JP2000231609A - Reader writer for id tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a resonance current from decreasing owing to a resonance frequency shift of a transmitting antenna. SOLUTION: A resonance capacitor circuit 39 which forms a series resonance circuit 3 together with the transmitting antenna 3 is constituted by connecting a reference capacitor 40 and a correcting circuit 42 composed of unit circuits 42 in parallel. Each unit circuit 42 is constituted by connecting a capacitors 42a and a capacitor 42b in series and connecting a switch 42c to the capacitor 42b in parallel. In this case, the electrostatic capacity of a unit circuit 42 can be increased by turning on the switch 42c according to the bit pattern of a register 48a of a capacitor on/off control circuit 48, so an MPU(microprocessor unit) 28 is able to adjust the eleetrostatic capacity of the resonance capacitor circuit 39 by varying the bit pattern of the register 48a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reader / writer for an ID tag having a reading / writing means for reading / writing data from / to an ID tag.

[0002]

2. Description of the Related Art For example, as a system for identifying a moving object,
A remote ID system using radio waves is provided.
In this apparatus, communication between a controller and an ID tag is performed by radio waves, and data of an ID tag at a remote position is read or data is written to the ID tag.

[0003] Such a remote ID system is considered to be applied to various systems such as a delivery system, an inventory management system, and a sales system. As an example, there is a tallying system for a rotating sushi shop. The outline of this system is that the ID tag embedded in the plate on which sushi is placed stores data such as the type of sushi, the time it was made, the selling price, and when the customer finished eating, the sushi plate was put on The ID tag reader / writer communicates with the ID tag of each dish to accumulate sushi fees.

[0004]

However, the inductance of the coil constituting the transmitting antenna of the ID tag reader / writer changes due to the interaction with the surrounding environment and the built-in substrate. Since the resonance frequency of the coil is determined by the inductance and the resonance capacitor, when the inductance changes, the resonance frequency of the transmitting antenna fluctuates accordingly. When the resonance frequency of the transmission antenna fluctuates in this way, when the Q value is large, the resonance current decreases, the power supplied to the ID tag decreases, and the communication performance deteriorates. In this case, if the transmission output is increased, the communication performance is improved, but the power consumption is increased.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the resonance current without increasing the transmission output and deteriorate the communication performance even when the resonance frequency of the transmission antenna fluctuates. I can prevent that
An object of the present invention is to provide a reader / writer for a D tag.

[0006]

According to the first aspect of the present invention, when a transmission signal is supplied to a transmission antenna, a radio wave is transmitted from the transmission antenna to the ID tag. Can read and write.

Incidentally, the inductance of the coil constituting the transmitting antenna changes due to the interaction with the surrounding environment and the built-in substrate. Since the resonance frequency of this coil is determined by the inductance and the resonance capacitor, the resonance frequency of the transmission antenna fluctuates due to the change in inductance.

Here, the transmission tuning deviation judging means detects a frequency deviation between the resonance frequency of the transmission antenna and the resonance frequency of the transmission antenna. At this time, the read / write means changes the resonance frequency of the transmitting antenna by the resonance frequency changing means when the frequency shift determined by the transmission tuning shift determining means is outside the allowable range. When the frequency shift detected by the transmission tuning shift determining means falls within the allowable range, reading and writing for the ID tag is executed. As a result, in the resonance tuning state where the maximum resonance current flows through the transmitting antenna, the ID
Since reading and writing can be performed on the tag, it is possible to prevent the communication area of the transmitting antenna from being reduced.

According to the second aspect of the present invention, since the transmitting antenna is composed of a coil constituting a series resonance circuit together with the resonance capacitor, the phase shift of the signal waveform at both ends of the coil is 90 ° in the resonance tuning state. On the other hand, as the state deviates from the resonance tuning state, the phase shift of the signal waveform at both ends of the coil deviates from 90 °. Thereby, the transmission tuning deviation determining means can determine the frequency deviation based on the deviation of the signal waveform at both ends of the coil.

According to the third aspect of the present invention, since the resonance capacitor is constituted by a plurality of correction capacitors exhibiting different capacitances according to the connection pattern, the resonance frequency changing means changes the connection pattern of the capacitor. By changing, the capacitance of the resonance capacitor can be changed to change the resonance frequency of the transmission antenna.

According to the fourth aspect of the present invention, since the connection pattern of the plurality of correction capacitors corresponds to the bit pattern of the register, the resonance frequency changing means writes the predetermined bit pattern in the register to perform the correction. The connection pattern of the capacitor can be changed.

According to the fifth aspect of the present invention, the counting means increases or decreases the register value according to the clock input so that the bit pattern of the register becomes a bit pattern in which the frequency shift is within an allowable range. The connection pattern can be changed continuously, and the resonance frequency of the transmission antenna can be made to coincide with the frequency of the transmission signal in a short time.

