Patent Publication Number: US-7907591-B2

Title: Synchronization detecting circuit and multimode wireless communication apparatus

Description:
THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCT INTERNATIONAL APPLICATION PCT/JP2006/314236. 
     TECHNICAL FIELD 
     The present invention relates to a synchronization detecting circuit and a multimode wireless communication apparatus supporting plural wireless communication methods. 
     BACKGROUND ART 
     A multimode wireless communication apparatus supporting plural wireless communication methods is disclosed in such as Japanese Patent Unexamined Publication No. 2003-134569. 
     As shown in  FIG. 21 , a conventional multimode wireless communication apparatus has first cellular radio  1701 , second cellular radio  1702 , and control part  1703 . Usually, a multimode wireless communication apparatus, even while communicating by either one of the wireless communication methods of first cellular radio  1701  and second cellular radio  1702 , needs to always check whether or not communication by the other wireless communication method is possible, and thus has radios with two different wireless communication methods. This results in increased power consumption by an amount corresponding to the number of radios increased. In order to solve the problem, a conventional multimode wireless communication apparatus reduces its power consumption by control part  1703  controlling on and off of the power to first cellular radio  1701  and second cellular radio  1702 . 
     However, the above-described conventional makeup has plural radios to support plural wireless communication methods while sharing a control part. Accordingly, with conventional makeup, the circuit size grows as the number of radios increases, and thus the power consumption undesirably increases even if the control part controls on and off of the power to the radios. 
     SUMMARY OF THE INVENTION 
     The synchronization detecting circuit has a first converting part adjusting the sampling frequency of a receiving signal by a first wireless communication method; a second converting part adjusting the sampling frequency of a receiving signal by a second wireless communication method; an adding part combining digital signals output from the first and second converting parts; a delay part storing the combined signal from the adding part; a first synchronization detecting part detecting synchronization timing for the receiving signal by the first wireless communication method, from the combined signal stored in the delay part; and a second synchronization detecting part detecting synchronization timing for the receiving signal by the second wireless communication method, from the combined signal stored in the delay part. 
     With the makeup, the delay part can be shared among plural wireless communication systems, thereby reducing the size and power consumption of the synchronization detecting circuit. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating makeup of a multimode wireless communication apparatus according to the first exemplary embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating makeup of a synchronization detecting part detecting synchronization timing by cross-correlation operation, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 3  is a block diagram illustrating another makeup of the synchronization detecting part detecting synchronization timing by cross-correlation operation, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 4  is a block diagram illustrating makeup of a synchronization detecting part detecting synchronization timing by auto-correlation operation, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 5  is a block diagram illustrating makeup of a synchronization detecting part including a bit-shifting rate converting part, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 6  is a block diagram illustrating makeup of a synchronization detecting part including a time-division rate converting part, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 7  is a block diagram illustrating makeup of a synchronization detecting part including an A/D part-directly-controlling rate converting part, of the multimode wireless communication apparatus according to the first embodiment of the present invention. 
         FIG. 8  is a block diagram illustrating makeup of a multimode wireless communication apparatus according to the second exemplary embodiment of the present invention. 
         FIG. 9  illustrates makeup of a weight coefficient in the multimode wireless communication apparatus according to the second embodiment of the present invention. 
         FIG. 10  is a block diagram illustrating another makeup of the multimode wireless communication apparatus according to the second embodiment of the present invention. 
         FIG. 11  a block diagram illustrating still another makeup of the multimode wireless communication apparatus according to the second embodiment of the present invention. 
         FIG. 12  is a block diagram illustrating makeup of a multimode wireless communication apparatus according to the third exemplary embodiment of the present invention. 
         FIG. 13  illustrates makeup of a preamble signal in the multimode wireless communication apparatus according to the third exemplary embodiment of the present invention. 
         FIG. 14  illustrates an output signal supplied to the delay part of the multimode wireless communication apparatus according to the third exemplary embodiment of the present invention. 
         FIG. 15  is a block diagram illustrating another makeup of the multimode wireless communication apparatus according to the third exemplary embodiment of the present invention. 
         FIG. 16  illustrates the circumstances of switching of the output to the delay part of the multimode wireless communication apparatus according to the third embodiment of the present invention. 
         FIG. 17  is a block diagram illustrating a multimode wireless communication apparatus according to the fourth exemplary embodiment of the present invention. 
         FIG. 18  is a flowchart illustrating the operation of the communication area judging process of the multimode wireless communication apparatus according to the fourth embodiment of the present invention. 
         FIG. 19  is a block diagram illustrating makeup of a multimode wireless communication apparatus according to the fifth exemplary embodiment of the present invention. 
         FIG. 20  is a flowchart illustrating the operation of the communication area judging process of the multimode wireless communication apparatus according to the fifth embodiment of the present invention. 
         FIG. 21  is a block diagram illustrating makeup of a conventional multimode wireless terminal 
     
    
    
     REFERENCE MARKS IN THE DRAWINGS 
     
         
           100 ,  400 ,  500  Multimode wireless communication apparatus 
           110  First RF receiving part 
           111  Second RF receiving part 
           112  First A/D part 
           113  Second A/D part 
           121 ,  321  Synchronization detecting part 
           130  First baseband signal processing part 
           131  Second baseband signal processing part 
           120 ,  140 ,  320 ,  520  Control part 
           422 ,  442  Area judging part 
           523  Switch 
           530  Baseband signal processing part (Software signal processing part) 
           1211  First-wireless-system-use synchronization detecting part (First synchronization detecting part) 
           1212  Second-wireless-system-use synchronization detecting part (Second synchronization detecting part) 
           1213  Delay part 
           1214  Adding part 
           1215  First rate converting part (First converting part) 
           1216  Second rate converting part (Second converting part) 
           1217  First bit-shifting part 
           1218  Second bit-shifting part 
           1219  First constant delay part 
           1220  Second constant delay part 
           1221  First averaging part 
           1222  Second averaging part 
           1230  Weight coefficient adjusting part 
           12111 ,  12121  Weight coefficient 
           12112 ,  12122 ,  12114 ,  12124  Multiplying part 
           12113 ,  12123  Adding part 
           1501 ,  1502  Switch 
           1701 ,  1702  Cellular radio 
           1703  Control part 
           2217  Filter 
           3215  First buffer (First converting part) 
           3216  Second buffer (Second converting part) 
           3217  Third buffer (Replica accumulating part) 
           3218  Switch 
       
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, a description is made for some embodiments of the present invention, using the related drawings. 
     First Exemplary Embodiment 
       FIG. 1  is a block diagram illustrating makeup of multimode wireless communication apparatus  100  according to the first exemplary embodiment of the present invention. 
