JP4071858B2 - Antenna device for reader / writer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device for a reader / writer, and more particularly to an antenna device and a device for canceling noise in an equivalent device, and more particularly to a non-contact type magnetically coupled to a transmitting antenna coil means of a non-contact type IC card. The present invention relates to an antenna device for a reader / writer that receives a signal sent to an IC card.
[0002]
[Prior art]
In the information era in recent years, so-called IC cards equipped with ICs have been put into practical use in the card field such as electronic money and credit cards. As a method of supplying power to the IC card from a recording medium writing / reading device (reader / writer) or exchanging data, a method of magnetically non-contacting using an antenna coil has been proposed. This method is expected to become the mainstream in the future because it is superior in handling and durability as compared with a contact-type method that requires electrical contacts.
[0003]
FIG. 6 shows an example of this non-contact type IC card and reader / writer. Further, FIG. 7 shows an enlarged three-dimensional perspective view of the transmitting coil 6 and the receiving coil 7 of the reader / writer 2 and the antenna coil 8 of the IC card 3 in FIG. 6, and a sectional view in the XZ direction of FIG. Is shown in FIG.
[0004]
In FIG. 6, the operation relationship between the reader / writer 2 and the IC card 3 is as follows: (1) a state in which only power is supplied from the reader / writer 2 to the IC card 3 (standby mode), and (2) the reader / writer 2 to the IC card 3 There are roughly three states: a state in which data is transmitted (transmission mode) and a state in which data is transmitted from the IC card 3 to the reader / writer 2 (reception mode).
[0005]
The outline of the internal operation of the reader / writer 2 and the IC card 3 in each state will be described below with reference to the drawings.
[0006]
First, the case where only power is supplied from the reader / writer 2 to the IC card 3, that is, the standby mode will be described. In FIG. 6, the reader / writer 2 supplies a high-frequency signal having a constant amplitude from the oscillation circuit 11 to the transmission circuit 12 and sends it to the transmission coil 6 via the driver 13.
[0007]
At this time, when the IC card 3 is attached to the reader / writer 2, the transmission coil 6 of the reader / writer 2 and the antenna coil 8 of the IC card 3 are electromagnetically coupled.
[0008]
Therefore, in the IC card 3, a 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 IC card 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 IC card 3.
[0009]
Next, a case where data is transmitted from the reader / writer 2 to the IC card 3, that is, a transmission mode will be described. In FIG. 6, 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.
[0010]
In the transmission circuit 12, a high-frequency signal having a constant amplitude is supplied from the oscillation circuit 11 as in the standby mode described above, and the high-frequency signal is modulated with data and a modulated high-frequency signal is output. This variable high-frequency signal is sent to the transmission coil 6 via the driver 13. At this time, the IC card 3 is mounted on the reader / writer 2, and the transmission coil 6 of the reader / writer 2 and the antenna coil 8 of the IC card 3 are electromagnetically coupled.
[0011]
Therefore, in the IC card 3, a 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 IC card 3. This high-frequency signal is rectified by the rectifier circuit 21 in the same manner as in the standby mode described above, and supplied to the power supply circuit 22 to generate a predetermined power supply voltage necessary for each part of the IC card 3.
[0012]
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).
[0013]
Finally, a case where data is transmitted from the IC card 3 to the reader / writer 2, that is, a reception mode will be described. In FIG. 6, a high-frequency signal with no modulation and a constant amplitude is output from the transmission circuit 12 of the reader / writer 2 and sent to the IC card 3 via the driver 13, the transmission coil 6 and the antenna coil 8.
[0014]
At this time, the IC card 3 is mounted on the reader / writer 2, and the transmission coil 6 of the reader / writer 2 and the antenna coil 8 of the IC card 3 are electromagnetically coupled.
[0015]
Therefore, in the IC card 3, a 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 IC card 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 IC card 3.
[0016]
On the other hand, in the IC card 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 includes, for example, an additional resistor and a switch, and this switch is turned on and off according to the “1” and “0” bits of data.
[0017]
In the reader / writer 2, when the switch of the transmission circuit 24 is turned on and off as described above, the load on the antenna coil 8 fluctuates, and therefore the amplitude of the high-frequency current flowing through the reception coil 7 fluctuates. That is, the high frequency current is amplitude-modulated by data supplied from the CPU 5 of the IC card 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.
[0018]
By the way, as described above, the IC card 3 operates based on the voltage received and induced by the antenna coil 8, and the power that can be used in the IC card 3 is usually a very small level of several mW or less. Therefore, the fluctuation range of the load of the antenna coil 8 based on the operation of the transmission circuit 24 is also small, and the transmission signal to the reader / writer 2 is much smaller than the reception signal from the reader / writer 2.
