JP2011191889A - Remote detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To configure a remote detection system, using small-sized tags and having a longer communication distance. <P>SOLUTION: A remote detection system 101 includes a reader/writer 30, active tags 40A, 40B and passive tags 50A to 50F. The reader/writer 30 communicates with the active tags 40A, 40B and reads detection data acquired by the active tags 40A, 40B. The active tags 40A, 40B detect the sensing information of the respective passive tags 50A to 50C, 50D to 50F, and transmits these data to the reader/writer 30. Each of the passive tags 50A to 50C, 50D to 50F includes a resonance circuit, resonating in a frequency band of radio waves for communication performed between the active tags 40A, 40B and the reader/writer 30, and an antenna connected to the resonant circuit. The active tags 40A, 40B analyze the frequency of reflected signals from the passive tags 50A to 50C, 50D to 50F and acquires the sensing information. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a remote detection system using an RF-ID tag.

  Conventionally, for example, Patent Literature 1 and Patent Literature 2 are disclosed as related to the RF-ID technology.

  In the data communication system of Patent Document 1, a relay reader / writer is provided between a data carrier and a main body reader / writer. The relay reader / writer is disposed close to the data carrier, and data communication is performed between the data carrier and the main body reader / writer via the relay reader / writer. The relay reader / writer has a built-in battery, and is configured such that the power switch is turned on when the data carrier is mounted on the relay reader / writer.

  In the wireless response device of Patent Document 2, a non-powered transponder is configured by a SAW-ID tag having an impedance converter. FIG. 1 is a block diagram showing the configuration of the state detection system of Patent Document 2. As shown in FIG. The state detection system 1 includes a transceiver 10 and a state detection sensor 20 that is a wireless response device. The transceiver 10 transmits a question signal to the state detection sensor 20 via the antenna 11. Further, the transceiver 10 receives the response signal transmitted from the state detection sensor 20 via the antenna 11. The state detection sensor 20 is a sensor (passive sensor) that operates without power supply. The impedance converter 22 converts changes in the surrounding state such as external force and light into impedance changes. Since the impedance of the impedance converter 22 changes depending on the surrounding state and the impedance matching state between the antenna 21 and the identification signal generator 23 changes, the state detection sensor 20 outputs a response signal corresponding to the surrounding state. become.

JP 2001-127672 A JP 2007-18492 A

  Since Patent Document 1 is a system in which a data carrier having a non-volatile memory performs data communication with power of a received signal, the carrier needs functions such as modulation / demodulation of memory data, received signal-voltage conversion, and the configuration is complicated. There is a problem of becoming large. Further, the relay reader / writer only relays the memory data to the main body reader / writer, and only has an effect of increasing the communication distance between the carrier and the main body reader / writer.

  The configuration of Patent Document 2 is a non-power supply SAW transponder in which an impedance converter is used for a sensor or the like with SAW as an ID. However, when SAW is used as an ID, an ID is assigned based on a “0” or “1” determination based on the presence or absence of IDT in the transversal type. Since the transversal type SAW has a larger loss than the resonator type SAW, characteristics such as a communication distance cannot be expected in the first place. Further, as the number of digits of the ID is increased, the number of IDTs increases and the distance of the IDT reciprocation increases, so that the loss further increases. In addition, since the impedance greatly affects the communication distance, the method of reading the change in the impedance affects whether it can be read or not, and is not stable as a system. Since the configuration for ID and the sensor are separately provided, it is disadvantageous for miniaturization.

  An object of the present invention is to provide a remote detection system that solves the above-described problems and uses a small tag and has a long communication distance.

  The remote detection system of the present invention is a remote detection system that includes an active tag and a reader that communicates with the active tag, and that resonates in a frequency band of communication radio waves between the active tag and the reader. A passive tag including a circuit and an antenna connected to the resonance circuit is provided. The active tag includes an antenna, a transmission / reception circuit, a demodulation circuit, a control circuit, an ID circuit, and a power supply circuit. The passive tag is remotely connected by a transponder method. Means for detecting and including information of the passive tag in communication information with the reader.

  With this configuration, the wireless communication between the active tag and the reader device and the transponder communication between the passive tag and the active tag effectively work with each other, using a small passive tag and transponder communication. Can communicate over long distances.

  If the resonance circuit of the passive tag includes a sensor element whose resonance frequency changes according to the detection amount, or the sensor element itself, the detection content of the passive sensor tag can be read by a reader.

