JP2010092208A - Rfid tag reader/writer system, rfid tag reader/writer device, and rfid tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RFID tag reader/writer system capable of communicating only with an RFID tag which is present within a prescribed range from the RFID tag reader/writer device. <P>SOLUTION: An RFID tag reader/writer device 10 transmits information related with an output power and a response correspondence distance (S12), and an RFID tag 80 determines whether or not an RFID tag is present within the range of the response distance (S26) based on the level of received power, and when determining that the RFID tag is present within the range of the response distance (S26: Yes), the RFID tag responds to the RFID tag reader/writer device (S28). Thus, it is possible to communicate with RFID tag which is present within the prescribed distance from the RFID tag reader/writer device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an RFID tag reader / writer system, an RFID tag reader / writer device, and an RFID tag that perform reading and writing by wireless communication with an RFID tag.

An RFID (Radio Frequency IDentification) system includes an RFID tag for registering ID and information data, and an RFID tag reader / writer device for recognizing and controlling the RFID tag. An RFID tag (passive tag) that does not have a built-in battery has a built-in antenna and an IC chip, receives power and communication data with the built-in antenna via radio waves output from the antenna of the RFID tag reader / writer device, and receives data from the IC chip. Register (encode), and return the data from the IC chip to the RFID tag reader / writer device.

In Patent Document 1, the distance to the external information storage medium is measured via the distance measuring unit, and the optimum value of the radio wave output is determined based on the measured distance, and the external information storage medium at an arbitrary distance is determined. An information terminal device that reads and writes information is disclosed.
JP-A-2005-328452 JP 2004-348559 A

However, in Patent Document 1, it is possible to read / write from / to an external information storage medium farther than an arbitrary position by reducing the transmission output of the external information storage medium. Reading and writing could not be restricted for external information storage media located closer.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an RFID tag reader / writer system, an RFID tag reader / writer device that can communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device, It is to provide an RFID tag.

In order to achieve the above object, the invention of claim 1 is an RFID tag reader / writer system that reads and writes information of the RFID tags 80A, 80B, and 80C with the RFID tag reader / writer device 10 through radio waves.
The RFID tag reader / writer device 10 transmits information on output power and response distance (S12),
The RFID tags 80A, 80B, 80C determine whether or not they are within the response distance range based on the level of received power (S26). If they are within the response distance range (S26: Yes), the RFID tag reader A technical feature is to respond to the writer device 10 (S28).

The RFID tag reader / writer system according to claim 1, the RFID tag reader / writer apparatus according to claim 9, and the RFID tag according to claim 10, wherein the RFID tag reader / writer apparatus transmits information regarding output power and response distance, and the RFID tag receives received power. It is determined whether or not the response distance is within the range of the response distance, and responds to the RFID tag reader / writer device when it is within the response distance. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

According to another aspect of the present invention, the RFID tag reader / writer device transmits the antenna gain together with information on the output power and the response distance. The RFID tag determines whether it is within the range of the response distance based on the antenna gain and the level of received power, and responds to the RFID tag reader / writer device when it is within the range of the response distance. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

According to a third aspect of the present invention, the RFID tag reader / writer device writes only to the RFID tag that is within the response distance and responds. For this reason, it is possible to write only to the RFID tag at a predetermined distance from the RFID tag reader / writer device.

According to claim 4, the RFID tag estimates the distance from the RFID tag reader / writer device based on the received output power and response distance information and antenna gain, the reception sensitivity of the RFID tag and the received signal level, and the estimated distance. In response to the RFID tag reader / writer device. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

In the fifth aspect, the RFID tag reader / writer device inputs the distance of the RFID tag that has been read and written at the time of initial setting, and calculates information related to the response distance based on the input distance. Thereby, the RFID tag reader / writer device transmits information on the output power and the response distance, and the RFID tag determines whether or not it is within the range of the response distance based on the level of the received power. Sometimes it responds to the RFID tag reader / writer device. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

According to the sixth aspect of the present invention, when the RFID tag reader / writer device detects the front passage of the object to which the RFID tag is attached and detects the front passage of the subject, the RFID tag reader / writer device communicates with the RFID tag attached to the subject. Do. For this reason, it can communicate only with the RFID tag at a predetermined distance in front of the antenna.

