JP2012043101A - Rfid reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hand-held RFID reader having a simple structure and allowing fine adjustment of communication distance.SOLUTION: A hand-held RFID reader 10 includes transmission means 18 for transmitting an electric wave to a tag, and receiving means 18 for receiving the electric wave from the tag. The transmission means 18 includes a patch antenna 18 transmitting an elliptically-polarized wave. The patch antenna 18 is rotatable around a propagation axis of the elliptically-polarized wave with respect to a body 12 on which the patch antenna 18 is mounted.

Description

  The technology disclosed in this specification relates to a hand-held RFID reader. In this specification, the RFID reader includes an RFID reader / writer.

  The RFID reader communicates with tags within a range where radio waves reach and reads information from these tags. Therefore, if a tag exists within a range where radio waves reach, the tag reader may read the tag information even though the tag information is unnecessary. In order to solve such a problem, there is known an RFID reader capable of changing the transmission output of radio waves. The user can change the transmission output of the radio wave of the RFID reader in a stepwise manner by operating an operation button installed on the main body of the RFID reader. When the transmission output is changed, the communication distance of the RFID reader is changed. The user can select a tag to be communicated by changing the communication distance of the RFID reader.

  Patent Document 1 discloses a communication system for an RFID reader configured such that only the tag selected by the auxiliary device transmits information to the RFID reader. Not a choice.

JP 2007-200188 A

  The above-described conventional RFID reader that can change the radio wave transmission output changes the radio wave transmission output step by step, and thus cannot finely adjust the transmission output. For this reason, for example, when two tags exist at different distances, information on both tags is received if the transmission output is set high, while information on both tags is received if the transmission output is set one step lower. There were cases where it was not possible. As described above, the conventional RFID reader cannot finely adjust the transmission output, and cannot appropriately select the tag to be communicated. Although it is conceivable that the transmission output is adjusted in finer steps, in this case, there arises a problem that a circuit and software for changing the transmission output become complicated. Therefore, the present specification provides a handheld RFID reader that has a simple configuration and can finely adjust a communication distance.

The present specification discloses a hand-held RFID reader including a transmission unit that transmits radio waves to a tag and a reception unit that receives radio waves from the tag. In this RFID reader, the transmission means includes a patch antenna that transmits elliptically polarized waves. The patch antenna is rotatable about the traveling axis of the elliptically polarized wave with respect to the main body to which the patch antenna is attached.
“Rotating around the traveling axis of the elliptically polarized wave relative to the main body” means rotating around the traveling axis of at least one elliptically polarized wave transmitted radially from the patch antenna. It means that there is.
One patch antenna may be configured to transmit elliptically polarized waves and receive radio waves from the tag. That is, the patch antenna and the receiving antenna may be provided separately, or these may be configured by one patch antenna.

  In this RFID reader, the patch antenna transmits an elliptically polarized wave, and the patch antenna can be rotated around the traveling axis of the elliptically polarized wave with respect to the main body. On the other hand, since the antenna of the tag is usually a linearly polarized antenna, the tag receives only radio waves in which an electric field / magnetic field vibrates in a specific direction (hereinafter referred to as a receiving direction). When the user rotates the patch antenna with respect to the main body, the amplitude of the electric field / magnetic field of elliptically polarized waves in the receiving direction of the tag changes. For example, if the amplitude of the electric field / magnetic field in the receiving direction of the tag becomes a predetermined magnitude when elliptical polarization is transmitted with the patch antenna set to a predetermined angle, the angle of the patch antenna is changed from the predetermined angle. Then, the amplitude of the electric field / magnetic field in the receiving direction of the tag increases or decreases from the predetermined magnitude. If the amplitude of the electric field / magnetic field in the receiving direction of the tag is large, the communication distance of the RFID reader becomes long. If the amplitude of the electric field / magnetic field in the receiving direction of the tag is small, the communication distance of the RFID reader becomes short. Therefore, the user can change the communication distance of the RFID reader by rotating the patch antenna. That is, the user can select a tag to be communicated from among a plurality of tags placed at different distances by changing the communication distance of the RFID reader. Further, this RFID reader can change the communication distance with a simple configuration in which the patch antenna is physically rotated. The angle of the patch antenna can be set to an arbitrary angle. Since the radio wave transmitted by the patch antenna is elliptically polarized, the communication distance of the RFID reader changes smoothly according to the angle of the patch antenna. Therefore, this RFID reader can continuously change the communication distance. For this reason, the user can finely adjust the communication distance of the RFID reader by rotating the patch antenna little by little. For example, when two tags exist at different close distances, the user may set the communication distance of the RFID reader to a communication distance that allows communication with only the near tag without communicating with the far tag. it can.

