JP2010219915A - Radio tag reader/writer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure read performance without increasing power consumption or the like even when an environment around an RFID tag is changed. <P>SOLUTION: The radio tag reader/writer includes a ground plate connected to the ground, a microstrip patch antenna facing the ground plate, a fixing member for fixing the microstrip patch antenna and the ground plate with a space between the microstrip patch antenna and the ground plate, a conductive auxiliary member, and a driving means for driving the auxiliary member so as to enter the space. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless tag reading / writing device.

  In recent years, many RFID tags have been used for merchandise management and the like. It is known that this RFID tag changes its antenna impedance depending on the surrounding environment and changes reading performance. Until now, reading performance has been maintained by adjusting the dielectric constant around the tag and adjusting the output voltage of the reader / writer on the reading side. Moreover, in patent document 1, the board switching mechanism which switches the distance between the ground board which comprises a patch antenna, and a radiation board is provided, and the distance of a radiation board and a ground board is predetermined value according to the communication frequency with a wireless tag. There has been proposed an antenna device capable of reducing the return loss by changing to.

  However, the environment in which the RFID tag is used is not constant, and adjusting the dielectric constant around the tag in accordance with changes in the surrounding environment is not recommended for users who use the RFID tag and its reader / writer. In addition, when adjusting the output voltage of the reader / writer on the reading side, the power consumption of the reader / writer may increase. The technique of Patent Document 1 minimizes the return loss according to the communication frequency of the patch antenna with the wireless tag, and the reader / writer side reading performance at a specific communication frequency under the influence of the surrounding environment. It does not improve.

  The present invention has been made in view of the above, and can read and write a wireless tag that can ensure reading performance easily and without increasing power consumption even when the environment around the RFID tag changes. An object is to provide an apparatus.

  In order to solve the above-described problems and achieve the object, the RFID tag reader / writer according to the present invention includes a ground plane connected to a ground, a microstrip patch antenna facing the ground plane, and the microstrip patch antenna. A fixing member that fixes the microstrip patch antenna and the ground plane so as to provide a space between the ground planes, a conductive auxiliary member, and a drive unit that drives the auxiliary member to enter the space. It is characterized by that.

  The RFID tag reading / writing device according to the present invention can change its antenna impedance arbitrarily, so that the reading performance can be ensured easily and without increasing power consumption.

FIG. 1 is a block diagram showing a configuration of an RFID tag reading / writing device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the RFID tag 200. FIG. 3 is a diagram for explaining a main configuration of the antenna unit 111.

  Hereinafter, an embodiment of a wireless tag reading / writing device according to the present invention will be described in detail with reference to the accompanying drawings.

(RFID tag reading / writing device)
FIG. 1 is a block diagram showing a configuration of an RFID tag reading / writing device according to an embodiment of the present invention. As shown in FIG. 1, the RFID tag reading / writing apparatus 100 includes an RFID reader / writer unit 110, an antenna unit 111, an operation panel 112, a communication interface 113, a storage unit 114, a control unit 115, and the like.

  The antenna unit 111 transmits a modulated wave as a read / write signal under the control of the RFID reader / writer unit 110, and receives a modulated wave transmitted from the RFID tag 200 that has received the modulated wave. The read / write signal is a signal transmitted to the RFID tag when the RFID tag is read or written. With this signal, the RFID reader / writer unit 110 can contact the data stored in the memory unit 207 of the RFID tag 200 (described later) existing in a communication area where the modulated wave transmitted from the antenna 111 can reach without contact. Read or write data in the memory unit 207 without contact. The characteristic configuration of the antenna unit 111 will be described in detail later.

  The operation panel 112 is provided with various keys and a display unit. Various external devices can be connected to the communication interface 113. The administrator can operate the RFID tag reading / writing device 100 using the operation panel 112 or a host device (not shown) connected to the communication interface 113.

  The storage unit 114 stores various programs and RFID write data. Here, the RFID write data is information to be written in the memory unit 207 of the RFID tag 200. The storage unit 114 is, for example, an SRAM (Static Random Access Memory) that is a flash memory.

  The control unit 115 controls the RFID reader / writer unit 110, the operation panel 112, the communication interface 113, and the storage unit 114, respectively. When the control unit 115 receives an RFID issuing job from the host device via the communication interface 113, the control unit 115 stores the RFID write data included in the job in the storage unit 114.

(RFID tag)
Next, the configuration of the RFID tag 200 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the RFID tag 200.

