Patent Publication Number: US-8113439-B2

Title: Antenna apparatus

Description:
This application is a continuation application of U.S. patent application Ser. No. 11/660,560, filed on Feb. 15, 2007, now U.S. Pat. No. 7,503,509 entitled “ANTENNA APPARATUS,” which is a national phase filing claiming priority of PCT Application No. PCT/JP2006/312067, filed on Jun. 15, 2006, and Japanese Patent Application No. 2005-192561, filed on Jun. 30, 2005. The U.S. patent application Ser. No. 11/660,560, filed on Feb. 15, 2007, entitled “ANTENNA APPARATUS,” is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an antenna apparatus for use in non-contact type IC cards into and from which data can be written and read when the cards are induction coupled with an electromagnetic field by electronic apparatuses having a communication function. 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2005-192561, filed in Japan on Jun. 30, 2005, the entire content of which is incorporated herein by reference. 
     BACKGROUND ART 
     In recent years, so-called radio frequency Identification (RFID) systems that use non-contact type IC cards or IC tags have been introduced into automatic gates at railway stations, entrance/exit security systems, electronic money systems, and the like. As  FIG. 1  schematically shows, the RFID system comprises a non-contact type IC card  100  and a reader/writer  101 . The reader/writer  101  can write data into, and read data from, the IC card  100 . In the RF system, when a loop antenna  102  provided on the reader-writer  101  radiates a magnetic flux, the magnetic flux is magnetically coupled with a loop antenna  103  provided on the IC card  100 , in accordance with the principle of electromagnetic induction. Thus, communication is performed between the IC card  100  and the reader/writer  101 . 
     In the RFID system, the user need not insert the IC card into the reader/writer or set the IC card into contact with the metal contact point provided on the reader/writer as is required in the conventional contact-type IC card system, and data can be easily and fast written and read into and from the IC card. Since the reader/writer  101  supplies power to the IC card  100  by virtue of electromagnetic induction, the IC card  100  need not incorporate a power supply such as a battery. The RFID system therefore can provide IC cards that are simple in configuration and, inexpensive and reliable. 
     However, the IC card may fail to communicate with the reader/writer if it incorporates an IC tag having communication frequency of 13.56 MHz. That is, the IC tag is influenced by any metal member that lies near the IC card. In the communication achieved at 13.56 MHz by virtue of electromagnetic induction, the IC tag is influenced by any metal member that exists near it, inevitably changing inductance. The change in inductance results in a shift of the resonance frequency or a change in the magnetic flux. As a result, no power can be attained. 
     In the RFID system described above, to ensure he communicable range between the IC card  100  and the reader/writer  101 , the IC card  100  needs to have the loop antenna  103  that can emit an electromagnetic field having a sufficient magnetic field intensity. 
     A technique that can reduce the influence a metal housing imposes on the loop antenna is known, other than the technique of arranging the loop antenna in an open space. Jpn. Pat. Appln. Laid-Open Publication No. 2001-331772, for example, discloses an antenna apparatus for use in IC cards. This antenna apparatus has a plate of magnetic material, which reduces the influence of any metal member. 
     DISCLOSURE OF INVENTION 
     Object the Invention is to Achieve 
     With an antenna apparatus of the type described in the above patent publication, the communication distance can be increased, but to some extent only. Since the communication range is narrow, communication errors may occur with the non-contact type IC card in some cases. Consequently, the non-contact type IC card cannot fully achieve its convenience. 
     Accordingly, a technical object of the present invention is to provide an antenna apparatus for use in non-contact type IC card, which can not only be small and thin, but also increase the communication distance between the IC card and an electronic apparatus with a communication function. 
     An antenna apparatus, which is an embodiment of this invention, is designed for use in a non-contact type IC card into and from which data can be written and read by electronic apparatuses having a communication function, by virtue of inductive coupling. The antenna apparatus comprises: a loop coil produced by winding a conductive wire in a plane and configured to perform the inductive coupling; and a magnetic member covering one region of the loop coil, provided at one side thereof, from one surface of the loop coil, passing through the loop coil, and covering another region of the loop coil, provided at the other side thereof, from the other surface of the loop coil. The magnetic member covers the loop coil at the one surface and from the other surface, and the entire region of loop coil is therefore covered. 
     The antenna apparatus can be small and thin, can yet increase the communication distance with respect to the electronic apparatus having a communication function and can therefore expand the communication range. 
     Other objects of the invention and the advantages the invention achieves will become apparent from the embodiments that will be described below with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing a conventional RFID system; 
         FIG. 2  is a circuit diagram showing an RFID system that uses an antenna apparatus according to the present invention; 
         FIG. 3  is a plan view showing the antenna apparatus according to this invention; 
         FIG. 4  is a side view depicting the distribution of a magnetic field at the antenna apparatus according to this invention; 
