Patent Publication Number: US-6985112-B2

Title: Antenna

Description:
FIELD OF THE INVENTION 
   The present invention relates to an antenna used for a wireless device for mobile communications such as a handy telephone. 
   BACKGROUND ART 
   Recently, wireless devices for mobile communications including a handy telephone have been getting smaller and more multi-functional. Accordingly, as an antenna to be mounted on such a compact device, a built-in type has become popular. 
   Here will be described a conventional built-in type antenna with reference to  FIG. 10  and  FIG. 11 .  FIG. 10  is a perspective view showing the appearance of a conventional antenna. Insulating resin-made core  1  has body  1 A generally shaped into a rectangular parallelepiped. Three projections  1 C, which project from each periphery of three corners of body  1 A, are disposed in parallel with each other. Each of projections  1 C has hole  1 B therein. 
   Antenna element  2 , which is made of a metallic thin plate, is calked on the upper side of core  1  with projections  1 D disposed on the upper surface of body  1 A of core  1 . 
   Antenna element  2  contains feeding terminal  2 A. Feeding terminal  2 A projects in a slanting-down direction from a periphery of the corner having no projection  1 C of core  1 . Conventional antenna  3  is structured above. 
     FIG. 11  shows how antenna  3  is mounted on a wireless device—specifically, shows the state previous to be accommodated in case  4  of a wireless device for mobile communications. 
   Antenna  3  is placed in a space adjacent to wiring board  5  in case  4 , using three wood screws  6  each of which is through hole  1 B of projection  1 C and boss  4 A of case  4  corresponding to each projection  1 C. 
   Wiring board  5  includes communications circuit  5 B located in area  5 C shown by the dash lines in  FIG. 11 . The explanation of the components (not shown) of circuit  5 B is omitted. When antenna  3  is fixed in case  4 , the tip of feeding terminal  2 A integrally formed with antenna element  2  has a tight contact with feeding section  5 A (which is further connected with communications circuit  5 B) of wiring board  5 . With the structure, an operation performed by circuit  5 B establishes wireless communications via antenna  3 . 
   References relating to the prior-art technology described above are introduced in, for example, Japanese Patent Non-examined Publications No. H11-163613 and H10-13287. 
   A prior art antenna, as described above, is mounted on a wireless device by wood screws  6 , which inconveniently decreases mounting efficiencies and increases production costs. Furthermore, due to the structure in which feeding terminal  2 A makes a tight contact with feeding section  5 A of wiring board  5 , the prior-art antenna cannot ensure stability in electrical connections when an impact load is applied thereto. It has been a pending problem to be improved. 
   SUMMARY OF THE INVENTION 
   The present invention addresses the problem above. It is therefore the object of the present invention to provide an antenna that offers not only an easy mounting on a wireless device, but also higher reliability in electrical connections. 
   To achieve the object above, the antenna of the invention is formed of i) a rod-like core made of insulating resin, and ii) an antenna element containing a feeding terminal secured to the core. Such structured antenna is mounted on a wireless device in such a way that the core is fitted in a notch formed in a wiring board of the wireless device and then the feeding terminal is soldered onto the wiring board of the device. Fitting the core into the notch of the wiring board allows the antenna to be properly positioned with respect to the wiring board. Besides, the feeding terminal can be soldered, as well as other components, in the same step. This contributes to decreased manufacturing cost. Furthermore, such mounted antenna can maintain secure connections with the wiring board of the wireless device, thereby ensuring electrical connections with reliability and mechanical strength against impact load from the outside. 
   It is another aspect of the present invention that i) the core is generally shaped into a rectangular parallelepiped, and ii) a joint section for soldering is disposed on side surfaces of the core other than the side surface on which the feeding terminal of the antenna element is provided. The core can be easily manufactured because of its simple shape. In addition, the antenna is soldered, through two or more positions on the side surfaces of the core, to the wiring board. This can provide a further steady mounting, which is resistant to impact load from the outside. 
   It is still another aspect of the present invention that the feeding terminal and the joint section are located substantially at the midpoint of a side surface of the core in the height direction. That is, the antenna is soldered to the wiring board of a wireless device so that the thickness of the core is evenly divided on the upper side and the lower side of the wiring board. Such a positioning provides, for example, spaces on the lower side of the wiring board for an effective use. In other words, the structure increases dimensional flexibility in the thickness direction of the wireless device. 
