Patent Publication Number: US-2009239595-A1

Title: Multi-band built-in antenna

Description:
PRIORITY 
     This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Oct. 1, 2007 and assigned Serial No. 2007-98693, the entire disclosure of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna for a portable wireless terminal. More particularly, the present invention relates to a multi-band built-in antenna for receiving and transmitting multi-band signals for a portable wireless terminal. 
     2. Description of the Related Art 
     Currently, portable wireless terminals such as Personal Communication Systems (PCS), Global Positioning Systems (GPS), a Personal Digital Assistant (PDA), cellular phones and wireless notebook computers, are being widely used. Since their introduction, these terminals have evolved into smaller and slimmer devices based on user demand. Also, these terminals are being provided with various functions in addition to the voice communication function. Therefore, in order to continue satisfying user desires and demands, the design of the terminal is focused on a size reduction while maintaining or improving the functions as well as providing new ones. 
     Portable wireless terminals include an antenna for radio communication. The antenna can be classified into an external type and a built-in type. An external type antenna is installed in a portable wireless terminal in such a manner that it protrudes from the terminal body. Conversely, a built-in antenna is installed on a Printed Circuit Board (PCB, hereinafter also called a motherboard) located internally of a portable wireless terminal without any external protrusion. Further, an external antenna can be classified into a dipole antenna having a feed part and a ground part or a monopole antenna having only a feed part. The monopole antenna has a feed part electrically connected to a feed pad of a PCB. A built-in antenna can be classified in the same way. The built-in antenna is more widely used than the external antenna because of its portability and the improvements it affords to the portable terminal&#39;s external appearance. 
     Though the performance of the antenna is proportional to the size of the antenna, a large antenna makes the terminal bigger. Therefore, there is a need for an antenna that can improve radiation performance without increasing its size and reduce a Specific Absorption Rate (SAR). 
       FIG. 1  is a perspective view of a conventional dual-band built-in antenna. 
     Referring to  FIG. 1 , the antenna  100  is mounted on a mother board (i.e. PCB, not shown) and is electrically connected with the PCB. 
     The antenna  100  includes a radiator  120  to radiate radio signals and a carrier  110  on which the radiator  120  is affixed. The carrier  110  is manufactured by molding. 
     The radiator  120  includes a conductive plate  121  manufactured by sheet metal processing. The plate  121  includes a feed part  124  and a ground part  125 , projected downwardly from a portion of the plate  121 , coupling with the PCB. Also, the carrier  110  includes a plurality of fixing protrusions projected upwardly, and the plate  121  includes a plurality of fixing holes  123 , each corresponding to a fixing protrusion. The plate  121  can be fixed to the carrier  110  by any suitable means, such as hot melt adhesion or ultrasonic welding. 
     The radiator  120  can be partitioned into a first radiation part  121 A for processing signals of a high frequency band and a second radiation part  121 B for processing signals of a low frequency band. That is, the first radiation part  121 A and the second radiation part  121 B process signals of different frequency bands. 
     Also, the first radiation part  121 A and the second radiation part  121 B have different radiation patterns to process signals of different frequency bands. Each radiation pattern has a width and a length. For example, a radiation pattern of the first radiation part  121 A can have a greater average width than that of the second radiation part  121 B. The feed part  124  provides the plate  121  with a transmission signal from the PCB. When the signal to be transmitted is received from the PCB, the first radiation part  121 A processes signals of a high frequency band and the second radiation part  121 B processes signals of a low frequency band. 
     The dual-band built-in antenna  100  only processes signals of dual-frequency bands. However, as communication technologies continue to advance, portable wireless terminals are becoming more sophisticated including the ability to operate in three or more frequency bands. Therefore, there is a need for an antenna that can accommodate and improve the processing of signals for three or more frequency bands without increasing the size of the antenna or the size of the terminal. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an object of the present invention is to provide a multi-band built-in antenna for a portable wireless terminal that can process multi-band signals without increasing the size of the terminal. 
     Another object of the present invention is to provide a multi-band built-in antenna for a portable wireless terminal that can improve radiation performance while maintaining a slim and lightweight terminal. 
