JP2005301443A - Rfid tag and circuit constant adjusting method for rfid tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily adjusting the circuit constants of the impedance matching circuit of an RFID tag attached to or embedded in the surfaces of products whose dielectric constants are different or products whose dielectric's thickness is different, and an RFID tag for adjusting the circuit constants. <P>SOLUTION: This RFID tag 10 is provided with an impedance matching circuit 15 equipped with a plurality of circuit elements M1 to M5 connected to antennas 17a and 17b in parallel, a circuit 18 for burning-off for burning off a specific circuit element M2 and a switch 19 for burning-off to be connected to the impedance matching circuit 15 in a normal voltage, and to be connected to the circuit 18 for burning-off when a higher voltage than the operating voltage of the RFID tag 10 is applied. An AC signal obtained by biasing a DC voltage from a tuning device 20 is made to flow through the circuit 18 for burning-off, and a portion of the circuit pattern of the circuit element M2 is burnt off, and the circuit element M2 is fixed to the antennas 17a and 17b in a non-connections state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for adjusting circuit constants of an RFID tag, and more particularly, to a method of adjusting circuit constants of an RFID tag that requires impedance matching for each product to be attached such as a tire.

In recent years, RFID tags have been written on tires with information on the tire, such as the company name, product name, serial number, tire structure symbol, cross-sectional width, rim diameter, flatness, etc. It is considered to be worn. This RFID tag is used in, for example, an RFID system installed in a conveying device such as a conveyor that moves a product. As shown in FIG. 5, the RFID tag is installed in the vicinity of a conveying device 51 that conveys a product 50. The product is identified by communicating with a battery-less wireless tag (RFID tag) 53 attached to the product 50 by an interrogator (reader) 52a and an antenna 52b provided in the main body 52 of the system. The RFID tag 53 includes an antenna and an IC chip having a communication function that is operated by induced electromotive force generated by weak radio waves received by the antenna. In response to the reader 52a, the non-volatile memory of the IC chip Is transmitted from the antenna (not shown) to the reader 52a (see, for example, Patent Document 1).
On the other hand, as shown in FIG. 6, the air pressure and temperature of the gas filled in the tire 60 are detected, and the information on the air pressure and temperature is sent from the transponder 61 to the external reader / interrogator 62. There is known a tire monitoring system for monitoring (see, for example, Patent Documents 2 and 3). The transponder 61 includes a measured value, calibration data, a programmable trim setting, and a memory that stores a transponder ID and the like. By changing the connection state of the CR elements (loads) connected between the terminals of the antenna device not to be operated according to the input power level, applying the PSK modulation (phase shift keying) to the received RF signal and transmitting The error rate is greatly reduced to improve the communication accuracy.
JP 2003-283365 A JP-T-2002-544744 Special table 2003-517231 gazette

By the way, RFID tags are manufactured assuming that reading and writing is performed in an environment where there is no dielectric such as rubber or water nearby, so that the dielectric around the RFID tag is similar to an RFID tag attached or embedded in a tire. When there is a rubber member that is a body, it is necessary to design circuit constants of the RFID tag according to the size and shape of the dielectric.
However, since there are tires of various sizes and shapes, in order to perform normal communication, the circuit constants must be set for each type of product tire when designing the RFID tag. The RFID tag is usually produced on a semiconductor line suitable for low-volume and high-volume production, so when such a high-mix low-volume production is performed, the cost increases. Therefore, circuit constants are designed for each type of product tire. Production was not practical. In addition, there is a method of designing in a state without a dielectric so that even if there is a dielectric nearby by providing a margin, in this case, the RFID tag is provided by providing a margin. Therefore, there is a problem that the transmission / reception accuracy is lowered and it is difficult to supply power to the arithmetic circuit inside the IC chip.
Therefore, by providing a programmable load on the RFID tag as in the transponder 61 and configuring the RFID so that the magnitude of the load can be changed for each type of product tire, circuit constants can be easily obtained. Although it may be possible to change, it is not feasible because the premise that normal power is originally supplied to the RFID tag is necessary to operate the program.

