JP4320580B2 - RFID reader / writer and antenna structure - Google Patents

Description

  The present invention relates to a reader or reader / writer of an RFID (Radio Frequency Identification) system that performs non-contact data communication using electromagnetic induction or electromagnetic coupling, and more particularly to an antenna structure of the reader or reader / writer.

  In recent years, RFID systems that perform data communication between a tag including an IC chip and a reader or reader / writer (hereinafter collectively referred to as a reader / writer) have become widespread. Since this RFID system communicates data using the antenna provided in each of the tag and the reader / writer, and can communicate even when the tag is separated from the reader / writer, it is used for various applications. Yes.

For example, Japanese Patent Application Laid-Open No. 14-019922 discloses a technique for using an RFID system for book management in a library. According to the above publication, a tag (strip IC seal) composed of a loop antenna and an IC chip is attached to an object (book), while a reader / writer that reads data of an IC chip provided on the object is provided. By installing the object in a delivery management device and placing the object at a predetermined position of the delivery management device, the data stored in the IC chip is read by a reader / writer, and taking out and returning of the book is managed.
Japanese Patent Laid-Open No. 14-019922 (page 3-6, FIG. 7)

  In the RFID system having the structure described in the above publication, the reader / writer antenna is fixed to the delivery management device, and the object to which the tag is attached is placed at a predetermined position on the reader / writer antenna. Therefore, the communication state of data between the reader / writer antenna and the tag can be kept good. However, in the case of a structure in which a reader / writer is installed on a fixed device, in order to communicate data with the tag, the object to which the tag is attached must be carried to the device, for example, placed on a shelf. It is inconvenient when managing books that are being used.

  Therefore, there is a method in which the reader / writer is formed in a small card shape and is used by being attached to a portable terminal device such as a PDA. In this method, since the reader / writer can be moved, data can be communicated without moving the object to which the tag is attached. However, if the reader / writer is portable, the reader / writer can be used. Since the antenna size is also reduced, the communication range with the tag is narrowed, and data communication may not be possible depending on the positional relationship between the reader / writer antenna and the tag.

  For example, as shown in FIG. 12, a card-like reader / writer 2 includes a reader / writer main body 4 mounted in a slot or the like of a mobile terminal device, and a reader / writer antenna 3 fixed to the reader / writer main body 4. The reader / writer 2 is brought close to the tag 5 in a state where the antenna axes of the antenna coil 7 embedded in the tag 5 and the antenna axis of the reader / writer antenna 3 face the same direction (in the figure, the reader / writer 2 is Data communication is possible when the reader / writer 2 is moved closer), but when the reader / writer 2 is moved closer to the tag 5 with both antenna axes orthogonal (in the figure, the reader / writer 2 is moved closer from the left side of the tag 5). Cannot communicate data. Therefore, in such a case, the orientation of the antenna axis of the reader / writer antenna 3 is adjusted by changing the orientation of the mobile terminal device itself, but if the orientation of the mobile terminal device is changed, the touch panel or keyboard It becomes difficult to operate and the monitor becomes difficult to see, resulting in a problem that workability is significantly reduced.

  The present invention has been made in view of the above problems, and its main object is to provide a reader or reader / writer that can reliably perform data communication regardless of the positional relationship with the tag, and a structure thereof. There is to do.

In order to achieve the above object, the reader or reader / writer of the present invention is a reader or reader / writer that communicates data with an RFID tag using electromagnetic induction or electromagnetic coupling, and the reader or reader / writer is The circuit is composed of a main body and a loop antenna, and the antenna is rotatably held around a rotation shaft provided in the main body, and a connecting portion between the main body and the antenna A capacity adjusting means whose capacity changes in accordance with the amount of rotation of the antenna is provided. The capacity adjusting means has a base portion on which one of the opposing electrodes of the capacitor is formed and the other of the opposing electrodes. A trimmer capacitor including a rotating portion that rotates with respect to the base portion, wherein the base portion of the trimmer capacitor is fixed to the main body, and the rotating portion is fixed to the antenna It is intended to be.