         FIG. 5  is a sectional view taken along line A-A shown in  FIG. 3 ; 
         FIG. 6  is a plan view of an antenna apparatus according to another embodiment of the present invention; 
         FIG. 7  is a plan view of an antenna apparatus, which is comparative example 1 for comparison with the antenna apparatus according to this invention; 
         FIG. 8  is a side view of the antenna apparatus, or comparative example 1; 
         FIG. 9  is a plan view of an antenna apparatus, which is comparative example 2 for comparison with the antenna apparatus according to this invention; 
         FIG. 10  is a side view of the antenna apparatus, or comparative example 2; 
         FIG. 11  is a plan view of an antenna apparatus, which is comparative example 3 for comparison with the antenna apparatus according to this invention; 
         FIG. 12  is a side view of the antenna apparatus, or comparative example 3; 
         FIG. 13  is a plan view of an antenna apparatus, which is comparative example 4 for comparison with the antenna apparatus according to this invention; and 
         FIG. 14  is a side view of the antenna apparatus, or comparative example 4. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Antenna apparatuses according to the embodiment of the present invention will be described with reference to the drawings appended hereto. 
     First, an RFID system using an antenna apparatus according to this embodiment will be explained. As shown in  FIG. 2 , the RFID system comprises a non-contact type IC card  1  and a reader/writer  50  (hereinafter referred to as R/W). The R/W  50  can write data into, and read data from, the IC card  1 . 
     The IC card  1  is a battery-less IC card that does not incorporate a power supply such as a battery, in compliant with, for example, ISO7810 Standard. The IC card  1  is of the same size as a so-called credit card. That is, it is rectangular and has such short sides and long sides that it can be placed, in its entirety, on the palm of the hand. The IC card  1  incorporates a substrate and has a loop antenna  2  and an integrated circuit (IC)  3 . The loop antenna  2  and the IC  3  are mounted on the substrate. The loop antenna  2  receives and transmits data when it is coupled with an electromagnetic field. The IC  3  includes electronic circuits and a memory. The electronic circuits perform various processes. 
     The loop antenna  2  is constituted by a loop coil  4  formed by winding a conductive wire in a plane. The loop coil  4  is connected in parallel to a capacitor  5 . The coil  4  and the capacitor  5  constitute a resonance circuit. The loop antenna  2  is coupled with the electromagnetic field radiated from the loop antenna provided on the R/W  50 , which will be described later. The loop antenna  2  converts the electromagnetic field into an electric signal, which is supplied to the IC. 
     The IC  3  comprises a rectifier circuit  6 , a regulator  7 , a high-pass filter (HPF)  8 , a demodulation circuit  9 , a sequencer  10 , a memory  11 , and a modulation circuit  12 . The rectifier circuit  6  receives the electric signal supplied from the loop coil  4  and rectifies the signal, smoothing the same. The regulator  7  receives the electric signal supplied from the rectifier circuit  6  and converts the signal to AC power. The HPF  8  extracts a high-frequency component from the electric signal supplied from the rectifier circuit  6 . The demodulation circuit  9  demodulates the high-frequency signal input from the HPF  8 . The sequencer  10  controls the data-writing process and data-reading process in accordance with the data supplied from the demodulation circuit  9 . The memory  11  stores the data supplied from the demodulation circuit  9 . The modulation circuit  12  modulates the data transmitted from the loop coil  4 . 
     The rectifier circuit  6  comprises a diode  13 , a resistor  14  and a capacitor  15 . The anode terminal of the diode  13  is connected to one end of the loop coil  4  and to one end of the capacitor  5 . The cathode terminal of the diode  13  is connected the other end of the resistor  14  and the other end of the capacitor  15 . The resistor  14  and the capacitor  15  are connected, at the other end, to the other end of the loop coil  4  and the other end of the capacitor  5 . The rectifier circuit  6  outputs an electric signal generated by rectifying and smoothing the electric signal supplied from the loop coil  4 . The signal output from the rectifier circuit  6  is supplied to the regulator  7  and the HPF  8 . 
     The regulator  7  is connected to the cathode terminal of the diode  13 , to one end of the resistor  14  and to one end of the capacitor  15  of the above-described rectifier circuit  6 . The regulator  7  controls the voltage fluctuation (data component) of tins electric signal supplied from the rectifier circuit  6 , thereby stabilizing this electric signal. The signal thus stabilized is supplied, as DC power, to the sequencer  10 . Thus, the voltage fluctuation that occurs as the IC card  1 , for example, moves and the voltage fluctuation that occurs as the power consumed in the IC card  1  changes, are suppressed. Note that such voltage fluctuations may cause the sequencer  10  to make errors in its operation. 
     The HPF  8  comprises a capacitor  16  and a resistor  17 . It extracts the high-frequency component from the electric signal supplied from the rectifier circuit  6 . The high-frequency component is supplied to the demodulation circuit  9 . 
     The demodulation circuit  9  is connected to the other end of the capacitor  16  and one end of the resistor  17  of the above-described HPF  8 . It demodulates the high-frequency signal input from the HPF  8  and outputs the signal to the sequencer  10 . 
