JP2005198032A - Non-electric source rf tag and interrogator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-electric source RF tag capable of obtaining information even at the far distance. <P>SOLUTION: In (a), an interrogator 200 comprises a transmission and receiving part 210 and a light emission part 220 for emitting invisible light of acute directivity. A tag 300 is irradiated with an invisible laser or a light with acute directivity which an LED has. The tag 300 receives the lights at a light receiving part 320 to convert them into electric energy and operates the transmission and receiving part 310 with that energy as an energy source. Then, a radio wave transmitted by the interrogator 200 is modulated by information which the transmission and receiving part 310 of the tag 300 has is transmitted to the interrogator side as the radio wave. In the construction of (b), the tag 300 which has received the visible light from the interrogator 200 converts the light received by the light receiving part 320 into the electric energy. Using the power, a microwave is generated by a transmission part 330 on the tag 300 side, modulated by data, and transmitted to the interrogator 200. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-powered RF tag and an interrogator.

Conventionally, tags using RF (radio frequency) have been used for identifying objects. For example, when an RF tag is attached to a medicine and information about what kind of medicine is to be obtained, a radio frequency radio wave at which the tag resonates is emitted from the interrogator toward the tag. The tag rectifies the radio wave, operates the electronic circuit in the tag, modulates the radio wave sent, and sends it back to the reader as radio wave. In FIG. 1, the conceptual diagram which showed the relationship between the conventional RF tag 120 and the interrogator 110 is shown. As shown in FIG. 1, the tag side has no power supply.
A radio wave is emitted from the reader (interrogator) 110 as energy. In the non-power supply RF tag 120, in order to operate the RF tag 120, the radio wave from the interrogator 110 is rectified to be a power source (power regeneration), the radio wave sent from the interrogator 110 is modulated and sent back, and the tag information is returned. Tell the reader (interrogator) 110. The reader (interrogator) 110 receives and demodulates the radio wave modulated by the RF tag, and detects information.
For the conventional RF tag and interrogator described above, refer to Non-Patent Document 1, for example.

In the conventional system shown in FIG. 1, an important performance is the distance between the tag 120 and the interrogator 110. The longer it is, the better. The communication distance depends on the magnitude of the radio wave output of the interrogator 110 and the gain of the antennas 112 and 122 of the interrogator 110 and the RF tag 120, but is usually several mm to several cm. It is said that the interrogator antenna can be made about 10 cm square at 2.4 GHz (the highest carrier frequency used for RF tags), and the communication distance can be about 1 m. Increasing the radio wave output to increase the distance causes problems in interference with other tags and interference with other communications, and therefore cannot be increased under license. Therefore, the antenna 112 having a large gain is prepared in the interrogator 110. However, the antenna 112 having a large gain is an antenna having a large shape, which is an obstacle to miniaturization of the interrogator 110. Further, since the antenna 122 on the tag side cannot be made larger than the interrogator, the tag side cannot gain gain.
As described above, in the conventional RF tag, the longer the distance between the RF tag 120 and the reader (interrogator) 110, the larger the antenna 112 of the reader (interrogator) 110, and the reader (interrogator) 110 becomes larger. It was an obstacle to downsizing.
Japan Automatic Recognition System Association edited "RFID understood by this" (Ohm Co., Ltd. September 10, 2003)

  An object of the present invention is to enable a distance from an interrogator to be increased in a non-power supply RF tag.

In order to achieve the above-described object, the present invention provides a light emitting unit that generates visible light with strong directivity with respect to a non-powered RF tag, and reception that receives information from a radio wave from the non-powered RF tag. A light receiving unit that receives visible light from the interrogator and converts it into electrical energy, and is supplied with electric energy from the light receiving unit, and receives information from the radio wave to the interrogator. It is a non-power supply RF tag characterized by including the transmitter which transmits.
Furthermore, the interrogator may be provided with a transmitter that transmits radio waves to the non-power supply RF tag. Electric energy is supplied to the non-power supply RF tag from the light receiving unit, and radio waves from the interrogator are transmitted. A receiver for receiving may be provided, and the transmitter may modulate and transmit the received radio wave.
The interrogator may include a positive periodic wave generator, the light emitting unit may be driven by the positive periodic wave generator, and a light receiving unit of the non-power-supply RF tag includes a filter and a rectifier circuit. Thus, it is preferable to convert visible light that fluctuates in a specific cycle into electrical energy.

Since the power is supplied to the non-powered tag by visible light, the distance between the tag and the interrogator can be increased as compared with the case of supplying by radio waves.
In addition, since only the target tag can be activated using the directivity by visible light, erroneous data is not obtained even when there are a plurality of tags.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 2A and FIG. 2B are diagrams showing the configuration of the embodiment of the present invention.
In FIG. 2A, the interrogator 200 includes a transmission / reception unit 210 having the same configuration as the conventional one and a light emitting unit 220 that generates visible light with sharp directivity. In this configuration, conventionally, electromagnetic waves emitted from the interrogator 200 to the tag 300 for supplying energy are radiated to the tag side as light having a sharp directivity of a visible laser or LED. In the tag 300, the light is received by the light receiving unit 320 and converted into electric energy, and the transmission / reception unit 310 of the tag 300 is operated as an energy source. Then, the radio wave transmitted from the interrogator 200 is modulated by the information held in the transmission / reception unit 310 of the tag 300 and is transmitted as a radio wave to the interrogator.

