JP4115478B2 - RF tag information reading method and information writing method - Google Patents

Description

  The present invention relates to an information reading method and an information writing method for an inexpensive non-contact RF tag that does not use expensive components such as an LSI chip.

  Conventionally, in the field of non-contact tags, the method of optically reading a barcode is the most widespread and has been attached to every article. In addition to being very inexpensive, it has become popular because it has been applied to inventory management and distribution management by making it compatible with networked payment systems. However, since it is optically read, there are problems such as being vulnerable to dirt, lack of additional writeability, and a small amount of stored information.

  In recent years, non-contact RF (Radio Frequency) tags and cards using semiconductor integrated circuits (LSIs) have started to spread. These tags and cards have a large information capacity compared to barcodes and are resistant to dirt. In addition, since it is possible to add information without contact, it is characterized by excellent traceability. However, it is more expensive than a bar code, and it is technically difficult to increase the communication distance.

  On the other hand, Patent Document 1 proposes a resonance tag (RF tag) having an LC resonance circuit. Further, Patent Document 2 proposes a method of reading information for specifying the resonance frequency of an arrayed tag formed by arranging a plurality of RF tags. These RF tags are resistant to dirt and are less expensive than non-contact RF tags using LSI. However, these publications do not disclose a method capable of adding information.

  Patent Document 3 describes an ID tag that represents unique information by the difference or ratio of the frequencies of other resonant waves with respect to a reference frequency among the frequencies of the respective resonant waves. The publication also describes rewriting of the resonance frequency due to dielectric breakdown of the capacitor. Patent Document 4 describes storing reference waveform pattern data in a memory of a reflected wave analyzing apparatus for an LC resonance tag.

Japanese Patent Laid-Open No. 8-44794 JP-A-11-96326 JP 2003-271912 A JP-A-11-175650

  Accordingly, an object of the present invention is to enable stable reading of information and addition of information to a resonant tag (RF tag) that is resistant to dirt and is less expensive than a non-contact RF tag using LSI. Is.

The RF tag information reading method according to the present invention includes at least one of a resistor and a capacitor, a fuse or an anti-fuse element capable of selecting a low impedance state and a high impedance state by an electric signal, and a coil antenna, each having a resonance frequency. A method of reading information from an RF tag that resonates by electromagnetic induction, comprising at least two different electromagnetic resonance circuits, wherein the device includes a reading means that reads information by resonating the RF tag with an electromagnetic wave, and emits the information from the reading means. The frequency of the read electromagnetic wave is continuously or intermittently swept at a constant speed, a plurality of reflected waves corresponding to the resonance frequency of the plurality of electromagnetic resonance circuits are received, and the peak position of the reflected wave is detected from the start of the sweep And measure each peak position from the start of sweep using the measured value. There time before detection, or based on either the time difference between the time mutual each peak position is detected, and detects the relative relationship of the frequency mutual reflected wave plurality of.

The RF tag information writing method of the present invention uses the information reading method of the present invention to measure the resonance frequencies of the plurality of electromagnetic resonance circuits, read the information, and then set the desired resonance frequency of the electromagnetic resonance circuit. In order to change, the impedance of the fuse or the antifuse element constituting the electromagnetic resonance circuit is changed by irradiating an electromagnetic wave having a larger amplitude than that at the time of reading that matches the resonance frequency of the electromagnetic resonance circuit. And

According to the RF tag information reading method of the present invention, in an inexpensive RF tag that is resistant to dirt and does not use an expensive component such as an LSI chip, the frequency of a plurality of reflected waves corresponding to the resonance frequency of a plurality of electromagnetic resonance circuits to detect the mutual relative relationship, even if variations in the resonance frequency of the resonant circuit for each RF tag, if only the relative relationship of the resonance frequencies of the electromagnetic wave resonator circuit is maintained in the same tag, stable Information can be read out.

