Abstract:
A synchronization equipment performs correlation processing between a first known pattern included in a received signal and a second known pattern, and detects reception timing of the received signal. A correlation value computing portion computes a correlation value between the first known pattern and the second known pattern at every reception time. A reception timing detection portion compares the computed related value with a predetermined threshold value, determines the reception time when the correlation value becomes larger than the threshold value to be the reception timing of a received signal, and, after this determination, suspends the comparison between the correlation value and the threshold value, and holds the reception time determined to be the reception timing.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a synchronization equipment used in digital communication. 
     2. Description of the Related Art 
     Conventionally, in this sort of synchronization equipment, a correlation value of a known pattern formed from a known symbol included in a received signal with a known pattern belonging to a receiver is computed, and it is decided that the known pattern has been detected when the computed correlation value becomes larger than a predetermined threshold value (disclosed in JP-A-7-250120 for instance). 
     This sort of synchronization equipment includes, as shown in FIG. 1, first and second analog-to-digital converters  101  and  102  to which in-phase components I-ch and orthogonal components Q-ch of a received signal obtained by synchronous detection of the received signal are inputted, respectively, a correlation circuit  103  to which the output signals of the first and second A/D converters  101  and  102  are inputted, and a reception timing detection circuit  108  to which the output signal of the correlation circuit  103  is inputted. Here, the correlation circuit  103  includes a first memory  104  for storing the in-phase components I-ch and the orthogonal components Q-ch of M pieces of received signals having known patterns inputted from the first and second A/D converters  101  and  102 , a correlator  105  to which two output signals of the first memory  104  are inputted, a second memory  106  where in-phase components and orthogonal components of known patterns belonging to the receiver are stored, and a power detection circuit  107  to which two output signals of the correlator  105  are inputted. Further, the reception timing detection circuit  108  includes a memory  110  where a predetermined threshold value is stored, and a comparator  109  for comparing the output signal of the correlation circuit  103  and the threshold value stored in the memory  110  with each other. 
     In this synchronization equipment, the in-phase components I-ch and the orthogonal components Q-ch of the received signal obtained by the synchronous detection of the received signal are quantized by the first and second A/D converters  101  and  102 , and stored thereafter in the first memory  104  of the correlator circuit  103 . In the first memory  104 , the in-phase components I-ch and the orthogonal components Q-ch of M pieces of received signals having the known pattern can be stored by the fact that the in-phase components I-ch and the orthogonal components Q-ch of the received signal stored most previously are superscribed by the in-phase components I-ch and the orthogonal components Q-ch of a newly inputted received signal. 
     In the correlator  105  of the correlation circuit  103 , two correlation values comb I  and comb Q  are computed with the following expressions using the in-phase components I-ch and orthogonal components Q-ch of the received signal outputted from the first memory  104  and the in-phase components and orthogonal components of the known pattern outputted from the second memory  106 .                      comb   I     =     Re        [       ∑     i   =   1     M            sw        (   i   )       ×       r        (   i   )       *         ]                   =       ∑     i   =   1     M          {           sw   I          (   i   )       ×       r   I          (   i   )         +         sw   Q          (   i   )       ×       r   I          (   i   )           }                     (   1   )                       comb   Q     =     Im        [       ∑     i   =   1     M            sw        (   i   )       ×       r        (   i   )       *         ]                   =       ∑     i   =   1     M          {         -       sw   Q          (   i   )         ×       r   Q          (   i   )         +         sw   I          (   i   )       ×       r   Q          (   i   )           }                     (   2   )                                
     Two correlation values comb I  and comb Q  computed in the correlator  105  are converted into one correlation value (power) comb by being processed in accordance with the following expression in the power, detection circuit  107 . 
     
       
         comb=comb I   2 +comb Q   2   (3)  
       
     
     Besides, in the above-described expressions (1) to (3), inferior letters I and Q show in-phase components and orthogonal components, respectively. Further, respective processings shown in the above-described expressions (1) to (3) can be realized simply by means of a software of a signal processor such as DSP. 
     The correlation value obtained in the correlation circuit  103  is compared with the threshold value which has been stored in the third memory  110  in the comparator  109  of the reception timing detection circuit  108 . When the correlation value obtained by the correlation circuit  103  is larger than this threshold value, it is decided that the known symbol has been received. 
     Besides, the correlation value is normalized with the power of the received signal sometimes in order to oppress power variation of the correlation value by fading, but a structure in the case such normalization is not made is shown here. 
     In a synchronization equipment such as described above, however, there are such problems as shown hereunder. 
     (1) Generally, when transmission is made including a known symbol train in a transmission signal, the correlation value shows the largest at the time when a transmitter transmits the known symbol train in an ideal state when the correlation between this known symbol train and the known symbol train belonging to a receiver is obtained. However, even when optimum timing is going to be detected from a fact that the correlation value simply becomes larger than a certain value or from a peak of the correlation value, the synchronization equipment does not necessarily operate smoothly when the received wave (hereinafter referred to as a “delay wave”) which is received after reflected by a building or a mountain is in existence. 
     Namely, the correlation values when such a delay wave exists are shown in FIGS. 2A to  2 D for instance. When only a desired received wave (hereinafter referred to as a “lead wave” or a “desired wave”) exists, it is possible to obtain timing which coincides with the lead wave accurately as shown in FIG.  2 A. Further, when only a delay wave exists, it is possible to obtain timing which coincides with the delay wave accurately as shown in FIG.  2 B. However, when the lead wave and the delay wave are in opposite phases and added to each other, the correlation value becomes small. Therefore, as shown in FIG. 2C, when the threshold value is made slightly larger, both the timing of the lead wave and the timing of the delay wave become no longer be detected. On the other hand, when the lead wave and the delay wave are in-phase and added to each other, the peak of the correlation value is detected at both of the reception time of the lead wave and the reception the of the delay wave. Therefore, as shown in FIG. 2D, the timing of the delay wave is detected only by the comparison with the threshold value. 
     (2) The detection accuracy of the reception timing is not so high. Namely, the detection accuracy of the reception timing depends on a sampling speed of the A/D converter, and it is when the lag between a transmitter and a receiver reaches T/2 (T: sampling time interval) that the detection accuracy is detected as a timing lag. When the sampling time interval is large, the timing lag becomes large, and the reception Performance is deteriorated. Further, when the frequency discrepancy between the transmitter and the receiver is small even in case the sampling time interval is not so large, it takes time until the timing lag is detected and a state that the reception performance has been deteriorated to some extent continues for a long time duration. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a synchronization equipment which is capable of detecting reception time of a lead wave even when the lead wave and a delay wave exist at the same time in view of the problems described in the above item (1). 
