JP2005102185A - Loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna where a plurality of loop antenna cells are combined, where the total of magnetic moments generated from the loop antenna cells becomes zero as possible by compensating degradation in balance among the loop antenna cells caused by changes in the operation environment. <P>SOLUTION: The direction of magnetic moment of the signal transmitted to a non-contact type data carrier 3 of a plurality of small loop antenna cells 61, 62, and 63 which couple magnetically with an antenna coil 8 of the non-contact type data carrier 3 is so configured as to be opposite to each other. The sum of magnetic moments generated from all the small loop antenna cells 61-63 becomes zero. A conductor constituting a short ring pattern 67 is arranged to the plurality of small loop antenna cells so that a degradation in balance among the small loop antenna cells 61-63 is compensated with the short ring pattern 67. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a loop antenna device, and is particularly suitable for use in a reader / writer device of an electromagnetic induction type non-contact data carrier system that transmits / receives data to / from a plurality of data carriers in a non-contact manner.

  Conventionally, in a data carrier system including a reader / writer device and a data carrier, data and commands are sent to the data carrier by modulating the alternating magnetic field supplied to the service area from the antenna device of the reader / writer device. ing.

  In the data carrier, an electromotive voltage generated by receiving the alternating magnetic field supplied to the service area with a built-in coil is rectified to serve as an operation power source for the data carrier. Further, the modulation applied to the alternating magnetic field is demodulated, data and commands sent from the reader / writer device are received, and predetermined operations such as transmitting data to the reader / writer according to the commands are performed.

  In such a data carrier system, the strength of the alternating magnetic field supplied from the reader / writer to a predetermined service area is limited to a predetermined range, and only the weakest magnetic field is generated outside the service area. It is desirable to do so.

  It is obvious that it is necessary to supply a strong alternating magnetic field within a predetermined range in the service area, but it is desirable to make the alternating magnetic field reaching the outside of the service area as weak as possible. This is because when a plurality of reader / writer devices such as those described above are installed side by side as in an automatic ticket gate system, they do not interfere with each other's operation or reduce adverse effects on other devices. As a conventional antenna device of this type, for example, there is Patent Document 1.

  Conventionally, a plurality of loop antenna cells are combined under the following conditions to satisfy the above-described requirements.

ここで、Ｎｉは各ループアンテナセルの巻き数、Ｉｉは各ループアンテナセルに流れる電流であり、流れる方向によって正負をつけて扱う。また、Ｓｉは各ループアンテナセルの面積であり、「ＮｉＩｉＳｉ」はｉ番目のループアンテナセルが発生する磁気モーメントである。

Here, Ni is the number of windings of each loop antenna cell, and Ii is a current flowing through each loop antenna cell, and is handled with positive and negative depending on the flowing direction. Si is the area of each loop antenna cell, and “NiIiSi” is the magnetic moment generated by the i-th loop antenna cell.

  The above-described conventional loop antenna device utilizes the fact that an alternating magnetic field that reaches farther than the size of each loop antenna cell can be weakened. When the strength of the alternating magnetic field generated from such a loop antenna device was measured, it was confirmed that the strength of the alternating magnetic field suddenly decreased when moving away from the loop size.

Japanese Patent Laid-Open No. 10-209737

  However, in order to stably reproduce such an action, it is only when the loop antenna device is installed alone in the measurement environment. That is, as described above, even if the loop antenna device is designed so that the strength of the alternating magnetic field rapidly decreases when the distance is larger than the loop size, the balance between the loop antenna cells is lost due to the influence of the surrounding environment. There is a problem that a strong magnetic field reaches a position far from the loop size.

  That is, the balance between the loop antenna cells in the loop antenna device may be disrupted when a metal or the like is installed asymmetrically near the antenna and an induced current flows through the metal to generate a magnetic field. For this reason, when the loop antenna device is incorporated in the reader / writer device, there is a problem that the balance between the loop antenna cells is lost.

  Even if the loop antenna device is incorporated in the reader / writer device in a well-balanced manner, when the reader / writer device is installed, the balance including the surrounding environment of the loop antenna device is substantially effective. Was impossible.