  The present invention has been made in view of the above-mentioned conventional problems, and impedance matching of RFID tags attached to the surface of products having different dielectric constants or products having different dielectric thicknesses or embedded therein. It is an object of the present invention to provide a method for easily adjusting circuit constants of a circuit and an RFID tag with adjustable circuit constants.

As a result of intensive studies, the present inventors have previously formed an impedance matching circuit composed of a plurality of circuit elements (L component, C component, R component) on the IC chip of the RFID tag. By enabling one or more connection circuits to be disconnected, or by storing in advance a connection pattern according to the usage environment of the circuit elements in the non-volatile memory, circuit elements that are not used are fixed in a disconnected state during operation. By doing so, it is found that usable circuit elements can be selected only by performing any of the above operations, and the circuit constant of the impedance matching circuit can be easily adjusted, and the present invention has been achieved. It is a thing.
That is, the invention according to claim 1 of the present invention is a method for adjusting the circuit constant of an impedance matching circuit of an RFID tag, wherein the RFID tag includes a plurality of circuit elements connected to an antenna. And the circuit constant of the RFID tag is adjusted by fixing one or more of the circuit elements in a non-connected state according to the use environment.

According to a second aspect of the present invention, in the RFID tag circuit constant adjusting method according to the first aspect, a pattern of a specific circuit element among the circuit elements that operates at a voltage higher than the operating voltage of the RFID tag. A circuit for burning out a part of the pattern is provided, a part of the pattern is burned out, and the circuit element is fixed in a non-connected state.
According to a third aspect of the present invention, there is provided an RFID tag circuit constant adjusting method according to the first aspect, wherein the switch is connected to the circuit element, and the circuit element is connected or disconnected. A non-volatile control memory for controlling the off state and a write circuit that operates at a voltage higher than the operating voltage of the RFID tag and writes the connection pattern of the impedance matching circuit in the control memory, The connection pattern is stored in advance in the memory, and a predetermined circuit element is fixed in a disconnected state during operation.

According to a fourth aspect of the present invention, there is provided the RFID tag circuit constant adjusting method according to the second or third aspect, wherein an adjustment power source is connected to the antenna, and the RFID is connected from the adjustment power source through the antenna. A part of the circuit pattern of the circuit element is burned off by applying an AC signal with a frequency different from the transmission / reception signal of the RFID tag to which the DC voltage is biased to the IC chip of the tag, or the connection pattern is connected to the control memory. It is made to memorize | store.
The invention according to claim 5 is the RFID tag circuit constant adjustment method according to claim 2 or claim 3, wherein a radio wave having a predetermined intensity is transmitted to the RFID tag, and the circuit pattern of the circuit element is transmitted. A part of the connection pattern is burned out or the connection pattern is stored in the control memory.

The invention according to claim 6 is an RFID tag including an impedance matching circuit composed of a plurality of circuit elements connected to an antenna, wherein a part of one or more circuit patterns of the circuit elements is The present invention is characterized in that it can be cut by an AC signal having a frequency different from that of the transmission / reception signal of the RFID tag, to which a DC voltage input from the antenna is biased.
The invention according to claim 7 is an RFID tag including an impedance matching circuit composed of a plurality of circuit elements connected to an antenna, and is connected to the circuit element, and the circuit element is connected or disconnected. And a non-volatile control memory, and a control circuit for controlling the open / close state of the switch according to the connection pattern of the impedance matching circuit stored in the control memory, and a voltage higher than the operating voltage of the RFID tag And a writing circuit for writing the connection pattern in the control memory.
The invention according to claim 8 is the RFID tag according to claim 6 or 7, wherein the RFID tag is an RFID tag having a dipole antenna.