According to the sixth aspect of the present invention, the storage means stores the relationship between the frequency deviation of the transmitting antenna and the magnitude of the resonance current of the transmitting antenna. The resonance frequency of the transmission antenna for obtaining the required resonance current is recognized by reading the resonance current stored in the storage means corresponding to the frequency deviation detected by the means, and the resonance frequency of the transmission antenna is changed. Thereby, the resonance current can be controlled.

According to the seventh aspect of the invention, when communicating with a plurality of ID tags and communicating with the maximum resonance current, all ID tags can be communicated, but the power consumption required for the communication is low. growing. Therefore, since the read / write means communicates with a preset small resonance current, sequentially increases the resonance current, and finally communicates with the maximum resonance current, it is possible to reduce the consumption of the built-in battery and prolong the operation time. Can be.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. Note that this embodiment is applied to a tallying system for a revolving sushi restaurant. here,
The rotating sushi shop is a shop having the following system.

[0016] A loop conveyor is provided in the store,
A table and seats are provided along the conveyor. Sushi is placed on a plate and transported to the audience by a conveyor. The customer takes a dish on which a favorite sushi is placed from among the dishes carried by the conveyor, and after eating, the dishes are sequentially stacked on the table. The shop places the sushi on a plate of a color or pattern corresponding to the selling price, so that the customer can know the approximate amount to be paid to the store from the stacked plates and the number of plates.
After the meal, the clerk counts the number of dishes for each color or pattern, and determines the amount to be paid to the store.

As shown in FIG. 2, the dish 1 on which sushi is placed is made of plastic such as ABS resin, for example, and has an ID tag 2 embedded therein. As shown in FIG. 3, the ID tag 2 includes an antenna coil 3 for transmitting and receiving a radio signal, and a resonance capacitor 4.
, A control IC 5, and a smoothing unit 6. The resonance capacitor 4, the control IC 5, and the smoothing unit 6 are 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. 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. When a radio wave signal of a predetermined high frequency is transmitted from a reader / writer which is an external device, Receiving this, the rectification unit 9
Send to 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 signal by the smoothing unit 6, and performs a DC voltage (operating electric power) of a constant voltage. ) And supply it to the MPU 8 and the like.

A signal such as data transmitted from a reader / writer is transmitted by being superimposed on a power radio signal, and the signal is demodulated by a modulation / demodulation unit 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, and stores received data in an erasable non-volatile memory such as an EEPROM included in the memory unit 11. It writes or reads data from the memory unit 11, modulates it with the modem unit 10, and transmits it as a radio signal from the antenna coil 3.

As a reader / writer for communicating with the ID tag 2 of the plate 1, there is a hand-held reader / writer 12 shown in FIG. The hand-held reader / writer 12 includes an operation unit 13 also serving as a grip unit, for example, a display unit 14 made of liquid crystal, and a battery 15 as an operation power supply (see FIG. 5).
Built-in. The operation unit 13 is provided with, for example, a plurality of key switches 16. The key switches 16 are used to instruct operation contents and to input basic data necessary for totaling, for example, unit prices of the dishes 1 by type. It has become. The operation unit 13 is provided with a tallying key switch 17 for instructing a tallying process in addition to the key switches 16 described above.

The hand-held reader / writer 12 is provided with a main controller 18 and a remote controller 19 (corresponding to read / write means and resonance frequency changing means) as shown in FIG. The main control unit 18 is connected to the key switch 16 group and the tallying key switch 17 via a switch circuit 20, and the display unit 14
A communication unit 21 for exchanging data with a higher-level device (for example, a personal computer) is connected. The switch circuit 20 transmits a signal corresponding to the operated key switch to the main control unit 18. The remote control unit 19 is in charge of data communication with the ID tag 2, and is connected to an antenna unit 22 for transmitting and receiving a radio signal to and from the ID tag 2, and a sounding unit 23 such as a buzzer. I have.

FIG. 6 schematically shows the configuration of the main controller 18 of the hand-held reader / writer 12. In FIG.
The main control unit 18 includes an MPU 24, a ROM 25 storing an operation program, a RAM 26 temporarily storing data,
It comprises a communication unit 27 that executes communication with the remote control unit 19 and the like. The MPU 24 processes data and controls peripheral devices. The MPU 24 executes a process corresponding to a signal sent from the remote control unit 19 or the switch circuit 20, and also executes a process content or a process being executed. The result is displayed on the display 14.

FIG. 7 schematically shows the configuration of the remote control unit 19. In FIG. 7, the MPU 28,
R storing an operation program and a database described later
It comprises an OM 29, a RAM 30 for temporarily storing data, a communication unit 31 for executing communication with the main control unit 18, and the like. The MPU 28 controls communication with the ID tag 2 and controls the sound generator 23. When performing communication with the ID tag 2, first modulates the carrier signal in the transmitter 32 to reduce the power. Transmission antenna 3 as radio signal for
3, and then the data to be transmitted is modulated by the transmission unit 32 so as to be superimposed on the power radio signal, and transmitted from the transmission antenna 33.

