JP2001034718A - Reader/writer for id tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect whether or not it is the state of enabling the supply of power required for operation to the coil for antenna of an ID tag by finding the inductance value of a transmitting antenna composed of a coil and estimating the degree of magnetic coupling with the coil for antenna of the ID tag on the basis of this inductance value. SOLUTION: When frequency tuning is completed, an MPU 27 obtains ON/ OFF information in respect to respective switches 41c of a capacitor circuit 38 for resonance from a capacitor (C) ON/OFF control circuit 47 and finds the electrostatic capacitance of the capacitor circuit 38 for resonance from that ON/OFF information. Corresponding to that found electrostatic capacitance, the inductance value of a coil 33 for transmitting antenna is operated, that operated inductance value is compared with a reference value and whether communication with the ID tag is enabled or not, namely, the degree of magnetic coupling between the coil 33 for transmitting antenna and the coil for antenna of the ID tag is estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ID tag reader / writer which communicates with an ID tag by radio waves to exchange data.

[0002]

For example, a remote ID using a high-frequency radio wave is used as a moving object identification system.
There is a system. In this method, communication between a reader / writer and an ID tag is performed by radio waves to read data of an ID tag at a remote position or write data to the ID tag.

[0003] In such a remote ID system, an ID tag that does not have a battery and is dependent on an external power source is mainly used as an ID tag. A radio signal for operating power is transmitted from the reader / writer to the ID tag dependent on the external power source, and the ID tag operates by receiving the radio signal.

[0004] The antenna of the ID tag is formed of a coil, and the magnetic flux, which is a radio signal emitted from a reader / writer, interlinks the coil for the antenna, so that the ID tag receives the radio signal. For this reason,
Even when the ID tag is within the communication range of the reader / writer, if the antenna coil of the ID tag is parallel to and does not interlink with the magnetic flux emitted from the reader / writer as a radio signal, the ID tag does not operate and communication becomes impossible. .

[0005] Even if the antenna coil of the ID tag interlinks with the magnetic flux from the reader / writer, the magnitude of the received power varies depending on the amount of the interlinkage magnetic flux. For example, if the ID tag is far from the reader / writer, the amount of magnetic flux linked to the antenna coil may be small, and power required for operation may not be obtained. Conversely, when the ID tag is near the reader / writer and the amount of magnetic flux linked to the antenna coil is large, more power than necessary is obtained, which may result in wasted power.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect whether or not the power required for operation can be supplied to an antenna coil of an ID tag. Another object of the present invention is to provide a reader / writer for an ID tag.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, when communicating with an ID tag, an inductance value of a transmission antenna formed of a coil is obtained.
In this configuration, the degree of magnetic coupling between the ID tag and the antenna coil is estimated based on the inductance value.

When the reader / writer communicates with the ID tag,
The antenna coil of the reader / writer and the antenna coil of the ID tag are electromagnetically coupled to each other, so that mutual induction occurs between them, and the inductance value of the antenna coil changes. In this case, in the reader / writer, the inductance value of the transmitting antenna coil indicates the strength of the electromagnetic coupling between the ID tag and the receiving antenna coil. The strength of the electromagnetic coupling with the transmission antenna coil of the ID tag indicates the magnitude of the electromotive force induced in the reception antenna coil of the ID tag when a radio signal is transmitted from the transmission antenna coil of the reader / writer. It will be. Therefore, according to the above configuration, it is possible to determine whether or not communication with the ID tag is possible based on the inductance value of the transmission antenna coil of the reader / writer.

According to a second aspect of the present invention, the output of the transmitting antenna is controlled in accordance with the magnetic coupling estimated by the coupling acquiring means. For example, when the ID tag is far away from the reader / writer, the transmission output of the reader / writer is increased, so that communication can be performed even when communication with the ID tag cannot be conventionally performed. it can.