     The sequencer  10  incorporates a read only memory (ROM) and a random access memory (RAM) and is connected to the demodulation circuit  9 . In the sequencer  10 , the signal (command) input from the demodulation circuit  9  is stored into the RAM and is analyzed in accordance with tire program stored in the ROM. On the basis of the results of analysis, the data stored in the memory  11  is read as needed, or the data supplied from the demodulation circuit  9  is written into the memory  11 . The sequencer  10  generates a response signal, which is supplied to the modulation circuit  12 , giving a response to the command. 
     The memory  11  is constituted by a nonvolatile memory such as an electrically erasable programmable read-only memory (EEPROM) and is connected to the sequencer  10  described above. The memory  11  stores the data supplied from the demodulation circuit  9  on the basis of the results of the analysis performed by the sequencer  10 . 
     The modulation circuit  12  is constituted by a serial circuit of impedance  18  and a field-effect transistor (FET)  19 . The impedance  18  is connected, at one end, to the cathode terminal of the diode  13  provided in the rectifier circuit  6 , and at the other end, to the drain terminal of the FET  19 . The source terminal of the FET  19  is connected to the ground. The gate terminal of the FET  19  is connected to the sequencer  10 . The modulation circuit  12  is connected in parallel to the loop coil  4  that constitutes the above-mentioned resonance circuit. The modulation circuit  12  causes the FET  19  to perform switching in accordance with the signal supplied from the sequencer  10 . Namely, the modulation circuit  12  performs so-called added modulation, causing fluctuation of the load of the impedance  18 , with respect to the loop coil  4 . 
     On the other hand, the R/W  50  comprises a control circuit  51 , a modulation circuit  52 , a demodulation circuit  53 , and a loop antenna  54 . The control circuit  51  controls the data to be transmitted and received. The modulation circuit  52  modulates data, and the demodulation circuit  53  demodulates data. The loop antenna  54  transmits and receives data when coupled with an electromagnetic field. 
     The control circuit  51  generates control signals in accordance with the instructions externally input or the program stored. The control signals control the modulation circuit  52  and the demodulation circuit  53  and generate transmission data that corresponds to the instructions. The transmission data is supplied to the modulation circuit  52 . Further, the control circuit  51  reproduces data from the response data supplied from the demodulation circuit  53 . The data thus reproduced is output to an external apparatus. 
     The modulation circuit  52  modulates the transmission data input from the control circuit  51 . The data modulated is supplied to the loop antenna  54 . 
     The demodulation circuit  53  demodulates a modulated wave supplied from the loop antenna  54 , generating demodulated data. This data is supplied to the control circuit  51 . 
     The loop antenna  54  is constituted by a loop coil formed by winding a conductive wire in a plane. The antenna  54  radiates an electromagnetic field that corresponds to the modulated wave supplied from the modulating circuit  52 . The antenna  54  also detects the load fluctuation of the loop coil  4 . A capacitor for resonance may be connected in parallel or in series to the loop antenna  54 , in accordance with the drive-circuit system of the R/W  50 . 
     In the RFID system so configured as described above, when a data-write instruction is given to the IC card  1  the control circuit  51  of the R/W  50  generates a write command signal in accordance with the instruction. At the same time, the control circuit  51  generates transmission data (data to be written) that accords with the data-write instruction. The transmission data is supplied to the modulation circuit  52 . The modulation circuit  52  then modulates the amplitude of the oscillation signal. The signal thus modulated is supplied to the loop antenna  54 . The loop antenna  54  radiates an electromagnetic signal corresponding to the modulated signal input to the R/W  50 . 
     The resonance circuit provided in the IC card  1  and constituted by the loop coil  4  and the capacitor  5  has a resonance frequency of, for example, 13.56 MHz. This frequency corresponds to the oscillation frequency (carrier frequency) of the signal transmitted from the R/W  50 . Hence, the resonance circuit performs resonance, receiving the electromagnetic field radiated from the loop antenna  54 . The resonance circuit converts the electromagnetic field into an electric signal, which is then supplied to the IC  3 . In the IC  3 , the electric signal is input to the rectifier circuit  6 . The rectifier circuit  6  rectifies the signal, smoothing the same. The electric signal thus smoothed is supplied to the regulator  7 . The regulator  7  controls the voltage fluctuation (data component) of the electric signal supplied from the rectifier circuit  6 , thereby stabilizing this electric signal. The signal thus stabilized is supplied, as DC power, to the sequencer  10 . 
     The signal smoothed by the rectifier circuit  6  is supplied via the modulation circuit  12  to the HPF  8 . The HPF  8  extracts the high-frequency component from the electric signal supplied from the rectifier circuit  6 . The high-frequency component is supplied to the demodulation circuit  9 . The demodulation circuit  9  demodulates the high-frequency signal input to it. The signal demodulated is supplied to the sequencer  10 . The sequencer  10  makes the RAM store the signal (command) input from the demodulation circuit  9 . Using the program stored in the ROM, the sequencer  10  analyzes the signal. On the basis of the results of the analysis performed by the sequencer  10 , the memory  11  stores the data supplied from the demodulation circuit  9 . 