     In  FIG. 1 , multimode wireless communication apparatus  100  includes first RF receiving part  110 , second RF receiving part  111 , first A/D part  112 , second A/D part  113 , synchronization detecting part  121 , first baseband signal processing part  130  as a first signal processing part, and second baseband signal processing part  131  as a second signal processing part. 
     First RF receiving part  110 , first A/D part  112 , and first baseband signal processing part  130  process a radio-frequency signal of a first wireless system in a first wireless communication method; and second RF receiving part  111 , second A/D part  113 , second baseband signal processing part  131  process a radio-frequency signal of a second wireless system in a second wireless communication method. 
     First RF receiving part  110  converts the radio-frequency signal of the first wireless system, supplied from the antenna, to an intermediate-frequency analog signal, and then outputs it to first A/D part  112 . First A/D part  112  converts the analog signal entered to a digital signal, and then outputs it to synchronization detecting part  121  and first baseband signal processing part  130 . 
     Second RF receiving part  111  converts the radio-frequency signal of the second wireless system, supplied from the antenna, to an intermediate-frequency analog signal, and then outputs it to second A/D part  113 . Second A/D part  113  converts the analog signal entered to a digital signal, and then outputs it to synchronization detecting part  121  and second baseband signal processing part  131 . 
     When synchronization detecting part  121 , connected to first A/D part  112  and second A/D part  113 , is supplied with the digital signal of the first wireless system, output from first A/D part  112 ; and that of the second wireless system, output from second A/D part  113 , part  121  detects timing for both signals. 
     For example, synchronization detecting part  121  has a function for detecting timing of removing a guard interval for OFDM (Orthogonal Frequency Division Multiplexing) as a wireless communication method; a function for detecting timing of a symbol, slot, and frame required for despreading for CDMA (Code Division Multiple Access). Timings for the two wireless communication methods, detected by synchronization detecting part  121  are output to first baseband signal processing part  130  and second baseband signal processing part  131 , respectively. 
     First baseband signal processing part  130  performs digital signal processing such as demodulation for the digital signal supplied from first A/D part  112  on the basis of timing supplied from synchronization detecting part  121 . Second baseband signal processing part  131  performs digital signal processing such as demodulation for the digital signal supplied from second A/D part  113  on the basis of timing supplied from synchronization detecting part  121 . 
     In the first embodiment, a description is made for the case where the first wireless system uses IEEE 802.11a as the first wireless communication method; and the second wireless system, W-CDMA (Wideband-Code Division Multiple Access) as the second wireless communication method. 
     Synchronization detecting part  121  detects timing for synchronization with a preamble signal for IEEE 802.11a; and with a spread code for W-CDMA. The sampling rate corresponding to the basic sampling frequency in IEEE 802.11a is 20 M samples/second, and the chip rate corresponding to the basic sampling frequency in W-CDMA is 3.84 M chips/second, and thus sampling frequencies of digital signals fed into synchronization detecting part  121  are different between the case where multimode wireless communication apparatus  100  is communicating by IEEE 802.11a and that by W-CDMA. 
       FIG. 2  is a block diagram illustrating makeup of synchronization detecting part  121  detecting synchronization timing by cross-correlation operation, of multimode wireless communication apparatus  100  according to the first embodiment. Synchronization detecting part  121  includes first rate converting part  1215  as a first converting part that converts the sampling frequency of a receiving signal received by the first wireless communication method and outputs the digital signal; second rate converting part  1216  as a second converting part that converts the sampling frequency of a receiving signal received by the second wireless communication method and outputs the digital signal; adding part  1214  that combines digital signals with their sampling frequencies converted from receiving signals by first rate converting part  1215  and second rate converting part  1216 ; delay part  1213  composed of plural delay elements cascaded (shown by “D” in the figure) that stores and delays combined signals supplied from adding part  1214 ; first-wireless-system-use synchronization detecting part  1211  as a first synchronization detecting part that detects synchronization timing for the receiving signal by the first wireless communication method, from the combined signal stored and delayed by delay part  1213 ; and second-wireless-system-use synchronization detecting part  1212  as a second synchronization detecting part that detects synchronization timing for the receiving signal by the second wireless communication method, from the combined signal stored and delayed by delay part  1213 . Here, delay parts  1213  composed of plural delay elements shown by “D” in the figure are cascaded with each other. Because there are a large number, only some of them are shown for simplicity. In the drawings hereinafter, delay parts  1213  are indicated in the same way. 
     First-wireless-system-use synchronization detecting part  1211  includes multiplying part  12112  composed of plural multipliers, and adding part  12113 . Multiplying part  12112  multiplies weight coefficient  12111  (indicated as b 0 , b 1 , . . . , b M−1  (M is a positive integer) in the figure), by plural digital signals stored in delay part  1213  and additionally corresponding to weight coefficient  12111 , and then outputs the products to adding part  12113 . The sum calculated by adding part  12113  is output to first baseband signal processing part  130 . Part  1211  performs such correlation operation for detecting synchronization timing for the first wireless system. Here, if the first wireless system uses IEEE 802.11a, weight coefficient  12111  uses the preamble signal in IEEE 802.11a. 
     Second-wireless-system-use synchronization detecting part  1212  includes multiplying part  12122  composed of plural multipliers, and adding part  12123 . Multiplying part  12122  multiplies weight coefficient  12121  (indicated as a 0 , a 1 , . . . , a M−1 , . . . , a N−1  (M, N are positive integers) in the figure), by the plural digital signals stored in delay part  1213  and additionally corresponding to weight coefficient  12121 , and then outputs these products to adding part  12123 . The sum calculated by adding part  12123  is output to second baseband signal processing part  131 . Part  1212  performs such correlation operation for detecting synchronization timing for the second wireless system. Here, if the second wireless system uses W-CDMA, weight coefficient  12121  uses the spreading code in W-CDMA. Weight coefficients  12111 ,  12121  can be preliminarily prepared as tap coefficients or can be read from such as a memory. 
     In the first exemplary embodiment, the first wireless system uses IEEE 802.11a and the second wireless system uses W-CDMA, thus first rate converting part  1215  and second rate converting part  1216  output a sampling frequency being oversampled to the same sampling frequency (i.e. 480 MHz), which is the minimum from among integral multiples of sample rates or chip rates in both methods, to adding part  1214 . That is, first rate converting part  1215  oversamples the digital signal in IEEE 802.11a entered by 24 times and outputs it; second rate converting part  1216  oversamples the digital signal in W-CDMA entered by 125 times and outputs it. 
