Patent Publication Number: US-2010109968-A1

Title: Antenna device and portable terminal device

Description:
TECHNICAL FIELD 
     The present invention relates to an antenna device preferably suitable for a miniaturization that can share an antenna between communication systems having different frequency bands and a portable terminal device provided with the antenna device. 
     BACKGROUND ART 
     In recent years, as a portable terminal device for reading information written in a card or writing information in the card, a reader and writer is proposed that can read and write, for instance, a non-contact IC card or an RF tag (For instance, see patent literature 1). 
     Namely, in the reader and writer, for instance, as shown in  FIG. 24 , the portable terminal device  100  includes a reader and writer part  101  that reads electronic information of the non-contact IC card or a non-contact IC tag (refer them together to as an RFID)  200  through an antenna  105 , a memory part  102  that holds the electronic information of the RFID  200  read by the reader and writer part  101  and a charging control part  104  that controls the charging of a battery  103 . In the reader and writer, when the battery  103  is charged, an electric signal inputted from a coil electromagnetically connected to a charging power supply device  300  to form the antenna  105  is allowed to be inputted to the charging control part  104 . Patent literature 1: JP-A-2001-307032 
     DISCLOSURE OF THE INVENTION 
     Problems that the Invention is to Solve 
     As an object on which the electronic information is read and written by the above-described reader and writer, the RFID (for instance, 950 MHz) or the like is exemplified that carries out a radio communication in a frequency band near a frequency band used mainly by a portable telephone. Further, in recent years, as one kind of the non-contact IC card, for instance, a non-contact communication system that carries out a communication in a frequency band greatly lower than the frequency band used in the portable telephone has been developed and started to be used. 
     However, such a reader and writer does not structurally meet a process for reading, for instance, a non-contact IC card of a different communication system depending on a low frequency band such as FeliCa (a registered trademark) of 13.56 MHz by one antenna. (Felica is a non-contact IC card technical system in which Sony Corporation developed). 
     Therefore, for the communication system of the different frequency band, since an exclusive antenna device meeting the above-described communication system needs to be separately provided, the reader and writer part is enlarged. Thus, the reader and writer is not convenient as a portable and compact device. 
     The present invention is devised by considering the above-described circumstances and it is an object of the present invention to provide an antenna device that can be used for radio communication systems having different frequency bands by sharing a single antenna, and accordingly, is suitable for a miniaturization and a portable terminal device provided with the antenna device. 
     Means for Solving the Problems 
     Namely, in an antenna device of the present invention having: a spiral antenna formed in a spiral shape; a first feeding part connected to and feeding an electric power to a first radio system operating in a first frequency band; and a second feeding part connected to and feeding an electric power to a second radio system operating in a second frequency band, the antenna device includes: a feeding part switch unit that switches a connecting state of the first feeding part or the second feeding part and an outermost periphery or an inner periphery inside the outermost periphery of the spiral antenna, and a grounding switch unit that switches a prescribed point of the outermost periphery of the spiral antenna t&amp; either an opening or a grounding. The spiral antenna is formed in such a way that the width of a conductor forming the spiral antenna is different in its dimension between the outermost periphery and the inner periphery inside the outermost periphery. 
     An antenna device of the present invention may be formed in such a way that the feeding part switch unit is formed with a first switch selectively connecting the first feeding part or the second feeding part to a starting point of the outermost periphery of the spiral antenna or connects the first feeding part or the second feeding part to an end point of the inner periphery, and the first switch is operated so that the spiral antenna may operate as a spiral loop antenna or a plate shaped antenna using the outer periphery. 
     An antenna device of the present invention may be formed in such a way that the grounding switch unit is formed with a second switch that may switch the prescribed point of the outermost periphery of the spiral antenna either to an opening or a grounding, and the spiral antenna operates as the plate shaped antenna for a UHF band as a high frequency band or the spiral loop antenna for 13.56 MHz band as a low frequency band. 
     An antenna device of the present invention may be formed in such a way that the feeding part switch unit has the first switch that selectively connects the starting point of the outermost periphery of the spiral antenna to the first feeding part or the second feeding part and a third switch that selectively switches to connect the starting point of the outermost periphery of the spiral antenna to the end point of the outermost periphery or to open both the starting point and the end point of the outermost periphery of the spiral antenna, and when the starting point of the outermost periphery of the spiral antenna is connected to the radio system for the high frequency band of the first radio system or the second radio system by the first switch, the starting point of the outermost periphery of the spiral antenna is connected to the end point of the outermost periphery by the third switch, on the other hand, when the starting point of the outermost periphery of the spiral antenna is connected to the radio system for the low frequency band of the first radio system or the second radio system by the first switch, the starting point of the outermost periphery of the spiral antenna is opened to the end point of the outermost periphery of the spiral antenna by the third switch. 
