Patent Publication Number: US-8967487-B2

Title: Non-contact communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. JP 2011-174983 filed in the Japanese Patent Office on Aug. 10, 2011, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     The present technology relates to a non-contact communication device, and more particularly, to a non-contact communication device capable of improving communication performance of non-contact communication. 
     An integrated circuit (IC) card for exchanging data through non-contact communication is much more convenient to use than a medium (for example, a magnetic card) in which data reading/writing is performed in a contact state. In recent years, for example, since the IC card has been widely utilized in ticket systems of railroad systems and the like, electronic money systems for payment in stores such as convenience stores, entrance and exit systems for managing entrances and exits to/from rooms of a company, etc. demands therefor have increased more and more. 
     For example, an IC card of an entrance and exit system has an IC chip with an entrance and exit ID (identification) as information for identifying a user possessing the IC card, and a photograph of a user&#39;s face and/or a name is displayed on the surface thereof. 
     In the entrance and exit system, a reader/writer (R/W) is installed around a doorway of a room to perform non-contact communication with the IC card, and if a user passes the IC card over the R/W, data exchange and other processes are quickly performed between the IC card and the R/W through non-contact communication in order to permit the entrance and exit to/from the room. 
     Non-contact communication devices for performing non-contact communication with the R/W include a portable terminal such as a cellular phone having a function of the IC card, a token-shaped IC tag (a wireless tag) in which the top and bottom of an IC chip are sandwiched by a resin case, and the like in addition to a card-shaped IC card, and the portable terminal or the IC tag has also been spread as a non-contact communication device, in addition to the IC card. 
     Here, a communication device performing non-contact communication will also be referred to as a non-contact communication device. 
     Both the R/W and the IC card, which transmit data to each other through non-contact communication, are non-contact communication devices. 
     The R/W outputs a radio frequency (RF) signal by itself, modulates the RF signal, and transmits data. 
     Meanwhile, for example, the IC card and the like having no power supply is driven by obtaining power from the RF signal output from the R/W, and load-modulates the RF signal to transmit data. 
     Hereinafter, a non-contact communication device such as the R/W, which outputs an RF signal and modulates the RF signal to transmit data, will also be appropriately referred to as an initiator, and a non-contact communication device such as the IC card, which is driven by obtaining power from the RF signal output from the initiator and load-modulates the RF signal to transmit data, will also be referred to as a target. 
     The IC card and the like serving as the target include electronic parts such as an IC chip, one (loop) coil, or a capacitor. 
     That is, in the IC card, for example, the IC chip, the capacitor and the like are connected to the coil as an antenna. If the IC card approaches the R/W and the like serving as the initiator, current flows through the coil serving as the antenna of the IC card due to electromagnetic induction by the RF signal output from the R/W, and the IC chip connected to the coil is driven by power obtained from the current. 
     In addition, by the capacitor connected to the coil serving as the antenna, a resonance frequency of a resonance circuit including the capacitor and the coil is adjusted. 
     For example, Japanese Unexamined Patent Application Publication No. 2007-328634 has proposed an R/W capable of simply adjusting a resonance frequency by closely electromagnetically coupling a main antenna coil and a sub-antenna coil to each other such that a coupling coefficient approaches 1 to a maximum extent, wherein the main antenna coil and the sub-antenna coil are not directly electrically connected to each other. 
     Furthermore, for example, Japanese Unexamined Patent Application Publication No. 2004-145453 has proposed an IC module which allows a single semiconductor circuit chip to integrally have an R/W function and an IC card function through a first loop antenna connected to an input/output terminal of a card IC function unit, and a second loop antenna connected to an input/output terminal of a reader/writer function unit and arranged inside the first loop antenna. 
     SUMMARY 
     Meanwhile, in recent years, the R/W is prepared in the form of a module and a module of the R/W (an R/W module) is installed in various devices, thereby serving as the R/W as a whole in many cases. 
     Since an antenna of the R/W module installed in a device has various shapes and sizes, it may be difficult for the R/W module to ensure constant communication performance with respect to the IC card and the like serving as a target. 
     Furthermore, when the R/W module, for example, is installed in a so-called notebook personal computer (PC), only a vicinity of the antenna of the R/W module in the notebook PC is formed by a resin casing, and other parts, that is, parts slightly separated from the antenna (parts outside the antenna), are formed by a metal casing in order to ensure physical strength. 
     Meanwhile, since the IC card and the like serving as a target are designed and manufactured in consideration of non-contact communication on a free space (a state in which there is no surrounding metallic body), when parts outside the antenna of the R/W module are formed by the metal casing, it is probable that communication performance between the IC card and the R/W (the notebook PC having the R/W module therein) may significantly deteriorate under the influence of the metal casing. 
     Moreover, since the R/W may be an R/W causing unnecessary radiation noise, communication performance between the IC card and the R/W may deteriorate due to the unnecessary radiation noise. 
     In light of the foregoing, it is desirable to improve communication performance of non-contact communication. 
     A non-contact communication device of the present technology includes an antenna configured to transmit data through non-contact communication after load-modulation of an RF signal from a reader/writer (R/W), wherein the antenna includes: a standard coil having an aperture with a predetermined size; and a small coil having an aperture with a size smaller than a size of the standard coil, wherein the standard coil and the small coil are connected in series or in parallel, and the small coil is arranged such that the aperture of the small coil overlaps a winding part of a coil that is an antenna of the R/W when the non-contact communication device is caused to face the R/W by matching a predetermined position of the non-contact communication device with a reference position of the R/W that is determined in advance as a position with which the predetermined position of the non-contact communication device is to be matched in causing the non-contact communication device to face the R/W. 
     In the non-contact communication device of the present technology, there is provided the antenna in which the standard coil and the small coil are connected in series or in parallel, wherein the standard coil has the aperture with the predetermined size and the small coil has the aperture with the size smaller than the size of the standard coil. The small coil is arranged such that the aperture of the small coil overlaps a winding part of a coil that is an antenna of the R/W when the non-contact communication device is caused to face the R/W by matching a predetermined position of the non-contact communication device with a reference position of the R/W that is determined in advance as a position with which the predetermined position of the non-contact communication device is to be matched in causing the non-contact communication device to face the R/W. 
     In addition, the non-contact communication device may be an independent device, or may be an internal block constituting one device. 
     According to the present technology, it is possible to improve communication performance of non-contact communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a communication distance between a strong electric field-type R/W and an IC card having a different antenna aperture area of an aperture of a coil serving as an antenna; 
         FIG. 2  is a plan view illustrating a state in which an IC card is placed on an R/W which is an on-top device; 
         FIG. 3  is a diagram describing an offset amount; 
         FIG. 4  is a diagram illustrating a correct communication rate of an IC card  10  with respect to each offset amount (x, y); 
         FIG. 5  is a diagram illustrating the presence or absence of a communication dead zone, which indicates whether the communication dead zone occurs in the IC card  10 ; 
         FIG. 6  is a diagram illustrating a configuration example of an embodiment of a communication system employing the present technology; 
         FIG. 7  is a block diagram illustrating an electrical configuration example of a non-contact communication device (R/W)  111 ; 
         FIG. 8  is a block diagram illustrating an electrical configuration example of a non-contact communication device (an IC card)  112 ; 
         FIG. 9  is a plan view illustrating a physical configuration example of the IC card  112 ; 
         FIG. 10  is a plan view illustrating a first configuration example of a set of antennas  21  and  141  for satisfying a predetermined positional relation; 
         FIG. 11  is a plan view illustrating a second configuration example of the set of antennas  21  and  141  for satisfying a predetermined positional relation; 
         FIG. 12  is a plan view illustrating a third configuration example of the set of antennas  21  and  141  for satisfying a predetermined positional relation 
         FIG. 13  is a plan view illustrating a fourth configuration example of the set of antennas  21  and  141  for satisfying a predetermined positional relation; 
         FIG. 14  is a diagram illustrating a relation between a distance from an IC card to an R/W and a coupling coefficient; 
         FIG. 15  is a diagram illustrating coupling coefficients of a 2-coil R/W  20  and each of a 1-coil card  10  and a 3-coil card  112 ; 
         FIG. 16  is a diagram illustrating a correct communication rate for each offset amount (x, y) of the 3-coil card  112 ; 
         FIG. 17  is a diagram illustrating the presence or absence of a communication dead zone, which indicates whether the communication dead zone occurs in the 3-coil card  112 ; and 
         FIG. 18  is a diagram illustrating the presence or absence of a communication dead zone, which indicates whether the communication dead zone occurs in the 3-coil card  112 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, preferred embodiments of the present technology will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     [Communication Performance] 
     Hereinafter, among targets, an IC card will be mainly described. However, the present technology can be applied to a portable terminal having the function of the IC card, an IC tag, and other targets for load-modulating an RF signal to transmit data, in addition to the IC card. 
