Relaying apparatus and communication system

BACKGROUND OF THE INVENTION

Field of the Invention

0001This invention relates to an RFID (Radio Frequency IDentification) employing a non-contact information medium, such as a non-contact IC (Integrated Circuit) tag or a non-contact IC card. More particularly, it relates to a relaying apparatus and a communication system as known from <patcit id="pcit0001" dnum="EP1031939A1"><text>EP-A1-1 031 939</text></patcit> and from <patcit id="pcit0002" dnum="US5270717A"><text>US 5 270 717</text></patcit>.

0002The RFID system, as the communication system employing a non-contact information medium, such as a non-contact IC card or a non-contact IC tag, has been devised and put to practical use. The RFID system allows information communication to be performed between an IC chip enclosed in the non-contact information medium, and a reader/ writer, and is utilized in an automatic ticket checker in a railroad station or for book lending in a lending library. It is estimated that, in near future, the system will be used for exchanging the private information in a wide variety of fields.

0003The non-contact IC card is a generic term for a card-shaped non-contact information medium, such as a so-called credit card. On the other hand, the non-contact IC tag is a generic term for a non-contact information medium of a shape other than the card shape, a non-contact information medium of a label size smaller than the credit card size, such as a stamp size or a size smaller than the stamp size, or a non-contact information medium of a round or a star shape.

0004In the RFID system by the electro-magnetic coupling system, the non-contact information medium receives electrical waves, transmitted from the reader/ writer, to obtain the operating power from the received electrical waves by electro-magnetic induction, and effects data communication with the reader/ writer by exploiting the received electrical waves. The non-contact information medium and the reader/ writer each include an antenna coil for transmitting/ receiving the electrical waves. The optimum communication distance between the reader/ writer of the electro-magnetic coupling system and the non-contact information medium is usually several cm to tens of cm.

[Patent Publication 1] Japanese Laid-Open Patent Publication 2000-315908

0005For example, if the non-contact information medium is a non-contact IC card, the card size of the same size as the credit card size (54 mm in length, 85.6 mm in width and 0.76 mm in thickness), as provided for by the ISO (International Organization for Standardization), is generally used.

0006In such case, the antenna coil 100, enclosed in the non-contact IC card, is sized to approximately the size of the non-contact IC card, in order to permit the largest amount possible of the flux from the reader/ writer as possible to traverse the inside of the coil, as shown in <figref idref="f0010">Fig. 17A</figref>. If the non-contact information medium is a non-contact IC tag, the antenna coil is of such a shape as to permit the largest amount possible of the flux to traverse the inside of the coil, depending on the standard or the size of the non-contact IC tag.

0007In this manner, the shape of the antenna coil of the non-contact information medium is determined to a more or less extent by e.g. the relevant standard.

0008On the other hand, the shape of the antenna coil of the reader/writer is appreciably influenced by the structure of the equipment carrying the reader/writer thereon.

0009In case the inside space of a casing of the device carrying the reader/writer thereon is occupied by densely arranged component parts, there is not sufficient space available for properly mounting the reader/writer. In such case, the antenna coil area is decreased compared to the available space in the casing, or the reader/writer is mounted on the back side of the casing of the carrying device, in order to exploit the small space left in the casing.

0010In particular, if the reader/writer is mounted on the back side of the casing of the carrying device, an aperture must be formed in a portion of the casing in order to pass the magnetic flux emanating from the magnetic field generated by the antenna coil of the reader/ writer to the antenna coil of the non-contact information medium.

0011In general, the casing is provided for protecting the circuitry in the casing against impacts from outside, or for shielding the electro-magnetic noise, emanating from the electronic circuit in the casing and hence the processing such as perforating the casing is to be avoided as far as is possible. If the casing is to be perforated, out of necessity, the area of an aperture produced needs to be as small as possible.

0012Consequently, the antenna coil of the reader/writer is of an extremely small size as compared the size of the antenna coil enclosed in the non-contact information medium. For example, an antenna coil 200 of the reader/writer, shown in <figref idref="f0010">Fig. 17B</figref>, is of a size appreciably smaller than the size of the antenna coil 100 enclosed in the inside of the non-contact IC card shown in <figref idref="f0010">Fig. 17A</figref>.

0013If the size of the antenna coil on the reader/writer side is this small, the amount of the magnetic flux generated by the current flowing in the antenna coil is also extremely small, so that, if the non-contact information medium is moved to the vicinity of the antenna coil of the reader/ writer, the amount of the magnetic flux necessary to operate the non-contact information medium cannot be generated.

0014<figref idref="f0011">Fig.18</figref> shows the manner in which the magnetic flux by the magnetic field generated by the antenna coil 200 provided to the reader/writer traverses the inside of the antenna coil 100 enclosed within the non-contact IC card. As may be seen from <figref idref="f0011">Fig. 18</figref>, since it is the magnetic flux by the magnetic field at the center of the antenna coil 200 that traverses the inside of the antenna coil 100, the antenna coil 100 must be moved to a position closer to the antenna coil 200 in order to procure an appropriate amount of the magnetic flux.

