JP4282618B2 - Active wireless tag and driving method thereof - Google Patents

Description

  The present invention relates to an active wireless tag incorporating a battery used as an operating power source and a driving method thereof.

  Wireless tags include a passive wireless tag that does not incorporate a battery and an active wireless tag that incorporates a battery. FIG. 6 shows a configuration example of a conventional passive wireless tag system. In the figure, the wireless tag 61 is in a standby state until it enters the communication area of the reader 62. When it enters the communication area of the reader 62, it receives supply of necessary power and clock from the reader 62 and Send and receive data with.

  FIG. 7 shows a configuration example of the active wireless tag. In the figure, the active wireless tag has a built-in battery 71 used as an operating power supply, and the wireless transmission circuit 72 receives power from the battery 71 and receives predetermined data (for example, ID information of the wireless tag) from the antenna 73 as a reader ( Send to (not shown). Here, in order to reduce power consumption and reduce the frequency of battery replacement, or to eliminate the need for battery replacement, the wireless transmission circuit 72 has a transmission schedule determined by a power on / off signal output from the transmission schedule management circuit 74. It is controlled and operates intermittently. For example, when the transmission schedule management circuit 74 is set to send a power-on signal to the wireless transmission circuit 72 every few seconds, the wireless tag intermittently operates every few seconds to transmit a predetermined signal. Become.

However, the radio frequency control in the radio transmission circuit 72 and the transmission schedule control in the transmission schedule management circuit 74 are performed based on a high-accuracy periodic signal from the crystal oscillator 75. Therefore, the transmission schedule management circuit 74 and the crystal oscillator 75 need to be always operated.
By Klaus Finkenzeller, RFID Handbook, published by Nikkan Kogyo Shimbun, May 31, 2004

  The passive wireless tag system must supply power used for wireless transmission from the reader side by radio waves. For this reason, in order to obtain electric power required by the wireless tag, it has been impossible to increase the distance between the wireless tag and the reader.

  On the other hand, in the case of an active wireless tag, it is not necessary to receive power supply from the reader, so the distance from the reader can be increased, and application to a use different from the passive wireless tag system is possible. However, it is necessary to always operate the transmission schedule management circuit 74 and the crystal oscillator 75 for managing the transmission schedule, and reduction of power consumption has been a problem.

  An object of the present invention is to provide a low-power active wireless tag and a driving method thereof that enable intermittent operation without using a transmission schedule management circuit.

  The present invention relates to a wireless transmission circuit that transmits a predetermined signal using a battery as an operating power source and an active wireless tag including a first antenna, the second antenna that receives the predetermined radio wave, and the second antenna that receives the signal. A generator that generates power by receiving energy supply from radio waves, and a voltage detection circuit that detects an output voltage of the generator and outputs a power on / off signal to the wireless transmission circuit in accordance with the output voltage. The detection circuit outputs a power-on signal to the wireless transmission circuit when the output voltage of the generator exceeds a predetermined threshold, and the wireless transmission circuit receives a first signal from the battery as an operating power source by the input of the power-on signal. After that, the reset signal is output to the voltage detection circuit, and the voltage detection circuit resets the generator output voltage to 0 by the input of the reset signal and outputs the power off signal. Output line transmission circuit, radio transmission circuit is configured to stop the operation to cut off the power supply from the battery by input of a power off signal.

  The voltage detection circuit includes a Schmitt trigger circuit that inputs the output voltage of the generator, and outputs a power-on signal using the battery as an operating power source when the output voltage exceeds a predetermined threshold.

  It also has a crystal oscillator that uses a battery as an operating power source and outputs a predetermined periodic signal used for radio frequency control of the radio transmission circuit. The crystal oscillator operates intermittently according to the power on / off signal output from the voltage detection circuit. It is good also as composition to do.

  In addition, the second antenna receives a radio signal periodically or constantly transmitted from a radio wave source as a predetermined radio wave.