     If the signal (command) input from the demodulation circuit  9  is a read instruction, the sequencer  10  reads from the memory  11  the data that corresponds to this instruction. In accordance with the data read from the memory  11 , the sequencer  10  performs switching on the FET  19  of the modulation circuit  12 . When the FET  19  is turned on in the modulation circuit  12 , the loop coil  4  is connected to the impedance  18 . When the FET  19  is turned off, the loop coil  4  is no longer connected in series to the impedance  18 . Thus, the impedance of the loop antenna  54  of the R/W  50 , which remains magnetically coupled with the loop antenna  2  of the IC card  1 , changes in accordance with the read data. As a result, the terminal voltage of the loop antenna  54  varies with this impedance. The demodulation circuit  53  demodulates this variation of the terminal voltage, whereby the R/W  50  can receive the read data. 
     Thus, communication is accomplished between the IC card  1  and the R/W  50 . Namely, the R/W  50  can write data into, and read data from, the IC card  1 , though it does not contact the IC card  1  at all. 
     The loop antenna  2  provided on the IC card  1  is an antenna apparatus  60  so constituted as shown in  FIGS. 3 ,  4  and  5 . The antenna apparatus  60  comprises a loop coil  61  and a magnetic member  62 . The loop coil  61  is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member  62  covers one region  61   a  of the loop coil  61 , from one surface F 1  of the loop coil  61 . The magnetic member  62  passes through the loop coil  61  and covers the other region  61   b  of the loop coil  61 , from the other surface F 2  of the loop coil  61 . That is, the loop coil  61  is covered by the magnetic member  62  from one surface F 1  and also from the other surface F 2 , thus the entire region of the loop coil  61  is covered, at both surfaces. 
     The loop coil  61  has been formed by etching foils of conductive metal, such as electrolyte copper, provided on both surfaces of a flexible insulating film or substrate made of, for example, polyimide, PET or the like. The method of forming the loop coil  61  is not limited to this. The loop coil  61  may be formed by printing conductor patterns made of conductive paste such as silver paste, or by sputtering a metal target and thereby forming conductor patterns on the substrate. The regions  61   a  and  61   b  of the loop coil  61  cover regions  61   d  and  61   e  that are opposed to the conductive wire that forms a rectangular coil. The loop coil  61  has an insertion hole  61   c , through which magnetic member  62  is inserted and held. The insertion hole  61   c  is circular or elliptical, having three or more apexes. The turns of the loop coil, which lie at one side, may be arranged at intervals different from those at the opposite side. In this case, the loop coil is an asymmetrical one, further increasing the communicable range. 
     The magnetic member  62  has a first part  62   a , a second part  62   b  and an insertion part  62   c . The first part  62   a  covers the first region  61   a  of the loop coil  61 , from one surface F 1  thereof. The second part  62   b  covers the other region  61   b  of the loop coil  61 , from the other surface F 2  thereof. The insertion part  62   c  passes through the insertion hole  61   c  and connects the first and second parts  62   a  and  62   b . That part of the surface F 1 , which is not covered with the magnetic member  62 , serves as a communication region. Namely, the surface F 1  is opposed to the R/W  50  to achieve communication with the R/W  50 . 
     The region  61   b  of the loop coil  61 , which is covered with the second part  62   b  of the magnetic member  62 , has a larger area than the region  61   a  of the loop coil  61 , which is covered with the first part  62   a  of the magnetic member  62 . The exposed part of the other region  61   b  of the loop coil  61 , i.e., the part not covered with the second part  62   b  of the magnetic member  62 , that is the one surface F 1  is used as communication region. 
     The magnetic member  62  is broader and longer than the loop coil  61 . The first part  62   a  and the second part  62   b  cover the surfaces F 1  and F 2 , respectively, whereby the loop coil  61  is covered in its entirety, at both surfaces. 
     The insertion part  62   c  of the magnetic member  62  is narrower and shorter than the first and second parts  62   a  and  62   b  thereof. That is, the magnetic member  62  has notches in both lateral edges of the insertion part  62   c . These notches define the first part  62   a , the second part  62   b  and the insertion part  62   c . The length of the notches may appropriately be selected in accordance with the thickness of the magnetic member  62  and the size of the insertion hole  61   c  of the loop coil  61 . The first and second parts  62   a  and  62   b  are formed but not limited by cutting notches. The first and second parts  62   a  and  62   b  may be prepared independently and may then be jointed at the opening part. If this is the case, the loop coil may have regions covered, at both surfaces, with the first and second parts of the magnetic member  62 . 
     To manufacture the magnetic member  62 , a magnetic paint is prepared, by mixing a binder made of rubber-based resin, with magnetic powder, a solvent and an additive. Hie magnetic powder is made of Fe-based material that contains 96 wt % of Fe, 3 wt % of Cr, 0.3 wt % of Co and some other magnetic materials. The magnetic paint is filtered, removing, from the binder, any magnetic particles having diameters larger than a predetermined value. In an extrusion molding machine, the magnetic paint is extruded from a tank through a nip between a pair of rollers, thereby forming a long magnetic: strip. The magnetic strip is dried, removing the solvent therefrom. 
     Then, in a coating machine, one major surface of the magnetic strip is coated with adhesive while the strip passes through the nip between a pair of rollers. Further, the magnetic strip is punch-pressed, forming a magnetic member  62 . 