According to the third aspect of the present invention, it is determined whether or not communication with the ID tag is possible based on the magnetic coupling degree estimated by the coupling degree acquiring means, and a warning is issued when it is determined that communication is not possible. In addition, it is possible to prevent the communication operation from being terminated while leaving the uncommunicated ID tag.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The ID tag 1 shown in FIGS. 9 and 10 is configured by incorporating the electric circuit shown in FIG. The electric circuit of the ID tag 1 includes an antenna coil 3 for transmitting and receiving a radio signal, a resonance capacitor 4, a control IC 5, and a smoothing unit 6, and the resonance capacitor 4, the control IC 5, and the smoothing unit. 6 is mounted on a printed wiring board 7.

The control IC 5 includes an MP as a control unit.
U (microprocessor unit) 8, rectifier 9,
The semiconductor elements constituting the modulation / demodulation unit 10 and the memory unit 11 are integrated into one chip. Here, the memory unit 11
Is EE as an erasable non-volatile memory for temporary storage.
It has a PROM. Although not shown, the smoothing unit 6 has a smoothing capacitor, a Zener diode, and the like.

The antenna coil 3 is connected in parallel with the resonance capacitor 4 to form a resonance circuit, and a predetermined high frequency power radio signal is transmitted from a reader / writer which is an external transmission / reception device. Is received and supplied to the rectifier 9. The rectifying unit 9 constitutes an operation power supply circuit together with the smoothing unit 6. The rectifying unit 9 rectifies an electric power radio signal transmitted from the resonance circuit, smoothes the electric power radio wave signal with the smoothing unit 6, and performs a constant voltage DC power (operation electric power). ) And MPU8
And so on.

A signal such as data transmitted from a reader / writer is transmitted while being superimposed on a power radio signal. The signal is demodulated by a modem 10 and supplied to an MPU 8. The MPU 8 has a memory unit 11
Operates according to an operation program stored in a ROM included in the memory unit 11, executes a process corresponding to a signal input from the modem unit 10, writes received data to an EEPROM included in the memory unit 11, Is read out, modulated by the modulation / demodulation unit 10, and transmitted as a radio signal from the antenna coil 3. Note that such an ID tag 1 is attached to an article in a delivery system, an inventory management system, a sales management system, or the like, and is used to identify the article.

As a reader / writer that communicates with the ID tag 1, there is a hand-held reader / writer 12 shown in FIGS. This hand-held reader / writer 12 is provided with a head 13b at the tip of an operation section 13a also serving as a grip section, and incorporates a battery 14 (see FIG. 5) as an operation power supply. A display unit 15 made of liquid crystal is provided on the front side of the head 13b.
(See FIG. 5). The operation unit 13 is provided with, for example, a plurality of key switches 16, and the key switches 16 are used to instruct operation contents and to input data.

The hand-held reader / writer 12 is provided with a main controller 17 and a remote controller 18 (corresponding to read / write means and resonance frequency changing means) as shown in FIG. The main controller 17 is connected to the group of key switches 16 via a switch circuit 19 and communicates data with the display 15 and a higher-level device (for example, a personal computer). Etc. are connected. The switch circuit 19 transmits a signal corresponding to the operated key switch to the main control unit 17. The remote control unit 18 is in charge of data communication with the ID tag 1, and includes an antenna unit 21 for transmitting and receiving a radio signal to and from the ID tag 1, and a sounding unit 22 as a warning unit such as a buzzer. Is connected.

FIG. 6 schematically shows the configuration of the main control unit 17 of the hand-held reader / writer 12. As shown in FIG. 6, the main control unit 17 includes an MPU 23, a ROM 24 storing an operation program, and a RAM 2 storing data temporarily.
5. Communication unit 26 that executes communication with remote control unit 18
It is composed of The MPU 23 processes data and controls peripheral devices. The MPU 23 executes a process according to a signal sent from the remote control unit 18 or the switch circuit 19, and also executes a process content or a process being executed. The result is displayed on the display 15.

FIG. 7 schematically shows the configuration of the remote controller 18. As shown in FIG. 7, the remote control unit 18 includes an MPU 27 as a control unit, a ROM 28 storing an operation program and the like, a RAM 29 storing data temporarily, and a communication unit 30 executing communication with the main control unit 17. , A transmission unit 31, a reception unit 32, and the like.