0015<figref idref="f0011">Fig. 19</figref> shows a communication system 150, made up by a reader/ writer 201 having an antenna coil 200, mounted to the back side of the metal casing 205, and by a non-contact IC card 101, having an antenna coil 100.

0016The reader/writer 201 includes an antenna coil 200, as an inductor arranged on a substrate 204, a tuning capacitor 203, connected in series with the antenna coil 200, to form a parallel resonance circuit, and an IC for a reader/writer 202 for controlling the data transmission/ receipt with the non-contact IC card 101. A casing 205, having the reader/ writer 201 mounted thereon, is perforated at 205A in register with the antenna coil 200.

0017In a majority of cases, the casing 205 of the equipment, adapted for loading the reader/ writer 201 thereon, is formed of metal for procuring the strength or for preventing leakage to outside of the electro-magnetic noise caused by the internal electronic circuitry. However, if a substrate 204 is mounted to the metal casing 205, the magnetic flux of the magnetic filed, generated by the antenna coil 200, is lost in the casing 205, such that it is only the small amount of the magnetic flux generated at the center of the antenna coil 200 that is allowed to pass through the inside of the antenna coil of the non-contact IC card 101.

0018Thus, with the communication system 150, shown in <figref idref="f0011">Fig. 19</figref>, the non-contact IC card 101 and the reader/writer 201 cannot communicate with each other.

0019That is, a wide variety of constraints are imposed on the antenna coil of the reader/writer, by the structure of the equipment adapted for loading the reader/writer thereon, such that it is difficult to set the antenna coil shape or area in such a manner as to permit optimum communication with the non-contact information medium. There is also a problem that, given the limited space within the equipment adapted for loading the reader/ writer thereon, it is also extremely difficult to eliminate the adverse effect of the metal components interfering with the wireless communication.

0020For overcoming this deficiency, the antenna coil of the reader/ writer 201 is designed as an antenna coil 210 substantially coextensive as the antenna coil of the non-contact IC card, and is mounted on the back side of a resin cover 220, fitted to the casing 205, so as to operate as a relaying antenna, as shown in <figref idref="f0012">Fig.21</figref>. In this manner, it is possible to cope with the constraint of the antenna area or to eliminate the adverse effect from the metal casing 205.

0021The antenna coil 210 is connected to the substrate 204 by fitting a jack 212, mounted to the distal end of a lead wire 211, extending from the antenna coil 210, into a plug 213 provided to the substrate 202 exposed through the aperture 205A formed in the casing 205.

0022Consequently, the antenna coil 210 is inconvenient to mount or dismantle, especially for maintenance, such that, in the worst of cases, the lead wire 211 may be ruptured, or the reader/ writer 201 may be destroyed.

0023In the relaying apparatus and the communication system known from <patcit id="pcit0003" dnum="EP1031939A"><text>EP-A-1 031 939</text></patcit> cited above, the first antennae coil and a second coupler coil as well as the capacitor forming a resonance circuit of the relaying apparatus are arranged altogether on an IC module forming an IC card together with a first coupler coil which is connected directly to an IC chip of the IC card. Further, the first coupler coil and the second coupler coil are transformer coupled and the antennae coil is proposed to have a large area that is this document does not disclose any relation of the size and shape of the antennae coil and a transmission/reception coil of an external read/write apparatus 100. Further, the common arrangement of the relaying apparatus together with the first coupling coil and the IC on the same substrate in the known communication system may enhance the electric power consumption within the IC card and enlarge the size thereof.

0024Also in non-contact electromagnetic energy transmission and detection systems (communication systems) known from <patcit id="pcit0004" dnum="JP2002175508A"><text>JP 2002-175508 A</text></patcit>, <patcit id="pcit0005" dnum="EP0812752A2"><text>EP-A2-0 812 752</text></patcit> and <patcit id="pcit0006" dnum="JP2003218624A"><text>JP 2003-218624 A</text></patcit> the relaying apparatus such as a booster coil and for example an IC providing the identification signal generator are placed together on the same substrate and therefore enhance the power consumption of the circuit tree on the IC card at increase the size of the latter. <patcit id="pcit0007" dnum="EP1385120A1"><text>EP-A1-1 385 120</text></patcit> being a prior art document according to Art. 54(3) EPC proposed to arrange a booster coil being a part of a resonance circuit of a relaying apparatus not on the IC card itself but in a fixed distance to the latter. This document proposes to use a very large booster coil and also does not disclose a relation of the size of the booster coil and the coil of the external information read/write device.

SUMMARY OF THE INVENTION

0025In view of the above-depicted status of the art, it is an object of the present invention to provide a communication system in which, in wireless communication by the electro-magnetic coupling system between an information read/ write device and a non-contact information medium, mediated by a carrier wave of a preset frequency, the adverse effect on the communication, brought about by the limitation as to the mounting site of the information read/write device, may be eliminated, and the use configuration of the information read/write device and a non-contact information medium may be flexibly coped with to achieve optimum communication.

0026The object is achieved by a communication system according to claim 1.

