JP4700831B2 - RFID tag communication distance expansion method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for arbitrarily extending the communication distance of an RFID tag that performs communication with electromagnetic waves using an antenna coil.
[0002]
[Prior art]
Conventionally, an RFID tag (Radio Frequency IDentification TAG) is classified into an electromagnetic induction type and an electromagnetic coupling type, and both communicate with a reader / writer machine or the like using electromagnetic waves.
[0003]
The RFID tag has an antenna coil and a control unit. When the antenna coil receives a transmission signal from a reader / writer machine, the control unit accumulates it in a capacitor as power, and stores the power in the storage unit. The information such as the ID code is transmitted from the antenna coil to the reader / writer again.
[0004]
As a transmission / reception method, there are an ASK (Amplitude Shift Keying) method and an FSK (Frequency Shift Keying) method. The former performs transmission / reception by intensity modulation of electromagnetic waves, and the latter performs transmission / reception by frequency modulation of electromagnetic waves.
[0005]
When a general RFID tag is divided into antenna coil types, a concentric disk-shaped antenna coil using a circular air-core coil and a cylindrical antenna coil in which an insulating copper wire such as an enameled wire is wound around a rod-shaped ferrite core. There are two types, and the outer shape is formed in a disk shape corresponding to the shape of each antenna coil, and the latter is formed in a bar shape.
[0006]
An RFID tag having a concentric disk-shaped antenna coil performs communication using the magnetic flux change in the surface direction of the circular coil, and an RFID tag having a cylindrical antenna coil communicates using the magnetic flux change in the axial direction. To do.
[0007]
[Problems to be solved by the invention]
However, the communicable distance of the RFID tag is generally several millimeters to several centimeters. For example, when reading information stored in the RFID tag with a small reader / writer, the reader / writer can communicate with the RFID tag. It is necessary to approach the distance, that is, several mm to several cm, and it is impossible to read from a position separated by several m to several tens m. Therefore, the field of use of RFID tags has been limited.
[0008]
The present invention solves the above-mentioned problems, and an object of the present invention is to provide an RFID tag communication distance expansion method capable of extending the communication range of the RFID tag and expanding the field of use of the RFID tag. It is something to be done.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the RFID tag communication distance expansion method according to the present invention is a method of arbitrarily expanding the communication distance of an RFID tag having an antenna coil, and a loop antenna having an arbitrary length can be attached and detached in series. An induction coil that can be connected to the RFID tag, and a mounting portion to which the RFID tag can be detachably mounted, and the induction coil is placed close to the antenna coil of the RFID tag mounted on the mounting portion. The RFID tag is attached to the attachment portion of the electromagnetic coupler, and a loop antenna having an arbitrary length is attached to the induction coil of the electromagnetic coupler. By connecting in series and communicating between the RFID tag and the reader / writer using the loop antenna, the communication distance of the RFID tag can be arbitrarily set. And wherein the large to Rukoto.
[0010]
Since the present invention is configured as described above, a loop antenna can be electromagnetically coupled to the RFID tag via an electromagnetic coupler, and the communicable distance of the RFID tag can be arbitrarily increased by the action of the loop antenna.
[0011]
That is, the connection end of the induction coil provided in the electromagnetic coupler body and the connection end of the loop antenna are connected in series, the RFID tag is attached to the attachment portion, and the RFID tag antenna coil is brought close to the induction coil. By arranging and electromagnetically coupling, the RFID tag antenna coil and the loop antenna can be electromagnetically coupled via the induction coil, and the communicable distance of the RFID tag can be arbitrarily expanded by the action of the loop antenna. is there.
[0012]
First, when reading the unique information stored in the RFID tag from an external reader / writer machine or the like, the information is transmitted from the antenna coil of the RFID tag to the induction coil as a magnetic flux change.
[0013]
Then, a current corresponding to the change in magnetic flux flows through the induction coil, and the current also flows through the loop antenna that forms a series circuit with the current, and the magnetic flux changes over the entire circumference of the loop antenna. Therefore, information can be read out from all directions outside the loop antenna by a reader / writer machine or the like.
