consequently, hardware structure is simplified compared with a case where the first signal and the second signal are generated by performing frequency synthesis for reference signals having different frequencies which correspond to the first signal and the second signal respectively.  
         [0103]    In a fourth receiving/transmitting apparatus according to the present invention, a sequence of instantaneous values of signals corresponding to the first signal and the second signal respectively are stored in the storage section  11 M in advance. The controlling section  11 C reads, during periods in which the first signal and the second signal are to be generated respectively, the sequence of the instantaneous values which are stored in storage areas of the storage section  11 M corresponding to the respective periods, to generate the first signal and the second signal.  
         [0104]    In other words, the first signal and the second signal are generated as the sequence of the instantaneous values which are stored in the storage section  11 M in advance and read so that the first signal and the second signal are obtainable constantly compared with a case where the first signal and the second signal are generated by an oscillating circuit for intermittently oscillating the first signal and/or the second signal or an oscillating circuit whose oscillating frequency is alternately switched.  
         [0105]    Therefore, desirable function and performance are stably and reliably obtained in the process of signal processing which is performed on the components of a reception wave.  
         [0106]    In a fifth receiving/transmitting apparatus according to the present invention, the signal generating section  11  alternately performs frequency synthesis according to fixed synthetic ratios, in response to two reference signals with different frequencies, to generate the first signal and the second signal respectively.  
         [0107]    In other words, switching of frequencies of the first signal used in generating an emission wave or corresponds to the emission wave and the second signal used in receiving a reception wave is realized as updating of an oscillating frequency of means for generating the above-mentioned reference signals.  
         [0108]    Consequently, hardware structure is simplified as long as processing to be performed for the reference signals in the process of the above frequency synthesis is consistent with frequencies of the first signal and the second signal.  
         [0109]    In a sixth receiving/transmitting apparatus according to the present invention, the signal generating section  11  alternately performs frequency synthesis according to two different synthetic ratios, in response to two reference signals with different frequencies, to generate the first signal and the second signal respectively.  
         [0110]    In other words, a frequency of the first signal which is used in generating an emission wave or corresponds to the emission wave and a frequency of the second signal which is used in receiving a reception wave are set based on the combination of an oscillating frequency of means for generating the two reference signals, and the synthetic ratios.  
         [0111]    This enables the structures of the reference signal generating sections  11 ,  11 A to flexibly adapt to frequencies of the emission wave and the reception wave to be received.  
         [0112]    In a seventh receiving/transmitting apparatus according to the present invention, the signal generating section  11  generates the first signal and the second signal in conformity with direct frequency synthesis which does not include a frequency-mixing process.  
         [0113]    In other words, the first signal and the second signal are generated alternately without any means for constantly or continuously generating a local-frequency signal being provided besides the signal generating section  11 .  
         [0114]    Consequently, highly precise signal processing is stably realized without any means provided for setting loose coupling or shielding coupling with means for generating the local-frequency signal.  
         [0115]    In an eighth receiving/transmitting apparatus according to the present invention, the signal generating section  11  generates the first signal and the second signal in conformity with direct frequency synthesis which includes a frequency-mixing process and in which leak of a local-frequency signal used in the frequency-mixing is suppressed to such an extent that components of a reception wave is separated with desirable precision by the receiving sections  13 ,  13 A.  
         [0116]    In other words, the first signal and the second signal are alternately generated without any means provided for setting loose coupling or shielding coupling with means for generating the local-frequency signal, even when means for constantly or continuously generating the local-frequency signal is provided in addition to the signal generating section  11 .  
         [0117]    Consequently, highly precise signal processing is stably achieved.  
         [0118]    In a ninth receiving/transmitting apparatus according to the present invention, the signal generating section  11  generates the first signal and the second signal, in conformity with indirect frequency synthesis or frequency synthesis including a process of the indirect frequency synthesis, the indirect frequency synthesis having responsiveness such that the phase of the second signal is fixed with desirable precision at the starting point of a period during which a reception wave whose phase is to be discriminated arrives.  
         [0119]    In other words, the first signal and the second signal are generated by a low-priced, general-purpose phase lock oscillator as long as the indirect frequency synthesis is achieved in such a short lock-up time that the above-described condition is satisfied.  
         [0120]    Consequently, structure simplification as well as price reduction is realized.  
