JP2006180073A - Wireless ic tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless IC tag that a reader can communicate with even at a longer distance and which is low-cost and convenient and has an added collision preventing function. <P>SOLUTION: Disclosed is the wireless IC tag constituted by adding: a rectifying circuit 12 which receives and converts a radio wave for retrieval from the reader into a DC voltage V<SB>d</SB>; and the collision preventing function for a return radio wave by generating a boosted voltage V<SB>D</SB>by boosting the DC voltage V<SB>d</SB>by a boosting circuit 21, supplying the DC voltage V<SB>D</SB>to a modulating circuit 15 to expand a range of communication with the reader by increasing the intensity of the return radio wave, by controlling the timing of transmission and reception between the reader and wireless IC tag by a transmission control information ROM. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless IC tag (also referred to as an electronic price tag) that receives search radio waves with an antenna, generates power, and transmits tag information and the like recorded in an identification IC chip.

Currently, barcodes are widely used as a method for automatically identifying and classifying articles. The bar code records binary code information by a combination of bars of different thicknesses arranged in parallel and their intervals, and the information is read by laser scanning. Recently, wireless IC tags for managing article information have attracted attention. The features of wireless IC tags compared to barcodes are:
(1) The amount of information dramatically increases from about 13 digits of barcode to about 38 digits (in the case of 128-bit data in binary code).
(2) Resistant to contamination and excellent in environmental resistance.
(3) It has a transmission function capable of reading tag information of packed goods.
(4) Since a plurality of pieces of tag information can be read at the same time, high-speed processing such as instant payment of merchandise at a cash register is possible.
Etc. have excellent properties.

Wireless IC tags are roughly classified into the following four types.
(A) Read-only tag: Tag information is stored in a read-only memory (ROM) written at the manufacturing stage of the identification IC chip, and the user cannot change the tag information. When the wireless IC tag enters the communicable range with the reader, it continuously starts transmitting its own tag information to the reader. Communication with the reader is one-way, and transmission from the reader to the wireless IC tag is not possible. For this reason, when there are a plurality of wireless IC tags in a communication range with the reader, interference (collision) occurs when the reader tries to read the plurality of tag information at the same time, and the tag information cannot be individually read. However, since this wireless IC tag has a simple circuit configuration, the size of the identification IC chip can be reduced, power consumption and cost can be reduced, and a conventional barcode can be substituted.
(B) Writable tag: The identification IC chip incorporates an electrically writable / erasable memory such as EEPROM or SRAM, and tag information can be modified in accordance with a command from the reader. Since it has a transmission function from the reader to the wireless IC tag, it can have an anti-collision function (collision prevention function), and even if there are multiple wireless IC tags at the same time within the communicable range with the reader, Tag information can be read individually. This anti-collision function is an essential function for batch processing of a large number of articles.
(C) Tag with encryption function: For applications that require security of tag information, an identification IC chip incorporates an encryption processing circuit to perform authentication between a wireless IC tag and a reader.
(D) Microprocessor tag: The wireless IC tag has a microprocessor incorporated in an identification IC chip and has more complicated encryption processing functions and authentication functions. It is used for contactless smart cards that require advanced authentication functions such as electronic money and transportation tickets and confidentiality of transmission.

  Of the four types of wireless IC tags described above, read-only tags that can be manufactured at the lowest cost and are expected to have an enormous market scale as an alternative to conventional barcodes have recently attracted attention. FIG. 10 shows a circuit configuration of a wireless IC tag in the conventional read-only tag disclosed in Patent Document 1, Patent Document 2, and Non-Patent Document 1.