     Communication performance of an IC card and the like serving as a target for performing non-contact communication, for example, includes a communication distance for allowing non-contact communication to be performed between the IC card and an R/W in the case in which the IC card is passed over the R/W, and offset characteristics indicating tolerance against position shift (offset) of the IC card from an ideal position of the IC card with respect to the R/W in the case in which the IC card is used while being directly placed on the R/W (making close contact with the R/W). 
     The IC card is required to ensure a communication distance to a certain degree, and to have offset characteristics for enabling non-contact communication between the IC card and the R/W even when the IC card is placed on the R/W in the state in which the IC card has been offset from the ideal position to a certain degree. 
     Here, superior offset characteristics mean that the non-contact communication is possible between the IC card and the R/W even when the IC card has been offset from the ideal position to a certain degree. 
       FIG. 1  is a diagram illustrating a communication distance between a strong electric field-type R/W and an IC card having a different antenna aperture area of an aperture of a coil serving as an antenna. 
     In  FIG. 1 , a horizontal axis denotes the antenna aperture area of the IC card and a vertical axis denotes the communication distance. 
     Referring to  FIG. 1 , it can be understood that the communication distance is increased in proportion to the antenna aperture area. 
     Here, the strong electric field-type R/W is an R/W that outputs an RF signal of a large level equal to or more than a certain level, and will also be referred to as a strong electric field device in the following description. 
     Meanwhile, the offset characteristics indicate communication performance needed to ensure a certain degree of efficiency in non-contact communication with the R/W (hereinafter, also referred to as an on-top device) on which the IC card is directly placed. However, in the on-top device, as with the aforementioned notebook PC, only a vicinity of the antenna of the R/W module is formed by a resin casing, and other parts are formed by a metal casing. 
       FIG. 2  is a plan view illustrating a state in which the IC card is placed on the R/W which is the on-top device. 
       FIG. 2  illustrates a state in which an IC card  10  is placed on an R/W  20  which is the on-top device. 
     The IC card  10  has one coil as an antenna  11  and an IC chip  12  therein. 
     In addition,  FIG. 2  illustrates the antenna  11  and the IC chip  12  to be seen. However, the antenna  11  and the IC chip  12  are actually not seen because they are embedded in the IC card  10 . 
     The R/W  20 , which is an on-top device, has an R/W module (not illustrated) therein. 
     In  FIG. 2 , in the R/W  20 , a vicinity (an aperture of a coil, a winding part of the coil, and a part of an outer side (a side other than the aperture) of the winding part while making contact with the winding part) of the (one) coil which is an antenna  21  of the R/W module is formed by a resin casing  22 , and other parts are formed by a metal casing  23 . 
     In addition,  FIG. 2  illustrates the antenna  21  (of the R/W module) of the R/W  20  to be seen. However, the antenna  21  is actually not seen because it is provided inside the resin casing  22  (the R/W  20 ). 
     As illustrated in  FIG. 2 , when an antenna aperture area of the antenna  11  of the IC card  10  is larger than an antenna aperture area of the antenna  21  of the R/W  20 , mutual coupling between the antennas  11  and  21  is weakened due to the difference between a size (the antenna aperture area) of the antenna  11  of the IC card  10  and a size of the antenna  21  of the R/W  20 , or overlapping of the antenna  11  of the IC card  10  to the metal casing  23 , resulting in a positional relation between the IC card  10  and the R/W  20 , in which non-contact communication is not possible between the IC card  10  and the R/W  20 . 
     Here, the positional relation between the IC card  10  and the R/W  20  in which the non-contact communication is not possible between the IC card  10  and the R/W  20 , that is, the position of the IC card  10  with respect to the R/W  20 , is also called a communication dead zone. 
     In addition, the R/W  20 , which is an on-top device, is drawn with an indication mark serving as an indication of a position when the IC card  10  is placed thereon, and when a predetermined position of the IC card  10  is matched with the position (an indication mark position: a reference position) of the indication mark and then the IC card  10  is placed on the R/W  20 , the position of the IC card  10  with respect to the R/W  20  is an ideal position. 
     Hereinafter, the amount of position shift (offset) of the IC card  10  from the ideal position of the IC card  10  will be also referred to as an offset amount, and the offset amount is expressed by an xy coordinate of a two-dimensional coordinate system employing the indication mark position of the R/W  20  as the origin. 
       FIG. 3  is a diagram describing the offset amount. 
     The indication mark position of the R/W  20  is a reference position of the R/W  20  determined in advance as a position with which the predetermined position of the IC card  10  is to be matched, when the IC card  10  is allowed to face the R/W  20 . 
     Here, if the center of a coil aperture, from which magnetic flux occurs in the antenna (the coil), is defined as an antenna center, the antenna center of the antenna  11  of the IC card  10 , for example, is employed as the predetermined position of the IC card  10  to be matched with the indication mark position of the R/W  20 , and the antenna center of the antenna  21  of the R/W  20 , for example, is employed as the indication mark position (the reference position) of the R/W  20 . 
     In the following description, as illustrated in  FIG. 3 , a two-dimensional coordinate system is defined, in which the indication mark position is employed as the origin, a horizontal axis denotes an x axis, and a vertical axis denotes a y axis. 
     In this case, the offset amount is expressed by a coordinate (x, y) on the two-dimensional coordinate system of the antenna center as the predetermined position of the IC card  10  when the IC card  10  is placed on the R/W  20  which is the on-top device. 
     In addition, in the present embodiment, for the purpose of convenience, the IC card  10  is assumed to be placed on the R/W  20  such that a transverse direction of the IC card  10  is parallel to the x axis on the two-dimensional coordinate system of the R/W  20  and a longitudinal direction of the IC card  10  is parallel to the y axis on the two-dimensional coordinate system of the R/W  20 , and when the IC card  10  has rotated about an axis vertical to the two-dimensional coordinate system of the R/W  20 , the IC card  10  is assumed not to be placed on the R/W  20 . 
     Furthermore, in the present embodiment, a unit of coordinates x and y as the offset amount (x, y) is assumed to be mm (millimeter). 
       FIG. 4  is a diagram illustrating a correct communication rate of the IC card  10  with respect to each offset amount (x, y) when a resonance frequency fo of the IC card  10  has been set as each frequency. 
     In  FIG. 4 , the correct communication rate represents a rate by which data exchange has succeeded between the IC card  10  and the R/W  20 . 
     In addition, the resonance frequency fo of the IC card  10 , for example, can be set as various frequencies by adjusting the capacitance of the capacitor (not illustrated) connected to the antenna  21  of the IC card  10 . 
     In  FIG. 4 , five types of offset amounts (offset positions) (5,0), (0, 0), (−5,0), (0,5), and (0,−5) are employed as the offset amount (x, y), and eight types of frequencies in the range of 13.6 MHz to 14.4 MHz at intervals of 0.1 MHz are employed as the resonance frequency fo. 
     Referring to  FIG. 4 , if the resonance frequency fo of the IC card  10  is equal to or more than 13.9 MHz, since it is possible to check the occurrence of a communication dead zone (a correct communication rate smaller than 100%) using three of the five types of offset amounts, it cannot be said that the offset characteristics are good. 
