Abstract:
In an antenna apparatus, a first current is induced in a first booster conductor by a current flowing through a coil conductor of a power feed antenna, and the first current circulates along a circumference of the first booster conductor. A second current is induced in a second booster conductor by the current flowing through the coil conductor of the power feed antenna, and the second current circulates along a circumference of the second booster conductor. A third current is induced in the first booster conductor by the second current flowing through the second booster conductor, and the third current circulates along the circumference of the first booster conductor. Thus, the antenna apparatus is much less influenced by nearby metallic objects and a shape of an included radiation plate may be more freely determined without requiring a highly accurate positional relationship between the radiation plate and the coil conductor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to antenna apparatuses and communication terminal instruments for use in RFID systems or near field wireless communication systems, which communicate with counterpart devices through electromagnetic signals. 
         [0003]    2. Description of the Related Art 
         [0004]    In an RFID system or a near field wireless communication system, the use of which is growing in recent years, a communication antenna is mounted on each device for communications between portable electronic instruments such as portable phones or between a portable electronic instrument and a reader/writer. Of these antennas, International Publication Pamphlet No. WO 2009/142114 discloses antennas to be mounted on portable electronic instruments. 
         [0005]      FIG. 1A  is a cross-sectional diagram of a principle portion of a wireless IC device described in International Publication Pamphlet No. WO 2009/142114.  FIG. 1B  is a diagram illustrating a spatial arrangement of a power feed circuit board and a radiation board of the wireless IC device. The wireless IC device  1  includes a wireless IC chip  5  that processes predetermined radio signals, a power feed circuit board  4  that is connected to the wireless IC chip  5  and includes a power feed circuit including at least one coil pattern  23 , and a radiation plate  3  that radiates transmission signals provided from the power feed circuit board  4 , receives reception signals, and provides them to the power feed circuit board  4 . The radiation plate  3  includes in part an opening portion  7  and a slit portion  6  connecting to the opening portion  7 . The opening portion  7  of the radiation plate  3  overlaps an inner side region of the coil pattern  23  in plan view when viewed in a winding axis direction of the coil pattern  23 , and areas of the inner side region and the opening portion  7  are nearly equal to each other. 
         [0006]    In  FIG. 1A , when a radio signal is being transmitted, a signal current flows from the wireless IC chip  5  to the coil pattern  23 . An induced magnetic field H generated by that current distributes through the opening portion  7  as illustrated by dotted lines in the drawing. The induced magnetic field H causes induced currents I 1  and I 2  to flow in a surrounding portion of the opening portion  7 , as illustrated in  FIG. 1B . Here, the slit portion  6  is connected to the opening portion  7 . Thus, the slit portion  6  limits the flows of these induced currents I 1  and I 2 . As described above, in the radiation plate  3 , the induced currents I 1  and I 2  are induced by the magnetic field H. This magnetic field causes the radio signal to be transmitted. 
         [0007]    However, it is necessary to have the opening portion and the slit portion in the radiation plate. Thus, a restriction is imposed on the shape of the radiation plate, and a highly accurate positional relationship between the radiation plate and the coil conductor must be satisfied. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, preferred embodiments of the present invention provide an antenna apparatus and a communication terminal instrument in which a shape of a radiation plate may be more freely determined without requiring a highly accurate positional relationship between the radiation plate and a coil conductor. 
         [0009]    An antenna apparatus according to a preferred embodiment of the present invention includes a power feed antenna that includes a coil conductor, to which a power feed circuit is connected; a first booster conductor that couples to the coil conductor of the power feed antenna through an electromagnetic field; and a second booster conductor that couples to the first booster conductor through an electromagnetic field and couples to the power feed antenna through an electromagnetic field. 
         [0010]    For example, in plan view, a first edge portion of the coil conductor overlaps a first edge portion of the first booster conductor, a second edge portion of the coil conductor overlaps a first edge portion of the second booster conductor, and a second edge portion of the first booster conductor overlaps a second edge portion of the second booster conductor. 