  In addition, when the tag is placed on a specific antenna cell, there is a problem that the balance between the loop antenna cells is broken as in the case described above due to the induced current flowing in the coil of the tag. That is, there is a problem that the balance between the loop antenna cells is likely to be lost during operation only by adjusting the sum of the magnetic moments to “0” by combining a plurality of loop antenna cells.

  In view of the above-mentioned problems, the present invention compensates for a loss of balance between the loop antenna cells caused by a change in the operating environment in a loop antenna device in which a plurality of small loop antenna cells are combined. The object is to always reduce the sum of the magnetic moments to be minimized.

  The loop antenna apparatus of the present invention includes a plurality of small loop antenna cells that are magnetically coupled to an antenna coil of a non-contact type data carrier, and transmits a signal to the non-contact type data carrier. The plurality of small loop antenna cells are configured such that the directions of magnetic moments of signals transmitted to the non-contact type data carrier are opposite to each other, and are generated from all the small loop antenna cells. The sum of the magnetic moments is set to 0, and the conductors constituting the short ring are arranged for the whole of the plurality of small loop antenna cells.

  Another feature of the present invention is characterized in that the conductors constituting the plurality of small loop antenna cells and the conductors constituting the short ring are laminated on a substrate. .

  Another feature of the present invention is that each of the plurality of small loop antenna cells is provided with an electric field shielding conductor for reducing an electric field component radiated from each small loop antenna cell. Each of the electric field shielding conductors is characterized in that a gap for preventing a short ring from being formed is formed.

  According to the present invention, in a loop antenna apparatus having a plurality of small loop antenna cells that are magnetically coupled to an antenna coil of a non-contact type data carrier and transmitting a signal to the non-contact type data carrier, A plurality of small loop antenna cells are configured such that the directions of magnetic moments of signals transmitted to the non-contact type data carrier are opposite to each other, so that the magnetism generated from all the small loop antenna cells Since the sum of moments is set to 0, and a conductor that forms a short ring is provided for the plurality of small loop antenna cells, the balance between the loop antenna cells is influenced by the surrounding environment. When collapsed, an induced current flows through the conductor constituting the short ring, and each loop antenna is caused by a magnetic field generated by the induced current. It is possible to compensate for the imbalance between Le. As a result, even if a metal or the like is placed asymmetrically near the antenna or the data carrier is placed on a specific antenna cell, the sum of the magnetic moments is set to “0” by combining a plurality of loop antenna cells. In such a loop antenna device, even when the balance between the loop antenna cells is lost during operation, it is possible to compensate well and prevent unnecessary electromagnetic waves from being radiated far away.

  Next, an embodiment of a loop antenna device of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an example of a situation in which the loop antenna device of the present embodiment is used, and shows a state where the data carrier 3 is brought close to the service area SA of the reader / writer device 2.

  As shown in FIG. 2, the transmission loop antenna apparatus according to the present embodiment includes three small loop coils 61, a second small loop coil 62, and a third small loop coil 63 on a substrate 60. A loop coil is formed. The loop antenna device of the present invention can be applied to a structure having more small loop coils.

  The first small loop coil 61 has an area twice that of the second small loop coil 62 and the third small loop coil 63. Further, as shown in FIG. 2, the alternating magnetic field 61a generated by the first small loop coil 61, and the alternating magnetic fields 62a and 63a generated by the second small loop coil 62 and the third small loop coil 63. The direction is reversed.

  As shown in FIG. 3, electric field shields 64 to 66 are disposed on the first to third small loop coils 61, 62, and 63. These electric field shields 64 to 66 are disposed to shield electric field components radiated from the first to third small loop coils 61, 62, and 63.

  That is, a high frequency power signal is radiated from each small loop coil 61, 62, 63 in the form of an electric field and a magnetic field. However, a magnetic field component is necessary for the operation and communication in the data carrier system, and the electric field component is not preferable because it hinders communication between another reader / writer and the data carrier and communication in another wireless device.

  Therefore, as shown in FIG. 3, in the present embodiment, a first electric field shielding conductor 64 is provided for the first small loop coil 61, and a second electric field is provided for the second small loop coil 62. The shield conductor 65 and the third electric field shield conductor 66 are arranged for the third small loop coil 63, respectively. Although not shown, the first electric field shield conductors 64, 65, 66 and the small loop coils 61, 62, 63 are electrically insulated by interposing an electric insulating layer.