   It is yet another aspect of the present invention that the core is force-fitted into the notch of the wiring board. With the structure, the antenna can be retained in a stable condition, although in temporary assembly until the core is soldered onto the wiring board, without worry about being come off the wiring board. The structure provides an easy handling of the wiring board during transportation. 
   It is another aspect of the present invention that the core of the antenna contains projections that downwardly extend under the wiring board on which the antenna is mounted. Fixing the projections to the wiring board by calking allows the antenna to be retained in temporary assembly until the core is soldered onto the wiring board. Therefore, the efficiency of mounting procedures is improved. 
   It is still another aspect of the present invention that the core contains a pedestal under the side surface on which the feeding terminal is disposed, and the gap between the tip of the feeding terminal and the principle plane of the pedestal is determined so as to be slightly smaller than the thickness of the wiring board. With the wiring board being clipped between the tip of the feeding terminal and the pedestal, the antenna can keep the right position until the core is soldered to the wiring board. If the wiring board with the antenna in temporary assembly (before soldering) had to be transported, the structure would minimize inconveniencies, for example, coming-off or being out of the right position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the appearance of an antenna in accordance with an embodiment of the present invention. 
       FIG. 2  is a side view of the antenna shown in  FIG. 1 . 
       FIG. 3  is a side view depicting how the antenna element is disposed. 
       FIG. 4  is a perspective view illustrating how to mount the antenna on a wiring board of a wireless device. 
       FIG. 5  is a perspective view illustrating the antenna mounted on the wiring board of the wireless device. 
       FIG. 6  is a side view illustrating the antenna mounted on the wiring board of the wireless device. 
       FIG. 7  is a perspective view illustrating the antenna mounted on the wiring board of the wireless device. 
       FIG. 8  is a perspective view illustrating how to mount an antenna having another structure on a wiring board. 
       FIG. 9  is a perspective view illustrating how to mount an antenna having still another structure on a wiring board. 
       FIG. 10  is a perspective view showing the appearance of a prior-art antenna. 
       FIG. 11  illustrates how to mount the prior-art antenna on a wireless device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of the present invention is described hereinafter with reference to the accompanying drawings,  FIG. 1  through  FIG. 8 . 
   Exemplary Embodiment 
     FIG. 1  is a perspective view showing the appearance of an antenna in accordance with an embodiment of the present invention, and  FIG. 2  is a side view of the antenna shown in  FIG. 1 . Insulating resin-made core  11 , which is generally formed into a rectangular parallelepiped, contains two caulking projections  11 A on upper surface  11 F. 
   Antenna element  12 , which is a metallic thin plate, is formed into U shape in section through blanking and bending processes. 
   Antenna element  12  is disposed on core  11  in such a way that the U shape conforms to top surface  11 F, side surface  11 B, and bottom surface  11 G, and then secured to core  11  by caulking at caulking projections  11 A on top surface  11 F and a caulking projection (not shown) disposed at the edge of bottom surface  11 G. 
   Antenna element  12  contains an element section on lengthwise side surface  11 B of core  11 , top surface  11 F, and bottom surface  11 G. 
   The element section of antenna element  12  on top surface  11 F of core  11  contains L-shaped feeding terminal  12 A. Climbing down along lengthwise side surface  11 D toward bottom surface  11 G, feeding terminal  12 A is bent substantially at the midpoint of height H 0  of side surface  11 D (i.e., H0/2) to form tip  12 B. 
   Antenna element  12  also contains L-shaped joint sections  12 C, each of which downwardly extends along side surfaces  11 D,  11 C,  11 E, respectively, toward bottom surface  11 G. Like feeding element  12 A, each of joint sections  12 C is bent at the same level of tip  12 B of feeding terminal  12 A—approximately at H0/2—to form tip  12 D of the L shape. 
     FIG. 2  shows the state in which antenna element  12  is attached to core  11 .  FIG. 2  is a side view of the same structure shown in  FIG. 1 , detail explanations on the components will therefore be omitted. As described above, tip  12 B of feeding terminal  12 A and tips  12 D of joint sections  12 C are bent substantially at the midpoint of height H 0  of side surface  11 D (i.e., H0/2) to form the L shape. 