     Adding part  1214  combines these two digital signals and outputs the results to delay part  1213 . In the makeup as shown in  FIG. 2 , synchronization detecting part  121  performs correlation operation for all the samples of combined signals. That is, delay part  1213  is supplied with the oversampled digital signals in each wireless communication method. Then, first-wireless-system-use synchronization detecting part  1211  uses the preamble signal in IEEE 802.11a oversampled by 24 times with weight coefficient  12111 . Meanwhile, second-wireless-system-use synchronization detecting part  1212  uses the spreading code in W-CDMA oversampled by 125 times with weight coefficient  12121 . 
     At this moment, weight coefficient  12111  remains the same value 24 (corresponding to the oversampling number) times continuously, and thus b 0  through b 23 , b 24  through b 47 , . . . , b 24×K  through b 24×(K+1)−1  (K is a positive integer) are all the same, and weight coefficient  12121  remains the same value 125 (corresponding to the oversampling number) times continuously, and thus a 0  through a 124 , a 125  through a 249 , . . . , a 125×L  through a 125×(L+1)−1  (L is a positive integer) are all the same as well. For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, 7,680 (=320×24) pieces of weight coefficients  12111  and multiplying parts  12112 , and 32,000 (=256×125) pieces of weight coefficients  12121  and multiplying parts  12122  are required. For delay part  1213 , 32,000 pieces, which is the larger one out of the required numbers of weight coefficients and multiplying parts in the two methods, of delay elements are required. 
     First-wireless-system-use synchronization detecting part  1211  and second-wireless-system-use synchronization detecting part  1212  can be configured as shown in  FIG. 3  as well.  FIG. 3  is a block diagram illustrating another makeup of synchronization detecting part  121  detecting synchronization timing by cross-correlation operation, of multimode wireless communication apparatus  100  according to the first embodiment. 
     Next, a description is made for the differences of first-wireless-system-use synchronization detecting part  1211  and second-wireless-system-use synchronization detecting part  1212  in  FIG. 3  from those in  FIG. 2 . 
     In  FIG. 2 , second-wireless-system-use synchronization detecting part  1212  is supplied in parallel with signals without delay output from adding part  1214  and with signals output from all the delay elements of delay part  1213 . First-wireless-system-use synchronization detecting part  1211  is supplied in parallel with signals without delay output from adding part  1214  and with signals output not from all the plural delay elements of delay part  1213 , but from delay elements continuously cascaded up to a required stage number. 
     In  FIG. 3 , on the other hand, second-wireless-system-use synchronization detecting part  1212  is supplied directly with the signal without delay output from adding part  1214  to delay part  1213 , which is the same as in  FIG. 2 . However, part  1212  is supplied in parallel not with signals output from all the delay elements of delay part  1213 , but with signals output from delay elements with discontinuous stage numbers (i.e. skipping a given number of delay elements). 
     First-wireless-system-use synchronization detecting part  1211  is supplied directly with the signal without delay output from adding part  1214  to delay part  1213 , which is the same as in  FIG. 2 . However, part  1211  is supplied in parallel not with signals output from all the delay elements of delay part  1213 , but with signals output from delay elements with discontinuous stage numbers (i.e. skipping a given number (generally different from that in second-wireless-system-use synchronization detecting part  1212 ) of delay elements out of those continuously cascaded up to a required stage number). Accordingly, weight coefficients  12111  and  12121  are indicated as b 0 , b 1 , . . . , b M′−1  and a 0 , a 1 , . . . , a N′−1  (M′, N′ are positive integers) in the figure, respectively. 
     If synchronization detecting parts  1211  and  1212  in each wireless system are composed as shown in  FIG. 3 , synchronization detecting part  121  does not perform correlation operation for all the samples, but only for samples required for detecting synchronization timing. This enables reducing the numbers of weight coefficients  12111 , weight coefficients  12121 , multiplying parts  12112 , and multiplying parts  12122 , compared to the composition shown in  FIG. 2 . For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, 32,000 pieces of delay parts  1213  are required in the same way as in  FIG. 2 . However, weight coefficients  12111  and multiplying parts  12112  need to be arranged only by 320 pieces in total at every 24 pieces of delay elements of delay part  1213 . In the same way, weight coefficients  12121  and multiplying parts  12122  need to be arranged by 256 pieces in total at every 125 pieces of delay elements of delay part  1213 . 
       FIGS. 2 and 3  illustrate makeup for performing cross-correlation operation for detecting synchronization timing. However, makeup for performing auto-correlation operation as shown in  FIG. 4  is also possible.  FIG. 4  is a block diagram illustrating makeup of synchronization detecting part  121  detecting synchronization timing by auto-correlation operation, of multimode wireless communication apparatus  100  according to the first embodiment. The makeup shown in  FIG. 4  is different from that in  FIGS. 2 and 3  in that multiplying parts  12114 ,  12124  multiply the digital signals delayed by a certain period by first constant delay part  1219  and second constant delay part  1220 , by the digital signals combined by adding part  1214 , respectively, to perform correlation (inner product) operation. Here, “a certain period” represents time corresponding to the repetition cycle of a known signal for each wireless system used for correlation detection in each synchronization detecting part, where generally each period is different from the other. Another difference is that first averaging part  1221  and second averaging part  1222  are provided that perform averaging process over a given period after correlation (inner product) operation. “A given period” during which averaging process is performed represents time corresponding to the repetition cycle of a known signal for each wireless system used for correlation detection in each synchronization detecting part, where generally each period is different from the other. 
     In  FIG. 4 , first constant delay part  1219  delays the digital signal supplied from first rate converting part  1215  by a certain period predetermined and then outputs it. Second constant delay part  1220  delays the digital signal supplied from second rate converting part  1216  by a certain period predetermined and then outputs it. In the first embodiment, the first wireless system uses IEEE 802.11a and the second wireless system uses W-CDMA, thus periods delayed by first constant delay part  1219  and second constant delay part  1220  are predetermined. For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, first constant delay part  1219  delays by the equivalent of 7,680 samples; and second constant delay part  1220 , by the equivalent of 32,000 chips. 
     After multiplying part  12114  multiplies a digital signal delayed by a certain period by first constant delay part  1219 , by the digital signal output from adding part  1214 , first averaging part  1221  performs averaging process over a certain period, and accordingly first-wireless-system-use synchronization detecting part  1211  performs auto-correlation operation for detecting synchronization timing for the first wireless system. 
     Meanwhile, after multiplying part  12124  multiplies a digital signal delayed by a certain period by first constant delay part  1220 , by the digital signal output from adding part  1214 , second averaging part  1222  performs averaging process over a certain period, and accordingly second-wireless-system-use synchronization detecting part  1212  performs auto-correlation operation for detecting synchronization timing for the second wireless system. Although the makeup as shown in  FIG. 4  is lower in the accuracy of detecting synchronization timing than that in  FIGS. 2 and 3 , the number of multiplying parts can be reduced, thereby contracting the circuit scale of synchronization detecting part  121 . In  FIG. 4 , the output from multiplying part  12114  and multiplying part  12124  needs to undergo averaging process over a given section as described above. However, each output may undergo averaging process internally after it is fed into first baseband signal processing part  130  or second baseband signal processing part  131  in  FIG. 1 , where these two averaging parts  1221  and  1222  may be dispensed with. 