     The magnetic member  62  can be made of any soft magnetic material and produced by any method, so long as it exhibits satisfactory magnetic characteristics. The magnetic material may be, for example, amorphous alloy, Co—Cr alloy, Fe—Al alloy, Sendust alloy (Fe—Al—Si), Fe—Ni alloy, Fe—Co—Ni alloy or the like. Powder of such an alloy is kneaded with a rubber-based binder and dispersed in the binder, providing a paste. The paste is applied, forming the magnetic member. Alternatively, the magnetic member may be a thin soft magnetic plate formed by electroplating or sputtering. Still alternatively, the magnetic member may be a thin bulk plate made of only one material such as ferrite-based powder (Ni—Zn ferrite or Mn—Zn ferrite), press-sintered and containing no binder. Moreover, an insulating layer may be formed on the plate made of the above-mentioned powder. To provide the insulating layer, an oxide film may be formed by heating and then be annealed, or an oxide film may be formed by sputtering on the plate made of the powder. The magnetic member may be a sheet that has flexibility. Otherwise, it may be a hard plate made of sintered material, such as a ferrite plate. 
     The magnetic material  62  has, in its in-plane direction, an effective magnetic permeability μ′ (real-number part) of 30 or more and an effective magnetic permeability μ″ (imaginary-number part) of 1.0 or less, each at the communication frequency. Since the magnetic material  62  has effective magnetic permeability μ′ of 30 or more and effective magnetic permeability μ″ of 1.0 or less in the antenna apparatus  60 , the range of communication between the IC card  1  and the R/W  50  can be expanded even if the thickness of the magnetic material is reduced. If the effective magnetic permeability μ′ is 50 or more, the communication distance can be increased. 
     To manufacture the antenna apparatus  60 , an IC chip  63  is connected to the loop coil  61  that has been produced as described above. As a result, the IC chip  63  and the coil  61  constitute a resonance circuit. The IC chip  63  used is, for example, an IC chip that accords with ISO 14443 Standard or ISO 15693 Standard. The IC chip  63  is connected to the loop coil by ACF method or wire bonding. Nonetheless, the method of connecting the IC chip is not limited in particular. Next, an insertion hole  61   c  is made at the center part of the loop coil  61 , so that the magnetic member  62  may pass through the loop coil  61 . The insertion part  62   c  of the magnetic member  62  is inserted in the insertion hole  61   c . The first part  62   a  covers the first region  61   a  of the loop coil  61  at one surface F 1 , and the second part  62   b  covers the other region  61   b  of the loop coil  61  at the other surface F 2 . In this condition, the loop coil  61  and the magnetic member  62  are bonded to each other. At this time, the magnetic member  62  is so positioned that the adhesive-coated surface faces the major surface that is opposed to the loop coil  61 . The antenna apparatus  60  can thus be manufactured. Since the loop coil  61  and the magnetic member  62  are bonded to each other with adhesive, with the member  62  inserted in the insertion hole  61   c , the antenna apparatus  60  can be easily manufactured in view of its structure. In addition, antenna apparatus  60  can be thin and small because the thickness of both the magnetic member  62  and the loop coil  61  can be reduced. 
     A magnetic field is distributed at the antenna apparatus  60  thus configured, as is illustrated in  FIG. 4 . That is, the magnetic field is intense at one surface F 1  of the loop coil  61 , which is opposite to the other region  61   b  that is covered with the second part  62   b  of the magnetic member  62 , which has a larger area than the first part  61   a . That is, the distribution of the magnetic field at the antenna apparatus  60  is asymmetrical, unlike the symmetrical distribution of the magnetic field that the conventional antenna apparatus generates. Moreover, the intensity of the magnetic field can be adjusted by changing the areas of the regions that the first and second parts  62   a  and  62   b  cover, respectively. 
     Hence, the antenna apparatus  60  can increase the communication distance between the IC card  1  and the R/W  50  by controlling the distribution of the magnetic field radiated from the loop coil  61  and can widen the communicable range. The antenna apparatus  60  can enable the IC card  1  and the R/W  50  to communicate with each other. That is, the R/W  50  can write data into, and read data from, the IC card  1 , without contacting the IC card  1 . 
     In the antenna apparatus  60  according to the embodiment of this invention, the magnetic member  62  is arranged as shown in  FIG. 4 , covering the first region  61   a  of the loop coil  61  at one surface F 1 , and passes through the loop coil  61 , covering the other region  61   b  and at the other surface of the loop coil  61 . Thus, the magnetic member  62  covers all regions of the loop coil  61 , at one surface and the other surface, whereby the magnetic field distribution at one surface F 1  of the loop coil  61  can be emphasized. The antenna apparatus  60  can therefore be made thin and small. Further, since the intensity of the magnetic field is increased, the range of the communication between the IC card  1  and the R/W  50  can be expanded. 
     In the antenna apparatus  60  according to the embodiment of the present invention, the magnetic field distribution at one surface F 1  of the loop coil  61  is emphasized and the magnetic member used has a predetermined effective magnetic permeability μ′ and a predetermined effective magnetic permeability μ″. Therefore, the antenna apparatus can be thin and can expand the communication range, greatly increasing the communication distance in a free space. In addition, the influence of any metal member can be reduced, greatly increasing the communication range in the metal member. 