     FIG. 3  shows the state in which the upper section of antenna element  12  is fixed by caulking. That is, after temporarily fixed to core  11 , antenna element  12  is bent into an L shape, and caulking holes of antenna element  12  fit onto caulking projections  11 A disposed on top surface  11 F of core  11 . Projections  11 A are then crashed to complete caulking. To reach the state shown in  FIG. 2 , steps to be followed are: bending lower section  12 E of antenna element  12  in the direction of arrow  11 J, i.e., to bottom surface  11 G; caulking the end of lower section  12 E by crashing projection  11 H formed at the edge of bottom surface  11 G. Lower section  12 E is thus secured to core  11 . 
   Now will be described the mounting process of such structured antenna  13  onto, for example, a wireless device for mobile communications with reference to the drawings. 
     FIG. 4  is a perspective view illustrating how to mount the antenna on a wiring board of a wireless device (not shown). Wiring board  14  of  FIG. 4  contains notch  14 A so as to conform the rectangular side of core  11 . 
   Like a wiring board employed for the prior-art structure, wiring board  14  contains communications circuit  14 B in area  5 C (indicated by the dash lines). The explanation of the components (not shown) of circuit  14 B is omitted. 
   For feeding power to antenna  13 , feeder  14 C extends from communications circuit  14 B to notch  14 A. In addition, fixed lands  14 D are disposed at positions corresponding to each joint section  12 C of antenna  13 . Fixed lands  14 D can be soldered, and electrically independent with each other. 
   To mount antenna  13  on wiring board  14 , firstly, core  11  of antenna  13  is fitted into notch  14  so that feeding terminal  12 A meets with feeder  14 C, and three joint sections  12 C meet with corresponding fixed lands  14 D. 
     FIG. 5  shows antenna  13  mounted on wiring board  14 , as well as other components (not shown), by dip soldering or reflow soldering. Antenna  13  is thus securely mounted onto wiring board  14 . 
   According to the embodiment, core  11  of antenna  13  is generally shaped into a rectangular parallelepiped. By virtue of the simple shape, core  11  can be manufactured with ease. Similarly, notch  14 A of wiring board  14  for accepting antenna  13  is shaped relatively simple. The simple structure contributes to an easy processing and minimized space between antenna  13  and notch  14 A. 
   In the structure of the embodiment, side surface  11 D of core  11  contains feeding terminal  12 A, while side surface  11 C and side surface  11 E opposite to surface  11 C contain each joint section  12 C. That is, with the three joint sections disposed on the surfaces of core  11 , antenna  13  can be held in a stable condition, although in temporary assembly until being soldered. Therefore, if wiring board  14  with antenna  13  before soldering had to be transported, the structure would minimize inconveniencies, for example, coming-off or being out of the right position. 
   As described above, core  11  has a snug fit with notch  14 A. After soldering, antenna  13  is securely mounted on wiring board  14  through feeding terminal  12 A of antenna element  12  and joint sections  12 C disposed on side surfaces  11 C and  11 D, whereby a firm attachment is obtained. If a perceptible impact load is applied to the wireless device caused by an accidental fall, electrical connections between antenna element  12  and communications circuit  14 B can be maintained with stability. 
     FIG. 6  is a side view illustrating antenna  13  mounted on wiring board  14 . As shown in the figure, tip  12 B of feeding terminal  12  and each of tips  12 D of joint sections  12 C are located substantially at the midpoint of height H 0  of core  11  in the height direction. In other words, the thickness of core  11  is evenly divided, through wiring board  14 , in the upwardly stand-out portion (H 1 ) and the downwardly stand-out portion (H 2 ). Such a positioning provides space  14 S for an effective use on the lower side of wiring board  14 . At the same time, the structure increases dimensional flexibility in the thickness direction of the wireless device. 
   To set the antenna to desirable frequency bands, the position of feeding terminal  12 A electrically connected to circuit  14 B of wiring board  14  can be replaced with any one of positions of joint sections  12 C. Such positional setting can be determined according to the size or shape of communications circuit  14 B mounted of wiring board  14 . The structure with design flexibility is an advantage of the present invention. 