     An antenna device of the present invention may further include: a plate shaped conductor positionally overlapped on an upper part or a lower part of the outermost periphery of the spiral antenna with an insulating layer held between the conductor and the spiral antenna and having one end connected to the end point of the inner periphery of the spiral antenna. The plate shaped conductor may be electro-statically connected to the outermost periphery, and the grounding switch unit and the feeding part switch unit are switched depending on a used communication system so that the spiral loop antenna and the plate shaped antenna using the outermost periphery may be switched. 
     An antenna device of the present invention may be formed in such a way that the plate shaped conductor is provided on the outermost periphery of the spiral antenna and a part of the inner periphery, the upper part or the lower periphery or both of them under a state the conductor is insulated from them, the outermost periphery of the spiral antenna and the inner periphery may be electro-statically connected to the conductor, and the grounding switch unit and the feeding part switch unit are switched depending on a used communication system so that the spiral loop antenna and the plate shaped antenna using the outermost periphery may be switched. 
     In an antenna device having: a spiral antenna formed in a spiral shape; and a feeding part that feeds an electric power to the spiral antenna, the spiral antenna is formed with a conductor whose width is different in its dimension between an outermost periphery and an inner periphery inside the outermost periphery. The antenna device includes: a plate shaped metal conductor provided on an upper part or a lower part of the spiral antenna, insulated from them and formed substantially in the shape of a character   with a center bored; the metal conductor being formed to be electro-statically connected to the spiral antenna, and the outermost periphery of the spiral antenna or the metal conductor being grounded at a prescribed point, and a feeding part switch unit that switched a connecting state between the feeding part and the outermost periphery or the inner periphery of the spiral antenna. The feeding part switch unit is switched depending on a used communication system so that the spiral antenna may be switched as an antenna of different frequency bands. 
     In an antenna device of the present invention having: a spiral antenna formed in a spiral shape; and a feeding part that feeds an electric power to the spiral antenna, the spiral antenna is formed with a conductor whose width is different in its dimension between an outermost periphery and an inner periphery inside the outermost periphery. The antenna device includes: a plate shaped metal conductor with a central part bored which is provided outside the spiral antenna under a state that the conductor is connected integrally in parallel with the spiral antenna; a grounding switch unit that may switch a prescribed point of the outermost periphery of the spiral antenna to either an opening or a grounding; and a feeding part switch unit that switches a connecting state between the feeding part and the outermost periphery or the inner periphery of the spiral antenna. The feeding part switch unit is switched depending on a used communication system so that the spiral antenna may be switched and used as an antenna of different frequency bands by using the inductance of the inner periphery of the spiral antenna. 
     A portable terminal device of the present invention is provided with the antenna device described in any one of the above-described items. 
     ADVANTAGE OF THE INVENTION 
     According to the present invention, an antenna device and a portable terminal device may be provided that can be used in radio communication systems in two different kinds of frequency bands by sharing a single antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a potable terminal device having an antenna device according to the present invention. 
         FIG. 2  is a schematic structural diagram of an antenna device according to a first embodiment of the present invention. 
         FIG. 3  is an explanatory view showing a basic structure of an inverted F antenna of the antenna device according to the present invention. 
         FIG. 4  is an explanatory view showing an operation when the antenna device according to the first embodiment is used as a first radio system. 
         FIG. 5  is an explanatory view showing an operation when the antenna device according to the first embodiment is used as a second radio system. 
         FIG. 6  is a schematic structural diagram of an antenna device according to a second embodiment of the present invention. 
         FIG. 7  is an explanatory view showing an operation when the antenna device according to the second embodiment is used as a first radio system. 
         FIG. 8  is an explanatory view showing an operation when the antenna device according to the second embodiment is used as a second radio system. 
         FIG. 9(A)  is a schematic structural diagram of an antenna device according to a third embodiment of the present invention and  FIG. 9  (B) is a sectional view taken along a line IX-IX of  FIG. 9(A) . 
         FIG. 10(A)  is an explanatory view showing an operation when the antenna device according to the third embodiment is used as a first radio system and  FIG. 10(B)  is a sectional view thereof. 
         FIG. 11(A)  is an explanatory view showing an operation when the antenna device according to the third embodiment is used as a second radio system and  FIG. 11(B)  is a sectional view thereof. 
         FIG. 12  (A) is a schematic structural diagram of an antenna device according to a fourth embodiment of the present invention and  FIG. 12  (B) is a sectional view taken along a line IX-IX of  FIG. 12(A) . 