       FIG. 5  is a block diagram illustrating makeup of synchronization detecting part  121  having a bit-shifting rate converting part, of multimode wireless communication apparatus  100  according to the first embodiment.  FIG. 5  illustrates the makeup shown in  FIG. 2  further having first bit-shifting part  1217  and second bit-shifting part  1218 . Parts  1217  and  1218  bit-shift the digital signal entered and then output it. For example, if the digital signal in the first wireless system has a bit width for 32-bit operation; and the second, 16-bit, second bit-shifting part  1218  bit-shifts the digital signal by 16 bits, and accordingly adding part  1214 , multiplying part  12112 , and multiplying part  12122  can operate in 32 bits. Thus, synchronization detecting part  121  further has first bit-shifting part  1217  and second bit-shifting part  1218  as a bit-shifting part that matches the number of bits for operation by first-wireless-system-use synchronization detecting part  1211  as the first synchronization detecting part and second-wireless-system-use synchronization detecting part  1212  as the second synchronization detecting part. 
     This makeup allows synchronization detecting part  121  to detect synchronization timing accurately even if the digital signals in the first and second wireless systems are different in their bit width, where weight coefficients  12111  and  12121  need to be prepared preliminarily. 
     As described above, synchronization detecting part  121  of multimode wireless communication apparatus  100  according to the first embodiment, with adding part  1214  shown in  FIGS. 2 through 5 , combines the digital signals in the first and second wireless systems and simultaneously detects synchronization timing for the two wireless systems. If combining the digital signals in this way, although the digital signals in each wireless system become noise components for the other, synchronization timing can be detected because known signals in a wireless system, such as the preamble signal and the spreading code for synchronization detection, generally has a low correlation with receiving signals in another wireless system. 
     Under the circumstances, multimode wireless communication apparatus  100 , further having an RF receiving part, A/D part, and baseband signal processing part of a wireless system different from the first and second wireless systems, combines the digital signals in three or more wireless communication methods, and accordingly can detect synchronization for each wireless communication system as well. Alternatively, when a wireless system has spare time in a resting state such as in communication idle time (e.g. standby), synchronization timing may be detected for the first and second wireless systems by time division. 
       FIG. 6  is a block diagram illustrating makeup of synchronization detecting part  121  having a time-division rate converting part, of multimode wireless communication apparatus  100  according to the first embodiment.  FIG. 6  is different from  FIG. 2  in that control part  120  is provided that controls whether or not synchronization timing is to be detected simultaneously, and switches  1501  and  1502  are further provided that switch the input from first rate converting part  1215  as the first converting part and second rate converting part  1216  as the second converting part, to adding part  1214 . While the first or second wireless communication method performing communication is in a resting state, controlling switch  1501  and switch  1502  allows detecting synchronization timing in the first or second wireless communication method in a resting state, by time division. In addition, with switches  1501  and  1502  controlled by control part  120 , the output from first rate converting part  1215  and second rate converting part  1216  can be combined and output simultaneously, or can be output separately to delay part  1213  by time division. Thus, outputting by time division enables detecting synchronization timing further highly accurately because while a wireless system is not communicating, a noise component does not occur in the other wireless system. 
     Furthermore, control part  140  can be provided that controls a sampling frequency of the digital signals output from first A/D part  112  and second part A/D  113  as shown in  FIG. 7 .  FIG. 7  is a block diagram illustrating makeup of synchronization detecting part  121  having an A/D part-directly-controlling rate converting part, of multimode wireless communication apparatus  100  according to the first embodiment.  FIG. 7  is different from  FIG. 2  in that first rate converting part  1215  and second rate converting part  1216  that are required in synchronization detecting part  121  shown in  FIG. 2  are dispensed with because control part  140  directly controls first A/D part  112  and second A/D part  113  to convert the sampling frequency instead of arranging each rate converting part to control the sampling frequency for the digital signals output from each A/D part. 
     In the first exemplary embodiment, the first and second wireless systems use IEEE 802.11a and W-CDMA, but not limited to. The sampling rate and chip rate in the two wireless communication methods are not particularly limited. The rate converting part can use zero insertion, interpolation filter, linear interpolation, zero-order hold, and others. In  FIGS. 5 ,  6 , and  7 , correlation operation is performed for all the samples in the same way as in  FIG. 2 . However, correlation operation can be performed only for samples required for detecting synchronization timing in the same way as in  FIG. 3 , or auto correlation can be performed in the same way as in  FIG. 4 . 
     As described above, multimode wireless communication apparatus  100  according to the first embodiment is characterized in that detection of synchronization timing performed by first-wireless-system-use synchronization detecting part  1211  as the first synchronization detecting part and second-wireless-system-use synchronization detecting part  1212  as the second synchronization detecting part is executed on the basis of the result of correlation operation between a specific code preliminarily prescribed for the first or second wireless communication method, namely a weight coefficient; and the combined signal of the digital signals stored in delay part  1213 , according to a sampling frequency. Thus, synchronization timing can be detected even for the combined signal by both wireless communication methods. 
     As described above, according to the present invention, a delay part for detecting synchronization timing can be shared among plural wireless communication systems, thereby contracting the circuit scale of a multimode wireless communication apparatus according to the present invention along with reducing the power consumption. 
     Second Exemplary Embodiment 
     In the first embodiment, the sampling frequency is set to the same one that is the minimum from among integral multiples of sampling rates or chip rates in different wireless communication methods. In the second embodiment, the sampling frequency is set to an integral multiple of the larger one out of sampling rates or chip rates in the first and second wireless systems. In the second embodiment, the first wireless system is assumed to use IEEE 802.11a; and the second, W-CDMA as well as in the first embodiment. For example, the sampling frequency is assumed to be 80 MHz, which is 4 times a sampling rate of 20 M samples/second in IEEE 802.11a of the first wireless system with the larger sampling rate. 
       FIG. 8  is a block diagram illustrating makeup of synchronization detecting part  121  of multimode wireless communication apparatus  100  according to the second embodiment of the present invention. In  FIG. 8 , the second embodiment is different from the first in that synchronization detecting part  121  has weight coefficient adjusting part  1230 . 
     Weight coefficient adjusting part  1230  adjusts the repetition number of a weight coefficient to adjust a fraction if the sampling frequency is not an integral multiple of the own sampling rate. Concretely, weight coefficient  12111  uses a signal oversampled by 4 times the preamble signal in IEEE 802.11a, and weight coefficient  12121  uses a signal oversampled by approximately 21 (≈80/3.84) times the spreading code in W-CDMA. 