  As shown in FIG. 2, the RFID tag 200 includes an antenna 201 and an IC chip 202. The IC chip 202 rectifies and stabilizes the modulated wave received by the antenna 201 to demodulate the modulated wave and send it to the control unit 205. The power generator 203 supplies power to each part of the IC chip 202. Unit 204, modulation unit 206 that modulates data sent from control unit 205 and sends it to antenna 201, data demodulated by demodulation unit 204 is written to memory unit 207, and data is read from memory unit 207 and modulated A control unit 205 that sends data to the unit 206, a nonvolatile rewritable memory unit 207 such as an EEPROM, and the like. In the memory unit 207, an ID, which is unique identification information assigned and set by the manufacturer at the manufacturing stage of the RFID tag 200, is stored in advance. In addition, a user area where a user can write arbitrary data is secured.

(Antenna part)
Next, details of the antenna unit 111 of the RFID reader / writer unit 110 will be described with reference to FIG. FIG. 3 is a diagram for explaining a main configuration of the antenna unit 111.

  As shown in FIG. 3A, the antenna unit 111 has a microstrip patch antenna 301 made of a microstrip line. Further, as shown in the figure, a metal ground plate connected to the ground is provided facing the microstrip patch antenna 301. As shown in FIG. 3 (B), the microstrip patch antenna 301 and the ground plane 302 are fixed to each other at a substantially central portion by a column 303 which is a fixing member made of plastic or metal. A space is provided between 301 and the base plate 302 as an air layer. In addition, a metallic auxiliary member 304 is provided in the antenna unit 111 so as to be able to enter the air layer between the microstrip patch antenna 301 and the ground plane 302 by being driven by a stepping motor 305 and a gear 306. Note that the stepping motor 305 accurately positions the auxiliary member 304 under the control of the control unit 115.

  The output impedance characteristic of the microstrip patch antenna 301 is optimized in a state where the auxiliary member 304 does not exist between the microstrip patch antenna 301 and the ground plane 302. When the auxiliary member 304 is gradually moved into the space between the microstrip patch antenna 301 and the ground plane 302 by driving by the stepping motor 305, the output impedance of the microstrip patch antenna 301 starts to change gradually. At this time, the movement of the auxiliary member 304 is stopped at the position of the auxiliary member 304 where the target RFID tag is successfully read. In this state, the wireless tag that has been difficult to read can be read. Note that when the number of target wireless tags is known, the number of wireless tags are read, and if all of them are read, the positioning operation of the auxiliary member 304 is stopped at that point. When the number of target wireless tags is not known, it is read as much as possible and the optimum position of the auxiliary member 304 is determined. Such positioning of the auxiliary member 304 may be automatically performed by the control unit 115, or the control unit 115 performs positioning of the position of the auxiliary member 304 in accordance with a user instruction via the operation panel 112. You may make it do.

  The RFID tag reading / writing apparatus 100 of the present embodiment changes the output impedance of the antenna unit 111 by changing the positional relationship between the microstrip patch antenna 301 and the auxiliary member 304. Then, when the impedance on the wireless tag side and the impedance on the antenna unit 111 side are close to each other, the coupling amount is maximized, so that more power is transmitted. As a result, the reading performance of the RFID tag reading / writing device 100 is improved.

DESCRIPTION OF SYMBOLS 100 RFID tag reading / writing apparatus 110 RFID reader / writer part 111 Antenna 112 Operation panel 113 Communication I / F
DESCRIPTION OF SYMBOLS 114 Memory | storage part 115 Control part 200 RFID tag 201 Antenna 202 IC chip 203 Power supply generation part 204 Demodulation part 205 Control part 206 Modulation part 207 Memory part 301 Microstrip patch antenna 302 Ground plane 303 Support | pillar 304 Auxiliary member 305 Stepping motor 306 Gear

JP 2006-261947 A

Claims (3)

A main plate connected to the ground,
A microstrip patch antenna facing the ground plane;
A fixing member for fixing the microstrip patch antenna and the ground plane so as to provide a space between the microstrip patch antenna and the ground plane;
A conductive auxiliary member;
A wireless tag reading / writing device comprising: driving means for driving the auxiliary member so as to enter the space.   2. The wireless tag reading / writing apparatus according to claim 1, wherein the driving unit includes a stepping motor and a gear.   The wireless tag reading / writing device according to claim 1, wherein the auxiliary member is positioned at a position where the wireless tag to be read can be read.

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