     As described above, the antenna apparatus  60  according to this invention improves the readiness of the communication between the IC card  1  and the R/W  50  and enables the R/W  50  to write data into, and read data from, the IC card  1 , reliably without contacting the IC card  1 . 
     The loop antenna  2  provided on the IC card  1  may be such an antenna apparatus  70  as shown in  FIG. 6 . This antenna apparatus  70  is asymmetrical, because the opposing sides of the loop coil differ in terms of the width of windings and/or the intervals thereof. 
     As  FIG. 6  shows, the antenna apparatus  70  comprises a loop coil  71  and a magnetic member  72 . The loop coil  71  is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member  72  covers one region  71   a  of the loop coil  71 , from one surface of the loop coil  71 . It passes through the loop coil  71  and covers the other region  71   b  of the loop coil  71 , from the other surface of the loop coil  71 . That is, the loop coil  71  is covered with the magnetic member  72  at all regions from both surfaces. The loop coil  71  has been manufactured in the same way as the loop coil  61  described above. The loop coil  71  is formed asymmetrical in terms of the widths of windings at the opposing sides. Namely, the part  71   e  covered with the region  71   b  of the loop coil  71  has a greater winding width than the part  71   d  covered with the region  71   a . Further, the loop coil  71  has an insertion hole  71   c , through which magnetic member  72  is inserted and held. Tire insertion hole  71   c  is circular or elliptical, having three or more apexes. 
     The magnetic member  72  has a first part  72   a , a second part  72   b  and an insertion part  72   c . The first part  72   a  covers the one region  71   a  of the loop coil  71 , from one surface thereof. The second part  72   b  covers the other region  71   b  of the loop coil  71 , from the other surface thereof. The insertion part  72   c  passes through the insertion hole  71   c  formed in the loop coil and connects the first and second pails  72   a  and  72   b . That part of one surface, which is not covered with the magnetic member  72 , serves as communication region. Thus, this surface of the loop coil  71  is opposed to the R/W  50 . 
     The region  71   b  of the loop coil  71 , which is covered with the second part  72   b  of the magnetic member  72 , has a larger area than the region  71   a  of the loop coil  71 , which is covered with the first part  72   a  of the magnetic member  72 . The part  71   e  at which the loop coil  71  has a large winding width is arranged in the other region  71   b  that is covered with the second part  72   b  having a large area. The exposed part of the other region  71   b  of the loop coil  71 , i.e., the part not covered with the second part  72   b  of the magnetic member  72 , which has a large area, is used as communication region. 
     The magnetic member  72  is broader and longer man tire loop coil  71 . The first part  72   a  and the second part  72   b  cover one surface and the other surface, respectively, whereby the loop coil  72  is covered in its entirety, at both surfaces. 
     The insertion part  72   c  of the magnetic member  72  is narrower than the first and second parts  72   a  and  72   b  thereof. That is, the magnetic member  72  has notches in both lateral edges of the insertion part  72   c . These notches define the first part  72   a , the second part  72   b  and the insertion part  72   c . The length of the notches may appropriately be determined by the thickness of the magnetic member  72  and the size of the insertion hole  71   c  of the loop coil  71 . The first and second parts  72   a  and  72   b  are formed but not limited by cutting notches. The first and second parts  72   a  and  72   b  may be prepared independently and may then be jointed at the opening part. If this is the case, the loop coil may have regions that are covered, at both surfaces, with the first and second parts of the magnetic member. This magnetic member  72  is manufactured in the same way as the above-described magnetic member  62 . Therefore, how it is made will not be explained in detail. 
     To manufacture the antenna apparatus  70  according to the present invention, an IC chip  73  is connected to the loop coil  71  produced as described above. As a result, the IC chip  73  and the coil  71  constitute a resonance circuit. The IC chip  73  is the same as the IC chip  63  described above, and the method of connecting the chip  73  is the same as the method of connecting the chip  63 . Further, the method of bonding the magnetic member  72  to the loop coil  71  is the same as in manufacturing the antenna apparatus  60  described above. 
     The magnetic field distribution at the antenna apparatus  70  thus configured is emphasized at one surface that is opposed to that surface of the other region  71   b  covered with the second part  72   b  having a large area from the regions of the loop coil  71  which is covered with the first and second parts  72   a  and  72   b  of the magnetic member  72 . This is because the second parts  72   b  having a large area is covered and also because the winding width of the other part  71   e  of the loop coil  71 , which is arranged in the other region  71   b  covered with the second part  72   b , is broader than the part  71   d . Here, the winding width of the part  71   e  of the loop coil  71  arranged in the other region  71   b  covered with the second part  72   b  is broader than the part  71   d . Nevertheless, the same advantage can be attained even if the turns of the winding at the part  71   e  are arranged at longer intervals than at the part  71   d.    