  In the RFID reader described above, the patch antenna is preferably rotatable only within an angle range of 0 to 180 degrees.

The function of time of an elliptically polarized electric or magnetic field draws an ellipse. Therefore, both the angle at which the electric field / magnetic field amplitude is maximum and the angle at which the electric field / magnetic field amplitude is minimum always exist within the range of 0 to 180 degrees. Therefore, if the patch antenna is rotated within an angle range of 0 to 180 degrees, the communication distance can be adjusted from the maximum value to the minimum value. In addition, by restricting the rotation angle of the patch antenna in this way, it is possible to prevent wiring twisting and the like.

  The RFID reader described above has a patch antenna fixed thereto, a rotating member that rotates together with the patch antenna, a contact portion that contacts the rotating member in the direction of the rotation axis of the rotating member, and one of the rotating member and the contact portion as the other. It is preferable to further include a spring that biases toward the surface.

  According to such a configuration, the rotating member is pressed against the contact portion by the spring. Therefore, it is possible to prevent the rotating member from unintentionally rotating and changing the angle of the patch antenna during use of the RFID reader.

  The RFID reader described above preferably has a grip portion formed on the main body. And it is preferable that the patch antenna is installed in the position adjacent to a holding part.

  According to such a configuration, when the user holds the grip portion with one hand, the angle of the patch antenna can be easily changed with the finger.

1 is a front view of an RFID reader / writer 10. FIG. FIG. 3 is a side view of the RFID reader / writer 10. FIG. 3 is a rear view of the RFID reader / writer 10. Sectional drawing of the antenna unit 16. FIG. The expanded sectional view of the contact part of the outer side case 16c and the inner side case 16b. The enlarged view of the antenna unit 16. FIG. The enlarged view of the antenna unit 16. FIG. The graph which shows the axial ratio of the elliptically polarized wave which the patch antenna 18 transmits. 4 is an explanatory diagram of a communication distance of the RFID reader / writer 10. FIG.

The features of the RFID reader of the embodiment described below will be listed.
(Feature 1) The patch antenna can rotate relative to the main body about an axis perpendicular to the radiation conductive plate.
(Feature 2) The rotating member is rotatably engaged with the main body by a screw groove. The spring biases the thread of the rotating member toward the thread of the main body.

  An RFID reader according to an embodiment will be described. As shown in FIGS. 1 to 3, the RFID reader / writer 10 includes a main body case 12. A barcode reader 14 is installed at the top of the front surface of the main body case 12. The barcode reader 14 reads information from the barcode. An antenna unit 16 is installed below the bar code reader 14 in front of the main body case 12. The antenna unit 16 has a built-in patch antenna 18. The patch antenna 18 communicates with the tag wirelessly. A grip portion 22 is formed below the antenna unit 16 of the main body case 12. The user can use the RFID reader / writer 10 by holding the holding unit 22. A display 24 is installed on the upper back of the main body case 12. The display 24 displays information read from the barcode by the barcode reader 14, information read from the tag by the patch antenna 18, and various other information. An operation panel 26 having a plurality of key buttons is installed below the display 24 on the back surface of the main body case 12 (that is, the back surface of the grip portion 22). The user can operate the operation panel 26 with a hand holding the holding unit 22.