  The first antenna and the second antenna may be configured as one antenna that transmits and receives radio waves in the same band.

  The present invention relates to a method for driving an active wireless tag including a wireless transmission circuit that transmits a predetermined signal using a battery as an operating power source and a first antenna, and energy from a radio wave received by a second antenna that receives the predetermined radio wave. When the power is generated by the generator and the output voltage of the generator exceeds a predetermined threshold, a power-on signal is output to the wireless transmission circuit. The wireless transmission circuit operates the battery by inputting the power-on signal. A predetermined signal is transmitted from the first antenna, a reset signal is output thereafter, the output voltage of the generator is reset to 0 by the reset signal, and a power off signal is output to the wireless transmission circuit. The power supply from the battery is cut off by the input of the power off signal to stop the operation.

  The present invention can intermittently operate a wireless tag without using a transmission schedule management circuit by using an electromotive force of a power generator that generates power by the energy of a received radio wave as a transmission trigger of the wireless tag. Thereby, an active wireless tag with extremely low power can be realized.

  FIG. 1 shows a configuration example of an active wireless tag according to the present invention. In the figure, a wireless transmission circuit 11 and a crystal oscillator 12 receive power from a battery 13 and transmit a predetermined signal from an antenna 14 to a reader (not shown). Radio frequency control in the radio transmission circuit 11 is performed based on a high-precision periodic signal from the crystal oscillator 12.

  The features of the present invention are an antenna 15 that receives a predetermined radio wave, a generator 16 that receives power from the radio wave received by the antenna 15 to generate power, a wireless transmission circuit 11 and a crystal according to the output voltage of the generator 16 A voltage detection circuit 17 that outputs a power on / off signal to the oscillator 12 is provided. The predetermined radio wave assumed here is different from the radio wave transmitted from the reader in the passive wireless tag system, for example, a radio wave periodically or constantly transmitted from a radio wave source such as a mobile phone, a mobile terminal, or a broadcasting station. Signal. Therefore, the reader need only be in a position where it can receive a transmission signal from the wireless tag.

  The operation procedure (driving method) of the active wireless tag of the present invention will be described with reference to the flowcharts of FIGS.

  When the antenna 15 receives a predetermined radio wave, it receives energy supply from the generator 16 and the received radio wave and starts a power generation operation (S1). At this time, the wireless transmission circuit 11 and the crystal oscillator 12 are off. The generator 16 gradually increases the output voltage by the energy of the received radio wave. The voltage detection circuit 17 detects the output voltage boosted by the power generator 16, and outputs a power-on signal to the wireless transmission circuit 11 and the crystal oscillator 12 when the output voltage of the power generator 16 exceeds a predetermined threshold ( S2, S3). The wireless transmission circuit 11 and the crystal oscillator 12 transmit a predetermined signal (for example, ID information of the wireless tag) from the antenna 14 by using the battery 13 as an operation power supply in response to the input of a power-on signal, and then a reset signal to the voltage detection circuit 17. Output (S4). The voltage detection circuit 17 resets the output voltage of the generator 16 to 0 in response to the input of the reset signal, and outputs a power-off signal to the wireless transmission circuit 11 and the crystal oscillator 12 (S5). The wireless transmission circuit 11 and the crystal oscillator 12 stop the operation by cutting off the power supply from the battery 13 by the input of the power-off signal. The above operation is repeated.

  Note that by adjusting the threshold value of the voltage detection circuit 17, the radio wave intensity for starting the operation of the radio tag (the radio transmission circuit 11 and the crystal oscillator 12), for example, the distance between the radio tag and the radio wave transmission source can be set. it can. Further, the timing at which the wireless tag operates can be set by adjusting the time during which the output voltage of the power generator 16 is equal to or higher than the predetermined threshold according to the threshold value of the voltage detection circuit 17.