  This wireless IC tag receives weak search radio waves from a reader by an antenna 101 and generates a DC voltage Vd using a rectifier circuit 102. The rectifier circuit 102 includes a voltage limiter that limits the upper limit of the DC voltage Vd supplied to the internal circuit of the identification IC chip as necessary. This DC voltage Vd is supplied to a circuit 103 including a clock generation circuit that generates various electric signals from a search radio wave received by an antenna, and a reset circuit that controls the timing for starting stable operation of the identification IC chip. Yes. The DC voltage Vd is also supplied to a tag information ROM circuit in which tag information is written and a ROM circuit 104 having peripheral circuits such as a counter and a decoder for reading the tag information. Further, it is also supplied to a modulation circuit 105 that transmits the read tag information as a return radio wave from the antenna. That is, the conventional wireless IC tag supplies a single DC voltage Vd to all circuits in the identification IC chip.

FIG. 11 shows a circuit configuration example in which a conventional IC chip for identification of a wireless IC tag is simplified. The input voltage of the search radio wave received by the antenna 11 is V _IN, and the DC voltage V _d is generated by the rectifier circuit 12 to which V _IN is input. Rectifier circuit includes a voltage limiter for limiting the upper limit of the DC voltage V _d generated. The DC voltage V _d is supplied to an analog / digital circuit 13 and the modulation circuit 15, the voltage amplitude of the reply wave including a tag information generated through the modulation circuit 15 to V _OUT. Here, for simplification of description, the clock generation circuit, the reset circuit, and the tag information ROM circuit illustrated in FIG.

12A and 12B show a circuit described in Non-Patent Document 2 that is used as a power supply rectifier circuit built in an identification IC chip of a wireless IC tag. FIG. 12A shows a bridge-type rectifier circuit composed of four diodes D1 to D4. If the amplitude of the input AC voltage is V _IN , the DC voltage V _d obtained across the capacitor C ₁ is about ( V _IN / 2−V _T ). Here, V _T is a threshold voltage of the forward rise of the diode.

FIG. 12B shows a charge pump type voltage doubler rectifier circuit. The input voltage V _IN is applied to the diodes D ₅ and D ₆ via the capacitor C ₂ , and the DC voltage V _{d is} applied across the capacitor C _3. (V _IN -2V _T ) is obtained.

In any circuit system, it is desirable that the threshold voltage V _{T of the} diode be as low as possible. Assuming the V _T = 0V as an ideal diode, a bridge rectifier circuit described above is approximately V _IN / 2, the voltage doubler rectifier circuit of the DC voltage V _d of approximately V _IN is obtained. Therefore, in the following, it is assumed that the DC voltage V _d is proportional to the input voltage V _IN of the search radio wave.

FIG. 13 shows a circuit diagram of a rectifier circuit and a modulation circuit part built in an identification IC chip in an example in which an antenna transmits tag information of a wireless IC tag disclosed in Non-Patent Document 3. The input voltage induced in the antenna L is rectified by a bridge rectifier circuit composed of _four diodes D _{1 to} D ₄ shown in FIG. 12A to generate a DC voltage V _d in the capacitor C ₁ . Yield diode Z ₁ is too strong search radio wave when the reader and the wireless IC tag approaches is the voltage limiter to prevent the rise in the DC voltage V _d is more stable operating voltage identification IC chip . V _d is supplied to the frequency dividing circuit, and the high frequency signal f _{IN of the} antenna input to the frequency dividing circuit is divided to generate the clock frequency f _{S of the} subcarrier. The 2-input NAND circuit N ₁ inputs the f _S signal and tag information sent from the tag information ROM circuit, and outputs an electric signal of a subcarrier modulated by the tag information.

If you enter the clock signal to the gate of MOSFET M _1, the antenna load resistance R ₁ by a subcarrier is controlled to be on / off for the GND potential, outgoing modulated wave reply by the tag information from antenna Is done. Since the circuit shown in FIG. 13 is supplied with a single DC voltage V _d , only the maximum voltage corresponding to the DC voltage V _d is applied to the gate voltage V _G of the MOSFET M ₁ .

