Abstract:
A case for a communication terminal and a communication terminal using the case are provided. The case includes a coupling unit configured to electrically couple the communication terminal and the case, and an extension device formed in the case and configured to extend a communication performance of the communication terminal when the communication terminal and the case are coupled together via the coupling unit.

Description:
[0001]    This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 10-2006-0131076 and 10-2006-0131085, filed in Republic of Korea on Dec. 20, 2006 the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    This document relates to a case for a communication terminal, and a communication terminal using the case. 
         [0004]    2. Related Art 
         [0005]    In a communication terminal, a case made of a material such as plastic is detachably provided. The case is fastened to the communication terminal to be used as a means for protecting a housing of the communication terminal from the outside. 
         [0006]    However, when the case is fastened to the communication terminal, due to a dielectric substance and other metal materials, etc. constituting the case, frequency characteristics of the communication terminal change. Thereby, a performance of an antenna provided in the communication terminal may be deteriorated. 
         [0007]    Further, as many functions are added to the communication terminal, it is difficult to extend a function of the communication terminal while decreasing a size of the communication terminal. 
       SUMMARY 
       [0008]    An aspect of this document is to provide a case for a communication terminal and a communication terminal using the case that can extend a communication performance of a communication terminal by coupling a case for the communication terminal comprising an extension device for extending the communication performance and the communication performance. 
         [0009]    Another aspect of this document is to provide a case for a communication terminal and a communication terminal using the case that can extend a performance of the communication terminal while decreasing a size of the communication terminal by forming an extension device for extending a communication performance of the communication terminal in the case for the communication terminal. 
         [0010]    In one general aspect, a case for a communication terminal comprises a coupling unit configured to electrically couple the communication terminal and the case, and an extension device formed in the case and configured to extend a communication performance of the communication terminal when the communication terminal and the case are coupled together via the coupling unit. 
         [0011]    The extension device may comprise an operating antenna having a specific frequency band and that is connected to a Radio Frequency (RF) module in the communication terminal when the communication terminal and the case are coupled together via the coupling unit. 
         [0012]    The extension device may comprise an operating power amplifier configured to amplify a transmission output of the communication terminal that is connected to a Radio Frequency (RF) module in the communication terminal when the communication terminal and the case are coupled together via the coupling unit. 
         [0013]    In another aspect, a communication terminal, comprises a communication module configured to wirelessly communicate with at least one other terminal, a case configured to cover at least a portion of the communication terminal, a coupling unit configured to electrically couple the communication terminal and the case, and an extension device formed in the case and configured to extend a communication performance of the communication terminal when the communication terminal and the case are coupled together via the coupling unit. 
         [0014]    The coupling unit may comprise a first connector formed in the case, and a second connector formed in the communication terminal configured to electrically connect to the first connector when the communication terminal and the case are coupled together. 
         [0015]    The extension device may comprise at least one operating antenna having a specific frequency band. 
         [0016]    In yet another aspect, a method of communicating on a mobile terminal, the method comprises coupling a case to the mobile terminal such that the case and the mobile terminal are electrically coupled together, and transmitting a signal from the mobile terminal that has been received or amplified by an extension communication device formed in the case. 
         [0017]    The extension communication device may comprise at least one operating antenna having a specific frequency band or a power amplifier. 
         [0018]    The method may further comprise providing a menu option allowing a user to select a class transmission power from among a plurality of class transmission powers, and amplifying a signal to be output via an internal antenna in the mobile terminal using the amplifier formed in the case to have the class transmission power selected by the user from the menu option. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The details of one or more implementations are set forth in the accompanying drawings and the description below. In the entire description of this document, like reference numerals represent corresponding parts throughout various figures. 