  As shown in FIG. 4, the antenna unit 16 includes a front cover 16a, a patch antenna 18, an inner case 16b, a spring 20, and an outer case 16c. The outer case 16c has a bottomed cylindrical shape. The outer case 16c is fixed to the main body case 12 in a state where the outer case 16c is inserted into the hole 12a formed in the main body case 12 from the bottom side. The inner case 16b has a bottomed cylindrical shape. The inner case 16b is fitted into the outer case 16c from the bottom side. FIG. 5 shows an enlarged cross-sectional view of a contact portion between the outer case 16c and the inner case 16b. As shown in FIG. 5, screw grooves are formed on the inner peripheral surface of the outer case 16c, and screw grooves corresponding to the screw grooves of the outer case 16c are formed on the outer peripheral surface of the inner case 16b. . The inner case 16b is screwed into the outer case 16c so that these screw grooves are screwed together. Therefore, the inner case 16b can rotate with respect to the outer case 16c around the rotation shaft 40 of FIG. The spring 20 is disposed between the bottom of the outer case 16c and the bottom of the inner case 16b in a compressed state. The spring 20 urges the inner case 16b toward the right side of FIG. Therefore, as shown in FIG. 5, the right side surface 50a of the thread of the inner case 16b is pressed against the left side surface 50b of the thread of the outer case 16c. Thereby, the inner case 16b is fixed to the outer case 16c. The front cover 16a has a substantially disc shape. The front cover 16a is fixed to the inner case 16b and closes the opening of the inner case 16b. The patch antenna 18 is composed of a laminated body of a ground conductive plate 18a, a dielectric substrate 18b, and a radiation conductive plate 18c. The patch antenna 18 is fixed to the front cover 16a so that the radiating conductive plate 18c contacts the front cover 16a while being accommodated in the inner case 16b. The surface of the radiation conductive plate 18c of the patch antenna 18 is perpendicular to the rotation axis 40 described above.

  In a state where no force is applied to the front cover 16a, the inner case 16b is fixed to the outer case 16c by the biasing force of the spring 20. When the user applies a force to rotate the front cover 16a around the rotation axis 40, the surface 50a in FIG. 5 slides with respect to the surface 50b, and the inner case 16b rotates with respect to the outer case 16c. That is, the inner case 16b, the front cover 16a, and the patch antenna 18 are integrally rotated with respect to the main body case 12. Accordingly, for example, the angle of the patch antenna 18 with respect to the main body case 12 can be changed to the angle shown in FIGS. As shown in FIGS. 6 and 7, a convex portion 30 is formed on the outer peripheral surface of the front cover 16 a so as to protrude outward from the outer peripheral surface. In addition, two stoppers 60 and 62 are formed on the main body case 12. The stoppers 60 and 62 are formed at positions where they can come into contact with the convex portion 30 when the front cover 16a rotates. The stoppers 60 and 62 limit the rotatable range of the front cover 16a (that is, the patch antenna 18) by contacting the convex portion 30. By the stoppers 60 and 62, the rotatable range of the patch antenna 18 is limited to a range of 180 degrees. Below, the angle of the patch antenna 18 is demonstrated using the angle measured clockwise from the angle shown in FIG. That is, the angle of the patch antenna 18 shown in FIG. 6 is called 0 degree, and the angle of the patch antenna 18 shown in FIG. 7 is called 90 degrees.

  As shown by the arrow 100 in FIGS. 2 and 4, the patch antenna 18 transmits radio waves radially with the direction perpendicular to the radiation conductive plate 18 c as the center. That is, the arrow 100 indicates the central axis of the directivity of the patch antenna 18. As shown in FIG. 4, the central axis 100 of the directivity of the patch antenna 18 substantially coincides with the rotation axis 40 of the patch antenna 18.