If the drain current controlled to be turned on / off by the MOSFET M ₁ is I _D , the voltage amplitude V _OUT of the return radio wave transmitted from the antenna is proportional to L _C (dI _D / dt). Here, L _C is the inductance of the antenna L, and (dI _D / dt) indicates the time variation of the return current. The drain current I _D flowing through the MOSFET is proportional to K (V _G −V _TR ) ² . Here, K is a constant determined by the physical constant of the MOSFET and the device shape, V _G is a gate voltage, and V _G is assumed to be equal to the DC voltage V _d applied to the modulation circuit. V _TR is the threshold voltage of the MOSFET. Therefore, if the time during which I _D changes is constant, V _OUT is proportional to I _D , that is, (V _G −V _TR ) ² . For simplicity, it can be assumed that V _OUT is proportional to V _d ² assuming that V _G = V _d is sufficiently larger than V _TR .

  On the other hand, when there are multiple wireless IC tags that are read-only tags within the communicable range with the reader, tag information is transmitted almost simultaneously from each wireless IC tag, so that the reply radio waves collide with each other. Therefore, the reader may experience a collision phenomenon of return radio waves that cannot normally read individual tag information.

  As a conventional example in which a collision prevention function for preventing the collision phenomenon is incorporated in a wireless IC tag, Patent Document 3 and Patent Document 4 are exemplified. In Patent Document 3, a waiting time until tag information transmission starts is controlled by a random number generated by a calculation of a processor built in a wireless IC tag. Further, this wireless IC tag has a communication function with a reader, and a wireless IC tag that has finished reading tag information is put into a sleep state to enable a more complete collision prevention function.

  In the example of Patent Document 4, the standby time is controlled by the first random number written in the ROM circuit built in the wireless IC tag. When wireless IC tags having the same first random number exist within the communicable range of the reader, the standby time is controlled by switching to the second random number possessed by each wireless IC tag. Since it is very unlikely that each wireless IC tag has the same first random number and second random number, collision prevention can be achieved.

  However, in Patent Document 3 and Patent Document 4 described above, since a mutual communication function between the reader and the wireless IC tag is required, a low-cost read-only tag with a collision prevention function cannot be realized. Furthermore, in the case of Patent Document 3, since the random number is generated by the processor, the circuit of the identification IC chip becomes extremely complicated, and the cost cannot be reduced. In the case of Patent Document 4, since there are two types of random numbers built into the ROM, it is difficult to make the probability that the two types of ROM data are exactly the same zero.

Japanese Patent Laid-Open No. 10-322250 JP 2002-152080 A Japanese Unexamined Patent Publication No. 08-123918 JP 2004-206371 A M. Usami et al., "The μ-Chip: An ultra-small 2.45 GHz RFID chip for ubiquitous recognition applications," IEICE Transactions on Electronics, vol. E86-C, no. 4, p. 521- p.528, April 2003 . K. Finkenzeller, Translated by Software Engineering Laboratory, "RFID Handbook, Principles and Applications of Contactless IC Cards" (2nd edition), p. 42 and p. 115, 2004 K. Finkenzeller, Translated by Software Engineering Laboratory, "RFID Handbook, Principles and Applications of Contactless IC Cards" (2nd Edition) p. 42, 2004

  Therefore, the following two items can be cited as problems of the conventional read-only tag.

  First, the minimum direct current required for the operation of the identification IC chip in the rectification circuit that rectifies the weak search radio wave received by the antenna of the wireless IC tag and generates the direct current voltage for operating the identification IC chip. In order to obtain a voltage, the radio wave intensity for search exceeding a certain level is required. In addition, in order for the reader to be able to receive a return wave of tag information from the wireless IC tag, a return wave intensity of a certain level or more is required. For this reason, the communication distance between the wireless IC tag and the reader is limited to keep a certain distance or less. However, the communicable range between the wireless IC tag and the reader is preferably as long as possible. Therefore, the wireless IC tag operates normally even with lower-intensity search radio waves, and by enabling tag information to be transmitted from the radio IC tag to the reader with higher-intensity return radio waves, It is required to increase the communication distance.