     A further object of the present invention is to provide a multi-band built-in antenna for a portable wireless terminal that can improve radiation performance of a high frequency band for a Digital Cellular System (DSC) and a Personal Communication System (PCS). 
     According to an aspect of the present invention, a multi-band built-in antenna for a portable wireless terminal is provided. The antenna includes a first radiation part for processing signals of a first frequency band, a second radiation part, spaced apart from the first radiation part and electrically connected to the first radiation part, for processing signals of a second frequency band that are lower than the first frequency band and a sub-radiator that is electrically connected to the second radiation part and is movable. 
     According to another aspect of the present invention, a portable wireless terminal is provided. The terminal includes an RF board having a feeding unit and grounding unit, a carrier fixed on the RF board, a first radiation part for processing signals of a first frequency band, fixed to the top surface of the carrier, a second radiation part, horizontally spaced apart from the first radiation part and electrically connected to the first radiation part, fixed to the top surface of the carrier, for processing signals of a second frequency band lower than the first frequency band, a feed part and a ground part, protruding from one end of at least one of the first radiation part and the second radiation part and electrically connected to the feeding unit and the grounding unit, respectively and a sub-radiator that is electrically connected to the second radiation part and is movable. 
     Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a conventional dual-band built-in antenna; 
         FIG. 2  is a perspective view of a portable wireless terminal using a multi-band built-in antenna according to an exemplary embodiment of the present invention; 
         FIG. 3A  is an exploded perspective view of a multi-band built-in antenna according to an exemplary embodiment of the present invention; 
         FIG. 3B  is a perspective view of a multi-band built-in antenna according to an exemplary embodiment of the present invention; 
         FIG. 4A  is a partial cross-sectional view corresponding to line A-A′ of  FIG. 3B ; 
         FIG. 4B  is a partial cross-sectional view corresponding to line B-B′ of  FIG. 3B ; 
         FIG. 5  is a partial view of a portable wireless terminal according to an exemplary embodiment of the present invention; 
         FIG. 6  is a graph showing a Voltage Standing Wave Ratio (VSWR) of the conventional dual-band built-in antenna illustrated in  FIG. 1 ; 
         FIG. 7  is a graph showing VSWR and a partial plane view of a multi-band built-in antenna according to an exemplary embodiment of the present invention, when a sub-radiator is in a position to process signals of a Digital Cellular System (DCS) frequency; and 
         FIG. 8  is a graph showing VSWR and a partial plane view of a multi-band built-in antenna according to an exemplary embodiment of the present invention, when a sub-radiator has moved to process signals of a Personal Communication Systems (PCS) frequency. 
     
    
    
     Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features and structures. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
     Though a slide type terminal is illustrated, this is merely for example and should not be considered as limiting. That is, the present invention can also be applied to other and various types of terminals, such as a flip type terminal, a folder type terminal, a bar type terminal and the like. 
       FIG. 2  is a perspective view of a portable wireless terminal using a multi-band built-in antenna according to an exemplary embodiment of the present invention. 
     Referring  FIG. 2 , a portable wireless terminal  200  includes a main body  210  and a sub-body  220  that slides on and relative to the main body  210 . The main body  210  includes a keypad assembly  203  as a data input device and a microphone  204  located under the keypad assembly  203  for input of voice signals. Also, the sub-body  220  includes an earpiece  201  to output voice or other audible signals and a display  202  under the earpiece  201 . In an exemplary implementation, the display  202  may be a Liquid Crystal Display (LCD) having up to millions of pixels. Also, if the LCD is provided as a touch screen, the display  202  may perform a part or all of the functions of an input unit, either supplemental or in place of keypad assembly  203 . 
     The portable wireless terminal  200  processes signals of multiple frequency bands using a multi-band built-in antenna shown, for example, in  FIG. 3A  according to an exemplary embodiment of the present invention. 
     As will be explained in more detail below, the multi-band built-in antenna of the portable wireless terminal  200  may include a sub-radiator. To process signals of the multiple frequency bands, the sub radiator may be movable. 