  Further, in the present invention, both ends of the antenna are fitted into a pair of holes provided on opposite surfaces of the main body so that the antenna sandwiches the main body, and the rotation axis passing through the pair of holes is centered. Thus, the antenna can be rotated.

  In the present invention, the reader or reader / writer may be configured such that the main body can be mounted in a slot of a mobile terminal device, and data acquired by the antenna is processed by the mobile terminal device. it can.

  Thus, according to the present invention, the reader / writer antenna is rotatably held in the reader / writer main body, or the reader / writer antenna is configured to be deformable, and the reader / writer is adapted to the direction of the tag. By making it possible to adjust the angle of the antenna, data can be reliably communicated regardless of the direction of the tag. Furthermore, a capacity adjusting means (for example, a trimmer capacitor) that changes the capacity of the capacitor by rotation is disposed at the connecting portion between the reader / writer main body and the reader / writer antenna, and the antenna of the antenna by the rotation of the reader / writer antenna is arranged. Compensation for synchronization deviations, and low antenna Q value to reduce the influence of impedance deviation due to deformation of the reader / writer antenna, thereby maintaining good data communication with the tag be able to.

  As described above, the structure of the RFID reader / writer and the reader / writer antenna of the present invention has the following effects.

  The first effect of the present invention is to reliably communicate data regardless of the positional relationship between a reader / writer installed in a movable device such as a portable terminal device and a tag attached to a target article. Is that you can.

  The reason is that the reader / writer antenna is rotatably held on the reader / writer main body or the reader / writer antenna is structured to be deformable, and the orientation of the reader / writer main body and the device to which the main body is mounted is changed. This is because the orientation of the reader / writer antenna can be adjusted in accordance with the orientation of the tag.

  In addition, the second effect of the present invention is that it is possible to suppress a deviation in tuning of the antenna and a deviation in impedance due to rotation or deformation of the antenna.

  The reason for this is that when the reader / writer antenna is rotatably held, a trimmer capacitor whose capacitance changes as a result of rotation is disposed at the connecting portion between the reader / writer body and the reader / writer antenna. This is because a deviation in tuning of the antenna can be compensated. Further, when the reader / writer antenna has a deformable structure, the influence of impedance deviation can be reduced by lowering the Q value of the reader / writer antenna.

  As shown in the prior art, there is a method for carrying a card-like reader / writer in a portable terminal device such as a PDA. In this case, the size of the reader / writer antenna may be increased. Because the communication range is narrowed, the range of communication is narrowed. Depending on the positional relationship between the reader / writer antenna and the tag, data communication cannot be performed. When the orientation of the mobile terminal device itself is adjusted, the operability and visibility of the mobile terminal device Problem arises.

  Such a problem occurs because the reader / writer antenna is fixed to the portable terminal device. If the orientation of the reader / writer antenna can be varied, the orientation of the portable terminal device itself can be changed. No need to adjust. However, the conventional reader / writer does not have a mechanism for adjusting the angle of the antenna, and if the reader / writer antenna is moved, the antenna tuning may be shifted or the antenna impedance may be shifted, resulting in data with the tag. It becomes impossible to communicate.

  Therefore, in the present invention, the reader / writer antenna is rotatably held on the reader / writer main body, or the reader / writer antenna is configured to be deformable. Further, the reader / writer main body and the reader / writer antenna A trimmer capacitor whose capacitance is changed by rotation is arranged at the connecting portion, and the capacitance is changed in accordance with the rotation of the reader / writer antenna to compensate for a deviation in tuning of the antenna, or the Q value of the reader / writer antenna To reduce the effect of impedance change. Hereinafter, the specific structure will be described with reference to the drawings.

  First, an RFID reader / writer and its antenna structure according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically showing a configuration of an RFID system according to the present invention, and FIG. 2 is a diagram showing a configuration of a reader / writer and a tag. 3 to 7 are perspective views showing the structure of the reader / writer according to the first embodiment, and FIG. 8 is a perspective view showing a structure example of the capacity adjusting means.

