JP2020113141A - RFID system and reader/writer device - Google Patents

Abstract

To make it possible to use an RF tag in the UHF band in a technology that arranges antennas of a reader/writer device in matrix on a two-dimensional plane and recognize where on the two-dimensional plane an RF tag is arranged.SOLUTION: An RFID system 1 comprises: an RF tag 3 that is provided with an antenna 31 for resonance in a loop shape including an impedance adjustment circuit for a dipole antenna for the UHF band; and a reader/writer device 2 that arranges a plurality of booster antennas 201 having the same shape as that of an antenna element of the dipole antenna for the UHF band in matrix on a surface panel 20 while shifting an arrangement angle by 90 degrees in an X-Y direction, and arranges a plurality of reader/writer antennas 210 having the same shape and the same size as those of the booster antennas 201 in matrix on a circuit board 21 such that the reader/writer antennas are aligned in direction with the booster antennas 201 and face the booster antennas 201 in the one-to-one correspondence relationship.SELECTED DRAWING: Figure 1

Description

The present invention relates to the field of RFID (Radio Frequency Identification) for automatically recognizing a person or an object by radio, and more specifically, it is an invention for preventing interference due to multipath in the UHF band.

As a technology related to an RFID system for automatically recognizing a person or an object by radio, antennas of a reader/writer device used for communication with an RF tag are arranged in a matrix on a two-dimensional plane, and where the RF tag is arranged on the two-dimensional plane. A technique for recognizing whether or not there is known (for example, Patent Document 1). Situations to which this technology can be applied include a system that makes it possible to reliably recognize where tools and intermediate products are placed on the work desk in the cell production workplace of a factory, and dolls and cards equipped with RF tags in amusement facilities. A battle game using is conceivable.

Currently, the HF (High Frequency) band (13.56MHz, etc.) and UHF (Ultra High Frequency) band (860-960MHz) are the mainstream frequency bands used in RFID systems, and the UHF band is more costly to manufacture RF tags. It is known that can be made cheap. This is because the price of the IC chip for the UHF band is lower than that of the IC chip for the HF band, and the antenna structure for the UHF band can be made simpler than the antenna structure for the HF band.

Even in the technique of arranging the antennas of the reader/writer device used for communication with the RF tag in a matrix on the two-dimensional plane and recognizing where on the two-dimensional plane the RF tag is arranged, the manufacturing cost becomes low. Although it is desired to use the RF tag, the UHF band RF tag is not suitable for this technology because the RF tag in the UHF band is likely to cause interference due to multipath propagation. In fact, the frequency band in the invention disclosed in Patent Document 1 is the HF band (13.56 MHz), and the antenna of the reader/writer device is a coil antenna.

WO2014/136167

Therefore, the present invention is a technique for arranging the antennas of the reader/writer device used for communication with the RF tag in a matrix on a two-dimensional plane and recognizing where on the two-dimensional plane the RF tag is arranged. The purpose is to enable the use of RF tags.

The present invention relates to an RFID system that uses frequencies in the UHF band, and an RF tag including an inlay that includes at least a loop-shaped resonance antenna including an impedance adjustment circuit for a UHF dipole antenna and an IC chip. , A plurality of booster antennas having the same shape as the linear antenna element of the UHF band dipole antenna are arranged on the front panel in a matrix with the arrangement angles being shifted by 90 degrees in the XY direction. A reader/writer in which a plurality of reader/writer antennas having the same shape and size are arranged on a circuit board in a matrix so as to face the booster antenna in a one-to-one correspondence with the direction of the booster antenna aligned. An RFID system including a device.
In the present invention, it is desirable to set the communication radio wave output of the RF circuit connected to the reader/writer antenna to the minimum output value that enables wireless communication with the RF tag.
Furthermore, the present invention claims a patent right for the reader/writer device that constitutes the RFID system according to the present invention.