According to another aspect of the present invention, the RFID tag reader / writer device measures the distance to the RFID tag by the distance measuring means, and calculates information related to the response distance based on the measured distance. Thereby, the RFID tag reader / writer device transmits information on the output power and the response distance, and the RFID tag determines whether or not it is within the range of the response distance based on the level of the received power. Sometimes it responds to the RFID tag reader / writer device. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

According to an eighth aspect of the present invention, the RFID tag reader / writer device includes an antenna having directivity and directivity control means for controlling the direction of the antenna. As a result, it is possible to read / write only the RFID tag existing in a region formed by the direction directed by the antenna directivity control means and an arbitrary distance.

[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an explanatory diagram for explaining the outline of the RFID tag reader / writer system according to the first embodiment.
Cargoes 52A, 52B, and 52C are conveyed onto three belt conveyors 50A, 50B, and 50C. RFID tags 80A, 80B, and 80C are attached to the cargos 52A, 52B, and 52C, respectively. The RFID tag reader / writer device 10 reads / writes the RFID tags 80A, 80B, and 80C of the cargos 52A, 52B, and 52C conveyed on the arbitrary belt conveyors 50A, 50B, and 50C by wireless communication from the antenna 30. be able to. That is, the RFID tag of the cargo 52C conveyed on the conveyor 50C only to the RFID tag 80A of the cargo 52A conveyed on the conveyor 50A, and only to the RFID tag 80B of the cargo 52B conveyed on the conveyor 50B. Reading / writing can be performed only to 80C.

FIG. 2 is a block diagram showing a configuration of the RFID tag reader / writer device in FIG.
The RFID tag reader / writer device 10 is connected to a host device (host, not shown) such as a personal computer via a serial interface, for example, and the RFID tag shown in FIG. 1 based on an instruction of an application program on the host device side. Communication is performed with 80A, 80B, and 80C by radio signals. That is, the RFID tag reader / writer device 10 performs polling to intermittently transmit a calling code for the RFID tags 80A, 80B, and 80C in order to detect that the RFID tags 80A, 80B, and 80C have approached its own communication area ( request). At this time, by specifying the response distance, the RFID tag attached to the cargo conveyed on the belt conveyor 50A, the RFID tag attached to the cargo conveyed on the belt conveyor 50B, and conveyed on the belt conveyor 50C Request a response to one of the RFID tags attached to the cargo to be shipped. The belt conveyor (RFID tag attached to the cargo conveyed on the belt conveyor 50A, RFID tag attached to the cargo conveyed on the belt conveyor 50B, and belt of the response distance designated from the RFID tag reader / writer device 10 When the RFID tag attached to the cargo conveyed on the conveyor 50C is located in the communication area, the RFID tag reader / writer device 10 transmits the RFID tag 80A, the RFID tag 80B, or the RFID tag 80C having the response distance. A power supply and a clock for operation are generated from the signal to respond.

In FIG. 2 in which the electrical configuration is shown as functional blocks, a CPU (control circuit) 14 performs serial communication with a host device via a host interface (I / F) unit 12. The encoding unit 18 encodes transmission data given serially from the CPU 14 by, for example, the NRZ (Non Return to Zero) method and outputs the encoded data to the modulation unit 20. The carrier oscillating unit 16 supplies an oscillation signal of 13.56 MHz to the encoding unit 18 and the modulation unit 20 as a carrier wave signal and to the CPU 14 as a clock signal. The CPU 14 uses a frequency obtained by appropriately dividing the oscillation signal as an operation clock. The modulation unit 20 is configured to ASK modulate the carrier wave with encoded transmission data, and is configured to be able to adjust the degree of modulation in that case. The modulated signal modulated by the modulation unit 20 is output from the amplification unit 22 to the transmission / reception antenna 30 via the cable 34 and transmitted as a radio wave signal. As the antenna 30, a multi-element antenna having forward directivity is used as indicated by a chain line circle in the drawing.

On the other hand, when the antenna 30 receives a signal transmitted from the RFID tags 80A, 80B, and 80C, the received signal is output to the receiving circuit unit 24. The reception data demodulated and decoded by the reception circuit unit 24 is output to the CPU 14.