           [0020]      FIGS. 1A and 1B  are perspective views illustrating a case for a communication terminal and a communication terminal using the case in an implementation; 
           [0021]      FIG. 2  is a perspective view illustrating an example in which an extension device is an antenna in an implementation; 
           [0022]      FIG. 3  is a view illustrating a case in which the extension device is an antenna in  FIG. 2 ; 
           [0023]      FIG. 4  is a perspective view illustrating a second connector of a communication terminal connected to a first connector of the case in an implementation; 
           [0024]      FIG. 5  is a block diagram illustrating a configuration of a communication terminal in an implementation; 
           [0025]      FIG. 6  is a flowchart illustrating a method of using an antenna of a communication terminal in an implementation; 
           [0026]      FIG. 7  is a diagram illustrating an operation when a case and a communication terminal are coupled in an implementation; 
           [0027]      FIGS. 8A and 8B  are diagrams illustrating an example of switching a switch in order to check whether a case is fastened; 
           [0028]      FIG. 9  is a diagram illustrating an operation of a corresponding antenna when a specific additional function is selected in an implementation; 
           [0029]      FIG. 10  is a diagram illustrating an example in which fastening terminals are provided in a case and a communication terminal in another implementation; 
           [0030]      FIG. 11  is a cross-sectional view of a pogo pin in another implementation; 
           [0031]      FIGS. 12A and 12B  are views illustrating a first connector and a second connector in another implementation; 
           [0032]      FIG. 13  is a perspective view illustrating a communication terminal using a case for a communication terminal in another implementation; 
           [0033]      FIG. 14  is a view illustrating an example in which an extension device is a power amplifier in another implementation; 
           [0034]      FIG. 15  is a perspective view illustrating a first input/output unit and a first interface of a communication terminal to be fastened to a case in an implementation; 
           [0035]      FIG. 16  is a block diagram illustrating a configuration of a case for a communication terminal in an implementation; 
           [0036]      FIG. 17  is a block diagram illustrating a configuration of a communication terminal in an implementation; 
           [0037]      FIG. 18  is a table illustrating a class of transmission power of Bluetooth; 
           [0038]      FIG. 19  is a flowchart illustrating a method of amplifying power of a communication terminal in an implementation; 
           [0039]      FIG. 20  is a diagram illustrating a process of selecting a class in an implementation; and 
           [0040]      FIG. 21  is a block diagram illustrating an operation when a case and a communication terminal are coupled in an implementation. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Hereinafter, in an implementation of this document, a case for a communication terminal and a communication terminal using the case will be described in detail with reference to the accompanying drawings. 
         [0042]      FIGS. 1A and 1B  are perspective views illustrating a case for a communication terminal and a communication terminal using the case in an implementation. 
         [0043]    As shown in  FIGS. 1A and 1B , a case  20  is detachably coupled to the outside of a communication terminal  10 . In the case  20 , a case unit  22  for protecting a housing of the communication terminal  10  is made of a leather material. 
         [0044]    In the case unit  22 , a connector  24  and an extension device  26  are formed. When the communication terminal  10  is coupled to the connector  24 , the extension device  26  extends a communication performance of the communication terminal  10 . 
         [0045]    An Implementation (When the Extension Device is an Antenna) 
         [0046]      FIG. 2  is a perspective view illustrating an example in which an extension device is an antenna in an implementation.  FIG. 3  is a view illustrating a case in which the extension device is an antenna in  FIG. 2 . 
         [0047]    Referring in  FIGS. 2 and 3 , the extension device  26  may be an antenna. Accordingly, when the communication terminal  10  and the case  20  are coupled, the extension device  26  operates as an antenna having a specific frequency band. In this case, the extension device  26  operates as an external antenna  100  formed in the outside of the communication terminal  10 . 
         [0048]    The external antenna  100  comprises a first external antenna  102 , a second external antenna  104 , and a third external antenna  106 . 
         [0049]    Each of the external antennas  100  can be operated in several frequency bands. For example, the first external antenna  102  operates in a Bluetooth frequency band, the second external antenna  104  operates in a CDMA or GSM frequency band. Further, the third internal antenna  106  operates in a FM radio frequency. A pattern and a shape of the external antenna  100  can be designed according to a corresponding frequency band. 
         [0050]    Further, the external antenna  100  can be formed in the inside of the case  20  and is connected to a first connector  110 , which is the connector  24  protruded to the outside of the case  20 . 
