Abstract:
In a wireless communication device, a switching section ( 11 ) is arranged between a transmitting circuit ( 201 ) and/or a receiving circuit ( 202 ) of one communication system and a branching filter ( 353 ), for connecting the transmitting circuit ( 201 ) and/or the receiving circuit ( 202 ) of the communication system to an antenna ( 351 ) through the branching filter ( 353 ) or not through the branching filter ( 353 ). When the communication system having the switching section ( 11 ) is independently operated, the transmitting circuit ( 201 ) and/or the receiving circuit ( 202 ) of the communication system in operation is directly connected to the antenna ( 351 ), not through the branching filter ( 353 ). Thus, circuit insertion loss is reduced, receiving sensitivity is improved and consumption power is reduced.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Japanese Patent Application No. 2006-353127 filed on Dec. 27, 2006, the entire contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a wireless communication apparatus. 
       BACKGROUND ART 
       [0003]    As wireless communication systems for a cellular phone or the like, there presently are a plurality of systems corresponding to each standard. Cellular phone systems widely used in Japan are, for example, PDC (Personal Digital Cellular), CDMA (Code Division Multiple Access), PHS (Personal Handyphone System) and the like. In addition, WiMAX (Worldwide Interoperability for Microwave Access) is becoming popular as one of new systems being suggested in recent years for a wireless broad band that takes a crucial part in ubiquitous age. 
         [0004]    Although the wireless communication apparatus normally corresponds to one of standards, it is becoming popular to have a multiband or a multimode wireless communication apparatus because of popularization of the cellular phones accompanied by tightening of the frequency range allocated to each system and, for example, a dual band communication apparatus capable of accepting two different communication systems of PDC and W-CDMA (Wideband Code Division Multiple Access) is known (see Patent Documents 1 and 2, for example). Recently, there is being developed a wireless communication apparatus capable of hybrid performance such as hand-off between different frequency ranges or seamless hand-off between different systems in order to provide a stable and highly functional service. 
         [0005]    Shown in  FIG. 10  is a block diagram illustrating an example of a conventional wireless communication apparatus used for the CDMA system. The wireless communication apparatus  100 - 1  has CDMA system of 800 MHz band (for example, ARIB STD-T53: Association of Radio Industries and Businesses STANDARD-T53) and CDMA system of 2 GHz band (for example, ARIB STD-T64). Furthermore, the diversity scheme is adopted for data communication (for example, cdma2000 1×EV-DO: 1× Evolution Data Optimized) of both the CDMA system of 800 MHz band and the CDMA system of 2 GHz band for the purpose of either improvement in throughput or hybrid performance. 
         [0006]    As shown in  FIG. 10 , the CDMA system of 800 MHz band is provided with a transmitting circuit  101 , a receiving circuit  102 , a duplexer (DUP)  103  for separating transmitted and received signals of 800 MHz band, and a secondary receiving circuit  121 , while the CDMA system of 2 GHz band is provided with a transmitting circuit  111 , a receiving circuit  112 , a duplexer (DUP)  113  for separating transmitted and received signals of 2 GHz band, and a secondary receiving circuit  131 . 
         [0007]    As common units for both of the CDMA systems, the wireless communication apparatus  100 - 1  has a primary antenna (ANT)  151 , a first external connector  152  comprising a measuring RF (Radio Frequency) connector for instance, a diplexer (Dip)  153  for sharing the primary antenna  151  with 800 MHz band and 2GHz band, a secondary antenna (ANT)  161 , a first external connector  162  comprising a measuring RF connector, and a diplexer (Dip)  163  for sharing the secondary antenna  161  by the secondary receiving circuit  121  of 800 MHz band and the secondary receiving circuit  131  of 2 GHz band. 
         [0008]    The transmitting circuit  101 , the receiving circuit  102  and the secondary receiving circuit  121  of the CDMA system of 800 MHz band are connected to a baseband unit  500 . Likewise, the transmitting circuit  111 , the receiving circuit  112  and the secondary receiving circuit  131  of the CDMA system of 2 GHz band are connected to the baseband unit  500 . 
         [0009]    For 1×EV-DO communication with the CDMA system of 800 MHz band, for instance, by the wireless communication apparatus  100 - 1  shown in  FIG. 10 , the transmitted signal from the transmitting circuit  101  is radiated from the primary antenna  151  by way of the duplexer  103  and the diplexer  153 , while the received signal of 800 MHz band received by the primary antenna  151  is received by the receiving circuit  102  by way of the diplexer  153  and the duplexer  103 . Furthermore, the received signal of 800 MHz band received by the secondary antenna  161  is diversity received by the receiving circuit  121  by way of the diplexer  163 . 
