Abstract:
Disclosed is a multi-band antenna unit of a mobile terminal that includes an antenna, switch, sensor, first matching circuit, second matching circuit, diplexer, first signal processing unit, and second signal processing unit. The antenna is movably installed between first and second contacts, and transmits and receives first and second signals of different frequency bands. The switch connects the first contact to the first matching circuit or the second contact through the second matching circuit. The sensor detects an antenna position, and allowing selective connection of first or second matching circuits. Transmission and reception of multiple signals of various frequency bands is enabled using a single antenna unit, reducing the number of components, cost, and size of a mobile terminal. Additionally, performance of an antenna is improved by connecting to a proper matching circuit according to the position of the antenna.

Description:
PRIORITY 
     This application claims priority to an application entitled “MULTI-BAND ANTENNA UNIT OF MOBILE TERMINAL” filed in the Korean Intellectual Property Office on Oct. 20, 2006, and assigned Serial No. 2006-0102346, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna unit of a mobile terminal, and, more particularly, to a multi-band antenna unit of a mobile terminal. 
     2. Description of the Prior Art 
     A mobile terminal is an electronic device enabling free wireless and short-range network communication with little restriction of time and place. The mobile terminal must have an antenna unit for effective communication. 
     Recently developed mobile terminals have a Bluetooth function, Digital Multimedia Broadcasting (DMB) function, and Radio Frequency IDentification (RFID) function in addition to their basic mobile communication function of telephone conversation. 
     Mobile terminals capable of receiving Terrestrial Digital Multimedia Broadcasting (T-DMB) service require a long antenna, because a T-DMB system uses a signal of a low frequency band (200 MHz). In this case, a retractable antenna is used for better portability of the mobile terminal. Mobile terminals capable of receiving Satellite Digital Multimedia Broadcasting (S-DMB) service utilize a diversity antenna unit. The diversity antenna unit includes an antenna integrated in the mobile terminal and a detachable external antenna for use in a weak radio field. 
     The RFID system is a non-contact identification system that processes information about a commodity (or product) and its surroundings via a radio frequency wave and a small chip that is attached to the commodity. The RFID system includes an RFID tag for storing data, a reader for retrieving data from the RFID tag, and an antenna for data transmission between the RFID tag and the reader. In the RFID system, a read range becomes a very importance factor, and a long antenna must be used for a longer read range. 
     A conventional mobile terminal must be equipped with several antennas for execution of mobile communication, DMB reception, and RFID functions corresponding to individual frequency bands. Therefore, the conventional mobile terminal has a disadvantage of increased size and weight. 
     In addition to the DMB and RFID functions, various functions, such as wireless Internet communication and GPS communication, are added to the mobile terminal, and accordingly the frequency band of each function becomes narrower and the number of frequency bands used by a mobile terminal is increasing. 
     To solve the above problems, several antennas have been developed to cover various frequency bands with a single antenna. However, development of an antenna circuit enabling effective transmission of signals in various frequency bands has not yet been successful. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above problems, and an object of the present invention is to provide a circuit of an antenna unit enabling effective transmission and reception of signals having a plurality of frequency bands with a single antenna, when executing mobile communication, DMB reception, and RFID functions. 
     Another object of the present invention is to improve performance of a mobile terminal antenna by using a proper antenna circuit. 
     Yet another object of the present invention is to reduce costs and size of a mobile terminal by reducing the number of components required for an antenna circuit. 
     In order to achieve the above objects, a multi-band antenna unit of a mobile terminal according to the present invention includes an antenna, switch, diplexer, first signal processing unit, and second signal processing unit. The antenna is movably installed between a first contact and a second contact, and transmits and receives a first signal and a second signal having different frequency bands from each other. The switch is selectively connected to the first contact through a first path or to the second contact through a second path. The diplexer is connected to the switch and separates the first signal and the second signal. The first and second signal processing units are connected to the diplexer. 
     The multi-band antenna unit preferably further includes a first matching circuit and a second matching circuit in the first path and in the second path, respectively. 
     The multi-band antenna unit further preferably includes a sensor connected to the first contact for detecting the position of the antenna and controlling the switch. 
     In the multi-band antenna unit, the first signal and the second signal may be an RFID signal and a T-DMB signal, respectively. 
     The multi-band antenna unit may further include an auxiliary antenna connected to the second signal processing unit, wherein the first signal and the second signal are an RFID signal and a T-DMB signal, respectively. 