         [0051]    In this case, the first connector  110  is formed in the quantity corresponding to that of the external antenna  100 . That is, when the external antenna  100  is formed in a first, second, and third external antennas ( 102 ,  104 ,  106 ), the first connector  110  has also three terminals. 
         [0052]    The first connector  110  contacts with the communication terminal  10  and has a protruded contact portion. Accordingly, when the first connector  110  is fastened to the communication terminal  10 , the first connector  110  is easily coupled to the communication terminal  10  due to an elastic force corresponding to a pressure in which the communication terminal  10  applies. 
         [0053]    The communication terminal  10  to be fastened to the first connector  110  is shown in  FIG. 4 . 
         [0054]      FIG. 4  is a perspective view illustrating a second connector of a communication terminal to be connected to a first connector of the case in an implementation. 
         [0055]    As shown in  FIG. 4 , the first connector  110  of the case  20  of  FIG. 3  is connected to the second connector  200  formed at a lower end of the communication terminal  10 . The second connector  200  is a conductive terminal and is formed in a position and the quantity corresponding to the first connector  110 . For example, when the first connector  110  is formed in three protruded portions, the second connector  200  is also formed in three terminals. 
         [0056]    Therefore, when the case  20  is fastened to communication terminal  10 , the first connector  110  and the second connector  200  come in contact and are coupled. 
         [0057]    An internal configuration of the communication terminal  10  to be fastened to the case  20  is shown in  FIG. 5 . 
         [0058]      FIG. 5  is a block diagram illustrating a configuration of a communication terminal in an implementation. 
         [0059]    Referring in  FIGS. 3 and 5 , the communication terminal  10  comprises a second connector  200 , an internal antenna  210 , an RF transceiver  220 , a switch  230 , and a controller  240 . 
         [0060]    When the case  20  is fastened to the communication terminal  10 , the second connector  200  contacts with the first connector  110 . 
         [0061]    The internal antenna  210  comprises a main antenna operating in a communication network of Code Division Multiple Access (CDMA) and Global System for Mobile Communication (GSM). Further, the internal antenna  210  comprises a sub-antenna corresponding to the external antenna  100  operating in Bluetooth and a FM radio frequency formed in the case  20 . 
         [0062]    For example, a first internal antenna  212  operates in a Bluetooth frequency band, or a second internal antenna  214  operates in a CDMA or GSM frequency band. Further, a third internal antenna  216  operates in a FM radio frequency. The internal antenna  210  may be formed in antennas of the quantity equal to or greater than that of the external antenna  100 . 
         [0063]    The RF transceiver  220  transmits, receives, and processes an RF signal corresponding to a frequency of the external antenna  100  and the internal antenna  210  by the control of the controller  240 . 
         [0064]    The switch  230  is provided between the second connector  200  and the RF transceiver  220  and connects the external antenna  100  or the internal antenna  210  to the RF transceiver  220 . 
         [0065]    The controller  240  comprises a Mobile Station Modem (MSM) and controls general input and output of the communication terminal  10 . Furthers when the first connector  110  and the second connector  200  come in contact, the controller  240  controls the switch  230  so that the external antenna  100  or the internal antenna  210  is connected to the RF transceiver  220 . 
         [0066]    An operation of a case for a communication terminal and a communication terminal using the case having the above described configuration is described as follows. 
         [0067]      FIG. 6  is a flowchart illustrating a method of using an antenna of a communication terminal in an implementation.  FIG. 7  is a diagram illustrating an operation when a case and a communication terminal are coupled in an implementation. 
         [0068]    As shown in  FIG. 6 , the controller  240  checks a RSSI of the external antenna  100  by switching the switch  230  in every predetermined time while operating in a CDMA communication network using the second internal antenna  214 . 
         [0069]    The controller  240  checks whether power is received from the first connector  110  through the second connector  200  by connecting the switch  230  to the second connector  200 , thereby knowing the RSSI of the external antenna  100 . 
         [0070]    in this case, when the case  20  is fastened to the communication terminal  10 , the first connector  110  and the second connector  200  are connected. Accordingly, the controller  240  checks the RSSI of the second external antenna  104 , thereby knowing that the case  20  is fastened to the communication terminal  10  (S 300 ). 