     For example, as illustrated  FIG. 2 , when the size (in  FIG. 2 , the size of the aperture of one coil serving as the antenna  11 ) of the antenna  11  of the IC card  10  is larger than the size of the antenna  21  of the R/W  20 , if the communication distance of the IC card  10  is sufficient, the antenna aperture area of the IC card  10  is allowed to be reduced, so that it is possible to improve the offset characteristics. 
     However, if the antenna aperture area of the IC card  10  is allowed to be reduced, although the offset characteristics are improved, a communication distance is reduced (shortened). 
     Since the offset characteristics of the IC card  10  are improved by reducing the antenna aperture area of the IC card  10  and the communication distance of the IC card  10  is improved by increasing the antenna aperture area of the IC card  10 , that is, since the offset characteristics and the communication distance of the IC card  10  are in a trade-off relation, it is difficult to improve both the offset characteristics and the communication distance of the IC card  10  only by adjusting the antenna aperture area of the IC card  10 . 
     Furthermore, the communication dead zone may occur due to unnecessary radiation noise of the R/W  20  as well as the position shift (offset) of the IC card  10 . 
     The communication dead zone due to the unnecessary radiation noise is likely to be mitigated by adjusting the shape, the size (the antenna aperture area), the arrangement (position), the inductance and the like of the coil serving as the antenna  11  of the IC card  10 . However, through such adjustment, it is difficult to improve all of the communication distance, the offset characteristics, and tolerance (robustness such that non-contact communication can be performed in spite of the unnecessary radiation noise) of the unnecessary radiation noise (the communication dead zone due to the unnecessary radiation noise). 
       FIG. 5  is a diagram illustrating the presence or absence of the communication dead zone, which indicates whether the communication dead zone occurs in the IC cards  10  having various antenna aperture areas. 
     In addition, in  FIG. 5 , the resonance frequencies fo of the IC cards  10  are set to 14.3 MHz, and five types of antenna aperture areas 39, 36, 34, 30, and 26 mm 2  are employed as the antenna aperture area. 
     Moreover, in  FIG. 5 , as an R/W for performing non-contact communication with the IC cards  10 , an R/W (hereinafter, also referred to as an unnecessary radiation device) causing the unnecessary radiation noise of a predetermined level or more has been employed, in addition to the R/W  20  serving as the on-top device. 
     In addition, there is no unnecessary radiation noise of the on-top device, or the unnecessary radiation noise is at a negligible level. 
     Furthermore,  FIG. 5  also illustrates communication distances when the IC cards  10  perform non-contact communication with the R/W, which is a strong electric field device, in addition to the presence or absence of the communication dead zone. 
     In  FIG. 5 , all of the IC cards  10  having the antenna aperture areas 39, 36, 34, 30, and 26 mm 2  ensure a communication distance of 100 mm or more with respect to the strong electric field device. 
     Here, in the non-contact communication between the IC cards  10  and the unnecessary radiation device, the presence or absence of the communication dead zone has been examined by employing five types of offset amounts (0, 0), (10,0), (−10,0), (0,10), and (0,−10). 
     Furthermore, in the non-contact communication between the IC cards  10  and the on-top device, the presence or absence of the communication dead zone has been examined by employing five types of offset amounts (0, 0), (5,0), (−5,0), (0,5), and (0,−5). 
     Moreover, the communication distance between the IC cards  10  and the strong electric field device has been measured by employing an offset amount (0, 0). 
     In  FIG. 5 , “Present” indicates the occurrence of the communication dead zone and “Absent” indicates the non-occurrence of the communication dead zone. 
     Referring to  FIG. 5 , the antenna aperture areas of the IC cards  10  are allowed to be reduced in the range in which it is possible to ensure 100 mm or more as the communication distance to the strong electric field device, thereby preventing the occurrence of the communication dead zone due to the offset in the non-contact communication with the on-top device, that is, the offset characteristics are improved. However, in the non-contact communication with the unnecessary radiation device, it can be understood that the communication dead zone due to the unnecessary radiation noise occurs. 
     As described above, the antenna aperture areas of the IC cards  10  are allowed to be reduced, so that the communication distance is shortened to a certain degree and the offset characteristics are improved. However, it is difficult to prevent the occurrence of the communication dead zone due to the unnecessary radiation noise, that is, to improve tolerance against the unnecessary radiation noise. 
     In addition, the antenna  11  of the IC card  10  of  FIG. 2  is a coil having an antenna aperture area of 39 mm 2  in the record of the first row (from the top) of  FIG. 5 , and the correct communication rate of  FIG. 4  is a value measured by using the coil having the antenna aperture area of 39 mm 2  as the antenna  11  of the IC card  10 . 
     As described above, in the IC card  10  employing one coil as the antenna  11 , it is difficult to improve both the offset characteristics and the tolerance of the unnecessary radiation noise while maintaining the communication distance. 
     In light of the foregoing, the present technology proposes a non-contact communication device as a target capable of easily improving both the offset characteristics and the tolerance of the unnecessary radiation noise while maintaining the communication distance. 
     [One Embodiment of Communication System Employing Present Technology] 
       FIG. 6  is a diagram illustrating a configuration example of an embodiment of a communication system (a system includes a plurality of devices logically aggregated, and whether the devices having the configurations are in the same casing is not relevant) employing the present technology. 
     In  FIG. 6 , the communication system includes non-contact communication devices  111  and  112  configured to perform non-contact communication with each other. 
     In addition, in the embodiment of  FIG. 6 , for the purpose of convenience, the non-contact communication device  111  only serves as an initiator configured to output an RF signal, and modulates the RF signal to transmit the data, and the non-contact communication device  112  only serves as a target configured to load-modulate the RF signal output from the initiator and transmit data. 
     The non-contact communication device  111  serving as the initiator, for example, is an R/W, and the non-contact communication device  112  serving as the target, for example, is an IC card. 
       FIG. 7  is a block diagram illustrating an electrical configuration example of the non-contact communication device  111  serving as the R/W of  FIG. 6 . 
     An antenna  121  includes a coil and the like, and outputs an RF signal using a change in current flowing through the coil. Furthermore, magnetic flux passing through the coil serving as the antenna  121  is changed, so that current flows through the antenna  121 . 
     A reception unit  122  is configured to receive the current flowing through the antenna  121  and outputs the current to a demodulation unit  123 . The demodulation unit  123  demodulates a signal supplied from the reception unit  122  (for example, performs Amplitude Shift Keying (ASK) demodulation), and supplies a decoding unit  124  with a demodulated signal obtained by demodulating the above signal. The decoding unit  124  decodes the demodulated signal supplied from the demodulation unit  123 , for example, a Manchester code and the like, and supplies a data processing unit  125  with data obtained by decoding the demodulated signal. 
     The data processing unit  125  performs a predetermined process based on the data supplied from the decoding unit  124 . Furthermore, the data processing unit  125  supplies an encoding unit  126  with data to be transmitted to other devices such as the non-contact communication device  112 . 
     The encoding unit  126  encodes the data, which is supplied from the data processing unit  125 , into, for example, a Manchester code and the like, and outputs the Manchester code to a modulation unit  128 . 
     An RF signal output unit  127  allows current to flow through the antenna  121 , wherein the current is used to radiate a carrier (an RF signal) with a predetermined single frequency f c  from the antenna  121 . The modulation unit  128  adjusts the carrier as the current, which flows through the antenna  121  by the RF signal output unit  127 , according to the signal supplied from the encoding unit  126 . In this way, an RF signal, which is obtained by modulating the carrier according to the data (the Manchester code obtained by encoding the data) output from the data processing unit  125  to the encoding unit  126 , is radiated from the antenna  121  as a modulation signal. 
     Here, as a modulation scheme of the modulation unit  128 , for example, Amplitude Shift Keying (ASK) can be employed. However, the modulation scheme of the modulation unit  128  is not limited to ASK. For example, it is possible to employ Phase Shift Keying (PSK), Quadrature Amplitude Modulation (QAM), and the like. Furthermore, a modulation degree of amplitude is also not limited to a numerical value such as 8%, 30%, 50%, or 100%. For example, appropriate values can be selected. 