     That is, each element of weight coefficient  12111  remains the same value 4 times continuously in ascending order of element numbers, and thus b 0  through b 3 , b 4  through b 7 , . . . , b 4×K  through b 4×(k+1)−1  (K is a positive integer) are the same value. Meanwhile, each element of weight coefficient  12121  remains the same 20 times or 21 times continuously in ascending order of element numbers because the oversampling rate 80/3.84 is not an integer. That is, a 0  through a 19 , a 20  through a 40 , a 41  through a 61 , . . . , a X  through a X+19 , a X+20  through a X+40 , . . . , a Y  through a Y+20  (X, Y are positive integers) are the same value. Weight coefficient adjusting part  1230  manages this repetition number so that the weight coefficient of the second system will be adjusted to the same value 80/3.84 times continuously on average. For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, 1,280 (=320×4) pieces of weight coefficients  12111  and multiplying parts  12112  are required, and 5,333 (≈256×80/3.84) pieces of weight coefficients  12121  and multiplying parts  12122  are required. For delay parts  1213 , 5,333 pieces, the larger one, are required. 
       FIG. 9  illustrates circumstances of repeating of weight coefficient  12121  in this case. The number of weight coefficients required for 6 chips, for example, is calculated to obtain a round figure as 6×80/3.84=125. Meanwhile, 256=6×42+4, and thus from 125 (i.e. the equivalent of 6 chips) and 83 (i.e. the equivalent of remaining 4 chips), a calculation can be made as 5,333=125×42+83, 125=(20+21+21+21+21+21), and 83=(20+21+21+21). That is, 5,250 (=125×42) pieces out of all the weight coefficients represent 252 (=6×42) chips of the spreading codes, and 83 pieces of remaining weight coefficients represent 4 chips of the spreading codes, to represent 256 chips of the spreading codes. 
     As described above, if the number corresponding to the number of samples per one chip is 20 or 21, how 20 samples/chip or 21 samples/chip are arranged does not particularly matter. The above description is only an example and not limited. 
     First-wireless-system-use synchronization detecting part  1211  and second-wireless-system-use synchronization detecting part  1212  can have the same makeup as in  FIG. 3  of the first exemplary embodiment. In this case, correlation operation is not performed for all the samples, but for samples required for detecting synchronization timing in the same way as in the first embodiment. This allows reducing the numbers of weight coefficients  12111 , weight coefficients  12121 , multiplying parts  12112 , and multiplying parts  12122 . For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, 5,333 pieces of delay parts  1213  are required in the same way as in  FIG. 8 . However, weight coefficients  12111  and multiplying parts  12112  need to be arranged only by 320 pieces at every 4 pieces of delay parts  1213 . In the same way, weight coefficients  12121  and multiplying parts  12122  need to be arranged only by 256 pieces at every 20 or 21 pieces of delay parts  1213 . 
     Furthermore, in the second embodiment, the sampling frequency of second A/D part  113  (not shown in  FIG. 8 ) and that of second rate converting part  1216  are not in a relationship of integral multiple, thus generating an unnecessary frequency component in the output from second rate converting part  1216 . Accordingly, as shown in  FIG. 10 , filter  2217  may be inserted between second rate converting part  1216  and adding part  1214  to remove an unnecessary frequency component in the output from second rate converting part  1216 .  FIG. 10  is a block diagram illustrating another makeup of synchronization detecting part  121  of multimode wireless communication apparatus  100  according to the second embodiment. With this makeup, correlation operation is possible with the influence of an unnecessary frequency component reduced. In order to remove an unnecessary frequency component, the first and second rate converting parts can be made of a combination of an interpolation filter and decimation filter. 
     In this embodiment, the first and second wireless systems use IEEE 802.11a and W-CDMA, but not limited to, and makeup of the rate converting part does not particularly matter. The rate converting part may be bit-shifting, with a function of bit-shifting the digital signals as shown in  FIG. 5 ; time-division, with a function of switching the input to the adding part as shown in  FIG. 6 ; or A/D part-directly-controlling, with a function of controlling the sampling frequency of the digital signals as shown in  FIG. 7 . 
     In addition, the sampling frequency is not set to an integral multiple of the largest sampling rate or chip rate, out of those in plural wireless systems, but may be set to an integral multiple of a sampling rate or chip rate other than the largest one and additionally larger than the largest sampling rate or chip rate. Alternatively, the largest sampling rate or chip rate may be directly the sampling frequency, where first rate converting part  1215  can be omitted as shown in  FIG. 11 . 
     For example, if the preamble signal in IEEE 802.11a consists of 320 samples, and the spreading code in W-CDMA consists of 256 chips, 320 pieces of weight coefficients  12111  and multiplying parts  12112  are required, and 1,333 (≈ 256 ×20/3.84) pieces of weight coefficients  12121  and multiplying parts  12122  are required. For delay parts  1213 , 1,333 pieces, the larger one, are required. Weight coefficient  12121  in this case is represented in the same way as in  FIG. 9 . That is, 1,250 (=125×10) pieces out of all the weight coefficients represent 240 (=24×10) chips of the spreading codes, and 83 pieces of remaining weight coefficients represent 16 chips of the spreading codes, to represent 256 chips of the spreading codes. Here, with such as 125=19×5+5×6, and 83=13×5+3×6, each group of the coefficients is represented as 5 samples/chip, or 6 samples/chip. 
     As described above, if the number corresponding to the number of samples per one chip is 5 or 6, how 5 samples/chip or 6 samples/chip are arranged does not particularly matter. The above description is only an example and not limited. 
     As described above, multimode wireless communication apparatus  100  according to the second embodiment allows the delay part for detecting synchronization timing to be shared among plural wireless communication systems, thereby contracting the circuit scale of multimode wireless communication apparatus  100  along with reducing the power consumption. 
     Third Exemplary Embodiment 
       FIG. 12  is a block diagram illustrating makeup of synchronization detecting part  321  of multimode wireless communication apparatus  100  according to the third embodiment of the present invention. 
     Synchronization detecting part  321  in  FIG. 12  is different from synchronization detecting part  121  in  FIG. 2  in that part  321  has first buffer  3215  as the first converting part and second buffer  3216  as the second converting part, instead of first rate converting part  1215  as the first converting part and second rate converting part  1216  as the second converting part, in  FIG. 2 , and in that part  321  further has control part  320  directing output to the first and second buffers. 
     Control part  320  outputs a control signal to first buffer  3215  and second buffer  3216  so that digital signals stored in first buffer  3215  and second buffer  3216  will be output when detecting synchronization timing becomes necessary. 