In the present invention, in order to prevent interference due to multipath in the UHF band, an RF tag is provided with a resonance antenna of the UHF band dipole antenna, and a booster antenna having the same shape as the linear antenna element of the UHF band dipole antenna is provided. By providing the reader/writer device with the RF tag, the RF tag operates only when the RF tag is placed on the booster antenna. Further, according to the present invention, in order to prevent interference due to multipath in the UHF band, the booster antenna and the reader/writer antenna are arranged in a matrix with the arrangement angles shifted by 90 degrees in the XY directions. Interference between the pair of writer antennas is prevented.

The figure explaining the structure of the RFID system which concerns on this embodiment. The figure explaining the general dipole antenna for UHF bands. FIG. 6 illustrates a structure of an RF tag. FIG. 6 is a diagram illustrating a front panel included in a reader/writer device. FIG. 4 is a diagram illustrating a surface of a circuit board included in a reader/writer device. FIG. 4 is a diagram illustrating a back surface of a circuit board included in the reader/writer device. FIG. 6 illustrates a state in which an RF tag is placed in a reader/writer device. The figure explaining the overlapping state of the antenna when an RF tag is put on the card reading part. B-B' sectional drawing.

From here, the embodiment concerning the present invention is described. This embodiment is for facilitating the understanding of the present invention, and the present invention is not limited to this embodiment. Further, the drawings are schematic diagrams drawn to facilitate understanding of the present invention, unless otherwise specified.

FIG. 1 is a diagram illustrating a configuration of an RFID system 1 according to this embodiment. The RFID system 1 according to the present embodiment is a reader that wirelessly communicates with the RF tag 3 that is a non-contact data carrier used in the RFID system 1 according to the present embodiment and a frequency in the UHF band. A writer device 2 is included.

As shown in FIG. 1, on the front panel 20 of the reader/writer device 2, card reading units 200 for designating a position to place the RF tag 3 are provided in a matrix form (here, 3 rows and 3 columns). Inside the 200, a booster antenna 201 using a metal plate (including metal foil) is provided. The shape of the booster antenna 201 provided inside the card reading unit 200 is a linear shape, and the plurality of booster antennas 201 are arranged in a matrix with the arrangement angle shifted by 90 degrees in the XY directions.

A circuit board 21 is mounted on the inner side of the reader/writer device 2, that is, on the lower side of the surface panel 20, and the surface and the shape of the booster antenna 201 are the same as those of the booster antenna 201. A plurality of reader/writer antennas 210 (including metal foil) are arranged in a matrix so that they are aligned with the booster antenna 201 and face the booster antenna 201 in a one-to-one correspondence.

The booster antenna 201 is an antenna that uses a booster method, which is a well-known technique in the RFID field that uses the UHF band. The booster method is, for example, as described in JP-A-2013-46326, the communication distance of the resonance antenna 31 having a small size and the inlay 30 including the IC chip 32 connected thereto is smaller than that of the resonance antenna 31. This is a method of extending by using a booster antenna 201 having a large size.

In a general booster method, both the inlay 30 having the resonance antenna 31 and the booster antenna 201 are mounted on the RF tag 3, but in the present embodiment, only the inlay 30 having the resonance antenna 31 is mounted on the RF tag 3. The booster antenna 201 is provided in the card reading unit 200 of the reader/writer device 2. By doing so, by placing the RF tag 3 on the upper side of the booster antenna 201 arranged in the card reading unit 200 of the reader/writer device 2, the resonance antenna 31 and the booster antenna 201 are electrically coupled to each other and the RF tag 3 is used. Tag 3 works.

FIG. 2 is a diagram illustrating a general UHF band dipole antenna 4. FIG. 2A shows the structure of a general UHF band dipole antenna 4. In a general UHF band dipole antenna 4, a linear antenna element 40 used for supplying electric power and transmitting/receiving radio waves, and an impedance adjusting circuit 41 having an inductance used for adjusting resonance frequency are connected to the antenna element 40. The IC chip 32 has a structure and is connected to the impedance adjustment circuit 41.

