Patent Publication Number: US-2011063175-A1

Title: Portable wireless device

Description:
TECHNICAL FIELD 
     The present invention relates to a slim foldable portable radio exhibiting high communication performance. 
     BACKGROUND ART 
     Various portable radios such as for instance portable phones, have hitherto been developed. Further, in relation to the portable phones, various foldable portable phones that are open-able and closable around a hinge section have already been developed. In such a foldable portable phone, since a display section is provided in an upper housing, a radio circuit is set in a lower housing because of a limited space in many times. Further, in order to minimize a transmission loss occurring between the radio circuit and an antenna, it is preferable to place the antenna in close proximity to the radio circuit. With this being the case, in order to reduce the transmission loss occurring between the radio circuit and the antenna and minimize influence of a hand on a communication state, the antenna is placed in close proximity to the hinge section of the lower housing in many cases. For instance, a collapsible foldable phone, such as that shown in  FIG. 9 , has hitherto been known as a specific example of such a foldable portable phone (see; for instance, Patent Document 1). 
     As shown in  FIG. 9 , a foldable portable phone  100  has a first antenna element  104  placed in an upper housing  101 ; a conductor element  105  that is placed in a lower housing  102  and that makes up a dipole antenna in conjunction with the first antenna element  104 ; a second antenna element  106  making up a monopole antenna placed in the lower housing  102  close to a hinge section  103 ; a first feed section  107  placed at one side end of the first antenna element  104 ; a second feed section  108  that is placed on one side end of the second antenna element  106  facing the first feed section  107  and that feeds electric power to the second antenna element  106  through unbalanced feeding; and a high frequency switch  109  that selects between the first antenna element  104  and the second antenna element  106 , as required, and makes a switch to the selected antenna element. In the drawing, the reference numeral  110  designates a matching circuit; the reference numeral  111  designates a radio circuit; the reference numeral  112  designates a switch control section; and  113  designates an open-close sensor. 
     By the way, the foldable portable phone requires setting of a high frequency switch, or the like; hence, a configuration of the phone becomes complicate correspondingly. In such a foldable portable phone, it is common to use the housing of the portable phone by hand. Therefore, it is desirable to place the antenna at a location where the antenna undergoes as little influence of hand as possible. Incidentally, in the foldable portable phone shown in  FIG. 9 , an electric current flowing through the lower housing is large; therefore, gain deterioration which will arise when the phone is used while gripped is great. 
     For this reason, a portable phone  200 , such as that shown in  FIG. 10 , has also been developed (see; for instance, Patent Document 2). Specifically, the portable phone  200  has an upper housing  201  accommodating a first circuit board  204 ; a second circuit board  205  to be electrically connected to the first circuit board  204  and that is joined to the upper housing  201  by way of a hinge section  203 ; an antenna element  206  incorporated in the upper housing  201 ; a feed section  207  that is placed on the first circuit board  204  and that is electrically connected to the antenna element  206 ; and a coaxial line path  208  that electrically connects the first circuit board  204  to the second circuit board  205 . In the drawing, the reference numeral  209  designates a radio circuit, and the reference numeral  210  designates an FPC (flexible cable). 
     Patent Document 1: JP-A-2004-229048 
     Patent Document 2: JP-A-2007-158915 
     DISCLOSURE OF THE INVENTION 
     Problem that the Invention is to Solve 
     However, a tendency, for placing an emphasis on a design at the time of purchase of a portable radio, such as a portable phone, has recently become stronger. In order to prevent impairment of the design of the portable phone, a desire for minimizing projection of an antenna out of housings has become stronger. Moreover, when an attempt is made to reduce; for instance, the thickness of a housing of a portable phone shown in  FIG. 10 , the antenna element  206  and the hinge section  203  get closer to each other, with the result that an antenna characteristic is degraded by coupling between the antenna element and the hinge section. Further, since a feed section is provided in an upper housing equipped with a display section that accounts for a large area of the housing, a footprint eventually increases. 