  Second, a read-only tag that does not have a collision prevention function cannot simultaneously read tag information from a plurality of tags that exist within a communication range with a reader, and therefore simultaneously receives information from a large number of wireless IC tags. Batch processing is not possible. Therefore, a lot of tag information cannot be processed at the same time, and the application range is extremely limited without taking advantage of the features of the wireless IC tag. To expand the range of applications by taking advantage of low-cost read-only tags, even if there are many wireless IC tags in a certain area, the tag information from each wireless IC tag can be read normally. It is essential to incorporate the anti-collision function to be controlled at a low cost.

  In order to increase the communicable range between the wireless IC tag and the reader in the first problem described above, a larger DC voltage is generated from a weak low-intensity search radio wave received by the antenna, and stronger from the antenna. It is necessary to transmit a return radio wave carrying tag information with strength.

  In order to solve the second problem, it is necessary to add a more complete anti-collision function at a low cost without having a communication function with the reader. For this purpose, a tag is simultaneously received from a plurality of wireless IC tags in a communicable range with the reader after a reset time elapses until the identification IC chip of the wireless IC tag operates stably after receiving a search radio wave from the reader. A simple function to control the unique timing at which each wireless IC tag itself transmits tag information in order to prevent information from being transmitted and a return radio wave from colliding and consequently being unable to be read by a reader Need to be built in.

  As a more preferable method, the tag information read by the reader is returned to the tag, the wireless IC tags whose tag information has already been read are sequentially put into a sleep state, and the tag information is not yet read from the wireless IC tag. A tag information transmission / reception function that reduces the probability of a return radio wave colliding is built into an identification IC chip of a wireless IC tag at a low cost.

  An object of the present invention is to provide a wireless IC tag, particularly a wireless IC tag for a read-only tag that is low in cost and high in performance, and an improved wireless IC tag thereof. The first purpose is to realize a higher-performance wireless IC tag by widening the communicable range between the wireless IC tag and the reader as compared with the conventional example. The second purpose is a low-cost wireless IC tag that has a built-in simple collision prevention function and can reliably read the tag information even if multiple wireless IC tags are simultaneously present in the communicable range of the reader. Is to provide.

  In the present invention, in order to achieve the first object, a DC voltage booster circuit is built in the wireless IC tag. In order to achieve the second object, a transmission control information ROM circuit for adjusting the timing of transmitting tag information from the wireless IC tag is added.

  Specifically, in order to achieve the first object, the antenna is composed of an antenna and an identification IC chip. The identification IC chip includes a rectifier circuit that converts a search radio wave received by the antenna into a DC voltage, and a reply radio wave. A clock generation circuit for generating and sending out a basic signal, a tag information ROM circuit in which tag information is written, a control circuit for sending out the tag information as an information signal, and a return radio wave modulated by the information signal as an antenna In a wireless IC tag composed of a modulation circuit to be transmitted from, a booster circuit is provided for the rectifier circuit, and the boosted voltage obtained by boosting the DC voltage by the booster circuit is supplied to the clock generation circuit, the control circuit or the modulation circuit. Developed a wireless IC tag to supply.

  Here, the rectifier circuit is provided with a multi-stage booster circuit, and supplies two or more different boosted voltages obtained by boosting the DC voltage by the booster circuit to the clock generation circuit, the control circuit, or the modulation circuit, respectively. You may make it the structure to carry out.

  In order to achieve the second purpose, the antenna is composed of an antenna and an identification IC chip. The identification IC chip includes a rectifier circuit that converts a search radio wave received by the antenna into a DC voltage, and a basic signal of a reply radio wave. A clock generation circuit that generates and sends out, a tag information ROM circuit in which tag information is written, a control circuit that sends out the tag information as an information signal, and a return radio wave modulated by the information signal from the antenna A wireless IC tag composed of a modulation circuit is provided with a transmission control information ROM circuit in which transmission control information for setting how to send information signals representing tag information to the control circuit is written, and modulation is performed from the tag information ROM circuit. The method of sending the information signal of the tag information to the circuit is a wireless IC tag that is randomly changed by a control circuit that operates according to the sending control information of the sending control information ROM circuit. It was developed.