     A multi-band antenna unit of a mobile terminal according to another embodiment of the present invention includes a first antenna, first branch, second branch, duplexer, first signal processing unit, diplexer, second signal processing unit, and third signal processing. The first antenna is movably installed between a first contact and a second contact, and transmits and receives a first signal, second signal, and third signal having different frequency bands from each other. The first branch is connected to the first contact, and the second branch is connected to the second contact and the first branch. The duplexer is connected to the first branch, and the first signal processing unit is connected to the duplexer. The diplexer is connected to the second branch and separates the second signal and the third signal. The second and third signal processing units are connected to the diplexer. 
     The multi-band antenna unit preferably further includes a switch and a second antenna. The switch is disposed between the first branch and the duplexer, and selectively connects to the first branch or to the second antenna. The second antenna is connected to the switch, and transmits and receives the first signal. 
     The multi-band antenna unit further preferably includes a sensor connected to the first contact, for detecting the position of the first antenna and controlling the switch. 
     The multi-band antenna unit yet further preferably includes a band reject filter disposed between the second branch and the diplexer. 
     In the multi-band antenna unit, the first signal, second signal, and third signal may be a mobile communication signal, RFID signal, and DMB signal, respectively. 
     A multi-band antenna unit of a mobile terminal according to another embodiment of the present invention includes a first antenna, first switch, branch, second antenna, second switch, first signal processing unit, band reject filter, diplexer, duplexer, second signal processing unit, and third signal processing unit. The first antenna is movably installed between a first contact and a second contact, and transmits and receives a first signal, second signal, and third signal having different frequency bands from each other. The first switch is selectively connected to the first contact or to the second contact. The branch is connected to the first switch and the band reject filter. The second antenna transmits and receives the first signal. The second switch is selectively connected to the branch or to the second antenna. The duplexer is connected to the second switch and the first signal processing unit. The band reject filter is connected to the branch. The diplexer is connected to the band reject filter, and separates the second signal and the third signal. The second and third signal processing units are connected to the diplexer. 
     The multi-band antenna unit further preferably includes a first matching circuit disposed between the first contact and the first switch, and a second matching circuit disposed between the second contact and the first switch. 
     The multi-band antenna unit preferably further includes a sensor connected to the first contact, first switch, and second switch. The sensor detects the position of the first antenna, and controls the first switch and the second switch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram showing a configuration of an antenna unit of a mobile terminal according to an embodiment of the present invention; 
         FIG. 2  is a block diagram showing a configuration of an antenna unit of a mobile terminal according to another embodiment of the present invention; 
         FIG. 3  is a block diagram showing a configuration of an antenna unit of a mobile terminal according to another embodiment of the present invention; and 
         FIG. 4  is a block diagram showing a configuration of an antenna unit of a mobile terminal according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The same reference numbers are used throughout the drawings to refer to the same or like parts. Detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring the subject matter of the present invention. 
       FIG. 1  is a block diagram showing a configuration of an antenna unit  100  of a mobile terminal according to the present invention. Referring to  FIG. 1 , the antenna unit  100  of the mobile terminal includes an antenna  110 , switch  120 , diplexer  130 , first signal processing unit  140 , second signal processing unit  150 , and sensor  160 . 
     The antenna  110  may transmit and receive a first signal and a second signal having different frequency bands from each other. The first signal is an RFID signal having a frequency band of 900 MHz, and the second signal is a T-DMB signal having a frequency band of 200 MHz. When the mobile terminal is located in an area providing a strong radio field, the antenna  110  may be used in a state of being inserted within the mobile terminal, and thereby appearance of the mobile terminal is improved. However, when the mobile terminal is located in an area providing a weak radio field, the antenna may be used in a state of being extended outside of the mobile terminal, and thereby performance of the antenna is improved. When the antenna  110  is extended outside of the mobile terminal, the antenna is connected to a first contact  111 . When the antenna is inserted into the mobile terminal, the antenna is connected to a second contact  112 . 
     The first contact  111  is connected to the switch  120  through a first path. The second contact  112  is connected to the switch  120  through a second path. The switch  120  selects one of the first path and the second path. The first path and the second path include a first matching circuit  121  and a second matching circuit  122 , respectively. The matching circuits  121  and  122  are selected to provide optimum impedance corresponding to the first path and the second path, respectively. Performance of the circuit may be improved by selecting a proper matching circuit. 
     The antenna unit  100  includes a sensor  160  connected between the first contact  111  and the switch  120 . The sensor  160  detects the position of the antenna  110  by identifying whether the antenna  110  is connected to the first contact  111 , and controls the switch  120  according to the position of the antenna  110 . When the antenna  110  is located at the first contact  111 , the switch  120  connects the diplexer  130  to the first path. When the antenna  110  is located at the second contact  112 , the switch  120  connects the diplexer  130  to the second path. 