Here, the antenna section 21 includes a transmission antenna coil 33 and a reception antenna coil 34. The transmission antenna coil 33 is connected to the transmission section 31, and the reception antenna coil 34 is connected to the reception section 32. Have been. These two antenna coils 33 and 34 are
They are arranged in front and rear in the same direction on the front side (the right side in FIGS. 8 and 9) in the head 13b.

The MPU 27 of the remote controller 18 controls the sound generator 22 and the communication with the ID tag 1. When communicating with the ID tag 1, the MPU 27 first modulates the reference signal in the transmission unit 31 and transmits the modulated signal as a power radio signal from the transmission antenna coil 33, and then converts the data to be transmitted into a power radio signal. The signal is modulated by the transmission unit 31 so as to be superimposed and transmitted from the transmission antenna coil 33.

The radio signal transmitted from the ID tag 1 is received by the receiving antenna coil 34,
The signal is demodulated by the receiving unit 32 and discriminated as data. And
The MPU 27 of the remote control unit 18 temporarily stores the data demodulated by the receiving unit 32 in the RAM 29, and thereafter,
The data is transmitted to the main control unit 17 via the communication unit 30.

The transmitter 31 of the remote controller 18 has an automatic tuning function for automatically tuning the resonance frequency of the transmission antenna coil 33 to the frequency of the transmission signal. The automatic tuning function will be described.

First, the principle of automatic tuning will be described.
In a series resonance circuit including a coil L, a capacitor C, and a resistor R as shown in FIG. 3, a voltage difference between both ends of the coil L (corresponding to the transmission antenna coil 33) becomes a transmission output. When the resonance tuning is the same, the maximum current flows through the series resonance circuit, and the transmission output becomes maximum. At this time, the signal waveforms at both ends of the coil L are 90 ° out of phase with the waveform of the transmission signal. On the other hand, at the time of resonance non-tuning in which the frequency of the transmission signal and the resonance signal are shifted, the voltage at both ends of the coil L is lower than that at the time of resonance tuning, as shown by the broken line in FIG. At this time, the phase shift of the signal waveform at both ends of the coil L is out of 90 °. For this reason, the transmission output from the coil L decreases as compared with the time of resonance tuning.

FIG. 4 shows the relationship between the phase difference between the voltages across the coil L and the transmission output. In FIG. 4, the phase difference is 90
° and the phase difference is 90
It can be seen that the transmission output decreases as the angle deviates from the degree. Further, the phase shift between both ends of the coil L and the transmission output (resonance current)
It can be seen that there is a correlation between Therefore, by adjusting the phase shift within the allowable range by changing the capacitance of the capacitor C, automatic tuning of adjusting the resonance frequency of the transmission antenna coil 33 to the transmission frequency can be realized, and the resonance current (transmission output ) Can be adjusted to be sufficient.

FIG. 2 schematically shows the configuration of the transmitting section 31. 2, the transmission circuit 35 of the transmission unit 31 is connected to a series resonance circuit 36 and a first level conversion circuit 37, and transmits a reference signal (transmission signal) of a predetermined frequency to the series resonance circuit 36 and the first level conversion circuit 37. Output to the level conversion circuit 37. The series resonance circuit 36 includes the transmission antenna coil 33
And the resonance capacitor circuit 38 are connected in series.

The resonance capacitor circuit 38 is constituted by connecting a reference capacitor 39 and a correction circuit 40 in parallel, and the capacitance of the entire resonance capacitor circuit 38 is equal to the capacitance of the reference capacitor 39. It is a value obtained by adding the capacitance of the application circuit 40. The correction circuit 40 includes a plurality of first to n-th unit circuits 41 connected in parallel. One unit circuit 41 includes a capacitor 41a (corresponding to a correction capacitor) and a capacitor 41b (corresponding to a correction capacitor). ) Are connected in series, and a switch 41c is connected in parallel with the capacitor 41b. Therefore, the capacitance of the entire correction circuit 40 and the capacitance of the resonance capacitor circuit 38 are determined according to the on / off state of the switch 41c of each unit circuit 41.