[0019]
Here, as shown in FIG. 7, the transmission coil 6, the reception coil 7, and the antenna coil 8 are often arranged so as to be horizontally stacked on the XY plane. In this case, as shown in FIG. 8. Both the magnetic flux 30 from the transmission coil 6 and the magnetic flux 31 from the antenna coil pass through the reception coil 7. Therefore, there is a problem that it is difficult to detect a signal from the antenna coil 8 that is very weak with respect to a signal from the transmission coil 7.
[0020]
Furthermore, there is a possibility that the receiving coil 7 picks up surrounding noise signals 32 in addition to the above-described signals. When these noise signals are in the same frequency band as the signal from the antenna coil 8, the detection sensitivity is increased. There was a problem that the receiving coil would malfunction even if it was raised.
[0021]
Therefore, as a method for canceling the signal from the transmission coil 6 and noise from the surrounding environment, it is conceivable to use an antenna device as described in JP-A-7-30319 as the reception coil 7. . FIG. 9 shows a schematic plan view of the antenna device having the noise canceling property.
[0022]
In FIG. 9, the antenna is divided into two halves 41 and 42, each having the same surface area and number of turns, and the half 41 is in the winding orientation with respect to the half 42. Are connected 180 degrees opposite. Therefore, when magnetic fluxes of equal density pass through the antenna, the same amount of current flows through the half body 41 and the half body 42 in opposite directions, so that the current is effectively canceled when viewed as the entire antenna loop.
[0023]
On the other hand, the signal from the IC card 3 is such that the area of the antenna coil 8 is made smaller than the areas of the halves 41 and 42 of the receiving coil 7 and the antenna coil 8 and the receiving coil 7 are arranged at a short distance. Can be prevented from being canceled out.
[0024]
[Problems to be solved by the invention]
However, when the antenna device described above is used as a receiving coil, a dead band 43 is generated at the boundary between the half body 41 and the half body 42, and thus the signal from the antenna coil 8 of the IC card 3 is generated by this dead band. In this case, there is a problem that the signal cannot be detected.
[0025]
Further, when the signal from the antenna coil 8 passes evenly through the half body 41 and the half body 42, there is a problem that the signal is canceled out in the same manner as the noise and the signal from the transmission coil 6, and detection is impossible.
[0026]
Accordingly, an object of the present invention is to provide a reader / writer receiving antenna device that is magnetically coupled to a transmission antenna coil of a contactless IC card and receives a signal transmitted from the contactless IC card. It is an object of the present invention to provide an antenna device that efficiently detects a signal sent from the IC contactless card to a reader / writer while efficiently canceling a signal other than a signal sent to the reader / writer.
[0027]
[Means for Solving the Problems]
An antenna device for a reader / writer according to the present invention is magnetically coupled to a transmitting antenna coil means of a non-contact type IC card, and is provided in an antenna device for a reader / writer that receives a signal transmitted from the non-contact type IC card. An apparatus comprising a plurality of basic coils of at least four or more, wherein each of the plurality of basic coils includes a first small loop coil having a clockwise winding direction, and a counterclockwise A plurality of small loop coils classified as the second small loop coil having the direction of the surrounding winding are arranged in contact with each other so that the winding directions of adjacent small loop coils are opposite to each other. And the plurality of basic coils are arranged in a plane perpendicular to the magnetic flux generated from the transmitting antenna coil means of the non-contact type IC card. Is shifted upward with respect to the first basic coil, the third basic coil is shifted right with respect to the first basic coil, and the fourth basic coil is with respect to the first basic coil. By being shifted in the upward direction and the right direction, a dead zone generated in a region where the small loop coils in the first basic coil to the fourth basic coil are in contact with each other, and among the plurality of basic coils The signal sensing part which is an internal area | region of any one of these is made to overlap.
[0028]
Another feature of the reader / writer antenna device according to the present invention is that a plurality of basic coils are arranged so as to be shifted from each other by half the length of the small loop coil.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a reader / writer antenna device of the present invention will be described below with reference to the drawings.
FIG. 1 is a three-dimensional perspective view of the antenna device according to the first embodiment, and FIG. 2 shows an arbitrary one of the four-layer basic coils shown in FIG. 1 (here, the basic coil 51) from above. FIG. 3 is a plan view of FIG. 1 viewed from above.
[0038]
Note that the circuit block diagram when the antenna device according to this embodiment is used as a receiving coil of a reader / writer is the same as in FIG. 6, and the positional relationship between the antenna coil and the transmitting coil is the same as in FIGS. The description is omitted. Further, when the antenna device according to this embodiment is used as a receiving coil of a reader / writer, the method for receiving a signal from the IC card is the same as the method already described in the description of FIGS. Description is omitted.