The general UHF band dipole antenna 4 shown in FIG. 2A can be divided into two parts as shown in FIG. 2B according to its function. One is a linear antenna element 40 used for power supply and radio wave transmission/reception, and the other is an impedance adjustment circuit 41 having an inductance used for resonance frequency adjustment. In this embodiment, the antenna element 40 used for power supply and radio wave transmission/reception is used for the booster antenna 201, and the impedance adjustment circuit 41 having the inductance used for resonance frequency adjustment and connected to the IC chip 32 is inlaid. Use for 30.

FIG. 3 is a diagram illustrating the configuration of the RF tag 3 according to this embodiment. As illustrated in FIG. 3, an inlay 30 is mounted inside the center of the RF tag 3. The inlay 30 has a resonance antenna 31 having an inductance used for adjusting the resonance frequency and an IC chip 32 connected to the resonance antenna 31. The shape of the resonance antenna 31 included in the inlay 30 is a loop shape including an impedance adjustment circuit 41. It has become. The resonance antenna 31 included in the inlay 30 can be formed by etching using a metal foil such as copper foil or aluminum foil, or printing using a conductive pace.

The shape of the resonance antenna 31 included in the inlay 30 is a loop including the impedance adjusting circuit 41. The orientation of the RF tag 3 when placed in the card reading unit 200 and the RF tag 3 having the inlay 30 placed therein are placed. This is because the relative angle between the resonance antenna 31 and the booster antenna 201 changes depending on the card reading unit 200. For example, the angle of the booster antenna 201 is deviated by 90 degrees between the card reading unit 200 with the symbol "a" and the card reading unit 200 with the symbol "b" on the right side thereof.

By forming the resonance antenna 31 in a loop shape including the impedance adjustment circuit 41, the orientation of the RF tag 3 when placed on the card reading unit 200 and the card reading unit 200 on which the RF tag 3 having the inlay 30 is placed can be provided. Instead, by placing it on the upper side of the booster antenna 201 arranged in the card reading unit 200, the resonance antenna 31 and the booster antenna 201 can form the general shape of the dipole antenna 4 for the UHF band.

FIG. 4 is a diagram illustrating the front panel 20 of the reader/writer device 2 according to the present embodiment. As shown in FIG. 1 and FIG. 4, on the front panel 20 of the reader/writer device 2, card reading units 200 for designating a position where the RF tag 3 is placed are provided in a matrix, and one card reading unit 200 is provided. , A linear booster antenna 201 that is electrically coupled to the inlay 30 mounted on the RF tag 3 is provided.

The booster antenna 201 overlaps with the resonance antenna 31 of the RF tag 3 placed on the upper side of the booster antenna 201, and forms the shape of the general UHF band dipole antenna 4 shown in FIG. 2A. By forming the shape of the general UHF band dipole antenna 4 by the resonance antenna 31 and the booster antenna 201, the RF tag 3 is in a state of operating normally only when placed on the upper side of the booster antenna 201. It is possible to prevent interference due to multipath in the UHF band.

Since the RF tag 3 is in a state of operating normally only when placed on the upper side of the booster antenna 201, the card reading unit 200 needs a device for designating the position where the RF tag 3 is placed. .. This device can be realized by a printed pattern, but can also be realized by a concave portion that regulates the position where the RF tag 3 is placed.

The booster antenna 201 can be provided on the front surface of the front panel 20 or the back surface of the front panel 20, but in the present embodiment, as shown in the AA′ sectional view of FIG. The booster antenna 201 is provided, and the protective film 20a that covers the booster antenna 201 is attached by the adhesive layer 20b. This is a device for protecting the booster antenna 201 and shortening the distance between the RF tag 3 placed on the card reading unit 200 and the booster antenna 201.