0027According to this communication system, the position of the third antennae coil of the third resonance circuit is fixedly mounted in a predetermined distance to the position of the first antennae coil of the first resonance circuit so that a magnetic flux generated by the magnetic field generated by the first antennae coil of the first resonance circuit always traverses the third antennae coil of the third resonance circuit.

0028The relaying device and the communication system of the present invention assure optimum wireless communication even in cases wherein the antenna coil of the information read/ write device has a shape and a size differing appreciably from those of the antenna coil of the non-contact information medium.

0029The wireless communication between the non-contact information medium and a wide variety of use configurations of the read/ write device may be optimized by a simple technique of changing the size/ shape of the first and second antenna coils of the relaying device so that the first and second antenna coils may be electro-magnetically coupled to the antenna coils of the information read/ write device and the non-contact information medium, respectively.

0030In case limitations are imposed on the space in which to mount the first antenna coil, it is sufficient that the third antenna coil is changed in shape/ size so as to be electrically coupled to the first antenna coil. In case limitations are imposed that the first antenna coil has to be mounted on a metal component, such as a casing, the size of the first antenna coil or the aperture formed in the casing may be of the smallest size possible to assure the strength of the casing as well as to avoid adverse effects by the metal components.

0031The relaying device of the communication system of the present invention performs wireless communication of the electromagnetic coupling system with the information read/ write device, no laborious processing, such as wiring, is needed, and is able to relay the wireless communication with the non-contact information medium by fitting the relaying device on a removable cover or to a door that may be opened/closed.

BRIEF DESCRIPTION OF THE DRAWINGS

0032<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig.1</figref> illustrates the configuration of a communication system showing an example.</li><li><figref idref="f0002">Fig.2</figref> illustrates the configuration of a matching tuning circuit of the communication system.</li><li><figref idref="f0003">Fig.3</figref> shows an embodiment of the invention.</li><li><figref idref="f0004">Fig.4</figref> illustrates the configuration of a matching tuning circuit of the communication system.</li><li><figref idref="f0004">Fig.5</figref> shows an induction current I flowing in a matching tuning circuit of the communication system.</li><li><figref idref="f0005">Fig.6</figref> shows another embodiment of the invention.</li><li><figref idref="f0005">Fig.7</figref> shows a matching tuning circuit provided with a parallel-connected antenna coil.</li><li><figref idref="f0006">Fig.8</figref> illustrates an experiment 1 carried out for verifying the effect of the matching tuning circuit.</li><li><figref idref="f0006">Fig.9</figref> illustrates a communication range XY in the experiment 1.</li><li><figref idref="f0007">Fig.10</figref> shows the results of an experiment on a communication range Z in the experiment 1.</li><li><figref idref="f0007">Fig.11</figref> shows the results of an experiment on the communication range XY in the experiment 1.</li><li><figref idref="f0008">Fig. 12</figref> illustrates an experiment 2 carried out for verifying the effect of the matching tuning circuit.</li><li><figref idref="f0008">Fig. 13</figref> illustrates an iron plate used in the experiment 2.</li><li><figref idref="f0009">Fig. 14</figref> shows the communication range XY in the experiment 2.</li><li><figref idref="f0009">Fig. 15</figref> shows the results of an experiment on the communication range Z in the experiment 2.</li><li><figref idref="f0010">Fig.16</figref> shows the results of an experiment on the communication range Z in the experiment 2.</li><li><figref idref="f0010">Fig. 17A</figref> shows an example of an antenna coil of a non-contact IC card and <figref idref="f0010">Fig.17B</figref> shows an example of an antenna coil for a reader/writer.</li><li><figref idref="f0011">Fig. 18</figref> shows the magnetic flux passed through the antenna coil of the non-contact IC card.</li><li><figref idref="f0011">Fig.19</figref> shows an example of concrete setup of a reader/writer of a communication system shown as a prior art.</li><li><figref idref="f0012">Fig.20</figref> shows the magnetic flux passed through an antenna coil of a non-contact IC card when an antenna coil of the reader/writer is mounted on a metal chassis.</li><li><figref idref="f0012">Fig.21</figref> shows an example of mounting the antenna coil of the reader/ writer of the communication system of the prior art as a relay antenna.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0033Referring now to the drawings, the best embodiments of a relay apparatus and a communication system of the present invention are explained in detail.

0034Referring first to <figref idref="f0001">Fig. 1</figref>, a communication system 1 is explained.

0035The communication system 1, shown in <figref idref="f0001">Fig.1</figref>, is an RFID (Radio Frequency Identification), by the electromagnetic coupling system, provided with a reader/writer 10, a non-contact IC card 20, and a matching tuning circuit 30.

0036In this communication system 1, the non-contact IC card 20, as a non-contact information medium, receives electrical waves, transmitted from the reader/writer 10 through the matching tuning circuit 30, to obtain the power by electromagnetic induction, and has data communication with the reader/writer 10, with use of the electrical waves, through the matching tuning circuit 30.

0037The reader/ writer 10 includes a parallel resonance circuit 13, comprised of a serial connection of an antenna coil 11, as an inductor, and a tuning capacitor 12. A reader/writer for IC 14 is connected in parallel with this parallel resonance circuit 13. The reader/writer 10 is tuned to a frequency fc in the vicinity of, for example, 13.56MHz, as the a.c. voltage is applied to the parallel resonance circuit 13, under control by the reader/writer for IC 14.