  As shown in FIG. 1, an RFID system 1 according to the present invention includes a card-like, stick-like reader / writer main body 4 and a reader having a structure that can be mounted in a slot of a portable terminal device 10 such as a PDA, a notebook personal computer, or a cellular phone. The reader / writer 2 includes a loop-shaped reader / writer antenna 3 held by the writer main body 4 and a tag 5 such as a card shape, a sheet shape, or a label shape that is attached to an object.

  As shown in FIG. 2, the reader / writer body 4 includes a communication circuit unit 4a for converting transmission / reception signals and an arithmetic processing unit 4b for decoding transmission / reception signals. A writer antenna 3 is connected. The arithmetic processing unit 4 b is connected to a circuit of the mobile terminal device 10 and is configured so that data received by the reader / writer antenna 3 can be used by the mobile terminal device 10. Further, the tag 5 includes a resonance circuit 6 including an antenna coil 7 and a capacitor 8 (the capacitor 8 is not always necessary when the IC 9 having the internal capacitance is provided), and generates a signal also on the tag 5 side. In this case, an IC 9 for calculating and storing data is connected to the resonance circuit 6 and is driven using a built-in power source or a power source supplied from the reader / writer 2. Then, data communication with the reader / writer antenna 3 is performed by adjusting the resonance frequency of the resonance circuit 6 of the tag 5 to a desired communication frequency (for example, 13.56 MHz).

  The present invention is characterized by the structure of the reader / writer antenna 3 held by the reader / writer main body 4. The shape and structure of the reader / writer main body 4 and the tag 5 and the reader / writer 2 are mounted. The type, shape, structure, etc. of the object to which the device or tag 5 is attached are not limited.

  Next, the detailed structure of the reader / writer 2 of this embodiment will be described. As shown in the upper diagram of FIG. 3, the reader / writer 2 of this embodiment includes a card-like reader / writer body 4 that can be mounted in a slot of the mobile terminal device 10 and a wire having a predetermined strength wound in a loop shape. The reader / writer antenna 3 is rotated, and the reader / writer antenna 3 is rotatably held by the reader / writer main body 4 as shown in the lower diagram of FIG. For ease of explanation, the electrical connection structure between the reader / writer antenna 3 and the reader / writer main body 4 is not shown in the figure, but as described above, the reader / writer antenna 3 is The end of the wire is connected to the communication circuit unit 4a inside the main body.

  The wire that constitutes the reader / writer antenna 3 is not particularly limited, but it is preferable that the reader / writer antenna 3 has such strength that it is not easily deformed when rotated around the rotation shaft 11. The wire may be in a state where the metal is exposed, but may be covered with an insulating resin such as rubber.

  3 shows a loop antenna having one turn, but the number of turns of the reader / writer antenna 3 is not limited, and a structure in which a plurality of turns (two in the figure) are wound as shown in FIG. It can be. Further, the shape of the reader / writer antenna 3 is not limited, and may be any shape as long as it functions as an antenna. For example, the reader / writer antenna 3 may be semicircular or elliptical as shown in FIG. Further, the reader / writer antenna 3 may be formed of only a wire. However, if the strength cannot be maintained with only the wire, the reader / writer antenna 3 can be fixed to a reinforcing plate made of a non-metallic material such as plastic.

  3 to 5, the holes 12 are formed on the opposing surfaces of the reader / writer main body 4, and both ends of the reader / writer antenna 3 are fitted into the holes 12, but the reader / writer antenna is used. The rotation structure 3 is not particularly limited as long as the rotation structure rotates around the rotation axis of the reader / writer body 4. For example, as shown in FIG. 6, a cut is provided on one side of the reader / writer body 4. The reader / writer antenna 3 is configured to rotate around a rotation axis provided in the cut, or a hole 12 is formed in a predetermined surface of the reader / writer main body 4 as shown in FIG. Alternatively, the reader / writer antenna 3 may be fitted with the end thereof and rotated with the central axis of the hole 12 as the rotation axis.