         [0010]    Similarly, for 1×EV-DO communication with the CDMA system of 2 GHz band by the wireless communication apparatus  100 - 1 , the transmitted signal from the transmitting circuit  111  is radiated from the primary antenna  151  by way of the duplexer  113  and the diplexer  153 , while the received signal of 2 GHz band received by the primary antenna  151  is received by the receiving circuit  112  by way of the diplexer  153  and the duplexer  113 . Furthermore, the received signal of 2 GHz band received by the secondary antenna  161  is diversity received by the receiving circuit  131  by way of the diplexer  163 . 
         [0011]    The wireless communication apparatus  100 - 1  monitors a voice incoming call by regularly receiving notification information (paging) notifying the call from a base station in 1× communication. Therefore, during 1×EV-DO communication with either the CDMA system of 800 MHz band or the CDMA system of 2 GHz band, the wireless communication apparatus  100 - 1  regularly switches the system to 1× communication at the side of the primary antenna  151  to receive paging, or maintains 1×EV-DO communication at the side of primary antenna  151  to improve throughput and regularly switches the system to 1× communication at the side of the secondary antenna  161  to receive paging. 
         [0012]    Shown in  FIG. 11  is a block diagram illustrating another example of a conventional wireless communication apparatus used for the CDMA system. The wireless communication apparatus  100 - 2  is provided with an antenna switch  172  having four contact points a to d instead of the diplexer  153  in  FIG. 10 . The antenna switch  172  is controlled based on a control signal from the baseband unit  500  so that only the duplexer  103  is connected to the primary antenna  151  by way of the contact point a or to a secondary external connector (Ext)  171  serving as an external antenna connecting interface to which an external antenna can be connected, by way of the contact point b, or so that only the duplexer  113  is connected to the primary antenna  151  by way of the contact point c, or to the secondary external connector  171  by way of the contact point d. The primary antenna  151  and the secondary external connector  171  are thus shared by both the CDMA systems of 800 MHz band and of 2 GHz band. Since other constitutions and performances are the same as those of the wireless communication apparatus  100 - 1  in  FIG. 10 , the corresponding units are provided with the same reference symbols and the descriptions thereof will be omitted. 
         [0013]    Shown in  FIG. 12  is a block diagram illustrating an example of a conventional wireless communication apparatus used for the WiMAX system. The wireless communication apparatus  200  is for the WiMAX communication of 2.5 GHz band and provided with a transmitting circuit  201 , a receiving circuit  202 , a switch  253  with two contact points a and b, and an antenna (ANT)  251 . The transmitting circuit  201  and the receiving circuit  202  are connected to the baseband unit  500 . 
         [0014]    A complex communication system adopted by the WiMAX system is not Frequency Division Duplex (FDD) adopted for the CDMA system shown in  FIG. 10  and  FIG. 11  but Time Division Duplex (TDD). The wireless communication apparatus  200  thus controls the switch  253  based on the control signal from the baseband unit  500  in synchronization with transmitting and receiving so that the transmitted signal from the transmitting circuit  201  is radiated from the antenna  251  by way of the contact point a of the switch  253  in a transmitting frame (uplink) and the received signal received by the antenna  251  is received by the receiving circuit  202  by way of the contact point b of the switch  253  in a receiving frame (downlink). 
         [0015]    The wireless communication apparatus  200  shown in  FIG. 12  is further provided with an antenna (ANT)  261  and a secondary receiving circuit  211  to perform diversity receiving. The secondary receiving circuit  211  is connected to the baseband unit  500 . A first external connector  252  comprising a measuring RF connector is provided between the antenna  251  and the switch  253 , while a first external connector  262  comprising a measuring RF connector is also provided between the antenna  261  and the secondary receiving circuit  211 . 
         [0016]    A multimode wireless communication apparatus usable for both the CDMA system and the WiMAX system is conceivable as another wireless communication apparatus. When seamless hand-off between systems or the like is performed in such multimode wireless communication apparatus, it is necessary to run both systems simultaneously. It is preferable for each of the systems to share the same antenna in light of downsizing and the cost. 