     It is another object of the present invention to provide a synchronization equipment which is capable of detecting reception timing with high accuracy in view of the problems described in the above item (2). 
     A first synchronization equipment of the present invention is a synchronization equipment for performing correlation processing between a first known pattern included in a received signal and a second known pattern to detect reception timing of the received signal, which comprises: 
     correlation value computing means for computing a correlation value between the first known pattern and the second known pattern; 
     reception timing detecting means; and 
     reception window control means for sending reception time to the correlation means and the reception timing detection means; wherein: 
     the correlation value computing means computes the correlation value at every reception time; and 
     the reception timing detection means compares the computed correlation value with a predetermined threshold value, decides the reception time when the computed correlation value becomes larger than the threshold value to be the reception timing of the received signal, suspends the comparison of the correlation value with the threshold value after the decision, and holds the reception time decided as the reception timing. 
     A second synchronization equipment is the first synchronization equipment of the present invention described above, which further comprises timing correction value detection means for drawing up a histogram of reception time held in the latch circuit, compares the frequency of the reception time in the drawn up histogram with another threshold value, and generating a timing correction value for correcting the reception time sent by the reception window control means in accordance with the reception time when the frequency exceeds another threshold value. 
     A third synchronization equipment of the resent invention is a synchronization equipment for performing correlation processing between a first known pattern included in a received signal and a second known pattern to detect reception timing of the received signal, which comprises: 
     correlation value computing means for computing a correlation value between the first known pattern and the second known pattern; 
     reception timing detection means; and 
     reception window control means for sending reception time to the correlation means and the reception timing detection means; wherein 
     the correlation value computing means computes the correlation value at every reception time; and 
     the reception timing detection means compares the computed correlation value with a predetermined threshold value, detects the reception time when the computed correlation value becomes larger than the threshold value, and obtains the reception time when the correlation value computed by the correlation value computing means becomes the largest during a certain period after the detected reception time and holds the reception time. 
     A fourth synchronization equipment of the present invention is a synchronization equipment for performing correlation processing between a first known pattern included in a received signal and a second known pattern to detect reception timing of the received signal, which comprises: 
     correlation value computing means for computing a correlation value between the first known pattern and the second known pattern; 
     reception timing detection means; and 
     reception window control means for sending reception time to the correlation means and the reception timing detection means; wherein: 
     the correlation value computing means computes the correlation value at every reception time; and 
     the reception timing detection means compares the computed correlation value with a predetermined threshold value, detects first reception time when the computed correlation value has become larger than the threshold value for the first time and second reception time when the computed correlation value has become smaller than the threshold value for the first time after the first reception time, and obtains a mean value of the first reception time and the second reception time and holds the mean value. 
     A fifth synchronization equipment of the present invention is a synchronization equipment for performing correlation processing between a first known pattern included in a received signal and a second known pattern to detect reception timing of the received signal, which comprises: 
     correlation value computing means for computing a correlation value between the first known pattern and the second known pattern; 
     reception timing detection means; and 
     reception window control means for sending reception time to the correlation means and the reception timing detection means; wherein: 
     the correlation value computing means computes the correlation value at every reception time; and 
     the reception timing detection means interpolates the computed correlation value, compares the correlation value after the interpolation with a predetermined threshold value, deciders the reception time when the correlation value after the interpolation becomes larger than the threshold value to be the reception timing of the received signal. 
     A sixth synchronization equipment of the present invention is the fifth synchronization equipment of the present invention, in which the reception timing detection means comprises means which sustains comparison of the correlation value after the interpolation with the threshold value after deciding the reception time, and holds the reception time determined to be the reception timing. 
     A seventh synchronization equipment of the present invention is the fifth or sixth synchronization equipment of the present invention, further comprises timing lag detection means provided on the output side of the reception timing detection means, wherein the timing lag detection means comprises storage means where optimum reception time is stored and adding means for obtaining the difference between the reception time held by the reception timing detecting means and the optimum reception time. 
     An eighth synchronization equipment of the present invention is the seventh synchronization equipment of the present invention, wherein the reception window control means comprises a counter for counting a clock and also being set an initial value in accordance with an output signal of the timing lag detection means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a conventional synchronization equipment; 
     FIGS. 2A to  2 D show timing charts for explaining the operation of the synchronization equipment shown in FIG. 1; 
     FIG. 3 is a block diagram of a synchronization equipment according to a first embodiment of the present invention; 
     FIGS. 4A to  4 C are timing charts for explaining the operation of the synchronization equipment shown in FIG. 3; 
     FIG. 5 is a block diagram of a synchronization equipment according to a second embodiment of the present invention; 
     FIGS. 6A and 6B are timing charts for explaining the operation of the synchronization equipment shown in FIG. 5; 
     FIG. 7 is a block diagram of a synchronization equipment according to a third embodiment of the present invention; 
     FIGS. 8A to  8 E are timing charts for explaining the operation of the synchronization equipment shown in FIG. 7; 
     FIG. 9 is a block diagram of a synchronization equipment according to a fourth embodiment of the present invention; 
     FIGS. 10A to  10 G are timing charts for explaining the operation of the synchronization equipment shown in FIG. 9; 
     FIG. 11 is a block diagram of a synchronization equipment according to a fifth embodiment of the present invention; 
     FIGS. 12A to  12 D are timing charts for explaining the operation of the synchronization equipment shown in FIG. 11; 
     FIG. 13 is a block diagram of a synchronization equipment according to a sixth embodiment of the present invention; 
     FIGS. 14A to  14 D are timing charts for explaining the operation of the synchronization equipment shown in FIG. 13; 
     FIG. 15 is a block diagram of a synchronization equipment according to a seventh embodiment of the present invention; 
     FIG. 16 is a block diagram of a synchronization equipment according to an eighth Embodiment of the present invention; and 
     FIGS. 17A to  17 C are timing charts for explaining the operation of the synchronization equipment shown in FIG.  16 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (The first embodiment) 
     A synchronization equipment according to a first embodiment of the present invention includes, as shown in FIG. 3, first and second analog-to-digital converters (A/D converters)  1  and  2 , a correlation circuit  3 , a reception timing detection circuit  8 , and a reception window control circuit  13 . The first and second A/D converters  1  and  2  quantize in-phase components I-ch and orthogonal components Q-ch of a received signal obtained by synchronous detection of the received signal, respectively. The correlation circuit  3  computes a correlation value a between a known symbol pattern included in the output signals of the first and second A/D converters  1  and  2  and a known pattern belonging to a receiver, and includes a first memory  4  in which the in-phase components I-ch and orthogonal components Q-ch of the received signal inputted from the first and second A/D converters  1  and  2 , respectively, are stored, a correlator  5  to which two output signals of the first memory  4  are inputted, a second memory  6  in which in-phase components I-ch and orthogonal components Q-ch of the known pattern of the receiver are stored, and a power detection circuit  7  to which two output signals of the correlator  5  are inputted. The reception timing detection circuit  8  decides that the known pattern in the received signal has been detected when the correlation value a computed in the correlation circuit  3  becomes larger than a predetermined threshold value, and includes a third memory  11  where the predetermined threshold value has been stored, a comparator  10  for comparing the output signal of the correlation circuit  3  with the predetermined threshold value stored in the memory  11 , a switch  9  provided between the power detection circuit  7  and the comparator  10  and opening and closing of which is controlled by a timing correction control signal b outputted from the comparator  10 , and a latch circuit  12  for latching a counter value c of a counter  14  described later of the reception window control circuit  13  by a timing correction control signal b outputted from the comparator  10 . The reception window control circuit  13  operates the correlation circuit  3  and the reception timing detection circuit  8  only for a certain period of time, and includes the counter  14  to which a clock is inputted from the outside, and a decoder  15  for generating a timing detection window signal i which operates the correlation circuit  3  and the reception timing detection circuit  8  when the counter value c of the counter  14  shows a value of the time when the known symbol is received. 