FIG. 3 is a functional block diagram showing an electrical configuration inside the RFID tag 80A. The RFID tags 80A, 80B, and 80C have the same configuration. The RFID tag 80A includes an antenna (LC resonance circuit coil) 90, a rectifier 92, a clock extractor 98, a CPU 94, a memory 96, a modulator 99, and the like.

When the antenna 90 receives the radio wave signal transmitted from the RFID tag reader / writer device 10, the rectifying unit 92 rectifies and smoothes the received signal and supplies operation power to the CPU 94 and the demodulated data obtained by demodulating the received signal. Is output to the CPU 94. The clock extraction unit 98 supplies the CPU 94 with a clock signal extracted from the signal received by the antenna 90. The CPU 94 reads / writes data from / to the nonvolatile memory 96.

Further, the CPU 94 serially outputs transmission data to the modulation unit 99. The modulation unit 99 is connected to the antenna 90. In the memory 96 of the RFID tag 80A, ID data of the RFID tag 80A, a code used for authentication processing at the time of communication, data related to the user of the RFID tag 80A originally intended to be read by the RFID tag reader / writer device 10, and the above-mentioned A program for determining whether or not the response distance specified by the RFID tag reader / writer device is within the range is stored.

Next, processing for communicating with only the RFID tag on the designated distance (designated belt conveyor) will be described with reference to FIGS.
FIG. 4 is a flowchart showing the initial setting of the RFID tag reader / writer device according to the first embodiment. Here, the line A of the belt conveyor 50A shown in FIG. 1 is 1 m from the antenna 30 of the RFID tag reader / writer device, the line A ′ is 1.5 m, the line B of the belt conveyor 50B is 3 m, the line B ′ is 3.5 m, It is assumed that the line C of the belt conveyor 50C is 5 m and the line C ′ is 5.5 m. Here, the farthest belt conveyor 50C is stopped at a position where the cargo 52C is in front of the antenna 30, and the RFID tag reader / writer device 10 is adjusted to adjust the radio wave intensity at a distance (5 m) from the cargo 52C. In this figure, the cargo 52C is shown in a position where the side surface can be seen. However, the initial setting RFID tag 80 is arranged in the direction in which the radio wave intensity from the RFID tag reader / writer device is maximized. The cargo 52C is placed on the belt conveyor 50C. Specifically, the cargo is placed in a direction in which the antenna 30 is on an extension line with the side surface to which the RFID tag is attached. The same applies to the cargo 52B on the belt conveyor 50B and the cargo 52A on the belt conveyor 50A. Here, the initial setting RFID tag 80 does not correspond to the distance designation, and uses an object that responds to reading and writing from the RFID tag reader / writer device regardless of the distance.

When a distance (5 m) to the farthest RFID tag 80, an intermediate distance (distance of the conveyor 50B: 3 m), and a closest distance (distance of the conveyor 50A: 1 m) are input via the host device (S52: Yes) ), The farthest distance of 5 m is registered for initial setting (S54), and communication with the RFID tag 80 is started (S56). First, communication is attempted with a predetermined output, and when communication with the RFID tag 80 is possible (S58: Yes), the output power is reduced (S59). On the other hand, when communication is not possible (S58: No), the output power is increased (S60). Then, until necessary data, that is, an output value capable of reliably performing communication with the RFID tag 80 having a distance of 5 m is obtained (S62: No), the process returns to S58 and communication is repeated. When the lowest level output value capable of reliably communicating with the RFID tag 80 having a distance of 5 m is obtained (S62: Yes), distance data is created (S64). Here, the distance to the farthest RFID tag 80 (5 m ± 1 (more than 4 m, less than 6 m)), the distance to the intermediate distance RFID tag 80 (3 m ± 1 (more than 2 m, less than 4 m)), the nearest RFID tag 80 A response distance consisting of a distance up to (1 m ± 1 (over 0 m, less than 2 m)) is created.

Next, the reading process of the RFID tag reader / writer device 10 will be described with reference to the flowchart of FIG. FIG. 5A is a flowchart showing a reading process on the RFID tag reader / writer device side, and FIG. 5B is a flowchart showing a process on the RFID tag side. Here, the description is continued assuming that reading / writing is performed by designating the RFID tag 80C attached to the cargo 52C conveyed on the farthest belt conveyor 50C described above with reference to FIG.