  In addition, if the distance of the wireless communication between the active tag and the reader is made longer than the distance of the transponder communication between the active tag and the sensor tag, the passive tag can be used at a longer distance than the conventional transponder communication. Become.

The resonant circuit is, for example, a SAW device.
The antenna is formed of, for example, a film and a radiation electrode formed on the film, and the resonance circuit is provided on the film.
For example, the antenna and the resonance circuit of the passive tag are hermetically sealed.

  According to the present invention, the output of a passive tag having a relatively short communication distance can be detected by a transponder method using the communication radio wave between the reader and the active tag. In addition, long-distance one-to-many multipoint detection can be performed by wireless communication between a reader having a relatively long communication distance and an active tag. That is, the active tag method and the passive tag method are merged.

  Therefore, remote detection using a passive tag is possible even in the range exceeding the effective communication distance of the passive tag transponder system. Moreover, since the passive tag does not require an ID circuit, the passive tag is small and lightweight and easy to manufacture.

  For example, when remotely detecting body temperature in a hospital, wireless detection can be performed together with temperature information and ID information (for example, position information in the hospital) from active tags in the vicinity of the body temperature detection sensor tag among a plurality of active tags. Furthermore, the information of a plurality of active tags can be concentrated on the reader by wireless communication with the reader.

It is a block diagram which shows the structure of the state detection system of patent document 2. FIG. It is a block diagram of the remote detection system 101 of this invention. FIG. 3A is a block diagram showing a configuration of the reader / writer 30 shown in FIG. FIG. 3B is a block diagram showing a configuration of the active tag 40A shown in FIG. FIG. 3C is a block diagram showing a configuration of the passive tag 50A shown in FIG. 4A is a plan view of the passive tag 50A, and FIG. 4B is a front sectional view of the passive tag 50A. It is a figure which shows the frequency spectrum of the transmission signal and reflected signal between an active tag (40A, 40B) and a passive tag (50A-50F). FIG. 6A is a flowchart showing the processing contents of the control circuit 31 of the reader / writer 30 shown in FIG. FIG. 6B is a flowchart showing the processing contents of the control circuit 41 of the active tag 40A shown in FIG.

The remote detection system of the present invention will be described with reference to FIGS.
FIG. 2 is a block diagram of the remote sensing system 101 of the present invention. The remote detection system 101 includes a reader / writer 30, active tags 40A and 40B, and passive tags 50A to 50F. The reader / writer 30 communicates with the active tags 40A and 40B and collects the detection data acquired by the active tags 40A and 40B.

  The active tag 40 </ b> A detects the sensing information of each of the passive tags 50 </ b> A to 50 </ b> C and transmits (responds) those data to the reader / writer 30. Further, the active tag 40A itself performs predetermined sensing and transmits (responds) the information to the reader / writer 30. Similarly, the active tag 40B detects the sensing information of each of the passive tags 50D to 50F, and transmits (responds) those data to the reader / writer 30. Further, the active tag 40B itself performs predetermined sensing and transmits (responds) the information to the reader / writer 30.

  The passive tags 50A to 50C and 50D to 50F include a resonance circuit that resonates in a frequency band of communication radio waves between the active tags 40A and 40B and the reader / writer 30, and an antenna connected to the resonance circuit.

  The remote detection system 101 illustrated in FIG. 2 collects detection data by the active tags 40A and 40B and detection data by the passive tags 50A to 50C via the active tags 40A and 40B. In this example, since the passive tags 50A to 50C are separated from the active tag 40B by a certain distance, the active tag 40B is not affected by the passive tags 50A to 50C. Similarly, since the passive tags 50D to 50F are separated from the active tag 40A by a certain distance, the active tag 40A is not affected by the passive tags 50D to 50F.

  FIG. 3A is a block diagram showing a configuration of the reader / writer 30 shown in FIG. FIG. 3B is a block diagram showing a configuration of the active tag 40A shown in FIG. FIG. 3C is a block diagram showing a configuration of the passive tag 50A shown in FIG. The configuration of the active tag 40B is the same as that of the active tag 40A. The configuration of the passive tags 50B to 50F is basically the same as that of the passive tag 50A.

  As shown in FIG. 3A, the reader / writer 30 includes an antenna 35, a transmission / reception circuit 34, a modulation / demodulation circuit 33, a control circuit 31, a memory 32, and an interface circuit 36. The transmission / reception circuit 34 performs transmission and reception with the active tags 40A and 40B via the antenna 35. The modem circuit 33 modulates the transmission signal and demodulates the reception signal. The control circuit 31 transmits various commands as serial signals to the modulation / demodulation circuit 33, thereby transmitting predetermined commands to the active tags 40A and 40B. Further, the control circuit 31 receives the demodulated signal from the modulation / demodulation circuit 33, distinguishes the detection data for each passive tag and active tag, and writes (collects) it in the memory 32. Further, the control circuit 31 communicates with an external circuit via the interface circuit 36 via a cable, and outputs detection data to the outside.