     A control unit  129  performs control and the like with respect to the blocks constituting the non-contact communication device  111 . That is, the control unit  129 , for example, includes a central processing unit (CPU)  129 A, an electrically erasable programmable read only memory (EEPROM)  129 B, a random access memory (RAM, not illustrated), and the like. The CPU  129 A executes a program stored in the EEPROM  129 B, thereby controlling the blocks constituting the non-contact communication device  111  and performing various processes. The EEPROM  129 B stores the program to be executed by the CPU  129 A, or data necessary for the operation of the CPU  129 A. 
     In addition, a series of processes performed by the program executed by the CPU  129 A can be performed by dedicated software provided instead of the CPU  129 A. Furthermore, the program executed by the CPU  129 A can not only be installed in the EEPROM  129 B in advance, but can also be temporarily or permanently stored (recorded) on a flexible disk, a compact disc read only memory (CD-ROM), a magneto optical (MO) disc, a digital versatile disc (DVD), a magnetic disk, or a removable recording medium such as a semiconductor memory, so that the program can be provided as so-called packaged software. Moreover, the program can be transmitted to the non-contact communication device  111  through proximity communication, and can be installed in the EEPROM  129 B. 
     A power supply  130  supplies desired power to the blocks constituting the non-contact communication device  111 . 
     In addition,  FIG. 7  does not illustrate a line along which the control unit  129  controls the blocks constituting the non-contact communication device  111 , or a line along which the power supply  130  supplies the power to the blocks constituting the non-contact communication device  111 , in order to avoid the complication of the diagram. 
     Furthermore, in the aforementioned case, the decoding unit  124  and the encoding unit  126  process the Manchester code. However, the decoding unit  124  and the encoding unit  126 , for example, can select and process one from a plurality of types of codes such as modified Miller codes or non-return to zero (NRZ) codes, as well as the Manchester code. 
     In the non-contact communication device  111  configured as above, the control unit  129  serve as the R/W, which is an initiator, by controlling each block of the non-contact communication device  111 . 
     That is, in the non-contact communication device  111  (hereinafter, also referred to as the R/W  111 ) serving as an R/W, when data (a frame) is transmitted, the RF signal output unit  127  allows the current to flow through the antenna  121 , the current being used to radiate the carrier with the predetermined single frequency f c  from the antenna  121 , so that the RF signal is radiated from the antenna  121  as the carrier (a non-modulated wave). 
     Furthermore, in the R/W  111 , the data processing unit  125  supplies the encoding unit  126  with data to be transmitted to the target, and the encoding unit  126  encodes the data supplied from the data processing unit  125  into the Manchester code and outputs the Manchester code to the modulation unit  128 . The modulation unit  128  modulates the carrier as the current, which flows through the antenna  121  by the RF signal output unit  127 , according to the signal supplied from the encoding unit  126 . In this way, the RF signal, which is obtained by modulating the carrier according to the data output from the data processing unit  125  to the encoding unit  126 , is radiated from the antenna  121 , so that data is transmitted to the target. 
     Meanwhile, in the R/W  111 , when data (a frame) transmitted from the target through load modulation is received, the reception unit  122  outputs a signal, which corresponds to the current on the antenna  121  and is changed by the load modulation of the target, to the demodulation unit  123 . The demodulation unit  123  demodulates the signal supplied from the reception unit  122 , and supplies the demodulated signal to the decoding unit  124 . The decoding unit  124  decodes the Manchester code and the like as the signal supplied from the demodulation unit  123 , and supplies the data processing unit  125  with the data obtained by decoding the signal. The data processing unit  125  performs a predetermined process based on the data supplied from the decoding unit  124 . 
       FIG. 8  is a block diagram illustrating an electrical configuration example of the non-contact communication device  112  serving as the IC card of  FIG. 6 . 
     An antenna  141  includes a coil and the like, and outputs an RF signal using a change in current flowing through the coil. Furthermore, magnetic flux passing through the coil which is the antenna  141  is changed, so that current flows through the antenna  141 . 
     A reception unit  142  is configured to receive the current flowing through the antenna  141  and outputs the current to a demodulation unit  143 . The demodulation unit  143  performs ASK demodulation with respect to a signal supplied from the reception unit  142 , and supplies a decoding unit  144  with a demodulated signal. The decoding unit  144  decodes the demodulated signal supplied from the demodulation unit  143 , for example, a Manchester code and the like, and supplies a data processing unit  145  with data obtained by decoding the demodulated signal. 
     The data processing unit  145  performs a predetermined process based on the data supplied from the decoding unit  144 . Furthermore, the data processing unit  145  supplies an encoding unit  146  with data to be transmitted to other devices such as the non-contact communication device  111 . 
     The encoding unit  146  encodes the data, which is supplied from the data processing unit  145 , into, for example, a Manchester code and the like, and outputs the Manchester code to a load modulation unit  147 . 
     The load modulation unit  147  changes the impedance of the coil serving as the antenna  141  when viewed from an exterior according to the signal supplied from the encoding unit  146 . When an RF field (a magnetic field) is formed around the antenna  141  by an RF signal output from other devices as a carrier, the impedance of the coil serving as the antenna  141  is changed, so that the RF field around the antenna  141  is also changed. In this way, the carrier as the RF signal output from other devices is modulated (load-modulated) according to the signal supplied from the encoding unit  146 , and the data output from the data processing unit  145  to the encoding unit  146  is transmitted to other devices which output the RF signal. 
     Here, as a modulation scheme of the load modulation unit  147 , for example, Amplitude Shift Keying (ASK) can be employed. However, the modulation scheme of the load modulation unit  147  is not limited to ASK. For example, it is possible to employ PSK, QAM, and the like. Furthermore, a modulation degree of amplitude is also not limited to a numerical value such as 8%, 30%, 50%, or 100%. For example, appropriate values can be selected. 
     A power supply  148  obtains power from the current flowing through the antenna  141  by the RF field formed around the antenna  141 , and supplies the power to the blocks constituting the non-contact communication device  112 . 
     A control unit  149  performs control and the like with respect to the blocks constituting the non-contact communication device  112 . That is, the control unit  149 , for example, includes a CPU  149 A, an EEPROM  149 B, a RAM (not illustrated), and the like. The CPU  149 A executes a program stored in the EEPROM  149 B, thereby controlling the blocks constituting the non-contact communication device  112  and performing various processes. The EEPROM  149 B stores the program to be executed by the CPU  149 A, or data necessary for the operation of the CPU  149 A. 
     In addition, a series of processes performed by the program executed by the CPU  149 A can be performed by dedicated software provided instead of the CPU  149 A. Furthermore, the program executed by the CPU  149 A can not only be installed in the EEPROM  149 B in advance, but can also be temporarily or permanently stored (recorded) in a flexible disk, a CD-ROM, an MO disc, a DVD, a magnetic disk, or a removable recording medium such as a semiconductor memory, so that the program can be provided as so-called packaged software. Moreover, the program can be transmitted to the non-contact communication device  112  through proximity communication, and can be installed in the EEPROM  149 B. 
     In addition,  FIG. 8  does not illustrate a line along which the control unit  149  controls the blocks constituting the non-contact communication device  112 , or a line along which the power supply  148  supplies the power to the blocks constituting the non-contact communication device  112  in order to avoid the complication of the diagram. 
     Furthermore, in  FIG. 8 , the power supply  148  obtains the power from the current flowing through the antenna  141 . However, for example, a battery is embedded in the non-contact communication device  112 , so that power can be supplied from the battery to the blocks constituting the non-contact communication device  112 . 
     Furthermore, in the aforementioned case, the decoding unit  144  and the encoding unit  146  process the Manchester code. However, the decoding unit  144  and the encoding unit  146 , for example, can select and process one from a plurality of types of codes such as modified Miller codes or NRZ codes, as well as the Manchester code. 
     In the non-contact communication device  112  configured as above, the control unit  149  serve as the target by controlling each block of the non-contact communication device  112 . 
     That is, in the non-contact communication device  112  (hereinafter, also referred to as the IC card  112 ) serving as an IC card, when data (a frame) is transmitted, the data processing unit  145  supplies the encoding unit  146  with data to be transmitted to the initiator, and the encoding unit  146  encodes the data, which is supplied from the data processing unit  145 , into the Manchester code and outputs the Manchester code to the load modulation unit  147 . The load modulation unit  147  changes the impedance of the coil serving as the antenna  141  when viewed from an exterior according to the signal supplied from the encoding unit  146 . 