     For example, the sub-radiator may be moved to a first position for processing signals of a Global System for Mobile Telecommunication (GSM) and signals of a Digital Cellular System (DCS) and is movable to a second position for processing signals of a GSM and a Personal Communication System (PCS). 
       FIGS. 3A and 3B  are exploded perspective views of a multi-band built-in antenna  300  according to an exemplary embodiment of the present invention and  FIGS. 4A and 4B  are partial cross section views respectively corresponding to lines A-A′ and B-B′ illustrated in  FIG. 3B . 
     Referring to  FIGS. 3A to 4B , the multi-band built-in antenna  300  includes a radiator  320  for transmitting and receiving radio frequency signals, a carrier  310  on which the radiator  320  is affixed and a sub-radiator  330  connected to the radiator  320 . The sub-radiator  330  is movable. 
     The radiator  320  includes a conductive plate  321  having a radiation pattern for processing radio frequency signals. In an exemplary implementation, the conductive plate  321  is made by press processing. In addition, the conductive plate  321  is for electrically connecting the antenna  300  to a circuit board (e.g. a mother board or a Printed Circuit Board (PCB)) of a portable wireless terminal. The conductive plate  321  includes a feed part  324  and a ground part  325 . The feed part  324  and the ground part  325  respectively protrude from one end of the radiator  320 . Based on the configuration of the radiator  320  being affixed to the carrier  310 , and the carrier  310  mounted on the PCB, the feed part  324  and the ground part  325  may be electrically connected to the PCB. 
     The carrier  310  also includes a body  311 . In an exemplary implementation, the body  311  is made by injection molding. The body  311  of the carrier  310  includes one or more fixing protrusions  313  projecting upwardly from the top of the body  311 . The plate  321  includes a plurality of fixing holes  323  corresponding to the fixing protrusions  313 . Therefore, the radiator  320  can be fixed to the carrier  310  using the fixing holes  323  by any suitable fusion means, such as hot melt adhesion, ultrasonic welding and the like. 
     The plate  321  of the radiator  320  includes a guide slot  322 . In an exemplary implementation, the guide slot  322  is formed as an elongated hole which penetrates through the plate  321 . In addition, the sub-radiator  330  includes a guide protrusion  333 , projected downwardly from a lower or bottom side of the sub-radiator  330 . Furthermore, the body  311  of the carrier  310  includes a first sub-slot  312  corresponding to the guide protrusion  333 . As best illustrated in  FIGS. 3B ,  4 A and  4 B, when the multi-band built-in antenna is assembled, the guide protrusion  333  simultaneously passes through both the guide slot  322  and through the first sub-slot  312  which are aligned with each other. Therefore, the guide protrusion  333  may be moved along a path of the guide slot  322 . Also, the sub-radiator  330  is electrically connected to the radiator  320  and maintains the electrical connection while moving from one position to another. 
     In addition, a guide block  334  is provided to secure the configuration of the movable sub-radiator  330 . More specifically, the guide block  334  is fixed to a lower side of the guide protrusion  333  by a fixing means, such as a screw  336 . The guide block  334  has a larger width than the guide protrusion  333 . Also, as best illustrated in  FIG. 4B , the body  311  of the carrier  310  includes a second sub-slot  312 ′. The second sub-slot  312 ′ has a greater width than the first sub-slot  312  and is located under the first sub-slot  312 . Accordingly, the guide block  334 , fixed by fixing means  336  to the guide protrusion  333  and having a width correlating to the width of the second sub-slot  312 ′, is moved along a path of the second sub-slot  312 ′ while the guide protrusion  333  moves along a path of the guide slot  322 . Furthermore, the guide block  334 , having a width greater than the width of the guide protrusion  333  and greater than the width of the first sub-slot  312 , prevents the guide protrusion  333  from escaping the guide slot  322 . Thus, the guide block  334  secures the sub-radiator  330  as it moves in a sliding manner. 