     In the portable phone shown in  FIG. 10 , the antenna element  206  is incorporated in the upper housing  201  that is little affected by hand; hence, occurrence of gain deterioration, which would otherwise arise when the portable phone is used by hand, can be avoided. Accordingly, the antenna element works in this respect. However, the antenna element operates as a monopole antenna while the upper housing  201  is taken as a ground. Hence, an electric current flowing through the upper housing  201  is large, and a vertical polarization component is greater than a horizontal polarization component. As a consequence, the horizontal polarization component accounts for the most part during communication, which can sometimes induce a drop in communication gain. 
     The present invention has been conceived in light of the circumstance and aims at providing a foldable portable radio that can exhibit high communication performance despite its slimness and compact housings. 
     Means for Solving the Problem 
     A portable radio of the present invention has a first housing in which a first circuit board is placed; a second housing in which a second circuit board is placed; a first hinge joining the first housing and the second housing to each other so as to be rotatable around one axis and having a conductivity; an antenna element that is placed in a vicinity of the first hinge and that is placed substantially parallel to an axial direction of the first hinge; and a feed section connected to a radio circuit on the first or second circuit board, wherein the first hinge and the antenna element operate as a dipole antenna as a result of the antenna element being electrically connected to the feed section and also the first hinge being connected as a ground. By means of the configuration, the first hinge is used as a ground. Hence, deterioration of an antenna characteristic attributable to a coupling between an antenna and a hinge can be ignored. An attempt can be made to correspondingly reduce the thickness of the housings. Since an electric current concentrates on the first hinge and the antenna element, gain deterioration can be diminished even when the portable radio is gripped by hand. Moreover, since the first hinge and the antenna element operate as a dipole, vertical polarization components become dominant during communication, and a high communication characteristic can be exhibited. 
     An overlap between the antenna element and the first hinge achieved in their longitudinal directions can also be set to about one-half or less of the length of the antenna element. By means of the configuration, electromagnetic coupling between the antenna element and the first hinge becomes small, and deterioration of a communication characteristic can be prevented. 
     The feed section may also be electrically connected to a radio circuit placed on the first or second circuit board by way of a coaxial line path, and an exterior conductor of the coaxial line path may electrically connect the first hinge to a ground of the first or second circuit board. Since the hinge can excite the antenna element by serving as a ground regardless of a location in which the radio circuit is placed, an attempt can be made to reduce the size and thickness of the portable radio while high communication performance is maintained. 
     A length of the coaxial line path is preferably about quarter of a wavelength corresponding to an operating frequency of the dipole antenna made up of the antenna element and the first hinge. It is thereby possible to prevent leakage of a signal from the coaxial line path to the first or second circuit board, and influence of the hand on communication can be diminished. 
     The portable radio can also be configured so as to further include an impedance matching circuit between the antenna element and the feed section, and a ground of the impedance matching circuit and the first hinge may also be electrically connected together. Since there is no necessity for providing an additional ground, an attempt can be made to decrease the size and thickness of the portable radio. 
     The portable radio of the present invention further includes at least one of a first filter and a second filter that sections a resonance frequency of the dipole antenna made up of the antenna element and the first hinge, and the first filter may be placed on the first circuit board and has one end electrically connected to the antenna element and a remaining end electrically connected to a ground of the first circuit board; and the second filter may be placed on the second circuit board and has one end electrically connected to the first hinge and a remaining end electrically connected to a ground of the second circuit board. As a result, it becomes possible to build a dipole antenna having two different operating frequencies of the first dipole antenna made up of the antenna element and the hinge and the second dipole antenna made up of the first and second circuit boards. A multi-band antenna having two frequencies can be accomplished without addition of antenna components. 
     The portable radio can also be configured so as to further include a second conductive hinge that joins the first housing to the second housing so as to be rotatable around a remaining axis orthogonal to the one axis. As a result, an attempt can be made to reduce the size and thickness of a portable radio that is open-able and closable in both the longitudinal and lateral directions. 
     The portable radio can also be configured so as to further include at least one of a first reactance element having one end electrically connected to the first hinge and a remaining end electrically connected to the second hinge; a second reactance element having one end electrically connected to the first hinge and a remaining end electrically connected to the ground of the first circuit board or the second circuit board; and a third reactance element having one end electrically connected to the second hinge and a remaining end electrically connected to the ground of the first or second circuit board. As a result, it becomes possible to prevent deterioration of an antenna characteristic, which would otherwise be caused by coupling between the hinge and the antenna element. 