         [0011]    According to the foregoing structure, a current is induced in the first booster conductor by the power feed antenna, and a current is induced in the second booster conductor by the first booster conductor and the power feed antenna. Thus, according to the foregoing structure, neither an opening portion nor a slit is necessary. Thus, the provision of the first booster conductor and the second booster conductor makes it possible to more freely determine a shape of a radiation plate (first and second booster conductors). 
         [0012]    When the first booster conductor is larger than the second booster conductor, a degree of freedom in arranging the two booster conductors becomes higher and fitting into an electronic device becomes easier, compared to a case where the first booster conductor and the second booster conductor have the same size. 
         [0013]    Furthermore, when a distance between the power feed antenna and the first booster conductor is shorter than a distance between the power feed antenna and the second booster conductor, the first booster conductor, which is the larger booster conductor, couples to the power feed antenna more strongly. Accordingly, a better antenna characteristic may be obtained, compared to a case where the second booster conductor, which is the smaller booster conductor, couples to the power feed antenna more strongly. 
         [0014]    A communication terminal instrument according to a preferred embodiment of the present invention includes an antenna apparatus including a power feed antenna that includes a coil conductor; a first booster conductor that couples to the coil conductor of the power feed antenna through an electromagnetic field; and a second booster conductor that couples to the first booster conductor through an electromagnetic field and couples to the power feed antenna through an electromagnetic field. The communication terminal instrument further includes a power feed circuit that is connected to the coil conductor. 
         [0015]    The first booster conductor preferably is, for example, a metal member contained inside a casing or is the case of the communication terminal instrument. According to the foregoing structure, no special member is required to define the first booster conductor. Thus, the number of components, a device size, and manufacturing costs are significantly reduced. 
         [0016]    According to various preferred embodiments of the present invention, no radiation plate having an opening portion and a slit is necessary. Thus, the provision of the first booster conductor and the second booster conductor makes it possible to determine the shape of the radiation plate (first and second booster conductors) more freely. Furthermore, a highly accurate positional relationship among the first and second booster conductors, which define the radiation plate, and the coil conductor is not required. 
         [0017]    The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1A  is a cross-sectional diagram of a principle portion of a wireless IC device described in International Publication Pamphlet No. WO 2009/142114. 
           [0019]      FIG. 1B  is a diagram illustrating a spatial arrangement of a power feed circuit board and a radiation board of the wireless IC device. 
           [0020]      FIG. 2A  is a schematic plan view of an antenna apparatus  101  according to a first preferred embodiment of the present invention, and  FIG. 2B  is a partially enlarged plan view of the antenna apparatus  101 . 
           [0021]      FIGS. 3A-3D  are diagrams illustrating an operational principle of the antenna apparatus  101 . 
           [0022]      FIG. 4  is an exploded perspective view of an antenna apparatus  102  according to a second preferred embodiment of the present invention. 
           [0023]      FIG. 5  is an exploded perspective view illustrating shapes of a second booster conductor  62 , a power feed antenna  50 , and a ferrite sheet  63 , and a positional relationship among them. 
           [0024]      FIG. 6  is a partially enlarged plan view of the antenna apparatus  102 . 
           [0025]      FIG. 7  is a diagram illustrating an operational principle of the antenna apparatus  102 . 
           [0026]      FIG. 8A  is a plan view of an antenna apparatus  103 , and  FIG. 8B  is a plan view of a principle portion of the antenna apparatus  103 . 
           [0027]      FIG. 9  is a diagram illustrating an operational principle of the antenna apparatus  103 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
           [0028]      FIG. 10A  is a plan view of an antenna apparatus  104 , and  FIG. 10B  is a plan view of a principle portion of the antenna apparatus  104 . 
           [0029]      FIG. 11  is a diagram illustrating an operational principle of the antenna apparatus  104 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
           [0030]      FIG. 12A  is a plan view of an antenna apparatus  105 , and  FIG. 12B  is a plan view of a principle portion of the antenna apparatus  105 . 