  The first electric field shield conductor 64 is provided with a gap 64a, the second electric field shield conductor 65 is provided with a gap 65a, and the third electric field shield conductor 66 is provided with a gap 66a. Is provided.

  Thereby, in the electromagnetic waves radiated from the first small loop coil 61 to the third small loop coil 63, the electric field component is shielded by the first electric field shield conductor 64 to the third electric field shield conductor 66. The gaps 64a, 65a and 66a are provided to prevent the occurrence of magnetic field components.

  Further, a short ring pattern 67 is disposed so as to overlap the electric field shielding conductors 64, 65 and 66. The short ring pattern 67 is a short ring pattern for the three small loop coils 61, 62, 63. Although not shown, an electric insulation layer is disposed between the electric field shield conductors 64, 65 and 66 and the short ring pattern 67.

  Since the short ring pattern 67 has gaps 67a and 67b, it is not a short ring for each of the three small loop coils 61, 62 and 63. For this reason, when the balance between the three small loop coils 61, 62, 63 is lost, an induced current flows through the short ring pattern 67 to generate a magnetic field, and the magnetic moment of the entire loop antenna device is zero. It is trying to become.

  That is, in the loop antenna device of the present embodiment, it is possible to perform good communication with the data carrier by reducing the radiation of the electric field component that hinders the operation and communication in the data carrier system as much as possible. I can do it. Further, a short ring pattern 67 that also serves as a shield is provided on the outer periphery of a loop antenna device in which a plurality of loop antenna cells 61, 62, 63 are combined.

  That is, in the case of the loop antenna device of the present embodiment, since the sum of the magnetic moments radiated from the plurality of loop antenna cells 61, 62, 63 is “0”, a short circuit that also serves as an outer shield. Originally, no current flows through the ring pattern 67.

  However, when a metal or the like comes around and the balance between the small loop antenna cells 61 to 63 is lost, a current is induced in the short ring pattern 67 to generate a magnetic field, and the generated magnetic field causes the overall balance to be lost. It works to correct. The same applies to the case where the overall balance is lost due to the arrival of the data carrier on a specific antenna cell.

  That is, in the present embodiment, a plurality of loop antenna cells 61 to 63 are combined so that the sum of magnetic moments generated from all the loop antenna cells is zero, and the short ring pattern 67 also serves as a shield on the outer periphery. By providing the loop antenna, there is an effect that the characteristics of the loop antenna that supplies a strong magnetic field in the vicinity and emits a weak magnetic field in the distance can be maintained even when the balance is lost due to a metal or data carrier approaching at the time of installation. In addition, it is possible to obtain an effect of suppressing a change width in which a large number of data carriers concentrate on a specific antenna cell and the magnetic field strength in the antenna cell region changes.

  FIG. 5 shows an exploded perspective view of the loop antenna device of the present embodiment. As shown in FIG. 5, the loop antenna device of the present embodiment includes a plurality of first small loop coils 61, second small loop coils 62, and third small loop coils 63 formed on a substrate 60. The loop antenna is configured.

  Further, short rings 67 that also serve as electric field shields are provided above and below the plurality of loop antennas. Further, in the loop antenna device of the above-described embodiment, the short ring pattern 67 also has the effect of electric field shielding, so the electric field shields 64 to 66 are omitted in the exploded perspective view of FIG.

  Further, in the embodiment shown in FIG. 5, the short ring pattern 67 on the opposite side of the surface of the substrate 60 on which the small loop coils 61, 62, 63 are formed, It is also possible to arrange them at different positions. Also in this case, as described above, an electrical insulating layer is disposed between the small loop coils 61, 62, 63 and each short ring pattern 67.

  Next, an example of a data carrier system using the loop antenna device of the present embodiment will be described with reference to FIG.

  In the reader / writer 2, data from the host 1 or the like is processed by the CPU 15 and sent to the transmission circuit 12. The transmission circuit 12 is supplied with a high-frequency signal having a constant amplitude from the oscillation circuit 11, and the high-frequency signal is modulated with the data and a modulated high-frequency signal is output.