     ADVANTAGE OF THE INVENTION 
     A portable radio of the present invention includes a first housing in which a first circuit board is placed; a second housing in which a second circuit board is placed; a first conductive hinge that joins the first housing and the second housing to each other so as to be rotatable around one axis; an antenna element that is placed in a vicinity of the first hinge and that is placed substantially parallel to an axial direction of the first hinge; and a feed section connected to a radio circuit on the first or second circuit board, wherein the first hinge and the antenna element operate as a dipole antenna as a result of the antenna element being electrically connected to the feed section and also the first hinge being connected as a ground. The portable radio can exhibit high communication performance despite its slimness and compact housings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing a foldable portable phone of a first embodiment of the present invention. 
         FIG. 2  is an oblique perspective view showing a configuration of a first hinge of the present invention. 
         FIG. 3  is a general oblique perspective view showing the configuration of the hinge of the first embodiment of the present invention. 
         FIG. 4  is a front view showing a foldable portable phone of a second embodiment of the present invention. 
         FIGS. 5  (A) and (B) are a front view and a side view showing a state of a biaxial foldable portable phone of a third embodiment of the present invention when the phone is opened in its longitudinal direction. 
         FIGS. 6  (A) and (B) are a front view and a side view showing a state of the biaxial foldable portable phone of the third embodiment of the present invention when the phone is opened in its lateral direction. 
         FIGS. 7  (A) is an oblique perspective view showing a configuration of a second hinge of the third embodiment of the present invention, and (B) is an oblique perspective view showing a turning state of the hinge. 
         FIG. 8  is a front view showing a foldable portable phone of a fourth embodiment of the present invention. 
         FIGS. 9  (A) and (B) are a plan view and a side view showing a configuration of a related art foldable portable phone. 
         FIG. 10  is a plan view showing a configuration of another related art foldable portable phone. 
     
    
    
     DESCRIPTIONS OF THE REFERENCE NUMERALS AND SYMBOLS 
     
         
         
           
               10 ,  20 ,  30 ,  40  FOLDABLE PORTABLE PHONE 
               11  UPPER HOUSING (FIRST HOUSING) 
               11 A FIRST CIRCUIT BOARD (UPPER CIRCUIT BOARD) 
               12  LOWER HOUSING (SECOND HOUSING) 
               12 A SECOND CIRCUIT BOARD (LOWER CIRCUIT BOARD) 
               13  HINGE 
               13 A HINGE ELEMENT (FIRST HINGE: FIRST HINGE ELEMENT) 
               13 B HINGE ELEMENT (SECOND HINGE: SECOND HINGE ELEMENT) 
               133 A GROUND 
               14  ANTENNA ELEMENT 
               15  FEED SECTION 
               16  IMPEDANCE MATCHING SECTION 
               17  RADIO CIRCUIT 
               21  UPPER FILTER 
               22  LOWER FILTER 
               41  FIRST REACTANCE ELEMENT 
               42  SECOND REACTANCE ELEMENT 
               43  THIRD REACTANCE ELEMENT 
           
         
       
    
     BEST MODES FOR IMPLEMENTING THE INVENTION 
     Preferred embodiments of the present invention are hereunder described in detail by reference to the drawings. 
     First Embodiment 
       FIG. 1  shows a foldable portable phone  10  of a first embodiment of a portable radio of the present invention. The foldable radio  10  has an upper housing  11  making up a first housing; a lower housing  12  making up a second housing; a hinge  13  that joints the upper housing  11  to the lower housing  12  in a rotatable manner; an antenna element  14 ; a feed section  15 ; an impedance matching circuit  16 ; a radio circuit  17 ; and a coaxial line path  18 . 
     The upper housing  11  has an un-illustrated display section and a first circuit board (an upper circuit board)  11 A. The lower housing  12  has an un-illustrated operation section, a second circuit board (a lower circuit board)  12 A, and the foregoing radio circuit  17 . 