According to the present invention, when adjusting the circuit constant of the impedance matching circuit of the RFID tag, the impedance matching circuit composed of a plurality of circuit elements connected to the antenna is provided, and the connection lines of the specific circuit elements are burned out. A switch that fixes a specific circuit element in a non-connected state or connects or disconnects the circuit element and a non-volatile control memory that stores a connection pattern of an impedance matching circuit are provided. The number of the circuit elements is changed by controlling the switch in accordance with the stored connection pattern to hold a specific circuit element in a disconnected state, and the circuit constant of the impedance matching circuit is adjusted. As a result, RFID tags can be manufactured by conventional low-volume mass production, and at the time of use, It can be easily changed in accordance with the circuit constants to use environment.
At this time, an adjustment power source is connected to the antenna, and an AC signal with a DC voltage biased is applied from the antenna to the IC chip of the RFID tag, or a radio wave having a predetermined intensity is irradiated to the RFID tag. The circuit constants of the RFID tag can be easily changed by burning out the connection lines and writing the connection pattern into the nonvolatile control memory.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
Best Mode
FIG. 1 is a schematic diagram showing a method for adjusting the circuit constants of the impedance matching circuit in the RFID tag 10 according to the best mode 1. The RFID tag 10 of this example includes a transmission / reception unit 11, a memory unit 12, and a control unit 13. , An LSI (hereinafter referred to as an IC chip) 16 having a power supply unit 14 and an impedance matching circuit 15, and antennas 17a and 17b extending in opposite directions from the IC chip 16 in the same line shape. In this RFID tag, the impedance matching circuit 15 includes a plurality of circuit elements M1 to M5 connected to the antennas 17a and 17b. Here, the circuit elements M1 to M5 may be one C element, R element, or L element, or a combination thereof.
In this example, in order to tune the impedance matching circuit 15, a burn-out circuit for burning out a specific circuit element (here, the circuit element M 2) of the circuit elements M 1 to M 5 on the IC chip 16. 18 and a burnout switch 19 connected to the impedance matching circuit 15 at a normal voltage and connected to the burnout circuit 18 when a voltage higher than the operating voltage of the RFID tag 10 is applied. The burnout switch 19 is configured by using a current control element such as a diode or a thyristor, which does not flow current up to a predetermined voltage, and whose impedance is drastically reduced and a large current flows when the voltage exceeds the predetermined voltage. can do.

FIG. 2 is a diagram showing an example of a circuit for burning-out. This circuit 18 for burning-out is formed adjacent to a part (hereinafter referred to as a burned-out portion) K of the circuit pattern M2r of the circuit element M2 to be burned out. The heat generating element 18r is provided. When the voltage applied to the RFID tag 10 is less than a predetermined threshold, the burn-off switch 19 is not connected to the circuit 18 for burn-out, but when the applied voltage exceeds the threshold, the burn-out switch 19 is not connected. The switch 19 is connected to the burn-out circuit 18 so that a large current flows through the heating element 18r and the temperature of the heating element 18r rises. For this reason, the pattern of the burned-out portion K adjacent to the heating element 18r is cut, and the circuit element M2 is disconnected.
Thus, an RFID tag having an impedance matching circuit in which four circuit elements (M1, M3 to M5) are connected in parallel from an RFID tag having an impedance matching circuit in which five circuit elements (M1 to M5) are connected in parallel. You can get a tag. That is, the impedance matching circuit 15 of the RFID tag 10 can be tuned.
At the time of burning, the burning circuit 18, the impedance matching circuit 15, and the normal circuit 16 J such as the transmission / reception unit 11 and the power supply unit 14 are separated by the burning switch 19, which affects other circuits. Can be tuned so that the burn-out circuit element M2 is disconnected.