     At this time, if the IC card  112  is adjacent to the R/W  111  and the RF field is formed around the antenna  141  by the RF signal output from the R/W  111  as the carrier, the impedance of the coil serving as the antenna  141  is changed, so that the RF field around the antenna  141  is also changed. In this way, the RF signal output from the R/W  111  is modulated (load-modulated) according to the signal supplied from the encoding unit  146 , and the data output from the data processing unit  145  to the encoding unit  146  is transmitted to the R/W  111  which outputs the RF signal. 
     Meanwhile, in the IC card  112 , when data (a frame), which is transmitted after the RF signal output from the R/W  111  as the carrier is modulated, is received, the reception unit  142  outputs a signal, which corresponds to the current flowing through the antenna  141  according to the RF signal modulated by the data, to the demodulation unit  143 . The demodulation unit  143  demodulates the signal supplied from the reception unit  142 , and supplies the demodulated signal to the decoding unit  144 . The decoding unit  144  decodes the Manchester code and the like as the signal supplied from the demodulation unit  143 , and supplies the data processing unit  145  with the data obtained by decoding the signal. The data processing unit  145  performs a predetermined process based on the data supplied from the decoding unit  144 . 
     [Physical Configuration Example of IC Card] 
       FIG. 9  is a plan view illustrating a physical configuration example of the non-contact communication device  112  serving as the IC card of  FIG. 6 . 
     In  FIG. 9 , parts corresponding to the IC card  10  of  FIG. 2  are denoted with the same reference numerals, and a description thereof will be appropriately omitted. 
     In  FIG. 9 , the IC card  112  has an approximately rectangular card shape, and has an IC chip  12  and an antenna  141  therein. 
     Thus, the IC card  112  is similar to the IC card  10  of  FIG. 2  in that the IC card  112  has the IC chip  12  therein, but is different from the IC card  10  of  FIG. 2  in that the IC card  112  has the antenna  141 , instead of the antenna  11 . 
     In addition,  FIG. 9  illustrates the IC chip  12  and the antenna  141  to be seen. However, the IC chip  12  and the antenna  141  are actually not seen because they are embedded in the IC card  112 . 
     Furthermore, in  FIG. 9 , the IC chip  12  corresponds to the reception unit  142  or the control unit  149  of  FIG. 8 . 
     The antenna  141  has a plurality of coils, for example, three coils  200 ,  201 U, and  201 D. 
     As the coil  200 , a coil (a standard coil) having an aperture with a predetermined size slightly smaller than that of the IC card  112  is employed. As the coils  201 U and  201 D, a coil (a small coil) having a size smaller than that of the coil  200  is employed. 
     The coils  200 ,  201 U, and  201 D are electrically connected in series to one another, or are connected in parallel to one another. 
     When the total inductance required in the antenna  141  is expressed by L and the inductances of the coils  200 ,  201 U, and  201 D are expressed by L 200 , L 200U , and L 200D , if the coils  200 ,  201 U, and  201 D are connected in series to one another, the inductances L 200 , L 200U , and L 200D  are determined such that L=L 200 +L 200U +L 200D  is satisfied. 
     Furthermore, when the coils  200 ,  201 U, and  201 D are connected in parallel to one another, the inductances L 200 , L 200U , and L 200D  are determined such that 1/L 1/L 200 +1/L 200U +1/L 200D  is satisfied. 
     In addition, in the case of manufacturing the IC card  112  by forming the coils  200 ,  201 U, and  201 D on a flexible substrate and the like as the antenna  141 , serial connection among the coils  200 ,  201 U, and  201 D facilitates the manufacturing of the IC card  112  as compared with parallel connection among the coils  200 ,  201 U, and  201 D. 
     The coil  200  (the standard coil) has an aperture with a size slightly smaller than that of the IC card  112 , and a winding part arranged slightly inside of the edge of the IC card  112 . 
     Meanwhile, for example, an R/W such as the R/W  20  (an on-top device,  FIG. 2 ), an unnecessary radiation device, or a strong electric field device is assumed as the R/W  111  ( FIG. 6 ) performing non-contact communication with the IC card  112 , and the coils  201 U and  201 D (small coils) are arranged such that a positional relation with a coil serving as an antenna of the assumed R/W (hereinafter, also referred to as assumption R/W) is a predetermined positional relation. 
     That is, the coils  201 U and  201 D are arranged such that the apertures of the coils  201 U and  201 D overlap a winding part of a coil serving as an antenna of the assumption R/W when the IC card  112  is allowed to face the assumption R/W by matching an antenna center (corresponding to the center of gravity of the apertures of the coils  200 ,  201 U, and  201 D in which magnetic flux is generated in the antenna  141 ) of the IC card  112  with an indication mark position which is a reference position of the assumption R/W that is determined in advance as a position with which the antenna center is to be matched as a predetermined position of the IC card  112 , for example. 
     In  FIG. 9 , the coils  201 U and  201 D (small coils) are arranged in a row in the longitudinal direction such that the IC card  112  is divided into two equal parts in the transverse direction. 
       FIG. 10  is a plan view illustrating a state in which the IC card  112  is placed on the R/W  20  which is an on-top device. 
     In  FIG. 10 , the IC card  112  is placed on the R/W  20  which is a kind of the assumption R/W, similarly to the case of  FIG. 2 . 
     In addition,  FIG. 10  illustrates the IC chip  12  and the antenna  141  to be seen. However, the IC chip  12  and the antenna  141  are actually not seen because they are embedded in the IC card  112 . 
     Furthermore,  FIG. 10  illustrates an antenna  21  (of an R/W module) of the R/W  20  if it were to be seen. However, the antenna  21  is actually not seen because it is embedded in a resin casing  22 . 
     In  FIG. 10 , the coil  200  serving as the antenna  141  of the IC card  112  overlaps a metal casing  23 , similarly to the case of  FIG. 2 . However, the other coils  201 U and  201 D serving as the antenna  141  overlap only the resin casing  22  without overlapping the metal casing  23 . 
     Therefore, in the IC card  112 , the influence of the metal casing  23  with respect to the whole of the antenna  141  is reduced. As a consequence, the antenna  141  overlaps the metal casing  23  and mutual coupling between the antenna  21  of the R/W  20  and the antenna  141  of the IC card  112  is weakened, so that it is possible to prevent non-contact communication from not being performed between the R/W  20  and the IC card  112 , resulting in the achievement of stable non-contact communication. 
     Furthermore, even when there is offset of a certain offset amount (other than (0, 0), for example, an offset amount in the range in which either of an x coordinate and a y coordinate is about −10 mm to +10 mm), since at least one of the coils  201 U and  201 D serving as the antenna  141  overlaps only the resin casing  22  without overlapping the metal casing  23 , it is possible to perform non-contact communication without the communication dead zone. 
     In addition, the configuration of the antenna  141  of the IC card  112  is not limited to the configurations illustrated in  FIG. 9  and  FIG. 10 . For example, a positional relation between small coils (the coils  201 U and  201 D in  FIG. 9  and  FIG. 10 ) of the antenna  141  and the coil serving as the antenna of the assumption R/W may be a predetermined positional relation described with reference to  FIG. 9  according to the configuration of the antenna of the assumption R/W. 
     That is, in  FIG. 10 , the antenna  21  (of an R/W module) of the R/W  20  as the assumption R/W includes one coil. However, the antenna  21  may be formed by arranging a plurality of coils on a plane. 
     Furthermore, in  FIG. 10  ( FIG. 9 ), the antenna  141  of the IC card  112  includes the three coils  200 ,  201 U, and  201 D, and the coils  201 U and  201 D (small coils) are arranged in a row in the longitudinal direction such that the IC card  112  is divided into two equal parts in the transverse direction. However, the number of coils constituting the antenna  141  or the arrangement of the small coils is not limited to the aforementioned number or arrangement. For example, the coils may be formed to satisfy the predetermined positional relation described with reference to  FIG. 9  according to the configuration of the antenna  21  of the R/W  20  serving as the assumption R/W. 