0038The reader/writer 10 has wireless communication with the non-contact IC card 20, using the electrical waves, which have modulated a carrier having this frequency fc as the carrier frequency. Although the carrier frequency is the frequency fc, in the following explanation, the carrier frequency fc is not limited to 13.56MHz.

0039The reader/writer for IC 14 is provided with an interfacing circuit, not shown, and is connected to and controlled by a CPU (central processing unit) of a counterpart device, having loaded thereon the reader/writer 10.

0040The reader/writer for IC 14 controls the operation in sending data from the reader/ writer 10 to the non-contact IC card 20 and in receiving data sent from the non-contact IC card 20.

0041In data transmission, the reader/writer for IC 14 modulates the carrier wave of the carrier frequency fc with data being transmitted to generate transmission signals. As the data modulating system, ASK (amplitude shift keying), PWM (pulse width modulation) or the PSK (phase shift keying), for example, may be used.

0042The transmission signals, generated on modulation, are sent to the antenna coil 11 to generate a magnetic field. The magnetic field, generated in the antenna coil 11, is changed in keeping with the transmission signals, such that data carried by the carrier wave with the carrier frequency fc is transmitted, as changes in the magnetic flux, to an antenna coil 31 of the matching tuning circuit 30, electro-magnetically coupled to the antenna coil 11.

0043In data receipt, the reader/writer for IC 14 demodulates the data, transmitted from the non-contact IC card 20 through the matching tuning circuit 30 and received as changes in the magnetic flux by the antenna coil 11. On receipt of the data by the antenna coil 11 from the non-contact IC card 20, the induced current is generated in the antenna coil 11 as a result of changes in the magnetic flux in the antenna coil 31 of the matching tuning circuit 30 electro-magnetically coupled with the antenna coil 11.

0044As the induced current, generated in the antenna coil 11, is changed with the magnetic flux, the data carried by the carrier wave with the carrier frequency fc is transmitted to the antenna coil 11 as changes in the induced current.

0045The reader/ writer for IC 14 demodulates this induced current to acquire data transmitted from the non-contact IC card 20.

0046The non-contact IC card 20 includes a parallel resonance circuit 23, which is a serial connection of an antenna coil 21, as an inductor, and a tuning capacitor 22. An IC for a card 24 is connected in parallel with this parallel resonance circuit 23.

0047The antenna coil 21 receives the electrical waves, transmitted from the reader/ writer 10 through the matching tuning circuit 30, as changes in the magnetic flux. In the parallel resonance circuit 23, there is generated the induced electromotive force operating in a direction of obstructing changes in the magnetic flux of the electrical waves received by the antenna coil 11. By this induced electromotive force, the parallel resonance circuit 23 is tuned in the vicinity of the frequency fc = 13.56 MHz.

0048The IC for a card 24, connected in parallel with the parallel resonance circuit 23, is operated with this induced electromotive force as the operating power. The IC for a card 24, supplied with the operating power, controls the operation in receiving data sent from the reader/writer 10 and in transmitting data to the reader/ writer 10.

0049In data receipt, the IC for a card 24 demodulates the electrical waves, transmitted from the reader/writer 10 through the matching tuning circuit 30 and received as changed in the magnetic flux in the antenna coil 21.

0050In data transmission, the IC for a card 24 modulates the carrier wave, with the carrier frequency fc, with data to be transmitted, to generate transmission signals. The IC for a card 24 changes the load of the antenna coil 21, responsive to data to be transmitted, to modulate the carrier wave, by way of load modulation.

0051The transmission signals, generated on modulation, are sent to the antenna coil 21 to generate a magnetic field. As the magnetic field, generated in the antenna coil 21, is changed with the transmission signals, the data carried by the carrier wave, with the carrier frequency fc, is transmitted, as changes in the magnetic flux, to an antenna coil 32 of the matching tuning circuit 30, electro-magnetically coupled with the antenna coil 21.

0052The matching tuning circuit 30 includes a parallel resonance circuit 34, comprised of a series connection of an antenna coil 31, as a first inductor, an antenna coil 32, as a second inductor, and a tuning capacitor 33.

0053Specifically, the matching tuning circuit 30 is comprised of the antenna coils 31, 32, arranged on a substrate 35, so as to be connected in series with the tuning capacitor 33.

0054The antenna coil 31 is electro-magnetically coupled, in a non-contact fashion, with the antenna coil 11, forming the parallel resonance circuit 13 in the reader/writer 10, and is shaped for communicating with the reader/writer 10.

0055The antenna coil 31 may be of any suitable shape, on the condition that it may communicate with the reader/ writer 10. For example, the antenna coil 31 may be of an elliptical or a square shape, to say nothing of the circular shape shown in <figref idref="f0001">Fig.1</figref>.