  This modulated high-frequency signal is sent to the transmission coil 6 formed on the substrate 60 via the driver 13. The transmission coil 6 is constituted by a first small loop coil 61, a second small loop coil 62, and a third small loop coil 63 in the present embodiment.

  The data carrier 3 is close to the reader / writer 2, and the transmission coil 6 of the reader / writer 2 and the antenna coil 8 of the data carrier 3 are electromagnetically coupled. Therefore, in the data carrier 3, a modulated high frequency signal is supplied to the transmission / reception circuit 4 from the transmission coil 6 of the reader / writer 2 via the antenna coil 8 of the data carrier 3.

  This modulated high-frequency signal is rectified by the rectifier circuit 21 and supplied to the power supply circuit 22 to generate a predetermined power supply voltage necessary for each part of the data carrier 3. The output signal of the antenna coil 8 is also supplied to the receiving circuit 23, where the data is demodulated and supplied to the CPU 5. The CPU 5 operates based on the outputs of the timing circuit 25 and the reset circuit 26, processes the supplied data, and writes predetermined data in a memory (not shown).

  Finally, a case where data is transmitted from the data carrier 3 to the reader / writer 2, that is, a reception mode will be described.

  From the transmission circuit 12 of the reader / writer 2, a high-frequency signal with no modulation and a constant amplitude is output and sent to the data carrier 3 through the driver 13, the transmission coil 6 and the antenna coil 8.

  At this time, the data carrier 3 is approaching the reader / writer 2, and the transmission coil 6 of the reader / writer 2 and the antenna coil 8 of the data carrier 3 are magnetically coupled. Therefore, in the data carrier 3, a high frequency signal is supplied from the transmission coil 6 of the reader / writer 2 to the transmission / reception circuit 4 via the antenna coil 8 of the data carrier 3. The high-frequency signal is rectified by the rectifier circuit 21 and supplied to the power supply circuit 22 to generate a predetermined power supply voltage necessary for each part of the data carrier 3.

  On the other hand, in the data carrier 3, data read from a memory (not shown) is processed by the CPU 5 and supplied to the transmission circuit 24. The transmission circuit 24 is composed of, for example, a load resistor and a switch, and this switch is turned on and off according to the “1” and “0” bits of data. When the switch of the transmission circuit 24 is turned on and off in this way, the load on the antenna coil 8 varies.

  For this reason, in the reader / writer 2, the amplitude of the high-frequency current flowing through the receiving coil 7 varies. That is, the high frequency current is amplitude-modulated by data supplied from the CPU 5 of the data carrier 3 to the transmission circuit 24. The modulated high frequency signal is demodulated by the receiving circuit 14 to obtain data. This data is processed by the CPU 15 and sent to the host 1 or the like.

  By the way, the data carrier 3 can be used for data on a plurality of books or products, such as book management and product inventory management, in addition to handling one card at a time, such as credit cards and electronic money. There are cases in which a plurality of cards are handled at a time, such as attaching the carrier 3 one by one and reading the information of these books or products with the reader / writer 2 or searching for a specific one of these books or products. is there.

  In such a case, it is necessary to reduce the data carrier 3 and increase the transmission / reception coils 6 and 7 of the reader / writer 2. Further, when the data carrier 3 is reduced, the built-in antenna coil 8 is naturally reduced. Therefore, in order to supply power necessary for operating the data carrier 3, the transmitter coil 6 of the reader / writer 2 is supplied. It is necessary to increase the strength of the generated magnetic field.

  On the other hand, as described above, it is necessary to prevent unnecessary electromagnetic waves from being emitted outside the service area SA. As described above, the transmission coil 6 according to the present embodiment combines a plurality of loop antenna cells 61 to 63 to reduce the sum of magnetic moments generated from all the loop antenna cells to 0 and to provide a shield on the outer periphery. A short ring pattern 67 is also provided.

  As a result, the characteristics of a loop antenna that supplies a strong magnetic field in the vicinity and emits a weak magnetic field in the distance can be maintained even when the metal or data carrier approaches and loses balance during installation. The request can be fully satisfied.

  Hereinafter, measurement examples of specific effects will be shown.