The radio signal transmitted from the ID tag 2 is received by the receiving antenna 34, demodulated by the receiving unit 35 and discriminated as data. Then, the MPU 28 of the remote control unit 19 temporarily stores the data demodulated by the receiving unit 35 in the RAM 30, and then transmits the data to the main control unit 18 via the communication unit 31. I have. In the communication with the ID tag 2 performed under the control of the remote control unit 19, when the communication mode is the multi-read mode as the multi-mode, during the execution of the communication, the remote control unit 19. 23 is controlled so as to emit an operation sound “pip”.

The multi-read mode refers to a mode in which the antenna unit 22 communicates with all ID tags 2 present in a communication area. The communication mode includes a single read mode and a single write mode in addition to the multi-read mode. This single read mode is
This is a mode for designating the ID number of the D tag 2 and reading data from the ID tag of the ID number. The single write mode is a mode for designating the ID number of the ID tag 2 and This is a mode for writing data.

The transmitting section 32 of the remote control section 19 has an automatic tuning function for automatically tuning the resonance frequency of the transmitting antenna 33 to the frequency of the transmission signal. Will be described.

First, the principle of automatic tuning will be described.
In a series resonance circuit including a coil L and a capacitor R as shown in FIG. 8, a voltage difference between both ends of the coil L (corresponding to the transmission antenna 33) becomes a transmission output. At the time of tuning, the maximum current flows through the series resonance circuit, the transmission output becomes maximum, and the phase shift of the signal waveform at both ends of the coil L at this time is 90 °.
It is. 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 one end of the coil L is lower than that at the time of resonance tuning, as indicated 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.

Here, in FIG. 9 showing the relationship between the phase difference of the voltage between both ends of the coil L and the transmission output, the transmission output becomes maximum when the phase difference is 90 °, and the phase difference deviates from 90 °. It can be seen that the transmission output has decreased. Also,
It can be seen that there is a correlation between the phase shift at both ends of the coil L and the transmission output (resonance current). Therefore, by adjusting the phase shift within the allowable range, the resonance current can be adjusted to the resonance frequency of the transmission antenna 33 at which the transmission output becomes sufficient, and automatic tuning can be realized.

FIG. 1 schematically shows the configuration of the transmitting section 32. In FIG. 1, a transmission circuit 36 of a transmission unit 32 is connected to a series resonance circuit 37 and a first level conversion circuit 38, and transmits a reference signal (transmission signal) of a predetermined frequency to the series resonance circuit 37 and the first level conversion circuit 38. The signal is output to the level conversion circuit 38. This series resonance circuit 37 is configured by connecting a transmission antenna 33 and a resonance capacitor circuit 39 in series.

The resonance capacitor circuit 39 is configured by connecting a reference capacitor 40 and a correction circuit 41 in parallel, and the capacitance of the entire resonance capacitor circuit 39 is equal to the capacitance of the reference capacitor 40. It is a value obtained by adding the capacitance of the application circuit 41. The correction circuit 41 includes a plurality of first to n-th unit circuits 42 connected in parallel. One unit circuit 42 includes a capacitor 42a (corresponding to a correction capacitor) and a capacitor 42b (corresponding to a correction capacitor). ) And the capacitor 4
A switch 42c is connected in parallel to 2b.
Accordingly, the capacitance of the entire correction circuit 41 and the capacitance of the resonance capacitor circuit 39 are determined according to the on / off state of the switch 42c of each unit circuit 42.

Here, if the capacitance of the capacitor 42a and the capacitor 42b in each unit circuit 42 is set to the same capacitance, for example, 2C, the capacitance of the unit circuit 42 becomes C when the switch 42e is off. When the switch 42c is on, the capacitance of the unit circuit 42 is 2
C, the unit circuit 42 is turned on when the switch 42 is turned on.
Can be increased from C to 2C by C.

When the correction circuit 41 is composed of the first to sixth unit circuits 42, the capacitances of the capacitors 42a and 42b in the first to sixth unit circuits 42 are 64C and 32C, respectively. , 16C, 8C, 4C, and 2C, respectively. Accordingly, when the switches 42c of the first to sixth unit circuits 42 are independently turned on, the capacitance of the entire correction circuit 41 becomes 32C,
It increases by 16C, 8C, 4C, 2c, and 1C. This means that the capacitance of the entire correction circuit 41 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 42c of each unit circuit 42.

In this case, the correction circuit 41 is designed so that the series resonance circuit 37 is in resonance tuning with the switch 42c of the first unit circuit 42 turned on. This is because the resonance frequency of the series resonance circuit 37 is set as a design value at the center of the adjustable frequency range of the correction circuit 41 so that the increase or decrease of the capacitance of the correction circuit 41 can be corrected. This is to make it work effectively.

The resonance capacitor circuit 3 having the above configuration
9, a voltage dividing circuit 43 is connected in parallel. The voltage dividing circuit 43 is composed of a capacitor 43a and a capacitor 43b connected in series.
It outputs the voltage level at the common connection point to the second level conversion circuit 44 to the second level conversion circuit 44, and has a small capacitance so as not to affect the capacitance of the resonance capacitor circuit 39. .