         FIG. 13(A)  is an explanatory view showing an operation when the antenna device according to the fourth embodiment is used as a first radio system and  FIG. 13(B)  is a sectional view thereof. 
         FIG. 14(A)  is an explanatory view showing an operation when the antenna device according to the fourth embodiment is used as a second radio system and  FIG. 14(B)  is a sectional view thereof. 
         FIG. 15  (A) is a schematic structural diagram of an antenna device according to a fifth embodiment of the present invention and  FIG. 15(B)  is a sectional view taken along a line IX-IX of  FIG. 15(A) . 
         FIG. 16(A)  is an explanatory view showing an operation when the antenna device according to the fifth embodiment is used as a first radio system and  FIG. 16(B)  is a sectional view thereof. 
         FIG. 17(A)  is an explanatory view showing an operation when the antenna device according to the fifth embodiment is used as a second radio system and  FIG. 17(B)  is a sectional view thereof. 
         FIG. 18(A)  is a schematic structural diagram of an antenna device according to a sixth embodiment of the present invention and  FIG. 18(B)  is a sectional view taken along a line IX-IX of  FIG. 18(A) . 
         FIG. 19  is a circuit diagram of the antenna device according to the sixth embodiment. 
         FIG. 20  is an exploded view showing an antenna part of the antenna device according to the sixth embodiment. 
         FIG. 21(A)  is an explanatory view showing an operation when the antenna device according to the sixth embodiment is used as a first radio system and  FIG. 21(B)  is a sectional view thereof. 
         FIG. 22(A)  is an explanatory view showing an operation when the antenna device according to the sixth embodiment is used as a second radio system and  FIG. 22(B)  is a sectional view thereof. 
         FIG. 23  is a schematic structural diagram showing a modified example of the embodiment of the present invention. 
         FIG. 24  is a block diagram showing a usual antenna device. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS AND SIGNS&gt; 
     
         
           10  portable telephone (portable terminal device) 
           11  upper casing 
           12  lower casing 
           14  switch for switching 
           2  to  7  first to sixth antenna device 
           21  spiral antenna 
           21 A outermost winding part (outermost periphery) 
           21 B inner peripheral winding part (inner periphery) 
           21 C wiring part 
           21 D end conductor part 
           21 A 1  first side part 
           21 A 4  fourth side part 
           21 B inner peripheral winding part 
           21 B 1  outermost side part 
           212  lead-out line 
           212  lead-out line 
           213  lead-out line 
           22  feeding part switch unit 
           22 B first feeding terminal 
           22 C second feeding terminal 
           22 A switching terminal 
           23  grounding switch unit 
           23 A switching terminal 
           23 B grounding terminal 
           23 C opening terminal 
           24  feeding part 
           241  first feeding part 
           242  second feeding part 
         A inverted F antenna 
         M main part (main body part) 
         P feeding line 
         S short-circuit line 
         SW 1  first switch 
         SW 2  second switch 
         SW 3  third switch 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Now, embodiments of the present invention will be described below in detail by referring to the attached drawings. 
     First Embodiment 
       FIG. 1  shows a portable telephone  10  according to a first embodiment of the present invention. The portable telephone  10  includes an upper casing  11  and a lower casing  12  and a hinge part  13  for connecting the casings so as to freely rotate. In the upper casing  11 , a first antenna device  2  according to the first embodiment is provided. 
     As shown in  FIG. 2 , the first antenna device  2  includes a spiral antenna  21  formed in a spiral shape, a feeding part switch unit  22  for switching a connection of the spiral antenna  21  and a below-described feeding part  24 , a grounding switch unit  23  provided in the outermost periphery of the spiral antenna  21  and the feeding part  24  having first and second feeding parts  241  and  242  and connected to the spiral antenna  21 . 
     The spiral antenna  21  is formed so as to operate not only as a loop antenna (refer it to as a “spiral loop antenna” hereinafter) using an entire part of the spiral antenna (for a low frequency band), but also as an inverted F antenna A (see  FIG. 3 ) (for a high frequency band) using an outermost peripheral part. Further, the spiral antenna  21  is formed in such a way that the width of a conductor is different in its dimension between a conductor part of an outermost periphery (refer it to as an “outermost winding part  21 A”, hereinafter) and a conductor part of an inner periphery (refer it to as an “inner peripheral winding part  21 B”, hereinafter). That is, the width of the inner peripheral winding part  21 B is narrowed relative to the outermost winding part  21 A and spaces between the outermost winding part  21 A and peripheral parts of the inner peripheral winding part  21 B respectively are narrowed. In such a structure, the wide outermost winding part  21 A (that is allowed to meet the high frequency band such as 950 MHz) is formed as a plate shaped antenna (a plate inverted F antenna (PIFA)). The space between the outermost winding part  21 A and the inner peripheral winding part  21 B is set to a prescribed value so that capacities of wirings between the outermost winding  21 A and the inner peripheral winding part  21 B are connected together in view of a distribution factor. 