Further, according to the information writing method of the RF tag of the present invention, the impedance of the fuse or antifuse element constituting the desired electromagnetic resonance circuit is changed to change the resonance frequency of the electromagnetic resonance circuit, thereby stabilizing Information can be added (rewritten).

  The present invention relates to a method for reading and writing information in an inexpensive RF tag that can store, read, and additionally write multiple bits of information without using expensive components such as LSI chips.

  The term “RF” as used in this specification refers to Radio Frequency, which refers to an electromagnetic wave that can propagate through a normal space. The “tag” refers to a card-like tag, an authentication tag, or the like.

  An RF tag according to the present invention includes at least one of a resistor and a capacitor, a fuse or an antifuse element that can select a low impedance state and a high impedance state by an electric signal, and a coil antenna, and electromagnetic resonance with different resonance frequencies. At least two or more sets of circuits are provided.

  In the electromagnetic resonance circuit, a specific resonance frequency is determined by a combination of the wiring, the resistance value of the resistor, the capacitance of the capacitor, and the inductance of the coil antenna. A plurality of information can be recorded by having two or more sets of electromagnetic resonance circuits having different resonance frequencies on the same tag. Information to be stored is determined by a combination of resonance frequencies of the two or more sets of electromagnetic resonance circuits.

In the information reading method of the RF tag of the present invention, using a device including a reading means for reading information by resonating an RF tag and an electromagnetic wave, the frequency of the reading electromagnetic wave emitted from the reading means is continuously or intermittently swept, By receiving a plurality of reflected waves corresponding to the resonance frequencies of the plurality of electromagnetic resonance circuits, an operation for searching for the resonance frequency of the RF tag is performed. Then, directly instead of reading out the information based on the frequency of the reflected wave, to detect the relative relationship of the frequency mutual plurality of reflected waves, and reads the information on the basis of this. Accordingly, even if the resonance frequency of the plurality of electromagnetic resonance circuits is shifted due to, for example, manufacturing variation of the RF tag, the reading operation is not affected, so that stable information reading can be performed.

The RF tag according to the present invention includes a fuse or an antifuse element capable of selecting a low impedance state and a high impedance state by an electric signal in an electromagnetic wave resonance circuit. Accordingly, the resonance frequency can be prevented from changing or resonating with the electromagnetic wave irradiated from the outside. This makes it possible to electrically rewrite information from the outside. This fuse or antifuse element can also function as the resistor or capacitor. The fuse itself is a resistor, the initial state is low resistance, and a state change is caused by passing a large current, and the state changes to a high resistance state. On the other hand, the anti-fuse element is a capacitor itself, and the initial state is high resistance. When the high voltage is applied, the anti-fuse element changes its state and changes to the low resistance state.

In the information writing method of the RF tag according to the present invention, in order to change the resonance frequency of the desired electromagnetic resonance circuit after reading out the information by the information reading method of the present invention, the reading that matches the resonance frequency of the electromagnetic resonance circuit is performed. Irradiating electromagnetic waves with a larger amplitude than the time, and changing the impedance of the fuse or anti-fuse element having the above characteristics constituting the electromagnetic wave resonance circuit, it is possible to add (rewrite) stable information. it can.

  Embodiments of the present invention will be described below with reference to the drawings.

(First Reference Embodiment)
Figure 1 is a diagram showing the configuration of the RF tag in the present reference embodiment. Four sets (U0 to U3) of electromagnetic resonance circuit units including one resistor (R0 to R3), one capacitor (C0 to C3), and one coil antenna (L0 to L3) are formed on a plastic substrate. Thus, one RF tag is configured. The resonance frequency bands of each unit are separated from each other.

  The electromagnetic wave resonance unit U0 is a reference electromagnetic wave resonance circuit, and has a fixed reference resonance frequency.

