PATENT ABSTRACT
An electronic device which includes a radio wave impermeably cylindrical case, a radio wave permeable cover covering an opening in one end of the case, a radio wave impermeable cover covering an opening in the other end of the case, and a circuit board and an antenna, both arranged between the two covers in the inner space. The antenna is connected to the board and includes an elongated core and a coil wound around an intermediate portion of the core. Magnetic flux introducing portions are provided on both end portions of the core, a radio wave permeable partition plate is arranged between the permeable cover and the antenna in the inner space, and a pair of flat and magnetic members are arranged between the partition plate and the antenna in the inner space and are magnetically connected to the flux introducing portions.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a Continuation application of U.S. application Ser. No. 11/238,034 filed Sep. 28, 2005 now U.S. Pat. No. 7,355,556, which is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2004-287860, filed Sep. 30, 2004; No. 2004-300205, filed Oct. 14, 2004; No. 2005-153916, filed May 26, 2005; and No. 2005-155213, filed May 27, 2005, the entire contents of all of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an antenna and an electronic device which receive radio waves. 
   2. Description of the Related Art 
   A radio-wave clock is known as an electronic device which receives a radio wave (hereinafter referred to as the “standard radio wave”) carrying a standard time signal thereon with a built-in antenna and which analyzes time information by a standard radio-wave signal inside the electronic device to correct present timing and precisely keep time. Moreover, as the radio-wave clock which receives such standard radio wave, an electronic watch has broadly spread which automatically receives a standard time radio wave to correct the time. 
   The antenna for receiving the standard radio wave comprises a magnetic core and a coil wound around this core. Moreover, when a magnetic flux (hereinafter referred to as the “signal magnetic flux”) by a magnetic field (hereinafter referred to as the “signal magnetic field”) produced by the standard radio wave is passed through this coil, a current is generated in the coil to receive the standard radio wave. 
   As the antenna which is disposed in such electronic watch to receive the radio wave, an antenna is known which is configured by winding the coil around the core formed of a magnetic material having a satisfactory receiving sensitivity, such as ferrite or amorphous metal. 
   Especially, the antenna using the amorphous metal as the core is superior to that configured by the ferrite material in impact resistance and temperature characteristic, and has been noted in recent years. 
   As the antenna of the amorphous metal, an antenna has heretofore been known in which a plurality of thin films of amorphous metals are laminated. 
   However, since such antenna using the amorphous metal is formed by laminating a plurality of thin films of amorphous metals, it is technically difficult and it requires much cost to work a shape of the core into an arbitrary three-dimensional shape, and manufacture the antenna adapted to a purpose. 
   It is also known that metals are used in a case, a back lid, and a dial plate of a portable electronic device such as a watch. However, when the metal is used in the case or the like of the electronic device including the built-in antenna, the metal interrupts the radio wave, and the built-in antenna cannot sufficiently receive the radio wave. 
   To solve the problem, it is known that although the metals are used in the case and the back lid, any metal is not used in the dial plate so that the built-in antenna can receive the radio wave through the dial plate. 
   However, in such antenna, since a portion of the antenna capable of receiving the radio wave is limited, the radio wave cannot be sufficiently received on a side of the dial plate, 
   Moreover, when the antenna is enlarged in order to obtain a satisfactory receiving sensitivity, restrictions are imposed on a mounting space in which another component is to be disposed, and it is difficult to miniaturize the device. 
   Furthermore, the receiving sensitivity of the standard radio wave by the antenna needs to be raised in order to receive the signal carrying the standard time signal thereon securely. Therefore, an antenna is known in which sectional areas of opposite end portions of the core are enlarged so that more signal magnetic fluxes can pass through the coil in order to raise the receiving sensitivity. 
   However, in this case, when the signal magnetic flux passes through the coil of the antenna, the current flows through the coil in a direction in which the signal magnetic fluxes are inhibited from being changed, and a magnetic flux (hereinafter referred to as the “generated magnetic flux”) directed in reverse to the signal magnetic flux is generated by the current. When the generated magnetic flux passes through a metal member positioned in the vicinity of the antenna, a current called an eddy current flows in the form of a concentric circle forming right angles with respect to the magnetic flux. It is known that when the eddy current is generated in the metal member, heat is released by an electric resistance owned by the metal material, and energy is lost. Therefore, the energy is consumed as a heat loss by the eddy current generated in the case of the device when the signal magnetic flux passes through the coil, and the receiving sensitivity of the antenna drops. 
   BRIEF SUMMARY OF THE INVENTION 
   An electronic device is provided which comprises: a cylindrical case which has an inner space and both ends opened to the inner space and which is impermeable to a radio wave; a first cover which covers an opening in one end of the case and which is permeable to the radio wave; a second cover which covers an opening in the other end of the case and which is impermeable to the radio wave; a circuit board which is arranged between the first cover and the second cover in the inner space of the case; an antenna which is arranged between the first cover and the second cover in the inner space of the case, which is connected to the circuit board, and which includes an elongated core having both end portions and an intermediate portion between the both end portions, and a coil wound around the intermediate portion of the core; a pair of magnetic flux introducing portions provided on the both end portions of the core of the antenna; a partition plate which is arranged between the first cover and the antenna in the inner space of the case and which is permeable to the radio wave; and a pair of flat and magnetic members which is arranged between the partition plate and the antenna in the inner space of the case and which is magnetically connected to the pair of magnetic flux introducing portions. An electric signal entered into the inner space of the case from an outside of the case through the first cover and the partition plate is introduced into the magnetic flux introducing portions through the flat and magnetic members and then the electric signal is introduced into the intermediate portion of the core from the magnetic flux introducing portions through the both end portions of the core to act on the coil. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a plan view showing a watch having a built-in antenna according to Embodiment 1 of the present invention; 
       FIG. 2  is a sectional view taken along a line II-II in  FIG. 1 ; 
       FIG. 3A  is a front view showing the antenna according to Embodiment 1 of the present invention; 
       FIG. 3B  is a sectional view taken along a line IIIB-IIIB in  FIG. 3A  and showing the antenna according to Embodiment 1 of the present invention; 
       FIG. 3C  is a side view showing the antenna according to Embodiment 1 of the present invention; 
       FIG. 4  is a block diagram showing an internal constitution of the watch; 
       FIG. 5A  is a front view showing the antenna according to Modification 1 of Embodiment 1 of the present invention; 
       FIG. 5B  is a sectional view taken along a line VB-VB in  FIG. 5A ; 
       FIGS. 6A ,  6 B, and  6 C are perspective views showing three examples of the antenna according to Modification 2 of Embodiment 1 of the present invention; 
       FIGS. 7A and 7B  are perspective views showing two examples of the antenna according to Modification 3 of Embodiment 1 of the present invention; 
       FIGS. 7C and 7D  are sectional views of two examples of a coil wound around the antenna according to Modification 3 of Embodiment 1 of the present invention; 
       FIG. 8  is a sectional view showing the antenna according to Modification 4 of Embodiment 1 of the present invention; 
       FIG. 9  is a side view showing the antenna according to Modification 5 of Embodiment 1 of the present invention; 
       FIG. 10  is a plan view showing the watch having the built-in antenna according to Embodiment 2 of the present invention; 
       FIG. 11  is a perspective view showing the antenna according to Embodiment 2 of the present invention; 
       FIG. 12  is a flowchart of a method for manufacturing the antenna according to the present invention; 
       FIG. 13  is a perspective view showing a mold for manufacturing a core of the antenna according to Embodiment 2 of the present invention; 
       FIG. 14  is a perspective view showing the mold in  FIG. 13  in a state that melted materials are poured into the mold for manufacturing a core of the antenna according to Embodiment 2 of the present invention; 
       FIG. 15  is a perspective view showing a pre-shaped core removed from the mold in  FIG. 13 ; 
       FIG. 16  is a perspective view showing the antenna according to Embodiment 2 of the present invention, which is completed by winding an electric wire around a shaped core to form a coil; 
       FIG. 17  is a perspective view showing the antenna according to a modification of Embodiment 2 of the present invention; 
       FIG. 18  is a plan view showing the watch having the built-in antenna according to Embodiment 3 of the present invention; 
       FIG. 19  is a plan view showing the antenna according to Embodiment 3 of the present invention; 
       FIG. 20  is a plan view showing the watch having the built-in antenna according to Embodiment 4 of the present invention; 
       FIG. 21  is a sectional view taken along a line XXI-XXI in  FIG. 20 ; 
       FIG. 22  is a view showing an operation of the antenna according to Embodiment 4 of the present invention; 
       FIG. 23  is a view showing an operation of the antenna according to Modification 1 of Embodiment 4 of the present invention; 
       FIG. 24  is a view schematically showing a constitution of the antenna according to Modification 1 of Embodiment 4 of the present invention; 
       FIG. 25  is a plan view showing the watch having the built-in antenna according to Embodiment 5 of the present invention; 
       FIG. 26  is a sectional view taken along a line XXVI-XXVI in  FIG. 25 ; 
       FIG. 27  is a view showing an operation of the antenna according to Embodiment 5 of the present invention; 
       FIG. 28  is a plan view showing the watch having the built-in antenna according to Embodiment 6 of the present invention; 
       FIG. 29  is a sectional view taken along a line XXIX-XXIX in  FIG. 28 ; 
       FIG. 30  is a view schematically showing a built-in process of the antenna into the watch according to Embodiment 6 of the present invention; 
       FIG. 31  is a plan view schematically showing a constitution of the watch according to Embodiment 7 of the present invention; 
       FIG. 32  is a sectional view taken along a line XXXII-XXXII in  FIG. 31 ; 
       FIG. 33  is a right side view of the watch according to Embodiment 7; 
       FIG. 34  is a sectional view taken along a line XXXIV-XXXIV in  FIG. 33 ; 
       FIG. 35  is a sectional view along line XXXV-XXXV of  FIG. 33 ; 
       FIG. 36  is a view showing a function of a signal magnetic flux in the antenna of  FIG. 35 ; 
       FIG. 37  is a sectional view corresponding to  FIG. 35  in the watch according to Embodiment 8 of the present invention; 
       FIG. 38  is a sectional view corresponding to  FIG. 35  in the watch according to Embodiment 9 of the present invention; 
       FIG. 39  is a view showing a function of the signal magnetic flux in the antenna of  FIG. 38 ; 
       FIG. 40  is a sectional view corresponding to  FIG. 35  in the watch according to Embodiment 10 of the present invention; 
       FIG. 41  is a sectional view corresponding to  FIG. 35  in the watch according to Embodiment 11 of the present invention; 
       FIG. 42  is a sectional view taken along a line XLII-XLII in  FIG. 41 ; 
       FIG. 43  is a sectional view corresponding to  FIG. 35  in the watch according to Embodiment 12 of the present invention; 
       FIG. 44  is a sectional view taken along a line XLIV-XLIV in  FIG. 43 ; 
       FIG. 45  is a sectional view corresponding to  FIG. 35  in the watch according to a modification of Embodiment 12; and 
       FIG. 46  is a sectional view taken along a line XLVI-XLVI in  FIG. 45 . 
   

   The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described hereinafter with reference to the drawings. Additionally, the scope of the present invention is not limited to embodiments and modifications shown below. 
   Embodiment 1 
     FIG. 1  is a plan view of a watch  1  having a built-in antenna  100  according to Embodiment 1 of the present invention, and  FIG. 2  is a sectional view taken along a line II-II in  FIG. 1 . 
   As shown in  FIGS. 1 and 2 , the watch  1  as an electronic device comprises a watch case  2  as a device case in which a watch timing portion  4  is stored, and band members  8  for attaching the watch case to user&#39;s wrist. 
   A watch glass  2   a  with a packing  2   b  is fitted into an upper surface center of the watch case  2  in such a manner that a dial plate  5  is visible, and switches  3  for instructing execution of each type of function of the watch  1  are attached to a periphery of the watch case  2 . A bezel  2   f  is disposed on an upper outer periphery of the watch case  2 , and a back lid  2   c  molded of a metal is attached to a bottom surface of the watch case  2  with a waterproof ring  2   d.    
   The watch timing portion  4  comprises: an upper housing portion  4   a ; a lower housing portion  4   b ; an analog pointer mechanism  7  which operates pointers  7   b  such as an hour pointer and a second pointer; the antenna  100  which receives a standard radio wave; and a circuit substrate  6  connected to the analog pointer mechanism  7  and the antenna  100  to control them. Peripheral edge portions of the lower housing portion  4   b , the upper housing portion  4   a , and the dial plate  5  are attached to an inner frame  2   g  disposed on an inner peripheral surface of the watch case  2 . 
   The lower housing portion  4   b  is supported above a buffer member  2   e  disposed on the back lid  2   c , and the circuit substrate  6  is disposed between the lower housing portion  4   b  and the upper housing portion  4   a . The dial plate  5  is disposed on an upper surface of the upper housing portion  4   a , and a frame-like member  5   b  is disposed on the upper surface peripheral edge portion of the dial plate  5  in a state in which the member abuts on a lower surface peripheral edge portion of the watch glass  2   a.    
   The analog pointer mechanism  7  has a pointer shaft  7   a  extending upward from a shaft hole  5   a  formed in the dial plate  5 , and pointers  7   b  such as the hour pointer and a minute pointer attached to the pointer shaft  7   a , and operates the pointers  7   b  above the dial plate  5 . A battery (not shown) for operating the analog pointer mechanism  7  is incorporated in, for example, the lower housing portion  4   b.    
   The antenna  100  is supported by the upper housing portion  4   a  and disposed between the lower housing portion  4   b  and the dial plate  5 . 
     FIGS. 3A to 3C  are explanatory views of the antenna  100  according to Embodiment 1,  FIG. 3A  is a front view of the antenna  100 ,  FIG. 3B  is a sectional view taken along a line IIIB-IIIB in  FIG. 3A , and  FIG. 3C  is a side view of the antenna  100 . 
   As shown in  FIGS. 3A to 3C , the antenna  100  comprises: a magnetic core  110 ; and a coil  120  wound around the core  110 . 
   The core  110  is formed into a bulk configuration using an amorphous metal as a material. Here, the bulk configuration refers to a solid shape formed using a casting mold or a mold. Specifically, examples of the bulked amorphous metal include an Fe-based alloy, a Pd-based alloy, a Zr-based alloy, an Ni-based alloy and the like. Examples of the Fe-based alloy include an Fe—M—B (M=Cr, W, Ta, Nb, Hf, Zr)-based alloy, an Fe—Co—RE—B (RE=Nb, Sm, Tb, Dy)-based alloy and the like. More specifically, the amorphous metal is formed of a composition such as Pd 40 Cu 30 Ni 10 P 20  or Fe 81 B 13 Si 14 C 2 . Moreover, when the melted alloy is worked into the bulk configuration by casting, an inner configuration is configured to be amorphous. More specifically, to manufacture the core  110 , for example, the alloy as the amorphous metal is melted, poured into the mold, and thereafter sintered at a crystallization starting temperature or a lower temperature in a state in which a pressure of, for example, 200 Mpa or more is applied. 
   The core  110  is a rod member, and each end surface  110 B is circular. Moreover, each of end portions  110 C of the core  110  has a conical shape. A sectional area of the core  110  gradually decreases from each end surface  110 B disposed in the end portion  110 C of the core  110  toward a central portion (shaft portion)  110 A, and is substantially constant in the central portion  110 A of the core  110 . Therefore, an area of each end surface  110 B disposed in the end portion  110 C of the core  110 , and a sectional area of the end portion  110 C are larger than the sectional area of the central portion  110 A of the core  110 . 
