JP2018093309A - Wireless tag communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time required until data communication is started, while determining radio field intensity appropriately without being affected by external noise.SOLUTION: A memory 31 previously storing a resonance frequency of a tag 3 is provided in the tag 3. Control section 41 of a reader/writer 2 reads the resonance frequency of the tag 3 stored in the memory 31 of the tag 3, by transmitting radio field intensity of a carrier signal to the tag 3, while changing to maximum radio field intensity at a radio field intensity setting section 8. Furthermore, the control section 41 acquires a lower limit radio field intensity from a storage section 42, by using the resonance frequency of the tag 3 thus read, and a preset distance between it and the tag 3. After the frequency of the carrier signal to the tag 3 is changed to the resonance frequency of the tag 3 thus read in a frequency setting section 7, the radio field intensity of the carrier signal to the tag 3 is set to the lower limit radio field intensity acquired from the maximum radio field intensity in the radio field intensity setting section 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wireless tag communication system including a tag and a reader / writer, and more particularly to a technique for controlling the frequency and radio wave intensity of a carrier signal.

  In a wireless tag communication system, a reader / writer transmits a carrier wave signal modulated according to data to be transmitted to a tag. On the other hand, the tag receives the carrier signal from the reader / writer and demodulates it to hold the data. Further, the tag transmits a subcarrier signal modulated according to the held data to the reader / writer. On the other hand, the reader / writer receives the subcarrier signal from the tag, demodulates it, and reads the data held in the tag.

  By the way, in the radio tag communication system as described above, when the frequency of the carrier wave signal to the tag deviates from the resonance frequency of the tag, the communicable distance between the reader / writer and the tag is reduced. However, if the radio wave intensity (output) of the carrier signal of the reader / writer is increased in order to increase the communication distance between the reader / writer and the tag, the carrier signal may adversely affect peripheral devices.

  Therefore, in the conventional RFID tag communication system, for example, as shown in Patent Document 1 below, the radio wave intensity of the carrier signal is detected while changing the frequency of the carrier signal of the reader / writer. Then, a technique has been proposed in which the radio wave intensity and frequency suitable for communication are obtained, and the obtained frequency is used as the frequency of the carrier wave signal so that the radio wave intensity of the carrier wave signal is not increased more than necessary.

JP 2007-212698 A

  However, in the conventional wireless tag communication system as described above, every time data communication is started between the reader / writer and the tag, the frequency of the carrier wave signal is mutually changed to obtain the radio wave intensity and frequency suitable for communication. There is a need to change to many different frequencies. For this reason, in this conventional wireless tag communication system, it takes time to start data communication every time data communication is performed. Further, if the frequency of the carrier signal is changed when external noise is generated, the selection of the radio wave intensity (and hence the selection of the frequency of the carrier signal) may not be performed properly.

  The present invention has been made in view of the above circumstances, and an object thereof is to shorten the time required to start data communication while appropriately determining the radio wave intensity without being affected by external noise.

  A wireless tag communication system according to an aspect of the present invention is a wireless tag communication system including a tag and a reader / writer that performs data communication with the tag, and the tag has a resonance frequency of the tag. The reader / writer includes a memory stored in advance, the carrier writer for generating a carrier wave signal to be transmitted to the tag, a frequency setting unit for setting the frequency of the carrier wave signal generated by the carrier wave generator, and the frequency setting A radio field intensity setting unit that sets the radio field intensity of the carrier signal whose frequency has been changed by the unit, an antenna that transmits the carrier signal whose radio field intensity is set by the radio field intensity setting unit, to the tag, the frequency setting unit, and For communication with the tag when the distance between the control unit that controls the radio field intensity setting unit and the tag is a preset distance. A storage unit that stores a relationship between a resonance frequency of a carrier wave signal that is present and a minimum radio wave intensity that allows data communication with the tag at the resonance frequency, and the control unit communicates with the tag. At the start, the carrier signal is transmitted from the antenna to the tag, and when the tag receives the carrier signal from the reader / writer, the tag reads the resonance frequency of the tag stored in the memory, and the reader Transmitting as a subcarrier to the writer, the control unit of the reader / writer reads the minimum radio wave intensity corresponding to the resonance frequency indicated by the subcarrier transmitted from the tag from the storage unit, and sets the frequency Unit sets the frequency of the carrier signal to the resonance frequency indicated by the subcarrier, and the radio wave intensity setting unit sets the radio wave strength of the carrier signal. And sets to the said minimum signal strength indicator reading.