The first and second level conversion circuits 38 and 44 convert an input signal into a binary signal, and output the binary signal to an exclusive OR circuit 45. The exclusive OR circuit 45 outputs the exclusive OR of the binary signals input from the first and second level conversion circuits 38 and 44 to the phase difference voltage conversion circuit 46. The exclusive OR circuit 45 outputs a phase difference signal indicating the phase difference between the reference signal from the transmission circuit 36 and the resonance signal of the series resonance circuit 37. When the phases of both signals do not match, the phase difference signal is output. And outputs a pulse-like phase difference signal indicating the magnitude and direction of the phase difference.

The phase difference voltage conversion circuit 46 converts the phase difference signal output from the exclusive OR circuit 45 into a voltage indicating the phase difference and the phase difference direction, and converts the signal into a transmission tuning deviation determination circuit 47.
(Corresponding to transmission tuning deviation determination means).

The transmission tuning deviation determination circuit 47 outputs the transmission tuning deviation and the direction of the deviation to a C (capacitor) on / off control circuit 48 (corresponding to a counting means) based on the voltage output from the phase difference voltage conversion circuit 46. This C
The on / off control circuit 48 adjusts the capacitance of the series resonance circuit 37 so as to eliminate the signal phase difference between both ends of the transmission antenna 33 by controlling on / off of the switch 42c of the unit circuit 42 of the correction circuit 41.

The C on / off control circuit 48 has a register 48a. This register 48a is composed of 6 bits corresponding to the first to sixth unit circuits 42 of the correction circuit 41, and the corresponding switch 42c in the correction circuit 41 is turned on / off according to the on / off of the corresponding bit. It has become.
In this case, the C on / off control circuit 48
When a bit pattern is given from 28, the capacitance of the correction circuit 41 is continuously adjusted by increasing or decreasing the count value of the register 48c in accordance with the clock input so that the bit pattern is obtained. Has become.

On the other hand, a power saving mode is set in the handheld reader / writer 12. In the power saving mode, when performing communication with the ID tag 2 built in the plate 1, communication is performed in a state where power consumption is suppressed. In other words, as a result of the above-described automatic tuning, the communication with the ID tag 2 is performed with the maximum power by communicating with the ID tag 2 with the maximum power, but the power consumption is large and the consumption of the battery 15 is reduced. Battery 15
The transmission power is suppressed in order to suppress the consumption of power.
Although it is possible to suppress the transmission power by suppressing the power of the transmission signal from the transmission circuit 36 as described above, the configuration of the transmission circuit 36 becomes complicated and the cost increases. In the embodiment, the transmission power is suppressed as follows.

That is, the data table shown in FIG. 10 is stored in the ROM 29 of the remote control unit 19 of the hand-held reader / writer 12. In this data table, predetermined numerical values are set corresponding to the reference power saving mode, the power saving mode 1, the power saving mode 2, and the maximum power mode. Here, the reference power saving mode, the power saving mode 1 and the power saving mode 2 are modes in which communication with the ID tag 2 is performed in a state where the current flowing through the series resonance circuit 37 is suppressed, and the maximum power mode is the series resonance mode. In this mode, communication with the ID tag 2 is performed in a resonance tuning state in which the maximum current flows through the circuit 37. In this case, the numerical value stored in the data table indicates the deviation of the capacitance in the correction circuit 41 at the time of the maximum current. That is, when the capacitance of the capacitor in the first unit circuit 42 of the correction circuit 41 is 64C, the capacitance of the correction circuit 41 is reduced by 6C from the capacitance at the maximum current in the reference power saving mode. Set to
In the power saving mode 1, the capacitance is set to decrease by 4C from the capacitance at the maximum current. In the power saving mode 2, the capacitance is set to decrease by 2C from the capacitance at the maximum current. The capacitance is set to be the capacitance at the time of current.

By adjusting the capacitance of the correction circuit 41, the deviation of the resonance frequency in the reference power saving mode from the resonance frequency at the time of the maximum current becomes maximum, and subsequently, the power saving mode 1 and the power saving mode 2 It becomes in order. The resonance frequency in the maximum power mode matches the resonance frequency at the time of the maximum current.

FIG. 11 shows a C on / off control circuit 48.
1 shows an example of a bit pattern written to a register 48a of the register 48a. In FIG. 11, when the bit pattern of the register 48a at the time of the maximum current (at the time of resonance tuning) is, for example, "100000" by the automatic tuning, the correction circuit 41 at the time of the maximum current is required to execute the reference power saving mode. 6C from the capacitance of
The bit pattern of the register 48a is “011010” obtained by subtracting “6” from “100000”. To execute the power saving mode 1, the capacitance of the correction circuit 41 at the time of the maximum current needs to be reduced by 4 C. Therefore, the bit pattern of the register 48a is obtained by subtracting “4” from “100000” to “011100”. ". To execute the power saving mode 2, the capacitance of the correction circuit 41 at the time of the maximum current needs to be reduced by 2 C. Therefore, the bit pattern of the register 48a is obtained by subtracting “2” from “100000” to “011111”. ". In order to execute the maximum power mode, the capacitance of the correction circuit 41 at the time of the maximum current may be set as the capacitance.
Is assumed to be "100000".