  3 to 7, the reader / writer antenna 3 is configured to be able to rotate approximately 360 ° around the rotation axis 11 of the reader / writer main body 4. However, the direction of the antenna axis of the reader / writer antenna 3 is not limited. May be configured to rotate at least 90 ° or more. Further, it is preferable that the reader / writer main body 4 and the reader / writer antenna 3 are tightly fitted to a certain extent so that the rotation position does not shift when the reader / writer antenna 3 is rotated. You may provide the structure which can be stopped in the position (For example, the position where the main plane of the card-like reader / writer main body 4 and the antenna surface of the reader / writer antenna 3 coincide or are orthogonal to each other).

  In the reader / writer antenna 3 having such a structure, when the antenna axis of the antenna coil 7 of the tag 5 and the antenna axis of the reader / writer antenna 3 are largely deviated, data communication cannot be performed. Since it is only necessary to rotate 3 and there is no need to change the orientation of the mobile terminal device 10 itself, it is possible to exchange data without impairing the operability and visibility of the mobile terminal device 10.

  Here, when the reader / writer antenna 3 is rotated, the distance and the positional relationship between the reader / writer antenna 3 and the reader / writer main body 4 or the portable terminal device 10 change, and the tuning of the antenna shifts. Therefore, in this embodiment, in addition to the structures shown in FIGS. 3 to 7, capacity adjusting means for changing the capacity in accordance with the rotation of the reader / writer antenna 3 is provided.

  Specifically, as shown in FIG. 8, for example, a capacitor (capacitor of an opposing semicircular electrode plate that changes its capacitance by rotating it) is connected to the connecting portion between the reader / writer antenna 3 and the reader / writer main body 4. A trimmer capacitor or the like that changes the overlap by rotating one electrode plate is installed, one electrode of the trimmer capacitor is fixed to the reader / writer main body 4, and the other electrode is fixed to the reader / writer antenna 3. When the reader / writer antenna 3 is rotated, the capacitance of the trimmer capacitor is changed in accordance with the degree of rotation to compensate for the tuning deviation.

  What is necessary is just to set suitably the capacitance value and variation | change_quantity of this trimmer capacitor according to the grade of the deviation | shift of antenna tuning. The structure of the capacity adjusting means 13 is not limited to the above structure. For example, a plurality of contacts are provided side by side around the hole 12 of the reader / writer body 4, and capacitors having different capacities are connected to each contact. In addition, a structure in which the reader / writer antenna 3 is sequentially connected to capacitors having different capacities as the reader / writer antenna 3 rotates is also possible.

  By providing the capacity adjusting means 13 having such a structure, even when the distance between the reader / writer antenna 3 and the reader / writer main body 4 or the portable terminal device 10 changes, the capacity adjusting means 13 compensates for the deviation in tuning. Therefore, the data communication with the tag 5 can always be kept good.

  Next, an RFID reader / writer and its antenna structure according to a second embodiment of the present invention will be described with reference to FIGS. 9 to 11 are perspective views showing the structure of the reader / writer according to the second embodiment.

  In the first embodiment described above, the reader / writer antenna 3 is rotated to adjust the direction of the antenna axis. However, if a rotating mechanism is provided, the structure becomes complicated, and the structure is operated by repeating the rotating operation. There is also a risk of wear of parts. Therefore, in this embodiment, the orientation of the antenna axis is adjusted by deforming the reader / writer antenna 3 instead of rotating it.

  Specifically, as shown in FIG. 9, Al or Al provided on the insulating sheet 14 having moderate flexibility (is easily deformed when external force is applied and can retain its shape in the deformed state). The reader / writer antenna 3 is formed by removing a conductive film such as Cu by etching, or applying a conductive paste on the insulating sheet 14 by screen printing, and one end of the reader / writer antenna 3 is connected to the reader / writer It is fixed to the writer main body 4 and connected to the communication circuit section 4 a inside the reader / writer main body 4. With such a structure, the reader / writer antenna 3 can be easily deformed, and its shape is maintained in the deformed state. Therefore, the antenna axis of the antenna coil 7 of the tag 5 and the reader / writer When the antenna axis of the antenna 3 for use is largely deviated, as shown in FIG. 10, data communication with the tag 5 is possible by bending the open end of the reader / writer antenna 3 at an arbitrary angle. Become.

