Patent Publication Number: US-6342858-B1

Title: Portable terminal device with chip antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to portable terminal devices, and more specifically, the invention relates to portable terminal devices such as note-type personal computers and electronic pocketbooks used as the nodes of wireless LAN systems, in which the covers of the devices are opened when used. 
     2. Description of the Related Art 
     Local Area Networks (LANs) have a structure in which the system is located in specified areas, for example, on the sites or premises of users in such a manner that communications are performed by mutually connecting various individual devices such as personal computers, servers, facsimiles, and the like. This system is used for various purposes such as gaining access to the database of servers via personal computers or gaining access to devices of other LAN systems via a communication network connected to the LAN system. 
     The connections between devices in LAN systems are very often made by wire communication channels. However, there are wireless LAN systems in which parts of the connections are make by wireless communication channels. In the wireless LAN systems, it is not necessary to mechanically connect individual devices to the LAN communication networks. Alternatively, the wireless LAN system can be used by registration, regardless of locations, as long as the devices are located in areas to which wireless radio waves can reach. Accordingly, this is a significantly useful system. 
     FIGS. 8A and 8B show the front view of a prior art portable terminal device and the side view thereof, respectively. A portable terminal device  50  has a main body  52  including a data entry keyboard  51  and the like, a cover  53  openably and closably attached to the main body  52 , a liquid crystal display  54  disposed on the inner side of the cover  53 , and a monopole antenna  55  for a wireless LAN system. In addition, a board having a ground, on which a calculation processing unit, a memory unit, and the like are mounted, is disposed inside the main body  52 , although the board is not shown in the figure. When the portable terminal device  50  is used, the cover  53  attached to the main body  52  is opened and the monopole antenna  55  is set up. When carried with a user, the cover  53  is closed in such a manner that the cover  53  and the main body  52  are put together, and the monopole antenna  55  is collapsed along the main body  53 . 
     Since a beam  56  in a horizontal direction can be obtained by the monopole antenna  55  in the above portable terminal device  50 , the monopole antenna  55  can sufficiently satisfy requirements as the directional characteristics of an antenna. Meanwhile, when carried with a user, the monopole antenna  55  is collapsed and the portable terminal device  50  is placed in a bag, or a pocket. As a result, since the monopole antenna  55  collapsed alongside of the main body  52  exists as a protruding item, the antenna is a nuisance to the user, and it also tends to be easily broken. To solve these problems, another prior art portable terminal device has been developed as shown in FIGS. 9A and 9B. 
     FIGS. 9A and 9B show the front view of another prior art portable terminal device and the side view thereof, respectively. When compared with the portable terminal device  50  (shown in FIGS.  8 A and  8 B), in a portable terminal device  60 , instead of disposing a monopole antenna, a wireless card  62  having a monopole antenna  61  is connected to a PCMCIA slot (not shown) of the main body  52 , by which a wireless communication function is given to the portable terminal device  60 . 
     In each of the above conventional portable terminal devices, however, since the portable terminal device and the wireless card are separated, there is a problem in that it is inconvenient for a user to carry such a type of portable terminal device with him. 
     In addition, since the wireless card is directly connected to the main body having the ground, there is a problem in that the directivity of the monopole antenna toward the main body side deteriorates significantly. Furthermore, there is a problem in that the directivity of the monopole antenna is influenced by digital noise from the main body. 
     SUMMARY OF THE INVENTION 
     To overcome the above described problems, preferred embodiments of the present invention provide a portable terminal device having the directivity of an antenna in a desired direction without increasing the size and weight of the portable terminal device. 
     One preferred embodiment of the present invention provides a portable terminal device comprising: a main body including a data entry keyboard; a cover openably and closably attached to the main body and establishing a connecting portion between the main body and the cover; a display disposed on the inner side of the cover; a chip antenna disposed on the cover at a place other than the display and opposed to the connecting portion; and the chip antenna comprising a ceramic base body, a conductor disposed at least either inside the base body or on a surface thereof, and a feeding terminal disposed on a surface of the base body and connected to one end of the conductor. 