  According to the present invention, it is possible to shorten the time required to start data communication while appropriately determining the radio wave intensity without being affected by external noise.

It is a block diagram which shows the principal part structure of the radio | wireless tag communication system which concerns on one Embodiment of this invention. It is a flowchart which shows the flow of operation | movement with the reader / writer shown in FIG. It is a figure which shows the specific example of the information memorize | stored in the memory | storage part shown in FIG.

  Hereinafter, a wireless tag communication system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a main configuration of a wireless tag communication system according to an embodiment of the present invention. The wireless tag communication system 1 of this embodiment includes a reader / writer 2 and a passive or active tag 3. The reader / writer 2 performs data communication with the tag 3.

  More specifically, in the RFID tag communication system 1, the reader / writer 2 modulates a carrier wave signal according to data to be transmitted, and transmits the modulated carrier wave signal to the tag 3. The received subcarrier signal is demodulated to generate data and output it to the outside.

  The tag 3 generates a subcarrier signal corresponding to data to be transmitted to the reader / writer 2. The tag 3 transmits the generated subcarrier signal to the reader / writer 2.

  As shown in FIG. 1, the reader / writer 2 includes a communication control unit 4, a carrier wave generation unit 5, an amplifier 6, a frequency setting unit 7, a radio wave intensity setting unit 8, an antenna 9, an envelope detection unit 10, an operational amplifier 11, and each Capacitors C1, C2 and the like are provided.

  The communication control unit 4 includes a control unit 41 and a storage unit 42. The communication control unit 4 performs control necessary for communication with the tag 3. The distance between the reader / writer 2 and the tag 3 is a predetermined fixed value.

  The control unit 41 is configured using a processor such as a CPU (Central Processing Unit), an MPU, or an ASIC, and controls overall operation of the reader / writer 2.

  The storage unit 42 is configured using a RAM (Random Access Memory) or the like. The storage unit 42 can perform data communication with the tag 3 at the resonance frequency of the carrier wave signal used for transmission with the tag 3 when the distance to the tag 3 is the predetermined fixed value. The relationship with the minimum radio wave intensity is stored. Further, the resonance frequency (described later) of the tag 3 that is acquired from the tag 3 by the control unit 41 and is stored in the memory 31 of the tag 3 is written in the storage unit 42.

  The demodulation circuit 12 includes an envelope detection unit 10, an operational amplifier 11, and a capacitor C2. The demodulation circuit 12 demodulates the subcarrier signal from the tag 3.

  Based on the instruction signal from the control unit 41, the carrier wave generation unit 5 oscillates a carrier signal having a specified frequency (for example, 13.56 MHz) and outputs the carrier signal to the amplifier 6.

  Based on the instruction signal from the control unit 41, the amplifier 6 amplitude-modulates and outputs the carrier signal from the carrier generation unit 5. The amplifier 6 controls the gain based on the instruction signal from the control unit 41 and modulates the carrier wave signal output to the frequency setting unit 7.

  The frequency setting unit 7 changes the frequency of the carrier wave signal from the amplifier 6 according to the instruction signal input from the control unit 41 and outputs it.

  When an instruction signal is input from the control unit 41, the radio wave intensity setting unit 8 changes the radio wave intensity of the carrier wave signal from the frequency setting unit 7 according to the input instruction signal and outputs it.

  The antenna 9 transmits and receives a carrier wave signal. The antenna 9 transmits the carrier signal output from the radio wave intensity setting unit 8 and receives the subcarrier signal transmitted from the tag 3.