     That is, the distribution of the magnetic field at the antenna apparatus  70  is asymmetrical, unlike the symmetrical distribution of the magnetic field that the conventional antenna apparatus generates. Moreover, the intensity of the magnetic field can be adjusted by changing the areas of the regions that the first and second parts  62   a  and  62   b  cover, respectively, and by changing the intervals and/or width of the rums of the winding at the other part  71   e  of the loop coil  71 , which are arranged in the other region  71   b  that is covered with the second part  72   b.    
     Therefore, this antenna apparatus  70  can increase the communication distance between the IC card  1  and the R/W  50  by controlling the distribution of the magnetic field radiated from the loop coil  71  and can widen the communicable range. The antenna apparatus  70  can enable the IC card  1  and the R/W  50  to communicate with each other. That is, the R/W  50  can write data into, and read data from, the IC card  1 , without contacting the IC card  1 . 
     In the antenna apparatus  70  according to the present invention, the magnetic member  72  is arranged, covering one region  71   a  of the loop coil  71  at one surface, and passes through the loop coil  71 , covering the other region  71   b  at the other surface. Thus, the magnetic member  72  covers all regions of the loop coil  71 , at one surface and the other surface. In addition, the winding width of the pail  71   e  of the loop coil  71  arranged in the other region covered at the other surface is broader than the part  71   d . Hence, only the magnetic field distribution at one surface of the loop coil  71  can be emphasized. The antenna apparatus  70  can therefore be made thin and small. Moreover, the antenna apparatus  70  can expand the range of the communication between the IC card  1  and the R/W  50 , because the intensity of the magnetic field is increased. 
     In the antenna apparatus  70  according to the present invention, the magnetic field distribution at one surface F 1  of the loop coil  71  is emphasized and the magnetic member used has a predetermined effective magnetic permeability μ′ and a predetermined effective magnetic permeability μ″. Therefore, the antenna apparatus can be thin and can expand the communication range, greatly increasing the communication distance in a free space. Furthermore, the influence of any metal member can be reduced, greatly increasing the communication range in the metal member. 
     As described above, the antenna apparatus  70  according to this invention improves the readiness of the communication between the IC card  1  and the R/W  50  and enables the R/W  50  to write data into, and read data from, the IC card  1 , reliably without contacting the IC card  1 . 
     Embodiments of the antenna apparatus  60  according to the present invention will be described below. More precisely, four comparative examples of the antenna apparatus  60  according to this invention will be described with reference to  FIG. 7  to  FIG. 14 . 
     Antenna apparatus  110 , i.e., comparative example 1, comprises a loop coil  111  and a magnetic member  112  as shown in  FIG. 7  and  FIG. 8 . The loop coil  111  is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member  112  is bonded to the surface of the loop coil  111 , which faces away from the surface that may face an IC card  1 . The magnetic member  112  is broader and longer than the loop coil  111 . 
     Antenna apparatus  120 , i.e., comparative example 2, comprises a loop coil  121  and a magnetic member  122  as shown in  FIG. 9  and  FIG. 10 . The loop coil  121  is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member  122  is bonded to the surface of the loop coil  121 , which faces away from the surface that may face an IC card  1 . The magnetic member  122  is narrower and shorter than the loop coil  121 . 
     Antenna apparatus  130 , i.e., comparative example 3, comprises a loop coil  131  and a magnetic member  132  as shown in  FIG. 11  and  FIG. 12 . The loop coil  131  is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member  132  is bonded to the loop coil  131 , such that it passes through the insertion hole of the loop coil  131  and is bonded, covering a part of the coil  131  at one surface and covering another part of the coil  131  at the other surface. The magnetic member  132  is narrower and longer than the loop coil  131 . 
     Antenna apparatus  140 , i.e., comparative example 4, comprises a loop coil  141  and a magnetic member  142  as shown in  FIG. 13  and  FIG. 14 . The loop coil  141  is produced by winding a conductive wire in a plane. The magnetic member  142  is bonded to the loop coil  141 , such that it passes through the insertion hole of the loop coil  141  and is bonded, covering a pail of the coil  141  at one surface and covering another part of the coil  141  at the other surface. The magnetic member  142  is narrower and shorter than the loop coil  141 . 
     Assume that embodiments 1 and 2 of the same structure as the antenna apparatus  60  according to this invention and the antenna apparatuses  110 ,  120 ,  130  and  140 , i.e., comparative examples 1 to 4, each have such effective magnetic permeabilities μ′ and μ″ as shown in the following Table 1. These antenna apparatuses were evaluated for the communication distances they achieve. Table 1 shows the communicable distance in a metal member and the communicable distance in a free space, which each apparatus achieved. Note that embodiment 1 and comparative example 1 have a magnetic member made of ferrite-based magnetic material and that embodiment 2 and comparative example 2 have a magnetic member made of Fe—Si—Cr-based magnetic material. The effective magnetic permeability μ′ is the AC specific permeability measured at the earner frequency (13.56 MHz) by an impedance analyzer or the like, for ring-shaped samples, each comprising a ring having a diameter (φ) of, for example, 7 mm and a 5-turn wire coil wound around the ring. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Example 
                 Example 
                 Comparative 
                 Comparative 
                 Comparative 
                 Comparative 
               