     In detail, as a first configuration example of a set of the antennas  21  and  141  for satisfying the predetermined positional relation, the configuration illustrated in  FIG. 10  can be employed. 
       FIG. 11  is a plan view illustrating a second configuration example of a set of the antennas  21  and  141  for satisfying the predetermined positional relation. 
       FIG. 11  illustrates a state in which the IC card  112  is placed on the R/W  20  which is the on-top device, similarly to the case of  FIG. 10 . 
     In  FIG. 11 , the antenna  21  of the R/W  20  includes two coils  301 L and  301 R arranged in a row in the transverse direction. 
     Furthermore, in  FIG. 11 , the antenna  141  of the IC card  112  includes three coils  200 ,  201 U, and  201 D, similarly to the cases of  FIG. 9  and  FIG. 10 . 
     Also in  FIG. 11 , similarly to the case of  FIG. 10 , the coils  201 U and  201 D are arranged such that the apertures of the coils  201 U and  201 D overlap a winding part of at least one of the coils  301 L and  301 R serving as the antenna  21  of the R/W  20  when the IC card  112  is allowed to face the R/W  20  by matching an antenna center of the IC card  112  with an indication mark position which is a reference position of the R/W  20  that is determined in advance as a position with which the antenna center of the IC card  112  is to be matched in allowing the IC card  112  to face the R/W  20  serving as the assumption R/W. 
     Furthermore, as described with reference to  FIG. 9 , the coils  201 U and  201 D, which are the small coils of the antenna  141  of the IC card  112 , are arranged in a row in the longitudinal direction such that the IC card  112  is divided into two equal parts in the transverse direction. However, even when there is offset of a predetermined offset amount (other than (0, 0)) in the IC card  112  placed on the R/W  20  (the on-top device) of  FIG. 11 , the coils  201 U and  201 D are arranged such that the aperture of the coil  201 U or  201 D overlaps the winding part of at least one of the coils  301 L and  301 R serving as the antenna  21  of the R/W  20 . 
     That is,  FIG. 11  illustrates the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), in addition to the IC card  112  placed on the R/W  20  in the state in which there is no offset (there is offset of an offset amount (0, 0)) (the antenna center of the IC card  112  has been matched with the indication mark position which is the reference position of the R/W  20 ), which is the same in  FIG. 12  and  FIG. 13  which will be described later. 
     Referring to  FIG. 11 , in all of the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), it can be understood that the aperture of the coil  201 U or  201 D overlaps the winding part of the coil  301 L or  301 R serving as the antenna  21  of the R/W  20 . 
     In addition,  FIG. 11  illustrates the IC chip  12  and the antenna  141  to be seen. However, the IC chip  12  and the antenna  141  are actually not seen because they are embedded in the IC card  112 . Moreover,  FIG. 11  illustrates the antenna  21  of the R/W  20  if it were to be seen. However, the antenna  21  is actually not seen because it is embedded in the R/W  20 . This is the same in  FIG. 12  and  FIG. 13  which will be described later. 
       FIG. 12  is a plan view illustrating a third configuration example of a set of the antennas  21  and  141  for satisfying the predetermined positional relation. 
       FIG. 12  illustrates a state in which the IC card  112  is placed on the R/W  20  which is the on-top device, similarly to the case of  FIG. 10 . 
     In  FIG. 12 , the antenna  21  of the R/W  20  includes one coil, similarly to the case of  FIG. 10 . 
     Furthermore, in  FIG. 12 , the antenna  141  of the IC card  112  includes five coils  200 ,  211 ,  212 ,  213 , and  214 . 
     The coil  200  has an aperture with a size slightly smaller than that of the IC card  112 , which is a standard coil having a predetermined size, and a winding part arranged slightly inside the edge of the IC card  112 , as described with reference to  FIG. 9 . 
     The coils  211  to  214  are coils (small coils) having sizes smaller that of the coil  200 , which is the standard coil, and are arranged inside (four corners of the aperture of the coil  200  having an approximately rectangular shape) at four corners of the IC card  112 , as compared with a winding part of the coil  200 . 
     In addition, the coils  200  and  211  to  214  are electrically connected in series to one another, or are connected in parallel to one another. 
     Also in  FIG. 12 , similarly to the case of  FIG. 10 , the coils  211  to  214  (small coils) are arranged such that the apertures of the coils  211  to  214  overlap a winding part of the coil serving as the antenna  21  of the R/W  20  when the IC card  112  is allowed to face the R/W  20  by matching an antenna center of the IC card  112  with an indication mark position which is a reference position of the R/W  20  with an offset amount set to (0, 0). 
     Furthermore, the coils  211  to  214 , which are the small coils of the antenna  141  of the IC card  112 , are arranged at the four corners of the IC card  112  as described above. However, even when there is offset of a predetermined offset amount (other than (0, 0)) in the IC card  112  placed on the R/W  20  (the on-top device) of  FIG. 12 , the coils  211  to  214  are arranged such that the apertures of the coil  211  to  214  overlap the winding part of the coil serving as the antenna  21  of the R/W  20 . 
     That is, similarly to the case of  FIG. 11 ,  FIG. 12  illustrates the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), in addition to the IC card  112  placed on the R/W  20  in the state in which there is no offset (there is offset of an offset amount (0, 0)). 
     Referring to  FIG. 12 , in all of the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), it can be understood that the apertures of the coils  211  to  214  overlap the winding part of the coil serving as the antenna  21  of the R/W  20 . 
       FIG. 13  is a plan view illustrating a fourth configuration example of a set of the antennas  21  and  141  for satisfying the predetermined positional relation. 
       FIG. 13  illustrates a state in which the IC card  112  is placed on the R/W  20  which is the on-top device, similarly to the case of  FIG. 10 . 
     In  FIG. 13 , the antenna  21  of the R/W  20  includes four coils  311 ,  312 ,  313 , and  314  arranged such that length×breadth is (2×2). 
     Furthermore, in  FIG. 13 , the antenna  141  of the IC card  112  includes two coils  200  and  221 . 
     The coil  200  has an aperture with a size slightly smaller than that of the IC card  112 , which is a standard coil having a predetermined size, and a winding part arranged slightly inside the edge of the IC card  112 , as described with reference to  FIG. 9 . 
     The coil  221  is a coil (a small coil) having a size smaller than that of the coil  200 , which is the standard coil, and is arranged at a position which is an antenna center of the IC card  112 . 
     In addition, the coils  200  and  221  are electrically connected in series to one another, or are connected in parallel to one another. 
     Also in  FIG. 13 , similarly to the case of  FIG. 10 , when an antenna center of the IC card  112  is matched with an indication mark position which is a reference position of the R/W  20  and the IC card  112  is allowed to face the R/W  20 , the coil  221  (the small coil) is arranged such that the aperture of the coil  221  overlaps a winding part of at least one of the coils  311  to  314  serving as the antenna  21  of the R/W  20 . 
     Furthermore, the coil  221 , which is the small coil of the antenna  141  of the IC card  112 , is arranged at the position which is the antenna center of the IC card  112  as described above. However, even when there is offset of a predetermined offset amount (other than (0, 0)) in the IC card  112  placed on the R/W  20  (the on-top device) of  FIG. 13 , the coil  221  is arranged such that the aperture of the coil  221  overlaps the winding part of at least one of the coils  311  to  314  serving as the antenna  21  of the R/W  20 . 
     That is, similarly to the case of  FIG. 11 ,  FIG. 13  illustrates the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), in addition to the IC card  112  placed on the R/W  20  in the state in which there is no offset (there is offset of an offset amount (0, 0)). 
     Referring to  FIG. 13 , in all of the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (−10, 0), the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, 10), and the IC card  112  placed on the R/W  20  in the state in which there is offset of an offset amount (0, −10), it can be understood that the aperture of the coil  221  overlaps the winding part of at least one of the coils  311  to  314  serving as the antenna  21  of the R/W  20 . 