[0039]
As shown in FIG. 1, the antenna device of the present embodiment is composed of four basic coils 51 to 54, each coil is disposed horizontally on the XY plane, and is layered at a predetermined interval in the Z direction. It is piled up. All four coils have a structure in which a plurality of small loop coils are coupled as shown in FIG.
[0040]
In the small loop coils 55 to 58 having the same surface area as the number of windings, the adjacent small loop coils are arranged so that the winding directions of the coils are reversed. When the winding direction of the small loop coil 55 in FIG. 2 is a clockwise direction, the winding direction of the small loop coil 56 on the right side in FIG. 2 and the winding direction of the small loop coil 57 in the lower side of FIG. Counterclockwise. The winding direction of the small loop coil 58 located diagonally is the same clockwise direction as the small loop coil 55. That is, it can be said that the small loop coils 55 and 58 form a first small loop coil group, and the small loop coils 56 and 57 form a second small loop coil group.
[0041]
When a vertical magnetic field is generated in the forward direction from the back side of the drawing, a clockwise current is generated in each of the small loop coils 55 to 58 as indicated by arrows in FIG. The small loop coils 55 and 58 generate a current in the same direction as the winding direction, but the small loop coils 56 and 57 generate a current in the direction opposite to the winding direction.
[0042]
Therefore, when the strength of the magnetic field passing through each small loop coil is equal, the current generated in the small loop coils 55 and 58 and the current generated in the small loop coils 56 and 57 cancel each other, and between the terminals a and b. The current output to is zero.
[0043]
The length (L) of one side of the small loop coil is set based on the following equation (1).
(IC coil antenna coil coil size) + maximum communication distance × coefficient A (1) (where 1 ≦ A ≦ 2)
[0044]
If the length of one side is made shorter than the value obtained from the equation (1), the magnetic field lines generated from the antenna coil of the IC card may pass over a plurality of small loop coils, canceling each other and reducing the detection sensitivity. Not practical to do.
[0045]
Also, if the length of one side is made longer than the value obtained from the above equation (1), the ability to cancel noise decreases, or the lines of magnetic force emitted from the antenna coil of the IC card pass through one small loop coil. However, since it passes through the same coil again and returns to the antenna coil side, the lines of magnetic force are canceled and the detection sensitivity may be lowered, which is not practical.
[0046]
In FIG. 3, when the antenna device is viewed from above, the basic coil 52 is L × 7/8 in the X and Y directions, and the basic coil 53 is L × 7/8 in the Y direction. The coil 54 is arranged so as to be shifted by L × 7/8 in the X direction.
[0047]
The larger the amount by which the basic coil is shifted, the larger the area 71 for detecting the signal from the antenna coil 8 can be made. However, if the area where the basic coils overlap is reduced, the detection sensitivity at that portion decreases. There is a fear. Therefore, in the present embodiment, the amount by which the basic coil is shifted is balanced by L × 7/8. However, this amount is not fixed to L × 7/8, and is variable between 0 and L.
[0048]
The magnetic field lines generated from the antenna coil 8 of the IC card are not only perpendicularly incident on the receiving coil 7 but also spread outward as the distance from the antenna coil 8 increases. It extends to the external region of the coils 51-54. This external region depends on the size of the antenna coil 8 and the distance between the antenna coil 8 and the receiving coil 7.
[0049]
With such an arrangement, the signal sensing part (the internal area of the coil) of one of the other three basic coils overlaps the boundary of the small loop coil in one basic coil. Therefore, when only one basic coil 51 is used as an antenna device as in the prior art, for example, the B portion in FIG. 3 becomes a dead zone and a signal from the IC card cannot be detected. In the embodiment, this portion can be detected by the basic coil 53.
[0050]
In other words, there is always a dead band in one basic coil, but the dead band disappears as a whole when a plurality of basic coils of the same shape are overlapped with the position of the dead band overlapped. Signals from the IC card can be detected in all areas.
[0051]
In addition, each basic coil is composed of a plurality of small loop coils having the same surface area and the same number of turns, and by connecting the adjacent small loop coils opposite to each other in the winding direction, signals from the transmission coil and external signals can be obtained. Noise can be canceled out.
[0052]
As described above, the antenna device according to the present embodiment has a single antenna in which a plurality of square small loop coils having the same surface area and the same number of turns are connected so that the winding directions of adjacent ones are opposite to each other. When a plurality of basic coils are projected from the direction in which the magnetic flux passes, they are arranged in layers so that the sides of the small loop coil of the basic coil do not overlap, so that signals from the transmission coil and external Noise is canceled out, and only the signal sent from the IC card can be detected efficiently.
[0053]
Further, as a second embodiment of the present invention, when a region in which a signal from an antenna coil is desired to be detected is wide, four basic coils 51 to 54 used in the antenna device of the first embodiment are connected to each other. In total, 16 basic coils 59 to 62 composed of small loop coils are formed, and as shown in FIG. 4, these 4 basic coils 59 to 62 are shifted by L / 2 in the X and Y directions. It is also possible to configure the antenna device by disposing them.