         [0071]    Thereafter, in order to check the RSSI of the second internal antenna  214  and the second external antenna  104 , the controller  240  switches the switch, as shown in  FIGS. 8A and 8B . 
         [0072]      FIGS. 8A and 8E  are diagrams illustrating an example of switching a switch in order to check whether a case is fastened. 
         [0073]    As shown in  FIG. 8A , the second switch  234  is connected to the second internal antenna  214 . In this state, the controller  240  connects the second switch  234  to the second connector  204  in every predetermined time, as shown in  FIG. 8B . The controller  240  switches the second switch  234 , thereby knowing that the case  20  is fastened to the communication terminal  10 . 
         [0074]    Thereafter, as shown in  FIGS. 8A and 8B , the controller  240  checks whether the RSSI of the second internal antenna  214  is greater than that of the second external antenna  104  by switching the second switch  234  (S 310 ). If the RSSI of the second internal antenna  214  is greater than that of the second external antenna  104 , the controller  240  connects the second switch  234  to the second internal antenna  214 . 
         [0075]    The second internal antenna  214  is connected to the second RF transceiver  224  and thus the second internal antenna  214  is used (S 320 ). 
         [0076]    If the RSSI of the second internal antenna  214  is not greater than that of the second external antenna  104 , the controller  240  connects the second switch  234  to the second connector  204 . Therefore, the second switch  234  is connected to the second external antenna  104  formed in the case  20 , whereby the second external antenna  104  is connected to the second RF transceiver  224  and thus the second external antenna  104  is used (S 330 ). 
         [0077]    In the implementation, as the controller  240  switches the second switch  234 , an antenna having a better RSSI is used, however this document is not limited thereto. That is, when it is checked that the case  20  is fastened to the communication terminal  10  by switching the second switch  234  while using the second internal antenna  214 , the controller  240  controls to use the second external antenna  104  formed in the case  20 . 
         [0078]    Further, an example of operating another antenna while using the second internal antenna  214  or the second external antenna  104 , which is a main antenna is described as follows. 
         [0079]      FIG. 9  is a diagram illustrating an operation of a corresponding antenna when selecting a specific additional function in an implementation. 
         [0080]    As shown in  FIG. 9 , the user executes “1. Bluetooth function” among additional functions provided by the communication terminal  10 . Accordingly, the controller  240  can operate one of the first internal antennas  212  and the first external antenna  102  operating in a Bluetooth frequency with the above-described principle. That is, by checking the RSSI of the first external antenna  102  by the above-described principle, the controller  240  checks whether the case  20  is fastened to the communication terminal  10 . 
         [0081]    If the case  20  is fastened to the communication terminal  10 , the controller  240  compares the RSSI of the first internal antenna  212  with that of the first external antenna  102  and executes an antenna having a better RSSI. 
         [0082]    In another example, as shown in  FIG. 9 , the user executes “2. FM radio function” among additional functions provided by the communication terminal  10 . Accordingly, the controller  240  checks whether the case  20  is fastened to the communication terminal  10  with the above-described principle. 
         [0083]    If the case  20  is fastened to the communication terminal  10 , the controller  240  executes an antenna having a better RSSI between the third internal antenna  216  and the third external antenna  106 . 
         [0084]    In the above-described implementation, by checking the RSSI of the external antenna  100  corresponding to the internal antenna  210 , it can be seen that the case  20  is fastened to the communication terminal  10 , however this document is not limited thereto. That is, the controller  240  can check whether the case  20  is fastened to the communication terminal  10  by switching one of switches  230  coupled to the second connector  200 . 
         [0085]    In this case, the controller  240  checks the RSSI by switching one of the switches  230  connected to the second connector  200 , thereby checking whether the case  20  and the communication terminal  10  are fastened. 
         [0086]    Further, when the case  20  and the communication terminal  10  are fastened, a fastening signal may be output to the controller  240 , and an example thereof is described as follows. 
         [0087]      FIG. 10  is a diagram illustrating an example in which fastening terminals are provided in a case and a communication terminal in another implementation. 