Next, the operation of the above configuration will be described with reference to the flowcharts shown in FIGS. In addition,
12 and 13 show only the counting operation of the hand-held reader / writer 12, and other operations are omitted for simplification of description.

In order to total the payment amount of the customer who has finished the meal, the key switch 17 for totaling with the hand-held reader / writer 12 facing the plate 1 stacked on the table of the customer as shown in FIG. Operate.

Then, a signal corresponding to the tallying key switch 17 is input from the switch circuit 20 to the main controller 18, and the MPU 24 decodes the signal input from the switch circuit 20. In this case, the input signal from the switch circuit 20 is a tally command signal (S101: YE
S), since this instructs communication with the ID tags 2 of all dishes 1 that the customer has finished eating, the remote control unit 19
The MPU 28 sets an initial bit pattern in the register 48a of the C on / off control circuit 48 to start communication with the ID tag 2 (S102), and then starts supplying a reference signal (S103). That is, for example, “1” is stored in the register 48a of the C on / off control circuit 48.
00000 "is set. Thereby, the correction circuit 4
Only the switch 42c of the first first unit circuit 42 is turned on, and the capacitance of the correction circuit 41 is adjusted to the middle of the capacitance correctable range. Outputs a reference signal having a predetermined period. As a result, the series resonance circuit 37 is brought into a resonance state by the reference signal.

Incidentally, the series resonance circuit 37 is
Although it is designed to be in a resonance state (resonance tuning state) at the maximum current according to the output of the reference signal from 6,
The inductance of the transmitting antenna 33 of the hand-held reader / writer 12 may change due to the interaction with the surrounding environment or a built-in board. Since the resonance frequency of the transmission antenna 33 is determined by the self-inductance and the resonance capacitor 41, the resonance frequency of the transmission antenna 33 may fluctuate due to a change in the inductance. If the resonance frequency of the transmission antenna 33 fluctuates in this way, the resonance current decreases when the Q value is large, and the power supplied to the ID tag 2 decreases with this, resulting in deterioration in communication performance. I will. In this case, if the transmission output is increased, the communication performance is improved, but the power consumption is increased.

Therefore, in the present embodiment, the resonance current of the transmitting antenna 33 is prevented from lowering without increasing the transmission output in the following manner. That is, the MPU 28 of the remote control unit 19 detects the signal phase difference between both ends of the transmission antenna 33 based on the determination result by the transmission tuning deviation determination circuit 47 of the transmission unit 32, and determines whether the phase difference is within the reference range. Judgment (S10
5). At this time, if the reference signal and the resonance signal have a phase difference exceeding the allowable range, it is determined that the current is not the maximum current in the resonance tuning state (S105: NO), and the next is stored in the register 48a of the C on / off control circuit 48. Is set (S116). In this case, the transmission tuning deviation determination circuit 47 determines the frequency deviation and the deviation direction of the reference signal and the resonance signal based on the phase difference between the reference signal and the resonance signal, so that the MPU 28 cancels the deviation. The bit pattern of the register 48a of the C on / off control circuit 48 is changed.

At this time, the C on / off control circuit 4
8, when a bit pattern is given by a command from the MPU 28, the register 48a is increased or decreased so as to have a command value in accordance with the input of the clock so that the bit pattern becomes the bit pattern. Thereby, the on / off pattern of the switch of the correction circuit 41 is switched in a short time, and the series resonance circuit 37 is switched.
, Rapidly approaches the frequency at which the resonance current becomes the maximum current. When the phase difference falls within the predetermined range, it is determined that the maximum current has reached the resonance tuning state (S10).
5: YES), the current C on / off control circuit 48
Is stored in the RAM 30 (S106).

When the ID tag 2 is read at the time of the maximum current in the resonance tuning state as described above, all the ID tags 2 located in the communication area by the antenna section 22, that is, all the stacked plates 1 Although the ID tag 2 can be read, the power consumption until the entire ID tag 2 is read becomes large, and the battery 15 is greatly consumed. Therefore, in this embodiment, the ID tag 2 is read as follows. 2
To reduce the power consumption in the read operation.

That is, when reading the ID tag 2, the MPU first executes the reference power consumption mode (S1).
07). In the reference power consumption mode, a bit pattern “011010” obtained by subtracting “6” from the bit pattern “100000” stored at the time of resonance tuning is written in the register 48 a of the C on / off control circuit 48. As a result, the capacitance of the correction circuit 41 becomes 6 C from the maximum current.
Therefore, the frequency of the series resonance circuit 37 greatly deviates from the resonance frequency, and the transmission output of the hand-held reader / writer 12 is reduced from the maximum current and the communicable area is reduced. As a result, as shown in FIG. 14, the number of plates 1 located in the communicable area of the handheld reader / writer 12 is reduced.