0056The antenna coil 31 does not have to be of the same shape as the antenna coil 11, on the condition that the antenna coil 31 is able to communicate with the reader/writer 10. However, in case the antenna coil 31 is approximately of the same shape and of the same size as the antenna coil 11, the electro-magnetic coupling may be stronger to achieve stable and highly efficient data communication.

0057On the other hand, the antenna coil 32 is electro-magnetically coupled, in a non-contact fashion, with the antenna coil 21 on the non-contact IC card 20, forming the parallel resonance circuit 23, such as to communicate with the non-contact IC card 20.

0058The antenna coil 32 may be of any suitable shape, on the condition that it may communicate with the reader/ writer 10. For example, the antenna coil 31 may be of an elliptical or a circular shape, to say nothing of the square shape shown in <figref idref="f0001">Fig.1</figref>.

0059The antenna coil 32 is desirably larger in size than the antenna coil 21, provided to the non-contact IC card 20, since then a sufficient amount of the magnetic flux can be passed through the antenna coil 21 even in case the center of the antenna coil 21 is offset from the center of the antenna coil 32.

0060For example, in case the non-contact information medium is a non-contact IC card, and is used as a commutation ticket for railway or bus, the non-contact IC card cannot be placed at a constant fixed position at all times with respect to the antenna coil 32 of the matching tuning circuit 30 for data communication. Thus, in such case, the antenna coil 32 is larger in size than the antenna coil of the non-contact IC card to assure more reliable data communication.

0061For example, if the non-contact information medium is a non-contact IC tag affixed to a toner cartridge of a printer, as a consumable commodity, and is to have data communication with the reader/writer 10 mounted to a preset inner chassis in a printer casing, in order to manage the residual toner quantity, the non-contact IC tag may be placed in a fixed position relative to the antenna coil 32 of the matching tuning circuit 30 for data communication. Thus, in such a case, more efficient data communication may be had with the antenna coil 32 sized to be approximately equal to the size of the antenna coil of the non-contact IC tag.

0062If the antenna coil 32 is slightly smaller in size than the antenna coil 21, communication may be had by adjusting the output of the reader/writer 10.

0063The antenna coil 32 does not have to be of the same size and shape as the antenna coil 21, on the condition that the antenna coil 32 is able to communicate with the non-contact IC card 20, as discussed above. However, if the antenna coil 32 is of the same size and shape as the antenna coil 21, the electro-magnetic coupling becomes stronger to realize more efficient stable data communication.

0064That is, the size as well as the shape of the antenna coils 31, 32 of the matching tuning circuit 30 is limited to a more or less extent by the shape of the antenna coil 11 of the reader/writer 10 and by the shape of the antenna coil 21 of the non-contact IC card 20, respectively, for the realization of the efficient stable wireless communication.

0065With the communication system 1, the non-contact IC card 20 is used as the non-contact information medium. Hence, in the following explanation, it is assumed that the shape and the size of the antenna coil 32 are approximately the same as those of the antenna coil 21 of the non-contact IC card 20, and also that the shape and the size of the antenna coil 31 are approximately the same as those of the antenna coil 11 of the reader/ writer 10.

0066Since the antenna coils 31, 32 are connected in series with each other so that these coils are wound in the same direction, the antenna coils 31, 32 may be deemed to be an inductor having a combined inductance L = L1 + L2, where L1 is the inductance of the antenna coil 31 and L2 is the inductance of the antenna coil 32. Consequently, the parallel resonance circuit 34 may be deemed to be a resonance circuit comprised of a series connection of an inductor having a combined inductance L and the tuning capacitor 33.

0067Referring to <figref idref="f0003">Fig.3</figref>, an embodiment of the reader/writer 10 and the matching tuning circuit 30 of the invention is shown and, based on this embodiment, the operating principle of the matching tuning circuit 30 is explained.

0068It is assumed that the reader/writer 10, provided on a substrate 15, is mounted on the back side of a metal chassis 50, as a casing of an apparatus on which to mount the reader/ writer 10. The metal chassis 50, on which the reader/writer 10 is mounted in this manner, has an aperture 50A in a location which is to be register with the mounting position of the antenna coil 11 of the reader/ writer 10.

0069The opening area of the aperture 50A is selected to be such that the strength of the metal chassis 50 is not impaired and such that there is no risk of leakage of the electromagnetic noise produced by e.g. an electronic circuit within the metal chassis 50. The shape and the size of the antenna coil 11 of the reader/writer 10 are selected so that the antenna coil will be housed within this aperture 50A.

0070Since the antenna coil 31 of the matching tuning circuit 30 is shaped so that the antenna coil 31 is electro-magnetically coupled with the antenna coil 11 in a non-contact fashion and so that the antenna coil 31 may communicate with the reader/ writer 10, the shape of the antenna coil 31 is determined to a more or less extent if once the shape of the antenna coil 11 is determined.

0071On the other hand, the matching tuning circuit 30 is mounted for facing the reader/ writer 10, mounted on the metal chassis 50, with the metal chassis 50 in-between. The matching tuning circuit 30 is mounted at this time so that the antenna coil 31 overlies the aperture 50A formed in the metal chassis 50. By so doing, the antenna coil 11 of the reader/writer 10 and the antenna coil 31 of the matching tuning circuit 30 may be electromagnetically coupled to each other in a non-contact fashion.