   Here, the core  110  is made of the amorphous metal. Therefore, for example, even when the central portion  110 A is configured to be thinner than that of the core made of ferrite, an equal or more strength can be obtained. Specifically, for example, in a case where a diameter of the central portion (shaft portion) of the core made of ferrite is set to 1.5 mm, a diameter of the central portion  110 A of the core using the amorphous metal can be set to 0.5 to 1.0 mm. 
   Moreover, the coil  120  is layered and wound around the core  110 . A diameter obtained by adding up the diameters of the core  110  and the laminated coil  120  is substantially equal to the diameter of each end surface  110 B of the core  110 . 
   Furthermore, when this antenna  100  is placed in a magnetic field (hereinafter referred to as the “signal magnetic field”) by a standard radio wave, the magnetic field acts on the antenna  100  as follows. It is to be noted that since a long wave having a wavelength of several kilometers is used as the standard radio wave, the magnetic field may be regarded as a parallel magnetic field in which a size of a magnetic field component does not change depending on a position in a range of an antenna size. Therefore, to simplify description, the signal magnetic field is regarded as the parallel magnetic field in the following description. 
   When the core  110  is placed in the signal magnetic field in such a manner that an axial line of the coil  120  is parallel to a magnetic field direction, as shown in  FIG. 3A , a magnetic flux (hereinafter referred to as the “signal magnetic flux”) M 1  by the signal magnetic field is concentrated on the core  110  having a specific permeability which is higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  120 , and in the coil  120 , there is generated such an induced electromotive force V as to generate a magnetic flux (hereinafter referred to as the “generated magnetic flux”) M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  120  according to Lenz&#39;s law. 
   It is to be noted that since the signal magnetic field is an alternating magnetic field, and a size or a direction of the signal magnetic flux M 1  periodically changes, the induced electromotive force V turns to an alternating power. The generated magnetic flux M 2  turns to an alternating magnetic field whose size or direction periodically changes following the change of the signal magnetic flux M 1  with time. 
   Moreover, the induced electromotive force V generated in the coil  120  is detected by a reception circuit (not shown) connected to the coil  120 . The reception circuit includes a tuning capacitor for tuning to a frequency (40 kHz or 60 kHz) of the standard radio wave to be received, or a loss resistance. The reception circuit is mounted on, for example, the circuit substrate  6  shown in  FIG. 2 . 
   Furthermore, even in the core  110 , there is generated such induced electromotive force as to generate the generated magnetic flux M 2  in the direction to inhibit the change of the signal magnetic flux M 1 . Accordingly, an eddy current is generated inside the core  110 , and there is generated an eddy current loss by the eddy current in the signal magnetic flux M 1 . 
   Here, an electric resistance of the core  110  is proportional to a length of the core  110  in a longitudinal direction, and inversely proportional to the sectional area of the core  110 . The central portion  110 A of the core  110  formed of the amorphous metal can be configured to be thinner than that of, for example, the core formed of ferrite. The sectional area of the central portion  110 A can be set to be smaller than the area of the end surface  110 B, and the electric resistance of the core  110  can be increased. 
   Therefore, the eddy current of the signal magnetic flux M 1  generated inside the core  110  is reduced, and the eddy current loss by the eddy current is inhibited. 
     FIG. 4  is a block diagram showing an internal constitution of the watch  1 . According to the figure, the watch  1  comprises: a CPU (Central Processing Unit)  10 ; an input section  20 ; a display section  30 ; a ROM (Read Only Memory)  40 ; a RAM (Random Access Memory)  50 ; a reception control section  60 ; a time code converting section  70 ; a timing circuit section  80 ; and an oscillation circuit section  82 . The respective sections excluding the oscillation circuit section  82  are connected to one another via a bus B, and the oscillation circuit section  82  is connected to the timing circuit section  80 . 
   The CPU  10  reads a program stored in the ROM  40  at a predetermined timing or in response to an operation signal input from the input section  20  to develop the program in the RAM  50 , and gives an instruction to each section of the watch  1  or transfers data based on the program. Specifically, the reception control section  60  is controlled to execute reception processing of the standard radio wave, for example, every predetermined time, and present time data timed by the timing circuit section  80  is corrected based on a standard time code (not shown) input from the time code converting section  70 . 
   The input section  20  comprises the switches  3  and the like for instructing execution of each type of function of the watch  1 . When these switches  3  are operated, a corresponding operation signal is output to the CPU  10 . 
   The display section  30  includes the dial plate  5  or the analog pointer mechanism  7  controlled by the CPU  10 , and displays a present time timed by the timing circuit section  80 . 
   The ROM  40  stores a system program or an application program relating to the watch  1 , and a program, data or the like for realizing the present embodiment. 
   The RAM  50  is used as an operation region of the CPU  10 , and temporarily stores the program read from the ROM  40 , the data processed by the CPU  10  or the like. 
   The reception control section  60  is provided with a radio wave receiving device  62 . The radio wave receiving device  62  has the antenna  100 , and the reception circuit (not shown), cuts an unnecessary frequency component of the standard radio wave received by the antenna  100  to extract the corresponding frequency signal, and outputs to the time code converting section  70  a signal converted into an electric signal corresponding to the frequency signal. 
   The time code converting section  70  converts the electric signal input from the radio wave receiving device  62  into a digital signal, generates a standard time code including data required for a clock function, such as an integration code or a week day code, and output the standard time code to the CPU  10 . 
   The timing circuit section  80  counts signals input from the oscillation circuit section  82  to set the present time, and outputs the timed present time data to the CPU  10 . The oscillation circuit section  82  is a circuit which constantly outputs a clock signal at a certain frequency. 
   As described above, according to the antenna  100  of Embodiment 1, the core  110  is manufactured by forming the amorphous metal into the bulk configuration. Therefore, the core  110  can be worked into an arbitrary shape, and the antenna  100  having a shape more adapted to a purpose can be manufactured. Since any thin film is not laminated as in the conventional core of the amorphous metal, working steps can be reduced, and the antenna  100  can be manufactured more easily. 
   Moreover, since the core  110  is made of the amorphous metal formed into the bulk configuration, and the amorphous metal has a remarkably high permeability, the sensitivity of the antenna  100  can be remarkably improved. Since the amorphous metal has a high strength, the central portion  110 A of the core  110  can be configured to be remarkably thin, and a winding number of the coil  120  can be increased, the sensitivity of the antenna  100  can be improved. Since the amorphous metal is not prone to rust, and has a satisfactory temperature stability, life of the antenna  100  can be lengthened. 
   Furthermore, since the area of each end surface  110 B of the core  110 , and the section area of each end portion  110 C of the corresponding core  110  are larger than the sectional area of the central portion  110 A of the core  110 , more standard radio waves can be received, and the sensitivity of the antenna  100  can be improved. 
   Additionally, since the sectional area of the central portion  110 A of the core  110  is smaller than the area of each end surface  110 B owned by the end portion  110 C of the core  110  and the sectional area of the end portion  110 C of the core  110 , an induced current generated in the core  110  can be reduced, and the eddy current loss can be suppressed. 
   Moreover, since the watch  1  has the built-in antenna  100  manufactured by forming the amorphous metal into the bulk configuration, the antenna  100  having the shape more adapted to the purpose can be built in. A degree of freedom of design increases, and the watch  1  can be miniaturized more. Since the core  110  of the built-in antenna  100  is manufactured by molding the amorphous metal, the radio waves can be received with good sensitivity, and the watch  1  can be manufactured at a reduced cost. Since the life of the built-in antenna  100  is lengthened, the life of the watch  1  can be lengthened more. 
   The antenna  100  according to Embodiment 1 of the present invention may be modified as in Modifications 1 to 4. 
   (Modification 1) 
     FIGS. 5A and 5B  are views for explaining an antenna  200  according to Modification 1 of Embodiment 1,  FIG. 5A  is a front view of the antenna  200 , and  FIG. 5B  is a sectional view taken along a line VB-VB in  FIG. 5A . 
   As shown in  FIGS. 5A ,  5 B, according to Modification 1 of the antenna  100  of Embodiment 1, the antenna  200  comprises a magnetic core  210  and a coil  220  wound around the core  210 . 
   As to the core  210 , an amorphous metal is used as a material and formed into a bulk configuration in the same manner as in the core  110 . As shown in  FIGS. 5A and 5B , the core is a long rod member, and end surfaces  210 B of end portions  210 C are circular. A sectional area of the core  210  continuously decreases from each end surface  210 B toward a center  210 D. Specifically, the sectional area is continuously reduced from the opposite end surfaces  210 B and  210 B toward the center  210 D. Therefore, an area of each end surface  210 B owned by the end portion  210 C of the core  210 , and a sectional area of the end portion  210 C of the core  210  are larger than the sectional area of a central portion  210 A of the core  210 . 
   Here, the core  210  is made of the amorphous metal. Therefore, for example, even when the central portion  210 A is configured to be thinner than a core made of ferrite, an equal or more strength can be obtained. 
   Moreover, a winding number of coil  220  wound around the core  210  in the center  210 D is larger than that in the opposite end portions  210 C,  210 C of the core  210 . 
   Furthermore, when this antenna  200  is placed in a signal magnetic field in such a manner that an axial line of the coil  220  is parallel to a magnetic field direction, as shown in  FIG. 5A , a signal magnetic flux M 1  is concentrated on the core  210  having a specific permeability which is higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  220 , and in the coil  220 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  220  according to Lenz&#39;s law. 
   In addition, the induced electromotive force V generated in the coil  220  is detected by a reception circuit (not shown) connected to the coil  220 . 
   Moreover, even in the core  210 , there is generated such induced electromotive force as to generate the generated magnetic flux M 2  in the direction to inhibit the change of the signal magnetic flux M 1  in the core  210 . Accordingly, an eddy current is generated inside the core  210 , and there is generated an eddy current loss by the eddy current in the signal magnetic flux M 1 . 
   Here, as to the central portion  210 A of the core  210 , since the central portion  210 A of the core  210  is configured to be thinner than that of a core made of ferrite, an electric resistance of the core  210  is larger than that of the core made of the ferrite, the eddy current generated in the core  210  is reduced, and an eddy current loss by the eddy current of the signal magnetic flux M 1  is inhibited. 
   According to the antenna  200  of Modification 1 of Embodiment 1, since the sectional area of the core  210  is continuously reduced from the opposite end surfaces  210 B,  210 B toward the center  210 D, the electric resistance increases from the opposite end surfaces  210 B,  210 B toward the center  210 D. An induced current generated in the core  210  can be reduced, and the eddy current loss can be suppressed. 
   Moreover, since the winding number of the coil  220  in the central portion  210 A is larger than that in each end portion  210   c  of the core  210 , a magnetic flux density increases toward the center  210 D, the induced electromotive force (reception voltage) generated in the center  210 D can be increased more, and a reception sensitivity of the antenna  200  can be raised. 
   Furthermore, since the core  210  has a smooth shape in such a manner that the sectional area of the core  210  is continuously reduced from the opposite end surfaces  210 B and  210 B toward the center  210 D, the core can be easily molded from a mold or the like. 
   (Modification 2) 
     FIGS. 6A to 6C  are perspective views showing three examples of an antenna  300  according to Modification 2 of Embodiment 1. 
   According to Modification 2 of the antenna  100  of Embodiment 1, as shown in  FIGS. 6A to 6C , the antenna  300  comprises: a magnetic core  310 ; and a coil  320  wound around the core  310 . 
   As to the core  310 , core members  310 E 1  to  310 E 4  are formed into columnar shapes having various diameters, using amorphous metals as materials in the same manner as in the core  310 , and flat surface portions of the core members  310 E 1  to  310 E 4  are connected and fixed to one another. 
   Specifically, in the core  310 , flat surfaces of the respective core members  310 E 1  to  310 E 4  are connected and fixed to one another in such a manner that diameters of the respective core members  310 E 1  to  310 E 4  are reduced toward a center  310 D of the core  310  in a stepwise manner. As a result, a sectional area of the core  310  is reduced from each end portion  310 C of the core  310  toward the center  310 D of the core  310 . Therefore, an area of each end surface  310 B owned by the end portion  310 C of the core  310  is larger than a sectional area of a central portion  310 A of the core  310 . 
   Here, any adhesive may be used as an adhesive for connecting and fixing core members  310 E to one another as long as the amorphous metal is bonded to another amorphous metal, and a nonconductive adhesive is preferable in respect of prevention of occurrence of an eddy current. 
   Moreover, the core  310  is made of the amorphous metal. Therefore, for example, even when the central portion  310 A is configured to be thinner than that of a core formed of ferrite, an equal or more strength can be obtained. 
   Furthermore, a winding number of the coil  320  wound around the core  310  in the center  310 D is larger than that in the opposite end portions  310 C,  310 C of the core  310 . 
   Additionally, according to Modification 2 of Embodiment 1, since the core  310  is manufactured by the connecting of the core members  310 E, a size or a shape of the antenna  300  can be changed more easily, when changing a combination of the core members  310 E. For example, as shown in  FIG. 6B , when the core member  310 E 4  configured to be thinnest is set to be longer than that shown in  FIG. 6A , the length of the center  310 D of the core  310  in a longitudinal direction can be lengthened. As shown in  FIG. 6C , when changing a size of the core member  310 E 1  for use in one end portion  310 C of the core  310  and that of the core member  310 E 5  for use in the other end portion  310 C, the antenna  300  can be formed into an asymmetric shape. 
   According to the antenna  300  of Modification 2 of Embodiment 2, since the sectional area of the core  310  is reduced from the opposite end portions  310 C,  310 C of the core  310  toward the center  310 D in the stepwise manner, an electric resistance of the core  310  increases from the opposite end portions  310 C,  310 C of the core  310  toward the center  310 D of the core  310 . An induced current generated in the core  310  can be reduced, and an eddy current loss can be suppressed. 
   Moreover, since a winding number of the coil  320  in the central portion  310 A is larger than that in each end portion  310 C of the core  310 , a magnetic flux density increases toward the center  310 D, an induced electromotive force (reception voltage) generated in the center  310 D can be increased, and a receiving sensitivity of the antenna  300  can be raised. 
   Furthermore, the core members  310 E formed into the columnar shapes having various sizes are connected and fixed to one another to thereby form the core  310 . Therefore, since a combination of the core members  310 E configuring the core  310  is changed, the size or the shape of the antenna  300  can be easily changed. 
   (Modification 3) 
     FIGS. 7A to 7D  are views for explaining an antenna  400  according to Modification 3 of Embodiment 1,  FIGS. 7A and 7B  are perspective views showing two examples of the antenna  400 , and  FIGS. 7C and 7D  are sectional views showing two examples of a coil  420  wound around cores  410  of the antennas  400  shown in  FIGS. 7A and 7B , respectively. 
   According to Modification 3 of the antenna  100  of Embodiment 1, as shown in  FIGS. 7A to 7D , the antenna  400  comprises the magnetic core  410  and the coil  420  wound around the core  410 . 
   As shown in  FIGS. 7A to 7D , the core  410  is formed into a bulk configuration using an amorphous metal in the same manner as in the core  110 . The core  410  comprises a central portion  410 A having a longitudinal round rod shape, and columnar end portions  410 C. A flat surface of each end portion  410 C substantially has right angles with respect to the central portion  410 A. Therefore, an area of each end surface  410 B of the core  410  is larger than a sectional area of the central portion  410 A of the core  410 . 