         [0121]    In a tenth receiving/transmitting apparatus according to the present invention, the integrating section  14  integrates, in parallel, components of individual reception waves which are separated by the receiving sections  13 ,  13 A at every phase relative to the first signal or the second signal.  
         [0122]    The integrating processing described above is performed for each group of components of the reception waves having a common phase and arriving from a target as responses to emission waves which are intermittently and every time transmitted at the same phase level.  
         [0123]    Consequently, the reception wave is detected efficiently and highly reliably even when the reception wave is very weak, as long as the characteristic of a propagation path of the emission wave and the reception wave which is formed between the transmitting sections  12 ,  12 A and a target and between the receiving sections  13 ,  13 A and the target, the time required for the target to respond, and the characteristic of the target do not vary.  
         [0124]    [0124]FIG. 2 is a block diagram showing a principle of a radar equipment according to the present invention.  
         [0125]    The radar equipment shown in FIG. 2 is composed of a receiving/transmitting apparatus  21  or  21 A and a signal processing section  22  or  22 A.  
         [0126]    In a first radar equipment according to the present invention, the receiving/transmitting apparatus  21 A which corresponds to the first to tenth receiving/transmitting apparatuses described above, receives as a reception wave a reflected wave occurring in a medium through which a radiated emission wave propagates, or a signal radiated by the medium in response to the emission wave. The signal processing section  22 A performs signal processing related to measurement of all or a part of the characteristic, shape, size, and material of the above medium based on components of the reception wave which is separated by the receiving/transmitting apparatus  21 A at every phase relative to the emission wave.  
         [0127]    The signal processing described above is performed for each group of components having a common phase based on various digital signal processing such as integration, correlation, and others.  
         [0128]    Therefore, the measurement mentioned above is realized with efficiency and high reliability even when the reception wave is very weak, regardless of the medium, which corresponds to a propagation path for the emission wave and the reception wave.  
         [0129]    In a second radar equipment according to the present invention, the receiving/transmitting apparatus  21  which corresponds to the first to tenth receiving/transmitting apparatuses described above, receives as a reception wave a reflected wave occurring in a target in response to a radiated emission wave or a signal radiated by the target in response to the emission wave. The signal processing section  22  performs signal processing related to measurement of all or a part of the characteristic of a medium interposed between the receiving/transmitting apparatus  21  and the target, a relative distance and a relative position to the target, and a relative speed and a size of the target, based on a phase discriminated by the receiving/transmitting apparatus  21 .  
         [0130]    Therefore, the above measurement is achieved with efficiency and high reliability even when the reception wave is very weak, as long as the characteristic of the propagation path for the emission wave and the reception wave, which is interposed between the receiving/transmitting apparatus  21  and the target, a time required for the target to respond, and the characteristic of the target do not vary.  
         [0131]    In a third radar equipment according to the present invention, the signal processing section  22  identifies a target based on the measurement result obtained in signal processing.  
         [0132]    Since the target identification is achieved by performing processing such as integration, correlation, and others on a phase discriminated with high precision, reliability and precision in the target identification are highly maintained in any of the following cases:  
         [0133]    the target is too small for a reflector of an emission wave;  
         [0134]    a relative distance to the target is extremely long;  
         [0135]    excessive disturbance is superimposed on an emission wave and a reception wave;  
         [0136]    attenuation in a propagation path formed between the receiving/transmitting apparatus and the target is extremely large; and  
         [0137]    a characteristic (including the attenuation) of the propagation path may possibly vary to a great extent.  
         [0138]    Embodiments of the present invention are explained in detail below with reference to the drawings.  
         [0139]    [0139]FIG. 3 is a diagram showing a first embodiment and a second embodiment of the present invention.  
         [0140]    In FIG. 3, the same numerals and symbols are used to designate elements having the same structure as those shown in FIG. 9 and explanations thereof are omitted here. Note that the numeral ‘ 30 ’ denotes a reference signal generating part. The numeral ‘ 31 ’ denotes a switch which operates under the control of the reference signal generating part  30 .  
         [0141]    The reference signal generating part  30  is composed of the following elements.  
