Patent Publication Number: US-2011050512-A1

Title: Mobile terminal device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-202068 filed on Sep. 1, 2009, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a mobile terminal device. 
     BACKGROUND 
     Mobile terminal devices, such as mobile phones, have recently come to include not only a voice call function and a mail function but also a near field communication function and a 1 seg broadcast viewing function, thus increasing their functions. With the increase in the function of mobile terminal devices, the number of antennas also tends to increase. With the increase in the number of antennas of one mobile terminal device, various arrangements of antennas are under study. 
     Known examples of folding mobile terminal devices in which two casings are movably joined together with a hinge have a call antenna and a 1 seg broadcast receiving antenna (hereinafter referred to as a 1 seg antenna) disposed at different positions. 
       FIG. 4  is a diagram illustrating an example of the mobile terminal devices in which a call antenna and a 1 seg antenna are disposed at different positions. As shown in  FIG. 4 , a mobile terminal device  110  in which a first casing  111  and a second casing  112  are movably joined together with a hinge has a monopole antenna  114  as a call antenna in the vicinity of the hinge  113  and an extendable rod antenna  115  as a 1 seg antenna on a side of the second casing  112 . 
       FIG. 5  is a diagram illustrating another example of the mobile terminal devices in which a call antenna and a 1 seg antenna are disposed at different positions.  FIG. 5  illustrates the same components as those of  FIG. 4  using the same reference numerals. In a mobile terminal device  120  shown in  FIG. 5 , an internal antenna  121  is disposed at the opposite ends of the second casing  112  to the hinge  113 . 
     The known mobile terminal devices shown in  FIGS. 4 and 5  have a special space for disposing the 1 seg antenna at a side or end of the second casing  112 . Providing the special space for the antenna poses the problem of hindering size reduction of the device. 
     Thus, to solve such a problem, known mobile terminal devices use a hinge that joins the two casings as an antenna for a purpose other than for calling. In these mobile terminal devices, the hinge is formed of an electrically conductive material. The hinge is supplied with electricity from a circuit board provided in the casing and thus functions as an antenna for receiving radio waves from a global positioning system (GPS). 
     Since these mobile terminal devices use the hinge itself as a GPS antenna, there is no need to provide another space for a GPS antenna to a casing joined with the hinge. Accordingly, the devices can be reduced in size. 
     Japanese Laid-open Patent Publication Nos. 2007-88692 and 2009-94859 are examples of related art 
     However, the mobile terminal device described above has a problem in that the hinge cannot be used as a 1 seg antenna. 
     Specifically, the foregoing mobile terminal device uses the hinge as a GPS antenna. The frequency range of a GPS radio wave is about 1,575 MHz, and the corresponding electrical length of the hinge is about 20 to 30 mm. On the other hand, the frequency band of a 1 seg radio wave is relatively low and wide (about 400 to 800 MHz). Therefore, if the hinge of the above mobile terminal device is used as a 1 seg antenna, its electrical length is insufficient. Thus, the above mobile terminal device cannot use the hinge as a 1 seg antenna. 
     SUMMARY 
     According to an aspect of the embodiment, a mobile terminal device includes: a first casing having a first antenna element; a second casing having a second antenna element; and a joint for rotatably joining the first casing and the second casing, the joint having third antenna element for electrically connecting the first antenna element and the second antenna element. 
     The object and advantages of the embodiment will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an outside perspective view of a mobile phone according to an embodiment; 
         FIG. 2  is an enlarged perspective view illustrating the periphery of a joint portion of the mobile phone according to the embodiment; 
         FIG. 3  is a block diagram illustrating the configuration of a 1 seg circuit unit; 
         FIG. 4  illustrates an example of a mobile terminal device in which a call antenna and a 1 seg antenna are disposed at different positions; and 
         FIG. 5  is illustrates another example of the mobile terminal device in which a call antenna and a 1 seg antenna are disposed at different positions. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of a mobile terminal device laid open in this application will be described hereinbelow with reference to the drawings. 
     This embodiment is an example in which the mobile terminal device laid open in this application is applied to a folding mobile phone.  FIG. 1  is an outside perspective view of the mobile phone according to this embodiment.  FIG. 2  is an enlarged perspective view illustrating the periphery of a joint portion of the mobile phone according to this embodiment. 
     As shown in  FIGS. 1 and 2 , the mobile phone  10  includes a first casing  11  on the display side and a second casing  12  on the operating section side. The first casing  11  and the second casing  12  are movably joined together with a joint portion  13 . The first casing  11  and the second casing  12  are shaped like a box from, for example, a lightweight high-strength magnesium alloy. An outer cover (not shown) for preventing exposure of the joint portion  13  is provided in the vicinity of the joint portion  13 .  FIG. 1  shows a state in which the first casing  11  and the second casing  12  are put one on another by rotating the second casing  12  to the first casing  11 . 