   Moreover, the core  410  is made of an amorphous metal. Therefore, for example, even when the central portion  410 A of the core is configured to be thinner than that of a core formed of ferrite, an equal or more strength can be obtained. 
   Furthermore, the coil  420  is layered and wound around the central portion  410 A of the core  410 . First, the coil  420  is wound around the central portion  410 A of the core  410  in such a manner that a diameter obtained by adding up a diameter of the central portion  410 A and that of the laminated coil  420  is larger than that of each end portion  410 C of the core  410  ( FIG. 7A ). Thereafter, the coil is compressed, when a pressure is applied to an outer peripheral surface of the antenna from a direction vertical to a longitudinal direction of the antenna  400 . As shown in  FIG. 7C , a section of the coil  420  before compressed has a circular shape, and small gaps exist among the respective coils  420 . However, as to the coil  420  after compressed, as shown in  FIG. 7D , the respective coils  420  are deformed and adhere to one another. Moreover, when the coil  420  wound around the central portion  410 A is compressed, the diameter obtained by adding up the diameter of the central portion  410 A and that of the laminated coil  420  is substantially equal to that of each end portion  410 C of the core  410  ( FIG. 7B ). 
   It is to be noted that the core  410  is formed of the amorphous metal. Therefore, unlike, for example, an antenna made of ferrite, even when the pressure or the like is added to the core after winding the coil  420  therearound, the core does not break. When the pressure is added, the winding number of the coil  420  can be increased more. 
   (Modification 4) 
     FIG. 8  shows a sectional view of an antenna  500  according to Modification 4 of Embodiment 1. 
   According to Modification 4 of the antenna  100  of Embodiment 1, as shown in  FIG. 8 , the antenna  500  comprises a magnetic core  510  and a coil  520  wound around the core  510 . 
   The core  510  is formed into a bulk configuration using an amorphous metal as a material. As shown in  FIG. 8 , the core is a long rod-like member, and an outer shape of an end surface  510 B included each end portion  510 C of the core  510  is circular. Concaves  510 E,  510 E opened outward in an axial direction of the core  510  are formed in the opposite end portions  510 C,  510 C of the core  510 . Sectional areas of the end portions  510 C,  510 C of the core  510  are reduced as much as the formed concaves  510 E,  510 E. An area of each end surface  510 B of the core  510  is larger than the sectional area of a central portion  510 A of the core  510 . 
   Moreover, the core  510  is made of the amorphous metal. Therefore, for example, even when the central portion  510 A is configured to be thinner than that of a core formed of ferrite, an equal or more strength can be obtained. 
   A winding number of the coil  520  wound around the core  510  in a center  510 D is larger than that in the opposite end portions  510 C,  510 C of the core  510 . 
   According to the antenna  500  of Modification 4 of Embodiment 1, since the concaves  510 E,  510 E are disposed in the opposite end portions  510 C,  510 C of the core  510 , a radio wave receiving sensitivity of the core  510  is not impaired, and sectional areas of the opposite end portions  510 C,  510 C can be reduced as much as the disposed concaves  510 E. Accordingly, electric resistances of the opposite end portions  510 C,  510 C can be increased, and an eddy current low resulting from an induced current generated in the core  510  can be suppressed more. 
   (Modification 5) 
     FIG. 9  shows a side view of an antenna  600  according to Modification 5 of Embodiment 1. 
   According to Modification 5 of the antenna  100  of Embodiment 1, as shown in  FIG. 9 , the antenna  600  comprises a magnetic core  610  and a coil  620  wound around the core  610 . 
   To form the core  610 , as shown in  FIG. 9 , there are bundled up a large number of wire rods  630  formed using amorphous metals in the same manner as in the core  110 . End portions of the wire rods  630  are formed into thin foil-like portions  630 A. Moreover, when the wire rods  630  are bundled up, the foil-like portions  630 A form end portions  610 B of the antenna  600 . Central portions  630 B of the wire rods  630  sandwiched between the foil-like portions  630 A form a central portion  610 A of the antenna  600 . The coil  620  is layered and wound around the central portion  610 A of the antenna  600 . 
   The wire rods  630  are formed using the amorphous metals. Therefore, for example, even when the wire rods are configured to be thinner than those formed of ferrite, an equal or more strength can be obtained. 
   Moreover, the wire rods  630  are bundled up to provide the core  610 . The central portions  630 B and the foil-like portions  630 A of the wire rods  630  are integrally formed into a bulk configuration using the amorphous metal as a material, and flat surfaces of the foil-like portions  630 A receive a signal magnetic flux (not shown). 
   According to the antenna  600  of Modification 5 of Embodiment 1, the wire rods  630  on end sides have the thinly formed foil-like portions  630 A. Therefore, the signal magnetic flux (not shown) can be received by flat surfaces of the foil-like portions  630 A, a reception area can be set to be broader than that of each wire rod  630  as such, and a receiving sensitivity can be improved. 
   Embodiment 2 
   According to Embodiment 2 of the present invention, as shown in  FIGS. 10 and 11 , a watch  1   a  is different from that of Embodiment 1 only in a structure of an antenna  700 . Therefore, a constitution similar to that of the watch  1  of Embodiment 1 is denoted with the same reference numerals, and description thereof is omitted. 
     FIG. 10  is a plan view of the watch  1   a  having the built-in antenna  700  according to Embodiment 2. 
   Moreover, according to Embodiment 2, as shown in  FIG. 11 , the antenna  700  comprises a core  710  which is a magnetic member, and a coil  720  wound around the core  710 . 
   In the core  710 , as shown in  FIG. 11 , for example, opposite end portions of a central portion  710 A having a square pole shape, and a substantially central portion between end portions  710 C having a square pole shape extending in a direction crossing the central portion  710 A at right angles form a substantially bonded H-shape, and are integrally and three-dimensionally formed into a bulk configuration of an amorphous metal. 
   Therefore, an area of each end surface  710 B of the core  710  is larger than a sectional area of the central portion  710 A of the core  710 . 
   Here, the core  710  is made of the amorphous metal. Therefore, for example, even when the central portion  710 A of the core  710  is configured to be thinner than that of a core made of ferrite, an equal or more strength can be obtained. 
   It has been described that the end portions  710 C and the central portion  710 A of the core  710  have the square pole shapes, but corners of a square pole may be smoothened, or a columnar shape may be used. 
   Moreover, when the core  710  is placed in a signal magnetic field in such a manner that an axial line of the coil  720  is parallel to a magnetic field direction, as shown in  FIG. 11 , a signal magnetic flux M 1  is concentrated on the core  710  having a specific permeability higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  720 , and in the coil  720 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  720  according to Lenz&#39;s law. 
   Furthermore, the induced electromotive force V generated in the coil  720  is detected by a reception circuit (not shown) connected to the coil  720 . 
   Moreover, as shown in  FIG. 10 , in a case where the antenna  700  according to Embodiment 2 is built in the watch  1   a  which is a type of radio-wave clock, an electronic circuit, a capacitor, a battery, a resistance and the like may be appropriately arranged in each division X 1  partitioned into a substantial U-shape by the end portions  710 C and the central portion  710 A. In this case, a magnetic shielding material is attached to the inside of the division X 1  of the end portions  710 C and the central portion  710 A, it is possible to reduce an influence of the generated magnetic flux M 2  on the electronic circuit and the like arranged in the division X 1 . 
   Next, a method for manufacturing the core  710  of the antenna  700  according to Embodiment 2 of the present invention will be described with reference to a flowchart shown in  FIG. 12 . 
   First, in step S 1  of  FIG. 12 , additives are added at predetermined ratios to iron, nickel and the like which is material of amorphous metal configuring the core  710  according to the present invention to melt the material in a vacuum melting furnace at a high temperature (melting step). 
   Next, in step S 2  of  FIG. 12 , as shown in  FIG. 13 , the melted material is quickly poured into a space  90 A of a mold  90 , the space  90 A adapted to the shape of the core  710  of the antenna  700 , through a funnel-like inlet port  90 B connected to the space  90 A in the mold  90  (pouring step). 
   Next, in step S 3  of  FIG. 12 , as shown in  FIG. 14 , the mold  90  is left to cool and solidify the melted material poured therein (cooling step). In a case that the material has a usual material composition for the amorphous metal, the material needs to be overcooled at a high cooling speed of, for example, 300 K/sec to become amorphous. 
   Therefore, a thin film-like core only can be manufactured by using the material having the usual material composition for the amorphous metal. However, in a case that the material has the material composition for the amorphous metal described above in relation to the present invention, the material can become amorphous at a very low cooling speed of, for example, 10 K/sec. Therefore, a more cubic core can be manufactured from the above described specific material composition for the amorphous metal in such a mold casting. 
   Subsequently, in step S 4  of  FIG. 12 , a cooled and solidified amorphous metal member  1000  is removed from the mold. The removed amorphous metal member  1000  is shown in  FIG. 15 . Thereafter, after cutting off an unnecessary portion  90 C cooled and solidified in the inlet port  90 B, the amorphous metal member  1000  is shaped by polishing or the like (shaping process). 
   Next, in step S 5  of  FIG. 12 , an electric wire is wound around the shaped core  710  to form the coil  720 , whereby the antenna  700  is manufactured. The completed antenna  700  is shown in  FIG. 16 . 
   According to the antenna  700  of Embodiment 2 described above, since an area of each end surface  710 B of the core  710  is larger than a sectional area of the central portion  710 A of the core  710 , more standard radio waves can be received, and a sensitivity of the antenna  700  can be enhanced. 
   Especially, since the core  710  is made of the bulked amorphous metal, even the core having a complicated shape such as the H-shape can be easily formed as compared with the conventional core provided by laminating a plurality of thin films of amorphous metals. 
   Moreover, since any thin film cannot be laminated as in the conventional core of the amorphous metal, working steps can be reduced, and the antenna  700  can be easily manufactured. 
   Furthermore, the electronic circuit, the capacitor, the battery, the resistance and the like can be appropriately arranged in each division X 1  partitioned into the substantial U-shape by the end portions  710 C and the central portion  710 A of the core  710 . 
   Even when the antenna  700  according to Embodiment 2 of the present invention is modified as follows if necessary, similar effects are obtained. 
   (Modification) 
   According to a modification of the antenna  700  of Embodiment 2, as shown in  FIG. 17 , an antenna  800  comprises: a magnetic core  810 ; and a coil  820  wound around the core  810 . 
   In the core  810 , as shown in  FIG. 17 , for example, opposite end portions of a central portion  810 A having a square pole shape, and end portions  810 C having a square pole shape extending in the same direction crossing the central portion  810 A at right angles form a substantially bonded U-shape, and are integrally and three-dimensionally formed into a bulk configuration of an amorphous metal. 
   Therefore, an area of each end surface  810 B of the core  810  is larger than a sectional area of the central portion  810 A of the core  810  in the same manner as in the antenna  700 . 
   Here, the core  810  is made of the amorphous metal. Therefore, for example, even when the central portion  810 A is configured to be thinner than that of a core made of ferrite, an equal or more strength can be obtained. 
   It has been described that the end portions  810 C and the central portion  810 A of the core  810  have the square pole shapes, but corners of a square pole may be smoothened, or a columnar shape may be used. 
   Moreover, when the core  810  is placed in a signal magnetic field in such a manner that an axial line of the coil  820  is parallel to a magnetic field direction, as shown in  FIG. 17 , a signal magnetic flux M 1  is concentrated on the core  810  having a specific permeability higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  820 , and in the coil  820 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  820  according to Lenz&#39;s law. 
   Furthermore, the induced electromotive force V generated in the coil  820  is detected by a reception circuit (not shown) connected to the coil  820 . 
   In addition, according to the modification, the core  810  of the antenna  800  is three-dimensionally formed in the same manner as in the method of manufacturing the core  710  of the antenna  700 . 
   It is to be noted that in a case where the antenna  800  according to the modification is built in a watch (not shown) which is a type of radio-wave clock, an electronic circuit, a capacitor, a battery, a resistance and the like may be appropriately arranged in a division X 2  partitioned into a substantial U-shape by the end portions  810 C and the central portion  810 A of the core  810  in the same manner as in the antenna  700  of Embodiment 2. In this case, a magnetic shielding material is attached to the inside of the division X 2  by the end portions  810 C and the central portion  810 A, it is possible to reduce an influence of the generated magnetic flux M 2  on the electronic circuit and the like arranged in the division X 2 . 
   Embodiment 3 
   According to Embodiment 3 of the present invention, as shown in  FIGS. 18 and 19 , in a watch  1   b , an only structure of an antenna  900  is different from that of the antenna  100  of Embodiment 1. Therefore, a constitution similar to that of the watch  1  of Embodiment 1 is denoted with the same reference numerals, and description thereof is omitted. 
     FIG. 18  is a plan view of the watch  1   b  having the built-in antenna  900  according to Embodiment 3. 
   Moreover, according to Embodiment 3, as shown in  FIG. 19 , the antenna  900  comprises a core  910  as a magnetic member, and a coil  920  wound around the core  910 . 
   As shown in  FIG. 19 , the core  910  comprises: for example, a central portion  910 A having a square pole shape; a first end portion  910 C extending from one end of the central portion  910 A outwards in a longitudinal direction into a substantially triangular shape in a plan view; and a second end portion  910 D extending from the other end of the central portion  910 A outwards in the longitudinal direction into a substantially triangular shape in a plan view and further extending into a substantially rectangular shape in the plan view. The shape of the first end portion  910 C is asymmetrical to that of the second end portion  910 D. The core  910  is integrally and three-dimensionally formed of the amorphous metal. 
   Moreover, the second end portion  910 D is provided with a substantially rectangular through hole X 3  as a space in which electronic components  2000  and the like can be arranged. 
   Furthermore, an area of each of end surfaces  910 B of the first end portion  910 C and the second end portion  910 D is larger than a sectional area of the central portion  910 A of the core  910 . 
   Here, the core  910  is made of the amorphous metal. Therefore, for example, even when the central portion  910 A is configured to be thinner than that of a core made of ferrite, an equal or more strength can be obtained. 
   It has been described that the first end portion  910 C, the second end portion  910 D, and the central portion  910 A of the core  910  have the substantially rectangular sections, but corners of the substantially rectangular section may be smoothened, or a circular section may be used. 
   Moreover, when the core  910  is placed in a signal magnetic field in such a manner that an axial line of the coil  920  is parallel to a magnetic field direction, as shown in  FIG. 19 , a signal magnetic flux M 1  is concentrated on the core  910  having a specific permeability higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  920 , and in the coil  920 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  920  according to Lenz&#39;s law. 
   Furthermore, the induced electromotive force V generated in the coil  920  is detected by a reception circuit (not shown) connected to the coil  920 . 
   In addition, the through hole X 3  disposed in the second end portion  910 D of the core  910  is surrounded with a magnetic member which is the core  910 , and the signal magnetic flux M 1  and the generated magnetic flux M 2  are concentrated and distributed in the surrounding magnetic member of the through hole X 3 . Therefore, there are remarkably few magnetic fluxes distributed in the through hole X 3 . 
   Moreover, according to Embodiment 3, the core  910  of the antenna  900  is three-dimensionally formed in the same manner as in the method of manufacturing the core  710  of the antenna  700  of Embodiment 2. 