  As described above, the active wireless tag according to the present invention is configured to intermittently operate with the reception of a predetermined radio wave as a trigger, and does not require transmission schedule management by the wireless tag itself. That is, the wireless transmission circuit 11 and the crystal oscillator 12 can be intermittently operated without using the transmission schedule management circuit 74 in the conventional active wireless tag. Thereby, an active wireless tag with extremely low power consumption can be realized.

  FIG. 3 shows a configuration example of the power generator 16. In the figure, a signal from an antenna 15 is input to a multistage booster circuit 22 using a plurality of transistors and capacitors via a matching circuit 21, and an output voltage corresponding to the number of stages is output. Although the booster circuit 22 having a five-stage configuration is shown here, the output voltage differs depending on the number of stages, and the time until the output voltage is obtained differs. The output of this generator is used only for detecting the voltage by the voltage detection circuit 17. For this reason, there is no load, and sufficient power generation is possible even with weak radio waves transmitted from, for example, a mobile phone within about 10 meters. Further, for example, power generation is possible for broadcast radio waves such as FM broadcast.

  FIG. 4 shows a configuration example of the voltage detection circuit 17. In the figure, the output voltage of the generator 16 is input from the voltage detection terminal to the Schmitt trigger circuit 31, and when the voltage at the voltage detection terminal reaches a predetermined threshold, a power-on signal is output via the output circuit 32. In addition, although the power supply voltage is applied to the Schmitt trigger circuit 31 from the battery 13 shown in FIG. 1, a current flows only at the moment when the voltage at the voltage detection terminal becomes a threshold value, and no current flows in other states. Therefore, the power consumption of the voltage detection circuit 17 is extremely small.

  Further, a voltage on signal is output from the voltage detection circuit 17, the wireless transmission circuit 11 and the crystal oscillator 12 operate, and after transmitting a predetermined signal, a reset signal is output from the wireless transmission circuit 11 to the voltage detection circuit 17. . This reset signal turns on the transistor 33 connected to the voltage detection terminal, and resets the output voltage of the generator 16 (voltage of the voltage detection terminal) to zero. As a result, the voltage detection circuit 17 outputs a power-off signal, and the wireless transmission circuit 11 and the crystal oscillator 12 stop operating. Therefore, the wireless transmission circuit 11, the crystal oscillator 12 and the voltage detection circuit 17 operate only at the moment when the output voltage of the generator 16 exceeds the threshold value, and the power consumption as a wireless tag becomes small, and the battery 13 The replacement frequency can be greatly reduced.

  In the configuration shown in FIG. 1, the crystal oscillator 12 is used in order to control the frequency of the transmission signal of the active wireless tag with high accuracy. However, in the case of an impulse radio system that communicates using the entire antenna band by supplying an impulse signal to the antenna 14, a crystal oscillator is unnecessary, and the present invention can also be applied to such an active radio tag. It is.

  In the configuration shown in FIG. 1, an example is shown in which the antenna 14 used for transmission from the active wireless tag is different from the antenna 15 that receives a predetermined radio wave. However, when radio waves in the same band are used for transmission and energy supply to the generator 16, one antenna may be shared.

  Here, the radio wave used for the power generation of the power generator 16 of the active wireless tag of the present invention and the usage form will be described. For example, in an event venue such as a museum, a mobile phone carried by a customer who enters is assumed as a radio wave source. Active radio tags placed at various locations in the event venue send a predetermined signal (for example, ID information set in the radio tag) in response to reception of radio waves from a mobile phone, and convert the signal into position information. Thus, the position of the mobile phone, that is, the position and density of the customer can be collected.

  Also, if the active wireless tag intermittently operates only when it receives a radio wave emitted from a mobile phone and transmits a predetermined signal (for example, temperature information measured separately), the time zone when the customer is entering The collection period of temperature information used for air conditioning management can be changed during an unattended closed time zone. The operation image in this case is shown as a time chart in FIG. This makes it possible to achieve both fine-tuned air conditioning management and reduced power consumption of the active wireless tag.