         [0017]    A multimode wireless communication apparatus  300  shown in  FIG. 13  is suggested as an example of such multimode wireless communication apparatus. The multimode wireless communication apparatus  300  is a combination of the wireless communication apparatus  100 - 1  of the CDMA system shown in  FIG. 10  and the wireless communication apparatus  200  of the WiMAX system of 2.5 GHz band shown in  FIG. 12 . As shown in  FIG. 13 , each antenna terminal of the duplexer  103  of the CDMA system of 800 MHz band, of the duplexer  113  of the CDMA system of 2 GHz band and of the switch  253  of the WiMAX system of 2.5 GHz band is connected, by way of a triplexer (Tri)  353 , to an antenna (ANT)  351  that accepts three bands of 800 MHz band, 2 GHz band and 2.5 GHz. A first external connector  352  comprising a measuring RF connector is provided between the triplexer  353  and the antenna  351 . 
         [0018]    An antenna (ANT)  361  that accepts three bands is connected, by way of a triplexer (Tri)  363 , to secondary receiving circuits  121 ,  131  and  211  corresponding to each band. A first external connector  362  comprising a measuring RF connector is provided between the antenna  361  and the triplexer  363 . 
         [0019]    The transmitting circuit  101 , the receiving circuit  102  and the secondary receiving circuit  121  of the CDMA system of 800 MHz band are connected to the baseband unit  500 , and so are the transmitting circuit  111 , the receiving circuit  112  and the secondary receiving circuit  131  of the CDMA system of 2 GHz band and the transmitting circuit  201 , the receiving circuit  202  and the secondary receiving circuit  211  of the WiMAX system of 2.5 GHz band. 
         [0020]    A multimode wireless communication apparatus  300  shown in  FIG. 13  is provided with the triplexer  353  to share the antenna  351  among the CDMA system of 800 MHz band, the CDMA system of 2 GHz band and the WiMAX system of 2.5 GHz band and also provided with the triplexer  363  to share the antenna  361  among the secondary receiving circuits  121 ,  131  and  211  of each system. 
         [0021]      FIG. 14  shows another example of the multimode wireless apparatus. The multimode wireless communication apparatus  400  is a combination of the wireless communication apparatus  100 - 2  of the CDMA system shown in  FIG. 11  and the wireless communication apparatus  200  of the WiMAX system of 2.5 GHz band shown in  FIG. 12 . That is, in addition to the constitution shown in  FIG. 13 , in the multimode wireless communication apparatus  400 , the antenna terminal of the triplexer  353  is provided with an antenna switch  451  having two contact points a and b. The antenna switch  451  is controlled based on the control signal from the baseband unit  500  to selectively turn on the switch at the contact point a or b, thereby the antenna  351  and the second external connector  171  are shared among the CDMA system of 800 MHz band, the CDMA system of 2 GHz band and the WiMAX system of 2.5 GHz band. Other constitution is the same as that of the multimode wireless apparatus  300  in  FIG. 13 . 
       Patent Document 1: Japanese Patent Laid-Open No. 2003-188759 
     Patent Document 2: Japanese Patent Laid-Open No. 2004-023536 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0022]    However, the multimode wireless communication apparatus having constitution shown in  FIG. 13  and  FIG. 14  requires a demultiplexer such as a triplexer to share an antenna by each system. Thus, it has been a concern that insertion loss of a circuit is increased, resulting in degradation of receiving sensitivity and increase of power consumption. 
         [0023]    In consideration of such problems, therefore, an object of the present invention is to provide a wireless communication apparatus capable of reducing insertion loss of a circuit and thus improving receiving sensitivity and reducing power consumption. 
       Summary of the Invention 
       [0024]    In order to achieve the above object, a first aspect of the present invention is to provide a wireless communication apparatus comprising: 
         [0025]    an antenna; 
         [0026]    a demultiplexer provided in downstream of the antenna for demultiplexing signals in different frequency ranges of a plurality of communication systems; 
         [0027]    a transmitting circuit and/or a receiving circuit of the each communication system provided in downstream of the demultiplexer; 
         [0028]    a switching unit provided between the transmitting circuit and/or the receiving circuit of at least one communication system and the demultiplexer for switching a connection of the transmitting circuit and/or the receiving circuit of the communication system either to the antenna by way of the demultiplexer or to the antenna directly without the demultiplexer; and 
         [0029]    a control unit for controlling the switching unit so that, when a plurality of communication systems including a communication system having the switching unit are simultaneously operated, the transmitting circuit and/or the receiving circuit of each operating communication system is connected to the antenna by way of the demultiplexer and, when a communication system having the switching unit is solely operated, the transmitting circuit and/or the receiving circuit of the operating communication system is connected directly to the antenna without the demultiplexer. 