  The carrier wave signal whose radio wave intensity is set by the radio wave intensity setting unit 8 and the subcarrier signal received by the antenna 9 are input to the envelope detection unit 10 via the capacitor C1. The envelope detector 10 is composed of a voltage doubler circuit, receives a carrier signal and a subcarrier signal, extracts an envelope of the received signal, and outputs an analog signal corresponding to the envelope.

  The high-frequency component of the analog signal corresponding to the envelope output from the envelope detector 10 (signal corresponding to the rise and fall of the envelope) is applied to the operational amplifier 11 through the capacitor C2. A signal corresponding to the rise and fall of the envelope and a DC offset voltage vf due to voltage division are applied to the pair of input terminals of the operational amplifier 11, and a digital signal corresponding to the envelope is output from the output terminal of the operational amplifier 11. Is output.

  The tag 3 includes a memory 31, a communication control unit 32, and an antenna 33.

  The memory 31 stores in advance the resonance frequency of the tag 3 used for communication with the reader / writer 2. Further, the memory 31 stores data obtained by demodulating the carrier wave signal from the reader / writer 2.

  The communication control unit 32 controls communication with the reader / writer 2. The antenna 33 transmits and receives information to and from the reader / writer 2 by transmitting and receiving a carrier wave and a subcarrier.

  The resonance frequency of the tag 3 is a value measured by the tag 3 alone when the tag 3 is shipped, for example, and is written in the memory 31 in advance. In the wireless tag communication system 1 of the present embodiment, when the reader / writer 2 and the tag 3 are installed at a predetermined distance (the predetermined fixed value), the first data is transferred from the reader / writer 2 to the tag 3. Before the communication is performed, the resonance frequency previously written in the memory 31 is read by the reader / writer 2 and applied to the carrier wave signal transmitted from the reader / writer 2.

  That is, in the wireless tag communication system 1 of the present embodiment, the reader / writer 2 performs initial data communication with the tag 3 (transmitting / receiving a carrier wave and a subcarrier indicating data to be transmitted to / from the tag 3). Before the control unit 41 transmits the carrier wave signal whose radio field intensity is set to the maximum radio field intensity by the radio field intensity setting unit 8 to the tag 3, the resonance frequency of the tag 3 stored in the memory 31 of the tag 3 is transmitted. Read. Further, the control unit 41 reads out the minimum radio wave intensity that can be used for communication at the resonance frequency stored in association with the resonance frequency of the read tag 3, and the frequency setting unit 7 After changing the frequency of the carrier wave signal to the tag to the resonance frequency, the radio wave intensity setting unit 8 changes the radio wave intensity of the carrier wave signal to the read minimum radio wave intensity (details will be described later).

  Hereinafter, the operation of the wireless tag communication system 1 configured as described above will be specifically described. FIG. 2 is a flowchart showing a flow of operations in the reader / writer shown in FIG. FIG. 3 is a diagram illustrating a specific example of information stored in the storage unit illustrated in FIG. 1. In the following description, the operation of the reader / writer 2 will be mainly described. In the following description, processing in a situation where the distance between the reader / writer 2 and the tag 3 is set at a predetermined fixed value will be described.

  Before the reader / writer 2 performs initial data communication with the tag 3 (transmitting / receiving a carrier wave and a subcarrier indicating data to be transmitted to / from the tag 3), first, the control unit 41 It is determined whether or not the resonance frequency of the tag 3 is stored in the storage unit 42 (S1).

  Here, when the control unit 41 determines that the resonance frequency of the tag 3 is stored in the storage unit 42 (YES in S1), the control unit 41 has already performed data communication with the tag 3. Judge that Then, the control unit 41 modulates the carrier wave signal according to the data to be transmitted to the tag 3, and the resonance frequency of the tag 3 stored in the storage unit 42 and the minimum frequency at this resonance frequency Using the carrier wave signal set to the radio wave intensity (S6), data communication to the tag 3 is performed (S7).