[0014]
Conversely, when transmitting power or information from a reader / writer machine or the like to an RFID tag, the loop antenna first captures the magnetic flux change caused by the signal transmitted from the antenna of the reader / writer machine, etc., thereby causing a current to flow to the loop antenna. The induction coil amplifies it in the form of magnetic flux (amplification by the number of turns), and the antenna coil of the RFID tag captures the change in the amplified magnetic flux.
[0015]
As described above, since communication is possible from all directions of the loop antenna, the communicable distance of the RFID tag can be arbitrarily extended and expanded according to the size and shape of the loop antenna with a simple structure and at low cost.
[0016]
In addition, a commercially available RFID tag can be used as it is. In addition, simply mounting an RFID tag on the mounting part of the electromagnetic coupler makes it possible to stably electromagnetically couple the antenna coil and the loop antenna, thus simplifying the construction and enabling stable operation for a long time. .
[0017]
In addition, management, storage, transportation, and construction can be facilitated by previously mounting the RFID tag on the mounting portion of the electromagnetic coupler.
[0018]
Furthermore, a loop antenna can be connected to the electromagnetic coupler in advance, and the electromagnetic coupler, the RFID tag, and the loop antenna can be unitized, thereby further simplifying management, storage, transportation, and construction.
[0019]
In addition, when the antenna coil of the RFID tag is formed in a cylinder shape or a concentric disk shape, a commercially available RFID tag can be used, so that it can be easily obtained and the cost can be reduced by mass production.
[0020]
Further, when the loop antenna is fixed to a sheet-like elongated base material, the loop antenna fixed to the sheet-like base material can be easily formed into a specific shape, so that installation or installation is possible. Easy to do.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the RFID tag communication distance extending method according to the present invention will be specifically described with reference to the drawings. FIG. 1 is an explanatory cross-sectional view showing an R FID tag structure applied to an RFID tag having a concentric disk-shaped antenna coil, and FIG. 2 shows a configuration of an electromagnetic coupler applied to the RFID tag having a concentric disk-shaped antenna coil. It is a perspective view.
[0022]
FIG. 3A is a plan view showing a configuration of an RFID tag having a concentric disk-shaped antenna coil, and FIG. 3B is a schematic diagram showing a state of a magnetic field generated in the RFID tag having a concentric disk-shaped antenna coil. FIG. 4 is a block diagram showing the configuration of the RFID tag control system.
[0023]
5A and 5B are a cross-sectional explanatory view and a plane explanatory view showing an R FID tag structure applied to an RFID tag having a cylindrical antenna coil, and FIG. 6 shows an RFID tag having a cylindrical antenna coil. FIG. 7 is a schematic diagram showing a configuration of an RFID tag having a cylindrical antenna coil and a state of a magnetic field generated in the RFID tag having a cylindrical antenna coil.
[0024]
FIG. 8A shows an RFID tag structure in which a loop antenna is fixed to a sheet-like base material and an RFID tag is mounted on an electromagnetic coupler attached to the sheet-like base material. It is a side view which shows the state before the use turned.
[0025]
8 (b) and 8 (c) are a side view and a plan view showing a state in which the sheet-like substrate of FIG. 8 (a) is extended in use, and FIG. 9 is an array of a plurality of RFID tag structures shown in FIG. It is a schematic plan view showing an example in which guide rails such as unmanned vehicles and traveling robots are formed.
[0026]
First, with reference to FIGS. 1 to 4, a configuration when an RFID tag 1 a having a concentric disc-shaped antenna coil 2 a is employed as an example of the RFID tag communication distance extending method according to the present invention will be described.
[0027]
The RFID tags 1a and 1b suitably employed in the present embodiment are electromagnetic coupling type and electromagnetic induction type RFID tags. In the present embodiment, an embodiment in which an electromagnetic induction type RFID tag is used will be described below. Explained.