Subsequently, it is determined whether the total command signal from the switch circuit 20 is a multi-read command (S
108). At this time, since the aggregation command signal is a multi-read command (S108: YES), the MPU 24 of the main control unit 18 performs communication in the multi-read mode in order to communicate with all ID tags 2 located in the communicable area. The command is transmitted to the remote control unit 19.

Then, the MPU 28 of the remote control unit 19
Starts communication in the multi-read mode (S10
9) That is, while transmitting the power radio signal, the sound generator (buzzer) 23 is driven, and then the multi-read command signal is transmitted while being superimposed on the power radio signal (S11).
0).

Therefore, the sound generator 23 emits an operating sound "beep" simultaneously with the transmission of the power radio signal.
The clerk knows that the counting operation has started, and fixes the handheld reader / writer 12 so as not to move.

On the other hand, by starting communication in the multi-read mode, the ID tag 2 side of the plate 1 receives the power radio signal by the antenna coil 3 and rectifies and smoothes the radio signal by the rectifier 9 and the smoother 6. The MPU 8 converts the power into DC power of a constant voltage and supplies it as power for operating the MPU 8 or the like.

The supply of the operation power causes the MPU 8 of the ID tag 2 of each plate 1 to start operation and determine the type of the transmitted command. In this case, since the transmitted command is a multi-read command, the antenna unit 22
The MPU 8 performs an operation of reading data such as the ID number and the type of the dish 1 from the memory unit 11, modulating the data with the modem 10, and transmitting the data from the antenna coil 3.

The radio signal transmitted from each ID tag 2 as described above is received by the receiving antenna 34 of the handheld reader / writer 12, and the received signal is received by the receiving unit 35.
, And the demodulated data is temporarily stored in the RAM 30 (S111). The reception of the radio signal transmitted from the ID tag 2 is performed until the radio signals from the ID tags 2 of all the dishes 1 existing in the communication area by the antenna unit 22 are received (see FIG. 14).

Here, determination as to whether or not the radio signals from the ID tags 2 of all the dishes 1 present in the communication area by the antenna unit 22 have been received is performed, for example, as follows. That is, as shown in FIG.
The MPU 28 of No. 9 repeatedly transmits the multi-read command at a fixed time interval, and divides the transmission section of the multi-read command into, for example, ten time slots.

On the other hand, when the MPU 8 of the ID tag 2 receives the multi-read command, the MPU 8 first determines the position of the time slot for transmitting a signal in response to the multi-read command by setting its own ID number to 1
Is determined. For example, three ID tags 2a, 2b, and 2c exist in a communication area of the antenna unit 22, and their ID numbers are 121, 132, and 14, respectively.
2, the three ID tags 2a, 2
b and 2c determine the number of time slots to be 1, 2, and 2, respectively.

Therefore, when the first multi-read command is transmitted from the remote control unit 19, a response signal to the first multi-read command is transmitted by the ID tag 2a in the first time slot, and the ID tags 2b and 2c transmit the response signal in the second time slot. Make a call in the time slot. ID tag 2 transmitted in the first time slot is 1
Since there are only one ID tag 2a, the radio signal transmitted from the ID tag 2a is received by the remote control unit 19, and the ID tag 2a receives a signal indicating that the ID tag 2a has been received from the remote control unit 19. However, the ID tags 2b, 2c
Are transmitted in the second time slot, the response signals collide and are not received by the remote control unit 19.

When the second multi-read command is transmitted from the remote control unit 19, the ID tags 2b and 2c
This time, the time slot position to be transmitted is set to ID number 10
, That is, the ID tag 2b of the ID number 132 determines the number of time slots to be 3 and the ID number 1
The 42 ID tags 2c determine the number of time slots to be four. For this reason, the response signals of the ID tags 2b and 2c
It is transmitted in the third and fourth time slots after the second multi-read command is transmitted. in this case,
ID tag 2 transmitted in the third and fourth time slots
Is only one each, so that the ID tags 2b, 2
The radio signal transmitted from c is received by the remote controller 19, and the ID tags 2 and 2b receive a signal from the remote controller 19 to the effect that the signal has been received.

Next, a third multi-read command is transmitted from the remote control unit 19. Then, three IDs
Since the tags 2a, 2b, and 2c have already received the signal indicating that the response signal has been received, they do not respond to the third multi-read command. Therefore, the remote control unit 19
Communicated with all the ID tags 2 existing in the communication area by the antenna unit 22 because the response signal was not received until the time of 10 time slots elapsed after the transmission of the third multi-read command. Judge.