         [0030]    A second aspect of the present invention is to provide the wireless communication apparatus according to the first aspect, further comprising a matching circuit provided between the demultiplexer and the switching unit, wherein 
         [0031]    the switching unit is arranged so that the transmitting circuit and/or the receiving circuit of the corresponding communication system is connected to the antenna also by way of the matching circuit when connected to the antenna by way of the demultiplexer. 
         [0032]    Furthermore, a third aspect of the present invention for achieving the above object is to provide a wireless communication apparatus comprising: 
         [0033]    an antenna; 
         [0034]    a demultiplexer provided in downstream of the antenna for demultiplexing signals in different frequency ranges of a plurality of communication systems; 
         [0035]    a transmitting circuit and/or a receiving circuit of the each communication system provided in downstream of the demultiplexer; 
         [0036]    an external antenna connecting interface to which an external antenna can be connected; 
         [0037]    an external antenna switching unit provided between the external antenna connecting interface and the demultiplexer for switching a connection of the demultiplexer either to the antenna or to the external antenna connecting interface; 
         [0038]    a switching unit provided between the transmitting circuit and/or the receiving circuit of at least one communication system and the demultiplexer for switching the connection of the transmitting circuit and/or the receiving circuit of the communication system either to the external antenna switching unit by way of the demultiplexer or to the external antenna switching unit directly without the demultiplexer; and 
         [0039]    a control unit for controlling the switching unit so that, when a plurality of communication systems including a communication system having the switching unit are simultaneously operated, the transmitting circuit and/or the receiving circuit of each operating communication system is connected to the external antenna switching unit by way of the demultiplexer and, when a communication system having the switching unit is solely operated, the transmitting circuit and/or the receiving circuit of the operating communication system is connected directly to the external antenna switching unit without the demultiplexer. 
         [0040]    A fourth aspect of the present invention is to provide the wireless communication apparatus according to the third aspect, further comprising a matching circuit provided between the demultiplexer and the switching unit, wherein 
         [0041]    the switching unit is arranged so that the transmitting circuit and/or the receiving circuit of the corresponding communication system is connected to the external antenna switching unit also by way of the matching circuit when connected to the external antenna switching unit by way of the demultiplexer. 
       EFFECT OF THE INVENTION 
       [0042]    According to the present invention, there is provided, between a transmitting circuit and/or a receiving circuit of at least one communication system and a demultiplexer, a switching unit where the transmitting circuit and/or the receiving circuit of the communication system is connected to an antenna or an external antenna connecting interface either directly or by way of the demultiplexer, which makes it possible, when a communication system having the switching unit is solely operated, to connect the transmitting circuit and/or the receiving circuit of the running communication system directly to the antenna or the external antenna connecting interface without the demultiplexer along the path. Therefore, it becomes possible to reduce insertion loss of the circuit when a system is solely operated and, as a result, to improve receiving sensitivity and reduce power consumption. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0043]      FIG. 1  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the first embodiment of the present invention. 
           [0044]      FIG. 2  is a flowchart illustrating an example of operations of the multimode wireless communication apparatus of the first embodiment. 
           [0045]      FIG. 3  is a diagram illustration an example of characteristics of output power to current of a power amplifier in a transmitting circuit of WiMAX system shown in  FIG. 1 . 
           [0046]      FIG. 4  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the second embodiment of the present invention. 
           [0047]      FIG. 5  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the third embodiment of the present invention. 
           [0048]      FIG. 6  is a flowchart illustrating an example of operations of the multimode wireless communication apparatus of the third embodiment. 
           [0049]      FIG. 7  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the fourth embodiment of the present invention. 
           [0050]      FIG. 8  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the fifth embodiment of the present invention. 
           [0051]      FIG. 9  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the sixth embodiment of the present invention. 
           [0052]      FIG. 10  is a block diagram illustrating an example of a conventional wireless communication apparatus used for CDMA system. 
           [0053]      FIG. 11  is a block diagram illustrating another example of a conventional wireless communication apparatus used for the CDMA system. 
           [0054]      FIG. 12  is a block diagram illustrating an example of a conventional wireless communication apparatus used for the WiMAX system. 
           [0055]      FIG. 13  is a block diagram illustrating an example of a conventional multimode wireless communication apparatus usable for both the CDMA system and the WiMAX system. 