[0028]
In FIG. 1, an electromagnetic coupler 5 is an RFID having a resin-made main body having electrical insulation, a guiding coil 6 formed of a circular air-core coil embedded in the main body, and a concentric disk-shaped antenna coil 2a. A mounting portion 5a for mounting the tag 1a and electromagnetically coupling the antenna coil 2a and the induction coil 6 by placing them close to each other is provided.
[0029]
The mounting portion 5a is formed of a shallow groove having a circular cross section so as to conform to the outer shape of the RFID tag 1a, and an induction coil 6 is disposed below the mounting portion 5a. The induction coil 6 is molded with resin and built in the electromagnetic coupler 5. The RFID tag 1a is bonded and fixed to the mounting portion 5a with an adhesive 11 or the like, and is stably mounted.
[0030]
The connection ends 6a and 6b of the induction coil 6 embedded in the electromagnetic coupler 5 are electrically connected to a conductive screw type receptacle 5b provided exposed on the surface side of the electromagnetic coupler 5. In addition, a conductive screw-type plug 5c can be screwed into the receptacle 5b.
[0031]
Reference numeral 7 denotes a loop antenna. A connection terminal 7 c is electrically connected to connection ends 7 a and 7 b of the loop antenna 7. The induction coil 6 and the loop antenna 7 are connected as a series circuit via the connection terminal 7c, the plug 5c and the receptacle 5b by screwing and fastening the plug 5c to the receptacle 5b with the connection terminal 7c interposed. The
[0032]
Thereby, the loop antenna 7 and the antenna coil 2a of the RFID tag 1a can be electromagnetically coupled via the induction coil 6 of the electromagnetic coupler 5.
[0033]
The loop antenna 7 can be laid in an arbitrary closed area and shape depending on the target communication area. If the length (loop) of the loop antenna 7 is extended, the communication area is expanded accordingly, but the communication sensitivity tends to decrease in inverse proportion to the area. On the other hand, if the communication sensitivity of the RFID tags 1a and 1b and the reader / writer is high, the communication area can be expanded accordingly.
[0034]
For example, in the case of the RFID tag 1a having the concentric disk-shaped antenna coil 2a having an outer diameter of 50 mm, the maximum communication distance can be expanded to about 10 m to 20 m when the loop antenna 7 is formed into an elongated loop shape according to experiments. It has been found.
[0035]
In the present embodiment, the electrical connection between the connection ends 6a and 6b of the induction coil 6 and the connection ends 7a and 7b of the loop antenna 7 is made with a conductive screw-type plug 5c via a connection terminal 7c. Although it is configured to be detachable by screwing with the receptacle 5b, it may be electrically connected by soldering.
[0036]
The RFID tag structure shown in FIG. 1 is an example of communication using electromagnetic waves using a concentric disk-shaped antenna coil 2a of the RFID tag 1a. As shown in FIG. 3A, a concentric disk-shaped structure is used. The antenna coil 2a and the semiconductor IC chip 4 serving as a control unit are directly connected without using a printed circuit board or the like, thereby realizing downsizing of the RFID tag 1a.
[0037]
The semiconductor IC chip 4 is formed by integrally packaging an IC (semiconductor integrated circuit) chip, an LSI (semiconductor large-scale integrated circuit) chip or the like. As shown, a CPU 4a serving as a control unit, a memory 4b serving as a storage unit, a transceiver 4c, and a capacitor 4d serving as a power storage unit are provided.
[0038]
A signal transmitted from an unillustrated external reader / writer device or the like is transmitted to the CPU 4a via the transceiver 4c, and the electric power is stored in the capacitor 4d. The capacitor 4d serving as the power storage means may be omitted, and power may be continuously supplied to the semiconductor IC chip 4 from an external reader / writer machine or the like.
[0039]
The CPU 4a is a central processing unit, and reads programs and various data stored in the memory 4b, performs necessary calculations and determinations, and performs various controls.