[0054]
Also in this case, the basic coils 59 to 62 are arranged horizontally on the XY plane, and are laminated in layers in the Z direction perpendicular to the plane. Also in the present embodiment, as in the first embodiment, the amount by which the basic coil is displaced is not fixed at L / 2, but is variable between 0 and L.
[0055]
However, since the ratio of the length of the small loop coil to the length of the basic coil decreases as the number of small loop coils increases, the width of the signal detection area 72 changes so much even if the amount of shifting the basic coil is changed. do not do.
[0056]
Furthermore, as a third embodiment of the present invention, when the noise source is at a specific position, the antenna device is configured by combining basic coils 63 to 65 composed of rectangular small loop coils as shown in FIG. It can also be configured.
[0057]
Although the basic coils 63 and 64 are composed of two small loop coils having the same area, the basic coil 65 has an area obtained by adding the areas of these small loop coils between two rectangular small loop coils. A rectangular small loop coil is arranged.
[0058]
The coils 63 to 65 are horizontally arranged on the XY plane, and are stacked in layers in the Z direction perpendicular to the plane with a predetermined interval. In this case, the noise source is located perpendicular to the Y axis and above the center of the antenna device in FIG.
[0059]
Although the length of the short side of the rectangle of the small loop coil is defined in accordance with the above-described equation (1), since the long side can be made longer than this, there is an advantage that the number of small loop coils can be reduced. .
[0060]
The present invention is not limited to the above embodiment, and various design changes can be made within the spirit of the present invention, for example, the shape of the small loop coil is not a square or a rectangle but a triangle.
[0061]
【The invention's effect】
As described above, according to the present invention, in the reader / writer antenna device that is magnetically coupled to the transmission antenna coil of the non-contact type IC card and receives a signal transmitted from the IC card, at least four or more In the plane perpendicular to the magnetic flux generated from the transmitting antenna coil means of the non-contact type IC card, the second basic coil becomes the first basic coil. The third basic coil is shifted to the right with respect to the first basic coil, and the fourth basic coil is shifted upward and to the right with respect to the first basic coil. A dead zone generated in a region where the small loop coils of the first basic coil to the fourth basic coil are in contact with each other, and the plurality of basic coils It becomes possible to overlap the signal sensor is an internal region of either coil of, while canceling signals other than those transmitted from the IC card to the reader writer, a signal sent from the IC card to the reader writer An antenna device that detects efficiently can be obtained.
[Brief description of the drawings]
FIG. 1 is a three-dimensional perspective view of an antenna device according to a first embodiment of the present invention.
FIG. 2 is a plan view of one basic coil of FIG.
3 is a plan view of the antenna device of FIG. 1. FIG.
FIG. 4 is a plan view of an antenna device according to a second embodiment of the present invention.
FIG. 5 is a plan view of an antenna device according to a third embodiment of the present invention.
FIG. 6 is a block diagram showing a circuit configuration of a non-contact type IC card and a reader / writer.
7 is a three-dimensional perspective view in which the transmission / reception coil and antenna coil portions of FIG. 6 are enlarged. FIG.
8 is a cross-sectional view perpendicular to the Y direction of FIG.
FIG. 9 is a plan view of a conventional antenna device.
[Explanation of symbols]
2 Reader / Writer 3 IC Card 6 Transmitting Coil 7 Receiving Coil 8 Antenna Coils 51-54 Basic Coils 55-58 Small Loop Coil 71 Signal Detection Area

Claims (2)

An antenna device that is magnetically coupled to a transmission antenna coil means of a non-contact type IC card and is disposed in a reader / writer antenna device that receives a signal transmitted from the non-contact type IC card,
A plurality of basic coils, each including a first small loop coil having a clockwise winding direction and a counterclockwise winding; A plurality of small loop coils classified as a second small loop coil having a direction are arranged in contact with one side so that the winding directions of adjacent small loop coils are opposite to each other. With
The plurality of basic coils are shifted upward with respect to the first basic coil in a plane perpendicular to the magnetic flux generated from the transmitting antenna coil means of the non-contact type IC card. The third basic coil is shifted to the right with respect to the first basic coil, and the fourth basic coil is shifted with respect to the first basic coil in the upward and right directions.
A dead zone generated in a region where the small loop coils of the first basic coil to the fourth basic coil are in contact with each other, and a signal sensing unit which is an internal region of any one of the plurality of basic coils. An antenna device for a reader / writer, wherein the antenna device is stacked.   The reader / writer antenna device according to claim 1, wherein the plurality of basic coils are arranged so as to be shifted from each other by a length that is half the length of the small loop coil.

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