     Namely, when the spiral antenna  21  is allowed to operate as an antenna for a prescribed high frequency band, the outermost winding part  21 A is set to the same potential by the capacities between the wirings of the spiral loop antenna so that the spiral antenna is allowed to function as the inverted F antenna. On the other hand, when the spiral antenna is allowed to operate as an antenna for a low frequency band, since the capacities between the wirings of the spiral loop antenna are small, a current is supplied to ordinary wirings physically connected together. Thus, the spiral antenna is allowed to function as a spiral type loop antenna. 
     Further, in a board which is not shown in the drawing, such as a printed circuit board having a surface on which the spiral antenna  21  is mounted, an innermost part of the inner peripheral winding part  21 B is connected to one end of a wiring part  21 C provided on the back surface of the board with the same dimension of width as that of the inner peripheral winding part  21 B through a through hole SH 1 . Further, the wiring part  21 C is wired in such a manner as to stride over the inner peripheral winding part  21 B and the outermost winding part  21 A on the surface of the board from the backside of the board. Further, the other end part of the wiring part  21 C is connected to one end of an end conductor part  21 D having the same dimension of width as that of the inner peripheral winding part  21 B provided on the surface of the board through a through hole SH 2 . 
     The inverted F antenna A shown in  FIG. 3  includes, as well known, a feeding line P connected to the feeding part, a short-circuit line S that is grounded and a main part M (refer it to as a “main body part”, herein after) to which the feeding line P and the short-circuit line S are connected. 
     The feeding part switch unit  22  is allowed to operate in cooperation with the below-described grounding switch unit  23  so that the spiral antenna  21  may be switched to an operational function as the loop antenna for the low frequency band and an operational function as the inverted F antenna for the high frequency band. The feeding part switch unit  22  of the present embodiment is formed with a first switch SW 1  that connects a switching terminal  22 A provided in an end part of a lead-out line  211  (the feeding line P) led out or drawn out from a starting point of the outermost winding part  21 A to a first feeding terminal  22 B having one end connected to the first feeding part  241  or a second feeding terminal  22 C provided in a lead-out line  212  (through the second feeding part  242  forming a part of the feeding part  24 ) from the end conductor part  21 D of the inner peripheral winding part  21 B side by switching the first feeding terminal  22 B and the second feeding terminal  22 C. 
     The grounding switch unit  23  switches the outermost winding part  21 A of the spiral antenna  21  either to an opening or a grounding and is formed with a second switch SW 2  that connects a switching terminal  23 A at one end of a lead-out line  213  (the short-circuit line S) connected to a part a prescribed distance spaced from the starting point of the outermost winding part  21 A to a grounding terminal  23 B connected to a ground plate not shown in the drawing (GND of a casing side) part or an opening terminal  23 C by switching the grounding terminal  23 B and the opening terminal  23 C. According to this embodiment, in the feeding part switch unit  22  and the grounding switch unit  23 , a combined pattern at the time of switching on and off is exclusively determined. Therefore, in the present embodiment, since a user switches a switch  14  (see  FIG. 1 ) for switching on/off to selectively use one of below-described radio communication systems (as well as a function as the portable telephone), the operations of the feeding part switch unit  22  and the grounding switch unit  23  are automatically controlled by a control part not shown in the drawing. 
     The feeding part  24  includes the first feeding part  241  for the high frequency band and the second feeding part  242  for the low frequency band. The first feeding part  241  of the present embodiment connects and supplies a radio wave of a UHF (high frequency) band (a first frequency band) such as 950 MHz to a non-contact radio communication system (refer it to as a “first radio system”, hereinafter) such as an RFID tag system, and may read an RFID tag even when a communication distance is longer than that of a below-described radio communication system for the low frequency band. 
     On the other hand, the second feeding part  242  is connected to and supplies an electric power to a radio communication system (refer it to as a “second radio system”, hereinafter) in a short distance such as an IC tag or FeliCa (a registered trademark of Sony Corporation) used in the low frequency band (a second frequency band) such as 13.56 MHz (or 2.45 GHz). The second radio system may meet, for instance, a season ticket, electronic money, a point service and a biological certification used in a management of entry into a room or to draw out cash in a financial agency. 