     FIG. 7  is a perspective view illustrating the antenna mounted on the wiring board of the wireless device. The element section of antenna element  12  is positioned on top surface  11 F, bottom surface  11 G, and lengthwise side surface  11 B—the surface most distant from circuit  14 B—of core  11 . The height of antenna  12  from the upper surface of wiring board  14  (indicated by H 1  in  FIG. 6 ) measures approximately one half of H 0  —the whole height of antenna element  12 . Antenna  13  contains the other half the thickness on the lower surface of wiring board  14 . The structure provides good antenna characteristics without degradation of the performance. 
   Although antenna element  12  in the description above is fixed to core  11  by calking, it is not limited thereto; antenna element  12  can be formed by insert molding. In this case, soldering joint piece (not shown), which is separated from antenna element  12 , is embedded with core  11  so as to serve a joint section between antenna element  12  and core  11 . 
   Core  11  of antenna  13  and notch  14  of wiring board  14  are so designed that core  11  can be force-fitted into notch  14 . Although still in a temporary assembly, antenna  13  and wiring board  14  can be kept in a stable condition until being soldered together. Such stableness provides wiring board  14  with an easy handling during transportation. 
   According to the structure shown in  FIG. 8 , core  16  of antenna  15 , which is generally shaped into a rectangular parallelepiped, contains small projections  16 A. Projections  16 A are formed each at both corners of the lengthwise surface on which feeding terminal  17 A is disposed. Core  16  is attached to wiring board  18 , with small projections  16 A downwardly extended. On the other hand, wiring board  18  contains two corner-notches  19  at the inside corners of notch  18  so as to correspond to small projections  16 A. 
   With such a structure, when core  16  of antenna  15  is fitted into notch  18 A of wiring board  18 , small projections  16 A downwardly extend through corner-notches  19 . Caulking by crashing small projections  16 A allows antenna  15  to be temporarily but stably fixed to wiring board  18 , thereby providing more stable attachment between the antenna and the wiring board until being soldered each other. 
   Such stableness can protect antenna  15  from coming apart from wiring board  18  even if the wiring board is turned upside down: efficiencies in mounting work is greatly improved. 
   Although small projections  16 A are positioned each at both corners of the lengthwise surface of core  16  in  FIG. 8 , the positioning is not limited by the shape or the location of core  16 ; small projections  16 A can be disposed at anywhere as long as the positioning is effective in caulking until antenna  15  is soldered to wiring board  18 . 
   According to the structure shown in  FIG. 9 , antenna  20  contains core  21  generally formed into a rectangular parallelepiped. Mounted on a principal plane of pedestal  21 B, core  21  contains side surfaces  21 A,  21 C, and  21 D. Surface  21 A contains feeding terminal  22 A and joint section  22 C. On the other hand, surfaces  21 C and  21 D contains respective joint section  22 C. Feeding terminal  22 A and each joint section  22 C extend toward the principal plane of pedestal  22 B but have no contact with the plane; feeding terminal  22 A and each joint section  22  are bent, at a distance (indicated by t 0  in  FIG. 9 ) from the principal plane, into an L-shape to form tip  22 B and tip  22 D, respectively. That is, Tips  22 B and  22 D face the principal plane of pedestal  21 B, keeping gap to therebetween. 
   On the other hand, wiring board  14  is so designed that its thickness t1 is slightly larger than the gap t 0 . Antenna  20  is moved in the direction indicated by arrow Q and fitted into notch  14 A of wiring board  14 . The dimensional setting of t 1 &gt;t 0  allows the gap t 0  to bite the thickness t 1 , thereby antenna  20  can be firmly attached to wiring board  14 . If wiring board  14  and antenna  20  in the temporary assembly (i.e., before soldering) is moved, the firm connection can protect antenna  20  from coming off or having a wrong position. 
   To complete the mounting, tip  22 B of feeding terminal  22 A is soldered to feeding section  14 . Similarly, tips  22 D of joint sections  22 C are soldered to corresponding fixed land  14 . 
   The antenna of the present invention, as described above, is tightly fitted into the notch of the wiring board and then secured to the wiring board by soldering at the feeding terminal and the joint sections. The antenna can be mounted onto the wiring board with ease, i.e., the efficiency of mounting procedures is improved. Besides, the steady mounting condition ensures electrical connection with reliability and mechanical strength against impact load from the outside. It will be understood that the antenna of the present invention has a great value in industrial use.