           [0056]      FIG. 14  is a block diagram illustrating another example of a conventional multimode wireless communication apparatus usable for both the CDMA system and the WiMAX system. 
       
    
    
     REFERENCE SYMBOLS 
       [0000]    
       
           10 ,  20 ,  30 ,  40 ,  50 ,  60  multimode wireless communication apparatus 
           11 ,  41 ,  61 ,  253  switch 
           12  matching circuit 
           31  diplexer 
           101  transmitting circuit (CDMA of 800 MHz) 
           102  receiving circuit (CDMA of 800 MHz) 
           103 ,  113  duplexer 
           111  transmitting circuit (CDMA of 2 GHz) 
           112  receiving circuit (CDMA of 2 GHz) 
           121  secondary receiving circuit (CDMA of 800 MHz) 
           131  secondary receiving circuit (CDMA of 2 GHz) 
           171  second external connector 
           201  transmitting circuit (WiMAX of 2.5 GHz) 
           202  receiving circuit (WiMAX of 2.5 GHz) 
           211  secondary receiving circuit (WiMAX of 2.5 GHz) 
           351 ,  361  antenna 
           352 ,  362  first external connector 
           353 ,  363  triplexer 
       
     
       DESCRIPTION OF EMBODIMENTS 
       [0075]    Embodiments of the present invention will be described with reference to the accompanying drawings. 
       Embodiment 1 
       [0076]    Shown in  FIG. 1  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the first embodiment of the present invention. Although the multimode wireless communication apparatus  10  has a similar constitution to that shown in  FIG. 13 , the switch  253  is replaced with a switch  11  having four contact points a to d serving as a switching unit. The switch  11  is controlled based on a control signal from a baseband unit  500  serving as a control unit to selectively connect a transmitting circuit  201  or a receiving circuit  202  of WiMAX system of 2.5 GHz band to a triplexer  353  by way of the contact point a or c. Thereby, such circuit is connected to an antenna  351  by way of the triplexer  353  or by way of the contact point b or d without the triplexer  353 . 
         [0077]    A matching circuit (M)  12  is inserted between the switch  11  and the triplexer  353  to prevent, when the transmitting circuit  201  or the receiving circuit  202  of the WiMAX system of 2.5 GHz band is connected to the side of the antenna terminal of the triplexer  353  and an terminal at the demultiplexing side of the triplexer  353  is opened, influence on the impedance at the side of an antenna terminal. Other constitutions are the same as those in  FIG. 13  and the corresponding units are thus provided with the same reference symbols and descriptions thereof will be omitted. 
         [0078]    Shown in  FIG. 2  is a flowchart illustrating an example of operations of the multimode wireless communication apparatus  10  of the present embodiment. When the WiMAX system is selected (S 1 ), the multimode wireless communication apparatus  10  of the present embodiment judges whether or not the WiMAX system is solely operated, that is, whether or not the WiMAX system of 2.5 GHz band is operated simultaneously with the CDMA systems of 800 MHz band or of 2 GHz band (S 2 ). 
         [0079]    When it is judged that the WiMAX system is solely operated, the switch  11  is turned on at the contact point d (S 11 - d :ON) and turned off at the other contact points a to c (S 11 - a :OFF, S 11 - b :OFF, S 11 - c :OFF) (S 4 ) for receiving, while the switch  11  is turned on at the contact point b (S 11 - b :ON) and turned off at the other contact points a, c, and d (S 11 - a :OFF, S 11 - c :OFF, S 11 - d :OFF) (S 5 ) for transmitting, in synchronization with transmitting and receiving. Therefore, the transmitting circuit  201  or the receiving circuit  202  is connected directly to the antenna  351  without the triplexer  353  when the WiMAX system is solely operated. 
         [0080]    On the other hand, when it is judged at S 2  that the WiMAX system and the CDMA system are simultaneously operated, that is, when hand-off between the systems or the like is performed, in synchronization with transmitting and receiving in the WiMAX system (S 6 ), the switch  11  is turned on at the contact point c (S 11 - c :ON) and turned off at the other contact points a, b and d (S 11 - a :OFF, S 11 - b :OFF, S 11 - d :OFF) (S 7 ) for receiving, while the switch  11  is turned on at the contact point a (S 11 - a :ON) and turned off at the other contact points b to d (S 11 - b :OFF, S 11 - c :OFF, S 11 - d :OFF) (S 8 ) for transmitting. Therefore, the transmitting circuit  201  or the receiving circuit  202  of the WiMAX system is connected to the antenna  351  by way of the triplexer  353  when both of the WiMAX system and the CDMA system are simultaneously operated. 