     In the synchronization equipment of the present embodiment, the number of clocks inputted from the outside is counted with the counter  14  of the reception window control circuit  13 . Here, the count period of the counter  14  is the same as the reception interval of the known symbol. In the decoder  15 , a timing detection window signal i is generated when the counter value c of the counter  14  shows a value of the time when the known symbol is received, and the correlation circuit  3  and the reception timing detection circuit  8  become operable only for the period that this timing detection window signal i is being generated. 
     The in-phase components I-ch and the orthogonal components Q-ch of the received signal obtained by the synchronous detection of the received signal are quantized by the first and second A/D converters  1  and  2 , and stored thereafter in the first memory  4  of the correlation circuit  3 . In the first memory  4 , in-phase components I-ch and orthogonal components Q-ch of M pieces of received signals having the known pattern can be stored, and the in-phase components I-ch and orthogonal components Q-ch of the received signal stored most previously are superscribed -with in-phase components I-ch and orthogonal components Q-ch of a newly inputted received signal. In the correlator  5  of the correlation circuit  3 , two correlation values are computed with the above-mentioned expressions (1) and (2) using in-phase components I-ch and orthogonal components Q-ch of the received signal outputted from the first memory  4  and in-phase components and orthogonal components of the known pattern included in the receiver that are outputted from the second memory  6 . Two correlation values computed in the correlator  5  are converted into one correlation value (power) a by being processed in the power detection circuit  7  in accordance with the above-mentioned expression (3). 
     The correlation value a obtained in the correlation circuit  3  is inputted to the comparator  10  through the switch  9  of the reception timing detection circuit  8 , and is compared with a predetermined threshold value stored in the third memory  11 . When the correlation value a obtained in the correlation circuit  3  is larger than this predetermined value, it is determined that the known symbol has been received, and the timing correction control signal b is outputted from the comparator  10 . When the timing correction control signal b is outputted from the comparator  10 , the switch  9  is brought into an open state, and the detection of the known symbol is sustained. Further, when the timing correction control signal b is inputted to the latch circuit  12 , the counter value c of the counter  14  of the reception window control circuit  13  is introduced into the latch circuit  12 . Since the switch  9  is kept in an open state hereafter, the correlation value a is never inputted to the reception timing detection circuit  8  from the correlation circuit  3 , but the counter value c of the counter  14  which has been introduced in the latch circuit  12  is outputted as reception time tmg. 
     For example, as shown in FIG. 4A, when a lead wave and a delay wave are in existence and there are peaks of the correlation value larger than the predetermined threshold value at reception time t 3  of the lead wave and reception time t 8  of the delay wave in the reception window, the performance of equalization processing becomes better when the timing is adapted to the lead wave in general in an equalizer or the like that performs equalization processing of received data utilizing the reception timing detected in the synchronization equipment. 
     In the synchronization equipment according to the present embodiment, since the correlation value a computed in the correlation circuit  3  becomes larger than the predetermined threshold value at the reception time t 3  of the lead wave, the timing correction control signal b is outputted from the comparator  10  at the reception time t 3  of the lead wave as shown in FIG.  4 B. Since the switch  9  is brought to an open state by the timing correction control signal b at this time t 3  and thereafter, the correlation value a computed in the correlation circuit  3  is never inputted to the comparator  10 . As a result, the timing correction control signal b will never be outputted from the comparator  10  at the reception time t 8  of the delay wave. Accordingly, in the synchronization equipment according to the present embodiment, it is possible to detect only the reception time of the lead wave even when there are peaks of correlation value larger than the predetermined threshold value at the reception time t 3  of the lead wave and the reception time t 8  of the delay wave in the reception window. 
     On the other hand, in the conventional synchronization equipment shown in FIG. 1, when there are peaks of correlation value larger than the predetermined threshold value at the reception time t 3  of the lead wave and the reception time t 8  of the lead wave in the reception window, the timing correction control signal b is outputted from the comparator  109  at the reception time t 3  of the lead wave and at the reception time t 8  of the delay wave as shown in FIG.  4 C. Therefore, the reception timing is locked midway between the lead wave and the delay wave, thus producing the worst timing for the equalizer. 
     Since there are provided, in the synchronization equipment according to the present embodiment, the switch  9  for suspending detection of the known symbol when the known symbol is received and thereafter, and the latch circuit  12  for holding the time when the known symbol is received in the reception timing detection circuit  8  as described above, it is possible to detect only the reception time of the lead wave surely even when the lead wave and the delay wave are in existence and there are the peaks of the correlation value larger than the predetermined threshold values in the reception window. 
     (The second embodiment) 
     A synchronization equipment according to a second embodiment of the present invention is different from the synchronization equipment according to the first embodiment shown in FIG. 3 in that a timing correction value detection circuit  16  is provided as shown in FIG.  5 . The timing correction value detection circuit  16  includes a histogram circuit  17  to which the output signal of the latch circuit  12  of the reception timing detection circuit  8  is inputted, a fourth memory  19  in which a threshold value with respect to the frequency of reception timing has been stored, a comparator  18  for comparing the output signal of the histogram circuit  17  with the threshold value stored in the fourth memory  19 , a fifth memory  21  in which the optimum reception time has been stored, and a correction value detection circuit  20  to which the output signal of the histogram circuit  17 , the output signal (timing control signal d) of the comparator  18  and the optimum reception time stored in the fifth memory  21  are inputted, and the output signal (counter correction value e) of the correction value detection circuit  20  is inputted to the counter  14  of the reception window control circuit  13 . 