     Therefore, the sub-radiator  330  is not separated upwardly from the radiator  320  because of the guide block  334  as an obstacle. Also, the sub-radiator  330  is not separated downwardly from the radiator  320  because of the plate  321  as an obstacle. Once the sub-radiator  330  is connected to the radiator  320  by the guide block  334 , the sub-radiator  330  can be moved horizontally while being secured from escaping in an upward or downward direction. 
     The sub-radiator  330  includes a conductive sub-plate  331  having a radiation pattern, for example a right angle pattern, ‘ ’. The sub-radiator  330  includes a handling protrusion  332  which allows for control of its movement by a user. In an exemplary implementation, the handling protrusion  332  is projected upwardly from top of the plate  331 . In a further exemplary implementation, the handling protrusion  332 , the guide protrusion  333  and the guide block  334  are all located on a perpendicular extension of the sub-plate  331 . 
     The handling protrusion  332  can be a non-conductive material. However, considering the necessary performance of the antenna, the handling protrusion  332  may also be a conductive material. As illustrated in  FIG. 5  and explained in greater detail below, the handling protrusion  332  is exposed through an exterior frame  400  of the terminal. Herein, the exterior frame  400  of the terminal  200  includes a third sub-slot  401 , providing a path. The handling protrusion  332  is moveable along the path provided by the third sub-slot  401 . 
     Furthermore, as best illustrated in  FIGS. 3B and 4B , the sub-plate  331  covers or surrounds the plate  321  near the guide protrusion  333 . That is, the sub-plate  331  has a prominent part and a depressive part for substantially following the contour of the plate  321 , especially the guide slot  322 , so that, as the sub-plate  331  extends laterally relative to the plate  321 , the plate  321  and the sub-plate  331  are substantially in the same plane. Accordingly, the vertical space required to mount both the plate  321  and the sub-plate  331  is substantially the same as the vertical space required to mount the plate  321  by itself. Furthermore, as the radiator  330  is moved along the guide slot  322 , the prominent and depressive parts will provide additional support and stability for the sub-plate  331  and provide a better electrical coupling to the radiator  320 . 
     The radiator  320  includes a first radiation part  321 A for processing signals of a first frequency band and a second radiation part  321 B, spaced apart from and electrically connected to the first radiation part  321 A, for processing signals of a second frequency band lower than the first frequency band. The first radiation part  321 A and the second radiation part  321 B comprise the plate  321 . That is, the first radiation part  321 A and the second radiation part  321 B are one body, and they can separately process signals of multiple frequency bands. 
     In the illustrated example, the second radiation part  321 B includes the guide slot  322  which allows the sub-radiator  330  to slideably move. In addition, the second radiation part  321 B includes the feed part  324  and the ground part  325 , each protruding from one end of the second radiation part  321 B. By mounting the antenna  300  on a PCB or mother board of a portable wireless terminal, the feed part  324  and the ground part  325  are electrically connected to the PCB of the portable wireless terminal. Here, the feed part  324  provides the first radiation part  321 A and the second radiation part  321 B with an electrical signal, for example an electrical current. Therefore, the first radiation part  321 A and the second radiation part  321 B radiate individually. 
     For example, the first radiation part  321 A processes signals of a higher frequency band, and the second radiation part  321 B processes signals of a lower frequency band. Herein, the first radiation part  321 A and the second radiation part  321 B comprise the plate  321 , having a radiation pattern. The radiation pattern has a length and a width for radiating various frequencies individually. For example, the radiation pattern length of the first radiation part  321 A is distinguishably longer than the radiation pattern length of the second radiation part  321 B. Accordingly, signals of a higher frequency band are processed by the first radiation part  321 A while signals of a lower frequency band are processed by the second radiation part  321 B. 
     Moreover, because the sub-radiator  330  is electrically connected to the second radiation part  321 B and is movable, the antenna  300  can process signals of an additional frequency band, beyond the higher frequency bands processed by the second radiation part  321 B without the sub-radiator  330 . 
     The conventional antenna  100  processes signals of dual-frequency bands, such as GSM and DCS. However, by including a sub-radiator  330 , an antenna according to an exemplary embodiment of the present invention can individually process signals of triple frequency bands, such as GSM, DCS and PCS, or more without increasing a size of the conventional antenna. 