         [0142]    a clock generating part  33  having a first output connected to a carrier input of a quadrature demodulator  59   
         [0143]    a timing control part  34  having an input connected to a second output of the clock generating part  33  and an output connected to a control input of the switch  31   
         [0144]    a waveform-regenerate controlling part  35  having two inputs connected to the output of the timing control part  34  and a third output of the clock generating part  33  respectively  
         [0145]    a waveform memory  36  having a control input connected to an output of the waveform-regenerate controlling part  35  and a clock terminal connected to a fourth output of the clock generating part  33   
         [0146]    a D/A converter  37  having a clock terminal connected to a fourth output of the clock generating part  33  and an input connected to an output of the waveform memory  36   
         [0147]    a multiplier  38  having an input connected to an output of the D/A converter  37  and an output connected to an input of the switch  31   
         [0148]    [0148]FIG. 4 is a chart explaining operations of the first embodiment according to the present invention.  
         [0149]    The operations of the first embodiment according to the present invention are explained below with reference to FIG. 3 and FIG. 4.  
         [0150]    The waveform memory  36  has a first storage area and a second storage area in which data strings which are read during the aforesaid transmitting time and the receiving time respectively are stored respectively. More specifically, a sequence of instantaneous values of the following two signals are stored in advance in these storage areas respectively.  
         [0151]    a ‘quasi-transmission wave signal’ utilized as a frequency reference in generating a transmission wave to be radiated from an antenna  57  during the transmitting time  
         [0152]    a ‘quasi-local-frequency signal’ utilized as a frequency reference in generating a local-frequency signal to be fed to a mixer  58  during the receiving time Note that frequencies of the ‘quasi-transmission wave signal’ and the ‘quasi-local-frequency signal’ are hereinafter supposed to be 50 megahertz and 50.05 megahertz respectively for simplification.  
         [0153]    The clock generating part  33  constantly generates a clock signal with a predetermined frequency (supposed to be 60 megahertz here for simplification).  
         [0154]    The timing control part  34  divides the clock signal to generate a control signal signifying the aforesaid transmitting time and the receiving time by logical values at a predetermined duty factor.  
         [0155]    The waveform-regenerate controlling part  35  identifies starting points of the transmitting time and the receiving time which alternately occur according to a change in the logical values of the control signal to generate an address signal indicating the following strings of addresses which are updated at a cycle of the clock signal during the transmitting time and the receiving time respectively.  
         [0156]    a string of addresses signifying in sequence a top storage area and a series of storage areas subsequent to the top storage area in the first storage area of the waveform memory  36   
         [0157]    a string of addresses signifying in sequence a top storage area and a series of storage areas subsequent to the top storage area in the second storage area of the waveform memory  36   
         [0158]    The waveform memory  36  outputs the sequence of the instantaneous values which are stored in advance in the storage areas signified by these addresses.  
         [0159]    Therefore, signals signified by the sequence of the instantaneous values correspond to the quasi-transmission wave signal whose phase at the starting point of the transmitting time (FIG. 4( 1 )) is set at a fixed value and the quasi-local-frequency signal whose phase at the starting point of the receiving time (FIG. 4( 2 )) is set at a fixed value, as shown by the black circles and the white circles in FIG. 4.  
         [0160]    The D/A converter  37  converts the quasi-transmission wave signal and the quasi-local-frequency signal to analog signals. The multiplier  38  multiplies frequencies of the analog signals by  200  to generate a composite signal which corresponds to a transmission wave signal with a frequency of 10000 (=50×200) megahertz during the transmitting time and corresponds to a receiving local-frequency signal with a frequency of 10010 (=50.05×200) megahertz during the receiving time.  
         [0161]    The switch  31  distinguishes the transmission wave signal from the receiving local-frequency signal which are included in the composite signal according to the aforesaid logical values of the control signal and distributes the transmission wave signal and the receiving local-frequency signal to the power amplifier  55  and the mixer  58  respectively.  
         [0162]    Incidentally, processing performed by the power amplifier  55 , a circulator  56 , the antenna  57 , and the mixer  58  operating together is basically the same as that performed in the second conventional example and therefore, explanations thereof are omitted below.  
         [0163]    In other words, the transmission wave signal and the receiving local-frequency signal are generated in the transmitting time and the receiving time respectively by a single reference signal generating part  30 , but an initial value of a phase of the transmission wave signal at the starting point of the transmitting time (FIG. 5( a )( 1 )) and an initial value of a phase of the receiving local-frequency signal at the starting point of the receiving time (FIG. 5( a )( 2 )) are maintained at fixed values.  
         [0164]    Therefore, the quadrature demodulator  59  is capable of classifying components of a received reflected wave at its every phase relative to the clock signal which is generated by the clock generating part  33  and phase-locked with the transmission wave in this embodiment.  