  As shown in FIG. 3B, the active tag 40A includes an antenna 48, a transmission / reception circuit 47, a modulation / demodulation circuit 46, a control circuit 41, a power supply circuit 42, a memory 43, a sensor 44, and an ID circuit 45. The transmission / reception circuit 47 performs transmission and reception with the reader / writer 30 for the active tag via the antenna 48. The modem circuit 46 modulates the transmission signal to the reader / writer 30 and demodulates the reception signal. The modem circuit 46 also detects reflected signals from the passive tags 50A to 50C. The sensor 44 is, for example, a temperature sensor, a humidity sensor, a gas sensor, or the like. The ID circuit 45 is a circuit that generates unique information used by the reader / writer 30 to identify an active tag.

  When all necessary sensing is performed with a passive tag, it is not necessary to provide such a sensor 44 on the active tag. The memory 43 is not necessarily provided outside the control circuit 41.

The control circuit 41 transmits the detection data to the reader / writer 30 by outputting the detection data as a serial signal to the modulation / demodulation circuit 46. The control circuit 41 receives a demodulated signal from the modulation / demodulation circuit 46, identifies a command from the reader / writer 30, and performs processing according to the command. If it is a response request command for detection data, a serial signal obtained by assigning an ID to already acquired detection data is output to the modem circuit 46. The control circuit 41 further reads the frequency information of the reflected signals from the passive tags 50A to 50C detected by the modulation / demodulation circuit 46, and acquires the sensing information of the passive tags 50A to 50C. For example, since the frequencies of the reflected signals of the passive tags 50A to 50C are individually set, the passive tag 50A to 50C is detected from which passive tag by detecting the frequency, and the frequency is detected. Information is written to the memory 43 as detection data.
As described above, the control circuit 41 includes means for including information on the passive tag in the information transmitted to the reader / writer 30.

As shown in FIG. 3C, the passive tag 50A includes a SAW device 54 and antenna radiation electrodes 52A and 52B to form a SAW transponder. The SAW device 54 constitutes a resonance circuit including a piezoelectric substrate and an IDT electrode formed on the piezoelectric substrate. The radiation electrodes 52A and 52B constitute a dipole antenna and are connected to the resonance circuit.
In place of the dipole antenna, an antenna such as a loop antenna or a monopole antenna may be used.

  The reflection state of the radio wave transmitted from the active tag 40A differs depending on the resonance frequency of the resonance circuit of the passive tag 50A. The active tag 40A detects the sensing information of the passive tags 50A to 50C by detecting the frequency of the reflected signal.

  4A is a plan view of the passive tag 50A, and FIG. 4B is a front sectional view of the passive tag 50A. The passive tag 50A includes a base film 51, a SAW device 54, and a sealing film 59. On the upper surface of the base film 51, radiation electrodes 52A and 52B are formed. In the SAW device 54, an IDT electrode 56 and reflection electrodes 57A and 57B are formed on a piezoelectric substrate 55 such as lithium niobate or lithium tantalate, and a 2-terminal 1-port resonance circuit is configured. The resonance frequency of this resonance circuit is, for example, a frequency band of 860 MHz to 960 MHz. The resonance frequency of the resonance circuit has a constant coefficient with respect to temperature. That is, the resonance frequency changes according to the ambient temperature.

  Strictly speaking, the resonance frequency of the passive tag 50A is a resonance frequency of a circuit constituted by the resonance circuit of the SAW device 54 and the radiation electrodes 52A and 52B, but substantially the resonance frequency of the resonance circuit of the SAW device 54. Equal to frequency.

  The SAW device 54 is mounted on the upper surface of the base film 51, and two terminals of the SAW device are connected to the radiation electrodes 52A and 52B. The sealing film 59 is attached to the entire upper surface of the base film 51 on which the SAW device 54 is mounted, and the SAW device and the radiation electrodes 52A and 52B are sealed by the sealing film 59 and the base film 51. ing. With such an airtight sealed package structure having moisture resistance, the passive tag can be used even in a high humidity environment.