   Furthermore, as shown in  FIG. 18 , in a case where the antenna  900  according to Embodiment 3 is built in the watch  1   b  which is a type of radio-wave clock, for example, an electronic circuit, a capacitor, a battery, a resistance and the like can be appropriately arranged as the electronic components  2000  in the through hole X 3  disposed in the second end portion  910 D of the core  910 . Here, since the through hole X 3  has a direction deviating from a path of the generated magnetic flux from the coil  920 , the portion is not easily influenced by the magnetic flux, but a countermeasure may be preferably taken such as the attaching of a magnetic shielding material onto an inner surface of the core  910  surrounding the through hole X 3 . 
   It is to be noted that it has been described in the present embodiment that the through hole X 3  has the substantially rectangular shape, but the portion may have any shape. 
   According to the above-described antenna  900  of Embodiment 3, since the shape of the first end portion  910 C of the core  910  is asymmetrical to that of the second end portion  910 D, there increases a degree of freedom in design of the watch  1   b  having the built-in antenna  900  comprising the core  910 , and the watch  1   b  can be miniaturized more. Especially, since the core  910  is made of the bulked amorphous metal, the core can be easily formed into the shape as compared with a conventional core provided by laminating a plurality of thin films of the amorphous metals. 
   Moreover, the core  910  is provided with the substantially rectangular through hole X 3  as the space in which the electronic components  2000  and the like can be arranged. Therefore, when the antenna  900  is built in the watch  1   b , electronic components  2000  such as the electronic circuit, the capacitor, the battery, and the resistance can be appropriately arranged in the through hole X 3  of the core  910 . While an outer shape of the core  910  is enlarged, and a sensitivity of the antenna  900  is enhanced, the watch  1   b  can be miniaturized more. 
   Furthermore, since remarkably few magnetic fluxes are distributed in a through hole X 3  of the core  910 , it is possible to reduce remarkably influences of the magnetic fluxes on electronic components  2000  such as the electronic circuit, the capacitor, the battery, and the resistance arranged in the through hole X. 
   According to Embodiments 1 to 3 of the present invention, the core can be prepared by forming the amorphous metal into the bulk configuration. As compared with the conventional core provided by the laminating of a plurality of thin films of the amorphous metals, the core is easily worked into an arbitrary shape, and the antenna having a shape adapted to its purpose can be manufactured more easily. Since any thin film is not laminated as in the conventional core of the amorphous metal, working steps can be reduced. 
   Moreover, since the core made of the amorphous metal formed into the bulk configuration has a remarkably high permeability, the sensitivity of the antenna can be remarkably improved. Since the amorphous metal has a high strength, the core can be configured to be remarkably thin, a winding number of the coil can be increased, and the sensitivity of the antenna can therefore be improved. Since the amorphous metal is not prone to rust, and its temperature stability is satisfactory, a life of the antenna can be lengthened more. 
   According to Embodiments 1 to 3 of the present invention, since a sectional area of the end portion of the core is larger than that of the central portion of the core, more radio waves can be received, and the sensitivity of the antenna can be enhanced. Especially, since the core is made of the bulked amorphous metal, the core can be easily formed into the shape as compared with the conventional core provided by the laminating of a plurality of thin films of the amorphous metals. 
   Moreover, according to Embodiment 1 of the present invention, the sectional area of the end portion of the core is reduced from the end surface of the core toward the central portion thereof, and the sectional area is constant in the central portion of the core. Therefore, the electric resistance increases from the end surface toward the central portion, the induced current generated in the core can be reduced, and the eddy current loss can be suppressed. 
   According to Modifications 1 and 2 of Embodiment 1 of the present invention, since the sectional area of the core is reduced from the end surface toward the central portion of the core continuously or in the stepwise manner, the electric resistance increases from the end surface toward the central portion. The induced current generated in the core can be reduced, and the eddy current loss can be suppressed. 
   Moreover, according to Modifications 1 and 2 of Embodiment 1 of the present invention, since the winding number of the coil in the central portion is larger than that in each end portion of the core, the magnetic flux density increases toward the central portion, a magnitude of the induced electromotive force (reception voltage) generated in the central portion can be increased, and the sensitivity of the antenna can be raised. 
   Furthermore, according to Modification 4 of Embodiment 1 of the present invention, since the end portion of the core is provided with the concave, the sectional area of the end portion can be reduced as much as that of the concave without impairing the receiving sensitivity of the radio wave of the core. Consequently, the electric resistance of the end portion can be increased, and it is further possible to suppress the eddy current loss resulting from the induced current generated in the core. 
   Additionally, according to Embodiment 3 of the present invention, the end portion of the core is provided with the space in which the electronic components can be arranged. Therefore, for example, in a case where the antenna is built in the electronic device, electronic components such as the electronic circuit, the capacitor, the battery, and the resistance can be appropriately arranged in the space of the core. While the outer shape of the core is enlarged, and the antenna sensitivity is improved, the electronic device can be miniaturized more. 
   Embodiment 4 
   Next, Embodiment 4 of the present invention will be described. 
   In a watch  1   c  according to Embodiment 4 of the present invention, as shown in  FIGS. 20 ,  21 , and  22 , an only structure of an antenna  1100  is different from that of the antenna  100  of Embodiment 1. Therefore, a constitution similar to that of the watch  1  of Embodiment 1 is denoted with the same reference numerals, and detailed description thereof is omitted. 
     FIG. 20  is a plan view of the watch  1   c  having the built-in antenna  1100  according to Embodiment 4 of the present invention, and  FIG. 21  is a sectional view taken along a line XXI-XXI in  FIG. 20 . 
   As shown in  FIGS. 20 and 21 , the watch  1   c  as an electronic device comprises a watch case  2  as a case in which a watch timing portion  4  is contained, and band members  8  for attaching the case to user&#39;s wrist are attached to the watch case  2 . 
   The watch case  2  has, for example, a cylindrical shape, and has openings in upper and lower portions thereof. A watch glass  2   a  with a packing  2   b  is fitted into an upper surface center of the watch case  2  in such a manner as to close the opening of the upper portion. The lower portion of the watch glass  2   a  is provided with a dial plate  5  as a decorative plate in such a manner that the dial plate is visible from the side of the upper portion of the watch glass  2   a . Switches  3  for instructing execution of each type of function of the watch  1  are attached to a periphery of the watch case  2 . A bezel  2   f  is disposed on an upper outer periphery of the watch case  2 , and a back lid  2   c  with a waterproof ring  2   d  is attached to a bottom surface of the watch case  2 . 
   The watch case  2  and the back lid  2   c  are formed of a material such as a metal which is impermeable to a radio wave. 
   The dial plate  5  as the decorative plate is formed of a material such as a resin which is permeable to the radio wave. 
   Here, the decorative plate is not limited to the dial plate  5  of the watch  1   c , and refers to, for example, a plate which is disposed in a display portion of the electronic device or the like to produce a decorative effect through vision. 
   The antenna  1100  is supported by an upper housing portion  4   a , and disposed between a lower portion of the dial plate  5  as the decorative plate and an upper portion of a lower housing portion  4   b . Moreover, the antenna is disposed in such a manner that the dial plate  5  is parallel to an axial line X of a central portion  1110 B (described later) of a core  1110  (described later) of the antenna  1100  in a longitudinal direction and that the dial plate  5  faces each facing surface  1110 C (described later) of an expanded portion  1110 A integrally formed on the end portion of the core  1110  in the longitudinal direction. 
     FIG. 22  is a view showing an operation of the antenna  1100  according to Embodiment 4. 
   As shown in  FIG. 22 , the antenna  1100  comprises the magnetic core  1110 , a coil  1120  wound around the core  1110  and the like. 
   The core  1110  is formed into a bulk configuration by use of an amorphous metal as a material. Here, the bulk configuration refers to a solid shape made using a casting mold or a mold. That is, the core  1110  comprises a single member by use of the amorphous metal as the material. Specifically, examples of the bulked amorphous metal include an Fe-based alloy, a Pd-based alloy, a Zr-based alloy, an Ni-based alloy and the like. Examples of the Fe-based alloy include an Fe—M—B (M=Cr, W, Ta, Nb, Hf, Zr)-based alloy, an Fe—Co—RE—B (RE=Nb, Sm, Tb, Dy)-based alloy and the like. More specifically, the amorphous metal is formed of a composition such as Pd 40 Cu 30 Ni 10 P 20  or Fe 81 B 13 Si 14 C 2 . Moreover, when the melted alloy is worked into the bulk configuration by casting, an inner configuration is configured to be amorphous. More specifically, to manufacture the core  1110 , for example, the alloy as the amorphous metal is melted, and sintered at a crystallization starting temperature or a lower temperature in a state in which a pressure of 200 Mpa or more is applied. 
   The core  1110  is a long rod member, and the expanded portions  1110 A formed integrally with the opposite end portions of the core  1110  in the longitudinal direction are bent from the back lid  2   c  toward the dial plate  5 . As to each expanded portion  1110 A, the facing surface  1110 C on a side opposite to a side on which the expanded portion  1110 A is formed integrally with the end portion of the core  1110  in the longitudinal direction, that is, the facing surface  1110 C facing the dial plate  5  is circular. Moreover, a diameter of each expanded portion  1110 A disposed on the end portion of the core  1110  in the longitudinal direction gradually decreases toward the central portion  1110 B of the core  1110  in the longitudinal direction, and the diameter is substantially constant in the central portion  1110 B of the core  1110  in the longitudinal direction. Therefore, an area of the facing surface  1110 C owned by the expanded portion  1110 A is larger than a sectional area of the central portion  1110 B of the core  1110  in the longitudinal direction. A length L 2  of the core  1110  in the longitudinal direction on a side of an opposite surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction is shorter than a length L 1  of the core  1110  in the longitudinal direction on a side of the facing surface  1110 C of the core  1110  facing the dial plate  5 . 
   Here, the core  1110  is made of the amorphous metal. Therefore, for example, even when the central portion  1110 B in the longitudinal direction is configured to be thinner than that of a core made of ferrite, an equal or more strength can be obtained. Specifically, for example, in a case where a diameter of the central portion  1110 B of the core made of ferrite in the longitudinal direction is set to 1.5 mm, a diameter of the central portion  1110 B of the core using the amorphous metal in the longitudinal direction can be set to 0.5 to 1.0 mm. 
   Moreover, the coil  1120  is layered and wound around the central portion  1110 B of the core  1110  in the longitudinal direction. 
   Furthermore, when this antenna  1100  is placed in a magnetic field (hereinafter referred to as the “signal magnetic field”) by a standard radio wave, the magnetic field acts on the antenna  1100  as follows. It is to be noted that since a long wave having a wavelength of several kilometers is used as the standard radio wave, the magnetic field may be regarded as a parallel magnetic field in which a size of a magnetic field component does not change depending on a position in a range of an antenna size. Therefore, to simplify description, the signal magnetic field is regarded as the parallel magnetic field in the following description. 
   When the core  1110  is placed in the signal magnetic field in such a manner that an axial line of the coil  1120  is parallel to a magnetic field direction, as shown in  FIG. 22 , a magnetic flux (hereinafter referred to as the “signal magnetic flux”) M 1  by the signal magnetic field is concentrated on the core  1110  having a specific permeability which is higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  1120 , and in the coil  1120 , there is generated such an induced electromotive force V as to generate a magnetic flux (hereinafter referred to as the “generated magnetic flux”) M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  1120  according to Lenz&#39;s law. 
   It is to be noted that since the signal magnetic field is an alternating magnetic field, and a size or a direction of the signal magnetic flux M 1  periodically changes, the induced electromotive force V turns to an alternating power. The generated magnetic flux M 2  turns to an alternating magnetic field whose size or direction periodically changes following the change of the signal magnetic flux M 1  with time. 
   Moreover, the induced electromotive force V generated in the coil  1120  is detected by a reception circuit (not shown) connected to the coil  1120 . The reception circuit includes a tuning capacitor for tuning to a frequency (40 kHz or 60 kHz in Japan) of the standard radio wave to be received, or a loss resistance. The reception circuit is mounted on a circuit substrate  6  shown in, for example,  FIG. 21 . 
   Here, the expanded portions  1110 A disposed on the end portions of the core  1110  in the longitudinal direction are bent from the back lid  2   c  toward the dial plate  5 , the diameter of each expanded portion  1110 A owned on the end portion of the core  1110  in the longitudinal direction gradually decreases toward the central portion  1110 B of the core  1110  in the longitudinal direction, and the diameter is substantially constant in the central portion  1110 B of the core  1110  in the longitudinal direction. 
   Moreover, the expanded portions  1110 A face the dial plate  5  at their facing surfaces  1110 C being disposed on a side opposite to a side on which the expanded portions  1110 A are formed integrally with the end portions of the core  1110  in the longitudinal direction. Accordingly, a radio wave receiving area on the side of each facing surface  1110 C facing the dial plate  5  is broader (larger) than that on the side of each surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction in the expanded portions  1110 A,  1110 A owned by the opposite end portions of the core  1110  in the longitudinal direction. 
   Therefore, the antenna  1100  is shaped in such a manner that during the receiving of the radio wave, a received radio wave amount on the side of each facing surface  1110 C of the core  1110  facing the dial plate  5  is larger than that on the side of each surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the antenna  1100 . 
   Moreover, the length L 1  of the core  1110  in the longitudinal direction on the side of the facing surface  1110 C facing the dial plate  5  is longer than the length L 2  in the longitudinal direction on the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction. Accordingly, a receiving sensitivity of the core  1110  in the longitudinal direction on the side of the facing surface  1110 C is high as compared with a case where the length L 1  on the facing surface  1110 C side is equal to the length L 2  on the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the antenna  1100 . 
   Furthermore, the antenna  1100  is shaped in such a manner that the received radio wave amount on the facing surface  1110 C side facing the dial plate  5  in the expanded portion  1110 A bent toward the dial plate  5  is larger than that on the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the antenna  1100 . 
   Additionally, the length L 2  of the core  1110  in the longitudinal direction on the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction is shorter than the length L 1  in the longitudinal direction on the side of the facing surface  1110 C facing the dial plate  5 . Therefore, the generated magnetic flux M 2  of the facing surface  1110 C of the core  1110  has a larger amount as compared with the side of the surface  1110 D opposite to the facing surface  1110 C. 
   Furthermore, the generated magnetic flux M 2  is generated on the surface  1110 D of the core  1110  opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction. The flux passes through the back lid  2   c , generates an eddy current in the back lid  2   c , and generates an eddy current loss of the signal magnetic flux M 1 . Since the generated magnetic flux M 2  on the side of the surface  1110 D opposite to the facing surface  1110 C of the core  1110  is suppressed as compared with the facing surface  1110 C side, the eddy current generated in the back lid  2   c  is suppressed, and the eddy current loss of the signal magnetic flux M 1  is suppressed. 
   Since an inner constitution of the watch  1   c  is the same as that described in Embodiment 1 with reference to  FIG. 4 , description thereof is omitted. 
   As described above, according to the antenna  1100  and the watch  1   c  in which the antenna  1100  is incorporated according to Embodiment 4, the core  1110  is disposed under the dial plate  5 . The expanded portions  1110 A are shaped in such a manner that during the receiving of the radio wave, the received radio wave amount is larger on the side of the facing surfaces  1110 C facing the dial plate  5  as compared with the side of the surfaces  1110 D opposite to the facing surfaces  1110 C with respect to the axial line X of the central portion  1110 B of the antenna  1100  in the longitudinal directions. Therefore, the radio wave can be sufficiently received from the dial plate  5  side, and the receiving sensitivity can be improved without enlarging the whole antenna  1100  as compared with the conventional antenna. 