     For example, as the sub-radiator  330  is connected electrically to the second radiation part  321 B and is selectively movable, the antenna  300  is able to process signals of a high frequency band, such as DCS and PCS, individually and selectively. As illustrated in  FIG. 4A , the sub-radiator  330  can move along an imaginary line at the selection of a user, thus allowing the portable terminal to process higher frequency signals that those processed by the second radiation part  321 B alone. 
       FIG. 5  is a partial view of a portable wireless terminal according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , an exterior frame  400  includes a third sub-slot  401  through which the position of the sub-radiator  330  may be controlled by a user. In an exemplary implementation, the third sub-slot  401  is provided as an elongated hole through the exterior frame  400 . More specifically, as described above, the multi-band built-in antenna  300  is installed in the terminal and the handling protrusion  332  of the sub-radiator  330  is exposed through the third sub-slot  401 . The exposed handling protrusion  332 , by means of its connection to the guide protrusion  333  movable along the guide slot  322 , allows movement of the sub-radiator  330 . Accordingly, by movement of the sub-radiator  330  using the handling protrusion  332 , a user may select which frequencies are to be targeted for reception. In addition, the handling protrusion  332  may include a suitable prominence to allow easier movement by the user. Furthermore, a surface of the exterior frame  400  may include symbols, figures, lettering or other indicia for indicating a specific frequency band, such as DCS and PCS, targeted for reception. 
       FIG. 6  is a graph illustrating a Voltage Standing Wave Ratio (VSWR) of the conventional dual-band built-in antenna illustrated in  FIG. 1 .  FIG. 7  includes a graph illustrating a VSWR and a partial plane view of the multi-band built-in antenna according to an exemplary embodiment of the present invention, when a sub-radiator is in a position to process signals of a Digital Cellular System (DCS) frequency.  FIG. 8  includes a graph illustrating a VSWR and a partial plane view of the multi-band built-in antenna according to an exemplary embodiment of the present invention, when the sub-radiator has moved to process signals of a Personal Communication Systems (PCS) frequency. 
     Referring to  FIGS. 6 to 8 , a comparison will be made between the conventional art and exemplary embodiments of the present invention. As illustrated in  FIG. 6 , the conventional dual-band built-in antenna  100  processes signals of a low frequency band (between points 1 and 2; e.g. GSM) and signals of a high frequency band (between points 3 and 4; e.g. DCS). Namely, the conductive plate  121  is specifically patterned to process signals of the GSM and DCS bands. Therefore, because a Voltage Standing Wave Ratio (VSWR) of PCS (points 5 and 6) is from 3 to 7 and over 8, performance of the conventional dual-band built-in antenna  100  is deteriorated for PCS. 
     Referring to  FIG. 7 , the sub-radiator  330  of the multi-band built-in antenna  300  is moved to process signals of a DCS band. As illustrated in  FIG. 7 , a VSWR of a low frequency band (points 1 and 2; e.g. GSM) indicates that the reception is substantially the same as in the conventional art. However, a VSWR of a high frequency band (points 3 and 4; e.g. DCS) is lower than that of the conventional antenna  100 . Therefore, it is evident that performance of the antenna  300  is improved in the DCS band, but performance of the antenna  300  in the PCS band (points 5 and 6) is not improved. 
     Referring to  FIG. 8 , the sub-radiator  330  of the multi-band built-in antenna  300  is moved to process signals of a PCS band. As illustrated in the VSWR graph of  FIG. 8 , performance of the antenna  300  in the GSM band (points 1 and 2) and the DCS band (points 3 and 4) indicates that the reception is substantially the same as in the conventional art regarding these two bands. However, it is evident that performance of the antenna  300  is improved in the PCS band (points 5 and 6). 
     In conclusion, performance of the antenna  300  in the low frequency band (GSM) is independent of the added radiator  330 ′ movement. However, to better process signals of high frequency bands (DCS band or PCS band) for the antenna  300 , as the sub-radiator  330  is movable, performance of the antenna in a DCS band or a PCS band can improve markedly. 
     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.