When reading of all readable ID tags 2 is completed in the reference power saving mode as described above (S112: YES), it is confirmed that power saving mode 1 is not being executed (S112). (S113: NO), in the state where the power saving mode 1 is executed (S119), the multi-read mode is executed (S109-). That is, the bit pattern “10000” stored at the time of the maximum current at the time of resonance tuning is used.
Bit pattern “011010” obtained by subtracting 4 from “0”
Is written into the register 48a of the C on / off control circuit 48. As a result, the capacitance of the correction circuit 41 increases by 2C as compared with the reference power saving mode, and the frequency of the resonance signal of the series resonance circuit 37 approaches the resonance frequency to increase the current. 33, the transmission output increases, and the communicable area expands. As a result,
ID tag 2 located in communication area by antenna unit 22
Increase (see FIG. 14).

In the power saving mode 1, similarly to the reference power saving mode, reading of all readable ID tags 2 located in the communication area by the antenna unit 22 is executed in the multi-read mode. At this time, since the ID tag 2 which has been communicated in the reference power saving mode does not execute communication in the power saving mode 1, the communication time with the ID tag 2 in the power saving mode 1 can be short.

When reading of all communicable ID tags 2 is completed by executing the power saving mode 1 (S112:
(YES), after confirming that the power saving mode 2 is not executed (S114: NO), the multi-read mode is executed while the power saving mode 2 is executed (S120) (S109-). That is, the bit pattern “011010” obtained by subtracting 2 from the bit pattern “100000” stored at the time of the maximum current during resonance tuning is written to the register 48 a of the C on / off control circuit 48. As a result, the capacitance of the correction circuit 41 becomes larger by 2C than in the power saving mode 1, and the series resonance circuit 37
Since the frequency of the resonance signal approaches the resonance frequency and the current increases, the transmission output of the transmission antenna 33 further increases, and the communicable area expands. As a result, the antenna unit 2
2 further increases the number of ID tags 2 located in the communication area.

When reading of all communicable ID tags 2 is completed by executing the power saving mode 2 (S112:
(YES), after confirming that the maximum power mode is not being executed (S115: NO), the multi-read mode is executed with the maximum power mode being executed (S121) (S109-). That is, the bit pattern “100000” stored at the time of the maximum current in the resonance tuning state is written in the register 48 a of the C on / off control circuit 48. As a result, the capacitance of the correction circuit 41 increases by 2C as compared with the reference power saving mode, and the frequency of the resonance signal of the series resonance circuit 37 approaches the resonance frequency to increase the current. The transmission output of 33 further increases, and the communicable area expands. As a result, all the ID tags 2 come to be located in the communication area of the antenna unit 22.

Therefore, the ID tag 2 in the maximum power mode
Is completed, the tag data of all the ID tags 2 contained in the stacked dishes 1 can be read.

When the reception of the radio signals from the ID tags 2 of all the dishes 1 has been completed (S115: YES), the MPU 28 of the remote control unit 19 terminates the multi-read communication and drives the sound generation unit 23. Stop. For this reason,
Since the sounding section 23 stops the sounding operation of “beep, beep”, the clerk knows that the counting operation has been completed.

When the main control unit 18 causes the remote control unit 19 to perform communication by an operation other than the operation of the tallying key switch 17, the mode is the single read mode or the single write mode (S108: N
O), the remote control unit 19 transmits a single read command or a single write command (S117), and the ID tag 2 of the designated ID number transmits data to the remote control unit 19 or transmits data from the remote control unit 19 to the remote control unit 19. It is received (S118).

According to the present embodiment,
The difference between the frequency of the reference signal and the frequency of the resonance signal of the series resonance circuit 37 is obtained by the automatic tuning function of the handheld reader / writer 12, and the correction circuit 41 is adjusted so that the difference is eliminated and the resonance current becomes maximum. Since the capacitance is adjusted, even if the resonance frequency of the series resonance circuit 37 deviates from the design value, the communication area of the antenna unit 22 can be reduced without increasing the transmission output of the reference signal. Prevent and prevent all IDs built into the stacked dishes 1
Tag data can be reliably read from the tag 2.

When communication with the ID tag 2 is performed, the capacitance of the correction circuit 41 is adjusted so that the resonance frequency is shifted from the resonance frequency at the maximum current in the resonance tuning state to a low power state. Executes communication with the ID tag 2 and all communicable IDs located in the communication area.
Each time the communication with the tag 2 is completed, the communication with the ID tag 2 is performed in a low power state in which the resonance frequency approaches the resonance frequency at the maximum current in order, and finally the maximum power at the resonance frequency at the maximum current is used. Since the communication with the ID tag 2 is performed, compared to the configuration in which communication with all the ID tags 2 is performed with the maximum power, the power consumption until the communication with all the ID tags 2 is completed is reduced. Can be suppressed.

Since the capacitance of the correction circuit 41 is adjusted based on the bit pattern of the register 48a of the C on / off control circuit 48, the capacitance of the correction circuit 41 can be easily adjusted. it can.

Further, the capacitance of the correction circuit 41 is set to the first value.
Can be finely controlled every 1/64 of the capacitance of the capacitor of the unit circuit 42, so that the capacitance of the correction circuit 41 is accurately adjusted so that the resonance current of the series resonance circuit 37 is maximized. be able to.