     Since the operation of the first and second A/D converters  1  and  2 , the correlation circuit  3  and the reception timing detection circuit  8  in the synchronization equipment according to the present embodiment is similar to that of the synchronization equipment according to the first embodiment described above, the operation of the timing correction value detection circuit  16  and the reception window control circuit  13  related thereto will be described in detail hereinafter with reference to FIGS. 6A and 6B. 
     In the histogram circuit  17  of the timing correction value detection circuit  16 , the frequency of the reception timing is computed using the output signal of the latch circuit  12  of the reception timing detection circuit  8 . For example, it is assumed that the histogram of the reception timing before update has the maximum value at time t 3  as shown in FIG.  6 A. When the newly detected reception timing is also at the time t 3 , 1 is added to the frequency at the time t 3  until the last time in the histogram circuit  17  (see FIG.  6 B). In the comparator  18 , the frequency at each time of the histogram computed in the histogram circuit  17  is compared with the threshold value stored in the fourth memory  19 . In the comparator  18 , when a frequency larger than the threshold value is in existence, the timing control signal d is outputted. Accordingly, in an example shown in FIG. 6B, since the frequency at the time t 3  becomes larger than the threshold value, the timing control signal d is outputted from the comparator  18  at the time t 3 . In the correction value detection circuit  20 , the time when the frequency becomes larger than the threshold value (the time t 3  in the example shown in FIG. 6B) and the optimum reception time stored in the fifth memory  21  are compared with each other only when the timing control signal d is inputted from the comparator  18 . A timing correction value e which sets the initial value of the counter  14  of the reception window control circuit  13  at 0 in case the time when the frequency becomes larger than the threshold value is the same as the optimum reception time, sets the initial value of the counter  14  at −1 in case the time when the frequency becomes larger than the threshold value is earlier than the optimum reception time, and sets the initial value of the counter  14  at +1 in case the time when the frequency becomes larger than the threshold value is later than the optimum reception time is outputted from the correction value detection circuit  20  to the counter  14 . 
     As a result, for example, in case the time when the frequency becomes larger than the threshold value is time t 4  when the optimum reception time stored in the fifth memory  21  is time t 3 , the timing correction value e which sets the initial value of the counter  14  at −1 is outputted from the correction value detection circuit  20 . Therefore, the reception time detected by the reception timing detection circuit  8  the next time becomes earlier than the actual reception time by one sample time interval and shows time t 3  which is the optimum reception time. On the other hand, in case the time when the frequency becomes larger than the threshold value is time t 2  when the optimum reception time stored in the fifth memory  21  is time t 3 , the timing correction value e which sets the initial value of the counter  14  at +1 is outputted from the correction value detection circuit  20 . Therefore, the reception time detected by the reception timing detection circuit  8  next time gets later than the actual reception time by one sample time interval and shows time t 3  which is the optimum reception time. 
     Since there is provided, in the synchronization equipment of the present embodiment, the timing correction value detection circuit  16  which detects the histogram of the reception time and corrects the lag of the reception time when a frequency larger than the threshold value is included, it is possible to detect the reception time of the lead wave accurately even when both the lead wave and the delay wave are in existence. 
     (The third embodiment) 
     A synchronization equipment according to a third embodiment of the present invention is different from the synchronization equipment according to the first embodiment shown in FIG. 3 in that a reception timing detection circuit is structured as described hereunder. 
     In the synchronization equipment according to the present embodiment, a reception timing detection circuit  31  includes a memory  32 , a comparator  33 , a timer  34 , a maximum value detection circuit  35  and a latch circuit  36  as shown in FIG.  7 . In the memory  32 , a predetermined threshold value is stored. In the comparator  33 , a correlation value a sent from the correlation circuit  3  and the predetermined threshold value stored in the memory  32  are compared with each other, and 1 is outputted as a control signal f when the correlation value a is larger than the predetermined threshold value, and 0 is outputted as the control signal f when the correlation value a is smaller than the predetermined threshold value. In the timer  34 , when 1 is inputted as the control signal f from the comparator  33 , a control signal q which operates the maximum value detection circuit  35  only for a certain period (timer value) is outputted. In the maximum value detection circuit  35 , when the newly inputted correlation value a is larger than the maximum value of the correlation values in the past, 1 is outputted as a control signal h only for a period shorter than one sample time interval, and the newly inputted correlation value a is also replaced with the maximum value of the correlation values in the past. In the latch circuit  36 , a count value c of the counter  14  of the reception window control circuit  13  is taken in and held at the rise edge of the control signal h from the maximum value detection circuit  35 . Besides, the maximum value of the correlation values in the past stored in the maximum value detection circuit  35  is reset to 0 at a fall edge of an output signal (a timing detection window signal i) of the decoder  15 . 
     The operation of the synchronization equipment according to the present embodiment will be described taking a case that the correlation value a and the predetermined threshold value stored in the memory  32  have a mutual relationship shown in FIG.  8 A and the width of a timing detection window signal i is 4 as an example. 
     Since the correlation value a is smaller than the predetermined threshold value at time t 0 , 0 is outputted from the comparator  33  as the control signal f (see FIG.  8 B). Further, since the timer value of the timer  34  is 0 (see FIG.  8 C), 0 is outputted from the timer  34  as the control signal q (see FIG.  8 D). As a result, the maximum value detection circuit  35  is not operated. 
     Since the correlation value a becomes larger than the predetermined threshold value at time t 1 , 1 is outputted from the comparator  33  as the control signal f (see FIG.  8 B). In the timer  34 , since the timer value is set to 4 which is the width of the timing detection window signal i at the rise edge of the control signal f from the comparator  33  (see FIG.  8 C), 1 is outputted from the timer  34  as the control signal q (see FIG.  8 D). As a result, the maximum value detection circuit  35  starts the operation, and the maximum value of the correlation values in the past (0 in this case since it has been reset at the fall edge of the timing detection window signal i) and the correlation value a computed at the time t 1  are compared with each other. Since the correlation value a computed at the time t 1  is larger than 0, the control signal h having a pulse width shorter than one sample time interval is outputted from the maximum value detection circuit  35  (see FIG.  8 E), and, in the maximum value detection circuit  35 , the correlation value a computed at the time t 1  is replaced with 0 which is the maximum value of the correlated values in the past. In the latch circuit  36 , the counter value c is taken in and held at the rise edge of the control signal h. 