Here, if the capacitance of the capacitors 41a and 41b in each unit circuit 41 is set to the same capacitance, for example, 2C, the switch 41c
When the switch is turned on, the capacitance of the unit circuit 41 becomes C. When the switch 41c is on, the capacitance of the unit circuit 41 becomes 2C.
The capacitance of 1 can be increased from C to 2C by C.

When the correction circuit 40 is composed of the first to sixth unit circuits 41, the capacitances of the capacitors 41a and 41b in the first to sixth unit circuits 41 are 64C and 32C, respectively. , 16C, 8C, 4C, and 2C, respectively. Therefore, when the switches 41c of the first to sixth unit circuits 41 are independently turned on, the capacitance of the entire correction circuit 40 becomes 32C,
It increases by 16C, 8C, 4C, 2c, and 1C. This means that the capacitance of the entire correction circuit 40 can be adjusted in the range of 0 to 63C in units of 1C according to the combination pattern of the ON / OFF states of the switches 41c of each unit circuit 41.

In this case, the correction circuit 40 is designed so that the series resonance circuit 36 is in resonance tuning with the switch 41c of the first unit circuit 41 turned on. This is because, by setting the resonance frequency of the series resonance circuit 36 as a design value at the center of the frequency adjustable range of the correction circuit 40, when increasing or decreasing the capacitance of the correction circuit 40, the increase or decrease of the frequency is corrected. This is to make it work effectively.

The resonance capacitor circuit 3 having the above-described configuration is used.
8, a voltage dividing circuit 42 is connected in parallel. The voltage dividing circuit 42 includes a capacitor 42a and a capacitor 42b connected in series, and the capacitor 42a and the capacitor 42b are connected in series.
It outputs the voltage level at the common connection point to the second level conversion circuit 43 to the second level conversion circuit 43, and has a small capacitance so as not to affect the capacitance of the resonance capacitor circuit 38. .

The first and second level conversion circuits 37 and 43 convert an input signal into a binary signal, and output the binary signal to an exclusive OR circuit 44. The exclusive OR circuit 44 outputs an exclusive OR of the binary signals input from the first and second level conversion circuits 37 and 43 to the phase difference voltage conversion circuit 45. The exclusive OR circuit 44 outputs a phase difference signal indicating the phase difference between the reference signal from the transmission circuit 35 and the resonance signal of the series resonance circuit 36. When the phases of both signals do not match, the phase difference signal is output. And outputs a pulse-shaped phase difference signal indicating the magnitude and phase difference direction.

The phase difference voltage conversion circuit 45 converts the phase difference signal output from the exclusive OR circuit 44 into a voltage indicating the phase difference and the direction of the phase difference, and performs a transmission tuning deviation judgment circuit 46.
(Corresponding to transmission tuning deviation acquisition means). The transmission tuning deviation determination circuit 46 determines the phase difference and the phase difference direction based on the voltage output from the phase difference voltage conversion circuit 45.
(Capacitor) Outputs to the on / off control circuit 47 (corresponding to counting means) and the MPU 27. Then, the C on / off control circuit 47 controls the on / off of the switch 41 c of the unit circuit 41 of the correction circuit 40 so that the signal phase difference between both ends of the transmission antenna coil 33 becomes 9
The capacitance of the series resonance circuit 36 is adjusted so as to be 0 °. Further, the MPU 27 determines whether or not frequency tuning has been performed based on a signal from the transmission tuning deviation determination circuit 46 (tuning determining means).

Here, the inductance value of the transmission antenna coil 33 changes depending on the surrounding environment, in particular, the relationship between the transmission antenna coil 33 and the antenna coil 3 of the ID tag 1 electromagnetically coupled to the transmission antenna coil 33. The inductance value of the antenna coil 33 changes. That is, the transmitting antenna coil 33 and the antenna coil 3 of the ID tag 1
When the distance to the distance increases, the inductance value increases.
Therefore, the distance from the ID tag 1 is detected by detecting the inductance value of the transmission antenna coil 33, or whether the ID tag 1 is in a state where it can receive operable power from the power radio signal. Can be detected.