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     The user operates the switch  14  (see  FIG. 1 ) for switching on/off to set the antenna to the radio system for, for instance, the RFID. Then, as shown in  FIG. 4 , the first switch SW 1  operates in accordance with a control signal form the control part not shown in the drawing to connect the switching terminal  22 A to the first feeding terminal  22 B, and the second switch SW 2  operates at the same time to connect the switching terminal  23 A to the grounding terminal  23 B. Thus, the spiral antenna is connected to the first feeding part  241  of a 950 MHz band to feed an electric power. Here, capacities C A  of wirings between the outermost winding part  21 A and the outermost winding part of the inner peripheral winding part  21 B are connected together in view of a distribution factor. Namely, in this frequency band, a conductor part (refer it to as an outermost side part  21 B 1 , hereinafter) of an outermost side as a starting part of the inner peripheral winding part  21 B connected to one side part (refer it to as a fourth side part  21 A 4 , hereinafter) having an end point of the outermost winding part  21 A is electrically conducted, in view of a high frequency current, to one side part (refer it to as a first side part  21 A 1 , hereinafter) having the starting point of the outermost winding part  21 A of the spiral antenna  21 . Accordingly, only the entire part of the outermost winding part  21 A has the same potential and operates as the inverted F antenna shown in  FIG. 3 . In this case, the outermost winding part  21 A forms the main body part M of the inverted F antenna A, the lead-out line  213  forms the short-circuit line S and the lead-out line  211  forms the feeding line P. 
     (II) In the case of using in second radio system for low frequency band: 
     The user operates the switch  14  for switching on/off to set the antenna to the radio system for, for instance, the FeliCa. Then, as shown in  FIG. 5 , the first switch SW 1  operates in accordance with a control signal from the control part to connect the switching terminal  22 A to the second feeding terminal  22 C. On the other hand, the second switch SW 2  operates to connect the switching terminal  23 A to the opening terminal  23 C. Thus, the first side part  21 A 1  is physically connected to the end conductor part  21 D and connected to the second feeding part  242  of 13.56 MHz to feed an electric power. In this frequency band, since capacities C A  between wirings of the spiral antenna  21  are low, adjacent peripheries are not electrically conducted together in view of a high frequency, but an electric current is supplied on the conductor from the outermost winding part  21 A to the outermost winding part  21 A and the end conductor part  21 D in an ordinary wiring. Thus, the spiral antenna operates as the loop antenna F. 
     Second Embodiment 
     Now, a second antenna device  3  according to a second embodiment of the present invention will be described below. In this embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and a duplicated explanation thereof is avoided. 
     The second antenna device  3  of the present embodiment, which is different from the first embodiment, includes, as a radio switch unit, a third switch  31  (SW 3 ) is provided as well as first and second switches between a starting point of an outermost winding part  21 A of a spiral antenna  21  and an end point of the outermost winding part  21 A, specifically described, a fourth side part  21 A 4  of the outermost winding part  21 A connected to an outermost side part  21 B 1  of an inner peripheral winding part  21 B as shown in  FIG. 6 . 
     The third switch SW 3  switches and connects a second switching terminal  31 A branching and provided from an intermediate part of a lead-out line  211  (a feeding line P) led out or drawn out from the starting point of the outermost winding part  21 A either to a second switching terminal  31 B or a fourth switching terminal  31 C for opening provided in a lead-out line  214  led out or drawn out from an end point of an outermost peripheral side (that is, the fourth side part  21 A 4 ) bent toward an inner periphery of the inner peripheral winding part  21 B. 
     In the present embodiment, with such a structure, that is, the three switches SW 1  to SW 3  are operated, so that the spiral antenna may be switched to the spiral loop antenna  21  and a plate shaped antenna using an outermost periphery (the outermost winding part  21 A). 
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     A user operates a switch  14  (see  FIG. 1 ) for switching on/off to set the antenna to a communication system for, for instance, an RFID. Then, as shown in  FIG. 7 , the first switch SW 1  operates in accordance with a control signal form a control part not shown in the drawing to connect a switching terminal  22 A to a first feeding terminal  22 B, and the second switch SW 2  operates at the same time to connect a switching terminal  23 A to a grounding terminal  23 B. Further, the third switch SW 3  operates at the same time as that of the switching operations to connect the second switching terminal  31 A to the third switching terminal  31 B. 
     In such a way, in a 950 MHz band, when the second switching terminal  31 A is connected to the third switching terminal  31 B, the first side part  21 A 1  of the outermost winding part  21 A is physically connected to the fourth side part  21 A 4 , an entire part of the outermost winding part  21 A has the same potential and operates as an inverted F antenna. Further, a first feeding part  241  is connected to the spiral antenna  21  to feed an electric power thereto, however, in the 950 MHz band, since an impedance of the inner peripheral winding part  21 B of a small width is high, an electric current is not supplied to the inner peripheral winding part  21 B. Thus, a high frequency current is supplied only to the outermost winding part  21 A. Accordingly, the outermost winding part  21 A functions as the inverted F antenna including the outermost winding part  21 A as a main body part M, a lead-out line  213  as a short-circuit line S and the lead-out line  211  as a feeding line P. 