  In addition, the material of the insulating sheet 14 is not particularly limited, and may be any material that does not easily break even if it is repeatedly bent and has an appropriate elasticity. Can be protected with an insulating resin such as rubber. In FIG. 9, the rectangular antenna pattern is wound once on the insulating sheet 14, but the number of windings, the position where the antenna is formed, the shape of the antenna, and the like are required for the reader / writer antenna 3. It can be set appropriately depending on the situation. 9 and 10, the antenna pattern is formed on the insulating sheet 14 having appropriate flexibility. However, as shown in FIG. 11, the antenna pattern similarly has appropriate flexibility (applying external force). The reader / writer antenna 3 may be formed only with a wire) which can be easily deformed and can retain its shape in the deformed state.

  In such a structure, when the reader / writer antenna 3 is deformed, the antenna shape of the reader / writer antenna 3 changes, and tuning and impedance are shifted. Therefore, in this embodiment, the gain is lowered by, for example, inserting a resistor between the reader / writer antenna 3 and the communication circuit unit 4a, thereby lowering the Q value of the antenna. By reducing the Q value, the communication distance is shortened, but the influence of the impedance change can be reduced. The degree of the Q value can be set as appropriate according to the performance required for the reader / writer antenna 3.

  In the above description, the antenna structure of the present invention is applied to the reader / writer antenna. However, the present invention is not limited to the above-described embodiments, and is not limited to the tag antenna or other communication device antenna. The same applies to.

It is a figure which shows typically the structure of the RFID system which concerns on this invention. It is a figure which shows the structure of the reader / writer and tag which concern on this invention. It is a perspective view which shows the structure of the reader / writer based on 1st Example of this invention. It is a perspective view which shows the variation of the structure of the reader / writer based on 1st Example of this invention. It is a perspective view which shows the variation of the structure of the reader / writer based on 1st Example of this invention. It is a perspective view which shows the variation of the structure of the reader / writer based on 1st Example of this invention. It is a perspective view which shows the variation of the structure of the reader / writer based on 1st Example of this invention. It is a perspective view which shows typically the structure of the capacity | capacitance adjustment means of the reader / writer based on 1st Example of this invention. It is a perspective view which shows typically the structure of the reader / writer based on the 2nd Example of this invention. It is a perspective view which shows typically the structure (deformed state) of the reader / writer concerning 2nd Example of this invention. It is a perspective view which shows the variation of the structure of the reader / writer based on 2nd Example of this invention. It is a figure which shows the structure of the conventional RFID system typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RFID system 2 Reader / writer 3 Reader / writer antenna 4 Reader / writer main body 5 Tag 6 Resonant circuit 7 Antenna coil 8 Capacitor 9 IC
DESCRIPTION OF SYMBOLS 10 Portable terminal device 11 Rotating shaft 12 Hole 13 Capacity adjusting means 14 Insulating sheet

Claims (3)

A reader or reader / writer that communicates data with an RFID tag using electromagnetic induction or electromagnetic coupling,
The reader or reader / writer is composed of a main body in which a circuit is formed and a loop antenna.
The antenna is held so as to be rotatable around a rotation shaft provided in the main body,
In the connecting portion between the main body and the antenna, a capacity adjusting means whose capacity changes according to the amount of rotation of the antenna is arranged ,
The capacitance adjusting means comprises a trimmer capacitor including a base portion where one of the opposing electrodes of the capacitor is formed, and a rotating portion where the other of the opposing electrodes is formed and rotated with respect to the base portion,
A reader or a reader / writer , wherein the base portion of the trimmer capacitor is fixed to the main body, and the rotating portion is fixed to the antenna . Both ends of the antenna are fitted into a pair of holes provided on opposite surfaces of the main body so that the antenna sandwiches the main body, and the antenna rotates about a rotation axis passing through the pair of holes. reader or reader / writer according to claim 1, characterized in that. 3. The reader or reader / writer is formed so that the main body can be mounted in a slot of a mobile terminal device, and data acquired by the antenna is processed by the mobile terminal device. Reader or reader / writer.

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