Therefore, when the frequency tuning is completed, the MPU 27 obtains on / off information for each switch 41c of the resonance capacitor circuit 38 from the C sound off control circuit 47, and obtains the capacitance of the resonance capacitor circuit 38 from the on / off information. I want to ask. And MP
U 27 calculates the inductance value of the transmission antenna coil 33 based on the capacitance of the resonance capacitor circuit 38.

Next, the operation of the above configuration is applied to a case where data is read from the ID tag 1, and a description will be given with reference to a flowchart shown in FIG. When the read switch of the operation unit 13a is operated, the remote control unit 18, in other words, the MPU 27 determines "YES" in step S1, and in the next step S2, outputs a small output for measurement from the transmission antenna coil 33. Then, an automatic tuning operation command is given to the C on / off control circuit 47 in the following step S3.

When giving an automatic tuning operation command, the MPU 27
Controls the C on / off control circuit 47 so that only the switch 41c of the first unit circuit 41 of the correction circuit 40 is turned on, and the capacitance of the correction circuit 40 is within the capacitance correctable range. To be adjusted in the middle of

Although the series resonance circuit 36 is designed to be in a resonance state (tuned state) with the maximum current corresponding to the output of the reference signal from the transmission circuit 35, the transmission antenna of the handheld reader / writer 12 The inductance value of the use coil 33 changes by being magnetically coupled to the antenna coil 3 of the ID tag 1 or the like. Since the resonance frequency of the transmission antenna coil 33 is determined by the inductance and the capacitance of the resonance capacitor, when the inductance value of the transmission antenna coil 33 changes, the resonance frequency of the transmission antenna coil 33 changes.

Therefore, in the present embodiment, the MPU 27 detects the signal phase difference between both ends of the transmission antenna coil 33 based on the determination result by the transmission tuning deviation determination circuit 46 of the transmission unit 31, so that the phase difference is reduced. It is determined whether it is within the reference range (synchronization determination means). At this time, if the phase difference between the reference signal and the resonance signal exceeds the allowable range, it is determined that the resonance is not in the tuning state, and the switching command is given to the C on / off control circuit 47. Thereby, the on / off pattern of the switch of the correction circuit 40 is switched in a short time, and the resonance frequency of the transmission antenna coil 33 approaches the frequency of the reference signal. When the phase difference between both ends of the transmitting antenna coil 33 falls within a predetermined range, it is determined that the resonance tuning state has been established.

When the resonance tuning state is established in this way, M
The PU 27 reads the capacitance of the resonance capacitor from the switching information of the C on / off control circuit 47 (the on / off pattern information of the switch of the correction circuit 40) in step S4, and in the next step S5, the inductance value of the transmission antenna coil 33. (Inductance value acquisition means). Then, the MPU 27 compares the inductance value of the transmission antenna coil 33 obtained by this calculation with the reference value, and determines whether communication with the ID tag 1 is possible, in other words, the transmission antenna coil 33 and the ID.
The degree of magnetic coupling between the tag 1 and the antenna coil 3 is estimated, and it is determined whether or not the degree of coupling can transmit operation power to the ID tag 1 (step S6; degree of coupling obtaining means, determining means).

Next, when communication with the ID tag 1 is possible,
The MPU 27 makes “YES” in the step S6 and shifts to the step S7. In step S7, the MPU 27 obtains an output corresponding to the inductance value by, for example, an operation, and calculates the output level based on the output level.
3 outputs a radio signal. As a result, the ID tag 1 obtains a sufficient operation power from the operation radio signal, and outputs identification information in response to a request from the handheld reader / writer 12. When reading the identification information from the ID tag 1 (step S8), the MPU 27 of the hand-held reader / writer 12 outputs
2 to notify that it has been received (step S9),
End.