     The hinge  13  has a hinge element  13 A making up the first hinge, the foregoing antenna element (a first antenna element)  14 , the feed section  15 , and the impedance matching circuit  16 . In particular, details of the hinge  13  of the present embodiment are described later. The antenna element  14 , the feed section  15 , the impedance matching section  16 , a ground  134 , a spring connector  134 C, and the like, are placed on a substrate (a flexible printed board)  133  that is positioned along a direction of a rotary shaft of the hinge  13  and that assumes a substantially rectangular shape. 
     As shown in  FIG. 2 , the hinge element  13 A includes a hinge fixing section  131  and a hinge turning section  132  that is attached to the hinge fixing section  131  in a rotatable manner. Both the hinge fixing section and the hinge turning section are made of a conductive material. The hinge fixing section  131  is fixed to the lower housing  12 , and the hinge turning section  132  is fixed to the upper housing. 
     As shown in  FIG. 3 , the ground  134  is made of a conductor (e.g. copper foil) placed on the substrate  133 . A coaxial line path fixing section  134 A and a spring connector fixing section  134 B that each are formed from a conductive material are fixed to the ground  134 . The coaxial line path fixing section  134 A and the spring connector fixing section  134 B are electrically connected to each other by way of the ground  134 . 
     One end of the coaxial line path  18  is fixed to the coaxial line path fixing section  134 A, whereby a desired degree of strength is assured. A base end of the spring connector  134 C is fixed to the spring connector fixing section  134 B. The spring connector  134 C makes an electrical connection with the hinge element  13 A while maintaining a state of being rotatable with respect to the hinge turning section  132 . Therefore, a ground of the lower circuit board  12 A is electrically connected to the hinge element  13 A. The antenna element  14  is electrically connected to the radio circuit  17  by way of the impedance matching circuit  16  on the substrate  133 , the feed section  15 , and an interior conductor in the coaxial line path  18 . 
     The feed section  15  is in the hinge  13  and electrically connected to the radio circuit  17  placed on the second circuit board by way of the interior conductor in the coaxial line path. 
     The impedance matching circuit  16  attempts to achieve impedance matching between the antenna element  14  and the interior conductor in the coaxial line path. 
     As mentioned previously, the antenna element  14  and the hinge element  13 A are electrically connected together by way of the impedance matching circuit  16 . Specifically, the antenna element  14  and the hinge element  13 A make up a dipole antenna. A desirable length of the coaxial line path  18  is made, in consideration of prevention of leakage of a radio wave into the second circuit board, so as to come to about a quarter of a wavelength λ 1  corresponding to an operating frequency (f 1 ) of the dipole antenna (a first dipole antenna) made up of the antenna element  14  and the hinge element  13 A. 
     Although un-illustrated, a mesh-shaped exterior conductor and an interior conductor made of a wire; for instance, are provided in the coaxial line path  18 . One end of the exterior conductor of the coaxial line path  18  is secured to a conductive coaxial line path fixing section  134 A, and the other end of the exterior conductor is connected to the ground of the lower circuit board  12 A. Specifically, the ground  134  is connected to the ground of the lower circuit board  12 A by way of the exterior conductor. 
     One end of the interior conductor of the coaxial line path  18  is connected to the antenna element  14  by way of the impedance matching circuit  16  and the other end of the interior conductor of the coaxial line path  18  is connected to the radio circuit  17 . As a consequence, the antenna element  14  and the hinge element  13 A are electrically connected to the wireless circuit  17  by way of the impedance matching circuit  16 . 
     Accordingly, the antenna element  14  and the hinge element  13 A that make up the antenna are placed on the hinge  13 . Antenna space does not need to be provided in the upper housing  11  and the lower housing  12 . Therefore, it is possible to realize compact housings, and the antenna portion does not need to project out of the housings. Hence, it is possible to prevent impairment of appearance of the portable radio. 