The RFID tag reader / writer device 10 transmits radio waves to read / write the RFID tag 80C passing through a distance of 5 m attached to the cargo 52C conveyed on the belt conveyor 50C (S12 in FIG. 5A). ). At this time, the distance over 4 m, the response distance of less than 6 m, the output value set in the initial setting (the output value set in the above process at the position of 5 m), and the distance of 5 m set with the output value, The gain of the antenna 30 is transmitted.

When the RFID tags 80A, 80B, and 80C receive radio waves (S22 in FIG. 5B: Yes), the gain of the antenna 30 on the RFID tag reader / writer device 10 side, the gain of the built-in antenna 90 (see FIG. 3), The free space loss from the transmitted output value is calculated from the received power value (S24), and it is determined whether or not it matches the designated response distance (S26). Here, the RFID tags 80A and 80B receive high-output radio waves with little free space loss due to the correspondence between the distance of 5 m for which the output value is set and the response distance of more than 4 m and less than 6 m. If the specified response distance is not met (S26: No), the process is terminated. The RFID tag 80C transmits the response because the distance of 5 m for which the output value is set corresponds to the response distance of more than 4 m and less than 6 m and matches the specified response distance (S26: Yes) ( S28). Here, when communication with the RFID tag 80B is performed, the RFID tag 80B has a set output value, a distance of 5 m where the output value is set, and a response distance of more than 2 m and less than 4 m. Corresponding, that is, when there is a reception strength that is higher by a value corresponding to the free space loss of the difference 2m between the intermediate distances 3m and 5m of more than 2m and less than 4m, the self is in the response distance of more than 2m and less than 4m to decide. More specifically, the minimum reception level value at which the RFID tag can stably communicate is held in advance in the RFID tag, and the minimum reception at a distance of 5 m is performed in the initial setting process described above with reference to FIG. The output on the RFID tag reader / writer device 10 side is set so as to be level. Whether the RFID tag 80B has a reception level between a reception level when a radio wave having a minimum reception level at a distance of 5 m is received at a distance of 4 m and a reception level when the radio wave is received at a distance of 2 m. Thus, it is determined whether or not the user is at a response distance of more than 2 m and less than 4 m. Similarly, when performing communication with the RFID tag 80A, the RFID tag 80A corresponds to the set output value, the distance of 5 m where the output value is set, and the response distance of more than 0 m and less than 2 m. That is, when there is a reception strength that is high by a value corresponding to a free space loss of 4 m and 5 m between a difference of more than 0 m and less than 2 m and 5 m, it is determined that the self is in a response distance of more than 0 m and less than 2 m.

Next, the writing process of the RFID tag reader / writer device 10 will be described with reference to FIG. The RFID tag reader / writer device 10 transmits a radio wave for instructing writing to the RFID tag 80C (S32 in FIG. 6A). At this time, the distance over 4 m, the distance less than 6 m, the output value set in the initial setting, the distance (5 m) in which the output value is set, and the gain of the antenna 30 are transmitted.

When the RFID tags 80A, 80B, 80C receive radio waves (S42 in FIG. 6B: Yes), they calculate the free space loss from the output value transmitted from the values of the antenna gain and received power, respectively (S44). ), It is determined whether or not it matches the designated response distance (S46). Here, since the RFID tags 80A and 80B do not coincide with the designated response distance (S46: No), the processing ends. Since the RFID tag 80C matches the specified response distance (S46: Yes), information is written (S48). Here, the RFID tag 80C is identified from the RFID tag reader / writer device 10 with a response distance of more than 4 m and less than 6 m, but based on the ID sent from the RFID tag 80C without specifying the response distance, It is also possible to obtain a response to the RFID tag 80C.

The RFID tag reader / writer apparatus 10 detects a cargo 52A conveyed on the belt conveyor 50A, a cargo 52B conveyed on the belt conveyor 50B, and a cargo 52C conveyed on the belt conveyor 50C. Then, radio wave transmission is repeated while switching between designations of distances greater than 2 m and less than 4 m and designations of distances greater than 4 m and less than 6 m. Thereby, the RFID tag reader / writer device 10 grasps the cargo conveyed by each belt conveyor by detecting the RFID tag attached to the cargo conveyed on each belt conveyor 50A, belt conveyor 50B, and belt conveyor 50C. it can.