  Further, by adjusting the threshold value of the voltage detection circuit 17 and setting the time until the output voltage of the power generator 16 becomes equal to or higher than the threshold value, the active wireless tag is intermittently used, for example, using weak broadcasting radio waves such as FM broadcasting. It becomes possible to operate. The operation image in this case is shown as a time chart in FIG. In this example, since the active wireless tag can constantly receive radio waves, the time interval of intermittent operation is constant.

The figure which shows the structural example of the active wireless tag of this invention. The flowchart which shows the operation | movement procedure of the active wireless tag of this invention. The figure which shows the structural example of the generator 16. FIG. FIG. 3 is a diagram illustrating a configuration example of a voltage detection circuit 17. The time chart which shows the operation example of the active wireless tag of this invention. The figure which shows the structural example of the conventional hash wireless tag system. The figure which shows the structural example of the conventional active wireless tag.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Radio transmission circuit 12 Crystal oscillator 13 Battery 14 Antenna 15 Antenna 16 Generator 17 Voltage detection circuit 21 Matching circuit 22 Booster circuit 31 Schmitt trigger circuit 32 Output circuit 33 Transistor

Claims (7)

In an active wireless tag including a wireless transmission circuit that transmits a predetermined signal using a battery as an operating power source and a first antenna,
A second antenna for receiving a predetermined radio wave;
A generator for generating energy by receiving energy supply from radio waves received by the second antenna;
A voltage detection circuit that detects an output voltage of the generator and outputs a power on / off signal to the wireless transmission circuit according to the output voltage;
The voltage detection circuit outputs a power-on signal to the wireless transmission circuit when the output voltage of the generator exceeds a predetermined threshold, and the wireless transmission circuit uses the battery as an operating power supply by the input of the power-on signal. A predetermined signal is transmitted from the first antenna, and then a reset signal is output to the voltage detection circuit. The voltage detection circuit resets the output voltage of the generator to 0 by inputting the reset signal and turns off the power. An active wireless tag, wherein a signal is output to the wireless transmission circuit, and the wireless transmission circuit is configured to stop the operation by cutting off power supply from the battery in response to input of a power-off signal. The active wireless tag according to claim 1,
The voltage detection circuit includes a Schmitt trigger circuit that inputs an output voltage of the generator, and is configured to output the power-on signal using the battery as an operating power source when the output voltage exceeds a predetermined threshold value. Active wireless tag characterized by. The active wireless tag according to claim 1,
The battery as an operating power supply, comprising a crystal oscillator that outputs a predetermined periodic signal used for radio frequency control of the radio transmission circuit,
The active radio tag, wherein the crystal oscillator is configured to intermittently operate in accordance with a power on / off signal output from the voltage detection circuit. The active wireless tag according to claim 1,
An active wireless tag, wherein the second antenna receives a radio signal that is periodically or constantly transmitted from a radio wave source as the predetermined radio wave. The active wireless tag according to claim 1 or 4,
The active radio tag, wherein the first antenna and the second antenna are configured as one antenna that transmits and receives radio waves in the same band. In a method for driving an active wireless tag including a wireless transmission circuit that transmits a predetermined signal using a battery as an operating power source and a first antenna,
The generator generates power by receiving energy supply from the radio wave received by the second antenna that receives the predetermined radio wave,
When the output voltage of the generator is equal to or higher than a predetermined threshold, a power-on signal is output to the wireless transmission circuit,
The wireless transmission circuit transmits a predetermined signal from the first antenna using the battery as an operation power supply by inputting a power-on signal, and then outputs a reset signal,
The output signal of the generator is reset to 0 by the reset signal and a power off signal is output to the wireless transmission circuit,
The method of driving an active wireless tag, wherein the wireless transmission circuit stops operation by interrupting power supply from the battery in response to an input of a power-off signal. The driving method of the active wireless tag according to claim 6,
A method for driving an active wireless tag, wherein the second antenna receives a radio signal periodically or constantly transmitted from a radio wave source as the predetermined radio wave.

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