     According to the present embodiment, the hinge is used as a ground of the antenna element. Therefore, deterioration of a characteristic attributable to coupling between the hinge and the antenna element can be ignored. A configuration for assuring a minimum distance between the upper housing  11 , the lower housing  12  and the hinge  13 , such as that hitherto been required, becomes obviated; hence, the thickness of the housings can be reduced. 
     Further, according to the present embodiment, an electric current concentrates on the antenna element and the hinge. Accordingly, gain deterioration, which would otherwise be caused when the lower housing is gripped by hand, can be avoided. Because of operation of the dipole antenna made up of the antenna element and the hinge element  13 A, the vertical polarization component can be increased during communication, and a communication characteristic becomes better. 
     In the present embodiment, the hinge is placed so as to turn in the longitudinal direction of the housings. However, even when the hinge is arranged so as to turn in a widthwise direction of the housings, a similar advantage can be yielded. 
     An overlap between the antenna element  14  and the first hinge element  13 A in their longitudinal directions may be set to about one-half or less of the length of the antenna element  14 . By means of the configuration, electromagnetic coupling between the antenna element and the first hinge becomes smaller, and deterioration of the communication characteristic can be prevented. 
     Second Embodiment 
     A second embodiment of the present invention is now described in detail by reference to  FIG. 4 . In the present embodiment, the elements that are identical with those of the portable phone described in connection with the first embodiment are assigned the same reference numerals, and their repeated explanations are omitted. 
     A foldable portable phone  20  of the present embodiment differs from the foldable portable phone of the first embodiment in that the phone has an upper filter  21  and a lower filter  22 . 
     The antenna element  14  and the upper circuit board  11 A are electrically connected to each other by way of the upper filter  21 . The upper filter  21  hinders flow of, to the upper circuit board  11 A, a high frequency current having an operating frequency f 1  (a first frequency) of the first dipole antenna made up of the antenna element  14  and the hinge element  13 A of the first embodiment. 
     The hinge element  13 A and the lower circuit board  12 A are electrically connected to each other by way of the lower filter  22 . As does the upper filter  21 , the lower filter  22  hinders flow of the high frequency current having the operating frequency f 1  from the hinge element  13  to the lower circuit board  12 A. 
     In the present embodiment, two filters having an identical configuration; namely, the upper filter  21  and the lower filter  22 , are placed. However, there may also be adopted a configuration in which only one of the filters is placed. The configuration of the filters is assumed to encompass an LC parallel resonance circuit, an LC serial resonance circuit, and the like. 
     In the embodiment, the antenna element  14 , the upper circuit board  11 A and the hinge element  13 A, the lower circuit board  12 A act as a second dipole antenna. An electrical length of the second dipole antenna (made up of the antenna element  15  and the hinge element  13 A of the first embodiment) is longer than an electrical length of the first dipole antenna, and an operating frequency f 2  of the second dipole antenna is lower than the operating frequency f 1  of the first dipole antenna (f 2 &lt;f 1 ). 
     Therefore, according to the present embodiment, there can be configured multi-band slim housings that cover two frequency bands. Further, a multi-band configuration can be realized by merely setting one antenna element. Therefore, cost reduction can also be accomplished. 
     Third Embodiment 
     A third embodiment of the present invention is now described in detail by reference to  FIGS. 5 and 6 . In the embodiment, the elements that are identical with those of the portable phone described in connection with the first embodiment are assigned the same reference numerals, and their repeated explanations are omitted. 
     Unlike the foldable portable phones described in connection with the first and second embodiments, a foldable portable phone  30  of the present embodiment works as a biaxial foldable portable phone in which the upper housing  11  and the lower housing  12  are open-able and closable in the horizontal direction (a lateral direction) shown in  FIG. 6  as well as in the vertical direction (a longitudinal direction) shown in  FIG. 5 . 
     Accordingly, the foldable portable phone  30  of the present embodiment has the upper housing  11 , the lower housing  12 , the hinge  13 , the feed section  15 , the impedance matching circuit  16 , the radio circuit  17 , the antenna element  14 , a longitudinal opening hinge element (hereinafter called a “first hinge element”)  13 A, and also a hinge element (hereinafter called a “second hinge element”)  13 B making up a lateral opening second hinge. 