     First buffer  3215  outputs the digital signals stored until detecting of synchronization timing completes, on the basis of a control signal entered from control part  320 , and also stores the digital signals entered from first A/D part  112  (not shown in  FIG. 12 ). Second buffer  3216  outputs the digital signals stored until detecting of synchronization timing completes, on the basis of the control signal entered from control part  320 , and also stores the digital signals entered from second A/D part  113  (not shown in  FIG. 12 ). 
     In the third embodiment, first buffer  3215  and second buffer  3216  are assumed to operate with the same timing due to the common clock. In the same way as in the first embodiment, the first wireless system is assumed to use IEEE 802.11a; and the second, W-CDMA. In this case, the preamble signal in IEEE 802.11a is composed of 10 pieces of short symbols (SS 0 , . . . , SS 9 =16×10 samples), the guard interval between long symbols, and two long symbols (LS 0 , LS 1 =64×2 samples), as shown in  FIG. 13 . The number of delay parts  1213  required for detecting synchronization timing is determined by which symbol is used in the preamble signal for detecting synchronization. Although the whole preamble signal (320 samples) can be used as in the first or second embodiment, only one long symbol in the preamble signal can be used, where 64 pieces of delay parts  1213  are required. 
     Meanwhile, the length (timewise length of a repeated code pattern) of the spreading code in W-CDMA is 256, and thus the number of delay parts  1213  required for detecting synchronization timing is 256. In the third embodiment, the number of delay elements of delay part  1213  required for detecting synchronization timing is equal to the larger one out of those required in the first and second wireless systems, and thus synchronization detecting part  321  results in being composed of delay part  1213  including 256 pieces of delay elements; multiplying part  12112  including weight coefficient  12111  with 64 elements and 64 pieces of multipliers; and multiplying part  12122  including weight coefficient  12121  with 256 elements and 256 pieces of multipliers. 
     That is, in multimode wireless communication apparatus  100  according to the third embodiment, first buffer  3215  as the first converting part and second buffer  3216  as the second converting part are buffers for accumulating the digital signals, and output the digital signals accumulated with their timing adjusted according to the number of delay parts  1213 . 
     The sampling rate in IEEE 802.11a is 20 M samples/second, and the chip rate in W-CDMA is 3.84 M chips/second. Accordingly, if first buffer  3215  and second buffer  3216  output the digital signals stored in each buffer at the same timing, the digital signals output from second buffer  3216  have a smaller number of samples (chips) not oversampled than those output from first buffer  3215 . Control part  320  thus controls second buffer  3216  so that the digital signals output from second buffer  3216  will be in a burst way. 
     For example, control is possible where output is stopped for a certain period until 256 chips of the digital signals are stored in second buffer  3216  after 256 (same as the number of delay elements of delay part  1213 ) chips of the digital signals are continuously output. In this case, while 256 chips in W-CDMA are accumulated in second buffer  3216  in 0.0000667 (≈256/3.84 M) seconds, 1,333 (≈20 M×256/3.84 M) samples in IEEE 802.11a are input into first buffer  3215 . 
     A description is made for the above process, using the related drawings.  FIG. 14  illustrates output signals to the delay part of the multimode wireless communication apparatus according to the third embodiment of the present invention, where the horizontal axis indicates elapsed time in the right direction. The upper part of  FIG. 14  shows signal xs output from first buffer  3215 ; and the lower, signal ys output from second buffer  3216 . As shown in the figure, control is performed where continuous 256 chips of signals ys are output from second buffer  3216  in a burst way at intervals of 1333, 1333, 1334 samples at which x 0 , x 1333 , x 2666 , x 4000 , . . . are output from first buffer  3215 . In other words, burst output t S2  of the output from second buffer  3216  is repeated at every burst output t S1  of the output from first buffer  3215 . 
     In the above-described example, distribution is made as 4000=1333+1333+1334, considering that time equivalent to 256 chips is 1 cycle for 3 periods because (20 M×256/3.84 M)×3=4000, but the way of distribution is not limited to this one. 
     Meanwhile, when second-wireless-system-use synchronization detecting part  1212  performs correlation operation for the digital signals output in a burst way, if synchronization timing falls at the vicinity of both ends (i.e. the beginning and ending) of 256 chips output in a burst way, accurately detecting synchronization timing is difficult. The reason is that the averaging process performed for correlation over a certain section is highly likely to be interrupted at the vicinity of both ends of the burst output. 
     Consequently, as shown in  FIG. 15 , in order to save a replica of the digital signal output from second buffer  3216 , third buffer  3217  as a replica accumulating part; and switch  3218  for switching the output from second buffer  3216  and third buffer  3217  to adding part  1214  are provided, and the replica accumulated is output from third buffer  3217  before outputting next 256 chips of the digital signals after 256 chips are output from second buffer  3216  at the current time in a burst way. Such makeup allows accurate detection of synchronization timing. 
       FIG. 16  illustrates timing at this moment of switching the output to delay part  1213  through adding part  1214 , by operating switch  3218  by control part  320 , schematically indicating circumstances in which control part  320  controls switch  3218  to switch the output to adding part  1214 . 
     In  FIG. 16 , the horizontal axis indicates elapsed time in the right direction. The upper part shows circumstances of output signal  20  from second buffer  3216 ; and the middle and lower parts, output signals  31  and  32  from third buffer  3217 , respectively. 
     First, control part  320  makes second buffer  3216  output digital signal  22  and controls switch  3218  so that digital signal  22  will be supplied to adding part  1214  during time t 0  to t 1 . Simultaneously, control part  320  controls third buffer  3217  so that digital signal  22  will be stored in third buffer  3217  as well. 
     Next, control part  320  does not especially perform concrete control during time t 1  to t 2 , when the digital signal is not output from second buffer  3216 . 
     Next, control part  320  makes third buffer  3217  output a replica of digital signal  22  at time point t 2 , prior to t 3 , when t 3  at which digital signal  33  is output from second buffer  3216  approaches. Then, during time t 2  to t 3 , while the replica of digital signal  22  is being output from third buffer  3217 , control part  320  controls switch  3218  so that the replica of digital signal  22  will be output to adding part  1214 . 
     Next, during time t 3  to t 4 , while digital signal  33  is being output from second buffer  3216 , control part  320  makes second buffer  3216  output digital signal  33  and controls switch  3218  so that digital signal  33  will be supplied to adding part  1214 . Simultaneously, control part  320  controls third buffer  3217  so that digital signal  33  will be stored in third buffer  3217  as well. By repeating this series of operation, the digital signal output in a burst way at a certain time point, continuously with that output in a burst way immediately before, is to be supplied to delay part  1213  through adding part  1214 . 