     As described above, even when there is offset of a predetermined offset amount in the IC card  112  placed on the assumption R/W serving as the on-top device, in addition to the case in which there is no offset (there is offset of an offset amount (0, 0)), the small coil constituting the antenna  141  of the IC card  112  is arranged such that the aperture of the small coil overlaps the winding part of the coil serving as the antenna of the assumption R/W. Consequently, even when there is offset of a predetermined offset amount (other than (0, 0)) in the IC card  112  placed on the assumption R/W serving as the on-top device, mutual coupling when the IC card  112  is placed on the assumption R/W is weakened (furthermore, unnecessary radiation noise is reduced), so that it is possible to improve tolerance against the unnecessary radiation noise. 
       FIG. 14  is a diagram illustrating a relation between a distance from an IC card to an R/W (a coil serving as an antenna) and a coupling coefficient. 
     In  FIG. 14 , a rhombic mark indicates a coupling coefficient between the R/W  20  (hereinafter, also referred to as a 2-coil R/W  20 ) having the antenna  21  including the two coils  301 L and  301 R illustrated in  FIG. 11 , and the IC card  10  (hereinafter, also referred to as a 1-coil card  10 ) having the antenna  11  including one coil illustrated in  FIG. 2 . 
     Furthermore, in  FIG. 14 , a triangular mark indicates a coupling coefficient between the 2-coil R/W  20  illustrated in  FIG. 11  and the IC card  112  (hereinafter, also referred to as a 3-coil card  112 ) having the antenna  141  including the three coils  200 ,  201 U, and  201 D illustrated in  FIG. 11 . 
     In addition, in  FIG. 14 , an offset amount is (0, 0). Furthermore, the one coil serving as the antenna  11  of the 1-coil card  10  and the coil  200 , which is the standard coil of the 3-coil card  112 , have the same arrangement and size. 
     Referring to  FIG. 14 , when a distance to the 2-coil R/W  20  is long (for example, when the distance is 50 mm), it can be understood that coupling coefficients of the 1-coil card  10  and the 3-coil card  112  have the same value. 
     Consequently, it is possible for the 3-coil card  112  to maintain a communication distance similarly to the case of the 1-coil card  10 . 
     Furthermore, in  FIG. 14 , for example, when the distance to the 2-coil R/W  20  is short (for example, when the distance is 10 mm) similarly to the state in which the 1-coil card  10  or the 3-coil card  112  is placed on the 2-coil R/W  20 , it can be understood that the coupling coefficient of the 3-coil card  112  is smaller than the coupling coefficient of the 1-coil card  10 . 
     Consequently, in the state in which the 3-coil card  112  is placed on the R/W  20 , mutual coupling between the 3-coil card  112  and the R/W  20  is weakened as compared with mutual coupling between the R/W  20  and the 1-coil card  10 . Therefore, even when the R/W  20  causes unnecessary radiation noise, the influence of the unnecessary radiation noise to the 3-coil card  112  is small as compared with the influence of the unnecessary radiation noise to the 1-coil card  10 . 
     As described above, the coupling coefficient of the 3-coil card  112 , which has the coils  201 U and  201 D with sizes smaller than that of the coil  200  serving as the antenna  141  in addition to the coil  200  (equal to the coil serving as the antenna of the 1-coil card  10 ), is equal to that of the 1-coil card  10  at a position at which the distance to the 2-coil R/W  20  is long, and is smaller than that of the 1-coil card  10  at a position at which the distance to the 2-coil R/W  20  is short. 
     Consequently, according to the 3-coil card  112 , it is possible to reduce the influence of the unnecessary radiation noise from the 2-coil R/W  20  when the 3-coil card  112  has been placed on the 2-coil R/W  20  while maintaining a communication distance similarly to the case of the 1-coil card  10 . 
     In addition, in the 1-coil card  10  ( FIG. 2 ), when the aperture (the antenna aperture area) of one coil serving as the antenna  11  is allowed to be small, it is possible to reduce the influence of the unnecessary radiation noise. However, it is not possible to maintain the communication distance (the communication distance is shortened). 
       FIG. 15  is a diagram illustrating coupling coefficients of the 1-coil card  10  and the 3-coil card  112  having been offset by each offset amount at a position of 20 mm at which the distance to the 2-coil R/W  20  is relatively short. 
     In  FIG. 15 , regardless of the offset amounts, the coupling coefficients (parts with horizontal lines) of the 3-coil card  112  are smaller than the coupling coefficients (parts with inclined lines) of the 1-coil card  10 . 
     In  FIG. 15 , since there are five offset amounts (0, 0), (10, 0), (−10, 0), (0, 10), and (0, −10), when the distance to the 2-coil R/W  20  is short, it can be understood that it is possible to reduce the influence of the unnecessary radiation noise to the 3-coil card  112  regardless of the presence or absence of the offset amounts, as compared with the 1-coil card  10 . 
     In order to reduce the influence of the unnecessary radiation noise (to improve tolerance against the unnecessary radiation noise) when there is offset, it is effective to arrange a standard coil and a small coil serving as the antenna  141  of the IC card  112  at appropriate positions. 
       FIG. 16  is a diagram illustrating a correct communication rate for each offset amount (x, y) of the 3-coil card  112  when a resonant frequency fo of the 3-coil card  112  has been set as each frequency. 
     In  FIG. 16 , the correct communication rate represents a rate by which data exchange has succeeded between the 3-coil card  112  and the 2-coil R/W  20 . 
     In addition, the resonance frequency fo of the 3-coil card  112 , for example, can be set as various frequencies by adjusting the capacitance of the capacitor (not illustrated) connected to the antenna  141  of the 3-coil card  112 . 
     In  FIG. 16 , similarly to the case of  FIG. 4 , five types of offset amounts (offset positions) (5,0), (0, 0), (−5,0), (0,5), and (0,−5) are employed as the offset amount (x, y), and eight types of frequencies in the range of 13.6 MHz to 14.4 MHz at an interval of 0.1 MHz are employed as the resonance frequency fo. 
     As described with reference to  FIG. 4 , in the 1-coil card  10 , if the resonance frequency fo is equal to or more than 13.9 MHz, a communication dead zone occurs at three or more of the five types of offset amounts. However, as illustrated in  FIG. 16 , according to the 3-coil card  112 , no communication dead zone (parts with inclined lines) occurs, differently from the 1-coil card  10 . Consequently, it can be understood that the offset characteristics are improved. 
       FIG. 17  is a diagram illustrating the presence or absence of a communication dead zone, which indicates whether the communication dead zone occurs in the 3-coil card  112 . 
     In  FIG. 17 , since records of first to fifth rows (from the top) are equal to the records of first to fifth rows of  FIG. 5  (although  FIG. 5  does not illustrate the number of antenna coils indicating the number of coils constituting the antenna), the records indicate the presence or absence of the communication dead zone of the 1-coil card  10 . 
     Furthermore, in  FIG. 17 , a record of a sixth row (a record of the lowermost row) indicates the presence or absence of the communication dead zone of the 3-coil card  112 . 
     In addition, in  FIG. 17 , similarly to the case of  FIG. 5 , as an R/W which performs non-contact communication with the 3-coil card  112 , the R/W  20  (the 2-coil R/W  20 ) as the on-top device and the unnecessary radiation device have been employed. 
     Furthermore, similarly to the case of  FIG. 5 , in addition to the presence or absence of the communication dead zone,  FIG. 17  also illustrates a communication distance when the 3-coil card  112  performs the non-contact communication with the R/W which is the strong electric field device. 
     Referring to  FIG. 17 , 10 mm or more is ensured as the communication distance between the 3-coil card  112  and the strong electric field device, similarly to the communication distance between each of the IC cards  10  (the 1-coil card  10 ) having antenna aperture areas of 39 mm 2 , 36 mm 2 , 34 mm 2 , 30 mm 2 , and 26 mm 2  and the strong electric field device. 
     Here, in the non-contact communication between the 3-coil card  112  and the unnecessary radiation device, the presence or absence of the communication dead zone has been examined by employing the five types of offset amounts (0, 0), (10,0), (−10,0), (0,10), and (0,−10), similarly to the case of  FIG. 5 . 