   More specifically, in the expanded portions  110 A,  1110 A disposed on the opposite end portions of the core  1110  in the longitudinal direction, the radio wave receiving area on the side of each facing surface  1110 C facing the dial plate  5  is broader (larger) than that on the side of each surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction. Therefore, when the radio wave is received, more radio waves can be received from the facing surface  1110 C side in the expanded portions  110 A,  1110 A disposed on the opposite end portions of the core  1110  in the longitudinal direction. Therefore, the radio waves can be sufficiently received from the dial plate  5  side, and the receiving sensitivity can be improved without enlarging the whole antenna  1100  as compared with the conventional antenna. 
   Moreover, the length L 2  of the core  1110  in the longitudinal direction on the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B of the core  1110  in the longitudinal direction is shorter than the length L 1  of the core  1110  in the longitudinal direction on the facing surface  1110 C side. Therefore, the receiving sensitivity on the facing surface  1110 C side in the longitudinal direction of the core  1110  increases, and the receiving sensitivity of the antenna  1100  can be improved more. 
   Furthermore, since the expanded portions  1110 A are bent from the end portions of the core  1110  in the longitudinal direction toward the dial plate  5 , the radio waves from the dial plate  5  side can be received more easily. The receiving sensitivity can be improved without enlarging the whole antenna as compared with the conventional antenna. 
   Additionally, as to each expanded portion  1110 A, the area of the facing surface  1110 C facing the dial plate  5  is larger than the sectional area of the central portion  1110 B of the core  1110  in the longitudinal direction. Therefore, more radio waves can be received from the facing surfaces  1110 C in the expanded portions  1110 A, and the receiving sensitivity of the antenna  1100  can be improved more. 
   Moreover, the expanded portions  1110 A bend from the end portions of the core  1110  in the longitudinal direction toward the dial plate  5 . The diameters of the expanded portions  1110 A gradually decrease toward the central portion  1110 B of the core  1110  in the longitudinal direction, and are substantially constant in the central portion  1110 B of the core  1110  in the longitudinal direction. Therefore, the radio wave received amount is large on the facing surface  1110 C side facing the dial plate  5  in the expanded portion  1110 A as compared with the side of the surface  1110 D opposite to the facing surface  1110 C with respect to the axial line X of the central portion  1110 B. Therefore, the radio waves can be received sufficiently from the dial plate  5  side. The receiving sensitivity can be improved without enlarging the whole antenna  1100  as compared with the conventional antenna. 
   Furthermore, since the amorphous metal is formed into the bulk configuration to manufacture the core  1110 , the core  1110  is easily worked into the arbitrary shape as compared with the conventional core provided by the laminating of a plurality of thin films of amorphous metals. Therefore, it is possible to manufacture the antenna  1100  having the shape adapted to its purpose more easily. Since any thin film is not laminated unlike the conventional core of the amorphous metal, working steps can be reduced. 
   Additionally, since the core  1110  configured by the amorphous metal configured into the bulk configuration has a remarkably high permeability, the receiving sensitivity of the antenna  1100  can be improved remarkably. Since the amorphous metal has a high strength, the core  1110  can be formed to be remarkably thin, and the winding number of the coil  1120  can be increased. Therefore, the receiving sensitivity of the antenna  1100  can be improved. Since the amorphous metal is not prone to rust, and has a satisfactory temperature stability, the life of the antenna  1100  can be lengthened. 
   In addition, the watch  1   c  has the built-in antenna  1100  whose receiving sensitivity has been improved more than before. Therefore, there can be provided the watch  1   c  capable of receiving the radio waves with a satisfactory sensitivity. 
   The antenna  1100  according to Embodiment 4 of the present invention may be modified as follows if necessary. 
   (Modification 1) 
     FIG. 23  is a view showing an operation of an antenna  1200  according to Modification 1 of Embodiment 4.  FIG. 24  is a view schematically showing a constitution of the antenna  1200  according to Modification 1 of Embodiment 4. 
   As shown in  FIG. 23 , the antenna  1200  obtained by modifying the antenna  1100  of Embodiment 4 comprises: a magnetic core  1210 ; a coil  1220  wound around the core  1210  and the like. 
   Moreover, in the same manner as in the antenna  1100  of Embodiment 4, the antenna  1200  is disposed under a dial plate  5  in such a manner that the dial plate  5  is parallel with an axial line X of a central portion  1210 B of the core  1210  (described later) of the antenna  1200  in a longitudinal direction. 
   The core  1210  is formed into a bulk configuration by use of an amorphous metal as a material in the same manner as in the antenna  1100  of Embodiment 4, and comprises: as shown in  FIG. 23 , expanded portions  1210 A having two flat surfaces substantially parallel to the dial plate  5  and having a substantially rectangular parallelepiped shape; and the central portion  1210 B as a long rod-like member whose section has a circular shape in the longitudinal direction. More specifically, as shown in  FIGS. 23 and 24 , engagement holes  1210 F engaging with end portions  1210 E of the core  1210  in the longitudinal direction are disposed in lower portions of the expanded portions  1210 A. When the engagement holes  1210 F are engaged with the end portions  1210 E of the core  1210  in the longitudinal direction, the expanded portions  1210 A are connected and fixed to the core  1210 . An area of the flat surface of the expanded portion  1210 A on a side of a facing surface  1210 C of the expanded portion  1210 A facing the dial plate  5  is broader (larger) than a flat surface on a side of a surface  1210 D opposite to the facing surface  1210 C with respect to an axial line X of the central portion  1210 B of the core  1210  in the longitudinal direction. A sectional area of the central portion  1210 B of the core  1210  in the longitudinal direction is smaller than that of each of the expanded portions  1210 A,  1210 A disposed on the opposite end portions  1210 E,  1210 E of the core  1210 . 
   It is to be noted that an adhesive for connecting and fixing the expanded portions  1210 A to the end portions  1210 E of the core  1210  in the longitudinal direction is not limited as long as the amorphous metals are bonded to each other, and a nonconductive adhesive is preferable from a viewpoint of prevention of an eddy current loss. 
   Moreover, the core  1210  is made of the amorphous metal. Therefore, even when the central portion  1210 B of the longitudinal direction is configured to be thinner than that of a core formed of, for example, ferrite, an equal or more strength can be obtained. 
   Furthermore, when the antenna  1200  is placed in a signal magnetic field in such a manner that an axial line of the coil  1220  is parallel to a magnetic field direction, as shown in  FIG. 23 , a signal magnetic flux M 1  is concentrated on the core  1210  having a specific permeability which is higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  1220 , and in the coil  1220 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  1220  according to Lenz&#39;s law. 
   Additionally, the induced electromotive force V generated in the coil  1220  is detected by a reception circuit (not shown) connected to the coil  1220 . 
   Here, the end portions  1210 E of the core  1210  in the longitudinal direction are connected and fixed to the lower portions of the expanded portions  1210 A. The area of the flat surface of each expanded portion  1210 A on the facing surface  1210 C side facing the dial plate  5  is broader (larger) than that on the side of the surface  1210 D opposite to the facing surface  1210 C with respect to the axial line X of the central portion  1210 B of the core  1210  in the longitudinal direction. Therefore, in the expanded portions  1210 A,  1210 A disposed on the opposite end portions  1210 E,  1210 E of the core  1210  in the longitudinal direction, a radio wave receiving area on the side of the facing surface  1210 C facing the dial plate  5  is broader (larger) than that on the side of the surface  1210 D opposite to the facing surface  1210 C with respect to the axial line X of the central portion  1210 B of the core  1210  in the longitudinal direction. Therefore, the antenna  1200  has such a shape that during the receiving of the radio wave, a received radio wave amount is larger on the facing surfaces  1210 C of the core  1210  facing the dial plate  5  as compared with the surfaces  210 D opposite to the facing surfaces  1210 C with respect to the axial line X of the antenna  1200 . 
   Moreover, the antenna  1200  has such a shape that the received radio wave amount is larger on the facing surfaces  1210 C of the expanded portions  1210 A facing the dial plate  5  as compared with the surfaces  1210 D opposite to the facing surfaces  1210 C with respect to the axial line X of the antenna  1200 . Therefore, the generated magnetic flux M 2  is larger on the side of the facing surfaces  1210 C of the expanded portions  1210 A facing the dial plate  5  as compared with the side of the surfaces  1210 D opposite to the facing surfaces  1210 C. The generated magnetic flux M 2  is generated on the side of the surfaces  1210 D of the expanded portions  1210 A opposite to the surfaces  1210 C facing the dial plate  5  with respect to the axial line X of the antenna  1200 . The flux passes through a back lid (not shown), generates an eddy current in the back lid, and generates the eddy current loss of the signal magnetic flux M 1 . On the other hand, the generated magnetic flux M 2  on the side of the surfaces  1210 D of the expanded portions  1210 A opposite to the surfaces  1210 C facing the dial plate  5  with respect to the axial line X of the antenna  1200  is suppressed as compared with the facing surface  1210 C side, the eddy current generated in the back lid (not shown) is suppressed, and the eddy current loss of the signal magnetic flux M 1  is suppressed. 
   Therefore, even in the antenna  1200  of Modification 1 and a watch in which this antenna  1200  is incorporated, needless to say, effects can be obtained which are similar to those of the antenna  1100  and the watch  1   c  of Embodiment 1. The expanded portions  1210 A which can be easily formed can be connected to the end portions  1210 E of the core  1210  to manufacture the core  1210 . Therefore, the antenna  1200  can be manufactured more easily. The antenna  1200  is manufactured by the combining of the expanded portions  1210 A with the core  1210 . Therefore, even an antenna having a complicates shape can be comparatively easily manufactured by the combining of expanded portions having various shapes with a central portion. 
   Embodiment 5 
   In a watch  1   d  according to Embodiment 5 of the present invention, as shown in  FIGS. 25 ,  26 , and  27 , an only structure of an antenna  1300  is different from that of the antenna  100  of Embodiment 1. Therefore, a constitution similar to that of the watch  1  of Embodiment 1 is denoted with the same reference numerals, and description thereof is omitted. 
     FIG. 25  is a plan view of the watch  1   d  having the built-in antenna  1300  according to Embodiment 5 of the present invention, and  FIG. 26  is a sectional view taken along a line XXVI-XXVI in  FIG. 25 . 
   Moreover,  FIG. 27  is a view showing an operation of the antenna  1300  according to Embodiment 5. 
   As shown in  FIG. 26 , the antenna  1300  is disposed under a dial plate  5  as a decorative plate. 
   Moreover, as shown in  FIG. 27 , the antenna  1300  according to Embodiment 5 comprises: a magnetic core  1310 ; a coil  1320  wound around the core  1310 ; magnetic sheets  1310 C,  1310 C attached to opposite end portions  1310 A,  1310 A of the core  1310  in a longitudinal direction in such a manner as to protrude outward from the core  1310  and the like. 
   As shown in  FIG. 27 , the core  1310  is, for example, a long rod-like member whose section has a circular shape. Each end portion  1310 A of the core  1310  in the longitudinal direction is configured into, for example, a flat surface shape, and each magnetic sheet  1310 C is attached to the end portion  1310 A of the longitudinal direction in such a manner as to protrude outward from the core  1310 . The core  1310  is three-dimensionally formed into a bulk configuration by use of the amorphous metal as the material in the same manner as in the core  110  of the antenna  100 . Each magnetic sheet  1310 C is configured into a sheet or foil shape by use of the amorphous metal or another magnetic material as the material. 
   Moreover, the core  1310  is made of the amorphous metal. Therefore, even when a central portion  1310 B of the core  1310  in the longitudinal direction is configured to be thinner than that of a core made of, for example, ferrite, an equal or more strength can be obtained. 
   Furthermore, the coil  1320  is layered and wound around the central portion  1310 B of the core  1310  in the longitudinal direction. 
   Additionally, when the core  1310  is placed in a signal magnetic field in such a manner that an axial line of the central portion  1310 B of the coil  1320  in the longitudinal direction is parallel to a magnetic field direction, as shown in  FIG. 27 , a signal magnetic flux M 1  is concentrated on the core  1310  having a specific permeability which is higher than that of a surrounding space. As a result, the signal magnetic flux M 1  is interlinked with the coil  1320 , and in the coil  1320 , there is generated such an induced electromotive force V as to generate a generated magnetic flux M 2  in a direction to inhibit a change of the signal magnetic flux M 1  in the coil  1320  according to Lenz&#39;s law. 
   Moreover, the induced electromotive force V generated in the coil  1320  is detected by a reception circuit (not shown) connected to the coil  1320 . 
   As described above, according to the antenna  1300  of Embodiment 5 and the watch  1   d  in which this antenna  1300  is incorporated, flat surfaces of the magnetic sheets  1310 C attached to the end portions  1310 A of the core  1310  in the longitudinal direction can be used as receiving surfaces of radio waves. Therefore, a broader (larger) receiving area can be secured while hardly requiring a three-dimensional space. A receiving sensitivity of the antenna  1300  can be improved. 
   Furthermore, since the amorphous metal has a high strength, the magnetic sheets  1310 C can be thinned without being torn. 
   Additionally, the watch  1   d  has the built-in antenna  1300  whose receiving sensitivity has been improved, and therefore there can be provided the watch  1   d  capable of receiving the radio wave with a satisfactory sensitivity. 
   Embodiment 6 
   As shown in  FIGS. 28 ,  29 , and  30 , a watch  1   e  according to Embodiment 6 of the present invention is different in magnetic sheets  5   c  as magnetic layers. An only structure of an antenna  1400  is different from that of the antenna  100  of Embodiment 1. Therefore, a constitution similar to that of the watch  1  of Embodiment 1 is denoted with the same reference numerals, and description thereof is omitted. 
     FIG. 28  is a plan view of the watch  1   e  having the built-in antenna  1400  according to Embodiment 6, and  FIG. 29  is a sectional view taken along a line XXIX-XXIX in  FIG. 28 .  FIG. 30  is a view schematically showing a built-in process of the antenna  1400  into the watch  1   e  according to Embodiment 6. 
   As shown in  FIG. 29 , the antenna  1400  is supported by an upper housing portion  4   a , and disposed between a lower portion of a dial plate  5  as a decorative plate and an upper portion of a lower housing portion  4   b . Moreover, the antenna is disposed in such a manner that the dial plate  5  is parallel to an axial line X of a central portion  1410 B of a core  1410  (described later) of the antenna  1400  in a longitudinal direction. 
   Moreover, the magnetic sheets  5   c  are disposed on a lower surface of the dial plate  5 , that is, the surface on an antenna  1400  side. 
   As shown in  FIG. 28 , the magnetic sheets  5   c  are attached to regions outside a region facing the central portion  1410 B (described later) of the antenna  1400  in the longitudinal direction in the surface of the dial plate  5  on the antenna  1400  side. 
   Moreover, each magnetic sheet  5   c  is a sheet having a substantial fan shape surrounded with a circle slightly smaller than an outer circular shape of the dial plate  5  and straight lines connecting opposite end portions of the circle. As a magnetic material forming the magnetic sheet  5   c , an amorphous metal, ferrite or the like is usable, but a material having a high strength is preferable from a viewpoint of prevention of breaking of the sheet, and the sheet is preferably formed of the amorphous metal. 