In this example, tuning of the RFID tag as described above is performed when the RFID tag 10 is attached to a tire, not at the time of designing an IC chip or an antenna. That is, the circuit constant of the impedance matching circuit 15 is electrically adjusted using a tuning device 20 described later in accordance with the tire model to which the RFID tag 10 is attached. Specifically, when the number of circuit elements required in the usage environment is four, the tuning device 20 includes the antennas 17a and 17b of the RFID tag 10 and the DC power source 21 and the AC signal generator 22. The connection terminals 23a and 23b are connected, an AC signal (burn-out signal) having a frequency different from that of the transmission / reception signal of the RFID tag 10 in which a DC voltage is biased to the RFID tag 10 is input, and the burn-out circuit By burning out the pattern line of the element M2 (the burned-out portion K), the circuit element M2 is fixed in a disconnected state with respect to the antennas 17a and 17b. As a result, the number of usable circuit elements of the impedance matching circuit 15 can be adjusted from five to four, so that the RFID tag 10 can be tuned according to the use environment.
After the tuning is completed, initial information of the product tire is written on the RFID tag 10 and attached to the product tire.

Thus, according to the best mode 1, the RFID tag 10 burns out the impedance matching circuit 15 including the plurality of circuit elements M1 to M5 connected in parallel to the antennas 17a and 17b and the specific circuit element M2. A burnout circuit 18 connected to the impedance matching circuit 15 at a normal voltage, and a burnout switch 19 connected to the burnout circuit 18 when a voltage higher than the operating voltage of the RFID tag 10 is applied. The circuit element M2 is supplied to the antennas 17a and 17b by supplying an AC signal biased with a DC voltage from the tuning device 20 to the circuit 18 for burning and burning the cut-off portion K of the circuit element M2. On the other hand, since it is fixed in a non-connected state, it is connected to the impedance matching circuit 15 of the RFID tag 10. The number of road elements can be easily changed. Therefore, the impedance matching circuit 15 can be tuned according to the use environment.
In addition, since the circuit constant of the RFID tag 10 can be easily changed according to the use environment, it is affixed to the surface of a product having a different dielectric constant or a product having a different dielectric thickness or embedded in the inside. The RFID tag to be manufactured can also be manufactured by conventional low-volume mass production, and the cost of the RFID tag 10 can be greatly reduced.

In the best mode 1 described above, the case where the RFID tag 10 is attached to a tire has been described. However, the present invention is not limited to this, and a dielectric material such as rubber, resin, or ceramic is partly or entirely. It can be applied to any product having a different dielectric constant and dielectric shape for each type of product.
In the above example, the heating element 18r of the circuit 18 for burning formed adjacent to the burning part K of the circuit element M2 to be burned out is heated to burn out the burning part K. FIG. As shown in FIG. 2, a circuit 18 for burning is connected to the cut-off portion K via the burn-off switch 18a, 18b, and a large current is directly supplied to the cut-off portion K so that the cut-off portion K is burned out. May be. The burnout switches 18a and 18b are switches that are closed only when the burnout circuit 18 is operated, and are normally open.
In addition, a plurality of circuit elements for burn-out are set, and a control logic circuit for designating which circuit elements are burned out is provided in place of the circuit 18 for burn-out, and one or more are burned out in advance simultaneously with the burn-out signal. If the logic circuit is activated by inputting a signal specifying the circuit element of the circuit and the specified circuit element is fixed to the non-connected state, the number of circuit elements to be fixed to the non-connected state varies variously. Therefore, an RFID tag having a plurality of impedance matching circuits having different circuit constants can be obtained using the same RFID tag. At this time, if a tuning parameter is set in advance for each tire model and the number of circuit elements to be fixed in the disconnected state is changed by the tuning parameter input to the tuning device 20, the tuning parameter is input. It is possible to easily change the number of circuit elements to be brought into a non-connected state.
In the above example, the pattern line (burn-out portion K) of the circuit element M2 for burning is burned out using the tuning device 20 including the DC power source 21 and the AC signal generator 22. However, the RFID tag 10 In addition, the pattern line may be burned out by wirelessly transmitting a radio wave having a predetermined intensity superimposed on the carrier wave by applying an alternating current signal biased with the direct current voltage.