         [0081]    As stated above, in the multimode wireless communication apparatus  10  of the present embodiment usable for both of the CDMA system and the WiMAX system, the transmitting circuit  201  or the receiving circuit  202  is connected to the antenna  351  without the triplexer  353  in synchronization with transmitting and receiving when the WiMAX system is solely operated. Therefore, it is possible to reduce insertion loss of the circuit and, as a result, to improve receiving sensitivity. Furthermore, the output power of a power amplifier on the transmitting circuit  201  can be reduced during transmitting, which can reduce power consumption. For example, when the power amplifier on the transmitting circuit  201  has a characteristic of output power (Pout[dBm]) to current (Icc[mA]) as shown in  FIG. 3 , about 50 mA of the current consumption can be reduced by lowering the output power by 1 dB. 
       Embodiment 2 
       [0082]    Shown in  FIG. 4  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the second embodiment of the present invention. Although the multimode wireless communication apparatus  20  has a similar constitution to that shown in  FIG. 1 , the transmitting circuit  201 , the receiving circuit  202 , the switch  11  and the matching circuit  12  of the WiMAX system are connected at the side of an antenna  361  while a secondary receiving circuit  211  of the WiMAX system is connected to the triplexer  353  at the side of the antenna  351 , and the switch  11  is controlled in the same manner as in the first embodiment. Other constitutions and performances are the same as those of the first embodiment. 
         [0083]    According to the multimode wireless communication apparatus  20  of the present embodiment, the transmitting circuit  201  or the receiving circuit  202  is connected to the antenna  361  without the triplexer  363  in synchronization with transmitting and receiving when the WiMAX system is solely operated. Therefore, it is possible, similarly to the case of the first embodiment, to reduce insertion loss of the circuit and, as a result, to improve receiving sensitivity and reduce power consumption. 
       Embodiment 3 
       [0084]    Shown in  FIG. 5  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the third embodiment of the present invention. Although the multimode wireless communication apparatus  30  has a similar constitution to that shown in  FIG. 4 , the matching circuit  12  is removed and the switch  11  and the triplexer  363  are replaced with a switch  253  and a diplexer  31  respectively. A secondary receiving circuit  121  of the CDMA system of 800 MHz band and a secondary receiving circuit  131  of the CDMA system of 2 GHz band are connected to the antenna  361  by way of the diplexer  31 , while the transmitting circuit  201  and the receiving circuit  202  of the WiMAX system are connected to an antenna terminal of the diplexer  31  by way of the switch  253 . 
         [0085]    More specifically, in the present embodiment, the transmitting circuit  201  and the receiving circuit  202  of the WiMAX system are connected to the antenna  361  without the diplexer  31  not only when the WiMAX system is solely operated but also when the WiMAX system and the CDMA system are simultaneously operated to perform hand-off therebetween or the like. It is thus prohibited to receive with the secondary receiving circuit of the CDMA system, namely diversity receiving when the WiMAX system and the CDMA system are simultaneously operated. 
         [0086]    Shown in  FIG. 6  is a flowchart illustrating an example of operations of the multimode wireless communication apparatus  30  of the present embodiment. When the WiMAX system is selected (S 11 ), the multimode wireless communication apparatus  30  of the present embodiment judges whether or not the WiMAX system is solely operated, that is, whether or not the WiMAX system is operated simultaneously with the CDMA systems of 800 MHz band or of 2 GHz band (S 12 ). 
         [0087]    When it is judged that the WiMAX system is solely operated, then whether or not to perform diversity receiving is judged (S 13 ). When diversity receiving is performed, diversity is set so as to receive with a secondary receiving circuit  211  of the WiMAX system (S 14 ), while diversity is prohibited so as not to receive with the secondary receiving circuit  211  of the WiMAX system when diversity receiving is not performed (S 15 ). 
         [0088]    On the other hand, when it is judged at S 12  that the WiMAX system and the CDMA system are simultaneously operated, namely when hand-off between the systems or the like is performed, diversity receiving is prohibited so as not to receive with the secondary receiving circuit  121  and with the secondary receiving circuit  131  of the CDMA system at S 15 . 
