JP4203410B2 - Wireless tag recognition device - Google Patents

Description

  The present invention relates to a wireless tag recognition device that recognizes a wireless tag in a non-contact manner using radio waves, reads information stored in a memory of the wireless tag, and writes information in the memory.

  In recent years, wireless tags that have a memory that can store and retain a unique ID and that can rewrite information and that can read IDs and write and read arbitrary information by non-contact communication have attracted attention. The wireless tag is a small and lightweight tag including a small antenna and an IC chip, and is attached to the surface of the article or embedded in the article to be provided on the article. The IC chip includes a nonvolatile memory and a control circuit that modulates information in the memory into a radio wave (response radio wave) in response to a radio wave (inquiry radio wave) received by the antenna and transmits the radio wave via the antenna. Is provided.

On the other hand, a device that recognizes this type of wireless tag, that is, a wireless tag recognition device that reads and writes information by recognizing the ID of a wireless tag, for example, connects an antenna that supports radio wave transmission and reception of 2,45 GHz microwaves. is doing. Then, by sending an inquiry radio wave from this antenna and receiving a response radio wave from the radio tag to the inquiry radio wave by the antenna, all the radio tags placed in the communication area (tag recognition area) are collectively It comes to recognize. In other words, the information of the wireless tag outside the antenna communication area cannot be recognized. Therefore, conventionally, in addition to the antenna, a radio wave reflector that includes a parabolic curve that reflects the radio wave radiated from this antenna or a part of a similar curve is provided, and the radio wave that passes through the radio tag without being irradiated is reflected. There has been known a technique in which a plate is reflected inward to prevent the scattering of radio waves and to effectively use radio waves from an antenna (for example, see Patent Document 1).
JP2003-249872A

  However, when a radio wave reflector is installed facing the antenna, the electric field strength of the radio wave from the antenna is amplified or attenuated by the overlapping of the wavelengths of the reflected waves. For this reason, there is no problem because the electric field intensity of the radio wave radiated from the antenna is high at a part close to the antenna, but the electric field intensity of the radio wave radiated from the antenna is weak at a part away from the antenna, that is, a part near the radio wave reflector. In addition, there is a problem in that the electric field strength is further attenuated by the reflected wave and a region where the electric field strength necessary for recognition of the wireless tag cannot be obtained is generated, and the recognition rate is lowered.

  The present invention has been made based on such circumstances, and an object of the present invention is to provide a wireless tag recognition device that can obtain a high recognition rate even at a site away from an antenna.

The present invention comprises an antenna having at least a tag recognition area as a communication area, and a wireless tag for recognizing a wireless tag located in the tag recognition area by receiving a response radio wave from the radio tag in response to an inquiry radio wave from the antenna. In the recognition device, a radio wave reflector with a flat radio wave reflection surface that reflects the radio wave radiated from the antenna is provided at a position facing the antenna across the tag recognition area, and the interrogation radio wave is transmitted from the antenna. , by changing the direction of the direction and away from the vicinity of the relative distance between the signal reflection surface of the antenna and the radio wave reflecting plate, Ru varying the region to be amplified than the electric field strength electric field strength of the traveling wave by the overlap of the reflected wave It is what I did.

  According to the present invention in which such a measure is taken, it is possible to provide a wireless tag recognition device that can obtain a high recognition rate even at a site distant from the antenna.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Note that this embodiment is a product constructed in a supermarket or the like, in which the sales data of the customer-purchased product is registered by reading the memory information of the wireless tag attached to the customer-purchased product put in the shopping basket. This is a case where the present invention is applied to a wireless tag recognition device of a sales registration system.