0072Since the reader/writer 10 mounted to the metal chassis 50 and the matching tuning circuit 30 may have wireless communication by the antenna coils 11,31 being electromagnetically coupled to each other in a non-contact fashion, no physical connection between the reader/writer 10 and the matching tuning circuit 30 is needed and hence the matching tuning circuit 30 may be mounted in position by a simplified technique of directly bonding the substrate 30 to the metal chassis 50 with e.g. a double-sided adhesive tape.

0073The matching tuning circuit 30, mounted to the metal chassis 50 operates as follows, by the electrical waves, transmitted from the reader/writer 10.

0074The antenna coil 31 of the parallel resonance circuit 34 of the matching tuning circuit 30 is traversed by a magnetic flux A, generated by a magnetic field, generated in turn by the antenna coil 11 of the reader/ writer 10, for electromagnetically coupling the antenna coils 11, 31 to each other.

0075The induced electromotive force is generated in the parallel resonance circuit 34 by the magnetic flux A traversing the antenna coil 31, so that the induced current I by the induced electromotive force flows through the entire circuit. The parallel resonance circuit 34 is tuned by the induced electromotive force in the vicinity of the frequency fc = 13.56 MHz.

0076When the induced current I flows through the antenna coil 32, a magnetic field is generated in the coil 32.

0077At this time, the non-contact IC card 20 may be moved to the vicinity of the matching tuning circuit 30. Thus, the magnetic flux B, generated by the magnetic field, generated in turn in the antenna coil 32, is passed through the inside of the antenna coil 21, as shown in <figref idref="f0004">Fig.4</figref>. This electro-magnetically couples the antenna coils 32, 21 to each other.

0078When the magnetic flux B traverses the antenna coil 21 of the non-contact IC card 20 in this manner, the non-contact IC card 20 is activated so that the reader/writer 10 and the non-contact IC card 20 are now able to have wireless communication with each other through the matching tuning circuit 30.

0079Referring to the cross-sectional view of <figref idref="f0005">Fig.6</figref>, another embodiment of the reader/ writer 10 and the matching tuning circuit 30 of the invention is hereinafter explained.

0080Referring to <figref idref="f0005">Fig.6</figref>, the reader/writer 10 is mounted on the back-side surface of a metal chassis 51, as a casing of a device, adapted for being loaded with the reader/ writer 10, so that the antenna coil 11 will be in register with an aperture 51A of the metal chassis 51.

0081On the front side surface of the metal chassis 51, having the reader/writer 10 mounted thereon, there is provided a metal component 52, such as a screw, such that the matching tuning circuit 30 cannot directly be mounted thereon, as shown in <figref idref="f0005">Fig.6</figref>.

0082Thus, the matching tuning circuit 30 is mounted in position by bonding the substrate 35 of the matching tuning circuit 30 on the back side surface of a resin cover 53 overlying the aperture 51A of the metal chassis 51.

0083The matching tuning circuit 30 is bonded to the back-side surface of the resin cover 53, so that, when the resin cover 53 is mounted to the metal chassis 51, the antenna coil 31 of the matching tuning circuit 30 is in register with the antenna coil 11 of the reader/ writer 10.

0084The cover 53, to which is bonded the matching tuning circuit 30, is formed of non-magnetic resin, in order to cause no loss of the magnetic flux by the magnetic field generated in the antenna coil 32 of the matching tuning circuit 30. The substrate 35 of the matching tuning circuit 30 is of an extremely thin thickness, and is e.g. a flexible substrate, so as not to affect the magnetic field generated in the antenna coil 32.

0085A shield plate 54 may also be provided in order to prevent the effect of the electromagnetic noise generated in the device designed for carrying the reader/writer 10. The shield plate 54 needs only to be mounted to overlie the antenna coil 11. At this time, caution should be exercised so that the shield plate 54 is kept aloof from the reader/writer 10 in order to prevent the function of the antenna coil 11 from being impaired.

0086The matching tuning circuit 30, mounted to the resin cover 53, may also be mounted to the inner side of a rotatable door, provided to e.g. a casing of the device loaded with the reader/writer 10, in a manner not shown, for saving the spacing.

0087Thus, there is no necessity for providing the wiring for the matching tuning circuit 30, in order for the matching tuning circuit 30 to communicate with the reader/ writer 10, and the matching tuning circuit 30 may be separated from the reader/ writer 10 and mounted freely to any place within the sphere of electro-magnetic coupling. The result is the communication system 1 with an extremely high degree of mounting freedom.

0088In the matching tuning circuit 30 of the above-described communication system 1, the antenna coils 31, 32 are connected in series with each other. In the communication system 1, a matching tuning circuit 40, in which a parallel resonance circuit 41 is made up by a parallel connection of the antenna coils 31, 32 and the tuning capacitor 33, as shown in <figref idref="f0005">Fig.7</figref>, may be used in place of the matching tuning circuit 30. The case of using the matching tuning circuit 40 is not explained in detail because the operation of the communication system 1 gives the identical effect in case the matching tuning circuit 40 is used in place of the matching tuning circuit 30.