     Here, a replica accumulated in third buffer  3217  does not need to be composed of all the 256 chips as described above, but of only a data amount with which a timing signal for synchronization at the vicinity of both ends of the digital signal output from second buffer  3216  can be detected. For example, as shown in the lower part of  FIG. 16 , control part  320  may make output signal  32  from the third buffer output a part of digital signal  22  from third buffer  3217  to adding part  1214 , at t 21 , prior to time point t 3  and additionally after time point t 2 . With such operation, accurate synchronization timing is available without accumulating all the 256 chips as the replica. 
     Here, in the above-described two cases, time period during which signal output to adding part  1214  continues corresponds to time t 2  to t 4  for output signal  31  from the third buffer shown in the middle part of  FIG. 16 ; and time t 21  to t 4  for output signal  32  from the third buffer shown in the lower part. 
     Further, the function of third buffer  3217  can be incorporated in second buffer  3216  to output the replica of digital signal  22  and digital signal  33  continuously. 
     As described above, multimode wireless communication apparatus  100  of the third embodiment further includes third buffer  3217  as the replica accumulating part that accumulates the digital signals same as all of those accumulated in second buffer  3216  as the second converting part, or part of those from an end, and is characterized in that the replica accumulating part completes outputting of digital signals to adding part  1214  previously accumulated before the second converting part starts outputting the digital signals. Thus, delay part  1213  can be shared among plural wireless communication systems, thereby reducing the size and power consumption of multimode wireless communication apparatus  100 . Multimode wireless communication apparatus  100  according to the third embodiment can detect synchronization timing at a low sampling frequency only when necessary and with both ends of the sampled receiving signal corrected, thereby allowing highly accurate detection of synchronization timing. 
     In this embodiment, the first and second wireless systems are assumed to use IEEE 802.11a and W-CDMA, but not limited to. 
     As described above, according to the present invention, the delay part for detecting synchronization timing can be shared among plural wireless communication systems, thereby reducing the circuit scale of multimode wireless communication apparatus  100 . 
     Multimode wireless communication apparatus  100  according to the third embodiment is characterized in that the first and second converting parts are buffers for accumulating receiving signals and output the digital signals accumulated with their timing adjusted according to the number of delay parts  1213 . Delay part  1213  thus can be shared among plural wireless communication systems, and synchronization timing can be detected at the low sampling frequency only when necessary. Consequently, multimode wireless communication apparatus  100  in the third embodiment can detect synchronization timing at a lower sampling frequency than that in the first embodiment, thereby further reducing the power consumption. 
     Fourth Exemplary Embodiment 
       FIG. 17  is a block diagram illustrating makeup of multimode wireless communication apparatus  400  according to the fourth exemplary embodiment of the present invention. As shown in  FIG. 17 , multimode wireless communication apparatus  400  of the fourth embodiment further includes area judging part  422  in addition to the makeup of multimode wireless communication apparatus  100  of the first embodiment. 
     Area judging part  422  judges that the communication apparatus is within a communication service area if the peak value of the results of correlation operation entered from synchronization detecting part  121  exceeds a given threshold; and out of the communication service area, otherwise. Further, area judging part  422  outputs a signal for turning on/off of the power, to first baseband signal processing part  130  and second baseband signal processing part  131  on the basis of the judgement result for the first and second wireless systems. 
       FIG. 18  is a flowchart illustrating the operation of communication area judging process of multimode wireless communication apparatus  400  according to the fourth embodiment. The operation of multimode wireless communication apparatus  400  shown in  FIG. 17  is described using the flowchart of  FIG. 18 . 
     First, area judging part  422  judges whether or not the communication apparatus is within an area communicatable by the first wireless system on the basis of the result of correlation operation by synchronization detecting part  1211  (step S 401 ). If judged as out of the communication service area (“No” in S 401 ), namely if the first wireless system is not available for communication, area judging part  422  turns off the power to first baseband signal processing part  130  (step S 407 ), and then the process proceeds to step S 403 . 
     Meanwhile, if judged as within the communication service area (“Yes” in S 401 ), namely if the first wireless system is available for communication, area judging part  422  checks the state of the power to first baseband signal processing part  130  (step S 402 ). Then, if the power to first baseband signal processing part  130  is on (“Yes” in S 402 ), the process proceeds to step S 403 . If off (“No” in S 402 ), however, area judging part  422  turns on the power to first baseband signal processing part  130  (step S 405 ), and then the process proceeds to step S 403 . 
     Next, area judging part  422  judges whether or not the communication apparatus is within the area communicatable by the second wireless system on the basis of the result of correlation operation by synchronization detecting part  1212  (step S 403 ). If judged as out of the communication service area (“No” in S 403 ), namely if the second wireless system is not available for communication, area judging part  422  turns off the power to second baseband signal processing part  131  (step S 408 ), and then completes the communication area judging process. 
     Meanwhile, if judged as within the communication service area (“Yes” in S 403 ), namely if the second wireless system is available for communication, area judging part  422  checks the state of the power to second baseband signal processing part  131  (step S 404 ). Then, if the power to second baseband signal processing part  131  is on (“Yes” in S 404 ), part  422  completes the communication area judging process. If off (“No” in S 404 ), however, part  422  turns on the power to second baseband signal processing part  131  (step S 406 ) and then completes the communication area judging process. 
     Here, the communication area judging process does not need to be performed for the first wireless system first, but can be performed for the second one first. In addition, the process does not need to use threshold judgement for the peak among correlation operation results, but may use any means as long as it uses correlation operation results, such as the difference between the peak among correlation operation results and the noise level. 
     As described above, multimode wireless communication apparatus  400  according to the embodiment includes first baseband signal processing part  130  as the first signal processing part that demodulates the digital signal from first A/D part  112 , in accordance with synchronization timing supplied from first-wireless-system-use synchronization detecting part  1211  as the first synchronization detecting part; second baseband signal processing part  131  as a second signal processing part that demodulates the digital signal from second A/D part  113 , in accordance with synchronization timing supplied from second-wireless-system-use synchronization detecting part  1212  as the second synchronization detecting part; and area judging part  422 , where part  422  judges the possibility of communication by a wireless system using correlation operation results supplied from synchronization detecting part  121 . If area judging part  422  judges as wireless communication impossible, part  422  turns off the power to the first or second signal processing part that demodulates the digital signal in the wireless communication method that has been judged as wireless communication being impossible. In this way, only the baseband signal processing part supporting the wireless system communicatable is operated, and thus multimode wireless communication apparatus  400  according to the embodiment can further reduce the power consumption. 