In the RFID tag reader / writer system, the RFID tag reader / writer device 10, and the RFID tag 80 according to the first embodiment, the RFID tag reader / writer device 10 transmits information about output power and response distance (S12), and the RFID tag 80 receives received power. Based on this level, it is determined whether or not it is within the range of the response distance (S26), and when it is within the range of the response distance (S26: Yes), it responds to the RFID tag reader / writer device (S28). For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

In the first embodiment, the RFID tag reader / writer device 10 transmits an antenna gain together with information on output power and response distance. The RFID tag determines whether it is within the range of the response distance based on the gain of the antenna 30 and the level of received power, and responds to the RFID tag reader / writer device when it is within the range of the response distance. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

In the first embodiment, the RFID tag reader / writer device 10 writes only to the responding RFID tag within the response distance range (S48). For this reason, it is possible to write only to the RFID tag at a predetermined distance from the RFID tag reader / writer device.

In the first embodiment, the RFID tag 80 estimates the distance to the RFID tag reader / writer device 10 based on the received output power and response distance information, the antenna gain, and the received signal level of the RFID tag (S24). If the determined distance is within the predetermined range (S26: Yes), a response is made to the RFID tag reader / writer device (S28). For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

In the first embodiment, the RFID tag reader / writer device 10 inputs the distance of the RFID tag that was read and written at the time of initial setting (S52), and calculates information related to the response distance based on the input distance (S64). ). Thereby, the RFID tag reader / writer device transmits information on the output power and the response distance, and the RFID tag determines whether or not it is within the range of the response distance based on the level of the received power. Sometimes it responds to the RFID tag reader / writer device. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

[Second Embodiment]
Next, an RFID tag reader / writer system, an RFID tag reader / writer apparatus, and an RFID tag according to a second embodiment of the present invention will be described. The configurations of the RFID tag reader / writer device and the RFID tag of the second embodiment are the same as those of the first embodiment described above with reference to FIGS.

FIG. 7 is an explanatory diagram showing a schematic configuration of an RFID tag reader / writer system according to the second embodiment. In the second embodiment, the light emitting device 36A and the light receiving device 36B are arranged across the belt conveyors 50A, 50B, 50C, and it is detected that the cargo has passed in front of the antenna 30, and at the detected timing, the RFID tag reader / writer device 10 attempts to communicate with the RFID tag 80C on the belt conveyor 50C, the RFID tag 80B on the belt conveyor 50B, and the RFID tag 80A on the belt conveyor 50A.

FIG. 8 is a flowchart showing a reading process in the RFID tag reader / writer apparatus according to the second embodiment. Based on the output from the light receiver 36B described above, it is determined whether the cargo has blocked the light between the light emitter 36A and the light receiver 36B, that is, whether the cargo has passed in front of the antenna 30 (S11). Here, if there is a passage of cargo (S11: Yes), each RFID tag 80C, RFID tag 80B, and RFID tag 80A try to communicate with each other (S12). Subsequent processing is the same as that of the first embodiment described above with reference to FIGS.

In the second embodiment, when the RFID tag reader / writer device 10 detects the passage of a cargo with an RFID tag in front of the antenna, the RFID tag reader / writer device 10 communicates with the RFID tag attached to the cargo. For this reason, it can communicate only with the RFID tag at a predetermined distance in front of the antenna.

[Third embodiment]
An RFID tag reader / writer system, an RFID tag reader / writer device, and an RFID tag according to a third embodiment will be described. The configurations of the RFID tag reader / writer device and the RFID tag of the third embodiment are the same as those of the first embodiment described above with reference to FIGS.

FIG. 9 is an explanatory diagram showing a schematic configuration of an RFID tag reader / writer system according to the third embodiment. In the third embodiment, a distance measuring device 38 for measuring the distance from the antenna 30 to the RFID tag is provided. The distance measuring device 38 includes a semiconductor laser that outputs infrared light, a PSD (Position Sensitive Detector) that receives reflected light reflected by the RFID tag as reflected by the RFID tag, and an incident angle received by the PSD. And an arithmetic unit for calculating the distance to the RFID tag. Each of the RFID tags 80A, 80B, 80C is attached to the surface of the cargo 52A, 52B, 52C facing the distance measuring device 38, and to a height at which the infrared rays emitted from the semiconductor laser of the distance measuring device 38 hit.