     Since the correlation value a is larger than the predetermined threshold value at time t 2 , 1 is continued to be outputted from the comparator  33  as the control signal f (see FIG.  8 B). In the timer  34 , the timer value is decremented and set to 3 (see FIG.  8 C). Since the timer value is not 0 as before, however, 1 is continued to be outputted from the timer  34  as the control signal q (see FIG.  8 D). As a result, the maximum value detection circuit  35  continues the operation, and the maximum value of the correlation values in the past (in this case, the correlation value a computed at the time t 1 ) and the correlation value a computed at the time t 2  are compared with each other. Since the correlation value a computed at the time t 2  is larger than the correlation value a computed at the time t 1 , the control signal h having a pulse width shorter than one sample time interval is outputted from the maximum value detection circuit  35  (see FIG.  8 E), and the correlation value a computed at the time t 2  is replaced with the correlation value a computed at the time t 1  in the maximum value detection circuit  35  at the same time. In the latch circuit  36 , the counter value c is taken in and held at the rise edge of the control signal h. 
     At time t 3 , 1 is continued to be outputted from the comparator  33  as the control signal f (see FIG. 8B) because the correlation value a is larger than the predetermined threshold value. In the timer  34 , the timer value is decremented and set to 2 (see FIG.  8 C). Since the timer value is not 0 as before, however, 1 is continued to be outputted from the timer  34  as the control signal q (see FIG.  8 D). As a result, the maximum value detection circuit  35  continues the operation, and the maximum value of the correlation values in the past (in this case, the correlation value a computed at the time t 2 ) and the correlation value a computed at the time t 3  are compared with each other. Since the correlation value a computed at the time t 3  is larger than the correlation value a computed at the time t 2 , the control signal h having a pulse width shorter than one sample time interval is outputted from the maximum value detection circuit  35  (see FIG.  8 E), and the correlation value a computed at the time t 3  is replaced with the correlation value a computed at the time t 2  in the maximum value detection circuit  35 . In the latch circuit  36 , the counter value c is taken in and held at the rise edge of the control signal h. 
     At time t 4 , since the correlation value a is larger than the predetermined threshold value, 1 is continued to be outputted from the comparator  33  as the control signal f (see FIG.  8 B). In the timer  34 , the timer value i decremented and set to 1 (see FIG.  8 C). Since the timer value is not 0 as before, however, 1 is continued to be outputted from the timer  34  as the control signal q (see FIG.  8 D). As a result, the maximum value detection circuit  35  continues the operation, and the maximum value among the correlation values in the past (in this case, the correlation value a computed at the time t 3 ) and the correlation value a computed at the time t 4  are compared with each other. Since the correlation value a computed at the time t 4  is smaller than the correlation value a computed at the time t 3 , 0 is outputted from the maximum value detection circuit  35  as the control signal h (see FIG.  8 E). At this time, the correlation value a computed at the time t 4  is not replaced with the correlation value a computed at the time t 3  in the maximum value detection circuit  35 . Further, the latch circuit  36  continues to hold the counter value c taken in at the time t 3 . 
     Since the correlation value a is smaller than the predetermined threshold value at time t 5 , 0 is outputted from the comparator  33  as the control signal f (see FIG.  8 B). In the timer  34 , the timer value is decremented and set to 0 (see FIG.  8 C). As a result, 0 is outputted from the timer  34  as the control signal q (see FIG.  8 D), and the operation of the maximum value detection circuit  35  is sustained. Further, the latch circuit  36  continues to hold the count value c taken in at the time t 3 . 
     Since 0 is continued to be outputted from the timer  34  as the control signal q from time t 6  to time t 10  (see FIG.  8 D), the maximum value detection circuit  35  will never restart the operation. Further, the latch circuit  36  continues to hold the count value c taken in at the time t 3 . As a result, it is possible to detect the reception time of the lead wave accurately. 
     As described above, in the synchronization equipment according to the present embodiment, the maximum value detection circuit  35  of the reception timing detection circuit  31  detects the reception time when the correlation value is at the maximum only during a certain period of time specified by the timer  34  from the time when the known symbol has been received and the latch circuit  36  holds the reception time after the lapse of the pointed time. Thus, it is possible to detect the reception time of the lead wave accurately even when the lead wave and the delay wave are in existence. 
     (The fourth embodiment) 
     A synchronization equipment according to a fourth embodiment of the present invention is different from the synchronization equipment according to the first embodiment shown in FIG. 3 in that a reception timing detection circuit is structured as described hereunder. 
     In the synchronization equipment according to the present embodiment, a reception timing detection circuit  41  includes a switch  42 , a memory  43 , a comparator  44 , first and second latch circuits  45  and  46 , a mean circuit  47  and a window control circuit  48  as shown in FIG. 9. A predetermined threshold value is stored in the memory  43 . In the comparator  44 , a correlation value a sent from the correlation circuit  3  through the switch  42  and the predetermined threshold value stored in the memory  43  are compared with each other, and 1 is outputted as a control signal i when the correlation value a is larger than the predetermined threshold value and 0 is outputted as the control signal j when the correlation value a is smaller than the predetermined threshold value. In the first latch circuit  45 , the counter value c of the counter  14  of the reception window control circuit  13  is taken in and held at the rise edge of the control signal i from the comparator  44 . In the second latch circuit  46 , the counter value c is taken in and held at the fall edge of the control signal i from the comparator  44 . In the mean circuit  47 , a mean value of the counter value c held in the first latch circuit  45  and the counter value c held in the second latch circuit  46  is obtained, and the obtained means value is used as the detection time of the known symbol. A switch control signal k which controls ON/OFF of the switch  42  is formed in the window control circuit  48 . Here, the switch control signal k is made 0 at the fall edge of the control signal j from the comparator  44  and is made 1 by the output signal (timing detection window signal i) of the decoder  15 . The switch  42  is turned OFF when the switch control signal k at 0 is inputted from the window control circuit  48  and is turned ON when the control signal k at 1 is inputted. 
     The operation of the synchronization equipment according to the present embodiment will be described taking a case that the correlation value a and the predetermined threshold value stored in the memory  43  have a mutual relationship shown in FIG.  10 A and the width of the timing detection window signal i is 4 as an example. 
     In the window control circuit  48 , the switch control signal k is set to 1 at time t 0  by the timing detection window signal i (see FIG.  10 C). As a result, the switch  42  is brought to an on-state (closed state). 
     In the comparator  44 , the correlation value a which is sent from the correlation circuit  3  to the reception timing detection circuit  41  and the predetermined threshold value stored in the memory  43  are compared with each other. In this case, since the correlation value a is smaller than the predetermined threshold value (see FIG.  10 A), 0 is outputted from the comparator  44  as the control signal j (see FIG.  10 B). As a result, the counter value c is never taken ir the first latch circuit  45  and the second latch circuit  46 , and the outputs thereof become unstable (see FIGS. 10D to  10 G). With this, the output of the mean circuit  47  also becomes unstable. 