0089Meanwhile, the tuning capacitor 33 is connected in series with both the antenna coils 31, 32, as shown in <figref idref="f0005">Fig.7</figref>.

[Embodiment]

0090By way of an embodiment, the results of an experiment, conducted for measuring the effect by the matching tuning circuit 30, are shown.

0091In the experiment, the area which allows for communication for the case of using the matching tuning circuit 30 and that for the case of not using the matching tuning circuit 30, in the wireless communication between the reader/writer 10 and the non-contact IC card 20, were measured and compared to each other.

0092The same experiment was conducted as an iron plate having an aperture of the same shape as the antenna coil 11 of the reader/writer 10 was interposed between the reader/writer 10 and the non-contact IC card 20, in order to verify the effect by the matching tuning circuit 30 under the actual assumed use condition of the matching tuning circuit 30, as shown in <figref idref="f0003">Figs.3</figref> and <figref idref="f0005">6</figref>.

(Experiment 1)

0093In an experiment 1, measurement was made of the area which allows for communication, in case the reader/writer 10 and the non-contact IC card 20 were arranged in a free space devoid of an obstacle, and the reader/writer 10 was activated in this state, and of the area which allows for communication, in case the matching tuning circuit 30 was interposed between the reader/writer 10 and the non-contact IC card 20, and the reader/writer 10 was activated in this state, as shown in <figref idref="f0006">Fig.8</figref>.

0094The antenna coil 11 of the reader/writer 10 was circular in shape, with a diameter on the order of 25 mm. The antenna coil 31 of the matching tuning circuit 30 was of approximately the same shape. The non-contact IC card 20 used was of the size of 54 mm in length, 85.6 mm in width and 0.76 mm in thickness, as provided for in the ISO (International Organization for Standardization). The antenna coil 21, enclosed in the non-contact IC card 20, was wound to approximate the size of the non-contact IC card 20. The antenna coil 32 of the matching tuning circuit 30 was approximately of the same shape as the antenna coil 21.

0095The area which allows for communication, and which is to be measured, is now explained. The area which allows for communication, and which is now to be measured, is defined by a distance for communication Z, representing the distance which allows for communication, in case the non-contact IC card 20 is moved vertically relative to the reader/writer 10, and by a distance for communication XY, representing the distance which allows for communication, in case the non-contact IC card 20 is moved horizontally relative to the reader/writer 10.

0096Specifically, the distance for communication Z is a distance up to which the communication is possible when the center of the antenna coil 11 of the reader/writer 10, placed horizontally, is confounded with the center of the major plane surface of the non-contact IC card 20, and when the non-contact IC card 20 is moved in the vertical direction, as it is kept parallel to the antenna coil 11.

0097The distance for communication XY is a distance up to which the communication is possible when the non-contact IC card 20, placed horizontally at a preset distance with respect to the antenna coil 11 of the reader/writer 10, is optionally moved along the X-axis direction and along the Y-axis direction within the X-Y coordinate plane shown in <figref idref="f0006">Fig.9</figref>. This distance for communication may be found by measuring the trajectory of the center point of the non-contact IC card 20.

0098This distance for communication Z and the distance for communication XY, thus measured, may be used as indexes for the effect of the matching tuning circuit 30.

0099First, <figref idref="f0007">Fig. 10</figref> shows the results of measurement of the distance for communication Z without the matching tuning circuit 30 and the results of measurement of the distance for communication Z with the matching tuning circuit 30 placed in position. Meanwhile, since the matching tuning circuit 30 is mounted at a distance of 10 mm from the antenna coil 11 of the non-contact IC card 10, the distance for communication for the case the matching tuning circuit 30 is placed in position was measured from the position of the intervening matching tuning circuit 30.

0100The distance for communication Z without the matching tuning circuit 30 was 10 to 25 mm, as shown in <figref idref="f0007">Fig. 10</figref>. The same distance Z with the matching tuning circuit 30 interposed in position was 20 to 75 mm. Thus, it may be seen that, by placing the matching tuning circuit 30 between the reader/writer 10 and the non-contact IC card 20, the distance for communication Z is approximately tripled.

0101If, in case the matching tuning circuit 30 is placed in position, the non-contact IC card 20 is at a distance of 10 to 20 mm from the antenna coil 11, the communication becomes infeasible because the non-contact IC card 20 and the matching tuning circuit 30 interfere with each other and become unstable in operation. This inconvenience may be overcome by strictly matching the resonance frequency of the non-contact IC card 20 to that of the matching tuning circuit 30 or by significantly separating the two resonance frequencies from each other.

0102<figref idref="f0007">Fig. 11</figref> shows the results of measurement of the distance for communication XY without the matching tuning circuit 30 and the results of measurement of the distance for communication XY with the matching tuning circuit 30 placed in position.

0103In case the matching tuning circuit 30 is not used, the distance for communication XY was measured at a location separated in the vertical direction by 10 mm from the center of the antenna coil 11 of the reader/writer 10. In case the matching tuning circuit 30 is used, the distance for communication XY was measured at a location separated 10 mm in the vertical direction from the center of the antenna coil 32 of the matching tuning circuit 30.