         [0088]    As shown in  FIG. 10 , a first fastening terminal  118  provided in one side of the first connector  110  of the case  20 . Further, in order to correspond to the first fastening terminal  118 , a second fastening terminal  208  is provided at one side of the second connector  200  of the communication terminal  10 . 
         [0089]    The first fastening terminal  118  and the second fastening terminal  208  are not connected to the respective external antenna  100  and internal antenna  210 . However, the second fastening terminal  208  is connected to the controller  240 . 
         [0090]    In such a state, when the communication terminal  10  and the case  20  are fastened, the first fastening terminal  118  formed in the first connector  110  and the second fastening terminal  208  formed in the second connector  200  come in contact. Accordingly, because the second fastening terminal  208  outputs a fastening signal to the controller  240 , the controller  20  can know that the case  240  is fastened to the communication terminal  10 . 
         [0091]    In the above-described implementation, it is described that a contact portion of the first connector  110  is protruded to contact with the second connector  200 . However, the first connector  110  may be formed in a pogo pin, and an example thereof is described as follows. 
         [0092]      FIG. 11  is a cross-sectional view of a pogo pin in another implementation. 
         [0093]    As shown in  FIG. 11 , a contact portion of the first connector  110  may use a pogo pin  350 . The pogo pin  350  comprises a pin  351  and a receptacle  358  into which the pin  351  is inserted and provided. In this case, a body  357  of the pin  351  of the pogo pin  350  is formed in a cylindrical shape, and in the receptacle  358 , one side thereof is opened and a sliding groove  353  is formed at the inside thereof, and a locking groove  354  depressed in a predetermined depth is formed following the sliding groove  353 . 
         [0094]    The body  357  has a locking jaw  355  locked to the locking groove  354  and has a probe  356  contacting with the second connector ( 200  of  FIG. 4 ) at a tip thereof and moves in a front and rear direction or a vertical direction along the sliding groove  353 . The body  357  contacts with a rear surface of the locking jaw  355  and moves in a front and rear direction or a vertical direction by an elastic force of a spring  352  inserted into and provided within the sliding groove  353 . 
         [0095]    The pogo pin  350  is formed in the first connector  110  and coupled to the second connector  200  of  FIG. 4 , and an example thereof is described as follows. 
         [0096]      FIGS. 12A and 12B  are views illustrating a first connector and a second connector in another implementation. 
         [0097]    As shown in  FIG. 12A , the first connector  110  may be formed in the pogo pin  350  of  FIG. 11 . Accordingly, in the second connector  200 , a predetermined hole  360  is formed with the quantity and in a position corresponding to the pogo pin  350 . 
         [0098]    Therefore, as shown in  FIG. 12B , when the communication terminal  10  and the case  20  are fastened, the first connector  110  of the pogo pin  350  formed in the case  20  is coupled to a hole  360  formed in the second connector  200  of the communication terminal  10 , whereby the above-described operation is performed. 
         [0099]    In addition to the pogo pin  350 , various fastening structures can be used. 
         [0100]    In the above-described implementation, three external and internal antennas ( 100 ,  210 ) are formed, and thus an example in which the first connector  110  and the second connector  200  have three contact portions is described. 
         [0101]    However, this document is not limited thereto, various quantities of antennas may be formed, and thus the quantity of the contact portion of the first connector  110  and the second connector  200  can be changed. For example, when the quantity of the external and internal antennas ( 100 ,  210 ) is four, the first connector  110  and the second connector  200  are formed in four contact portions. In this case, as shown in  FIG. 10 , the fastening portion  118  may be further formed. 
         [0102]    Further, in the above-described implementation, the case  20  is made of leather, however the case  20  is not limited thereto and may be made of several materials such as plastic. 
         [0103]    Further, the external antenna  100  formed in the case  20  may be formed on a surface as well as the inside of the case  20  and may be formed in a Flexible Printed Circuit Board (FPCB). 
         [0104]    Further, the external antenna  100  formed in the case  20  may be formed in several surfaces of the case  20 . 
         [0105]    Further, in the above-described implementation, when the first connector  110  and the second connector  200  come in contact, the external antenna  100  or the internal antenna  210  is selectively connected to RF transceiver  220 , however this document is not limited thereto. 