In the present embodiment, the plurality of booster antennas 201 are arranged in a matrix with the arrangement angle being shifted by 90 degrees in the XY direction, because the booster antennas 201 adjacent in the XY direction interfere with each other. This is to prevent interference due to multipath in the UHF band.

The shape of the booster antenna 201 is linear because the booster antenna 201 has directivity. By making the shape of the booster antenna 201 linear and giving the booster antenna 201 directivity and shifting the arrangement angle of the booster antennas 201 adjacent in the XY direction by 90 degrees, the booster antennas 201 adjacent in the XY direction are shifted. Do not interfere with each other.

FIG. 5 is a diagram illustrating the front surface of the circuit board 21 of the reader/writer device 2, and FIG. 6 is a diagram illustrating the back surface of the circuit board 21 of the reader/writer device 2.

Since the booster antenna 201 mounted on the front panel 20 of the reader/writer device 2 becomes an antenna that electrically functions with the resonance antenna 31 of the inlay 30 mounted on the RF tag 3, the circuit included in the reader/writer device 2 A reader/writer antenna 210 for wirelessly communicating with the inlay 30 mounted on the RF tag 3 using the booster antenna 201 is mounted on the surface of the substrate 21.

The reader/writer antenna 210 has the same shape and size as the booster antenna 201, and the plurality of reader/writer antennas 210 are aligned with the booster antenna 201 in a one-to-one correspondence relationship with the booster antenna 201. They are arranged in a matrix so as to face each other. By arranging the reader/writer antennas 210 in this way, like the booster antennas 201, the reader/writer antennas 210 adjacent in the XY direction do not interfere with each other, and interference due to multipath in the UHF band can be prevented.

Further, by making the reader/writer antenna 210 and the booster antenna 201 face each other, it is possible to reduce the minimum output value of the communication radio wave output that enables wireless communication with the RF tag 3 placed above the booster antenna 201. By setting the communication radio wave output of the reader/writer device 2 to the minimum output value that enables wireless communication with the RF tag 3 placed in the card reading unit 200, the reader/writer device 2 is set to the RF placed on the front panel 20. Interference due to multipath in the UHF band can be reliably prevented without detecting anything other than the tag 3.

The shorter the interval between the booster antenna 201 and the reader/writer antenna 210 is, the shorter the condition is that the booster antenna 201 and the reader/writer antenna 210 do not come into physical contact with each other. Can be prevented more reliably. Further, if the outer casing of the reader/writer device 2 is made of a radio wave shielding material such as metal, the effect of preventing interference due to multipath in the UHF band can be further enhanced.

As shown in FIG. 6, the RF tag 3 placed on the front panel 20 of the reader/writer device 2 and the inlay 30 are provided on the back surface of the circuit board 21 of the reader/writer device 2 so that the position of the RF tag 3 can be recognized. A pair of an RF circuit 211 that is an electric circuit that controls wireless communication and a control circuit 212 that is an electric circuit that controls the operation of the reader/writer device 2 is mounted for each reader/writer antenna 210 arranged on the surface of the circuit board 21. ing. Each reader/writer antenna 210 arranged on the surface of the circuit board 21 is connected to an RF circuit 211 corresponding to the reader/writer antenna 210. Further, each of the control circuits 212 is connected to the output port 213 provided in the reader/writer device 2. The control circuit 212 outputs the data read from the RF tag 3 to the host system via the output port 213, and the host system uses the control circuit 212 that reads the data from the RF tag 3 to display the front panel 20 of the reader/writer device 2. The RF tag 3 and its position in can be recognized.

In order to recognize the RF tag 3 placed on the front panel 20 of the reader/writer device 2 and its position, the RF circuit 211 and the control circuit 212 mounted on the circuit board 21 of the reader/writer device 2 are integrated into one, A switching circuit connected to each reader/writer antenna 210 may be provided, and the switching circuit may be used to switch the reader/writer antenna 210 connected to the RF circuit 211.