     Since the control signal d from the comparator  44  has no fall edge at time t 1 , the switch control signal k is remained as it is 1 (see FIG.  10 C). As a result, the switch  42  remains ON (closed state). In the comparator  44 , the correlation value a which is sent from the correlation circuit  3  to the reception timing detection circuit  41  and the predetermined threshold value stored in the memory  43  are compared with each other. In this case, since the correlation value a is larger than the predetermined threshold value (see FIG.  10 A), 1 is outputted from the comparator  44  as the control signal j (see FIG.  10 B). As a result, in the first latch circuit  45 , the counter value c (=1) is taken in at the rise edge of the control signal i (see FIGS.  10 D and  10 E). On the other hand, in the second latch circuit  46 , the counter value c is never taken in, but the output thereof remains as it is unsettled (see FIGS.  10 F and  10 G). Although the counter value c (=1) is held in the first latch circuit  45 , the output signal of the second latch circuit is unsettled. Therefore, the output of the mean circuit  47  remains as it is unsettled. 
     Since the control signal d from the comparator  44  has no fall edge from time t 2  to time t 4 , the switch control signal k is left as it is 1 (see FIG.  10 C). As a result, the switch  42  remains in an ON-state (closed state). In the comparator  44 , the correlation value a which is sent from the correlation circuit  3  to the reception timing detection circuit  41  and the predetermined threshold value stored in the memory  43  are compared with each other. In this case, since the correlation value a is larger than the predetermined threshold value (see FIG.  10 A), 1 is continued to be outputted from the comparator  44  as the control signal j (see FIG.  10 B). As a result, in the first latch circuit  45 , the counter value c (=1) which was taken in at the time t 1  is continued to be held (see FIGS.  10 D and  10 E). On the other hand, in the second latch circuit  46 , the counter value c is never taken in, but the output thereof remains as it is unsettled (see FIGS.  10 F and  10 G). Although the counter value c (=1) which was taken in at the time t 1  is continued to be held in the first latch circuit  45 , the output signal of the second latch circuit remains as it is unsettled. 
     Since the switch  42  remains as it is ON at the time t 5 , the correlation value a sent from the correlation circuit  3  to the reception timing detection circuit  41  and the predetermined threshold value stored in the memory  43  are compared with each other. In this case, since the correlation value a is smaller than the predetermined threshold value (see FIG.  10 A), the control signal j outputted from the comparator  44  is changed from 1 to 0 (see FIG.  10 B). As a result, since a fall edge is produced in the control signal j from the comparator  44  and the switch control signal k is changed from 1 to 0 in the window control circuit  48  (see FIG.  10 C), the switch  42  is brought to an OFF state (open state). Further, in the first latch circuit  45 , the counter value c (=1) which was taken in at the time t 1  continues to be held (see FIGS.  10 D and  10 E), but the counter value c (=5) is taken in at the fall edge of the control signal j from the comparator  44  in the second latch circuit  46  (see FIGS.  10 F and  10 G). With this, a mean value (=3) of the counter value c (=1) taken into the first latch circuit  45  at the time t 1  and the counter value c (=5) taken into the second latch circuit  46  is obtained for the output of the mean circuit  47 . 
     The switch control signal k remains as it is at 0 from time t 6  to time t 10  (see FIG.  10 C). Accordingly, the correlation value a is never inputted to the comparator  44 , but 0 is inputted to the comparator  44  in place of the correlation value a. Therefore, the control signal d outputted from the comparator  44  remains as it is 0 (see FIG.  10 B). As a result, the counter value c (=1) which was taken in at the time t 1  continues to be held in the first latch circuit  45 , and the counter value c (=5) which was taken in at the time t 5  continues to be held in the second latch circuit  46 . With this, the mean value (=3) obtained at the time t 5  continues to be outputted from the mean circuit  47 . 
     As described above, in the synchronization equipment according to the present embodiment, the mean value of the first time when the correlation value a has become larger than the predetermined threshold value stored in the memory  43  for the first time, detected in the first latch circuit  45  of the reception timing detection circuit  41 , and the second time when the correlation value a becomes smaller than the predetermined threshold value for the first time after the first time, detected in the second latch circuit  46 , is obtained in the mean circuit  47 , and this mean value is adopted as the reception time of the known symbol. Therefore, even when both the lead wave and the delay wave are in existence, it is possible to detect the reception time of the lead wave accurately. 
     Besides, in the synchronization equipment according to the present embodiment, since detection of the maximum value such as the synchronization equipment according to the third embodiment described above is not performed, it is possible to reduce the circuit scale when it is realized with a hardware or the number of operation steps when it is realized with a software. Further, since the same results are obtainable with a synchronization equipment according to the present embodiment and the synchronization equipment according to the above-mentioned third embodiment when the correlation value is symmetrical with respect to the reception time of the maximum value, it may safely be said that the synchronization equipment according to the present embodiment which is simple to be realized is preferable. When the correlation value is not symmetrical with respect to the reception time of the maximum value, however, the synchronization equipment according to the above-mentioned third embodiment can detect the reception time of the known reception symbol (the time when the correlation value reaches the maximum) more accurately. 
     In the first to fourth embodiments of the present invention described above, since the detection timing is adapted to the lead wave when both the lead wave and the delay wave are received, it is possible to remove the effect by the delay wave thereby to detect the reception time of the lead wave accurately. 
     (The fifth embodiment) 
     A synchronization equipment according to a fifth embodiment of the present invention is different from the synchronization equipment according to the first embodiment shown in FIG. 3 in that a reception timing detection circuit is structured as described hereunder. 
     In the synchronization equipment according to the present embodiment, a reception timing detection circuit  208  includes, as shown in FIG. 11, an interpolator  209  for interpolating the correlation value a which is sent from the correlation circuit  3 , a first memory  210  in which a correlation value A after interpolation is stored, an address control circuit  211  for controlling the time and order for reading out the correlation value A after interpolation of the first memory  210 , a second memory  213  in which a predetermined threshold value is stored, a comparator  212  for comparing the correlation value A after interpolation read out of the first memory  210  with the predetermined threshold value stored in the second memory  213 , and outputting a control signal B when the correlation value A after interpolation is larger than the predetermined threshold value, and a latch circuit  214  for taking in and holding a counter value c which is sent from a reception window control circuit  13  and an interpolation number D which is sent from the address control circuit  211  when the control signal B is sent from the comparator  212 . 