  As shown in FIG. 7, 60 mm × 120 mm loop coils 71 and 72 are arranged in parallel. Here, the “number of windings” of the first loop coil 71 and the second loop coil 72 is 15 T, the “inductance L value is 130 μH”, and the “Q value is 33”. These values are constant regardless of the presence or absence of a short ring. Further, “the measurement frequency is 125 KHz”, and the magnetic field is detected when the magnetic field at the detection point 73 that is balanced at the center point is zero.

  And, when there is no short ring pattern, if a 40 mm square aluminum plate 74 having a thickness of 1 mm is placed 20 mm below the first loop coil 71 side, the balance with the first loop coil 71 is lost. A magnetic field is detected.

  FIG. 8 is a diagram showing an experimental example for detecting the strength of the magnetic field generated when the balance between the loop antennas is lost when there is a short ring pattern.

  As shown in FIG. 8, even when the short ring pattern 75 is present, if the 1 mm thickness of a 40 mm square aluminum plate is placed 20 mm below the first loop coil 71 side, The balance with the loop coil 72 is lost and the magnetic field is detected, but the magnetic field intensity at the detection point is suppressed to half that when the short ring pattern is not attached, and the balance is less lost. I was able to confirm.

  Further, according to the experimental results, even when the same coil is used and 10 data carriers are placed only on one antenna cell side, the magnetic field strength ratio from the left and right is “100: 100 → 92: 100 ".

  On the other hand, when the short ring pattern is provided, “100: 100 → 96: 100”. As is clear from these results, it can be seen that the balance loss is smaller with the short ring pattern.

It is a figure which shows embodiment of this invention and shows a mode that the data carrier is brought close to the service area of a loop antenna apparatus. It is a figure which shows the loop antenna apparatus of embodiment of this invention, and shows a mode that three small loop coils are arrange | positioned on the board | substrate. It is a figure which shows a mode that the conductor for electric field shielding is arrange | positioned on three small loop coils. It is a figure which shows a mode that the short ring pattern is arrange | positioned on the antenna coil pattern. It is a disassembled perspective view for demonstrating the modification of embodiment and demonstrating the main structures of a loop antenna apparatus. It is a block diagram which shows schematic structure of a data carrier system. It is a figure which shows the experiment example which detects the intensity | strength of the magnetic field generated when the balance between loop antennas collapses when there is no short ring pattern. It is a figure which shows the experiment example which detects the intensity | strength of the magnetic field generate | occur | produced when the balance between loop antennas collapses when there exists a short ring pattern.

Explanation of symbols

1 Host 2 Reader / Writer Device 3 Data Carrier 4 Transmission / Reception Circuit 5 CPU
6 Transmission coil 7 Reception coil 8 Antenna coil 11 Oscillation circuit 12 Transmission circuit 13 Driver 15 CPU
21 rectifier circuit 22 power supply circuit 23 reception circuit 24 transmission circuit 25 timing circuit 26 reset circuit 60 substrate 61 first small loop coil 62 second small loop coil 63 third small loop coil 64 first electric field shielding conductor 64a Gap 65 Second electric field shield conductor 65a Gap 66 Third electric field shield conductor 66a Gap 67 Short ring pattern 67a Gap 67b Gap

Claims (3)

In a loop antenna device having a plurality of small loop antenna cells magnetically coupled to an antenna coil of a non-contact type data carrier, and transmitting a signal to the non-contact type data carrier,
The plurality of small loop antenna cells are configured such that directions of magnetic moments of signals transmitted to the non-contact type data carrier are opposite to each other, and are generated from all the small loop antenna cells. A loop antenna characterized in that the sum of the magnetic moments is zero, and a conductor constituting a short ring is arranged for all the plurality of small loop antenna cells. apparatus.   2. The loop antenna device according to claim 1, wherein the conductor constituting the plurality of small loop antenna cells and the conductor constituting the short ring are laminated on a substrate. Each of the plurality of small loop antenna cells is provided with an electric field shield conductor for reducing an electric field component radiated from each small loop antenna cell, and each of the electric field shield conductors is short-circuited. The loop antenna device according to claim 1, wherein a gap for preventing the ring from being formed is formed.

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