     According to the above described structure and arrangement, the chip antenna is disposed on the cover at a place other than the display and opposed to the connecting portion. When the cover is opened to use the portable terminal device, the chip antenna is thereby positioned as far as possible from the main body having a ground. As a result, the gain of the chip antenna can be substantially uniform in the range of 360°. Therefore, a wireless communication channel in which a portable terminal device is stabilized in the range of 360° can be provided. 
     In addition, since the chip antenna includes the ceramic base body and the conductor formed at least either inside the base body or a surface thereof, the chip antenna can be miniaturized by a wavelength-shortening effect. As a result, the cover of the portable terminal device and the chip antenna can be integrated by disposing the antenna on the inner side of the cover of the portable terminal device. Accordingly, this arrangement contributes to miniaturization of the portable terminal device and weight reduction thereof. 
     Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING(S) 
     FIG. 1A is a partial perspective front view of a portable terminal device according to an embodiment of the present invention; and FIG. 1B is a partial perspective side view thereof. 
     FIG. 2 is a perspective view of a chip antenna used in the portable terminal device shown in FIG.  1 . 
     FIG. 3 is an exploded perspective view of the chip antenna shown in FIG.  2 . 
     FIG. 4 is a perspective view of a modified example of the chip antenna shown in FIG.  2 . 
     FIG. 5 is a graph of reflection characteristics of the chip antenna shown in FIG. 2 obtained when the chip antenna is mounted on the portable terminal device shown in FIG.  1 . 
     FIG. 6 is a chart illustrating the directivity of the chip antenna shown in FIG. 2 obtained when the chip antenna is mounted on the portable terminal device shown in FIG.  1 . 
     FIG. 7A is a view of the directivity of the chip antenna shown in FIG. 2 obtained when the chip antenna is positioned at the left edge on the cover of the portable terminal device shown in FIGS. 1A and 1B; FIG. 7B is a view thereof obtained when the chip antenna is positioned substantially at the center thereon; and FIG. 7C is a view thereof obtained when the chip antenna is positioned at the right edge thereon. 
     FIG. 8A is a front view of a conventional portable terminal device; and FIG. 8B is a side view thereof. 
     FIG. 9A is a front view of another conventional portable terminal device, and FIG. 9B is a side view thereof. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     FIG. 1A is a partial perspective front view of a portable terminal device according to an embodiment of the present invention, and FIG. 1B is a partial perspective side view thereof. A portable terminal device  10  has a main body  11 , and a cover  13  openably and closably attached to the main body  11  by a hinge  12 . 
     A data entry keyboard  14  is disposed on the upper surface of the main body  11 . The cover  13  attached to the main body  11  by the hinge  12  is retained at a position in which the cover  13  is closed to be put together with the main body  11  and at a position in which the cover  13  is stood up substantially vertically to the main body  11 . A display  15  is disposed on the inner side of the cover  13 , that is, at a position opposing the data entry keyboard  13  of the main body  11  when the cover  13  is closed. The display  15  is formed by a liquid crystal display or the like, and necessary information is displayed on the display  15 . In addition, data is inputted by the data entry keyboard  14  on the main body  11 . 
     A chip antenna  16  is disposed at a place other than the display  15  on the inner upper part of the cover  13 , e.g., as shown at the upper left, and is connected to a transmission/reception circuit disposed inside the main body  11 , although this is not shown in the figure. 
     FIG. 2 is a perspective view of a chip antenna used in the portable terminal device shown in FIGS. 1A and 1B. The chip antenna  16  has a rectangular-parallelopiped base body  1 , a conductor  2  formed inside the base body  1 , and a feeding terminal  3  formed on a surface of the base body  1 . The chip antenna  16  has, for example, dimensions of 9.5×2×2 (mm). 
     The conductor  2  is disposed in a spiral manner in the longitudinal direction of the base body  1 . In addition, one end of the conductor  2  is extended onto an end face of the base body  1  to be connected to the feeding terminal  3 , and the other end thereof forms a free end  4  inside the base body  1 . 