         [0089]    According to the multimode wireless communication apparatus  30  of the present embodiment, the transmitting circuit  201  or the receiving circuit  202  of the WiMAX system is selectively connected to the antenna  361  without the diplexer  31  not only when the WiMAX system is solely operated but also when the WiMAX system and the CDMA system are simultaneously operated. Thus, it is always possible to improve the receiving sensitivity and to reduce power consumption in the WiMAX system. 
       Embodiment 4 
       [0090]    Shown in  FIG. 7  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the fourth embodiment of the present invention. Although a multimode wireless communication apparatus  40  has a similar constitution to that shown in  FIG. 14 , the switch  451  is replaced with a switch  41  having six contact points a to f serving as an external antenna switching unit. The switch  41  is controlled based on the control signal from the baseband unit  500  so that, when the WiMAX system is solely operated, the transmitting circuit  201  or the receiving circuit  202  is connected to the antenna  351  or a secondary external connector  171  to which an external antenna can be connected, by way of the switch  41  without the switch  253  and the triplexer  353 . 
         [0091]    More specifically, when the WiMAX system is solely operated, the switch  253  is turned off at both of the contact points a and b, while the switch  41  is turned on and off at only the contact points e and c by control in synchronization with transmitting and receiving and turned off at the other contact points a, b and d so as to selectively connect the transmitting circuit  201  or the receiving circuit  202  to the antenna  351 . Alternatively, the switch  41  is turned on and off at only the contact points f and d by control in synchronization with transmitting and receiving and turned off at the other contact points a, b, c and e so as to selectively connect the transmitting circuit  201  or the receiving circuit  202  to the second external connector  171 . Therefore, in the present embodiment, the switch  253  constitutes a switching unit where the transmitting circuit  201  and the receiving circuit  202  are connected to the switch  41  serving as an external antenna switching unit by way of the triplexer  353  or directly without the triplexer  353 . 
         [0092]    Similarly to the case of the first embodiment, the matching circuit  12  is provided between the triplexer  353  and the switch  253  to prevent, when the switch  253  are turned off at both of the contact points a and b and the terminal at the demultiplexing side for 2.5 GHz band of the triplexer  353  is opened, influence on the impedance at the side of the antenna terminal. 
         [0093]    When the WiMAX system and the CDMA system are simultaneously operated, the switch  253  are turned on and off at the contact points a and b by control in synchronization with transmitting and receiving of the WiMAX system, while the switch  41  are turned off at the contact points c to f and turned on at either one of the contact points a and b, so as to share the antenna  351  or the second external connector  171 , by way of the triplexer  353 , among the CDMA system of 800 MHz band, the CDMA system of 2 GHz band and the WiMAX system of 2.5 GHz band. Since other constitutions are the same as those shown in  FIG. 14 , the corresponding units are provided with the same reference symbols and the descriptions thereof will be omitted. 
         [0094]    According to the multimode wireless communication apparatus  40  of the present embodiment, similarly to the case of the first embodiment, when the WiMAX system is solely operated, the transmitting circuit  201  or the receiving circuit  202  is directly connected, in synchronization with transmitting and receiving, to the switch  41  that switches the connection either to the antenna  351  or to the second external connector  171 , without the triplexer  353 . It is thus possible to reduce insertion loss of the circuit and, as a result, to improve receiving sensitivity and to reduce power consumption, as output power of the power amplifier on the transmitting circuit  201  can be reduced during transmitting. 
       Embodiment 5 
       [0095]    Shown in  FIG. 8  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the fifth embodiment of the present invention. Although the multimode wireless communication apparatus  50  has the similar constitution as that of the second embodiment shown in  FIG. 4 , the first external connector  352  at the side of the antenna  351  is replaced with the second external connector  171  and a switch  451  having two contact points a and b. The switch  451  is controlled based on the control signal from the baseband unit  500  and turned on at either one of the contact points a or b so as to connect the antenna terminal of the triplexer  353  to the antenna  351  or the second external connector  171 . Other constitutions and performances are the same as those of the second embodiment. 
         [0096]    In the present embodiment also, it is thus possible to obtain the similar effect as that of the second embodiment. 
       Embodiment 6 
       [0097]    Shown in  FIG. 9  is a block diagram illustrating a constitution of a main section of a multimode wireless communication apparatus of the sixth embodiment of the present invention. Although the multimode wireless communication apparatus  60  has a similar constitution as that of the fifth embodiment shown in  FIG. 8 , the switch  451  and the triplexer  353  at the side of the antenna  351  are replaced with the switch  41  having six contact points a to f. The switch  41  is controlled based on the control signal from the baseband unit  500  to share the antenna  351  and the second external connector  171  among the CDMA system of 800 MHz band, the CDMA system of 2 GHz band and the WiMAX system of 2.5 GHz band. 