[0040]
The memory 4b stores various programs for operating the CPU 4a and various unique information when the electromagnetic induction tag 1a is installed for various purposes.
[0041]
Further, as an example of the concentric disk-shaped antenna coil 2a shown in FIG. 3, a copper wire having a diameter of about 30 μm is wound in a concentric disk shape with multiple layers in the radial direction by single wire winding, and the antenna coil 2a The inductance was about 9.5 mH (frequency 125 kHz), and the capacitance of a capacitor separately connected to the antenna coil 2a for resonance was about 170 pF (frequency 125 kHz). FIG. 3B shows a magnetic field H generated in the RFID tag 1a.
[0042]
The RFID tag 1a of the present embodiment uses a radio communication system of amplitude shift keying (ASK) with a radio frequency of one wave, has a wide resonance frequency band, and a hollow antenna coil with a wire diameter of several tens of microns. The RFID tag 1a using a CMOS-IC with very little power consumption and incorporating a special transmission / reception circuit 2a is adopted.
[0043]
In an RFID tag, an alternating magnetic field transmitted from an external reader / writer machine or the like is received by a resonance frequency of an antenna coil built in the RFID tag. At that time, the conventional RFID tag uses frequency shift keying (FSK) to increase the communication distance, and the radio frequency uses, for example, two waves of 125 kHz and 117 kHz, and the received power is increased. For this reason, a method of extending the communication distance by using a ferrite core for the antenna coil and increasing the coil diameter to make a plurality of windings has been common.
[0044]
In the frequency shift keying (FSK) method using two radio frequencies, when a conductive member such as a metal or magnetic material approaches, the reception frequency shifts and the received power decreases and a communication error occurs and communication becomes impossible. Because the distance is extremely reduced and it becomes practically unusable, the fixed idea that RFID tags cannot be used attached to conductive members such as metals and magnetic materials was dominant. .
[0045]
Recently, however, the radio frequency uses a single-wave amplitude shift keying (ASK) radio communication system, and is a consumption that incorporates a special transmission / reception circuit with an air-core antenna coil having a wide resonance frequency band and a wire diameter of several tens of microns. An RFID tag that can be used by attaching to a conductive member such as a metal or a magnetic material using a CMOS-IC with very little electric power has been proposed and is widely available on the market.
[0046]
Next, the configuration when the RFID tag 1b having the cylindrical antenna coil 2b is adopted as an example of the RFID tag communication distance extending method according to the present invention will be described with reference to FIGS.
[0047]
FIG. 5 shows an RFID tag structure using a rod-shaped RFID tag 1b having a cylindrical antenna coil 2b. In FIG. 5, the induction coil 6 built in the electromagnetic coupler 5 is formed in an air cylinder shape, and the mounting portion 5a of the rod-shaped RFID tag 1b is formed in a circular cross section formed inside the induction coil 6. It is constituted by an elongated insertion hole. The induction coil 6 is molded with resin and built in the electromagnetic coupler 5.
[0048]
The rod-shaped RFID tag 1b is inserted into the mounting portion 5a formed of an elongated insertion hole having a circular cross section, and is fixedly adhered and fixed with an adhesive or the like, and is stably mounted.
[0049]
The connection ends 6a and 6b of the induction coil 6 embedded in the electromagnetic coupler 5 are electrically connected to a conductive screw type receptacle 5b provided exposed on the surface side of the electromagnetic coupler 5. In addition, a conductive screw-type plug 5c can be screwed into the receptacle 5b.
[0050]
On the other hand, a connection terminal 7 c is electrically connected to the connection ends 7 a and 7 b of the loop antenna 7. The induction coil 6 and the loop antenna 7 are connected as a series circuit via the connection terminal 7c, the plug 5c and the receptacle 5b by screwing and fastening the plug 5c to the receptacle 5b with the connection terminal 7c interposed. The
[0051]
Thereby, the loop antenna 7 and the antenna coil 2b of the RFID tag 1b can be electromagnetically coupled via the induction coil 6 of the electromagnetic coupler 5.