  On the other hand, when the control unit 41 determines that the resonance frequency of the tag 3 is not stored (NO in S1), the process for acquiring the resonance frequency of the tag 3 stored in advance in the memory 31 of the tag 3 To start.

  Specifically, the control unit 41 outputs the instruction signal of the amplifier 6 and changes the amplification factor of the carrier wave generated by the carrier wave generation unit 5 to store the tag 3 in the memory 31. The resonance frequency of the tag 3 is modulated to a carrier wave signal corresponding to a command (data) required to notify the reader / writer 2 side.

  Further, the control unit 41 outputs an instruction signal for changing the radio wave intensity of the carrier wave signal transmitted to the tag 3 to the maximum radio wave intensity to the radio wave intensity setting unit 8. In accordance with this instruction signal, the radio wave intensity setting unit 8 sets the radio wave intensity of the carrier wave signal from the frequency setting unit 7 to the maximum radio wave intensity (S2). Then, the carrier wave signal set to the maximum radio field intensity is transmitted from the antenna 9 to the tag 3. In addition, since the carrier wave signal having the maximum radio wave intensity is transmitted to the tag 3 in this way, the reader / writer 2 reliably transmits data to the tag 3 (that is, the resonance frequency of the tag 3). Can be reliably performed.

  In S2, the control unit 41 causes the radio field intensity setting unit 8 to set the radio field intensity of the carrier wave signal transmitted to the tag 3 to the maximum radio field intensity. However, the control unit 41 is not necessarily limited to the maximum intensity. It may be set to other predetermined radio wave intensity.

  Thereafter, when the carrier signal is received by the antenna 33 of the tag 3, the communication control unit 32 reads the resonance frequency of the tag 3 stored in the memory 31. Further, the communication control unit 32 generates a subcarrier signal including the read resonance frequency. The generated subcarrier is transmitted from the antenna 33 to the reader / writer 2.

  In the reader / writer 2, when the antenna 9 receives the subcarrier signal from the tag 3, the received subcarrier signal is demodulated by the demodulation circuit 12, and the data indicated by the subcarrier signal, that is, the resonance frequency is extracted. Is done. The extracted resonance frequency is stored in the storage unit 42 (S3).

  Subsequently, the control unit 41 changes the frequency of the carrier wave signal used for communication with the tag 3 to the resonance frequency stored in the storage unit 42 (S4). That is, the control unit 41 outputs an instruction signal to the frequency setting unit 7, whereby the frequency of the carrier wave signal used for communication with the tag 3 is stored in the storage unit 42 in the frequency setting unit 7. Change to frequency.

  Next, the control unit 41 reads and acquires the minimum radio wave intensity associated with the resonance frequency from the storage unit 42 (S5). In the storage unit 42, as shown in FIG. 3, a distance between the reader / writer 2 and the tag 3 (a preset distance between the tag 3) is a predetermined fixed value (for example, 5 mm). In some cases, the relationship between the resonance frequency of the tag 3 and the minimum radio wave intensity at which the reader / writer 2 can perform data communication with the tag 3 at this resonance frequency is stored. For example, the control unit 41 acquires the minimum radio wave intensity α7 from the storage unit 42 when the read resonance frequency of the tag 3 is, for example, f7.

  Subsequently, the control unit 41 causes the radio wave intensity setting unit 8 to change the radio wave intensity of the carrier wave signal to the tag 3 to the acquired minimum radio wave intensity (S6). That is, the control unit 41 outputs an instruction signal to the radio wave intensity setting unit 8 to change the radio wave intensity of the carrier wave signal used for communication with the tag 3 to the acquired minimum radio wave intensity. As a result, communication between the reader / writer 2 and the tag 3 can be ensured, and the radio wave intensity of the carrier wave signal can be prevented from becoming unnecessarily high. It is possible to suppress the occurrence of adverse effects as much as possible.