           [0031]      FIG. 13  is a diagram illustrating an operational principle of the antenna apparatus  105 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Preferred Embodiment 
       [0032]    An antenna apparatus according to a first preferred embodiment is described with reference to  FIGS. 2A ,  2 B and  FIGS. 3A-3D .  FIG. 2A  is a schematic plan view of an antenna apparatus  101  according to the first preferred embodiment, and  FIG. 2B  is a partially enlarged plan view of the antenna apparatus  101 . 
         [0033]    The antenna apparatus  101  includes a power feed antenna  30 , a first booster conductor  41 , and a second booster conductor  42 . As illustrated in  FIG. 2B , the power feed antenna  30  preferably includes a spiral coil conductor  32  located on an insulating support film  31  such as a polyimide film. 
         [0034]    The first booster conductor  41  preferably includes a conducting film located on an insulating support film such as a polyimide film. Similarly, the second booster conductor  42  preferably includes a conducting film located on an insulating support film such as a polyimide film. 
         [0035]    A first edge portion  32 E 1  of the coil conductor  32  overlaps a first edge portion  41 E 1  of the first booster conductor  41 . This arrangement allows the first booster conductor  41  to couple to the coil conductor  32  of the power feed antenna  30  through an electromagnetic field. Furthermore, a second edge portion  32 E 2  of the coil conductor  32  overlaps a first edge portion  42 E 1  of the second booster conductor  42 . This arrangement allows the second booster conductor  42  to couple to the coil conductor  32  of the power feed antenna  30  through an electromagnetic field. Still furthermore, a second edge portion  41 E 2  of the first booster conductor  41  overlaps a second edge portion  42 E 2  of the second booster conductor  42 . This arrangement allows the first booster conductor  41  to couple to the second booster conductor  42  through an electromagnetic field. 
         [0036]      FIGS. 3A-3D  are diagrams illustrating an operational principle of the antenna apparatus  101 .  FIG. 3A  illustrates a way of coupling between the power feed antenna  30  and the first booster conductor  41 . 
         [0037]    As illustrated in  FIG. 3A , a current i 10  is induced in the first booster conductor  41  by a current i 0  flowing through the coil conductor of the power feed antenna  30 . That is, the current i 0  causes the current i 10  to flow through the first booster conductor  41  in a direction to cancel the current i 0  at a portion where the power feed antenna  30  overlaps the first booster conductor  41 . This current i 10  circulates a circumference of the first booster conductor  41  due to an edge effect. 
         [0038]    As illustrated in  FIG. 3B , a current i 2  is induced in the second booster conductor  42  by the current i 0  flowing through the coil conductor of the power feed antenna  30 . That is, the current i 0  causes the current i 2  to flow through the second booster conductor  42  in a direction to cancel the current i 0  at a portion where the power feed antenna  30  overlaps the second booster conductor  42 . This current i 2  circulates a circumference of the second booster conductor  42  due to the edge effect. 
         [0039]    As illustrated in  FIG. 3C , a current i 12  is induced in the first booster conductor  41  by the current i 2  flowing through the second booster conductor  42 . That is, the current i 2  causes the current i 12  to flow through the first booster conductor  41  in a direction to cancel the current i 2  at a portion where the second booster conductor  42  overlaps the first booster conductor  41 . This current i 12  circulates the circumference of the first booster conductor  41  due to the edge effect. 
         [0040]      FIG. 3D  illustrates the currents illustrated in  FIGS. 3A-3C , which are superimposed on each other. Thus, the current i 2  flows through the second booster conductor  42 , and the currents i 10  and i 12  flow through the first booster conductor  41 . The current i 10  and the current i 12  are currents in the same phase. Thus, both currents are added, and a current of i 10 +i 12  flow through the first booster conductor  41 . Accordingly, compared to a case where only the first booster conductor  41  is coupled to the power feed antenna  30 , an additional current, the amount of which is equivalent to the current i 2  and the current i 12 , flows. Furthermore, a current circulation path is expanded by having the current i 2  flowing through the second booster conductor  42 . These two effects improve an antenna gain. 