     The operation of the synchronization equipment according to the present embodiment will be described taking a case that it is assumed that interpolation in the interpolator  209  is a three-times primary candidate, and the reception time of a known symbol is detected between the time t 0  to the time t 6  as an example. 
     In the conventional synchronization equipment shown in FIG. 1, when it is assumed that the correlation value outputted from the correlation circuit  103  and the predetermined threshold value stored in the memory  110  have a relationship shown in FIG. 12A, the output signal of the comparator  109  shows a high level during a period when the correlation value is larger than the threshold value (viz. from the time t 3  to the time t 4 ) as shown in FIG.  12 B. Thus, in this synchronization equipment, the detection accuracy of the reception timing is determined univocally by a sampling time interval T in the first and second A/D converters  101  and  102 . 
     As against the above, in the synchronization equipment according to the present embodiment, the correlation value a (see a broken line shown in FIG. 12C) outputted from the correlation circuit  3  is interpolated to three times in the interpolator  209 , and the correlation value A after interpolation is stored in the first memory  210 . When the address control circuit  211  controls so as to read out the correlation value A after interpolation from the first memory  210  at the 0th, the first and the second of respective times (see a solid line shown in FIG.  12 C), 0.1 and 2 are outputted from the address control circuit  211  to the latch circuit  214 . 
     Now, when it is assumed that the correlation value A after interpolation and the predetermined threshold value stored in the second memory  213  have mutual relationship shown in FIG. 12C, the control signal B outputted from the comparator  212  shows a high level during the period from an interpolation number D=2 at the time t 3  when the correlation value A after interpolation becomes larger than the predetermined threshold value to an interpolation number D=0 at time t 4  (see FIG.  12 D). In the latch circuit  214 , the counter value c and the interpolation number D are taken in and held at the rise edge of the control signal B. With this, the detection time of the known symbol detected in the synchronization equipment according to the present embodiment is expressed by (3+2/3)T=11T/3. Besides, the detection time tmg of the known symbol detected in the synchronization equipment according to the present embodiment is generally expressed by the following expression. 
     
       
         tmg=(n+m/N)·T  (4)  
       
     
     Here, n is a counter number, 
     N is a rate of interpolation, 
     m is an interpolation number, and 
     T is a sampling the interval between the 
     A/D converters  1  and  2 . 
     Accordingly, in the synchronization equipment according to the present embodiment, it is possible to detect the reception timing with higher accuracy as compared with the conventional synchronization equipment. Further, the timing lag in the synchronization equipment according to the present embodiment becomes ±T/(2N) as against that the timing lag in the conventional synchronization equipment becomes ±T/2. 
     (The sixth embodiment) 
     A synchronization equipment according to a sixth embodiment of the present invention is different from the synchronization equipment according to the fifth embodiment shown in FIG. 11 in that a reception timing detection circuit  208 A includes a switch  218  opening and closing of which is controlled by a control signal B outputted from the comparator  212  provided before the interpolator  209  as shown in FIG.  13 . 
     When the lead wave (a desired wave) and the delay wave are included in the received wave, a correlation value a computed in the correlation circuit  3  changes with the passage of time as shown in FIG. 14A for instance. Here, the lead wave is a received signal which reaches most immediately directly from a transmitting station, and the delay wave is a received signal which reaches late after reflected by a building, a mountain and so on. In an electric wave environment where such a delay wave exists, there are a cases when the lead wave is received principally, a case when the delay wave is received principally, and a case when both the lead wave and the delay wave are received. 
     Since only the lead wave is received when there is no delay wave, it is possible to cope with the circumstances sufficiently with the synchronization equipment according to the above-mentioned fifth embodiment. When the delay wave is in existence, however, since the time when the correlation value a becomes larger than the predetermined threshold value is adopted as the reception timing in the synchronization equipment according to the above-mentioned fifth embodiment, the reception time of the lead wave is detected when the lead wave is received principally, the reception time of the delay wave is detected when the delay wave is received principally, and both the reception time of the lead wave and the reception time of the delay wave are detected when both the lead wave and the delay wave are received. In such a case, when the reception timing is corrected based on the detected reception time, the reception timing is controlled a little to the delay wave between the lead wave and the delay wave. Therefore, the reception timing after control becomes a reception timing when the performance can be least demonstrated when the delay wave is going to be removed with an equalizer or the like. The synchronization equipment according to the present embodiment is capable of adapting the reception timing to the lead wave surely in order to give full display to the performance of an equalizer or the like. 
     The operation of the reception timing detection circuit  208 A when the reception time of the known symbol is detected during time t 0  to time t 6  will be described hereinafter assuming that the interpolator  209  performs three times primary interpolation similarly to the case of the synchronization equipment according to the above-mentioned fifth embodiment. 
     When the time showing that the sampling time is n and the interpolation number D is m in the first and second A/D converters  1  and  2  is expressed by t(n−m), the switch  218  is closed on the rise edge of the output signal (a timing detection window signal i) of the decoder  15  of the receiving window control circuit  13  at time t( 0 - 0 ). As a result, the correlation value a computed in the correlation circuit  3  is inputted to the interpolator  209  and interpolation processing is performed, and stored thereafter in the first memory  210 . That which has the interpolation number D of zero among the correlation values A after interpolation stored in the first memory  210  is selected in the address control circuit  211  and inputted to the comparator  212 . Since the selected correlation value A after interpolation is smaller than the predetermined threshold value stored in the second memory  213  as shown in FIG. 14B, the control signal B outputted from the comparator  212  remains as it is at a low level. Accordingly, in the latch circuit  214 , the counter value c and the interpolation number D are never taken in. 
     At time t( 0 - 1 ), that which has the interpolation number D of 1 among the correlation values A after interpolation stored in the first memory  210  is selected by the address control circuit  211  and inputted into the comparator  212 . Since this selected correlation value A after interpolation is smaller than the predetermined threshold value stored in the second memory  213  as shown in FIG. 14B, the control signal B outputted from the comparator  212  remains as it is at a low level. Thus, in the latch circuit  214 , the counter value c and the interpolation number D are never taken in. 
     At time t( 0 - 2 ), that which has the interpolation number D of 2 among the correlation values A after interpolation stored in the first memory  210  is selected by the address control circuit  211  and inputted into the comparator  212 . Since this selected correlation value A after interpolation is smaller than the predetermined threshold value stored in the second memory  213  as shown in FIG. 14B, the control signal E outputted from the comparator  212  remains as it is at a low level. Thus, in the latch circuit  214 , the counter value c and the interpolation number D are never taken in. 
     At time from time t( 1 - 0 ) to time t( 1 - 2 ), since the correlation value A after interpolation is smaller than the predetermined threshold value stored in the second memory  213  as shown in FIG. 14B, the operation similar to that from the time t( 0 - 0 ) to the time t( 0 - 2 ) is performed. 