   As shown in  FIG. 30 , the antenna  1400  comprises: the magnetic core  1410 ; a coil  1420  wound around the core  1410  and the like. 
   For example, in the same manner as in the core  1110 , the core  1410  is formed into a bulk configuration by use of an amorphous metal as a material. As shown in  FIG. 30 , the core comprises: expanded portions  1410 A having flat surfaces substantially parallel to the dial plate  5  and having substantially rectangular parallelepiped shapes; and the central portion  1410 B which is a long rod-like member having a circular section in the longitudinal direction. 
   Moreover, the core  1410  is made of the amorphous metal. Therefore, even when the central portion  1410 B of the longitudinal direction is configured to be thinner than that of a core made of, for example, ferrite, an equal or more strength can be obtained. 
   Furthermore, the antenna  1400  is disposed in such a manner that the expanded portions  1410 A,  1410 A disposed on opposite end portions of the core  1410  are brought into contact with the magnetic sheets  5   c  attached to the dial plate  5 , and the expanded portions  1410 A are magnetically connected to the magnetic sheets  5   c.    
   In addition, as shown in  FIG. 30 , the above-described antenna  1400  is disposed above a back lid  2   c  in a watch case  2 , and the dial plate  5  provided with the magnetic sheets  5   c  is disposed above the antenna  1400 . 
   According to the antenna  1400  of Embodiment 6 described above, the magnetic sheets  5   c  attached to the lower surface of the dial plate  5 , that is, the surface on the antenna  1400  side are used as radio wave receiving surfaces, and radio waves can be received from the surfaces of the magnetic sheets  5   c . That is, when the antenna  1400  is placed in a signal magnetic field in such a manner that the axial line of the coil  1420  is parallel to a magnetic field direction, a magnetic flux (not shown) by a signal magnetic field is concentrated on the core  1410  through the magnetic sheets  5   c  and the expanded portions  1410 A disposed on the end portions of the core  1410 . As a result, the signal magnetic flux (not shown) is interlinked with the coil  1420 , and in the coil  1420 , there is generated such an induced electromotive force V as to generate a magnetic flux (not shown) in a direction to inhibit a change of the signal magnetic flux (not shown) in the coil  1420  according to Lenz&#39;s law. Therefore, the radio waves from the dial plate  5  side can be received with a satisfactory efficiency. 
   Since the antenna  1400  can receive the radio wave through the surfaces of the magnetic sheets  5   c  having broad areas, more radio waves can be received, a receiving sensitivity of the antenna  1400  can be improved, and there can be provided the watch  1   e  capable of receiving the radio wave with a satisfactory sensitivity. 
   Moreover, since the amorphous metal has a high strength, the magnetic sheets  5   c  can be thinned without being broken. 
   Furthermore, since the amorphous metal is formed into the bulk configuration to manufacture the core  1410 , the core  1410  is easily worked into the arbitrary shape as compared with the conventional core provided by the laminating of a plurality of thin films of amorphous metals. Therefore, it is possible to manufacture the antenna  1400  having the shape adapted to its purpose more easily. Since any thin film is not laminated unlike the conventional core of the amorphous metal, working steps can be reduced. 
   Additionally, since the core  1410  configured by the amorphous metal formed into the bulk configuration has a remarkably high permeability, the receiving sensitivity of the antenna  1400  can be improved remarkably. Since the amorphous metal has the high strength, the core  1410  can be formed to be remarkably thin, and the winding number of the coil  1420  can be increased. Therefore, the receiving sensitivity of the antenna  1400  can be improved. Since the amorphous metal is not prone to rust, and has a satisfactory temperature stability, the life of the antenna  1400  can be lengthened. 
   It is to be noted that in Embodiment 6, magnetic layers are provided by the magnetic sheets  5   c , but may be disposed, for example, by chemical or physical coating with a magnetic material such as the amorphous metal. 
   Moreover, the antenna  1400  is disposed in such a manner as to bring the expanded portions  1410 A,  1410 A disposed on the opposite end portions of the core  1410  into the magnetic sheets  5   c  attached to the dial plate  5 , but the antenna  1400  may be disposed in such a manner that the expanded portions  1410 A face the magnetic sheets  5   c  through a magnetically connectable space. 
   Furthermore, a shape of each expanded portion  1410 A disposed on the end portion of the core  1410  is not limited to the above-described shape, and any shape may be used as long as the expanded portion can be magnetically connected to the magnetic sheet  5   c.    
   According to Embodiment 4 of the present invention, the antenna and the core are disposed under the decorative plate, and the expanded portions have such shapes that during the receiving of the radio wave, a received radio wave amount is larger on the side of the surfaces facing the decorative plate as compared with the side of the surfaces opposite to the facing surfaces with respect to the axial line of the central portion of the core in the longitudinal direction. Therefore, the radio waves from the decorative plate side can be sufficiently received, and the receiving sensitivity can be improved without enlarging the whole antenna as compared with the conventional antenna. 
   Moreover, according to Embodiment 4 of the present invention, since the expanded portions bend from the end portions of the core in the longitudinal direction toward the decorative plate, the radio waves from the decorative plate side can be more easily received, and the receiving sensitivity can be improved without enlarging the whole antenna as compared with the conventional antenna. 
   Furthermore, according to Embodiment 4 of the present invention, an area of the facing surface of each expanded portion facing the decorative plate is larger than a sectional area of the central portion of the core in the longitudinal direction, more radio waves can be received from the facing surface of the expanded portion, and the receiving sensitivity of the antenna can be improved more. 
   Additionally, according to Embodiment 4 of the present invention, a radio wave receiving area on the side of the facing surface of the expanded portion facing the decorative plate is larger than that on the surface opposite to the facing surface with respect to the axial line. Therefore, when the radio wave is received, more radio waves can be received from the facing surface of each expanded portion. Therefore, the radio waves can be sufficiently received from the decorative plate side, and the receiving sensitivity can be improved without enlarging the whole antenna as compared with the conventional antenna. 
   Moreover, according to Embodiment 4 of the present invention, each expanded portion bends from the end portion of the core in the longitudinal direction toward the decorative plate, and a diameter of the expanded portion gradually decreases toward the central portion of the core in the longitudinal direction, and is substantially constant in the central portion of the core in the longitudinal direction. Therefore, a radio wave received amount is larger on the side of the facing surface of the expanded portion facing the dial plate with respect to the axial line of the central portion as compared with the side of the surface opposite to the facing surface. Therefore, the radio waves can be sufficient received from the decorative plate, and the receiving sensitivity can be improved without enlarging the whole antenna as compared with the conventional antenna. 
   Furthermore, according to Embodiment 5 of the present invention, the flat surfaces of the magnetic sheets attached to the end portions of the core in the longitudinal direction can be used as the radio wave receiving surfaces. Therefore, a three-dimensional space is hardly required, a broader receiving area can be secured, and the receiving sensitivity of the antenna can be enhanced. When each magnetic sheet is made of the amorphous metal having the high strength, the magnetic sheet can be thinned. 
   Additionally, according to Embodiment 6 of the present invention, the flat surface of the magnetic layer disposed on the lower surface of the decorative plate is used as the radio wave receiving surface, and the radio wave can be received through the magnetic layer. Therefore, the radio wave from the decorative plate can be received with a satisfactory efficiency. 
   Moreover, since the antenna can receive the radio wave through the surface of the magnetic layer having a large area, more radio wave can be received, and the receiving sensitivity of the antenna can be enhanced. There can be provided the electronic device capable of receiving the radio wave with a satisfactory sensitivity. 
   Furthermore, according to Embodiments 4 to 6 of the present invention, since the amorphous metal is formed into the bulk configuration to manufacture the core, the core is easily worked into the arbitrary shape as compared with the conventional core provided by the laminating of a plurality of thin films of amorphous metals. Therefore, it is possible to manufacture the antenna having the shape adapted to its purpose more easily. Since any thin film is not laminated unlike the conventional core of the amorphous metal, working steps can be reduced. 
   Additionally, since the core configured by the amorphous metal configured into the bulk configuration has a remarkably high permeability, the receiving sensitivity of the antenna can be improved remarkably. Since the amorphous metal has the high strength, the core can be formed to be remarkably thin, and the winding number of the coil can be increased. Therefore, the receiving sensitivity of the antenna can be improved. Since the amorphous metal is not prone to rust, and has a satisfactory temperature stability, the life of the antenna can be lengthened. 
   It is to be noted that in the embodiment of the present invention, the core is formed of the amorphous metal, but may be formed of a magnetic material such as ferrite. 
   Moreover, it has been described in the present embodiment a case where the present invention is applied to the antenna built in a watch type radio-wave clock as the electronic device to receive the standard radio wave, but the application of the present invention is not limited to this. The present invention may be applied to, for example, an antenna for a device mounted in a car, a keyless entry system, an IC tag or the like. 
   Embodiment 7 
     FIG. 31  is a plan view schematically showing a constitution of a watch  2100  according to Embodiment 7 of the present invention.  FIG. 32  is a sectional view taken along a line XXXII-XXXII in  FIG. 31 .  FIG. 33  is a right side view of the watch  2100  of  FIG. 31 .  FIG. 34  is a sectional view taken along a line XXXIV-XXXIV in  FIG. 33 . 
   As an electronic device illustrated as Embodiment 7 to which an electronic device of the present invention is applied, as shown in  FIGS. 31 and 32 , the watch  2100  has a built-in antenna  2005  to receive a radio wave (hereinafter referred to as the “standard radio wave”) carrying time information relating to a standard time and correct a displayed time. 
   The watch  2100  comprises a metal-made watch case  2002  as a device case in which a watch timing portion  2001  is stored, and a watch glass  2002   a  with a packing  2002   b  is fitted into an upper surface center of the watch case  2002 . 
   Moreover, a back lid  2002   c  with a waterproof ring  2002   d  is attached to a lower surface of the watch case  2002 , and a buffer member  2002   e  is disposed between the watch timing portion  2001  and the back lid  2002   c.    
   The watch timing portion  2001  comprises: an upper housing portion  2001   a ; a lower housing portion  2001   b ; an analog pointer mechanism  2004  which operates pointers  2004   b  such as an hour pointer and a second pointer on a dial plate  2003 ; the antenna  2005  which receives a standard radio wave; and a circuit substrate  2006  connected to the analog pointer mechanism  2004  and the antenna  2005  to control them. Peripheral edge portions of the lower housing portion  2001   b , the upper housing portion  2001   a , and the dial plate  2003  are attached to an inner frame  2002   f  disposed on an inner peripheral surface of the watch case  2002 . Portions of the lower housing portion  2001   b , the upper housing portion  2001   a , and the inner frame  2002   f  corresponding to a place where the antenna  2005  is disposed are cut out to secure a storage space of the antenna  2005 . 
   The lower housing portion  2001   b  is supported above the buffer member  2002   e  disposed above the back lid  2002   c , and the circuit substrate  2006  is disposed between the lower housing portion  2001   b  and the upper housing portion  2001   a . The dial plate  2003  is disposed on an upper surface of the upper housing portion  2001   a . The upper housing portion  2001   a  is provided with the analog pointer mechanism  2004 . The analog pointer mechanism  2004  has a pointer shaft  2004   a  extending upward from a shaft hole  2003   a  disposed in the dial plate  2003 , and pointers  2004   b  such as the hour pointer and a minute pointer attached to the pointer shaft  2004   a , and operates the pointers  2004   b  above the dial plate  2003 . A battery (not shown) for operating the analog pointer mechanism  2004  is incorporated in, for example, the lower housing portion  2001   b.    
   The watch case  2002  comprises: a case main body  2002 A having a substantially cylindrical shape; band attaching portions  2002 B,  2002 B disposed protruding outward from a side surface of the case main body  2002 A in six o&#39;clock and twelve o&#39;clock directions and the like. 
   Two rectangular cutout portions  2020 A,  2020 A opened on a bottom surface side are disposed on the side surface of the case main body  2002 A. 
   The cutout portions  2020 A,  2020 A are disposed in positions substantially facing each other through the band attaching portion  2002 B in the side surface of the case main body  2002 A. The cutout portions  2020 A are disposed in positions closer to the band attaching portion  2002 B in the twelve o&#39;clock direction rather than to that in the six o&#39;clock direction. 
   Each of the band attaching portions  2002 B,  2002 B comprises: two pin fixing portions  2102 P facing each other at an interval between a three o&#39;clock direction and a nine o&#39;clock direction; and a band fixing pin  2002 P which is disposed between the pin fixing portions  2102 P and  2102 P and to which a band  2001 B is attached so that the watch  2100  can be attached to user&#39;s wrist. Each through opening  2030 A having a substantially rectangular shape is disposed in a region surrounded with the pin fixing portions  2102 P, the band fixing pin  2002 P, and the case main body  2002 A. 
   The antenna  2005  is disposed in the upper housing portion  2001   a , and comprises: a magnetic core  2005   a ; and a coil  2005   b  wound around this core  2005   a  as shown in  FIGS. 31 ,  32 . 
     FIG. 35  is a schematically sectional view along line V-V of  FIG. 33 . As shown in  FIG. 35 , the core  2005   a  comprises: for example, a central portion  2051  positioned in a central portion of the core  2005   a  in the longitudinal direction and having a substantial square pole shape; and end portions  2052 ,  2052  disposed in opposite end portions of the central portion  2051 . 
   Each end portion  2052  has a shape whose width broadens in a longitudinal direction from a boundary surface with the central portion  2051 . An outer shape of an end surface  2053  of the end portion  2052  substantially agrees with that of a cutout portion  2020 A disposed in the watch case  2002 . The surface of the end surface  2053  is a curved surface having a curvature which is equal to that of an outer peripheral surface of the case main body  2002 A. 
   Moreover, as shown in  FIG. 32 , a portion of the end portion  2052  positioned in an inner space of the case main body  2002 A in a side view has a thickness which is substantially equal to that of the central portion  2051 . A portion of the end portion superimposed on the case main body  2002 A thickens as the portion comes close to the end surface  2053 . That is, a sectional area of the end portion  2052  is set in such a manner as to increase as the portion superimposed on the case main body  2002 A comes close to the end surface  2053 . Therefore, an area of the end surface  2053  of the core  2005   a  is set to be larger than a sectional area of the central portion  2051 . 
   The antenna  2005  is disposed in the upper housing portion  2001   a  in such a manner that the axial line of the core  2005   a  is parallel to the back lid  2002   c  (or the dial plate  2003 ) between the lower housing portion  2001   b  and the dial plate  2003 . 
   Furthermore, the antenna  2005  is disposed in the watch case  2002  in such a manner as to fit the end surfaces  2053  of the antenna  2005  into the cutout portions  2020 A. That is, the antenna is disposed in such a manner that the opposite end surfaces  2053  of the core  2005   a  are exposed from the watch case  2002  to the outside. Moreover, an insulating material  2002   h  is disposed between the end portion  2052  positioned in the cutout portion  2020 A and the back lid  2002   c , the end surface  2053  and the case main body  2002 A are prevented from being configured into a continuous curved surface. The end portion  2052  is surrounded with a conductive member configured by the case main body  2002 A, and the side surface of the watch  2100  is configured in such a manner as to be prevented from being brought into a short-circuit state at a high frequency (in an alternating manner). The insulating material  2002   h  is brought into contact with the back lid  2002   c , and has a waterproof effect. Examples of the usable insulating material  2002   h  include a vinyl chloride-based material, a polyethylene-based material, and an ethylene propylene-based material. 