[0052]
As shown in FIG. 7, a cylindrical core member 3 such as an iron core or ferrite is inserted in the axial direction (left-right direction in FIG. 7) inside an antenna coil 2b formed in a cylindrical shape by winding a single wire. Reference numeral 8 denotes a glass container serving as an exterior of the RFID tag 1b.
[0053]
For example, as an example of the antenna coil 2b, a state in which a copper wire having a diameter of about 30 μm is wound in a single-winding wire in a radial direction with multiple layers in a cylindrical shape in the axial direction and the core member 3 is inside the antenna coil 2b In this case, the inductance was about 9.5 mH (frequency 125 kHz), and the capacitance of the capacitor separately connected to the antenna coil 2a for resonance was about 170 pF (frequency 125 kHz). Other configurations are the same as those of the above-described embodiment, and the same effects can be obtained.
[0054]
FIG. 8 shows another embodiment of the R FID tag structure. In the present embodiment, the loop antenna 7 is fixed to the sheet-like base material 9, and the electromagnetic coupler 5 is fixed to the sheet-like base material 9 by adhesion or the like, and the connection ends 7a and 7b of the loop antenna 7 are electromagnetically connected. The connector 5 is electrically connected to the connection ends 6a and 6b of the induction coil 6 by the plug 5c, and the RFID tags 1a and 1b are appropriately fixed to the mounting portion 5a of the electromagnetic coupler 5.
[0055]
As the loop antenna 7, for example, a 0.3 mm copper wire is laminated and fixed on a base material 9 made of a soft plastic sheet such as vinyl chloride resin, polyethylene, or polypropylene can be used.
[0056]
In the present embodiment, as shown in FIG. 8, an example in which the sheet-like base material 9 is formed in an elongated shape will be described. However, the loop antenna 7 is attached to the sheet-like base material 9 having various shapes such as a square shape and a circular shape. It may be configured to be fixed in a desired loop shape. Further, a protective film may be further formed on the surface side of the loop antenna 7.
[0057]
In this embodiment, the fixing screw holes 9a are formed at the four corners of the sheet-like base material 9, but an adhesive layer and a release layer are laminated on the back side of the sheet-like base material 9. When the sheet-like base material 9 formed and fixed with the loop antenna 7 is installed at a target location, the release layer may be removed to expose the adhesive layer, and the adhesive layer may be bonded and fixed.
[0058]
FIG. 9 shows an example in which a plurality of RFID tag structures shown in FIG. 8 are arranged in series to form a guide rail for traveling such as an unmanned vehicle or a traveling robot 10. The unmanned vehicle and the traveling robot 10 are equipped with a reader machine 12 for reading information on the RFID tags 1a and 1b and a microcomputer (microcomputer). The position information stored in each of the RFID tags 1a and 1b is read, The vehicle can be controlled to run automatically according to preprogrammed conditions or to stop automatically at a predetermined position.
[0059]
Another application example is an anti-theft system. For example, a loop antenna 7 is stretched around a room, a reader 12 that reads information on the RFID tags 1a and 1b is attached to the product, and the reader 12 is connected to the RFID tags 1a and 1b when the product is taken out of the room. It can also be configured to issue an alarm by disconnecting the communication.
[0060]
【The invention's effect】
Since the present invention has the configuration and operation as described above, the communicable distance of the RFID tag can be arbitrarily extended and expanded according to the size and shape of the loop antenna with a simple structure and at a low cost. The field of use of tags can be expanded.
[0061]
That is, a loop antenna capable of communication from all directions is electromagnetically coupled to the RFID tag via an electromagnetic coupler, and the communicable distance of the RFID tag can be arbitrarily increased by the action of the loop antenna.
[0062]
In addition, a commercially available RFID tag can be used as it is, and the antenna coil and loop antenna can be stably electromagnetically coupled simply by mounting the RFID tag on the mounting portion of the electromagnetic coupler. Because it is possible, the construction is easy and it can be operated stably for a long time.