               
                   
                 1 
                 2 
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Structure 
                 Antenna 
                 Antenna 
                 Antenna 
                 Antenna 
                 Antenna 
               
               
                   
                 apparatus 
                 apparatus 
                 apparatus 
                 apparatus 
                 apparatus 
               
               
                   
                 60 
                 110 
                 120 
                 130 
                 140 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Frequency [MHz] 
                 13.56 
                 13.56 
                 13.56 
                 13.56 
                 13.56 
                 13.56 
               
               
                 at the measuring 
               
               
                 point 
               
               
                 Effective magnetic 
                 30 
                 40 
                 30 
                 30 
                 30 
                 30 
               
               
                 permeability μ′ 
               
               
                 (real-number part) 
               
               
                 Effective magnetic 
                 0.4 
                 0.1 
                 0.4 
                 0.4 
                 0.4 
                 0.4 
               
               
                 permeability μ″ 
               
               
                 (imaginary-number 
               
               
                 part) 
               
               
                 Result 
                 30 mm 
                 35 mm 
                 20 mm 
                 15 mm 
                 22 mm 
                 20 mm 
               
               
                 (communicable 
               
               
                 distance in a metal 
               
               
                 member) 
               
               
                 Result 
                 40 mm 
                 40 mm 
                 40 mm 
                 40 mm 
                 40 mm 
                 40 mm 
               
               
                 (communicable 
               
               
                 distance in a free 
               
               
                 space) 
               
               
                   
               
            
           
         
       
     
     As seen from Table 1, embodiments 1 and 2, i.e., antenna apparatuses  60  according to the invention, can increase not only the communicable distance in a free space, but also the communicable distance in a metal member. That is, they can expand the communicable range. 
     Further, in the antenna apparatuses, i.e., embodiments 1 and 2, the effective magnetic permeability μ′ and the effective magnetic permeability μ″, both measured at the communication frequency in the in-plane direction of the magnetic member, can be 30 or more and 1.0 or less, respectively. Moreover, they can expand the range of communication between the IC card  1  and the R/W  50 . 
     Embodiments of the present invention have been described, with reference to the drawings. Nonetheless, the invention is not limited to the embodiments. As is obvious to those skilled in the art, various changes, replacements and the like can be made, without departing from the scope of the claims appended hereto.