     The switch  120  is connected to the diplexer  130 . The diplexer  130  includes a low pass filter and a high pass filter, and separates an RFID signal and a T-DMB signal according to their frequency bands. The separated RFID signal is transmitted to the first signal processing unit  140  and the separated T-DMB signal is transmitted to the second signal processing unit  150 . 
     The first and second signal processing units  140  and  150  process the received signal to be used by the mobile terminal. For example, an RFID signal processing unit includes a directional coupler, power amplifier, and RF identification processing unit, and converts the received RFID signal properly for the mobile terminal. 
     Hereinafter, a method of operation of the antenna unit according to the present invention is described in detail. 
     The sensor  160  detects the position of the antenna  110  by identifying whether the antenna  110  is connected to the first contact  111 . If the antenna  110  is located at the first contact  111 , the sensor controls the switch  120  to connect the diplexer  130  to the first matching circuit  121 . If the antenna  110  is not located at the first contact  111 , the sensor controls the switch  120  to connect the diplexer  130  to the second matching circuit  122 . 
     The antenna  110  receives an RFID signal and a T-DMB signal. The received signal is transmitted to the diplexer  130  through a matching circuit  121  or  122 . The diplexer  130  separates the RFID signal and the T-DMB signal, and transmits the separated signals to the first signal processing unit  140  and the second signal processing unit  150 , respectively.  FIG. 2  is a block diagram showing a configuration of an antenna unit  200  of a mobile terminal according to another embodiment of the present invention. In the present invention, a first signal and a second signal are an RFID signal and an S-DMB signal, respectively. The antenna unit  200  includes components similar to the antenna unit  100  shown in  FIG. 1 , except that a second signal processing unit  250  further includes an auxiliary antenna  251 . Therefore, detailed descriptions of components similar to those of  FIG. 1  are omitted. 
     Referring to  FIG. 2 , the second signal processing unit  250  is connected to a diplexer  230  and the auxiliary antenna  251 . The auxiliary antenna  251  is used for receiving S-DMB signals when the mobile terminal  200  is located in an area providing a weak radio wave field. The second signal processing unit  250  receives the S-DMB signals both from the diplexer  230  and from the auxiliary antenna  251 , and selects the stronger signal. That is, the antenna unit  200  operates as a diversity antenna unit. 
       FIG. 3  is a block diagram showing a configuration of an antenna unit  300  of a mobile terminal according to another embodiment of the present invention. Referring to  FIG. 3 , the antenna unit  300  includes a first antenna  310 , switch  320 , diplexer  330 , duplexer  340 , first signal processing unit  350 , second antenna  351 , second signal processing unit  360 , third signal processing unit  370 , sensor  380 , and band reject filter  390 . 
     The first antenna  310  may receive a first signal, second signal, and third signal having different frequency bands from each other. The first signal, second signal, and third signal may be a mobile communication signal, RFID signal, and DMB signal, respectively. The mobile communication signal is a signal used for conversation through a mobile terminal. When the mobile terminal is located in an area providing a strong radio field, the antenna  310  may be used in a state of being inserted within the mobile terminal, and thereby the appearance of the mobile terminal is improved. However, when the mobile terminal is located in an area providing a weak radio field, the antenna  310  may be used in a state of being extended outside of the mobile terminal, and thereby the performance of the antenna  310  is improved. When the antenna  310  is extended outside of the mobile terminal  300 , the antenna  310  is connected to a first contact  311 . When the antenna  310  is inserted into the mobile terminal, the antenna  310  is connected to a second contact  312 . 
     The first contact  311  is connected to a first branch  321 . The first branch  321  joins the first signal processing unit  350 , second signal processing unit  360 , and third signal processing unit  370  together. The first branch  321  is connected to the first signal processing unit  350  through the switch  320 , and is connected to the second signal processing unit  360  and the third signal processing unit  370  through a second branch  322 . 
     The switch  320  is connected to the second antenna  351  transmitting and receiving the first signal. The switch  320  is connected also to the first contact  311  through the sensor  380 . The sensor  380  identifies whether the first antenna  310  is connected to the first contact  311 , and thereby detects the position of the first antenna  310 . The switch  320  selectively connects to the first branch  321  or to the second antenna  351  according to the position of the first antenna  310 . When the first antenna  310  is connected to the first contact  311 , the switch  320  connects the duplexer  340  to the first branch  321 . When the first antenna  310  is connected to the second contact  312 , the switch  320  connects the duplexer  340  to the second antenna  351 . 
     The switch  320  is connected to the duplexer  340  and the first signal processing unit  350 . Because the duplexer  340  includes a band pass filter for passing frequency bands of mobile communication signals, only the mobile communication signal is transmitted to the first signal processing unit  350  by the duplexer  340 . 