  Here, the transmission control information ROM circuit suspends the waiting time until the tag information information signal starts to be sent after the operation of the control circuit starts, the number of repetitions of sending the tag information information signal, and the sending of the tag information information signal. The transmission control information may be written with any one or a combination of interruption times. The identification IC chip also includes a demodulation circuit that demodulates a search radio wave received by an antenna to obtain an information signal of tag information, and a part of the tag information and tag information written in the tag information ROM circuit. Alternatively, the control circuit is configured to stop the transmission of the tag information written in the tag information ROM circuit when the collation of tag information is obtained by the collation circuit. Good.

  Since each of the identification IC chips is formed as a part of a large-scale integrated circuit chip, a wireless IC tag can be configured including the large-scale integrated circuit chip.

  According to the present invention, a DC voltage booster circuit is built in the identification IC chip of the wireless IC tag, and the communication range between the wireless IC tag and the reader can be greatly expanded. Furthermore, the IC chip for identification of the wireless IC tag has a built-in low-cost and simple collision prevention function that enables simultaneous reading of tag information from a plurality of wireless IC tags within the communicable range of the reader. The effect that the application range of the read-only tag can be expanded can be obtained.

FIG. 1 is a circuit configuration diagram showing the basic operation principle of a wireless IC tag in which a booster circuit according to the present invention is built in an identification IC chip. A feature of the present invention resides in that a first booster circuit 21 for multiplying a DC voltage by m is added to an identification IC chip. A voltage limiter function may be added to the first booster circuit 21. In this example, if the antenna receives the search radio wave V _IN / n whose intensity is reduced to 1 / n of the search radio wave V _IN transmitted from the reader, the DC voltage generated by the rectifier circuit 12 is also V _d. Reduced to / n. Here, if the first booster circuit 21 can boost m times, the first booster circuit 21 outputs a DC voltage (m / n) V _d , and the analog / digital circuit 13 and the modulation circuit 15. To supply. As described above, since the strength of the return radio wave transmitted from the antenna through the modulation circuit 15 is proportional to the square of the DC voltage supplied to the modulation circuit, the wireless IC tag of this example has (m / n) ² A reply wave amplified to V _OUT is transmitted.

In general, since radio waves propagate in a three-dimensional space, if the distance from the antenna to the reader is x, the intensity of the search radio waves attenuates in proportion to x ⁻³ . Now, if the m value is set so that n of the attenuation ratio of the intensity of the search radio wave and (m / n) ² of the gain of the return radio wave from the wireless IC tag are equal, m = n ^3/2 The following relationship is obtained. In other words, if this condition is satisfied, the reader can receive the return radio wave with the same strength from the wireless IC tag as before, even if the search radio wave received by the radio IC tag becomes 1 / n. The communication distance is increased by n ^1/3 times.

  When the above condition is satisfied, the expansion ratio of the communicable range between the wireless IC tag and the reader is, for example, 1.26 if n = 2 and 1.44 if n = 3. Accordingly, if the multiplication factor m of the first booster circuit 21 is 2.8, the communicable range is improved by about 25%, and if the multiplication factor m is 5.2, the communicable range is improved by about 45%.

FIG. 2 shows an example of a circuit that can be used as a DC voltage booster circuit. This circuit is a 5-stage Dickson charge pump DC-DC converter. The input DC voltage V _d is applied to the capacitors C _{4 to} C ₈ . The DC voltage V _d is multiplied by using pulse voltages φ ₁ and φ ₂ having opposite phases and diodes D _{7 to} D _11, and about 5 (V _d −V _T as a boost voltage V _{D at} both ends of the capacitor C _8. ). Assuming that V _T = 0V, V _D = 5V _d and a DC voltage multiplied by 5 is obtained. If the number of stages connected in series is appropriately selected, a higher boosted voltage V _D can be obtained.