     (II) In the case of using in second radio system for low frequency band: 
     The user operates the switch  14  for switching on/off to set the antenna to a communication system for, for instance, an FeliCa. Then, as shown in  FIG. 8 , the first switch SW 1  operates in accordance with a control signal from the control part to connect the switching terminal  22 A to a second feeding terminal  22 C. On the other hand, the second switch SW 2  operates to connect the switching terminal  23 A to an opening terminal  23 C. Further, the third switch SW 3  operates at the same time as that of the switching operations to connect the second switching terminal  31 A to the fourth switching terminal  31 C. 
     In such a way, in a 13.56 MHz band as a low frequency band, when the second switching terminal  31 A is connected to the fourth switching terminal  31 C, the outermost winding part  21 A is physically connected to the inner peripheral winding part  21 B and an end conductor part  21 D. Further, in this frequency band, a frequency is lower than that of the first radio system as in the first embodiment. Accordingly, since adjacent peripheries are not electrically conducted together in view of a high frequency, but the electric current is supplied to an actual conductor, the spiral antenna  21  operates as the loop antenna. 
     Third Embodiment 
     Now, a third antenna device  4  according to a third embodiment of the present invention will be described below. In this embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and a duplicated explanation thereof is avoided. 
     The third antenna device  4  of the present embodiment, which is different from the first embodiment, includes, as shown in  FIG. 9 , a conductor  21 E that is formed on a lower surface of a board  41  having an upper surface on which a spiral antenna  21  is mounted and is electrically connected to a part of a fourth side part  21 A 4  of an outermost winding part  21 A through a through hole  41 A. 
     The conductor  21 E is formed substantially in an L shape (a part surrounded in a dotted line in the left side in  FIG. 9(A) ) and formed substantially in the same configurations as those of the first side part  21 A 1  of the outermost winding part  21 A and a part of the fourth side part  21 A 4  as an end point of the outermost winding part  21 A under a state that the conductor  21 E is overlapped on them immediately below an outermost side part  21 B 1  as a staring part of an inner peripheral winding part  21 B connected to the fourth side part  21 A 4    
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     A user operates a switch  14  (see  FIG. 1 ) for switching on/off to set the antenna to a communication system for, for instance, an RFID. Thus, as shown in  FIG. 10 , the outermost winding part  21 A is connected to a first feeding part  241  of a 950 MHz band to feed an electric power thereto. Here, the conductor  21 E may be electro-statically connected to the first side part  21 A 1 , a part of the fourth side part  21 A 4  and the outermost side part  21 B 1  by capacities C B  of wirings between the overlapped parts (the first side part  21 A 1 , a part of the fourth side part  21 A 4  and the outermost side part  21 B 1  and the conductor  21 E) and has the same potential as those of them. That is, an entire part of the outermost winding part  21 A has the same potential as that of the conductor  21 E and operates as an inverted F antenna. 
     In the case of the present embodiment, a part corresponding to the main body part M of the inverted F antenna shown in  FIG. 3  is substantially extended more by the conductor  21 E than that of the first embodiment. Accordingly, since a connected capacity may be increased more than that of the first embodiment, a resonance frequency is low and a frequency band is narrowed. 
     (II) In the case of using in second radio system for low frequency band: 
     A user operates a switch  14  for switching on/off to set the antenna to a communication system for, for instance, an FeliCa. Thus, as shown in  FIG. 11 , the outermost winding part  21 A is connected to a second feeding part  242  of 13.56 MHz band to feed an electric power thereto. In this case, in  FIG. 11 , the overlapped parts (the first side part  21 A 1 , a part of the fourth side part  21 A 4  and the outermost side part  21 B 1  and the conductor  21 E) have the same potential. On the other hand, since the outermost winding part  21 A is physically connected to the inner peripheral winding part  21 B by a second switch SW 2 , a high frequency current is supplied between the outermost winding part  21 A and the inner peripheral winding part  21 B. Here, in a pattern of the conductor  21 E, since an end face is opened, an electric current is not supplied to the conductor  21 E. As a result, since the electric current is supplied only to a spiral conductor from the outermost winding part  21 A to the inner peripheral winding part  21 B and an end conductor part  21 D of the spiral antenna  21 , the spiral antenna  21  operates as the loop antenna F same as that of the first embodiment. 