         [0041]    It should be noted that there are a plurality of ways in the order of stacking the first booster conductor  41 , the second booster conductor  42 , and the power feed antenna  30 . However, all the ways produce similar effects. When the first booster conductor  41  is larger than the second booster conductor  42 , it is preferable, in view of improving an antenna characteristic, to have a shorter distance between the power feed antenna  30  and the first booster conductor  41  than a distance between the power feed antenna and the second booster conductor  42  because such an arrangement allows the first booster conductor  41 , which is the larger booster conductor, to couple to the power feed antenna  30  more strongly. 
         [0042]    In the example illustrated in  FIG. 2 , the coil conductor  32  defines a two-turn coil. The number of turns and the dimension of each side may be determined according to a required inductance. The coil conductor  32  and a circuit board are connected by, for example, pin terminals. That is, pad electrodes are preferably formed at both ends of the coil conductor  32  in advance, and configured so as to abut the pin terminals provided in a board on which the coil conductor  32  is mounted. 
       Second Preferred Embodiment 
       [0043]    An antenna apparatus and a communication terminal instrument according to a second preferred embodiment are described with reference to  FIG. 4-FIG .  7 .  FIG. 4  is an exploded perspective view of an antenna apparatus  102  according to the second preferred embodiment.  FIG. 5  is an exploded perspective view illustrating shapes of a second booster conductor  62 , a power feed antenna  50  and a ferrite sheet  63 , and a positional relationship among them.  FIG. 6  is a partially enlarged plan view of the antenna apparatus  102 . The antenna apparatus  102  is an antenna apparatus preferably for use typically in a near field wireless communication system or a RFID system using 13.56 MHz band (HF band), for example. 
         [0044]    In  FIG. 4 , the antenna apparatus  102  preferably includes a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . Furthermore, the communication terminal instrument preferably includes the antenna apparatus  102 , a printed wiring board  64 , and components mounted on the printed wiring board  64 . A rod antenna  65  and an image sensor  66  of a camera are mounted on the printed wiring board  64 . Furthermore, a magnetic sheet  63 , for example, such as a ferrite sheet, is arranged below the power feed antenna  50 . Furthermore, the printed wiring board  64  is provided with a power feed circuit that feeds power to a coil conductor  32  of the antenna apparatus  102 . The first booster conductor  61  is a metal casing (thin metal sheet). That is, a member that is originally included in the communication terminal instrument is shared as the first booster conductor  61 . 
         [0045]    The power feed antenna  50  preferably includes a coil conductor located on an insulating support film, as is the case with the power feed antenna  30  illustrated in  FIG. 2B  in the first preferred embodiment. The second booster conductor  62  preferably has a shape similar to the letter “Π”. The magnetic sheet  63  preferably has a shape similar to the letter “L”, and overlaps the coil conductor  32  of the power feed antenna  50  on two sides thereof. The magnetic sheet  63  defines magnetic paths such that a magnetic flux, which extends beyond a winding center of the coil conductor of the power feed antenna  50 , passes through edges of the printed wiring board. 
         [0046]    In plan view, the first booster conductor  61  overlaps an edge portion of the coil conductor  32  of the power feed antenna  50 , edge portions of the coil conductor  32  overlap edge portions of the second booster conductor  62 , and an edge portion of the first booster conductor  61  overlaps edge portions of the second booster conductor  62 . In this example, the second booster conductor  62  preferably has a shape similar to the letter “Π”, and thus overlaps the coil conductor  32  on three sides. Furthermore, the first booster conductor  61  overlaps the coil conductor  32  on one side. That is, a loop is defined by the overlapping portion of the first booster conductor  61  and the overlapping portions of the second booster conductor  62 , all of which overlap the coil conductor  32 . 
         [0047]      FIG. 7  is a diagram illustrating an operational principle of the antenna apparatus  102 .  FIG. 7  illustrates ways of coupling among the power feed antenna  50 , the first booster conductor  61 , and the second booster conductor  62 . 
         [0048]    First, a current i 10  is induced in the first booster conductor  61  by a current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Furthermore, a current i 2  is induced in the second booster conductor  62  by the current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Then, a current i 12  is induced in the first booster conductor  61  by the current i 2  flowing through the second booster conductor  62 . 