  The configuration shown in FIG. 2B is a slight modification of the configuration shown in FIG. In FIG. 2B, the tag 300 that has received visible light from the interrogator 200 converts the light received by the light receiving unit 320 into electrical energy. Using the power, a microwave is generated by the transmission unit 330 on the tag 300 side, modulated with data, and sent to the interrogator 200. Although the burden on the tag 300 side is increased as compared with the configuration shown in FIG. 2A, the burden on the interrogator 200 side is reduced.

  The communication distance between the interrogator 200 and the tag 300 is determined by how much energy as a power source can be given to the tag 300. It is determined by the power regeneration capability rather than the information transmission part that uses the radio wave from the interrogator 200 to modulate and send it back by a method such as reflection or non-reflection. The sharp directivity of light can send the transmitted energy to the tag without any loss even if the distance is long, and can supply energy to the power source.

  Now, when energy is supplied to the tag 300 by a laser or LED that is a light emitting unit of the interrogator 200, it is necessary to accurately illuminate the tag 300 with the light from the interrogator 200. If visible light is used, the user can confirm which tag 300 is selected visually. If it is off, energy will not be transmitted and the tag will not work. If there are multiple tags around the interrogator, only the irradiated tag will respond. A sharp ray can select one tag enough. This indicates that a plurality of nearby tags respond like radio waves and are less likely to cause interference. Further, data other than the tag aimed at the interrogator in response to a plurality of tags will not be erroneously recognized as that of the target tag. Furthermore, even if a plurality of data including a target tag appears, it is not necessary for the interrogator to select necessary data from the data.

FIG. 3 shows a case where a powerless tag 300 for performing power transmission with light is attached to the back cover of a book. Since power is transmitted to the non-powered tag 300 by light having high directivity, even if the tags are dense, it can be selected from them. Only the tags selected by illuminating react, and the other tags do not react. Information on the book can be selectively obtained by illuminating the non-powered tag 300 attached to the spine of the book.
In the case of a conventional tag that performs power supply by radio waves, surrounding tags also react. Moreover, since the directivity characteristics of the antenna cannot be sufficiently obtained with radio waves, power transmission over a long distance is not possible. Or the antenna of the interrogator can only be enlarged. If it is light, the directivity is strong and the tag can be selected.

The reason why the visible light is sent from the interrogator to the tag regardless of the radio wave is that a small LD (semiconductor laser) or LED (Light Emission Diode) can obtain an overwhelming directivity than the radio wave. The directivity of the laser light source is particularly strong. This indicates that much of the transmitted energy can be transmitted to the tag without loss. Loss is small even at long distances. Since it is difficult to obtain such directivity with radio waves, a lot of energy is lost when the distance is long. When trying to have directivity, the radio wave becomes a large antenna and hinders downsizing, but LD and LED can be downsized despite their sharp directivity. In the configuration shown in FIG. 2, the reason for sending back by radio waves instead of light from the tag side is that only information needs to be sent by sending back, and there is no need to transmit energy. This is because transmission of information is much easier than transmission of energy. That is, a large antenna gain and a large size antenna are not required for the interrogator.
In the configuration in which microwaves are generated on the tag side shown in FIG. 2B, the burden on the tag side is increased, but radio waves are only transmitted for information, and energy transmission is not required. From the point of view, it is the same.

FIG. 4 is a diagram for specifically explaining the interrogator 200 and the tag 300 shown in FIG.
In FIG. 4, the interrogator 200 includes a light emitting unit 224, an antenna 231, a microwave transceiver 232, and a data display unit 234 using a visible laser or LED. The DC power supply 222 supplies power to each part. The interrogator 200 has the same configuration as that of a conventional interrogator except that the interrogator 200 includes a light emitting unit 224.
The light receiving unit 322 of the solar cell in the tag 300 receives the light from the light emitting unit 224, converts the received light into electrical energy, and supplies power in the tag. The antenna 311, the modulation unit 313, and the data unit 314 have the same configuration as that of a conventional non-power supply RF tag.
In this configuration, when light for power transmission from the light emitting unit 224 of the interrogator 200 strikes the light receiving unit 322 of the tag 300, power supply to the transmitting / receiving unit 310 (FIG. 2A) starts. Then, the radio wave from the microwave transceiver 232 of the interrogator 200 is received by the antenna 311 of the tag 300, and the radio wave is modulated by the data from the data unit 314 by the modulation unit 313, whereby the data in the tag 300 is converted. It transmits from the antenna 311 to the interrogator 200. The interrogator 200 receives the radio wave from the tag 300 with the antenna 231, demodulates it with the microwave transceiver 232, and displays it on the data display unit 234.
The transmission / reception between the interrogator 200 and the tag 300 is performed only between the tag irradiated with the power transmission light from the light emitting unit 224 of the interrogator 200.