     Fourth Embodiment 
     Now, a fourth antenna device  5  according to a fourth embodiment of the present invention will be described below. In this embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and a duplicated explanation thereof is avoided. 
     The fourth antenna device  5  of the present embodiment, which is different from the first embodiment, includes, as shown in  FIG. 12 , a metal conductor  52  on a back surface of an insulating board  51  having a surface on which a spiral antenna  21  is mounted. 
     The conductor  21 F is formed substantially in the same configurations as those of a first side part  21 A 1  of an outermost winding part  21 A of the spiral antenna  21 , a part of a fourth side part  21 A 4  of the outermost winding part  21 A and an outermost side part  21 B 1  of an inner winding part  21 B connected thereto under a state that the conductor  21 F is overlapped on them immediately below them. 
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     When a user operates a switch  14  (see  FIG. 1 ) for switching on/off, the outermost winding part  21 A is connected to a first feeding part  241  of a 950 MHz band to feed an electric power thereto. In this case, in  FIG. 13 , an entire part of the outermost winding part  21 A has the same potential as that of the metal conductor  52  by a capacity connection Cc of the first side part  21 A 1  (of the outermost winding part  21 A) of the spiral antenna  21 , a part of the fourth side part  21 A 4  and the outermost side part  21 B 1  (of the inner peripheral winding  21 B) and the metal conductor  52  that is positionally overlapped on these conductors immediately below them through the insulating board  51  and operates as an inverted F antenna. 
     (II) In the case of using in second radio system for low frequency band: 
     When a user operates a switch  14  for switching on/off to switch to an opposite part, the outermost winding part  21 A is connected to a second feeding part  242  of 13.56 MHz band to feed an electric power thereto. In this case, in  FIG. 14 , the parts overlapped in upper and lower parts in view of a position (the outermost end conductor part  21 A 1 , a part of the fourth side part  21 A 4  and the conductor  21 B 1  and the metal conductor  52 ) have the same potential by an electrostatic connection. Further, since a first switch SW 1  is switched by operating the switch  14 , the outermost winding part  21 A is physically connected to the inner peripheral winding part  21 B. Accordingly, an ac current is supplied from the outermost winding part  21 A to the inner peripheral winding part  21 B. However, in a pattern of the metal conductor  52 , since an end face is opened, an electric current is not supplied to the metal conductor  52 . Namely, since the electric current is supplied only to a spiral conductor from the outermost winding part  21 A to the inner peripheral winding part  21 B and an end conductor part  21 D of the spiral antenna  21 , the spiral antenna  21  operates as the loop antenna F same as those of the first to third embodiments. 
     Fifth Embodiment 
     Now, a fifth antenna device  6  according to a fifth embodiment of the present invention will be described below. In this embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and a duplicated explanation thereof is avoided. 
     In the fifth antenna device  6  of the present embodiment, as shown in  FIG. 15 , a spiral antenna  21  the same as that of the first embodiment is mounted on the surface of a board  61 . An insulating board  62  formed substantially in the shape of a character   is laminated thereon in such a way as to cover the entire surface of the spiral antenna  21 . On the insulating board  62 , a metal conductor  63  similarly formed substantially in the shape of a character   is mounted. 
     The metal conductor  63  having a width smaller than that of the insulating board  62  is laminated immediately above an outermost winding part  21 A through the insulating board  62  so as to be overlapped on the outermost winding part  21 A in view of a position. Further, in the metal conductor  63 , since one end of a lead-out line  63 A (a short-circuit line) led out or drawn out from a ground point necessary for an inverted F antenna is connected to a ground plate (GND of a casing side) not shown in the drawing, a second switch SW 2  does not need to be provided as a grounding switch unit. 
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     When a user operates a switch  14  (see  FIG. 1 ) for switching on/off, the outermost winding part  21 A is connected to a first feeding part  241  of a 950 MHz band to feed an electric power thereto. In this case, in  FIG. 16 , the outermost winding part  21 A is electrically conducted to the metal conductor  63  in view of a high frequency to feed an electric power by a capacity connection of the outermost winding part  21 A of the spiral antenna  21  and the metal conductor overlapped thereon positionally in upper and lower parts. In this case, since the metal conductor  63  is electrically conducted to the outermost winding part  21 A 1  in view of a high frequency, the two conductors form one antenna. Namely, the metal conductor  63  just above the outermost winding part  21 A may receive the supply of a high frequency current from the first feeding part  241  through the outermost winding part  21 A. Further, since a part corresponding to the ground point of the outermost winding part  21 A is a ground part, the conductor part  63  may operate as an inverted F antenna. 