Best Mode 2
In the above best mode 1, the RFID tag 10 is tuned by burning out the pattern lines of the circuit element M2 for burning, but the circuit elements M1 to M5 of the impedance matching circuit 15 are tuned as shown in FIG. In addition, switches S1 to S5 that are controlled by the control circuit 31 and connect or disconnect the circuit elements M1 to M5 with respect to the antennas 17a and 17b according to the connection pattern stored in the nonvolatile memory 32 are provided. It may be provided and the connection state of the circuit elements M1 to M5 may be fixed to the connection pattern during operation.
Specifically, the control unit 13 is provided with a control circuit 31 that controls the opening and closing of the switches S1 to S5 and a non-volatile memory 32 that stores the connection pattern of the impedance matching circuit 15, and a front stage of the impedance matching circuit 15. In addition, the write circuit is connected to the impedance matching circuit 15 at a normal voltage and writes the connection pattern to the nonvolatile memory 32 based on an external input signal when a voltage higher than the operating voltage of the RFID tag 10 is applied. A write switch 34 connected to 33 is provided. During tuning, the connection pattern is written and stored in the nonvolatile memory 32. During operation, the control circuit 31 stores the connection pattern in the nonvolatile memory 32. Open and close the switches S1 to S5 according to the connection pattern To.

  That is, in the same manner as in the best mode 1, when the tuning device 20 receives an AC signal biased with a DC voltage (a write signal instructing the connection pattern of the impedance matching circuit 15) from the RFID tag 10, writing is performed. The switch 34 is connected to the write circuit 33 side. As a result, the write circuit 33 operates and the connection pattern is written into the nonvolatile memory 32. During operation of the RFID tag 10, the control unit 13 controls the opening and closing of the switches S <b> 1 to S <b> 5 based on the connection pattern of the impedance matching circuit 15 read from the nonvolatile memory 32. Accordingly, the circuit elements M1 to M5 are connected or disconnected from the antennas 17a and 17b according to the connection pattern. For example, when the optimum connection pattern in a certain use environment is M1, M3 to M5, the control circuit 31 can be operated during operation by storing the optimum connection pattern in the nonvolatile memory 32. Since the switches S1 to S5 are controlled so that the switches S1, S3 to S5 are closed and the switch S2 is closed, the impedance matching circuit 15 is configured as shown in FIG. , M3 to M5 are connected, and M2 is a non-connected surface body, and is tuned to the optimum connection pattern. Therefore, the circuit constant of the RFID tag 10 can be easily changed according to the use environment.

In addition, since tuning is not performed at the start of normal operation and the power supply voltage is not sufficient, as shown in FIG. 3B, the power supply unit 14 is provided with a switch 31S. Only the control circuit 31 of the control unit 13 is connected, and after the tuning by the control circuit 31 is completed, the other circuits of the control unit 13 and the entire normal circuit 16J such as the transmission / reception unit 11 are connected to the power supply unit 14. By doing so, at least the tuning by the control unit 13 can be performed even when the impedance is not adjusted. The opening / closing of the switch 31S may be performed by the control unit 13 or may be performed by providing a switch opening / closing circuit that is linked to the control unit 13 separately.
Further, when the RFID tag 10 is operating (at the normal voltage), the write switch 34 is connected to the impedance matching circuit 15 side, so that the write circuit 33 does not operate, so that the write is performed in the nonvolatile memory 32. The connection pattern is not rewritten, and the impedance matching circuit 15 maintains the tuned state.
In the above example, the switches S1 to S5 are provided in all of the circuit elements M1 to M5. However, when there is a circuit element that is always used regardless of the use environment, the RFID tag 10 is manufactured when the RFID tag 10 is manufactured. It suffices that a switch is not provided for a normal circuit element. As a result, the number of switches can be reduced, and the load on the writing circuit 33 and the nonvolatile memory 32 can be reduced. Therefore, the cost of the RFID tag 10 can be further reduced.
Also in the best mode 2, as in the best mode 1, the write signal instructing the connection pattern of the impedance matching circuit 15 to the carrier wave is modulated to the RFID tag 10 without using the tuning device 20. It is also possible to wirelessly transmit a radio wave having a predetermined intensity superimposed and store a desired connection pattern in the nonvolatile memory 32.