In the example shown in FIG. 1, the boosted voltage V _D boosted by one stage by the first booster circuit 21 is supplied to the analog / digital circuit 13 and the modulation circuit 15. In the example shown in FIG. 3, the boosted voltage V _D boosted by the first booster circuit 21 is applied only to the modulation circuit 15 or a part thereof, and the other analog / digital circuit 13 is generated by the rectifier circuit 12. DC voltage _Vd is applied. In this circuit configuration, since the power to be supplied from the first booster circuit 21 can be reduced, the circuit design of the first booster circuit 21 is easy and the device dimensions and the like are designed to be small, and the wireless IC tag can be further reduced. . Also, the power consumption of the identification IC chip is reduced. In this case, it requires consideration of the design at a low DC voltage V _d so as to enable the analog / digital circuit 13 and the like.

The example shown in FIG. 3 illustrates a state where the boost voltage V _D is applied to the modulation circuit 15. However, if the signal voltage applied to the gate of the MOSFET M ₁ shown in FIG. 13 is equal to the boosted voltage V _D , the drain current can be greatly changed. Therefore, only the two-input NAND circuit N ₁ has the boosted voltage V _D. Can also be applied.

FIG. 4 shows another example of the present invention. Obtaining a boosted voltage V _D to input DC voltage V _d from the rectifier circuit 12 to the first booster 21. Further, the boosted voltage V _D is input to the second booster circuit 22 to obtain a further boosted two-stage boosted voltage V _DD . The obtained boosted voltage V _D is supplied to the analog / digital circuit 13 and the DC voltage V _DD is supplied to the modulation circuit 15. In addition, the two-stage boosted voltage V _DD can be supplied to the analog / digital circuit 13 and the modulation circuit 15. Furthermore, as described in the explanation of FIG. 3, the two-stage boosted voltage V _DD may be supplied to all of the modulation circuit 15 or only to a part thereof.

  FIG. 5 shows an example of the present invention for adding a simple collision prevention function to a wireless IC tag. A feature of the present invention is that the analog / digital circuit 13 is added with a transmission control information ROM circuit 30 for adjusting the timing of transmitting tag information written in the tag information ROM circuit of the identification IC chip. .

FIG. 6 shows a flowchart of timing control of the transmission control information ROM circuit 30. Wireless IC tag of the present invention, generates a DC voltage V _d and the step-up voltage V _D required for stable operation of the rectifier circuit 12 and the first booster 21 has identification IC chip receives the search radio wave from the reader After the reset is released, a waiting time (w × t _D ) until transmission of a return radio wave carrying the tag information is started, and then a transmission time (s × t _D ) for transmitting the tag information , And the interruption time (i × t _D ) during which transmission is interrupted after the transmission time has elapsed. Here, the number of repetitions of the transmission time is set.

Here, t _D is a unit time required to transmit the tag information. The t _D integers w, expressed as a multiple of, s and i are written in advance identification IC chip as the delivery control information, such numerical write made to be random for each wireless IC tag It is rare and cannot be written from the outside.

  Therefore, the probability that a plurality of wireless IC tags within the communicable range of the reader have the same combination of values of w, s, and i is extremely low. Therefore, if the radio wave for reply from the wireless IC tag within the communicable range is repeatedly transmitted at the timing shown in FIG. 6, the transmission timing of the radio wave for reply will be different from the other radio IC tags. Even if the return radio waves collide temporarily, they are always read by the reader. Even if a wireless IC tag with the same values of w, s, and i exists in the communicable range of the reader, radio wave transmission from the reader is repeated intermittently and depends on manufacturing variations of the wireless IC tag. If the time difference until the reset is released is used, it is possible to avoid collision of reply radio waves.

  FIG. 7 adds a demodulation circuit and a verification circuit 40 to the identification IC chip of the wireless IC tag shown in FIG. 5 and changes it to a transmission / reception transmission control information ROM circuit 31 instead of the transmission control information ROM circuit 30. Another example of a wireless IC tag having a collision prevention function according to the present invention is shown. Here, the demodulation circuit is a circuit that receives tag information of a wireless IC tag that has been read and is demodulated into a digital signal. The collation circuit is a circuit that collates whether or not part or all of the tag information of the wireless IC tag that has been read as described above matches the tag information of the identification IC chip of the wireless IC tag. .