  Subsequently, the control unit 41 starts data transmission to the tag 3 using the carrier wave having the resonance frequency and the radio wave intensity (S7). The control unit 41 includes the data to be transmitted to the tag 3 and modulates the carrier wave signal, and then transmits the modulated carrier wave signal to the tag 3 via the antenna 9.

  As described above, when the resonance frequency of the tag 3 is stored in the storage unit 42 in S1 (YES in S1), the control unit 41 is associated with the resonance frequency. In order to perform data communication with the tag 3 using a carrier wave signal having a minimum radio wave intensity, when the reader / writer 2 performs the second and subsequent data communication with the tag 3, for example, The data communication with respect to the tag 3 can be started immediately without performing the processes of S2 to S5 for acquiring the resonance frequency between the tag 3 and the tag 3.

  As described above, in the wireless tag communication system 1 according to the present embodiment, the tag 3 includes the memory 31 in which the resonance frequency used for communication with the reader / writer 2 is stored in advance. Before the first data communication with the tag 3, the control unit 41 of the reader / writer 2 changes the radio wave intensity of the carrier wave signal to the tag 3 to the maximum radio wave intensity by the radio wave intensity setting unit 8 and transmits it to the tag 3. As a result, the resonance frequency of the tag 3 stored in the memory 31 of the tag 3 is acquired. Then, the control unit 41 causes the frequency setting unit 7 to set the frequency of the carrier wave signal used for communication with the tag 3 to the acquired resonance frequency of the tag 3, and the radio wave intensity setting unit 8 sets the radio wave intensity of the carrier wave signal. The minimum radio wave intensity associated with the resonance frequency is set.

  For this reason, in the wireless tag communication system 1 according to the present embodiment, unlike the conventional example, the reader / writer 2 changes the frequency to a large number of frequencies and transmits a radio wave each time data communication with the tag 3 is performed. There is no need to detect the intensity. For this reason, in the RFID tag communication system 1 according to the present embodiment, the time required to establish data communication with the tag 3 can be shortened. Further, in the wireless tag communication system 1 according to this embodiment, the acquired resonance frequency of the tag 3 is used as the frequency of the carrier wave signal, and the lowest radio wave intensity that can be communicated at this resonance frequency is used as the carrier wave signal. Since the strength is set, it is not necessary to perform much communication with the tag 3 in order to determine the resonance frequency and radio wave strength used for communication. For this reason, even when the external noise is generated, the radio wave intensity can be appropriately determined without being affected by the external noise.

  In the present embodiment, a distance of 5 mm is used as a preset distance between the tag 3 and the preset distance between the storage unit 42 and the tag 3 is 5 mm. The configuration in which the relationship between the frequency of the carrier wave signal to the tag 3 and the minimum radio wave intensity at which data communication with the tag 3 can be performed (FIG. 3) is stored in advance has been described. However, the present invention is not limited to this, and the distance from the tag 3 is set in advance in the communication control unit 4, and the distance between the storage unit 42 and the tag 3 that is set in advance is There is no limitation as long as the relationship between the frequency of the carrier wave signal to the tag 3 and the minimum radio wave intensity at which data communication with the tag 3 can be performed is stored in the storage unit 42 in advance.

  Specifically, before performing data communication, for example, a separation distance between the reader / writer 2 and the tag 3 is detected, and the detected separation distance is set as a preset distance between the tag 3 and the communication control unit. 4 and the frequency of the carrier wave signal to the tag 3 in the case where it is the preset distance between the set tag 3 and the data communication with the tag 3. A configuration in which the relationship with the minimum radio wave intensity that can be performed may be stored in advance.

  In the above description, the control unit 41 has described the configuration in which the reader / writer 2 acquires the resonance frequency of the tag 3 from the memory 31 of the tag 3 before performing the first data communication with the tag 3. The present invention is not limited to this. For example, every time data communication with the tag 3 is performed, or at a time when data communication is performed after a predetermined time has elapsed since the first data communication is performed, the tag 3 A configuration in which the reader / writer 2 acquires the resonance frequency may be employed.