On the other hand, as shown in FIG. 9, the ID tag 1 is located far away from the handheld reader / writer 12,
As shown in FIG. 10, the antenna coil 3 of the ID tag 1
Is the transmitting antenna coil 33 of the handheld reader / writer 12
If it is not parallel to the magnetic flux output from
Since the inductance value of the transmitting antenna coil 33 has a level indicating that communication is not possible, the MPU 27 determines “NO” in step S6, and proceeds to step S10.

The MPU 27 determines in step S10 that the tone generator 2
2 to notify that communication is not possible and return to step S3.
5. In step S6, "N0", the operations of step S10 and step S3 are repeatedly executed. Then, the user knows that the communication is not possible by the notification sound of the sound generator 22, and moves the handheld reader / writer 12 closer to the ID tag 1 or changes the direction of the handheld reader / writer 12. Then, since the communication becomes possible, the MPU 27 determines “YES” in step S6, executes the operations in and after step S7, and ends.

As described above, according to this embodiment, the degree of magnetic coupling between the transmission antenna coil 33 and the antenna coil 3 of the ID tag 1 is estimated by calculating the inductance value of the transmission antenna coil 33. It can be determined whether communication is possible.

When it is determined that communication is possible, a radio signal is transmitted with an output value corresponding to the inductance value.
There is no waste such as transmitting a radio signal with a large output even when the ID tag 1 is nearby, and power is saved. Further, when it is determined that communication is not possible, a warning is issued from the sound generation unit 22 to that effect, so that the handheld reader / writer 12 can be brought close to the ID tag 1 or the direction of the handheld reader / writer 12 can be changed so that communication can be performed immediately. There is no possibility of terminating the communication while leaving the uncommunicated ID tag 1.

The present invention is not limited to the embodiment described above and shown in the drawings, but can be extended or modified as follows. When transmitting a radio signal with an output corresponding to the inductance value, the output value may be obtained by calculation, or the inductance value and the output value may be stored as data in advance, and the data may be obtained by referring to the data. The warning means may be displayed on the display unit 15. The reader / writer is not limited to the handheld type,
It may be a fixed type.

[Brief description of the drawings]

FIG. 1 is a flowchart showing control contents according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating an outline of an electrical configuration of a transmission unit.

FIG. 3 is a circuit diagram and a signal waveform diagram for explaining a resonance state of the resonance circuit.

FIG. 4 is a diagram showing a relationship between a signal phase difference between both ends of a coil and a transmission output.

FIG. 5 is a block diagram showing an electrical configuration of the handheld reader / writer.

FIG. 6 is a block diagram illustrating an electrical configuration of a main control unit.

FIG. 7 is a block diagram showing an electrical configuration of a remote control unit.

FIG. 8 is a block diagram showing an electrical configuration of the ID tag.

FIG. 9 is a diagram showing an example of a state in which communication between an ID tag and a handheld reader / writer is disabled.

FIG. 10 is a diagram showing another example of a state in which communication between the ID tag and the handheld reader / writer is disabled.

[Explanation of symbols]

In the figure, 1 is an ID tag, 3 is an antenna coil, 12 is a hand-held reader / writer, 18 is a remote control unit (inductance value acquisition unit, coupling degree acquisition unit, determination unit, control unit), and 22 is a sound generation unit (warning). Means).

Claims (3)

[Claims] 1. An ID tag reader / writer having read / write means for reading / writing data from / to an ID tag, wherein when communicating with the ID tag, obtaining an inductance value for obtaining an inductance value of a transmission antenna composed of a coil. A reader / writer for an ID tag, comprising: means; and coupling degree acquiring means for estimating a degree of magnetic coupling with the ID tag based on the inductance value obtained by the inductance value acquiring means. 2. The reader / writer for an ID tag according to claim 1, further comprising control means for controlling an output of said transmitting antenna in accordance with a magnetic coupling degree estimated by said coupling degree acquiring means. . 3. A determining means for determining whether communication with the ID tag is possible based on the magnetic coupling degree estimated by the coupling degree obtaining means, and a warning when the determining means determines that communication is impossible. The reader / writer for an ID tag according to claim 1 or 2, further comprising a warning unit for issuing an ID tag.