FIG. 8 is a flowchart of timing control for realizing the collision prevention function. Wireless IC tag of the present invention receives the search radio wave from the reader generates a DC voltage V _d and the step-up voltage V _D required rectifier circuit 12 and the first booster 21 is in the stable operation of the wireless IC tag After the reset is released, the standby time (w × t _D ) until the tag information transmission is started, and after the transmission time (s × t _D ) for transmitting the tag information has elapsed, the standby time Set (p × t _D ). When the tag information transmitted from the reader during the standby time is received and the tag information held by the wireless IC tag itself is collated. Assuming that the reader has already read the tag information of the wireless IC tag, the wireless IC tag is put into a sleep state, and transmission is suspended. If the matching circuit does not obtain a match signal, the tag information of the wireless IC tag has not been read by the reader, so it returns to the initial state and waits for transmission, tag information transmission and reception standby. Repeat until the verification circuit issues a sleep command.

Here, the t _D integers w, expressed as a multiple of, s and p, the transmission control information has been written in advance in the transmission and reception delivery control information ROM circuit 31 of the identification IC chip as such numerical each radio Each IC tag is designed to be random and cannot be written from the outside.

  In the case of this example, the number of wireless IC tags that enter the sleep state increases rapidly every round of the timing control flowchart shown in FIG. 8, and the number of wireless IC tags in the communicable range to be read by the reader decreases rapidly. Therefore, the probability that the return radio waves transmitted from the wireless IC tag will collide drastically decreases. Therefore, compared to the case of the wireless IC tag illustrated in FIG. 6, all the wireless IC tags within the communicable range of the reader are used. The tag information can be collected more reliably in a shorter time.

Here, the method of supplying the DC voltage V _d and the boosted voltage V _D in the wireless IC tag circuit illustrated in FIGS. 5 and 7 conforms to the method illustrated in FIG. 3, but as illustrated in FIGS. A simple power supply method may be used.

  FIG. 9 shows an example in which the identification IC circuit 50 constituting the wireless IC tag of the present invention is incorporated in a part of a large-scale integrated circuit 51 such as a microprocessor and can be connected to an external terminal via an antenna connection terminal 52. Indicates. If an antenna is connected to the antenna connection terminal 52 from the outside, the tag information written in the identification IC circuit incorporated in the large-scale integrated circuit 51 can be read without contact. It is possible to follow up the production history, distribution route, etc., and to prevent forgery. In the case of the large-scale integrated circuit 51, since the chip area is large, the antenna can be formed integrally on the chip. Alternatively, it is possible to apply a signal for reading tag information written in the wireless IC tag from the outside to a plurality of terminals corresponding to antenna connection terminals and read the unique information.

According to the present invention, a wireless IC tag having an expanded communication range with a reader can be realized at low cost. In other words, the wireless IC tag has a built-in booster circuit for multiplying the DC voltage by m times, and the voltage amplitude of the return radio wave is n times the voltage amplitude of the search radio wave attenuated to 1 / n of the conventional example. It was realized. For example, the m value necessary for realizing n = 2 to 3 is 3 to 5. If the communication distance in this case is assumed to increase in proportion to n ^1/3 , an expansion of the communication range of 25 to 45% is realized.

  In addition, by adding a simple and low-cost collision prevention function, especially to a read-only tag wireless IC tag, it is possible to read tag information from a plurality of wireless IC tags within the communicable range of the reader, Realize expansion of application range of wireless IC tag of read-only tag. This anti-collision function uses the timing deviations written in advance in the transmission control information ROM circuit 30 so that the three types of timing for controlling transmission and reception between the wireless IC tag and the reader are random for each wireless IC tag. This was realized by reading the tag information from each wireless IC tag.