         [0049]    Accordingly, compared to a case where only the first booster conductor  61  is coupled to the power feed antenna  50 , there exists an additional current flow, the amount of which is equivalent to the current i 2  and the current i 12 . Furthermore, a current circulation path is expanded by having the current i 2  flowing through the second booster conductor  62 . These two effects improve an antenna gain. 
         [0050]    It should be noted that the magnetic sheet  63  illustrated in  FIG. 5  may have the same shape as that of the power feed antenna  50  to cover the whole area of a bottom plane of the power feed antenna  50 , for example. Furthermore, when there is no need for forced shaping of the magnetic path, no magnetic sheet is necessary. Furthermore, a magnetic member other than the ferrite may be used as the magnetic sheet. 
         [0051]    A capacitor for frequency adjustment may be connected to both ends of the coil conductor  32  that is included in the power feed antenna  50  to determine a resonance frequency of the antenna apparatus  102 . This capacitor for frequency adjustment may be provided at any one of the power feed antenna  50 , the printed wiring board  64 , and a wireless IC component. 
       Third Preferred Embodiment 
       [0052]    An antenna apparatus according to a third preferred embodiment is described with reference to  FIGS. 8A and 8B  and  FIG. 9 .  FIG. 8A  is a plan view of an antenna apparatus  103 , and  FIG. 8B  is a plan view of a principle portion of the antenna apparatus  103 .  FIG. 9  is a diagram illustrating an operational principle of the antenna apparatus  103 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
         [0053]    As illustrated in  FIG. 8A , the antenna apparatus  103  preferably includes a coil conductor  32  of the power feed antenna, the first booster conductor  61 , and the second booster conductor  62 . The power feed antenna  50  preferably includes an insulating support film and the coil conductor  32  located on the support film. In the third preferred embodiment, the second booster conductor  62  preferably is ring-shaped, and one side thereof overlaps one side of the coil conductor  32 . Furthermore, the power feed antenna  50 , the first booster conductor  61 , and the second booster conductor  62  are sequentially stacked in that order. 
         [0054]    As illustrated in  FIG. 9 , first, a current i 10  is induced in the first booster conductor  61  by a current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Furthermore, a current i 2  is induced in the second booster conductor  62  by the current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Then, a current i 12  is induced in the first booster conductor  61  by the current i 2  flowing through the second booster conductor  62 . 
         [0055]    Accordingly, compared to a case where only the first booster conductor  61  is coupled to the power feed antenna  50 , there exists an additional current flow, the amount of which is equivalent to the current i 2  and the current i 12 . Furthermore, a current circulation path is expanded by having the current i 2  flowing through the second booster conductor  62 . These two effects improve an antenna gain. 
       Fourth Preferred Embodiment 
       [0056]    An antenna apparatus according to a fourth preferred embodiment is described with reference to  FIGS. 10A ,  10 B and  FIG. 11 .  FIG. 10A  is a plan view of an antenna apparatus  104 , and  FIG. 10B  is a plan view of a principle portion of the antenna apparatus  104 .  FIG. 11  is a diagram illustrating an operational principle of the antenna apparatus  104 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
         [0057]    As illustrated in  FIG. 10A , the antenna apparatus  104  preferably includes a coil conductor  32  of the power feed antenna, the first booster conductor  61 , and the second booster conductor  62 . The power feed antenna  50  preferably includes an insulating support film and the coil conductor  32  located on the support film. In the fourth preferred embodiment, the second booster conductor  62  has a ring portion and a portion linearly extending therefrom, and overlaps the coil conductor  32  on two sides thereof. Furthermore, the power feed antenna  50 , the second booster conductor  62 , and the first booster conductor  61  are sequentially stacked in that order. 
         [0058]    As illustrated in  FIG. 11 , a current i 10  is induced in the first booster conductor  61  by a current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Furthermore, a current i 2  is induced in the second booster conductor  62  by the current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Then, a current i 12  is induced in the first booster conductor  61  by the current i 2  flowing through the second booster conductor  62 . 