     FIG. 3 is an exploded perspective view of the chip antenna shown in FIG.  2 . The base body  1  is comprised of laminated rectangular dielectric-ceramic sheet layers  5   a  to  5   c.  The main components of the dielectric ceramic material are barium oxide, aluminum oxide, and silica. On the surfaces of the sheet layers  5   b  and  5   c,  conductive patterns  6   a  to  6   h  are disposed by printing, evaporation, bonding together, or plating. These conductive patterns are preferably formed of copper or an alloy of copper, and they have substantially L-letter forms or substantially straight-line forms. 
     Via-hole conductors  7  are formed at specified positions on the sheet layer  5   b  (at both ends of the conductive patterns  6   e  to  6   g , and at an end of a conductive pattern  6   h ) in the thickness direction. 
     In addition, the laminated sheet layers  5   a  to  5   c  are fired, and the conductive patterns  6   a  to  6   h  are connected by the via-hole conductors  7 . This arrangement permits the conductor  2  wound in a spiral form in the longitudinal direction of the base body  1  to be formed inside the base body  1 . Antennas of this general type are known from various U.S. patents assigned to the assignee. This application, e.g., U.S. Pat. No. 5,767,811. 
     FIG. 4 is a perspective view of a modified example of the chip antenna shown in FIG. 2. A chip antenna  16   a  shown in FIG. 4 has a rectangular-parallelopiped base body  1   a , a conductor  2   a  wound in a spiral form in the longitudinal direction of the base body  1   a  inside the base body  1   a , a ground electrode  8  opposing the conductor  2   a,  a feeding terminal  6   a  for applying voltage to the conductor  2   a  on a surface of the base body  1   a,  and a ground terminal  9  thereon, the ground terminal  9  being connected to the ground electrode  8 . 
     FIG. 5 is a graph of the reflection characteristics of the chip antenna shown in FIG. 2, obtained when the chip antenna is mounted on the portable terminal device shown in FIGS. 1A and 1B. In this figure, it is found that even when the chip antenna  16  is mounted on the portable terminal device  10 , the chip antenna  16  provides a resonant frequency of 2.45 (GHz) and a bandwidth of 116 (MHz). 
     FIG. 6 is a chart illustrating the directivity of the chip antenna shown in FIG. 2 obtained when the chip antenna is mounted on the portable terminal device shown in FIGS.  1 A and  1 B. A solid line indicates a case of the portable terminal device  10  of the embodiment (shown in FIGS. 1A and 1B) , and a broken line indicates a case of the conventional portable terminal device  60  (shown in FIG.  9 ). In this figure, the range of 0° to 360° is equivalent to the range of 0° to 360° each shown in FIGS. 1A,  1 B and  9 . 
     This figure shows that although the chip antenna used in the portable terminal device  10  of the embodiment of the invention exhibits a substantially constant gain in the range of 360°, the chip antenna of the conventional portable terminal device  50  shows deterioration of the gain in a 90° direction where the main body  52  exists. 
     FIG. 7A is a view of the directivity of the chip antenna shown in FIG. 2 obtained when the chip antenna is positioned at the left edge on the cover of the portable terminal device shown in FIGS. 1A and 1B, FIG. 7B is a view thereof obtained when the chip antenna is positioned substantially at the center thereon, and FIG. 7C is a view thereof obtained when the chip antenna is positioned at the right edge thereon. In these figures, it is found that the chip antenna  16  exhibits a substantially constant gain in the range of 360°, regardless of the positions of the chip antenna  16  shown in FIG. 2 on the cover  13 . 
     Although the description has been given of a portable terminal device of the above embodiment whose chip antenna is embedded in the inner side of the cover, the invention is applicable as long as the chip antenna is disposed on the cover. Thus, the chip antenna may be exposed on the inner side of the cover or the outer side thereof. 
     In addition, regarding antenna characteristics, the case of the chip antenna shown in FIG. 2 mounted on the portable terminal device has been described. However, the same antenna characteristics can also be obtained by the chip antenna shown in FIG. 4 mounted thereon. 
     Furthermore, although the case of the chip-antenna conductor  2 ,  2   a  disposed inside the base body  1 ,  1   a  has been described, the chip-antenna conductor  2 ,  2   a  may be disposed on a surface of the base body  1 ,  1   a.    
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the forgoing and other changes in form and details may be made therein without departing from the spirit of the invention.