     As shown in  FIG. 7 , the second hinge element  13 B has a hinge fixing section  135  and a hinge turning section  136  that can laterally turn around a rotary shaft  137  with respect to the hinge fixing section  135 . The hinge fixing section  135  is fixed to the hinge  13 , and the hinge turning section  136  is fixed to the upper housing  11 . At this time, the hinge  13 B and the upper housing  11  may be electrically connected or unconnected. The rotary shaft  137  makes up a shaft that lets the upper housing and the lower housing turn in a direction orthogonal to the rotary shaft of the hinge element  13 A, and joins the hinge fixing section  135  to the hinge turning section  136  in a rotatable manner. All of the hinge fixing section  135 , the rotary shaft  137 , and the hinge turning section  136  are formed from a conductive material. 
     The present embodiment differs from the first and second embodiments in that the second hinge element  13 B is used as an antenna ground and that the second hinge element  13 B and the lower circuit board  12 A are electrically connected to each other by way of the exterior conductor of the coaxial line path  18 . The antenna element  14  is electrically connected to the radio circuit  17  by way of the impedance matching circuit  16 , the feed section  15 , and the interior conductor of the coaxial line path  18 . 
     The antenna element  14  and the second hinge element  13 B thereby make up a dipole antenna. Like the first embodiment, the coaxial line path  18  is formed so as to have a length of about a quarter of a wavelength corresponding to the operating frequency of the dipole antenna made up of the antenna element  14  and the second hinge element  13 B. 
     By adoption of the configuration, the antenna element  14  and the matching circuit  16 , which make up the antenna, can be placed in the hinge  13  in the third embodiment having a biaxial hinge configuration. A necessity for placing an antenna in the upper and lower housings becomes obviated, and hence miniaturization of the portable phone becomes possible. 
     In any of states of the housings shown in  FIGS. 5 and 6 , the dipole antenna can be configured in the hinge  13 , and superior antenna performance can be accomplished. 
     Fourth Embodiment 
     A fourth embodiment of the present invention is now described in detail by reference to  FIG. 8 . Even in the present embodiment, the elements that are identical with the elements of the portable phones described in connection with the first and third embodiments are assigned the same reference numerals, and their repeated explanations are omitted. 
     Unlike the foldable portable phone  30  described in connection with the third embodiment, a foldable portable phone  40  of the present embodiment has a first reactance element  41 , a second reactance element  42 , and a third reactance element  43 . In the embodiment, not all of the reactance elements are always required, any one or two of them may also be employed. 
     The first reactance element  41  is inserted between the hinge element  13 A and the second hinge element  13 B, and the second reactance element  42  is inserted between the hinge element  13 A and the lower circuit board  12 A. As a result of insertion of the reactance elements, it is possible to prevent performance deterioration, which would otherwise be caused by electromagnetic field coupling between the hinge element  13 A and the dipole antenna made up of the antenna element  14  and the second hinge element  13 B. 
     The third reactance element  43  is inserted between the second hinge element  13 B and the upper circuit board  11 A. It thereby becomes possible to prevent performance deterioration, which would otherwise be caused by electromagnetic field coupling between the hinge and a signal cable (not shown) that connects the upper circuit board  11 A to the lower circuit board  12 A. 
     Therefore, in the present embodiment, the biaxial foldable portable phone can prevent deterioration of an antenna characteristic, which would otherwise be caused by electromagnetic field coupling between the hinge and the signal cable connecting the upper and lower circuit boards together. Further, an attempt can also be made to reduce the thickness of the housings. 
     The present invention is not particularly limited to the embodiments and can be implemented in various forms to such an extent that it does not depart the gist of the invention. 
     Although the present invention has been described in detail by reference to the specific embodiments, it is manifest to the persons who are skilled in the art that the present invention be susceptible to various alterations or modifications without departing the spirit and scope of the present invention. 
     The present patent application is based on Japanese Patent Application No. 2008-127113 filed on May 14, 2008, the entire subject matter of which is incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The portable phone of the present invention yields an advantage of the ability to exhibit high communication performance despite its slimness and compact housings and is useful for; for instance, a foldable portable phone.