         [0059]    Accordingly, compared to a case where only the first booster conductor  61  is coupled to the power feed antenna  50 , there exists an additional current flow, the amount of which is equivalent to the current i 2  and the current i 12 . Furthermore, a current circulation path is expanded by having the current i 2  flowing through the second booster conductor  62 . These two effects improve an antenna gain. 
       Fifth Preferred Embodiment 
       [0060]    An antenna apparatus according to a fifth preferred embodiment is described with reference to  FIGS. 12A and 12B  and  FIG. 13 .  FIG. 12A  is a plan view of an antenna apparatus  105 , and  FIG. 12B  is a plan view of a principle portion of the antenna apparatus  105 .  FIG. 13  is a diagram illustrating an operational principle of the antenna apparatus  105 , and illustrates ways of coupling among a power feed antenna  50 , a first booster conductor  61 , and a second booster conductor  62 . 
         [0061]    As illustrated in  FIG. 12A , the antenna apparatus  105  preferably includes a coil conductor  32  of the power feed antenna, the first booster conductor  61 , and the second booster conductor  62 . The power feed antenna  50  preferably includes an insulating support film and the coil conductor  32  located on the support film, and includes an opening in a center portion. In the fifth preferred embodiment, the second booster conductor  62  includes a ring portion and a portion that has a shape similar to the letter “L” and extends from the ring portion, and overlaps the coil conductor  32  on three sides thereof. Furthermore, the power feed antenna  50 , the second booster conductor  62 , and the first booster conductor  61  are sequentially stacked in that order. 
         [0062]    As illustrated in  FIG. 13 , first, a current i 10  is induced in the first booster conductor  61  by a current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Furthermore, a current i 2  is induced in the second conductor  62  by the current i 0  flowing through the coil conductor  32  of the power feed antenna  50 . Then, a current i 12  is induced in the first booster conductor  61  by the current i 2  flowing through the second booster conductor  62 . 
         [0063]    Accordingly, compared to a case where only the first booster conductor  61  is coupled to the power feed antenna  50 , there exists an additional current flow, the amount of which is equivalent to the current i 2  and the current i 12 . Furthermore, a current circulation path is expanded by having the current i 2  flowing through the second booster conductor  62 . These two effects improve an antenna gain. 
       Other Preferred Embodiments 
       [0064]    In the foregoing preferred embodiments, the power feed coils include spiral conductor patterns. Alternatively, the power feed coils may include multilayered loop (helical) conductor patterns. The number of turns may be one if needed. Furthermore, planar shapes of the conductor patterns do not need to be rectangular, and may be circular or an irregular shape. Still furthermore, the number of the booster conductors may be three or more. 
         [0065]    In the foregoing preferred embodiments, the examples are described for a case in which the power feed coil are preferably coupled to the first booster conductor and the second booster conductor through mostly a magnetic field. However, the coupling may be made through mostly an electric field depending on the frequency band. Furthermore, the coupling may alternatively be made through both an electric field and a magnetic field. This is because, when a high frequency signal is used, sufficient energy may be transferred even by capacitance generated between the power feed coil and the booster conductor. In the scope of claims and description of the present application, the “coupling through an electromagnetic field” includes three modes of coupling: “(1) coupling through mostly an electric field; (2) coupling through mostly a magnetic field; and (3) coupling through an electric field and a magnetic field”. 
         [0066]    Furthermore, in the foregoing preferred embodiments, the examples are described for a case in which the present invention is applied to HF-band RFID devices. However, the present invention is not limited to the HF-band RFID devices, and may be similarly applied to UHF-band RFID devices. In cases with the UHF-band, the currents flow along not only circumferences of the first booster conductor and the second booster conductor, but also a plurality of current path loops distributed over the booster conductors and electromagnetic fields are induced in such a way that a magnetic flux interlinks adjacent current loops. Furthermore, preferred embodiments of the present invention may also be applicable to systems other than an RFID system. 
         [0067]    The power feed circuit, which is connected to the coil conductor of the antenna apparatus according to a preferred embodiment of the present invention, preferably includes, for example, a wireless IC component. The wireless IC component is typically mounted on the printed wiring board, but may alternatively be mounted on the power feed antenna. 
         [0068]    While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.