         [0098]    More specifically, for the transmitting circuit  101  and the receiving circuit  102  of the CDMA system of 800 MHz band, of the switch  41  is turned on at either one of the contact points a and b so as to connect the antenna terminal of the duplexer  103  to the antenna  351  or the second external connector  171 , for the transmitting circuit  111  and the receiving circuit  112  of the CDMA system of 2 GHz band, the switch  41  is turned on at either one of the contact points c and d so as to connect the antenna terminal of the duplexer  113  to the antenna  351  or the second external connector  171 , and for the secondary receiving circuit  211  of the WiMAX system of 2.5 GHz band, the switch  41  is turned on at either one of the contact points e and f so as to connect an input terminal of the secondary receiving circuit  211  to the antenna  351  or the second external connector  171 . 
         [0099]    In addition, in the fifth embodiment shown in  FIG. 8 , the switch  11 , the matching circuit  12  and the triplexer  363  at the side of the antenna  361  are replaced with a switch  61  having four contact points a to d. The switch  61  is controlled based on the control signal from the baseband unit  500  to share a first external connector  362  and an antenna  361  among the CDMA system of 800 MHz band, the CDMA system of 2 GHz band, and the WiMAX system of 2.5 GHz band. 
         [0100]    More specifically, the secondary receiving circuit  121  of the CDMA system of 800 MHz band, the secondary receiving circuit  131  of the CDMA system of 2 GHz band, the transmitting circuit  201  of the WiMAX system of 2.5 GHz band, and the receiving circuit  202  of the WiMAX system of 2.5 GHz band are connectable to the first external connector  362  and the antenna  361  by way of the contact point a, b, c or d of the switch  61  respectively. On or off at the contact points a to d is controlled based on the control signal from the baseband unit  500 . 
         [0101]    As stated above, since the transmitting circuit  201  and the receiving circuit  202  of the WiMAX system are connected to the antenna  361  without the triplexer  363  not only when the WiMAX system is solely operated but also when the WiMAX system and the CDMA system are simultaneously operated, receiving with the secondary receiving circuit of the CDMA system, namely diversity receiving, is prohibited when WiMAX system and the CDMA system are simultaneously operated, in the same manner as in the third embodiment. 
         [0102]    The multimode wireless communication apparatus  60  of the present embodiment can reduce insertion loss of the circuit of each system because of omission of the triplexer  353  at the side of the antenna  351  and the triplexer  363  at the side of the antenna  361 . It is thus possible to improve receiving sensitivity and to reduce power consumption in each system when a plurality of systems are simultaneously operated, and also to improve receiving performance by diversity receiving when each system is solely operated. 
         [0103]    It is noted that the present invention is not limited to the above embodiments, and many variations and modifications can be made. For example, although the transmitting circuit  201  and the receiving circuit  202  of the WiMAX system of 2.5 GHz band are selectively connected to the side of the antenna terminal of the triplexer  353  by means of the switch  11  serving as the switching unit in the first embodiment, it is also possible to selectively connect the duplexer  103  of the CDMA system of 800 MHz band and the duplexer  113  of the CDMA system of 2 GHz band to the side of the antenna terminal of the triplexer  353  so as to connect a circuit to the antenna  351  directly without the triplexer  353  when the system is solely operated. Likewise, in the second to the fifth embodiments also, the duplexer  103  of the CDMA system of 800 MHz band or the duplexer  113  of the CDMA system of 2 GHz band can be selectively connected to the side of the antenna terminal of the triplexer  353  so as to connect a circuit directly to the side of the antenna terminal of the triplexer  353  without the triplexer  353  when the system is solely operated. Furthermore, it is also possible to connect secondary receiving circuit directly to the antenna or the second external connector by the switching unit without the demultiplexer such as the triplexer when the system is solely operated and diversity receiving of the system is performed. 
         [0104]    It is noted that, although the multimode wireless communication apparatus of the above embodiments are for the CDMA system and the WiMAX system, the present invention is also applicable to a multimode wireless communication apparatus usable for arbitrary combination of a plural wireless communication systems including wireless LAN (Local Area Network) represented by IEEE (Institute of Electrical and Electronic Engineers) 802.11b, wireless WAN (Wide Area Network), for which IEEE802.20 is being standardized, and the like.