     At time from t( 2 - 0 ) to t( 2 - 1 ), since the correlation value A after interpolation is smaller than the predetermined threshold value stored in the second memory  213  as shown in FIG. 14B, the operation similar to that at the above-mentioned time from time t( 0 - 0 ) to time t( 0 - 1 ) is performed. At time t( 2 - 2 ), however, since the correlation value A after interpolation becomes larger than the predetermined value stored in the second memory  213  as shown in FIG. 14B, the control signal B outputted from the comparator  212  shows a high level. Accordingly, in the latch circuit  214 , the counter value c (which indicates the time t 2  in this cases) and the interpolation number D (which indicates 2 in this case) are taken in and held at the rise edge of the control signal B. Further, the switch  218  is opened at the rise edge of the control signal B, and the switch  218  remains as it is opened thereafter. As a result, from time t( 3 - 0 ) to time t( 6 - 2 ), the correlation value a computed in the correlation circuit  3  is not inputted into an interpolator  209 , but the control signal B outputted from the comparator  212  shows a low level (see FIG.  14 C). As a result, time t( 2 - 2 ) is outputted from the latch circuit  214  as the receiving time of the known symbol after completion of timing detection window. With this, it is possible to detect the reception timing from the above-mentioned expression (4) with the accuracy of (2+2/3)T=8T/3. 
     As described above, in the synchronization equipment according to the present embodiment, it is possible to detect the reception timing of the lead wave surely even when both the lead wave and the delay wave are in existence in addition to the effect of synchronization equipment according to the above-mentioned fifth embodiment. Incidentally, since the correlation value A after interpolation also exceeds the predetermined threshold value at the time t( 4 - 2 ) as shown in FIG. 14B in the synchronization equipment according to the above-mentioned fifth embodiment, the latch circuit  214  is operated at the time t( 4 - 2 ). As a result, since reception timings of both the lead wave and the delay wave are detected as shown in FIG. 14D, the reception timing is locked midway between the lead wave and the delay wave. 
     (The seventh embodiment) 
     A synchronization equipment according to a seventh embodiment of the present invention is different from the synchronization equipment according to the sixth embodiment shown in FIG. 11 in that a timing lag detection circuit  219  is provided on the output side of the reception timing detection circuit  208  as shown in FIG.  15 . Here, the timing lag detection circuit  219  includes a memory  220  in which the optimum reception time is stored, and an adder  221  for obtaining the difference between the optimum reception time stored in the memory  220  and the reception time tmg detected in the reception timing detection circuit  208 . 
     As described previously, the reception time tmg of the known symbol detected in the reception timing detection circuit  208  is expressed with the counter value c and the interpolation number D. Namely, when it is assumed that the counter value c of the counter  14  is n, the interpolation number D is m, the rate of interpolation is N, and the sampling time interval between the first and second A/D converters  1  and  2  is T, it is possible to obtain the reception time tmg with the above-mentioned expression (4). When it is assumed that the optimum reception time stored in the memory  220  is xT, the timing correction value A can be obtained from the following expression. 
     
       
         Δ=tmg−xT =(n+m/N−x)T  (4)  
       
     
     The operation of the expression (4) is performed in the adder  221 . Namely, a negative timing correction value A is obtained when the reception time tmg of the known symbol is earlier than the optimum reception time xT, and a positive timing correction value A is obtained when the reception time tmg of the known symbol is later than the optimum reception time xT. Accordingly, in the synchronization equipment according to the present embodiment, it is possible to detect the reception timing lag from the output of the synchronization equipment with a simple structure. 
     Besides, when the timing lag detection circuit  219  is provided on the output side of the reception timing detection circuit  208 A of the synchronization equipment according to the sixth embodiment shown in FIG. 13, similar effects are also obtainable. 
     (The eighth embodiment) 
     A synchronization equipment according to an eighth embodiment of the present invention is different from the synchronization equipment according to the seventh embodiment shown in FIG. 15 in that an output signal H of the timing lag detection circuit  219  is inputted to a counter  14 A of a receiving window control circuit  13 A so as to correct timing automatically. In timing correction in the present embodiment, the timing lag by the correlation value B after interpolation is corrected. Therefore, the timings of the first and second A/D converters  1  and  2  and a timing detection window signal f outputted from the decoder  15  are corrected with precision of T/N by using a clock having a frequency of a value obtained by multiplying sampling frequencies of the first and second A/D converters  1  and  2  by a rate of interpolation N as the clock inputted to the counter  14 A. The counter  14 A is operated at a period of reception intervals of the known symbol. It is possible to adjust the reception time backward and forward by adjusting the counter  14 A. 
     A method of timing correction in the synchronization equipment according to the present embodiment will be described hereinafter with reference to FIGS. 17A to  17 C. Besides, it is assumed that the period of the counter  14 A is 11T on the convenience of explanation. 
     (1) When timing correction is not made: 
     As shown in FIG. 17A, the synchronization equipment is operated at the period of the counter  14 A (i.e. 11T). 
     (2) When timing correction is made backward: 
     For example, the reception time tmg of the known symbol is detected earlier than the optimum reception time (stored in the memory  220 ) by 1T, the output signal H of the timing lag detection circuit  219  shows a timing lag detection value a of −1T. Since the whole is shifted backward as timing correction at this time, the initial value of the counter  14 A is set to −1T which is the timing lag detection value when the counter value c becomes (10+2/3)T as shown in FIG.  17 B. 
     (3) When timing correction is made frontward: 
     For example, when the reception time tmg of the known symbol is detected later than the optimum reception time (stored in the memory  220 ) by 1T, the output signal H of the timing lag detection circuit  219  shows a timing lag detection value of +1T. Since the whole is shifted frontward as timing correction at this time, the initial value of the counter  14 A is set to +1T which is a timing lag detection value when the counter value c shows (10+2/3)T as shown in FIG.  17 C. 
     As described above, in the synchronization equipment according to the present embodiment, it is possible to correct the timing lag of a synchronizing signal automatically with a simple structure using the output signal H of the timing lag detection circuit  219  provided on the output side of the reception timing detection circuit  208 . 
     Besides, when the timing lag detection circuit  219  is provided on the output side of the reception timing detection circuit  208 A of the synchronization equipment according to the sixth embodiment shown in FIG. 13, it is also possible to structure a synchronization equipment in which similar effects are obtainable. 
     In the synchronization equipments according to the fifth to eighth embodiments of the present invention described above, it is possible to detect the known symbol accurately, and to detect the reception timing with high accuracy by detecting the reception time of the known symbol after interpolating the correlation value computed in the correlation circuit.