   A ferromagnetic material having a large permeability is preferably used in the core  2005   a  from a property that a magnetic flux is concentrated on a place having a less magnetic resistance. Examples of the ferromagnetic material include ferrite, an amorphous metal and the like. Above all, the amorphous metal is more preferable because its permeability is high and its strength is also high. A plurality of thin films of amorphous metals may be laminated, and the amorphous metal formed into a bulk configuration is more preferable in respect of a degree of freedom in a shape of the core  2005   a.    
   Specifically, examples of the bulked amorphous metal include an Fe-based alloy, a Pd-based alloy, a Zr-based alloy, an Ni-based alloy and the like. Examples of the Fe-based alloy include an Fe—M—B (M=Cr, W, Ta, Nb, Hf, Zr)-based alloy, an Fe—Co—RE—B (RE=Nb, Sm, Tb, Dy)-based alloy and the like. More specifically, the amorphous metal is formed of a composition such as Pd 40 Cu 30 Ni 10 P 20  or Fe 81 B 13 Si 14 C 2 . Moreover, when the melted alloy is worked into the bulk configuration by casting, an inner configuration is configured to be amorphous. 
   Here, the core  2005   a  is made of the amorphous metal. Therefore, even when the central portion  2051  is configured to be thinner than that of a core made of, for example, ferrite, an equal or more strength can be obtained. 
   The coil  2005   b  is configured by a conductor which transmits electricity, and, for example, a copper wire is usable. In each figure, to simplify description, a diameter of the coil  2005   b  is increased, and a shown winding number is small, but the diameter and the winding number of the coil  2005   b  can be appropriately set. 
   Next, a magnetic flux generated in the antenna  2005  will be described with reference to  FIG. 36  in a case where the antenna  2005  is disposed in a magnetic field (hereinafter referred to as the “signal magnetic field”) by a standard radio wave.  FIG. 36  is a view showing a function of a signal magnetic flux in the antenna. 
   When the antenna  2005  is disposed in the signal magnetic field in such a manner that the axial line of the core  2005   a  is parallel to a signal magnetic field direction, as shown in  FIG. 36 , a magnetic flux (hereinafter referred to as the “signal magnetic flux”) M 1  by the signal magnetic field is concentrated on the core  2005   a  having a permeability higher than that of a surrounding space. 
   When the signal magnetic flux M 1  is concentrated on the core  2005   a , the signal magnetic flux M 1  is interlinked with the coil  2005   b , and in the coil  2005   b , there is generated such an induced electromotive force V as to generate a magnetic flux (hereinafter referred to as the “generated magnetic flux”) in a direction to inhibit generation of the signal magnetic flux M 1  in the coil  2005   b  according to Lenz&#39;s law. 
   The induced electromotive force V generated in the coil  2005   b  is detected by a reception circuit (not shown) connected to the coil  2005   b . The reception circuit (not shown) includes a tuning capacitor (not shown) for tuning to a frequency (40 kHz or 60 kHz in Japan) of the standard radio wave to be received, or a loss resistance (not shown). It is to be noted that the reception circuit (not shown) is mounted on, for example, the circuit substrate  2006 . 
   The generated magnetic flux M 2  generated by the induced electromotive force V generates a magnetic field around the core  2005   a . This magnetic field reaches a metal member positioned in the vicinity of the antenna  2005 , that is, the watch case  2002  to generate an eddy current in the watch case  2002 . 
   Since an inner constitution of the watch  2100  is the same as that described with reference to  FIG. 4  in Embodiment 1, description thereof is omitted. 
   According to the above-described watch  2100 , the opposite end surfaces  2053 ,  2053  of the core  2005   a  which captures the standard radio wave are exposed from the watch case  2002  to the outside. Therefore, the standard radio wave can be captured directly by the opposite end surfaces  2053 ,  2053 , and the standard radio wave can be received efficiently and securely. 
   Moreover, the core  2005   a  which captures the standard radio wave has such a shape that an area of each of the opposite end surfaces  2053 ,  2053  of the core  2005   a  is larger than a sectional area of the central portion  2051  of the core  2005   a . Accordingly, the receiving sensitivity of the standard radio wave can be enhanced, receivable directions increase more, and therefore directivity can be relaxed. 
   Consequently, when the standard radio wave is received, there can be compensated for an energy loss by the eddy current generated in the vicinity of the antenna  2005 , and time can be corrected with a high precision. 
   Furthermore, when the core  2005   a  is formed of the amorphous metal, the core  2005   a  is provided with the high strength and permeability, and the radio wave can be captured more securely. Furthermore, when the core  2005   a  is configured by the bulked amorphous metal, a degree of freedom in forming the core  2005   a  can be improved. 
   It is to be noted that the antenna  2005   a  is horizontally symmetric with respect to the center of a length direction, but may be horizontally asymmetric as long as the end surfaces  2053  are exposed from the watch case  2002 . 
   Moreover, in the present embodiment, as shown in  FIG. 33 , a part of the watch case  2002  is cut out to expose the end surface  2053  to the outside. Moreover, the insulating material  2002   h  is disposed between the end portion  2052  positioned in the cutout portion  2020 A and the back lid  2002   c . This is because it is difficult to receive a received radio wave appropriately, when a periphery of the end portion  2052  comes in contact with a hollowed portion to cause the metal surrounding the hollowed portion to cause an alternating short circuit in a case where a part of the watch case  2002  made of the metal is hollowed to expose the end surface  2053 . Therefore, in a case where the watch case is formed of a nonconductive material (e.g., a resin or the like), the watch case may be hollowed to expose the end surface  2053 . Appropriate working such as prevention of the alternating short circuit may be performed to hollow the metal-made watch case  2002  and expose the end surface  2053 . 
   Furthermore, the insulating material  2002   h  is disposed only between the end portion  2052  positioned in the cutout portion  2020 A and the back lid  2002   c , but an insulating ring may be disposed on the whole contact surface between the end portion  2052  and the watch case  2002 . 
   Embodiment 8 
   Next, a watch  2200  according to Embodiment 8 of the present invention will be described.  FIG. 37  is a sectional view of the watch  2200  according to Embodiment 8 to which the present invention is applied. To describe the watch  2200 , the same constitution as that of the watch  2100  of Embodiment 7 is denoted with the same reference numerals, and description thereof is omitted. 
   As shown in  FIG. 37 , a watch case  2202  of the watch  2200  comprises: a case main body  2202 A having a substantially cylindrical shape; band attaching portions  2002 B,  2002 B disposed protruding outward from the side surface of the case main body  2202 A in six and twelve o&#39;clock directions and the like. 
   The side surface of the case main body  2202 A is provided with two rectangular cutout portions  2220 A,  2220 A opened on a bottom surface side. The cutout portions  2220 A,  2220 A are disposed in positions substantially facing each other through the band attaching portion  2002 B. 
   An antenna  2205  of the watch  2200  comprises: a magnetic core  2205   a ; and a coil  2005   b  wound around this core  2205   a . The core  2205   a  comprises: a central portion  2051  positioned in a central portion of the core  2205   a  in the longitudinal direction and having a schematic square pole shape; and end portions  2252 ,  2252  disposed on opposite end portions of the central portion  2051 . 
   Each end portion  2252  comprises: an enlarged width portion  2252   a  whose width broadens apart from a boundary surface with the central portion  2051  in a plan view in the longitudinal direction; and an extended portion  2252   b  extended from a tip of the enlarged width portion  2252   a  further in the six o&#39;clock direction. An outer shape of an end surface  2253  of each end portion  2252  substantially agrees with a shape of the cutout portion  2220 A disposed in the watch case  2202 , and the surface of the end surface  2253  has a curvature which is equal to that of an outer peripheral surface of the case main body  2202 A. 
   A sectional area of the end portion  2252  is provided in such a manner as to broaden as it departs from the central portion  2051 , that is, it comes close to the end surface  2253 . Therefore, an area of the end surface  2253  of the core  2205   a  is provided in such a manner as to be larger than a sectional area of the central portion  2051 . 
   The antenna  2205  is disposed in such a manner that the end portion  2252  of the antenna  2205  is fit into the cutout portion  2220 A. That is, the antenna is disposed in such a manner that the opposite end surfaces  2253 ,  2253  of the core  2205   a  are exposed from the watch case  2202  to the outside. Moreover, the end surface  2253  and the case main body  2202 A configure a continuous curved surface to configure the side surface of the watch  2200 . 
   According to the watch  2200 , needless to say, effects similar to those of the watch  2100  are obtained. Since the end portion  2252  of the antenna  2205  is provided with the extended portion  2252   b , an area exposed from the case main body  2202 A can be enlarged as compared with the antenna  2205  of Embodiment 7. Therefore, the area of each of the opposite end surfaces  2253  of the core  2205   a  which captures the standard radio wave is provided in such a manner as to be sufficiently larger than the sectional area of the central portion  2051 . Consequently, the receiving sensitivity of the antenna  2205  can be improved more. Additionally, a receivable direction largely broadens, and directivity can be relaxed. 
   Embodiment 9 
   Next, a watch  2300  according to Embodiment 9 of the present invention will be described.  FIG. 38  is a sectional view of the watch  2300  according to Embodiment 9 to which an electronic device of the present invention is applied. To describe the watch  2300 , the same constitution as that of the watch  2100  of Embodiment 7 is denoted with the same reference numerals, and description thereof is omitted. 
   As shown in  FIG. 38 , a watch case  2302  of the watch  2300  comprises: a case main body  2302 A having a substantially cylindrical shape. 
   A side surface of the case main body  2302 A is provided with two rectangular cutout portions  2320 A,  2320 A opened on a bottom surface side. The cutout portions  2320 A,  2320 A are disposed in positions in band attaching directions including six and twelve o&#39;clock directions in the case main body  2302 A. 
   An antenna  2305  of the watch  2300  comprises: a magnetic core  2305   a ; and a coil  2005   b  wound around this core  2305   a . The core  2305   a  comprises: a central portion  2051  positioned in a central portion of the core  2305   a  in the longitudinal direction and having a schematic square pole shape; and end portions  2352 ,  2352  disposed on opposite end portions of the central portion  2051 . 
   Each end portion  2352  comprises: an enlarged width portion  2352   a  whose width broadens in a substantially triangular shape in a plan view extending outward from each end of the central portion  2051  in a longitudinal direction; a rectangular portion  2352   b  having a substantially rectangular shape in a plan view extending outward from this enlarged width portion  2352   a  in a longitudinal direction of the core  2305   a ; and two pin fixing portions  2302 P,  2302 P protruding outward from the rectangular portion  2352   b  in the longitudinal direction of the core  2305   a  and facing each other at an interval in three and nine o&#39;clock directions. A vertically sectional shape in the rectangular portion  2352   b  substantially agrees with a shape of the cutout portion  2320 A. Therefore, an area of each end surface  2353  of the core  2305   a  is provided to be larger than a sectional area of the central portion  2051 . 
   Moreover, between the pin fixing portions  2302 P,  2302 P, there is attached the band fixing pin  2002 P through which a band  2001 B is attached so that the watch  2300  can be attached to user&#39;s wrist. The pin fixing portions  2302 P and the band fixing pin  2002 P configure a band attaching portion  2302 B. A through opening  2330 A having a schematically rectangular shape is formed in a region surrounded with the pin fixing portions  2302 P, the band fixing pin  2002 P, and the case main body  2302 A. 
   The antenna  2305  is disposed in a position inside the watch case  2302 , in which the end portions  2352  of the antenna  2305  are fit into cutout portions  2320 A, and the rectangular portions  2352   b  of the end portions  2352  protrude from the case main body  2302 A. That is, the antenna is disposed in such a manner that the opposite end surfaces  2353 ,  2353  of the core  2305   a  are exposed from the watch case  2302  toward the outside. 
     FIG. 39  shows a function of a signal magnetic flux which passes through the core  2305   a  of the antenna  2305 . A signal magnetic flux M 1  enters the core  2305   a  through the end surfaces  2353  to pass through the core  2305   a . In this case, a generated magnetic flux M 2  is generated in the core  2305   a  by an induced electromotive force V generated in the coil  2005   b . Moreover, an eddy current is generated by the generated magnetic flux M 2  in the vicinity of in the watch case  2302 . 
   According to the watch  2300 , needless to say, effects similar to those of the watch  2100  can be obtained. Since the band  2001 B can be connected to the band fixing pins  2002 P disposed on the opposite ends of the core  2305   a  of the antenna  2305 , the exposed portions of the core  2305   a  can be recognized as the band attaching portions  2302 B by a user. Even in a case where an appearance of the core  2305   a  is different from that of the watch case  2302 , the difference is not conspicuous. While the appearance is secured, a high receiving sensitivity can be realized. 
   Embodiment 10 
   Next, a watch  2400  will be described according to Embodiment 10 for carrying out the present invention.  FIG. 40  is a sectional view of the watch  2400  according to Embodiment 10 to which an electronic device of the present invention is applied. To describe the watch  2400 , the same constitution as that of the watch  2300  of Embodiment 9 is denoted with the same reference numerals, and description thereof is omitted. 
   As shown in  FIG. 40 , a watch case  2402  of the watch  2400  comprises: a case main body  2402 A having a substantially cylindrical shape. 
   A side surface of the case main body  2402 A is provided with two rectangular cutout portions  2420 A,  2420 A opened on a bottom surface side. The cutout portions  2420 A,  2420 A are disposed in positions in six and twelve o&#39;clock directions in the case main body  2402 A. 
   An antenna  2405  of the watch  2400  comprises: a magnetic core  2405   a ; and a coil  2005   b  wound around this core  2405   a . The core  2405   a  comprises: a central portion  2051  positioned in a central portion of the core  2405   a  in the longitudinal direction and having a schematic square pole shape; and end portions  2452 ,  2452  disposed on opposite end portions of the central portion  2051 . 
   Each end portion  2452  comprises: an enlarged width portion  2452   a  whose width broadens in a substantially triangular shape in a plan view extending outward from each side of the central portion  2051  in a longitudinal direction; extended portions  2452   b ,  2452   b  extending from a tip of the enlarged width portion  2452   a  in three and nine o&#39;clock directions, respectively; a rectangular portion  2452   c  having a substantially rectangular shape extending outward from the enlarged width portion  2452   b  in a longitudinal direction; and two pin fixing portions  2402 P,  2402 P protruding outward from the rectangular portion  2452   b  in the longitudinal direction of the core  2405   a  and facing each other at an interval in three and nine o&#39;clock directions. Therefore, an area of each end surface  2453  of the core  2405   a  is configured to be larger than a sectional area of the central portion  2051 . 
   Outer shapes of the extended portions  2452   b ,  2452   b  substantially agree with a shape of the cutout portion  2420 A disposed in the watch case  2402 . An outer surface of each of the extended portions  2452   b ,  2452   b  is a curved surface having a curvature equal to that of an outer peripheral surface of the case main body  2402 A. 
   Moreover, a band fixing pin  2002 P is attached between the pin fixing portions  2402 P,  2402 P to fix a band  2001 B to the pin fixing portions  2402 P,  2402 P, so that the watch  2400  can be attached to user&#39;s wrist by the bands  2001 B. The pin fixing portions  2402 P and the band fixing pin  2002 P configure a band attaching portion  2402 B. A through opening  2430 A having a schematically rectangular shape is formed in a region surrounded with the pin fixing portions  2402 P, the band fixing pin  2002 P, and the case main body  2402 A. 