0104Meanwhile, the location of insertion of the matching tuning circuit 30 is 10 mm away from the reader/writer 10, as set forth above.

0105In the absence of the matching tuning circuit 30, the distance for communication XY is such that -30≤ X (mm) ≤30 and -15 ≤ Y (mm) ≤15, as shown in <figref idref="f0007">Fig. 11</figref>. That is, the distance for communication XY is defined to be the inside of an ellipsis, with a long axis of 60 mm and a short axis of 30 mm, as indicated by a broken line.

0106In case the matching tuning circuit 30 is placed in position, the distance for communication XY is such that -50 ≤ X (mm) ≤50 and -40 ≤ Y (mm) ≤40, as shown in <figref idref="f0007">Fig. 11</figref>. That is, in <figref idref="f0007">Fig. 11</figref>, the distance for communication XY is defined to be the inside of an ellipsis, with a long axis of 100 mm and a short axis of 80 mm, as indicated by a solid line.

0107Thus, it may be seen that, by placing the matching tuning circuit 30 between the reader/ writer 10 and the non-contact IC card 20, the distance for communication XY is quadrupled.

(Experiment 2)

0108In the experiment 2, the reader/writer 10 was bonded to an iron plate 60, which iron plate, stuck to the reader/writer 10, was placed so as to prove an obstacle between the reader/writer 10 and the non-contact IC card 20 to approximate the actual use state, as shown in <figref idref="f0008">Fig.12</figref>. The distance for communication Z and the distance for communication XY were measured for the case in which the matching tuning circuit 30 was used and for the case in which the matching tuning circuit 30 was not used.

0109In the iron plate 60, there is bored an aperture 60A of approximately the same shape as that of the antenna coil 1 of the reader/writer 10. When the reader/writer 10 is stuck to the iron plate 60, attention is to be paid so that the aperture 60A is in register with the antenna coil 11.

0110In the experiment 2, the reader/writer 10, non-contact IC card 20 and the matching tuning circuit 30 used are to be exactly the same as those used in the experiment 1. In using the matching tuning circuit 30, a spacer 61 is interposed between the iron plate 60 and the matching tuning circuit 30, and the separation between the antenna coil 11 of the reader/ writer 10 and the matching tuning circuit 30 is set to 5 mm, as shown in <figref idref="f0008">Fig.12</figref>.

0111The measured results of the distance for communication Z, shown in <figref idref="f0008">Fig. 12</figref>, and those for the distance for communication XY, shown in <figref idref="f0009">Fig. 14</figref>, are shown below. First, <figref idref="f0009">Fig. 15</figref> shows the measured results of the distance for communication Z, in the absence of the matching tuning circuit 30, and those of the distance for communication Z with the matching tuning circuit 30 placed in position. Meanwhile, since the matching tuning circuit 30 in the experiment 2 is placed at a separation of 5 mm from the antenna coil 11 of the reader/writer 10, the distance for communication Z was measured from the position of the matching tuning circuit 30.

0112In the absence of the matching tuning circuit 30, the communication disabled state was invited, in which communication is disabled under the influence of the iron plate 60, as shown in <figref idref="f0009">Fig. 15</figref>. The distance for communication Z, in case the matching tuning circuit 30 was placed in position, was 5 to 35 mm.

0113Thus, by introducing the matching tuning circuit 30 between the reader/writer 10 non-contact IC card 20, the wireless communication by the reader/ writer 10 and the non-contact IC card 20 may be improved from the communication disabled state to a practically satisfactory state.

0114<figref idref="f0010">Fig. 16</figref> shows the measured results of the distance for communication XY in the absence of the matching tuning circuit 30 and those of the same distance with the matching tuning circuit 30 placed in position.

0115In the absence of the matching tuning circuit 30, the distance for communication XY was measured at a position 5mm spaced apart in the vertical direction from the center of the antenna coil 11 of the reader/writer 10 and, in case the matching tuning circuit 30 was placed in position, the same distance XY was measured at a location 5 mm spaced apart from the center of the antenna coil 32 of the matching tuning circuit 30.

0116It is noted that the matching tuning circuit 30 is introduced at a position 5 mm spaced apart from the antenna coil 11 of the reader/writer 10, as noted previously.

0117In case the matching tuning circuit 30 is not used, the communication is disabled, as shown in <figref idref="f0010">Fig.16</figref>. The distance for communication XY is such that -35 ≤ X (mm) ≤ 35 and -20 ≤ Y (mm) ≤ 20. That is, as shown in <figref idref="f0010">Fig.16</figref>, the distance for communication XY is defined to be the inside of an ellipsis, with a long axis of 70 mm and a short axis of 40 mm, as indicated by a solid line in <figref idref="f0010">Fig.16</figref>.

0118Thus, it may be seen that, by placing the matching tuning circuit 30 between the reader/ writer 10 and the non-contact IC card 20, the wireless communication by the reader/ writer 10 and the non-contact IC card 20 may be improved from the communication disabled state to a practically satisfactory state.