         [0106]    That is, in this document, when the communication terminal  10  and the case  20  are fastened, by extending both the external antenna  100  and the internal antenna  210 , the external antenna  100  may extend a length of the internal antenna  210 . 
         [0107]    Another Implementation (when the Extension Device is a Power Amplifier) 
         [0108]      FIG. 13  is a perspective view illustrating a communication terminal using a case for a communication terminal in another implementation.  FIG. 14  is a view illustrating an example in which an extension device is a power amplifier in another implementation. 
         [0109]    As shown in  FIGS. 13 and 14 , the extension device  26  formed in the case  20  for the communication terminal  10  may be a power amplifier  400 . Further, in one side of the case  20 , a second interface  410  and second input/output units ( 420 ,  425 ), which are connectors, and the power amplifier  400  are formed. 
         [0110]    The second interface  410  and the second input/output units ( 420 ,  425 ) contact with communication terminal  10  and a contact portion thereof is protruded. Accordingly, when the case  20  is fastened to the communication terminal  10 , the case  20  is easily coupled to the communication terminal  10  due to an elastic force corresponding to a pressure to which the communication terminal  10  applies. 
         [0111]    The communication terminal  10  fastened to the case  20  is described as follows. 
         [0112]      FIG. 15  is a perspective view illustrating a first input/output unit and a first interface of a communication terminal to be fastened to a case in an implementation. 
         [0113]    Referring to  FIGS. 14 and 15 , a first interface  500  and first input/output units ( 510 ,  515 ) of the communication terminal  10  are conductive terminals. The first interface  500  and the first input/output units ( 510 ,  515 ) are formed in a position and with the quantity corresponding to the second interface  410  and the second input/output units ( 420 ,  425 ) of  FIG. 14 . 
         [0114]    For example, if the first interface  500  is formed in three terminals, the second interface  410  is also formed in three protruded portions. Further, if the first input/output units ( 510 ,  515 ) are formed in two terminals, the second input/output units ( 420 ,  425 ) are also formed in two protruded portions. 
         [0115]    Therefore, when the case  20  is fastened to the communication terminal  10 , the first interface  500  and the second interface  410  come in contact with and are coupled to each other. Further, the first input/output units ( 510 ,  515 ) and the second input/output units ( 420 ,  425 ) come in contact with and are coupled to each other. 
         [0116]    A configuration of the case  20  is described as follows. 
         [0117]      FIG. 16  is a block diagram illustrating a configuration of the case for the communication terminal in an implementation. 
         [0118]    As shown in  FIG. 16 , the second interface  410 , the second input/output units ( 420 ,  425 ), and the power amplifier  400  are formed at one side of the case  20 . 
         [0119]    The second interface  410  receives a control signal for controlling the power amplifier  400  from the communication terminal  10 , inputs the signal to the power amplifier  400 , and outputs a fastening signal to the communication terminal  10  when the communication terminal  10  and the case  20  are fastened. 
         [0120]    The second input/output units ( 420 ,  425 ) comprise a second input unit  420  and a second output unit  425 . Therefore, a signal having the first transmission output is received from the communication terminal  10  through the second input unit  420 . Further, a signal having the second transmission output is output to the communication terminal  10  through the second output unit  425 . 
         [0121]    The power amplifier  400  amplifies a signal having the first transmission output that is input through the second input unit  420  to a signal having the second transmission output and outputs the amplified signal to the second output units  425 . 
         [0122]    A configuration of the communication terminal  10  fastened to the case  20  is shown in  FIG. 17 . 
         [0123]      FIG. 17  is a block diagram illustrating a configuration of a communication terminal in an implementation. 
         [0124]    As shown in  FIG. 17 , the communication terminal  10  fastened to the case  20  comprises a baseband modem  530 , a first interface  540 , a Bluetooth antenna  550 , a Bluetooth module  560 , a first duplexer  570 , a second duplexer  575 , a first output unit  580 , and a first input unit  585 . 
         [0125]    The baseband modem  530  is a modem unit, and processes a Bluetooth protocol of a physical hierarchy. Further, the baseband modem  530  outputs a control signal for controlling the power amplifier  400  of the case  20  of  FIG. 14 . 