  As described above, according to the present invention, RFID tags can be manufactured by conventional low-volume mass production, and the circuit constants of the RFID tags can be easily changed. Therefore, it is necessary to change the circuit constants for each model. The RFID tag of the present invention can be applied to a wide range of products.

It is a figure which shows the method of adjusting the circuit constant of the impedance matching circuit of the RFID tag which concerns on the best form 1 of this invention. It is a figure which shows an example of the burning method of a circuit pattern. It is a figure which shows the other example of the burning-off method of a circuit pattern. It is a figure which shows the method to adjust the circuit constant of the impedance matching circuit of the RFID tag which concerns on this best form 2. It is a figure which shows an example of the conventional RFID system. It is a figure which shows the tire monitoring system using the conventional transponder.

Explanation of symbols

10 RFID tag, 11 transceiver unit, 12 memory unit, 13 control unit,
14 power supply unit, 15 impedance matching circuit, 16 IC chip, 16J normal circuit,
17a, 17b antenna, 18 burnout circuit, 18r heating element,
19 Switch for burning out, 20 Tuning device, 21 DC power supply,
22 AC signal generator, 23a, 23b connection terminal, 31 control circuit,
32 non-volatile memory, 33 writing circuit, 34 writing switch,
M1, M3-M5 circuit elements, M2 circuit elements for burn-off, S1-S6 switches.

Claims (8)

  An RFID tag is provided with an impedance matching circuit including a plurality of circuit elements connected to an antenna, and one or more of the circuit elements are fixed in a non-connected state according to a use environment, and the impedance matching circuit A circuit constant adjusting method for an RFID tag, characterized in that a circuit constant is adjusted.   A circuit that operates at a voltage higher than the operating voltage of the RFID tag and that burns out a part of a pattern of a specific circuit element among the circuit elements is provided, and part of the pattern is burned out. 2. The circuit constant adjustment method for an RFID tag according to claim 1, wherein the circuit is fixed in a non-connected state.   Provided with a switch connected to the circuit element to bring the circuit element into a connected state or a non-connected state, and a non-volatile control memory for controlling the on / off state of the switch. A write circuit that operates at a high voltage and writes the connection pattern of the impedance matching circuit in the control memory is provided, and the connection pattern is stored in the memory in advance, and a predetermined circuit element is disconnected during operation. 2. The RFID tag circuit constant adjusting method according to claim 1, wherein the circuit constant is adjusted to a state.   An adjustment power supply is connected to the antenna, and an AC signal having a frequency different from the transmission / reception signal of the RFID tag, in which a DC voltage is biased, is applied from the adjustment power supply to the IC chip of the RFID tag via the antenna. 4. The RFID tag circuit constant adjusting method according to claim 2, wherein a part of the circuit pattern of the circuit element is burned out or the connection pattern is stored in the control memory.   3. A radio wave having a predetermined intensity is transmitted to the RFID tag, and a part of the circuit pattern of the circuit element is burned out or the connection pattern is stored in the control memory. Item 4. A circuit constant adjustment method for an RFID tag according to Item 3.   An RFID tag having an impedance matching circuit composed of a plurality of circuit elements connected to an antenna, wherein a part of one or more circuit patterns of the circuit elements is biased with a DC voltage input from the antenna. In addition, the RFID tag can be cut by an AC signal having a frequency different from that of the transmission / reception signal of the RFID tag.   An RFID tag having an impedance matching circuit composed of a plurality of circuit elements connected to an antenna, the switch being connected to the circuit elements and connecting or disconnecting the circuit elements, and a non-volatile control memory And a control circuit that controls the open / close state of the switch according to the connection pattern of the impedance matching circuit stored in the control memory, and that operates at a voltage higher than the operating voltage of the RFID tag. An RFID tag comprising a writing circuit for writing a connection pattern.   The RFID tag according to claim 6 or 7, wherein the RFID tag is an RFID tag having a dipole antenna.

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