1 is a basic circuit configuration diagram of a wireless IC tag according to the present invention. FIG. It is an example of a DC voltage booster circuit. It is a circuit block diagram of the Example of the radio | wireless IC tag by this invention. It is a circuit block diagram of another Example of the radio | wireless IC tag by this invention. It is a circuit block diagram of the Example of the radio | wireless IC tag with a collision prevention function by this invention. It is a flowchart figure for implement | achieving the collision prevention function by this invention. It is a circuit block diagram of another Example of the radio | wireless IC tag with a collision prevention function by this invention. It is a flowchart figure of another Example for implement | achieving the collision prevention function by this invention. 1 is a large-scale integrated circuit incorporating a wireless IC tag according to the present invention. It is a circuit block diagram of the conventional radio | wireless IC tag of a read-only tag. It is the circuit block diagram which simplified the radio | wireless IC tag of the conventional read-only tag. Examples of conventional rectifier circuits are (a) a bridge type rectifier circuit and (b) a voltage doubler rectifier circuit. It is a circuit diagram of the conventional rectifier circuit and a modulation circuit part.

Explanation of symbols

11, 101 Antenna
12, 102 Rectifier circuit
13 Analog / digital circuits
15, 105 Modulation circuit
21 First booster circuit
22 Second booster circuit
30 Transmission control information ROM circuit
31 Transmission / reception transmission control information ROM circuit
40 Demodulation circuit and verification circuit
50 IC circuit for identification
51 Large scale integrated circuits
52 Antenna connection terminal
103 Circuit including clock generation circuit and reset circuit
104 ROM circuit
105 Modulation circuit

Claims (6)

The identification IC chip includes an antenna and an identification IC chip. The identification IC chip converts a search radio wave received by the antenna into a DC voltage, a clock generation circuit that generates and sends a basic signal of a reply radio wave, and tag information In a wireless IC tag consisting of a tag information ROM circuit in which is written, a control circuit that sends out the tag information as an information signal, and a modulation circuit that emits a return radio wave modulated by the information signal from an antenna,
A wireless IC tag comprising a booster circuit for a rectifier circuit and supplying a boosted voltage obtained by boosting a DC voltage by the booster circuit to a clock generation circuit, a control circuit, or a modulation circuit. The rectifier circuit includes a multi-stage booster circuit, and supplies two or more different boosted voltages obtained by boosting a DC voltage by the booster circuit to each of the clock generation circuit, the control circuit, and the modulation circuit. The wireless IC tag described. The identification IC chip includes an antenna and an identification IC chip. The identification IC chip converts a search radio wave received by the antenna into a DC voltage, a clock generation circuit that generates and sends a basic signal of a reply radio wave, and tag information In a wireless IC tag consisting of a tag information ROM circuit in which is written, a control circuit that sends out the tag information as an information signal, and a modulation circuit that emits a return radio wave modulated by the information signal from an antenna,
A transmission control information ROM circuit in which transmission control information for setting a method of sending information signals representing tag information to the control circuit is written is provided, and tag information information signals are sent from the tag information ROM circuit to the modulation circuit. The wireless IC tag is randomly changed by a control circuit that operates according to the transmission control information of the transmission control information ROM circuit. The transmission control information ROM circuit is any of the waiting time until the tag information information signal starts to be sent after the operation of the control circuit starts, the number of repetitions of sending the tag information information signal, and the interruption time for interrupting the tag information information signal sending. The wireless IC tag according to claim 3, wherein transmission control information combined with or in combination is written. The identification IC chip includes a demodulation circuit that demodulates a search radio wave received by an antenna to acquire an information signal of tag information, and a part or all of the tag information and tag information written in the tag information ROM circuit. 4. The wireless communication device according to claim 3, further comprising: a collation circuit for collation, wherein the control circuit stops sending the tag information written in the tag information ROM circuit when collation of the tag information is obtained by the collation circuit. IC tag. The wireless IC tag according to claim 1, wherein the identification IC chip is integrally formed as a part of a large-scale integrated circuit chip.

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