  A double-sided pressure-sensitive adhesive sheet and a release paper are attached to the back surface (outer bottom surface) of the base film 51 as necessary. For example, the release paper is peeled off and a passive tag 50A is attached to a predetermined part of the patient, thereby acting as a sensor tag for detecting body temperature.

  FIG. 5 is a diagram illustrating a frequency spectrum of a transmission signal and a reflection signal between the active tags (40A, 40B) and the passive tags (50A to 50F). In FIG. 5, the curve thru is the spectrum of the transmission signal of the active tag, the curve SAW is the spectrum of the reflected signal from other than the SAW device in the passive tag, the curve Rev is the spectrum of the reflected signal from the SAW device in the passive tag, and the curve NWA is It is a waveform of the insertion loss of the SAW device in a passive tag.

  In this example, the frequency of the transmission signal of the active tag 40A (the frequency when the passive tag 50A does not exist or the resonance operation of the resonance circuit of the passive tag 50A does not affect) ft is 868 MHz, and the resonance circuit of the passive tag 50A. The resonance frequency fr is about 868 MHz + 100 kHz.

  The range of change of the resonance frequency of the passive tag exists in the main band of the frequency of the transmission signal of the active tag 40A (867 to 869 MHz in the example shown in FIG. 5). Therefore, the passive tags (50A to 50F) receive transmission signals from the active tags (40A, 40B) and transmit (reflect) reflected signals according to the resonance frequency.

  As described above, when the passive tag 50A exists in the near field of the active tag 40A, the frequency of the reflected signal received by the active tag 40A is shifted. Therefore, the active tag 40A detects the frequency of the reflected signal, and the passive tags 50A to 50A. The resonance frequency of 50C, that is, sensing information is detected.

  FIG. 6A is a flowchart showing the processing contents of the control circuit 31 of the reader / writer 30 shown in FIG. FIG. 6B is a flowchart showing the processing contents of the control circuit 41 of the active tag 40A shown in FIG.

  As shown in FIG. 6A, the reader / writer 30 transmits a command for requesting detection data to the active tag at a fixed timing or irregular timing. Subsequently, detection data transmitted (response) from the active tag is received and stored in a predetermined format in the memory. As already described, the detection data includes sensing information of the passive tags 50A to 50F detected by the active tag.

  As shown in FIG. 6B, the active tags (40A, 40B) detect the presence / absence of a received signal, and if there is a received signal, determine whether it is any request command from the reader / writer 30. To do. If it is a detection data transmission request, the already acquired detection data is transmitted to the reader / writer 30. At the same time, the sensing information of each passive tag is acquired by analyzing the frequency of the reflected signal from the passive tag. Then, the detection data is written into the memory in preparation for the next transmission.

  As shown in FIG. 3B, the active tag according to the present invention includes a transmission / reception circuit 47 and a modulation / demodulation circuit 46 for communicating with a reader / writer, so that a passive tag (SAW) for a transmission signal to the reader / writer is provided. Receiving and analyzing the reflected signal of the transponder) is substantially performed by the signal processing of the control circuit 41. That is, since the transmission / reception circuit 47 and the modulation / demodulation circuit 46 are already provided, it is only necessary to add a function of analyzing the reflected signal from the passive tag to the signal processing by the control circuit of the active tag having the conventional configuration. Therefore, it is possible to construct a highly efficient remote detection system without substantially increasing the circuit scale of the active tag.

  In the active tag according to the present invention, since the frequency band used by the active tag and the passive tag can be shared, for example, [A] communication between the active tag and the reader, and [B In the communication between the active tag and the passive tag, the antenna, the transmission / reception circuit, the demodulation circuit, and the control circuit, which are the configurations of the active tag, can be shared. On the other hand, if different frequency bands are used for the above-mentioned [A] and the above-mentioned [B], if the above configuration is shared, the efficiency of wireless communication (radio wave transmission / reception) is reduced and the communication distance is shortened. Or, in order to maintain the efficiency of wireless communication, a predetermined frequency band is selected from a signal using a filter element, a duplexer element, a switch element, etc., and a demultiplexing circuit, a multiplexing circuit, a filtering circuit, etc. It is necessary to add frequency selection means to the active tag.

  Therefore, the number of components caused by circuit sharing is reduced as compared with the case where the frequency band used by the active tag and the passive tag is not shared in this way. Thereby, the miniaturization of the apparatus and the manufacturing process can be simplified.