FIG. 7 is a diagram illustrating a state in which the RF tag 3 is placed on the reader/writer device 2. In FIG. 7, three RF tags 3 are placed on the front panel 20 of the reader/writer device. The first RF tag 3 is placed on the card reading unit 200 with the symbol "a", and the second RF tag 3 is the card reading unit 200 with the symbol "f". , And the third RF tag 3 is placed on the card reading unit 200 marked with "g".

FIG. 8 is a diagram illustrating an overlapping state of antennas when the RF tag 3 is placed on the card reading unit 200 of the reader/writer device 2. In FIG. 8, elements other than the antenna (for example, the front panel 20 of the reader/writer device 2) are not shown.

In FIG. 8A, the overlapping state of the antennas in the RF tag 3 placed on the card reading unit 200 with the symbol “a” is illustrated, and in FIG. 8B, the symbol “f” is shown. The overlapping state of the antennas in the RF tag 3 placed on the card reading unit 200 marked with is shown, and in FIG. 8(c), on the card reading unit 200 marked with "g". The overlapping state of the antennas in the RF tag 3 placed in FIG.

As illustrated in FIGS. 8A to 8C, with the RF tag 3 placed on the card reading unit 200, the resonance antenna 31 of the inlay 30 and the booster antenna are sequentially arranged from the front side of the reader/writer device 2. 201 and the reader/writer antenna 210 are laminated in order. The arrangement angle of the booster antenna 201 is different between FIGS. 8A and 8B, and the orientation of the resonance antenna 31 is different between FIGS. 8A and 8C, but FIG. In any of the cases from (c) to (c), the resonance antenna 31 and the booster antenna 201 can form the general shape of the UHF band dipole antenna 4.

FIG. 9 is a sectional view taken along the line B-B′ in FIG. In the present embodiment, as shown in FIG. 9, between the resonance antenna 31 mounted on the RF tag 3 and the booster antenna 201 mounted on the reader/writer device 2, the protective film 20a and the base of the RF tag 3 are provided. There is wood. By selecting a material having a high relative permittivity as the material of the material existing between the resonance antenna 31 and the booster antenna 201, the resonance antenna 31 and the booster antenna 201 are electrically coupled to each other and the resonance antenna 31 and the booster antenna 201 are electrically connected as shown in FIG. It functions as the illustrated general UHF band dipole antenna 4.

On the other hand, the surface panel 20 and the air layer are present between the booster antenna 201 mounted on the reader/writer device 2 and the reader/writer antenna 210 mounted on the reader/writer device 2. Since the relative permittivity of the air layer is low, the booster antenna 201 and the reader/writer antenna 210 are not electrically coupled to each other, and electric power supply and wireless communication by the radio wave method are possible between the booster antenna 201 and the reader/writer antenna 210. Due to the above-mentioned reasons, interference due to multipath in the UHF band is prevented.

1 RFID System 2 Reader/Writer Device 20 Surface Panel 200 Card Reader 201 Booster Antenna 21 Circuit Board 210 Reader/Writer Antenna 211 RF Circuit 3 RF Tag 30 Inlay 31 Resonant Antenna 32 IC Chip

Claims (3)

An RF tag having an inlay at least composed of a loop-shaped resonance antenna including an impedance adjusting circuit for a UHF band dipole antenna, and an IC chip,
A plurality of booster antennas, which have the same shape as the linear antenna element of the UHF band dipole antenna, are arranged on the front panel in a matrix with the arrangement angle shifted by 90 degrees in the XY direction. A reader/writer device in which a plurality of reader/writer antennas having the same shape and the same size are arranged on a circuit board in a matrix form so as to be aligned with the booster antenna and face the booster antenna in a one-to-one correspondence relationship. And an RFID system including. The RFID system according to claim 1, wherein a communication radio wave output of an RF circuit connected to the reader/writer antenna is set to a minimum output value that enables wireless communication with the RF tag. A reader/writer device constituting the RFID system according to claim 1.