     The second branch  322  is connected to the second contact  312 , first branch  321 , and band reject filter  390 . The band reject filter  390  is connected to the diplexer  330 . The band reject filter  390  transmits only the RFID signal and DMB signal to the diplexer  330  by removing the mobile communication signal. The diplexer  330  transmits the RFID signal and the DMB signal, by separating them, to the second signal processing unit  360  and the third signal processing unit  370 , respectively. 
     Hereinafter, an operation method of the antenna unit according to this embodiment of the present invention is described in detail. 
     The first antenna  310  transmits and receives a mobile communication signal, RFID signal, and DMB signal. If the first antenna  310  is extended outside of the mobile terminal, the first antenna  310  is connected to the first contact  311 . The sensor  380  identifies that the first antenna  310  is connected to the first contact  311 , and controls the switch  320  to connect the duplexer  340  to the first branch  321 . 
     The three signals received through the first antenna  310  are transmitted from the first branch  321  to the switch  320  and the second branch  322 . However, only the mobile communication signal is transmitted to the first signal processing unit  350  by the duplexer  340 . Among the three signals transmitted to the second branch  322 , the mobile communication signal is removed by the band reject filter  390 , and only the RFID signal and DMB signal are allowed to pass. The passed RFID signal and DMB signal are separated by the diplexer  330 , and transmitted to the second signal processing unit  360  and the third signal processing unit  370 , respectively. 
     If the first antenna  310  is inserted within the mobile terminal, the first antenna  310  is connected to the second contact  312 . The sensor  380  identifies that the first antenna  310  is not connected to the first contact  311 , and controls the switch  320  to connect the duplexer  340  to the second antenna  351 . Accordingly, a mobile communication signal received through the second antenna  351  is transmitted to the first signal processing unit  350  through the duplexer  340 . 
     Among the signals received by the first antenna  310 , the mobile communication signal is removed by the band reject filter  390 , and only the RFID signal and DMB signal are allowed to pass. The passed RFID signal and DMB signal are separated by the diplexer  330 , and transmitted to the second signal processing unit  360  and the third signal processing unit  370 , respectively. 
       FIG. 4  is a block diagram showing a configuration of an antenna unit of a mobile terminal according to another embodiment of the present invention. Referring to  FIG. 4 , an antenna unit  400  this embodiment of the present invention includes a first antenna  410 , first switch  420 , first matching circuit  421 , second matching circuit  422 , second switch  425 , diplexer  430 , duplexer  440 , first signal processing unit  450 , second antenna  451 , second signal processing unit  460 , third signal processing unit  470 , sensor  480 , and band reject filter  490 . In the description of an antenna unit  400 , detailed descriptions of components similar to those of  FIG. 3  are omitted. 
     The first switch  420  is connected to a first contact  411  through the first matching circuit  421  and to a second contact  412  through the second matching circuit  422 . The matching circuits  421  and  422  are used for optimizing impedance corresponding to each path. The sensor  480  detects the position of the first antenna  410  and controls the first switch  420  and the second switch  425 . 
     If the first antenna  410  is connected to the first contact  411 , the sensor  480  controls the first switch  420  to connect a branch  423  to the first matching circuit  421 , and controls the second switch  425  to connect the duplexer  440  to the branch  423 . Accordingly, signals received through the first antenna  410  are transmitted to the duplexer  440  and the band reject filter  490  through the first matching circuit  421 . A method of processing the signals is similar to that described in  FIG. 3 . 
     If the first antenna  410  is connected to the second contact  412 , the sensor  480  controls the first switch  420  to connect the branch  423  to the second matching circuit  422  and controls the second switch  425  to connect the duplexer  440  to the second antenna  451 . Accordingly, signals received through the first antenna  410  are transmitted to the band reject filter  490  through the second matching circuit  422 . The duplexer  440  receives a mobile communication signal through the second antenna  451 . A method of processing the signals is similar to that described in  FIG. 3 . 
     The mobile terminal according to the present invention includes portable electronic devices, such as a mobile phone, Personal Digital Assistant (PDA), Global Positioning System (GPS), navigator, DMB receiver, and Portable Multimedia Player (PMP). 
     Additionally, the antenna unit according to the present invention may transmit and receive various signals having different frequency bands from each other, such as an RFID signal, S-DMB signal, T-DMB signal, GSM (Global System for Mobile communication) signal, mobile communication signal, and Bluetooth signal. 
     The present invention enables effective transmission and reception of multiple signals of various frequency bands by using a single antenna unit. Accordingly, the number of components, costs, and size of a mobile terminal may be reduced. Additionally, performance of an antenna may be improved by connecting to a proper matching circuit according to the position of the antenna. 
     Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention, as defined in the appended claims.