FIG. 8 shows the axial ratio of the radio wave transmitted by the patch antenna 18. The circumferential axis in FIG. 8 indicates the angle around the traveling direction of the radio wave. Further, the radial axis in FIG. 8 indicates the electric field amplitude of the radio wave. As illustrated, the patch antenna 18 transmits elliptically polarized waves. When the patch antenna 18 is at an angle of 0 degrees shown in FIG. 6, the electric field amplitude E ₀ indicated by the long axis in FIG. 8 is obtained in the vertical direction in FIG. When the patch antenna 18 is at an angle of 90 degrees shown in FIG. 7, the electric field amplitude E ₉₀ indicated by the short axis in FIG. 8 is obtained in the vertical direction in FIG. Thus, the direction of the elliptically polarized wave can be changed by rotating the patch antenna 18.

  The RFID reader / writer 10 transmits an elliptically polarized signal from the patch antenna 18 to the tag, and receives a radio wave transmitted from the tag by the patch antenna 18. For example, when reading information from the tag, a read command is transmitted from the patch antenna 18 toward the tag by elliptically polarized waves. The tag receives elliptical polarization to obtain power and to receive a read command. Then, the tag reads information corresponding to the read command from the memory and transmits the information by radio waves. The RFID reader / writer 10 receives the radio wave from the tag by the patch antenna 18 to obtain the information. When writing information to the tag, a write command and data are transmitted from the patch antenna 18 toward the tag by elliptically polarized waves. The tag receives the elliptically polarized wave, thereby obtaining power and receiving a write command and data. The tag then writes the received data to the memory. Further, the tag transmits the writing result by radio waves. The RFID reader / writer 10 receives the writing result by receiving the radio wave from the tag by the patch antenna 18.

Next, a method for changing the communication distance by the RFID reader / writer 10 will be described. Consider a state in which the tags 70 to 74 are placed at different distances from the RFID reader / writer 10 as shown in FIG. The antennas included in the tags 70 to 74 are linearly polarized antennas. Therefore, the tags 70 to 74 receive radio waves in which an electric field / magnetic field vibrates in a specific direction (hereinafter referred to as a receiving direction). In the following description, it is assumed that the vertical direction in FIG. In the state shown in FIG. 9, when the angle of the patch antenna 18 is 0 degree, the electric field amplitude of elliptically polarized waves in the receiving direction of the tags 70 to 74 becomes the maximum (electric field amplitude E _{0 in} FIG. 8). Therefore, the RFID reader / writer 10 can communicate with all of the tags 70 to 74. Thereafter, the angle of the patch antenna 18 is changed to 45 degrees, the electric field amplitude of the elliptically polarized in the receive direction of the tag 70 to 74 is lowered to a value indicating the amplitude E ₄₅ of FIG. For this reason, the communication distance of the RFID reader / writer 10 decreases. In this case, the RFID reader / writer 10 communicates with the tags 70 and 72 and does not communicate with the tag 74. Thereafter, when the angle of the patch antenna 18 is changed to 90 degrees, the electric field amplitude of elliptically polarized waves in the receiving direction of the tags 70 to 74 becomes the minimum (electric field amplitude E _{90 in} FIG. 8). For this reason, the communication distance of the RFID reader / writer 10 further decreases. In this case, the RFID reader / writer 10 communicates only with the tag 70 and does not communicate with the tags 72 and 74. Thus, the communication distance of the RFID reader / writer 10 can be changed by changing the angle of the patch antenna 18.

  As described above, in the RFID reader / writer 10, the communication distance of the RFID reader / writer 10 can be changed by rotating the patch antenna 18 with respect to the main body case 12. Thereby, a tag to be communicated can be selected from a plurality of tags. In particular, since the angle of the patch antenna 18 can be adjusted to an arbitrary angle, the communication distance can be finely adjusted. For this reason, the communication distance of the RFID reader / writer 10 can be adjusted to an optimum distance. For example, even when two tags exist at a distance close to each other, the communication distance can be adjusted so that only one tag can communicate. Further, since the radio wave to be transmitted is elliptically polarized, when the patch antenna 18 is rotated, the electric field amplitude (or magnetic field amplitude) in the tag receiving direction changes gently. Therefore, the communication distance of the RFID reader / writer 10 can be easily adjusted.