     The first casing  11  has a circuit board  14 , a receiver, a display formed of a liquid crystal display (LCD) device (not shown), etc. On the other hand, the second casing  12  has a circuit board  15 , operation keys, a microphone (not shown), etc. 
     As shown in  FIG. 2 , the circuit board  15  of the second casing  12  has a radio circuit unit  16  for voice calls, a 1 seg circuit unit  17 , which is a radio circuit for 1 seg broadcasting, a processing circuit unit including a processor and a memory (not shown), etc. The circuit board  14  of the first casing  11  and the circuit board  15  of the second casing  12  are electrically connected by a connecting cable  18  that passes through the joint portion  13 . 
     A call antenna  19  for voice calls is disposed at the joint portion  13  side of the second casing  12 . The call antenna  19  is connected to the radio circuit unit  16  of the circuit board  15  via a conductive member  20 , such as a flexible cable. The call antenna  19  transmits and receives radio waves in a first frequency band by being supplied with electricity from the radio circuit unit  16 . The radio circuit unit  16  performs a predetermined process necessary for radio call, such as demodulation, on reception signals in the first frequency band input through the call antenna  19 . 
     An example of the first frequency band is a relatively high frequency narrow band, such as 2 GHz, which is a frequency band for voice calls. 
     The joint portion  13  is a hinge module formed of an electrically conductive material, such as metal, and rotatably joins the first casing  11  and the second casing  12 . The joint portion  13  is connected to the 1 seg circuit unit  17  of the circuit board  15  via a conductive member  21  such as a metal plate. The joint portion  13  has a predetermined electrical length that allows reception of radio waves in a second frequency band that is lower and wider than the first frequency band and receives radio waves in the second frequency band by being supplied with electricity from the 1 seg circuit unit  17 . 
     Assuming that the first frequency band is a 2 GHz band for voice calls, the second frequency band is a relatively low and wide frequency band, such as 400 MHz to 800 MHz bands, for 1 seg broadcasting. 
     Specifically, the joint portion  13  includes a first hinge  22  and a second hinge  23 . Each of the first hinge  22  and the second hinge  23  is conductive metal. The first hinge  22  joins the first casing  11  and the second casing  12  rotatably about a first shaft  22   a . The second hinge  23  joins the first casing  11  and the second casing  12  rotatably about a second shaft  23   a  perpendicular to the first shaft  22   a.    
     The first hinge  22  has a first antenna element, a second antenna element, and a third antenna element. The first casing  11  has the first antenna element. The second casing  12  has the second antenna element. The first hinge  22  has a first joint for rotatable joining the first antenna element and the second antenna element conductively. The first joint can have a first roller as the third antenna element for connecting the first antenna element with the second antenna element conductively. The total length of the first, second and third antenna elements can correspond to an electrical length for receiving a radio wave of 1 seg broadcasting. The third antenna element can be a roller fixed with the first antenna element. The roller contacts with the second antenna element. 
     The second hinge  23  has a fourth antenna element, a fifth antenna element, and a sixth antenna element. The first casing  11  has the fourth antenna element. The second casing  12  has the fifth antenna element. The second hinge  23  has a second joint for rotatable joining the fourth antenna element and the fifth antenna element conductively. The second joint can have a second roller as the sixth antenna element for connecting the fourth antenna element with the fifth antenna element conductively. The total length of the fourth, fifth and sixth antenna elements can correspond to an electrical length for receiving a radio wave of 1 seg broadcasting. The sixth antenna element can be a roller fixed with the fourth antenna element. The roller contacts with the fifth antenna element. 
     The first hinge  22  is connected with the second hinge  23  conductively. The first antenna element or the second antenna element of the hinge  22  can be the same as the fourth antenna element of the hinge  23 . The total electrical length of the joint portion  13  including the length of the first hinge  22  and the length of the second hinge  23  can be set to one quarter of the wavelength of radio waves in the second frequency band. By setting the total electrical length at one quarter of the radio waves in the second frequency band, the joint portion  13  functions as an antenna that resonates with the radio waves in the second frequency band. Thus, the mobile phone  10  can efficiently receive the radio waves in the second frequency band. 
     The 1 seg circuit unit  17  supplies electricity to the joint portion  13  and performs a predetermined process necessary for receiving 1 seg broadcasts, such as demodulation, on reception signals in the second frequency band input through the joint portion  13 . A concrete configuration of the 1 seg circuit unit  17  will be described hereinbelow. 