FIG. 5 is a diagram illustrating another configuration example of the interrogator 200 and the tag 300 illustrated in FIG. The configuration shown in FIG. 5 is a configuration example of power transmission that is not affected by background light. The same components as those in FIG. 4 are denoted by the same reference numerals.
In FIG. 5, the light emitting unit (visible laser or LED) 224 of the interrogator 200 is driven by the output of the positive periodic wave generating unit 223 (varied with a constant frequency or a pseudo-random pattern). The light fluctuates at a constant frequency or pseudo-random pattern. The light receiving unit (solar cell) 322 of the tag 300 that has received the power transmission light passes through the matched random filter or bandpass filter 324 that passes the pseudo random pattern and frequency of the positive periodic wave generating unit 223. The rectifier circuit 326 supplies power in the tag as a direct current. For this reason, the tag 300 does not operate unless laser light or LED light, which is a periodic wave, from the interrogator 200 is received. For this reason, the operation of the tag 300 is not affected by the sun or illumination. Note that the number of cycles (frequency) taking a positive value is not 50 Hz or 60 Hz used in the AC power supply, but a frequency that is not easily affected by illumination.
The bandpass filter is used for selecting a simple periodic wave such as a sine wave. The matched filter can be used to select a more general periodic wave such as a pseudo random pattern. A bandpass filter is a special type of matched filter.

FIG. 6 is a diagram illustrating a configuration example of the interrogator 200 and the tag 300 illustrated in FIG. The configuration shown in FIG. 6 is the same as the configuration example of power transmission that is not affected by the background light shown in FIG. The same components as those in FIG. 5 are denoted by the same reference numerals.
In this configuration, when light for power transmission from the light emitting unit 224 of the interrogator 200 strikes the light receiving unit 322 of the tag 300, power supply to the transmitting unit 330 (FIG. 2B) starts. Then, the signal transmitted from the oscillation circuit 331 of the tag 300 is modulated with the data signal from the data unit 314 in the modulation circuit 332, so that the information in the tag 300 is transmitted from the antenna 311 to the interrogator 200.
The interrogator 200 receives the radio wave from the tag 300 with the antenna 231, demodulates it with the microwave transceiver 232, and displays it on the data display unit 234.
Even in the configuration shown in FIG. 6, since the light emitting unit (visible laser or LED) 224 of the interrogator 200 is driven by the output of the positive periodic wave generating unit 223, the light reception of the tag 300 that receives the power transmission light. The unit (solar cell) 322 passes the band number filter or matched filter 324 that passes the number of cycles (frequency) of the positive periodic wave generation unit 223 or the pseudo random pattern, or the matched filter 324 to generate a direct current in the rectifier circuit 326. Power is supplied in the tag. Therefore, as in the configuration of FIG. 5, the tag 300 does not operate unless laser light or LED light having the number of cycles (frequency) in the interrogator 200 is received. For this reason, the operation of the tag 300 is not affected by the sun or illumination.
Note that the interrogator and tag of FIG. 2B can be configured with the same configuration as FIG. 4 without using the positive periodic wave generator 223, the matched filter, or the bandpass filter 324.

It is a figure which shows the structure of the conventional RF tag. It is a figure which shows the structure of embodiment of this invention. It is a figure which shows the application example which attached the tag to the spine of a book. It is a figure which shows the specific example of an interrogator and a tag. It is a figure which shows the other specific example of an interrogator and a tag. It is a figure which shows the other specific example of an interrogator and a tag.

Claims (6)

A light-emitting unit that generates visible light with strong directivity with respect to a non-power-supply RF tag;
A receiver for receiving information by radio waves from the non-power-supply RF tag. The interrogator of claim 1,
The interrogator further comprises a transmitter that transmits radio waves to the non-power RF tag. The interrogator according to claim 1 or 2,
An interrogator further comprising a positive periodic wave generator, wherein the light emitting unit is driven by the positive periodic wave generator. A light receiving unit that receives visible light from the interrogator and converts it into electrical energy;
A non-power-supply RF tag comprising: a transmitter which is supplied with electric energy from the light receiving unit and transmits information by radio waves to the interrogator. The no-power RF tag according to claim 4,
In addition, a receiver that is supplied with electric energy from the light receiving unit and receives radio waves from the interrogator,
The transmitter is a non-power RF tag, wherein the transmitter modulates and transmits a received radio wave. The no-power RF tag according to claim 4 or 5,
The light receiving unit includes a filter and a rectifier circuit,
A non-power-supply RF tag that converts electrical energy only from visible light that fluctuates in a specific cycle.

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