     Fifth Exemplary Embodiment 
       FIG. 19  is a block diagram illustrating makeup of multimode wireless communication apparatus  500  according to the fifth embodiment of the present invention. Multimode wireless communication apparatus  500  in  FIG. 19  is different from multimode wireless communication apparatus  400  according to the fourth embodiment, shown in  FIG. 17  in that apparatus  500  includes baseband signal processing part  530  as a software signal processing part, instead of first baseband signal processing part  130  and second baseband signal processing part  131 , and further includes switch  523  and control part  520 . Another difference from the fourth embodiment is that judgement results from area judging part  442  are supplied to control part  520 . 
     Baseband signal processing part  530  implements a general-purpose signal process by hardware and a function specific to each communication method, by software. In the fifth embodiment, baseband signal processing part  530  can support IEEE 802.11a and W-CDMA, where control part  520  switches between the function of first baseband signal processing part  130  of multimode wireless communication apparatus  100  according to the first embodiment shown in  FIG. 1 , and that of second baseband signal processing part  131 . 
     Switch  523  switches the input of digital signals from first A/D part  112  and second A/D part  113 , and is controlled by control part  520 . More specifically, control part  520  sets switch  523  so that an output signal supplied from first A/D part  112  will be input to baseband signal processing part  530 , if baseband signal processing part  530  has the function of first baseband signal processing part  130 ; and part  520  switches so that an output signal supplied from second A/D part  113  will be input to baseband signal processing part  530 , if baseband signal processing part  530  has the function of second baseband signal processing part  131 . 
     Control part  520  controls switch  523  and baseband signal processing part  530  on the basis of the judgement result by area judging part  442 , and if the result indicates that communication is possible only by the first wireless system, part  520  directs baseband signal processing part  530  so that part  530  will support the first wireless system. 
     If the judgement result indicates that communication is possible only by the second wireless system, control part  520  directs baseband signal processing part  530  so that baseband signal processing part  530  will support the second wireless system. If the judgement result indicates that communication is possible or impossible by both wireless systems, control part  520  determines so that baseband signal processing part  530  will support the first or second wireless system, according to predetermined priority. 
     If communication is possible or impossible by both wireless systems, judgement can be made by comparing the results of correlation operation performed by first-wireless-system-use synchronization detecting part  1211  and that by second-wireless-system-use synchronization detecting part  1212 . Such methods include comparing the peak values between the respective results of correlation operation, and comparing the differences between the peaks among correlation operation results and the noise level. 
     If communication is impossible by both wireless systems, decision can be made on conditions such as larger cover area or higher reception sensitivity out of the first and second wireless systems. If communication is possible by both wireless systems, less expensive communication charge or lower power consumption can be such a condition. Alternatively, a user of the multimode wireless communication apparatus may select a wireless system. 
       FIG. 20  is a flowchart illustrating the operation of the communication area judging process of the multimode wireless communication apparatus according to the embodiment. The operation of multimode wireless communication apparatus  500  shown in  FIG. 19  is described using the flowchart of  FIG. 20 . 
     First, area judging part  442  judges whether or not the communication apparatus is within an area communicatable by the first wireless system on the basis of the result of correlation operation by synchronization detecting part  1211  (step S 501 ). 
     If judged as out of a communication service area (“No” in S 501 ), area judging part  442  judges whether or not the communication apparatus is within an area communicatable by the second wireless system on the basis of the result of correlation operation by synchronization detecting part  1212  (step S 505 ). If judged as out of the communication service area (“No” in S 505 ), the process proceeds to step S 503 . Meanwhile, if judged as within the communication service area (“Yes” in S 505 ), namely if only the second wireless system is available for communication, baseband signal processing part  530  begins to support the second wireless system (step S 506 ), and then completes the communication area judging process. 
     Meanwhile, in step S 501 , if judged as within the communication service area through the first wireless system (“Yes” in S 501 ), judgement is as well made whether or not the communication apparatus is within the area communicatable by the second wireless system on the basis of the result of correlation operation by synchronization detecting part  1212  (step S 502 ). If judged as within the communication service area (“Yes” in S 502 ), the process proceeds to step S 503 . Meanwhile, if judged as out of the communication service area (“No” in S 502 ), namely if only the first wireless system is within the communicatable area, baseband signal processing part  530  begins to support the first wireless system (step S 504 ), and then completes the communication area judging process. 
     The current state is that communication is possible or impossible by both the first and second wireless systems, and thus control part  520  determines if the first wireless system is to be supported, according to given priority (step S 503 ). If determined so (“Yes” in S 503 ), baseband signal processing part  530  begins to support the first wireless system (step S 504 ), and then completes the communication area judging process. Meanwhile, if determined otherwise (“No” in S 503 ), baseband signal processing part  530  begins to support the second wireless system (step S 506 ), and then completes the communication area judging process. 
     Here, the communication area judging process does not need to be performed for the first wireless system first, but can be performed for the second one first. 
     If the area determining process of the fifth embodiment is applied to multimode wireless communication apparatus  400  in  FIG. 17  of the fourth embodiment, the following control is possible. That is, in S 506 , the power to first baseband signal processing part  130  in  FIG. 17  is turned off instead of assigning baseband signal processing part  530  to support the second wireless system in  FIG. 19 ; and in S 504  as well, the power to second baseband signal processing part  131  is turned off instead of assigning baseband signal processing part  530  to support the first wireless system. 
     Synchronization detecting part  121  can detect synchronization timing for three or more wireless systems, and thus as a result that synchronization detecting part  121  performs correlation operation using a weight coefficient used for detecting synchronization timing for a wireless system other than the first or second wireless system, area judging part  442  can judge the communication service area for plural wireless systems. Making baseband signal processing part  530  support three or more wireless systems enables multimode wireless communication apparatus  500  according to the present invention to support three or more wireless systems. 
     As described above, multimode wireless communication apparatus  500  according to the embodiment includes baseband signal processing part  530  as a software signal processing part that switches operation including either one of a first signal process that demodulates the digital signal from first A/D part  112  in accordance with synchronization timing from first-wireless-system-used synchronization detecting part  1211  as the first synchronization detecting part; and a second signal process that demodulates the digital signal from second A/D part  113  in accordance with synchronization timing from second-wireless-system-use synchronization detecting part  1212  as the second synchronization detecting part, on a given condition. The software signal processing part is characterized in that it performs either one of the first and second signal processes corresponding to a wireless communication system that has been judged as wireless communication being possible by area judging part  442 . Other characteristics include that a signal process by the software signal processing part is determined to either one of the first and second signal processes by comparing the results of correlation operation by the first and second synchronization detecting parts. 
     Multimode wireless communication apparatus  100  according to the embodiment can thus share the delay part among plural wireless communication systems and does not have plural baseband signal processing parts  530 , thereby reducing the circuit scale and power consumption. 
     INDUSTRIAL APPLICABILITY 
     As described above, the present invention facilitates downsizing and reducing the power consumption of an apparatus, and thus is useful for a synchronization detecting circuit and a multimode wireless communication apparatus.