         [0126]    The first interface  540  outputs a control signal generating in the baseband modem  530  to the case  20 . 
         [0127]    The Bluetooth antenna  550  receives an electric wave in a Bluetooth frequency band (having a width of 83.5 MHz) of 2400 MHz to 2483.5 MHZ introduced from the outside. In this case, the Bluetooth antenna  550  can receive a signal having first transmission output and output a signal having second transmission output. 
         [0128]    The Bluetooth module  560  comprises a circuit such as a series of chips for Bluetooth communication. Accordingly, the Bluetooth module  560  converts a Bluetooth high frequency signal of the first transmission output received from the Bluetooth antenna  550  to a digital signal and converts the digital signal to the Bluetooth high frequency signal. 
         [0129]    The first duplexer  570  and the second duplexer  575  are connected to the Bluetooth antenna  550  to perform a function of dividing a transmission and reception frequency of the Bluetooth antenna  550 , thereby protecting mixing of a signal. Further, the first duplexer  570  and the second duplexer  575  enable a signal having the first transmission output received through the Bluetooth antenna  550  to be input to the Bluetooth module  560 . 
         [0130]    The first output unit  580  outputs a signal having the first transmission output that is output from the Bluetooth module  560  to the power amplifier  400  of the case  20  of  FIG. 2 . 
         [0131]    The first input unit  585  receives a signal having a second transmission output in which a signal having the first transmission output is amplified by the power amplifier  400  of the case  20  and outputs the signal to the Bluetooth antenna  550 . 
         [0132]    When the communication terminal  10  provides a Bluetooth function, transmission power of Bluetooth is generally divided into three classes, and this is shown in  FIG. 6 . 
         [0133]      FIG. 18  is a table illustrating a class of transmission power of Bluetooth. 
         [0134]    As shown in  FIG. 18 , transmission power of Bluetooth of the communication terminal  10  is divided into class  1 , class  2 , and class  3 . 
         [0135]    Class  1  has transmission power of 100 mW and a transmission output range of 100 m, and class  2  has transmission power of 2.5 mW and a transmission output range of 20 m to 30 m. Further, class  3  has transmission power of 1 mW and a transmission output range of 10 m. The classes  1  and  2  can set power control as an option, in the class  1 , transmission power can be varied within a range of 1-100 mW and in the class  2 , transmission power can be varied within a range of 0.25 to 2.5 mW. 
         [0136]    Class  1  supports a function of ‘birdie-birdie’, ‘walkie-talkie’, ‘one phone’, ‘local area Internet’, etc., and classes  2  and  3  support a function of local area data transmission or wireless headset, etc. 
         [0137]    A method of amplifying power between classes of Bluetooth is shown in  FIG. 19 . 
         [0138]      FIG. 19  is a flowchart illustrating a method of amplifying power of a communication terminal in an implementation.  FIG. 20  is a diagram illustrating an example of selecting a class in an implementation.  FIG. 21  is a block diagram illustrating an operation when a case and a communication terminal are coupled in an implementation. 
         [0139]    As shown in  FIG. 20 , the controller  240  turns on a Bluetooth function by entering a Bluetooth menu (S 600 ). 
         [0140]    In this case, as described in  FIG. 18 , transmission power of Bluetooth is divided into three classes. When class  1  is selected (S 610 ), a signal having 2.5 mV, which is the first transmission power received in the Bluetooth antenna  550  is received in a Bluetooth module  560  through the second duplexer  575  and the first duplexer  570  (S 620 ). 
         [0141]    Thereafter, after being converted to a signal in which Bluetooth can use in the Bluetooth module  560 , the signal is output to the Bluetooth antenna  550  through the second duplexer  575  and the first duplexer  570 . 
         [0142]    The controller  240  checks whether class  2  is selected in a Bluetooth menu (S 630 ). 
         [0143]    If class  2  is selected in a Bluetooth menu, the baseband modem  530  checks whether the case  20  is fastened (S 640 ). 
         [0144]    If the case  20  is not fastened, the controller  240  controls to display a message for requiring fastening of the case  20  (S 650 ). 