The electromagnetic wave resonance units U1, U2, and U3 correspond to the 1st place, the 2nd place, and the 22nd place of the binary system, respectively, and the resonance frequency of each electromagnetic wave resonance unit is the magnitude of the capacitance of the capacitor included in each unit. By selecting either (binary), a binary resonance frequency can be selected for each unit. Specifically, the capacitors included in the electromagnetic wave resonance units U1, U2, and U3 have an antifuse element function, and have a high resistance and a large capacitance in the initial state, and a low resistance and a small capacitance after the state change. The state can be changed by applying a large voltage to the antifuse element .

FIG. 2 shows the DC electrical characteristics of the antifuse element alone. It can be seen from the first voltage scan that the current value suddenly increases around 3 V, and that the state has changed from the high impedance (high resistance) state to the low impedance (low resistance) state. It can be seen that the low impedance state is maintained in the second voltage scan.

When such an antifuse element is used in an electromagnetic resonance circuit, if the RF peak value of the resonance frequency is sufficiently large, the antifuse element breaks down and the resonance frequency of the electromagnetic resonance circuit transitions. In addition, since the anti-fuse element is irreversibly short-circuited and the resonance frequency fluctuates, information can be stably rewritten (added).

  FIG. 3 shows an example of a system in which the RF tag and the reading device are combined. An RF tag 1, a reading antenna 2, and a reading device 3 are configured. The reading electromagnetic wave 4 emitted from the reading antenna 1 resonates with the RF tag and a reflected wave 5 is generated. The reflected wave is received by the readout antenna 2 and analyzed by the readout device 3 to obtain information stored in the RF tag 1.

  FIG. 4 is a graph showing the frequency of the read electromagnetic wave radiated from the readout antenna and the intensity of the reflected wave in order to show an example of the reflected wave analysis method in the readout device 3. In FIG. 4, the resonance frequency band of each unit U1 to U3 is shown, and the binary resonance frequency corresponding to the size of the capacitor contained in each unit (for example, C11 and C12 in the case of U1) is shown. Yes. For example, in the case of U1, the resonance frequency corresponding to C11 corresponds to “0” in the first place, and the resonance frequency corresponding to C12 corresponds to “1” in the first place. Therefore, in the case of FIG. 4, “101” is indicated in binary.

In this reference embodiment, the reflected wave frequency is identified by measuring the frequency differences Δf1, Δf2, and Δf3 from the reference reflected wave frequency instead of using the absolute frequency value for identifying the reflected wave frequency position. This is advantageous in that the read operation is not affected even if the resonance frequency is shifted due to manufacturing variations of the RF tag.

  Next, FIG. 5 shows a state after irradiating an RF electromagnetic wave having a larger amplitude than that at the time of reading in accordance with the resonance frequency of U2. It can be seen that the antifuse state has changed and the resonant frequency of U2 has changed. As a result, the recorded information was “111”. As a result, additional information can be added.

  In order to determine the resonance frequency of each unit, it is necessary to determine the resistance value of the resistor, the capacitance of the capacitor, and the inductance of the coil, respectively, but it is possible to omit the resistor or the capacitor, the resistor, the capacitor It is also possible to mount a plurality of coils.

  Moreover, as the means for selecting the resonance frequency of each unit, the magnitude of the capacitance of the capacitor is selected in the above embodiment, but it is also possible to select the magnitude of the resistance value of the resistor and the magnitude of the inductance value of the coil. Furthermore, not only binary values but also ternary or higher values can be selected.

Further, without using the anti-fuse element, also serves as a function of the resistor, it is also possible to use a fuse.

(Second Reference Embodiment)
The RF tag in the present reference embodiment is basically the same as that of the first reference embodiment, but does not have a reference electromagnetic resonance circuit, and four sets of electromagnetic resonance circuit units are each in the binary system 1 place, It corresponds to the 2nd place, the 22nd place, and the 23rd place. Therefore, the resonance frequency of each electromagnetic resonance unit can be selected as a binary resonance frequency for each unit by selecting one of the magnitudes (binary values) of the capacitor capacity included in each unit.