     Furthermore, in the non-contact communication between the 3-coil card  112  and the on-top device, the presence or absence of the communication dead zone has been examined by employing the five types of offset amounts (0, 0), (5,0), (−5,0), (0,5), and (0,−5), similarly to the case of  FIG. 5 . 
     Moreover, the communication distance between the 3-coil card  112  and the strong electric field device has been measured by employing the offset amount (0, 0). 
     Furthermore, as the antenna aperture area (of the coil  200  which is the standard coil) of the antenna  141  of the 3-coil card  112 , 39 cm 2  has been employed, which is equal to the antenna aperture area of the IC card  10 , in which the communication dead zone has occurred, in the non-contact communication with the unnecessary radiation device or the on-top device. 
     In  FIG. 17 , “Present” indicates the occurrence of the communication dead zone and “Absent” indicates the non-occurrence of the communication dead zone. 
     Referring to  FIG. 17 , both in the non-contact communication between the 3-coil card  112  and the unnecessary radiation device and the non-contact communication between the 3-coil card  112  and the on-top device, it can be understood that no communication dead zone occurs regardless of offset, so that the offset characteristics and the tolerance against the unnecessary radiation noise are improved while the communication distance is being maintained. 
     Meanwhile, in  FIG. 11  to  FIG. 13 , the number and the arrangement of the small coils constituting the antenna  141  of the IC card  112  are adjusted, thereby preventing the communication dead zone from occurring (preventing the communication dead zone from occurring in the IC card  112 ). However, for example, if a line width (a line diameter) of a winding of the coil constituting the antenna  141 , or a resistance value of the winding is adjusted by a conductive metal used as the winding, it is possible to further effectively prevent the communication dead zone. 
       FIG. 18  is a diagram illustrating the presence or absence of the communication dead zone, which indicates whether the communication dead zone occurs in the 3-coil card  112  when the diameters of the coils  200 ,  201 U, and  201 D constituting the antenna  141  of the 3-coil card  112  have values illustrated in  FIG. 18 . 
     In addition, in order to check the presence or absence of the communication dead zone of  FIG. 18 , the 3-coil card  112 , in which an interval between the coils  201 U and  201 D (small coils) is shorter than an appropriate interval (an interval in which the communication dead zone is the least likely to occur in the non-contact communication with the 2-coil R/W  20 ), has been employed such that the communication dead zone easily occurs. 
     In addition, in  FIG. 18 , similarly to the case of  FIG. 5  or  FIG. 17 , as an R/W which performs non-contact communication with the 3-coil card  112 , the R/W  20  (the 2-coil R/W  20 ) as the on-top device and the unnecessary radiation device have been employed. 
     Moreover, in addition to the presence or absence of the communication dead zone,  FIG. 18  also illustrates a communication distance when the IC card  10  performs the non-contact communication with the R/W which is the strong 
     In  FIG. 18 , 10 mm or more is ensured as the communication distance between the 3-coil card  112  and the strong electric field device. 
     Furthermore, in the non-contact communication between the 3-coil card  112  and the unnecessary radiation device, the presence or absence of the communication dead zone has been examined by employing the five types of offset amounts (0, 0), (10,0), (−10,0), (0,10), and (0,−10). 
     Moreover, in the non-contact communication between the 3-coil card  112  and the on-top device, the presence or absence of the communication dead zone has been examined by employing the five types of offset amounts (0, 0), (5,0), (−5,0), (0,5), and (0,−5). 
     Furthermore, the communication distance between the 3-coil card  112  and the strong electric field device has been measured by employing the offset amount (0, 0). 
     In  FIG. 18 , “Present” indicates the occurrence of the communication dead zone and “Absent” indicates the non-occurrence of the communication dead zone. 
     Referring to  FIG. 18 , if the diameters of the coils  200 ,  201 U, and  201 D constituting the antenna  141  of the 3-coil card  112  are reduced to 0.0045 mm to increase resistance values thereof, it can be understood that it is possible to improve communication performance of the non-contact communication between the 3-coil card  112  and the unnecessary radiation device (to prevent the communication dead zone from occurring) while maintaining the communication distance to the strong electric field device, without deterioration of communication performance of the non-contact communication between the 3-coil card  112  and the on-top device (without the communication dead zone). 
     Consequently, the small coils (the coils  201 U,  201 D and the like) of the antenna  141  of the 3-coil card  112  are arranged at positions at which the communication dead zone does not easily occur (does not occur) in the non-contact communication with the assumption R/W, and the diameters and resistance values of the standard coil (the coil  200 ) as the antenna  141  and the small coils are adjusted, so that it is possible to improve all the communication distance, the offset characteristics, and the tolerance against the unnecessary radiation noise. 
     In addition, if the diameters of the coils  200 ,  201 U, and  201 D serving as the antenna  141  are reduced to excessively increase the resistance values thereof, since the communication distance is reduced, it is important to adjust the diameters of the coils  200 ,  201 U, and  201 D in a range in which it is possible to ensure the communication distance required for the 3-coil card  112 . 
     Furthermore, the resistance values of the coils  200 ,  201 U, and  201 D serving as the antenna  141  can also be adjusted by changing the conductive metal of the coils  200 ,  201 U, and  201 D, in addition to a change in the diameters thereof. For example, the conductive metal is changed from copper to aluminum, resulting in a reduction of the resistance values. 
     Here, when no tuning capacitor for adjusting a resonance frequency is provided and tuning is performed using only the coils  200 ,  201 U, and  201 D, the total inductance of the antenna  141  of the IC card  112  is approximately constant. However, in this case, in order to improve the communication performance of the IC card  112 , it is effective to adjust the balance of each inductance of the coils  200 ,  201 U, and  201 D. 
     In addition, since the plurality of coils  200 ,  201 U, and  201 D are electrically connected to one another and constitute the antenna  141  of the IC card  112 , the present technology is different from the technology disclosed in Patent Literature 1 in which a plurality of coils are not electrically connected to one another, and the technology disclosed in Patent Literature 2 in which one of two coils is an antenna of a card IC function unit and the other coil is an antenna of a reader/writer function unit. 
     Furthermore, the present technology is particularly useful when the size of the standard coil (for example, the coil  200  of the IC card  112 ) is equal to or more than the size (the antenna aperture area) of the coil serving as the antenna of the assumption R/W. As the small coils (for example, the coils  201 U and  201 D of the IC card  112 ), coils having sizes equal to or less than the size (when the antenna of the assumption R/W includes a plurality of coils as illustrated in  FIG. 11  or  FIG. 13 , the size of each coil constituting the antenna) of the coil serving as the antenna of the assumption R/W are employed. 
     In addition, the embodiment of the present technology is not limited to the above-mentioned embodiment. For example, various modifications may occur within the scope of the present technology. 
     That is, the present technology can also be applied to non-contact communication of a communication device which performs both non-contact communication and contact communication, in addition to non-contact communication of a communication device which performs only non-contact communication. 
     Additionally, the present technology may also be configured as below. 
     [1] A non-contact communication device comprising an antenna configured to transmit data through non-contact communication after load-modulation of an RF signal from a reader/writer (R/W), 
     wherein the antenna includes: 
     a standard coil having an aperture with a predetermined size; and 
     a small coil having an aperture with a size smaller than a size of the standard coil, 
     wherein the standard coil and the small coil are connected in series or in parallel, and 
     the small coil is arranged such that the aperture of the small coil overlaps a winding part of a coil that is an antenna of the R/W when the non-contact communication device is caused to face the R/W by matching a predetermined position of the non-contact communication device with a reference position of the R/W that is determined in advance as a position with which the predetermined position of the non-contact communication device is to be matched in causing the non-contact communication device to face the R/W. 
     [2] The non-contact communication device according to [1], wherein the standard coil has a size equal to or more than a size of the coil which is the antenna of the R/W, and the small coil has a size equal to or less than the size of the coil which is the antenna of the R/W. 
     [3] The non-contact communication device according to [1] or [2], wherein the standard coil and the small coil are connected in series. 
     [4] The non-contact communication device according to any one of [1] to [3], wherein the antenna includes a plurality of small coils. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.