       FIG. 3  is a block diagram illustrating the configuration of the 1 seg circuit unit  17 . As shown in  FIG. 3 , the 1 seg circuit unit  17  includes a phase-adjustment circuit section  24 , a frequency cutoff section  25 , a matching circuit section  26 , and a 1 seg-circuit main body  27 . 
     The phase-adjustment circuit section  24  adjusts the phase of an electric current flowing through the joint portion  13  so that the reception characteristic of the joint portion  13  for radio waves in the second frequency band can be maintained. Furthermore, the phase-adjustment circuit section  24  adjusts the phase of an electric current flowing through the joint portion  13  so that the phase of an electric current flowing through the call antenna  19  and the phase of the electric current flowing through the joint portion  13  have phases other than opposite phases. 
     The frequency cutoff section  25  is formed of, for example, a low-pass filter, a high-pass filter, or a band-pass filter. The frequency cutoff section  25  cuts off the first frequency band received by the call antenna  19  and allows the second frequency band received by the joint portion  13  to pass through. 
     The matching circuit section  26  matches the impedance of the joint portion  13  to the input impedance of the 1 seg-circuit main body  27  to rectify an electric current flowing between the joint portion  13  and the 1 seg-circuit main body  27 . 
     The 1 seg-circuit main body  27  supplies electricity to the joint portion  13 , demodulates reception signals in the second frequency band input from the joint portion  13 , and displays an image on the display (not shown) provided on the first casing  11  using the demodulated signals. 
     As has been described above, in this embodiment, the conductive joint portion  13  that joins the first casing  11  and the second casing  12  has a predetermined electrical length that allows reception of radio waves in the second frequency band lower and wider than the first frequency band of radio waves received by the call antenna  19 . The joint portion  13  receives radio waves in the second frequency band by being supplied with electricity from the circuit board  15  of the second casing  12 . Thus, according to this embodiment, the mobile phone  10  can use the joint portion  13  that joins the casings as an antenna for receiving relatively low-frequency wide-band radio waves like radio waves for 1 seg broadcasting. 
     Furthermore, in this embodiment, the joint portion  13  includes the first hinge  22  and the second hinge  23 , and the electrical length including the length of the first hinge  22  and the length of the second hinge  23  is set to one quarter of the wavelength of the radio waves in the second frequency band. Thus, according to this embodiment, the mobile phone  10  can easily ensure the electrical length of the joint portion  13  for receiving relatively low-frequency wide-band radio waves like radio waves for 1 seg broadcasting. 
     Furthermore, this embodiment includes the phase-adjustment circuit section  24 , at the circuit board  15 , for adjusting the phase of an electric current flowing through the joint portion  13  so that the reception characteristic of the joint portion  13  for radio waves in the second frequency band can be maintained. Thus, according to this embodiment, even if the phase of an electric current flowing through the joint portion  13  changes with the movement of the joint portion  13 , the mobile phone  10  can stably receive relatively low-frequency wide-band radio waves like radio waves for 1 seg broadcasting. 
     Furthermore, in this embodiment, the phase-adjustment circuit section  24  adjusts the phase of an electric current flowing through the joint portion  13  so that the phase of an electric current flowing through the call antenna  19  and the phase of the electric current flowing through the joint portion  13  have phases other than opposite phases. Thus, according to this embodiment, the mobile phone  10  can avoid interference between the electric current flowing through the call antenna  19  and the electric current flowing through the joint portion  13 . This allows the mobile phone  10  to prevent degradation of the antenna characteristics of both of the call antenna  19  and the joint portion  13 . 
     Furthermore, in this embodiment, the circuit board  15  includes the frequency cutoff section  25  that cuts off the first frequency band received by the call antenna  19  and allows the second frequency band received by the joint portion  13  to pass through. Thus, according to this embodiment, the mobile phone  10  can prevent part of radio waves in the first frequency band received by the call antenna  19  from being caught by the joint portion  13 . This allows the mobile phone  10  to further prevent degradation of the antenna characteristics of both of the call antenna  19  and the joint portion  13 . 
     In this embodiment, description is made on the technology for receiving radio waves in different frequency bands by a folding mobile phone using a hinge module. The above technology can be applied not only to the folding mobile phones using the illustrated hinge module but also to folding mobile phones using other various hinge modules. Furthermore, the above technology can be applied not only to the folding type using the hinge module but also to mobile phones in which a movable casing can be moved relative to a fixed casing using, for example, a slide type or a plane rotating type of joint portion. 
     Furthermore, while this embodiment has been described when applied to a mobile phone as a mobile terminal device, the present invention is not limited thereto. For example, the present invention can also be applied to other various mobile terminal devices such as compact information processing terminals like personal digital assistants (PDAs), compact music playback units, portable TVs, and mobile game machines. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.