         [0145]    If the case  20  is fastened, a signal having 2.5 mV, which is the first transmission power received in the Bluetooth antenna  550  can be amplified. As shown in  FIG. 21 , when the case  20  is fastened to the communication terminal  10 , the first interface  500  of the communication terminal  10  is connected and fastened to the second interface  410  of the case  20 . Further, the first input/output units ( 510 ,  515 ) of the communication terminal  10  are connected and fastened to the second input/output units ( 420 ,  425 ) of the case  20 . 
         [0146]    When the communication terminal  10  and the case  20  are fastened, a fastening signal is generated from the second interface  410  of the case  20  and output to the first interface  500 . 
         [0147]    This fastening signal is output to the baseband modem  530 , thereby notifying that the communication terminal  10  and the case  20  are fastened. 
         [0148]    When it is checked that the communication terminal  10  and the case  20  are fastened, the baseband modem  530  outputs a signal for turning on the power amplifier  400  of the case  20  to the power amplifier  400  through the first interface  500  and the second interface  410 . 
         [0149]    Accordingly, the power amplifier  400  is turned on. In this case, when the Bluetooth module  560  does not support Bluetooth class  1 , the baseband modem  530  outputs a control signal for adjusting a gain value of the power amplifier  400  to the power amplifier  400  through the first interface  500  and the second interface  410 . 
         [0150]    Thereafter, a signal having 2.5 mV, which is the first transmission power received in the Bluetooth antenna  550  is output through the first duplexer  570  and the first output unit  580  (S 660 ). In this case, a signal having the first transmission power is input to the power amplifier  400  through the second input unit  420  of the case  20  connected to the first output unit  580 . 
         [0151]    The signal is amplified to a signal having 100 m W, which is the second transmission power in the power amplifier  400  and is output to the first input unit  585  connected to the second output unit  425  (S 670 ). 
         [0152]    A signal having 100 m W, which is the amplified second transmission power is output to the Bluetooth antenna  550  via the second duplexer  575  and converts transmission power from class  2  to class  1  (S 680 ). 
         [0153]    In the communication terminal  10 , class  2  can be easily converted to class  1  by amplifying transmission power of Bluetooth. 
         [0154]    However, this document is not limited thereto and in the communication terminal  10 , class  3  may be converted to class  1  or  2 , when the baseband modem  530  sets a gain value of the power amplifier  400  and the power amplifier  400  amplifies received power to a corresponding gain value. 
         [0155]    Further, in the above-described implementations, only amplifying of transmission power of Bluetooth is described, however this document is not limited thereto. 
         [0156]    That is, this document may be applied to amplifying of a wireless signal received in the communication terminal  10  for receiving the wireless signal. Therefore, in this case, the respective elements can be changed according to a kind of received wireless signals. 
         [0157]    Further, in the above-described implementations, each of the first input/output units ( 480 ,  485 ) and the second input/output units ( 420 ,  425 ) has two terminals, however this document is not limited thereto. That is, each of the first input/output units ( 480 ,  485 ) and the second input/output units ( 420 ,  425 ) may have one terminal and may have the quantity more than one terminal according to the input/output signal. 
         [0158]    Further, the first interface  540  and the second interface  410  may have several terminals to correspond to a control signal. 
         [0159]    Further, the case  20  in which the power amplifier  400  is formed is made of materials such as plastic as well as leather and is detachably formed to protect a housing of the communication terminal  10 . 
         [0160]    The case  20  has a structure for covering all or some of the communication terminal  10  and adjusts a position of the second interface  410  and the second input/output units ( 420 ,  425 ) according to a shape thereof. 
         [0161]    As described above, this document has the following effect. 
         [0162]    First, by coupling a case for the communication terminal having an extension device for extending a communication performance to the communication terminal, a communication performance of the communication terminal can be extended. 
         [0163]    Second, by providing the extension device for extending a communication performance of the communication terminal in the case for the communication terminal, a performance of the communication terminal can be extended while decreasing a size thereof. 
         [0164]    Other features will be apparent from the description and drawings, and from the claims.