   The antenna  2405  is disposed in a position inside the watch case  2402  in which the extended portions  2452   b  of the end portions  2452  of the antenna  2405  are fit into the cutout portions  2420 A, the extended portions  2452   b  and the side surface of the case main body  2402 A continuously configure a curved surface, and the rectangular portions  2452   c  protrude from the case main body  2402 A. 
   According to the watch  2400 , needless to say, effects similar to those of the watch  2100  can be obtained. Since the band  2001 B can be connected to the band fixing pins  2002 P in the antenna  2405 , the exposed portions of the core  2405   a  can be recognized as the band attaching portions  2402 B by a user. Even in a case where an appearance of the core  2405   a  is different from that of the watch case  2402 , the difference is not conspicuous. While the appearance is secured, a high receiving sensitivity can be realized. 
   Furthermore, since the end portions  2452  of the antenna  2405  are provided with the extended portions  2452   b , an area exposed from the case main body  2402 A can be enlarged as compared with the antenna  2305  of Embodiment 3. Therefore, an area of each of the opposite end surfaces  2453  of the core  2405   a  which captures a standard radio wave is provided in such a manner as to be sufficiently larger than a sectional area of the central portion  2051 . A receiving sensitivity of the antenna  2405  can be improved more, a receivable direction largely spreads, and directivity can be relaxed more. 
   Embodiment 11 
   Next, a watch  2500  will be described according to Embodiment 11 for carrying out the present invention.  FIG. 41  is a sectional view of the watch  2500  according to Embodiment 11 to which an electronic device of the present invention is applied.  FIG. 42  is a sectional view taken along a line XLII-XLIII in  FIG. 41 . To describe the watch  2500 , the same constitution as that of the watch  2100  of Embodiment 7 is denoted with the same reference numerals, and description thereof is omitted. 
   As shown in  FIGS. 41 and 42 , a watch case  2502  of the watch  2500  comprises: a case main body  2502 A having a substantially cylindrical shape; band attaching portions  2502 B disposed protruding from a side surface of the case main body  2502 A in six and twelve o&#39;clock directions and the like. 
   Two rectangular cutout portions  2520 A,  2520 A opened on a bottom surface side are disposed in the side surface of the case main body  2502 A. 
   Each of the band attaching portions  2502 B,  2502 B comprises: two pin fixing portions  2502 P facing each other at an interval in three and nine o&#39;clock directions; and a band fixing pin  2002 P which is disposed between the pin fixing portions  2502 P and  2502 P and to which a band  2001 B is attached so that the watch  2500  can be attached to user&#39;s wrist. Each through opening  2530 A having a substantially rectangular shape is disposed in a region surrounded with the pin fixing portions  2502 P, the band fixing pin  2002 P, and a case main body  2502 A. Each cutout portion  2520 A is provided in a root portion of the band attaching portion  2502 B in the case main body  2502 A, and disposed in such a manner as to face the opening  2530 A of the band attaching portion  2502 B. 
   An antenna  2505  comprises: a magnetic core  2505   a ; and a coil  2005   b  wound around this core  2505   a . The core  2505   a  comprises: a central portion  2051  positioned in a central portion of the core  2505   a  in the longitudinal direction and having a substantial square pole shape; and end portions  2552 ,  2552  disposed in opposite end portions of the central portion  2051 . 
   Each end portion  2552  slightly bends in a three o&#39;clock direction in a boundary surface with respect to the central portion  2051 , and bends in a direction substantially parallel to an axial direction of the coil  2005   b  in a root portion of the band attaching portion  2502 B. An area of an end surface  2553  of the end portion  2552  is formed to be larger than a sectional area of the central portion  2051 . An insulating material  2502   h  is disposed between the end portion  2552  positioned in the cutout portion  2520 A and a back lid  2002   c . Accordingly, the end surface  2553  and the case main body  2502 A are prevented from being configured into a continuous curved surface. The end portion  2552  is surrounded with a conductive member configured by the case main body  2502 A, and the side surface of the watch  2500  is configured in such a manner as to be prevented from being brought into a short-circuit state at a high frequency (in an alternating manner). The insulating material  2502   h  is brought into contact with the back lid  2002   c , and has a waterproof effect. Examples of the usable insulating material  2502   h  include a vinyl chloride-based material, a polyethylene-based material, and an ethylene propylene-based material. 
   The antenna  2505  is disposed in such a manner that the end portions  2552  are fitted into the cutout portions  2520 A of the watch case  2502  and the end surface  2553  are exposed in the openings  2530 A. 
   Therefore, when the band  2001 B is attached to the band fixing pins  2002 P of the band attaching portions  2502 B, the band  2001 B face the end surfaces  2553  exposed facing the openings  2530 A. 
   According to the watch  2500 , needless to say, effects similar to those of the watch  2100  are obtained. The end surfaces  2553  of the antenna  2505  face the bands  2001 B attached to the band fixing pins  2002 P. Therefore, when the bands  2001 B are attached to the band fixing pins  2002 P, the opposite end surfaces  2553 ,  2553  of the core  2505   a  are obstructed by the bands  2001 B so that they are not easily seen from the outside. Even if an appearance of the core  2505   a  is different from that of the watch case  2502 , the difference is not conspicuous. Without impairing the appearance, the core  2505   a  can be exposed. 
   Embodiment 12 
   Next, Embodiment 12 for carrying out the present invention will be described.  FIG. 43  is a sectional view of a watch  2600  as Embodiment 12 to which an electronic device of the present invention is applied.  FIG. 44  is a sectional view taken along a line XLIV-XLIV in  FIG. 43 . To describe the watch  2600 , the same constitution as that of the watch  2100  of Embodiment 7 is denoted with the same reference numerals, and description thereof is omitted. 
   As shown in  FIGS. 43 and 44 , a watch case  2602  of the watch  2600  comprises: a case main body  2602 A having a substantially cylindrical shape; band attaching portions  2602 B disposed protruding from a side surface of the case main body  2602 A in six and twelve o&#39;clock directions and the like. 
   Two rectangular cutout portions  2620 A,  2620 A opened on a bottom surface side are provided in a side surface of the case main body  2602 A. 
   Each of the band attaching portions  2602 B,  2602 B comprises: two pin fixing portions  2602 P,  2602 P facing each other at an interval in three and nine o&#39;clock directions; and a band fixing pin  2002 P which is disposed between the pin fixing portions  2602 P and  2602 P and to which a band  2001 B is attached so that the watch  2600  can be attached to user&#39;s wrist. Each through opening  2630 A having a substantially rectangular shape is disposed in a region surrounded with the pin fixing portions  2602 P, the band fixing pin  2002 P, and the case main body  2602 A. 
   An antenna  2605  comprises: a magnetic core  2605   a ; and a coil  2005   b  wound around this core  2605   a.    
   Furthermore, the core  2605   a  comprises: first magnetic members  2615  disposed inside the watch case  2602 ; second magnetic members  2625  exposed from the watch case  2602 ; and connecting members  2635  which are configured by magnetic materials and which connect the first magnetic members  2615  to the second magnetic members  2625  abutting on the first magnetic members. 
   The first magnetic members  2615  comprise: a central portion  2615   a  positioned substantially in a central portion and substantially having a square pole shape; and bent portions  2615   b ,  2615   b  which are disposed on opposite end portions of the central portion  2615   a  and which obliquely bend in a three/nine o&#39;clock direction in boundary surfaces with respect to the central portion  2615   a  and which bend in a direction substantially parallel to a longitudinal direction of the central portion  2615   a  in root portions of the band attaching portions  2602 B. End portions of the bent portions  2615   b  are provided with screw holes  2615   c  for passing the connecting members  2635 . 
   Each of the second magnetic members  2625  has a substantially rectangular parallelepiped shape, and a sectional area of the member is configured to be larger than a sectional area of the bent portion  2615   b  of the first magnetic member  2615 . A screw hole  2615   d  corresponding to the screw hole  2615   c  of the bent portion  2615   b  is disposed in an abutment surface of the second magnetic member  2625  which abuts on the first magnetic member  2615  which faces the opening  2630 A. Moreover, the connecting members  2635  are passed through the screw holes  2615   c  in the first magnetic members  2615 , and inserted into the screw holes  2615   d  of the second magnetic members  2625 . Accordingly, the first magnetic members  2615  are connected to the second magnetic members  2625  in a state in which they abut on each other. 
   That is, each end portion  2652  of the core  2605   a  comprises: the bent portion  2615   b  of the first magnetic member  2615 ; the second magnetic member  2625 ; and the connecting member  2635 . An end surface  2653  of each end portion  2652  comprises an outer surface of the second magnetic member  2625  which faces the opening  2630 A. Therefore, an area of the end surface  2653  is provided in such a manner as to be larger than a sectional area of the central portion  2615   a.    
   Moreover, an insulating material  2602   h  is disposed between the end portion  2652  positioned in the cutout portion  2620 A and a back lid  2002   c . Accordingly, the end surface  2653  and the case main body  2602 A are prevented from being configured into a continuous curved surface. The end portion  2652  is surrounded with a conductive member configured by the case main body  2602 A, and the side surface of the watch  2600  is configured in such a manner as to be prevented from being brought into a short-circuit state at a high frequency (in an alternating manner). The insulating material  2602   h  is brought into contact with the back lid  2002   c , and has a waterproof effect. Examples of the usable insulating material  2602   h  include a vinyl chloride-based material, a polyethylene-based material, and an ethylene propylene-based material. 
   Any of the first magnetic members  2615 , the second magnetic members  2625 , and the connecting members  2635  may be a magnetic member, or may be different types of members having, for example, different permeability. As the connecting member, for example, a bolt, a screw or the like is usable, and another member having a preferable connecting function can be appropriately used. 
   According to the watch  2600 , needless to say, effects similar to those of the watch  2100  are obtained. The first magnetic members  2615  are connected to the second magnetic members  2625  by the connecting members  2635  to form the core  2605   a  with the watch case  2602  being sandwiched between the first magnetic members  2615  and the second magnetic members  2625 . 
   Therefore, a degree of freedom in structure design can be enhanced as compared with a core as a single member. A design property is improved, or the watch can be structured in such a manner as to keep air tightness with respect to the watch case  2602 . 
   (Modification) 
   A watch  2700  as a modification of Embodiment 12 is shown in  FIGS. 45 and 46 .  FIG. 45  is a sectional view of the watch  2700 .  FIG. 46  is a sectional view taken along a line XLVI-XLVI in  FIG. 45 . A constitution similar to that of Embodiment 12 is denoted with the same reference numerals, and description thereof is omitted. 
   An antenna  2705  comprises: a magnetic core  2705   a ; and a coil  2005   b  wound around this 
   The core  2705   a  comprises: a first magnetic member  2715  disposed inside a watch case  2602 ; a second magnetic member  2725  exposed from the watch case  2602 ; and a connecting member  2635  configured by a magnetic material for connecting the first magnetic member  2715  to the second magnetic member  2725  in a state in which the first magnetic member abuts on the second magnetic member. 
   The first magnetic member  2715  is formed of: a central portion  2715   a  positioned substantially in a central portion and substantially having a square pole shape; and bent portions  2715   b  which are disposed in opposite end portions of the central portion  2715   a  and which obliquely bend in a three/nine o&#39;clock direction in boundary surfaces between the bent portions and the central portion  2715   a  and which bend in a direction substantially parallel to a longitudinal direction of the central portion  2715   a  in root portions of band attaching portions  2602 B. Screw holes  2715   c  for passing the connecting members  2635  are disposed in end portions of the bent portions  2715   b.    
   Screw holes  2715   d  corresponding to the screw holes  2715   c  of the bent portions  2715   b  are disposed in abutment surfaces of the second magnetic members  2725  which abut on the first magnetic member  2715  facing openings  2730 A. Moreover, when the connecting members  2635  are passed through the screw holes  2715   d  of the second magnetic member  2725 , and inserted into the screw holes  2715   c  of the first magnetic members  2715 , the first magnetic member  2715  is connected to the second magnetic member  2725  in an abutting state. 
   That is, each end portion  2752  of the core  2705   a  comprises the bent portion  2715   b  of the first magnetic member  2715 , the second magnetic member  2725 , and the connecting member  2635 . An end surface  2753  of the end portion  2752  comprises an outer surface of the second magnetic member  2725  disposed in the opening  2730 A. Therefore, an area of the end surface  2753  is provided in such a manner as to be larger than that of the central portion  2715   a.    
   Moreover, an insulating material  2602   h  is disposed between the end portion  2752  positioned in a cutout portion  2620 A and a back lid  2002   c . Accordingly, the end surface  2753  and a case main body  2602 A are prevented from being configured into a continuous curved surface. The end portion  2752  is surrounded with a conductive member configured by the case main body  2702 A, and the side surface of the watch  2700  is configured in such a manner as to be prevented from being brought into a short-circuit state at a high frequency (in an alternating manner). Examples of the usable insulating material  2602   h  include a vinyl chloride-based material, a polyethylene-based material, and an ethylene propylene-based material. 
   According to the watch  2700 , needless to say, effects similar to those of the watch  2600  are obtained. Since the connecting members  2635  can be tightened from the side of the second magnetic member  2725  configuring the core  2705   a , an operation of fastening the second magnetic members  2625  can be performed more easily. 
   It has been described in the embodiments of the present invention that the present invention is applied as the electronic device to the watch type radio-wave clock, but the present invention is not limited to this application. The present invention may be applied to, for example, an electronic device to be mounted in a car, a portable radio terminal or the like. 
   Moreover, the materials of the cores in Embodiments 8 to 12 are the same as those in Embodiment 7. 
   According to the above-described inventions described in Embodiments 7 to 12, the opposite end surface of the core which captures the radio wave are exposed from the device case to the outside. Therefore, the radio wave can be captured directly by the opposite end surfaces without being interrupted by the device case, and the radio wave can be received efficiently and securely. Accordingly, it is possible to enhance the receiving sensitivity of the antenna in the device case. 
   Moreover, since the core is made of the amorphous metal, the core is provided with the high strength and permeability, and the radio wave can be captured more securely. 
   Furthermore, the area of each end surface of the core which captures the radio wave is larger than the sectional area of the central portion of the core. According to this shape, the receiving sensitivity of the radio wave can be improved more, and the receivable directions increase. Therefore, the directivity can be relaxed, and the radio wave can be received more efficiently and securely. 
   Additionally, according to the inventions described in Embodiments 9 and 10, even in a case where the band attaching portion of the core is connected to the band, and the appearance of the core is different from that of the device case, the difference is not conspicuous, and the core can be exposed without impairing the appearance. 
   Moreover, according to the invention described in Embodiment 11, the opposite end surfaces of the core exposed from the device case to the outside face the band attached to the band attaching portion. Therefore, in a case where the band is attached to the band attaching portion, the opposite end surfaces of the core are accordingly obstructed by the band and are not easily seen from the outside, and the appearance of the core is different from that of the device case, the difference is not conspicuous, and the core can be exposed without impairing the appearance. 
   Furthermore, according to the invention described in Embodiment 12, the first magnetic member is connected to the second magnetic member by the connecting member to configure the core with the device case being sandwiched between the first magnetic member and the second magnetic member. Therefore, the degree of freedom in structure design can be enhanced as compared with the single-member core. The core can be structured in such a manner as to improve its design property and keep the air tightness with respect to the device case. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications and may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.