In the flowchart shown in FIG.
As a method for matching the resonance frequency of the transmission antenna 33 to the transmission frequency, a method in which the MPU determines whether the frequency deviation is within the reference range and sets the bit pattern has been described.
It is also possible to implement without a PU. That is, two output signals in the increasing direction and the decreasing direction of the determination circuit 47 are counted by a clock having a cycle determined as an input of the up / down counter. In this case, the capacitor on / off control circuit 48 shown in FIG. 1 is configured using an up / down counter.

The present invention is not limited to the embodiment described above and shown in the drawings, but can be extended or modified as follows. The target article on which the ID tag 2 is provided is not limited to the sushi plate 1, but can be widely applied to clothing, jewelry, delivered luggage, and the like. The present invention is not limited to the calculation of the payment amount, and can be widely applied to inventory, delivery destination management, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an electrical configuration of a transmitting unit of a hand-held tag reader according to an embodiment of the present invention.

FIG. 2 is a perspective view of a dish with a built-in ID tag.

FIG. 3 is a block diagram showing an electrical configuration of the ID tag.

FIG. 4 is a diagram showing a reading / writing state by a handheld reader / writer.

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

FIG. 9 is a diagram showing a relationship between a signal phase difference between both ends of a coil and a transmission output.

FIG. 10 is a diagram showing a table storing numerical values corresponding to each mode;

FIG. 11 is a diagram showing a correspondence between each mode and a bit pattern;

FIG. 12 is a flowchart showing the operation of the hand-held reader / writer (part 1).

FIG. 13 is a flowchart showing the operation of the handheld reader / writer (part 2).

FIG. 14 is a schematic diagram showing a communication process for a plurality of ID tags by a handheld reader / writer.

FIG. 15 is a diagram showing communication timing in a multi-read mode.

[Explanation of symbols]

2 is an ID tag, 12 is a handheld reader / writer, 17 is a key switch for counting, 18 is a main control unit, 19 is a remote control unit (read / write means, resonance frequency changing means), 37 is a series resonance circuit, and 32 is a transmission. Reference numeral 33 denotes a transmission antenna, 39 denotes a resonance capacitor circuit, 47 denotes a transmission tuning deviation determination circuit (transmission tuning deviation determination means), 48 denotes a capacitor on / off control circuit (counting means), and 48a denotes a register.

Continued on the front page F term (reference) 3E042 AA04 BA17 5B058 CA15 KA40 YA01 5J070 AK40 BC06 BC29 BC36 9A001 CC05 CC09 JZ52 JZ53 JZ54 KK31

Claims (7)

[Claims] An ID tag reader / writer including a read / write unit for reading / writing data from / to an ID tag detects a frequency shift between a resonance frequency of a transmission antenna and a transmission signal supplied to the transmission antenna. And a resonance frequency changing unit that changes a resonance frequency of the transmission antenna, wherein the read / write unit is configured to set the frequency deviation detected by the transmission tuning deviation determination unit within an allowable range. A reader / writer for an ID tag, wherein reading and writing are performed in a state where the resonance frequency of the transmitting antenna is changed by the resonance frequency changing means. 2. The transmission antenna includes a coil forming a series resonance circuit together with a resonance capacitor, and the transmission tuning deviation determination unit determines a frequency deviation based on a phase deviation of a signal waveform at both ends of the coil. The reader / writer for an ID tag according to claim 1, wherein: 3. The resonance capacitor includes a plurality of correction capacitors provided so as to exhibit different capacitances according to connection patterns, and the resonance frequency changing unit includes a connection pattern of the correction capacitors. 3. The resonance frequency of the transmission antenna is changed by changing the resonance frequency.
A reader / writer for the described ID tag. 4. A register having a rewritable bit pattern, wherein the correction capacitor is provided so that a connection pattern is changed in accordance with a bit pattern of the register. 4. The ID according to claim 3, wherein a connection pattern of the capacitor is changed by writing a predetermined bit pattern into the ID.
Reader / writer for tags. 5. A counting means for increasing / decreasing a register value according to a clock input so that a bit pattern of the register becomes a bit pattern having a frequency shift within an allowable range. ID tag reader / writer. 6. A storage means for storing a correspondence between a frequency deviation of the transmission antenna and a magnitude of a resonance current of the transmission antenna, wherein the resonance frequency changing means includes a frequency deviation detected by the transmission tuning deviation determination means. Recognizing a resonance frequency of a transmission antenna for obtaining a resonance current having a sufficient transmission output by reading a resonance current stored in the storage means in response to the above, and changing the resonance frequency of the transmission antenna The reader / writer for an ID tag according to any one of claims 1 to 5, wherein the resonance current is controlled by: 7. The read / write means, when communicating with a plurality of ID tags, communicates with a preset small resonance current,
The reader / writer for an ID tag according to any one of claims 1 to 6, wherein the resonance current is sequentially increased, and communication is performed last with the maximum resonance current.