  In addition, since the number of circuits in the apparatus can be reduced by sharing the circuits, the length of wiring connecting the circuits can be shortened. Therefore, the area for arranging the wiring can be reduced, so that the apparatus can be miniaturized. Furthermore, the noise that external electromagnetic waves jump into the wiring can be reduced by shortening the wiring length. Therefore, the electromagnetic wave noise tolerance of the device is increased.

  Since each passive tag is identified by the ID of the active tag, an ID circuit is not required for each passive tag, there is no signal attenuation due to the provision of the ID circuit, and the reflected signal is transmitted (reflected) from the passive tag. As a result, the transponder communication distance can be made longer than when an ID circuit is provided.

  In addition, if moisture is a problem when sensing a specific part, it is difficult to make the whole moisture-resistant structure because of its size and number of parts, but if it is a passive tag, only the sensor (chip) is used. Since it may be mounted in an airtight sealed package, it can be easily realized.

  According to the remote detection system described above, for example, when the body temperature is remotely detected in a hospital, the active tag arranged in the vicinity of the passive tag for body temperature detection among the plurality of active tags arranged is passive. The ID information (for example, position information in the hospital) of the active tag is transmitted to the reader / writer 30 together with the body temperature information obtained from the tag. Thus, body temperature information of a plurality of patients in a hospital can be centrally managed using a body temperature detection passive tag that is small, lightweight, and easy to manufacture (disposable).

<< Other embodiments >>
The embodiment described above shows an example in which the passive tag is a sensor tag that performs predetermined sensing. However, the embodiment can be similarly applied to the case where the presence / absence of a passive tag is detected. In this case, the active tag detects the presence / absence of a reflected signal from the passive tag, and thereby detects the presence / absence of the passive tag.

  In the above example, the transmission signal from the reader / writer is reflected by the passive tag, and the frequency of the reflected signal is detected. However, the SAW device generated after the transmission signal from the reader / writer is terminated. The detection data may be acquired by detecting the frequency of the transmission signal due to the reverberation of.

  In the example described above, the temperature dependence of the SAW device is positively used as a temperature sensor. In addition, the SAW device has a resonance frequency that varies depending on pressure, magnetic field, atmosphere, and the like. If it is comprised, it can be used as a sensor tag of a pressure sensor, a magnetic sensor, or a gas sensor, and these detections can be performed centrally remotely by a reader / writer.

  In the above embodiment, the reader / writer has been described so as to communicate wirelessly with the active tag. However, since writing some data to the active tag is not an essential function, it may simply be a “reader”. .

DESCRIPTION OF SYMBOLS 30 ... Reader / writer 31 ... Control circuit 32 ... Memory 33 ... Modulation / demodulation circuit 34 ... Transmission / reception circuit 35 ... Antenna 36 ... Interface circuit 40A, 40B ... Active tag 41 ... Control circuit 42 ... Power supply circuit 43 ... Memory 44 ... Sensor 45 ... ID circuit 46 ... Modulation / demodulation circuit 47 ... Transmission / reception circuit 48 ... Antennas 50A to 50F ... Passive tag 51 ... Base film 52A, 52B ... Radiation electrode 54 ... SAW device 55 ... Piezoelectric substrate 56 ... IDT electrodes 57A, 57B ... Reflection electrode 59 ... Sealing film 101 ... Remote detection system

Claims (7)

In a remote detection system including an active tag and a reader that communicates with the active tag,
A passive tag including a resonance circuit that resonates in a frequency band of a communication radio wave made between the active tag and the reader, and an antenna connected to the resonance circuit;
The active tag includes an antenna, a transmission / reception circuit, a demodulation circuit, a control circuit, an ID circuit, and a power supply circuit. The passive tag is remotely detected by a transponder method, and information on the passive tag is included in information transmitted to the reader. A remote sensing system including means.   The remote detection system according to claim 1, wherein the resonance circuit of the passive tag includes a sensor element whose resonance frequency changes according to a detection amount, or is the sensor element itself.   The control circuit of the active tag detects a signal generated when a radio wave transmitted to the reader is reflected by the passive tag, and communicates information of the passive tag with the reader using an ID by the ID circuit. The remote detection system according to 1 or 2.   The remote detection system according to any one of claims 1 to 3, wherein a communication distance between the active tag and the reader is longer than a communication distance between the active tag and the sensor tag.   The remote detection system according to claim 1, wherein the resonance circuit is a SAW device.   The remote detection system according to claim 1, wherein the antenna is formed of a film and a radiation electrode formed on the film, and the resonance circuit is provided on the film.   The remote detection system according to claim 1, wherein the antenna and the resonance circuit of the passive tag are hermetically sealed.

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