[0063]
In addition, management, storage, transportation, and construction can be facilitated by previously mounting the RFID tag on the mounting portion of the electromagnetic coupler.
[0064]
Furthermore, a loop antenna can be connected to the electromagnetic coupler in advance, and the electromagnetic coupler, the RFID tag, and the loop antenna can be unitized, thereby further simplifying management, storage, transportation, and construction.
[0065]
In addition, when the antenna coil is formed in a cylinder shape or a concentric disk shape, a commercially available RFID tag can be used, so that it is easy to obtain and the cost can be reduced by mass production.
[0066]
Further, when the loop antenna is fixed to the sheet-like base material, the loop antenna fixed to the sheet-like base material can be easily formed in a specific shape, so that installation or laying can be easily performed.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view showing an R FID tag structure applied to an RFID tag having a concentric disk-shaped antenna coil.
FIG. 2 is a perspective view showing a configuration of an electromagnetic coupler applied to an RFID tag having a concentric disk-shaped antenna coil.
3A is a plan view showing a configuration of an RFID tag having a concentric disk-shaped antenna coil, and FIG. 3B is a schematic diagram showing a state of a magnetic field generated in the RFID tag having a concentric disk-shaped antenna coil. is there.
FIG. 4 is a block diagram showing a configuration of a control system of the RFID tag.
5A and 5B are a cross-sectional explanatory view and a plane explanatory view showing an R FID tag structure applied to an RFID tag having a cylindrical antenna coil.
FIG. 6 is a perspective explanatory view showing a configuration of an electromagnetic coupler applied to an RFID tag having a cylindrical antenna coil.
FIG. 7 is a schematic diagram showing a configuration of an RFID tag having a cylindrical antenna coil and a state of a magnetic field generated in the RFID tag.
FIG. 8A is a sheet-like substrate in an RFID tag structure in which a loop antenna is fixed to a sheet-like substrate, and an RFID tag is mounted on an electromagnetic coupler attached to the sheet-like substrate. FIG. 9B is a side view showing a state before use in which the sheet is wound, and FIGS. 9B and 9C are a side view and a plan view showing a state in which the sheet-like substrate of FIG.
9 is a schematic plan view showing an example in which a plurality of RFID tag structures shown in FIG. 8 are arranged in series to form a guide rail such as an unmanned vehicle or a traveling robot.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a, 1b ... RFID tag 2a, 2b ... Antenna coil 3 ... Core member 4 ... Semiconductor IC chip 4a ... CPU
4b ... Memory 4c ... Transceiver 4d ... Capacitor 5 ... Electromagnetic coupler 5a ... Mounting part 5b ... Receptacle 5c ... Plug 6 ... Inductive coil 6a, 6b ... Connection end 7 ... Loop antenna 7a, 7b ... Connection end 7c ... Connection terminal 8 ... Glass container 9 ... Sheet-like base material 9a ... Screw hole
10 ... Unmanned vehicles and traveling robots
11… Adhesive
12 ... Reader machine

Claims (2)

In a method of arbitrarily expanding the communication distance of an RFID tag having an antenna coil ,
An induction coil capable of detachably connecting a loop antenna of an arbitrary length in series and a mounting portion capable of detachably mounting the RFID tag, wherein the induction coil is mounted on the mounting portion Using an electromagnetic coupler configured so that the antenna coil of the RFID tag is placed close to and electromagnetically coupled between the two ,
The RFID tag is attached to the attachment portion of the electromagnetic coupler, a loop antenna having an arbitrary length is connected in series to the induction coil of the electromagnetic coupler, and the RFID tag and the reader are utilized using the loop antenna. A communication distance expansion method for an RFID tag, wherein the communication distance of the RFID tag is arbitrarily increased by communicating with a writer . 2. The RFID tag communication distance extending method according to claim 1, wherein the loop antenna is fixed to a sheet-like elongated base material.

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