         [0165]    Consequently, in signal processing processes, phases are discriminated and precision in the signal processing is improved so that sensitivity, resolution, and other performance are enhanced as shown by the arrow depicted by the solid line in FIG. 5( b ).  
         [0166]    The second embodiment of the present invention is explained below.  
         [0167]    This embodiment is characterized in that a multiplier  38 A having a control terminal which is connected to the output of the timing control part  34  as shown by the arrow depicted by the broken line in FIG. 3 is provided.  
         [0168]    The operations of the second embodiment according to the present invention are explained below with reference to FIG. 3.  
         [0169]    In this embodiment, the multiplier  38 A is initialized at each of a rising instant and a falling instant of the control signal, which is fed by the timing control part  34 , and sets a multiplying ratio at different values M1, M2 (for example, ‘200’ and &#39;201) during the transmitting time and the receiving time corresponding to the logical values of the control signal respectively.  
         [0170]    In other words, similarly to the first embodiment described above, the phases of the transmission wave signal and the receiving local-frequency signal at the starting points of the transmitting time and the receiving time are maintained at fixed values and both of the frequencies of the transmission wave signal and the receiving local-frequency signal are set at desirable values even when the frequencies of the quasi-transmission wave signal and the quasi-local-frequency signal which are given as the sequence of the instantaneous values by the waveform memory  36  have the same value.  
         [0171]    As a result, according to this embodiment, coherency is secured without any great enlargement in hardware scale even when word lengths of the instantaneous values to be stored in the waveform memory  36  and the number of the instantaneous values are large.  
         [0172]    [0172]FIG. 6 is a diagram showing a third embodiment of the present invention.  
         [0173]    The characteristics of this embodiment are as follows.  
         [0174]    The output of the D/A converter  37  is connected to an input of the switch  31  instead of the output of the multiplier  38 A.  
         [0175]    A multiplier  41  is provided on an interstage between the switch  31  and the power amplifier  55 .  
         [0176]    A multiplier  42  is provided on an interstage between the switch  31  and the mixer  58 .  
         [0177]    Operations of the third embodiment according to the present invention are explained below with reference to FIG. 6.  
         [0178]    The quasi-transmission wave signal and the quasi-local-frequency signal which are converted to the analog signals are obtained during the transmitting time and the receiving time respectively at the output of the D/A converter  37 , as in the second embodiment described above.  
         [0179]    The switch  31  discriminates between the transmitting time and the receiving time according to the logical values of the control signal which is given by the timing control part  34  and it gives the quasi-transmission wave signal to the multiplier  41  during the transmitting time and the quasi-local-frequency signal to the multiplier  42  during the receiving time.  
         [0180]    Meanwhile, multiplying ratios of the multipliers  41 ,  42  are set at fixed values ‘200’ and ‘201’ in advance respectively and the multipliers  41 ,  42  multiply the quasi-transmission wave signal by 200 during the transmitting time to generate the transmission wave and multiply the quasi-local-frequency signal by 201 during the receiving time to generate the receiving local-frequency signal.  
         [0181]    In other words, the transmission wave and the receiving-local-frequency signal with desirable frequencies are generated by the two multipliers  41 ,  42  which are provided to substitute for the multiplier  38 A provided in the second embodiment described above and whose multiplying ratios are set at fixed values.  
         [0182]    Therefore, according to this embodiment, similarly to the first and second embodiments described above, coherency is secured to improve precision in signal processing to be performed for the reflected wave and to enhance sensitivity, resolution, and other performance as radar under a different structure from the structures in the first and second embodiments described above.  
         [0183]    Incidentally, the frequencies of the quasi-transmission wave signal and the quasi-local-frequency signal which are given as the sequence of the instantaneous values by the waveform memory  36  during the transmitting time and the receiving time are set at the same value in the second and third embodiments described above. However, the present invention is not limited to this structure and the multiplying ratios of the multiplier  38 A or the multipliers  41 ,  42  during the transmitting time and the receiving time and the frequencies of the quasi-transmission wave signal and the quasi-local-frequency signal may be set at appropriate values which tolerate, for example, levels of distortion which may possibly be included in the quasi-transmission wave signal and the quasi-local-frequency signal or may be set at values which downsize the storage areas of the waveform memory  36  within a range of the word lengths of the storage areas.  