  The RFID tag communication system 1 according to another embodiment of the present invention is applicable to an image forming system (not shown). The image forming system includes a toner container and an image forming apparatus.

  The image forming apparatus includes a toner container holding unit, an image forming unit, a paper feeding unit, a transport unit, a fixing unit, and a discharge unit. The toner container holding unit includes a housing that holds the toner container and a reader / writer 2. The reader / writer 2 communicates with the tag 3 to acquire information such as toner container identification information, toner storage amount and toner container usage status. The image forming unit includes an image carrier (photosensitive drum) that carries an image, a charging device that uniformly charges the surface of the image carrier, and a laser beam on the surface of the uniformly charged image carrier. An exposure device that forms an electrostatic latent image with the toner, a developing device that forms a toner image on the electrostatic latent image by moving toner to the surface of the image carrier, and the toner carried on the surface of the image carrier. And a transfer device that transfers the toner image onto a sheet or belt. The paper feeding unit stores sheets and feeds them to the transport unit. The conveyance unit conveys a sheet fed from the sheet feeding unit to the image forming unit. The fixing unit fixes the toner image transferred to the sheet by heating and pressing the sheet. The discharge unit is provided outside the image forming apparatus and holds a sheet on which toner is fixed.

  The toner container includes a tag 3 and a housing that stores toner for forming an image. The tag 3 holds information such as toner container identification information, toner storage amount and toner container usage status.

  Since the image forming system adopting the above configuration can reduce the time required to start data communication while appropriately determining the radio wave intensity without being affected by external noise, a toner container is mounted. Thereafter, it is possible to quickly form an image.

  Moreover, the structure and process demonstrated using FIG. 1 thru | or FIG. 3 are only one Embodiment of this invention, and are not the meaning which limits this invention to the said structure and process.

DESCRIPTION OF SYMBOLS 1 RFID tag communication system 2 Reader / writer 5 Carrier generation part 6 Amplifier 7 Frequency setting part 8 Radio wave intensity setting part 41 Control part 42 Storage part 3 Tag 31 Memory

Claims (2)

A wireless tag communication system comprising a tag and a reader / writer that performs data communication with the tag,
The tag is
It has a memory that pre-stores the resonance frequency of the tag,
The reader / writer
A carrier generation unit that generates a carrier signal to be transmitted to the tag;
A frequency setting unit for setting the frequency of the carrier signal generated by the carrier generation unit;
A radio wave intensity setting unit for setting the radio wave intensity of the carrier signal whose frequency has been changed by the frequency setting unit;
An antenna for transmitting the carrier wave signal whose radio wave intensity is set by the radio wave intensity setting unit to the tag;
A control unit for controlling the frequency setting unit and the radio wave intensity setting unit;
Relationship between the resonance frequency of the carrier signal used for communication with the tag when the distance between the tag and the tag is set in advance, and the minimum radio wave intensity at which data communication with the tag can be performed at the resonance frequency A storage unit for storing
The control unit causes the carrier signal to be transmitted from the antenna to the tag at the start of communication with the tag,
When the tag receives the carrier signal from the reader / writer, it reads out the resonance frequency of the tag stored in the memory, and transmits it to the reader / writer as a subcarrier,
The control unit of the reader / writer reads the minimum radio wave intensity corresponding to the resonance frequency indicated by the subcarrier transmitted from the tag from the storage unit, and the frequency setting unit determines the frequency of the carrier signal. A radio tag communication system in which the resonance frequency indicated by the subcarrier is set, and the radio wave intensity setting unit sets the radio wave intensity of the carrier signal to the read minimum radio wave intensity. The control unit, at the start of communication with the tag, causes the antenna to transmit the carrier wave signal in which the radio field intensity is set to the maximum radio field intensity from the antenna to the tag,
The tag reads out a resonance frequency of the tag stored in the memory and transmits it to the reader / writer as a subcarrier when receiving the carrier signal having the maximum radio wave intensity from the reader / writer. The wireless tag communication system according to 1.