Initial setting in the RFID tag reader / writer system of the third embodiment will be described with reference to the flowchart of FIG. 10 showing the processing.
In the first embodiment, the operator manually inputs the distance to the RFID tag. On the other hand, in the third embodiment, the initial setting RFID tag 80 is attached to the cargo 52A, 52B, 52C to be conveyed on the belt conveyors 50A, 50B, 50C, so that the belt conveyor 50A, the belt conveyor 50B, the belt The distance to the conveyor 50C is automatically measured by the distance measuring device 38. As in the first embodiment, the initial setting RFID tag 80 does not correspond to distance designation, and uses an object that responds to reading and writing from the RFID tag reader / writer device regardless of the distance. Here, the cargo 52A is transported onto the nearest belt conveyor 50A, then the cargo 52B is transported onto the intermediate belt conveyor 50B, and finally the cargo 52C is transported onto the farthest belt conveyor 50C. . The RFID tag reader / writer device 10 is set in advance to have three types of distances, and it is ruled to perform measurement from a short distance.

When the RFID tag reader / writer device 10 first detects the RFID tag 80 of the cargo 52A on the belt conveyor 50A via the distance measuring device 38 (S151: Yes), it measures the distance to the RFID tag 80 (S152). Then, it is determined whether the measurement of the three types of distances has been completed. Here, since the measurement of the distance to the RFID tag 80 on the nearest belt conveyor has been completed (S154: No), the process returns to S151 and is intermediate. In preparation for the measurement of the RFID tag 80 of the cargo 52B on the belt conveyor 50B at a distance of. When the distance measurement of the RFID tag 80 of the cargo 52C on the farthest belt conveyor 50C is completed (S154: Yes), the output adjustment is performed in the subsequent processing as in the first embodiment described above with reference to FIG. Plan.

FIG. 11 is a flowchart showing a reading process in the RFID tag reader / writer apparatus according to the third embodiment. It is determined whether the RFID tag has passed in front of the antenna 30 by the distance measuring device 38 described above (S11). Here, when the RFID tag passes (S11: Yes), the distance to the RFID tag is measured (S92), and reading / writing is performed on the RFID tag of the distance. Here, for example, when the RFID tag 80B attached to the cargo 52B on the belt conveyor 50B at an intermediate distance is detected, an intermediate distance (distance greater than 2 m and less than 4 m) is designated and a radio wave is transmitted ( S12). Subsequent processing is the same as that in the first embodiment, and thus description thereof is omitted. In the third embodiment, when the RFID tag 80B is detected on the belt conveyor 50B at an intermediate distance, communication is performed only with the RFID tag 80B, and the closest belt conveyor 50A and the farthest belt conveyor 50C are detected. Communication with the RFID tag is not performed. In the third embodiment, the RFID tag 80C is not shaded by the cargo 52A and 52B when viewed from the distance measuring device 38 side, and the cargo is placed on the belt conveyor so that the RFID tag 80B is not shaded by the cargo 52A. It is necessary to let

In the third embodiment, the RFID tag reader / writer device 10 measures the distance to the RFID tag by the distance measuring device 38 and calculates information related to the response distance based on the measured distance. As a result, the RFID tag reader / writer device 10 transmits information on the output power and the response distance, and the RFID tag determines whether it is within the range of the response distance based on the level of the received power. In response to the RFID tag reader / writer device. For this reason, it is possible to communicate only with an RFID tag at a predetermined distance from the RFID tag reader / writer device.

[Fourth embodiment]
The RFID tag reader / writer system according to the fourth embodiment will be described with reference to FIG. In the first to third embodiments described above, communication is performed with the RFID tag in front of the antenna, and only the distance is designated. In contrast, in the fourth embodiment, a distance and a direction are specified. The RFID tag reader / writer device 10 includes a directional multi-element antenna 130 and includes an antenna directivity control device 132 that adjusts the direction of the directional multi-element antenna 130.

In the RFID tag reader / writer system according to the fourth embodiment, reading / writing is performed only with respect to an RFID tag that exists in an area having a direction directed by the directional multi-element antenna 130 adjusted by the antenna directivity control device 132 and an arbitrary distance. Can do.

In the first embodiment to the fourth embodiment, three distances (close distance, intermediate distance, and far distance) are set. However, the distance can be set to 4 or more in the case of two distances.