  Further, the RFID reader / writer 10 can change the communication distance by rotating the patch antenna 18. Therefore, the user can easily change the communication distance without performing complicated key operations. Further, since the RFID reader / writer 10 does not require a circuit for changing the communication distance, the RFID reader / writer 10 does not increase in size.

  Further, according to the RFID reader / writer 10, the communication distance can be set so that only the necessary tag can be communicated by rotating the patch antenna 18 while performing the communication operation with the tag in the field. Instead of inputting a numerical value such as a communication distance, the communication distance can be set depending on whether or not communication is actually possible, so that the communication distance can be adjusted sensuously.

  Further, in the RFID reader / writer 10, the stoppers 60 and 62 allow the patch antenna 18 to rotate only within an angle range of 0 to 180 degrees. As shown in FIG. 8, in the elliptically polarized wave, both the angle at which the electric field amplitude becomes the maximum value and the angle at which the electric field amplitude becomes the minimum exist within an angle range of 0 to 180 degrees. Therefore, regardless of the angle at which the tag is arranged with respect to the RFID reader / writer 10, the communication distance is adjusted from the maximum value to the minimum value by rotating the patch antenna 18 within the angle range of 0 to 180 degrees. can do. Further, by restricting the rotation angle of the patch antenna 18 in this way, it is possible to prevent twisting of wiring (for example, a coaxial cable) connected to the patch antenna 18.

  Further, in the RFID reader / writer 10, the spring 20 urges the inner case 16 b along the rotation axis 40 to press the thread surface 50 a of the inner case 16 b against the thread surface 50 b of the outer case 16 c. Yes. As a result, the inner case 16b is fixed to the outer case 16c. Thus, since the inner case 16b is fixed by the spring 20, it is possible to prevent the angle of the patch antenna 18 from unintentionally changing during use of the RFID reader / writer 10.

  In the RFID reader / writer 10, the patch antenna 18 is provided adjacent to the grip portion 22. Therefore, the user can hold the grip portion 22 with one hand and adjust the angle of the patch antenna 18 with the finger.

  A dotted line 110 in FIG. 2 indicates a line connecting the end of the barcode reader 14 and the lower end of the main body case 12. As shown in FIG. 2, the antenna unit 16 is installed at a position that does not protrude outward from the dotted line 110. Therefore, when the barcode reader 14 falls, an impact is not directly applied to the antenna unit 16. This makes it difficult for the antenna unit 16 to be damaged.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: RFID reader / writer 12: body case 14: bar code reader 16: antenna unit 16a: front cover 16b: inner case 16c: outer case 18: patch antenna 18a: ground conductive plate 18b: dielectric substrate 18c: radiation conductive plate 20 : Spring 22: Holding part 24: Display 26: Operation panel 30: Convex part 60: Stopper 62: Stopper

Claims (4)

A handheld RFID reader comprising a transmission means for transmitting radio waves to a tag and a reception means for receiving radio waves from the tag,
The transmission means includes a patch antenna that transmits elliptically polarized waves,
An RFID reader, wherein the patch antenna is rotatable about an axis of travel of elliptically polarized waves with respect to a main body to which the patch antenna is attached.   The RFID reader according to claim 1, wherein the patch antenna is rotatable only within an angle range of 0 to 180 degrees. The patch antenna is fixed, and a rotating member that rotates together with the patch antenna;
A contact portion that contacts the rotating member in the rotation axis direction of the rotating member;
A spring that biases one of the rotating member and the contact portion toward the other,
The RFID reader according to claim 1, further comprising: The body has a gripping part,
The RFID reader according to any one of claims 1 to 3, wherein a patch antenna is attached to a position adjacent to the grip portion.

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