         [0184]    Furthermore, in each of the above described embodiments, the data in the first memory area and the second memory area of the waveform memory  36  is read with reliability from the top storage areas of these storage areas during the transmitting time and the receiving time so that the initial values of the phases of the transmission wave signal and the receiving local-frequency signal are maintained at fixed value.  
         [0185]    However, the present invention is not limited to this structure and, for example, either one of the following reference signal generating parts may be provided to substitute for the reference signal generating part  30 .  
         [0186]    a reference signal generating part composed of a single or a plurality of blocking oscillator(s) in which starting conditions are kept unchanged  
         [0187]    a reference signal generating part which does not perform a frequency-mixing and performs direct frequency synthesis  
         [0188]    a reference signal generating part which performs the direct frequency synthesis having the frequency-mixing process to maintain the phases of the transmission wave signal and the receiving local-frequency signal at the starting points of the transmitting time and the receiving time at fixed values with desirable precision and which performs  
         [0189]    a reference signal generating part which performs indirect frequency synthesis to maintain the phases of the transmission wave signal and the receiving local-frequency signal at the starting points of the transmitting time and the receiving time at fixed values with desirable precision  
         [0190]    Moreover, the frequencies of the quasi-transmission wave signal and the transmission wave signal are maintained at fixed values throughout the transmitting time in each of the above-described embodiments.  
         [0191]    However, the present invention is not limited to this structure and is applicable to radar, for example, pulse compression radar, in which desirable performance is achieved by varying the frequencies of the quasi-transmission wave signal or the transmission wave signal.  
         [0192]    In each of the above-described embodiments, integrating processing is performed for each group of components of the reflected wave having a common phase, by a signal processing part which is provided on a subsequent stage of the quadrature modulator  59 .  
         [0193]    However, processing to be performed in this signal processing part may be any of the processing listed below, for example, as shown in FIG. 7.  
         [0194]    processing for discriminating only components whose Doppler shifts exceed a predetermined minimum value, out of components of phase information I, Q obtained by the quadrature modulator  59  to realize MTI (Moving Target Indicator)  
         [0195]    processing for computing ‘a size of a target’ according to an average value (=(I 2 +Q 2 ) 1/2 ) of the phase information I, Q  
         [0196]    processing for computing ‘a relative speed of a target’ according to the aforesaid Doppler shift  
         [0197]    processing for computing ‘a relative distance of a target’ according to relative delay time at an instant when the reflected wave which is signified by the phase information I, Q is received in response to the transmission wave signal  
         [0198]    processing for computing ‘a relative position of a target’ according to a combination of a direction from which the reflected wave arrives and the above-mentioned ‘relative distance of a target’ 
         [0199]    processing for realizing all or a part of identification of ‘a specific target’, measurement of ‘a characteristic of a medium which is interposed between the receiving/transmitting apparatus and a target’, elimination of ‘a reflected wave arriving from a distributed target such as a sea clutter and so on’, and prevention or avoidance of ‘a collision with a target’ based on correlation between a predetermined reference and distribution of a frequency spectrum (the Doppler shift may be included) of the phase information I, Q and/or information which is secondarily radiated by the target in response to the aforesaid transmission wave signal and which is signified by a signal arriving as the reception wave  
         [0200]    In each of the embodiments described above, the present invention is applied to pulse radar.  
         [0201]    However, the present invention is not limited to be applied to such pulse radar and is applicable, for example, to Doppler radar and secondary radar in which emission wave and reflected wave do not always have the same frequency, and such radar may be not only utilized for navigation aids of watercrafts and aircrafts but also may be applied to any field such as weather, monitoring, controlling, and others.  
         [0202]    In each of the above-described embodiments, the transmission wave and the reflected wave are both radio waves.  
         [0203]    However, the present invention is not limited to be applied to such a radar equipment and is also applicable, for example, to a depth sounder, a fish finder, a seismic profiling device, a sonar, a flaw detector, an ultrasonic diagnostic equipment, and other various apparatuses and systems, as long as the emission wave and/or the reflected wave are/is an ultrasonic wave or a laser beam and measurement of a desirable medium and object is realized based on either of a pulse echo method, Doppler navigation, a pulse transmission method, and a resonance method.  
         [0204]    The invention is not limited to the above embodiments and various modifications may be made without departing from the spirit and the scope of the invention. Any improvement may be made in part or all of the components.