It is explanatory drawing which shows schematic structure of the RFID tag reader / writer system which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the RFID tag reader / writer apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the RFID tag which concerns on 1st Embodiment. It is a flowchart which shows the initial setting of the RFID tag reader / writer apparatus which concerns on 1st Embodiment. FIG. 5A is a flowchart showing a reading process in the RFID tag reader / writer apparatus according to the first embodiment, and FIG. 5B is a flowchart showing a process on the RFID tag side. FIG. 6A is a flowchart showing a writing process in the RFID tag reader / writer apparatus according to the first embodiment, and FIG. 6B is a flowchart showing a process on the RFID tag side. It is explanatory drawing which shows schematic structure of the RFID tag reader / writer system which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the reading process in the RFID tag reader / writer apparatus which concerns on 2nd Embodiment. It is explanatory drawing which shows schematic structure of the RFID tag reader / writer system which concerns on 3rd Embodiment of this invention. It is a flowchart which shows the initial setting of the RFID tag reader / writer apparatus which concerns on 3rd Embodiment. It is a flowchart which shows the reading process in the RFID tag reader / writer apparatus which concerns on 3rd Embodiment. It is explanatory drawing which shows schematic structure of the RFID tag reader / writer system which concerns on 4th Embodiment of this invention.

Explanation of symbols

10 RFID tag reader / writer device 30 Antenna 32 Distance measuring device (ranging means)
36A light emitter (detection means)
36B light receiver (detection means)
50A, 50B, 50C Belt conveyor 52A, 52B, 52C Cargo (object)
80A, 80B, 80C RFID tag 90 Antenna 132 Antenna directivity control device (antenna directivity control means)
S52 (distance input means)

Claims (10)

In an RFID tag reader / writer system that reads and writes information of an RFID tag with an RFID tag reader / writer device via radio waves,
The RFID tag reader / writer device transmits information regarding output power and response distance, and the RFID tag determines whether or not the response distance is within the range of the response distance based on the level of received power. An RFID tag reader / writer system characterized by responding to the RFID tag reader / writer device sometimes. The RFID tag reader / writer system according to claim 1, wherein the RFID tag reader / writer device transmits an antenna gain together with information on the output power and a response distance. 3. The RFID tag reader / writer system according to claim 1, wherein the RFID tag reader / writer device writes only to the RFID tag that is within the response distance and responds. The RFID tag estimates the distance to the RFID tag reader / writer device based on the received information regarding the output power and response distance, the antenna gain, and the received signal level of the RFID tag, and the estimated distance is within a predetermined range. 3. The RFID tag reader / writer system according to claim 2, wherein the RFID tag reader / writer device responds to the RFID tag reader / writer device. The RFID tag reader / writer device includes a distance input means for an operator to input the distance of the RFID tag that has been read and written at the initial setting,
2. The RFID tag reader / writer system according to claim 1, wherein information on the response distance is calculated based on the inputted distance. The RFID tag reader / writer device includes detection means for detecting the front of the antenna attached to the RFID tag object,
2. The RFID tag reader / writer system according to claim 1, wherein when the detection unit detects the forward passage of the object, communication is performed with respect to the RFID tag attached to the object. The RFID tag reader / writer device includes distance measuring means for measuring a distance to the RFID tag,
2. The RFID tag reader / writer system according to claim 1, wherein information on the response distance is calculated based on the input distance. The RFID tag reader / writer device includes an antenna having directivity and directivity control means for controlling the direction in which the antenna is directed, and exists in an area formed by a direction directed by the antenna directivity control means and an arbitrary distance. 2. The RFID tag reader / writer system according to claim 1, wherein the RFID tag reader / writer system performs reading and writing with respect to the RFID tag. In an RFID tag reader / writer device that reads and writes information of an RFID tag via radio waves,
Send information about output power and response distance to the RFID tag,
Receiving a response from the RFID tag determined to be within the range of the response distance based on the level of received power;
An RFID tag reader / writer device that performs writing only to an RFID tag that is within the response distance and responds. In an RFID tag that reads and writes information with an RFID tag reader / writer device via radio waves,
Receiving information on output power and response distance transmitted from the RFID tag reader / writer device;
An RFID tag characterized by determining whether or not the response distance is within a range based on a level of received power and responding to the RFID tag reader / writer device when the response distance is within the response distance.

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