     (II) In the case of using in second radio system for low frequency band: 
     When a user operates a switch  14  for switching on/off to switch to an opposite part, as shown in  FIG. 17 , the outermost winding part  21 A is connected to a second feeding part  242  of a 13.56 MHz band to feed an electric power thereto. In this low frequency band, since the capacity connection of the outermost winding part  21 A of the spiral antenna  21  and the metal conductor  63  overlapped thereon positionally in upper and lower parts is low, an electric current is supplied to an ordinary wiring, that is, only to the spiral antenna  21  and the spiral antenna operates as a loop antenna. Namely, since a capacity is low between the metal conductor  63  and (the ground point thereof) is low, the metal conductor  63  is not electrically conducted thereto in view of a high frequency. Thus, the electric current is not supplied to the metal conductor  63 . 
     Sixth Embodiment 
     Now, a sixth antenna device  7  according to a sixth embodiment of the present invention will be described below. In this embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and a duplicated explanation thereof is avoided. 
     As shown in  FIGS. 18 and 20 , the sixth antenna device  7  of the present embodiment, which is different from the first embodiment, includes a metal conductor  71  having a plate shaped antenna part and a spiral antenna  72  having the same form as that of the inner peripheral winding part  21 B of the first embodiment. The metal conductor  71  and the spiral antenna  72  are connected in parallel with a first feeding part  241  and a second feeding part  242  through a first switch SW 1  forming a part of a feeding part switch unit  22  (see  FIG. 19 ). The metal conductor  71  and the spiral antenna  72  are mounted on one surface of an insulating board  73 . 
     As shown in  FIG. 20 , the metal conductor  71  is arranged outside the spiral antenna  72  and is formed with a plate shaped metal conductor with a central part bored substantially in the shape of a character   (the central part is hollow) to form a plate shaped antenna. Further, the metal conductor  71  may be switched to a spiral loop antenna and the plate shaped antenna depending on an employed frequency by using the inductance of wiring directed toward an inner periphery. 
     The spiral antenna  72  has a spiral shape similar to that of the inner peripheral winding part  21 B as shown in  FIG. 20 . An inner edge part of one side part  71 B of the metal conductor  71  and an outer end part  72 B of a winding part  72 A are physically formed integrally on the same surface. 
     Now, an operation of the present embodiment will be described below. 
     (I) In the case of using in first radio system for high frequency band: 
     When a user operates a switch  14  (see  FIG. 1 ) for switching on/off, the metal conductor  71  is connected to the first feeding part  241  of a 950 MHz band to feed an electric power thereto. In this high frequency band, in  FIG. 21 , an electric current is not supplied to an inner periphery (an inner peripheral winding part  72 ) of the spiral antenna  72  due to the high inductance component of a spiral loop, but is supplied only to the metal conductor  71 . Thus, the metal conductor has a structure that may operate as an inverted F antenna. 
     (II) In the case of using in second radio system for low frequency band: 
     When a user operates a switch  14  for switching on/off to switch to an opposite part, as shown in  FIG. 22 , the metal conductor  71  is connected to the second feeding part  242  of a 13.56 MHz band to feed an electric power thereto. In this low frequency band, since the metal conductor  71  located at an outermost periphery has an entire length of a circumference (=length of four sides of the metal conductor  71 ) L smaller than the length (about 20 m) of a wavelength λ (=v/f; in this case, f=13.56 MHz, v=propagation velocity of radio wave), a high frequency current is not supplied. Namely, the electric current is supplied only to the spiral antenna  72  and the spiral antenna operates as the loop antenna. Further, since a capacity is low, the electric current is not supplied to the ground point of the metal conductor  71 . 
     The present invention is not limited to the above-described embodiments and various forms may be embodied within a scope without departing from the gist of the invention. 
     For instance, in place of a form in which the outermost winding part  21 A 1  is thickened in the first embodiment, as shown in  FIG. 23 , a structure may be formed in which spaces between wirings of an inner side part continuous to an outermost side part  21 B 1  are made to be dense to use an electrostatic connection between them. An operational principle in this case utilizes a capacity between wirings as in the first embodiment. 
     Further, a portable terminal device having the antenna device according to the embodiment of the present invention is not especially limited to the portable telephone described in the embodiments, and, for instance, such a structure as to mounted on a PHS or a PDA may be used. Further, an exclusive device of a handy type reader and writer may be used. 
     The present invention is specifically described above by referring to the specific embodiments, however, it is to be understood to a person with ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. 
     INDUSTRIAL APPLICABILITY  
     The antenna device of the present invention can be effectively used for the radio communication systems of two different frequency bands by sharing a single antenna. The antenna device may be applied to the portable telephone, the PHS (Personal Handy-phone System), the PDA (Personal Digital Assistant) or the like as the portable terminal device and advantageously mounted thereon.