Analysis Method of the reflected wave in the present reference embodiment, compares the acquired plurality of reflected wave peak shape (graph) and a prepared waveform library as shown in FIG. 6 (a) (graph), the closest This is a method for judging that the information is the same as the library.

  As an example, when a plurality of reflected waves as shown in FIG. 6B are acquired, it is understood that the information is (0100) in FIG. 6A indicating the waveform closest to the peak waveform. it can.

In the present reference embodiment as described above, converts the plurality of reflected wave in the graph, it is carried out the identification of the reflected wave frequency position in comparison with the previously prepared graph. But this in addition to, a method of method of extracting the points fluctuation width is large, and image recognition comparison.

Furthermore, the following are mentioned as a modification of 1st reference embodiment and 2nd reference embodiment.

First, when detecting a plurality of reflected waves frequencies mutual relative relationship of how to determine the respective frequency, for can include two variations.

  The first is the frequency at which f ′ (λ) obtained by differentiating the function P = f (λ) once changes from positive to negative, where λ is the frequency and P is the intensity of the detected reflected wave. This is a method of setting the peak frequency of the reflected wave.

  Second, when the frequency is λ, and the intensity of the detected reflected wave is P, the frequency f ′ (λ) obtained by differentiating the function P = f (λ) twice changes from positive to negative. In this method, the center frequency of the frequency changing from positive to negative is used as the peak frequency of the reflected wave.

  Next, a method of detecting the relative relationship between frequencies without using the frequency value itself can be mentioned.

  For example, on the assumption that frequency scanning is performed at a constant speed, the time from the start of scanning to the detection of the peak position is measured, and using the measured value, the time from the start of scanning to the detection of each peak position Alternatively, it is possible to detect the relative relationship between the frequencies by using the time difference between the times when the peak positions are detected and comparing them.

It is a figure which shows the structure of RF tag which concerns on the 1st reference embodiment of this invention. It is a graph for demonstrating the characteristic of the antifuse which is a component of the electromagnetic wave resonance unit of RF tag which concerns on this invention. 1 is a schematic diagram showing a system including an RF tag according to the present invention. It is a graph which shows the analysis method of the reflected wave in the 1st reference embodiment of the present invention. It is a graph which shows the analysis method of the reflected wave in the 1st reference embodiment of the present invention. It is a graph which shows the analysis method of the reflected wave in the 2nd reference embodiment of the present invention.

Explanation of symbols

1 RF tag 2 Reading antenna 3 Reading device 4 Reading electromagnetic wave 5 Reflected wave

Claims (2)

An electromagnetic wave including at least one of a resistor and a capacitor, a fuse or antifuse element capable of selecting a low impedance state and a high impedance state by an electric signal, and at least two sets of electromagnetic resonance circuits having different resonance frequencies from each other. An information reading method for an RF tag that resonates by induction,
Using a device including a reading unit that reads out information by resonating the RF tag and an electromagnetic wave, the frequency of the reading electromagnetic wave emitted from the reading unit is continuously or intermittently swept at a constant speed, and the plurality of electromagnetic resonance circuits Receives a plurality of reflected waves corresponding to the resonance frequency, measures the time from the start of sweep until the peak position of the reflected wave is detected, and uses the measured value to detect each peak position from the start of sweep time to, or based on either the time difference between the time mutual each peak position is detected, the information reading the RF tag, characterized by detecting the relative relationships of the frequency mutual reflected wave plurality of Method. The information readout method according to claim 1 , wherein after the resonance frequency of the plurality of electromagnetic resonance circuits is measured and the information is read out, the resonance of the electromagnetic resonance circuit is changed in order to change the resonance frequency of the desired electromagnetic resonance circuit. An RF tag information writing method comprising irradiating an electromagnetic wave having a larger amplitude than that at the time of reading that matches a frequency to change an impedance of the fuse or antifuse element constituting the electromagnetic wave resonance circuit.

Images