  FIG. 1 is a block diagram showing a main configuration of the present embodiment, and the wireless tag recognition device includes a tag recognition processing unit 10 and a tag recognition table 20. The tag recognition processing unit 10 includes a host interface 11 that controls data communication with a higher-level model of the device (a POS terminal 30 in this embodiment), a controller 12 including a CPU, a ROM, a RAM, and the like. A modulation unit 13 that modulates given data into a modulation signal suitable for wireless communication, an amplification process on the modulation signal, and transmission as an inquiry radio wave from an antenna 21 provided on the tag recognition base 20, reception by the antenna 21 A receiving unit 15 for amplifying the radio signal, a demodulating unit 16 for demodulating data from the amplified radio signal and supplying the demodulated signal to the controller 12, and a motor driver 17 for switching between driving and stopping of a lifting motor 25 described later under the control of the controller 12. It is configured.

  The tag recognition table 20 is an article (a product in this embodiment) that is fixed in a tag recognition area A that is virtually set in a space below the antenna 21 and the antenna 21 and is attached with a wireless tag. , A radio wave reflecting plate 23 that reflects the radio wave radiated from the antenna 21, and the radio wave reflecting plate 23 is attached to the table 22. The reflector plate raising / lowering mechanism 24 and the raising / lowering motor 25 are used as raising / lowering means for raising / lowering up and down on the lower side.

  FIG. 2 is a structural diagram of the tag recognition base 20, wherein FIG. 2A schematically shows the structure viewed from the side, and FIG. 2B schematically shows the structure viewed from the front side. Show. A column 26 is erected from the rear center of the table 22, and an antenna mounting plate 27 is provided at the upper end of the column 26. The antenna mounting plate 27 is fixed immediately above the table 22 in parallel with the table surface. The antenna 21 is attached to the lower surface of the antenna attachment plate 27.

  A radio wave reflector 23 is provided under the table 22 so as to face the antenna 21. The radio wave reflector 23 is disposed on a reflector lifting mechanism 24 that expands and contracts by the power of an elevator motor 25 (not shown), and moves vertically up and down as indicated by the arrows in the figure by extension and contraction of the reflector lifting mechanism 24. It has become.

  As shown in the figure, a shopping basket 40 in which customer-purchased products 41, 42, and 43 are stored is placed on the table 22. When the tag recognition processing unit 10 is activated in this state, the antenna 21 communicates with the wireless tags attached to the products 41, 42, and 43, and the wireless tag is recognized by the tag recognition processing unit 10. It is like that.

  That is, when the controller 12 of the tag recognition processing unit 10 receives an activation command from the POS terminal 30 that is a higher-level model, the controller 12 executes the processing shown in the flowchart of FIG. First, as ST (step) 1, a data signal corresponding to the inquiry radio wave is given to the modulation unit 13 to start transmission of the inquiry radio wave. In ST2, the operation of the lifting motor 25 is started via the motor driver 17.

  Thereby, the inquiry radio wave modulated by the modulation unit 13 and amplified by the transmission unit 14 is periodically transmitted from the antenna 21 toward the tag recognition area. In addition, the reflector lift mechanism 24 is extended by the rotation of the lift motor 25, and the radio wave reflector 23 is repeatedly raised and lowered. At this time, the wireless tags attached to the products 41, 42, and 43 stored in the shopping basket 40 operate when receiving the inquiry radio wave with a necessary and sufficient electric field strength, and store the ID and product information stored in the memory. Etc. are transmitted as response radio waves. The response radio wave is received by the antenna 21, demodulated by the receiving unit 15 and the demodulating unit 16, and recognized by the controller 12. The data of each wireless tag recognized by the controller 12 is transmitted to the POS terminal 30 via the host interface 11, and the sales data of the customer-purchased product is registered based on the product information in the data.

  Thereafter, the controller 12 waits for a recognition end command from the POS terminal 30 as ST3. If a recognition end command is received, the data signal corresponding to the inquiry radio wave is stopped in ST4 and the transmission of the inquiry radio wave is stopped. Further, the controller 12 waits for the radio wave reflector 23 rising or descending to reach the preset home position as ST5. For example, when it is detected that the home position has been reached by a signal from a sensor (not shown), the operation of the lift motor 25 is stopped via the motor driver 17 in ST6, and this process is terminated.

  Here, the controller 12 transmits distance inquiry means for changing the relative distance between the antenna 21 and the radio wave reflector 23 while transmitting the inquiry radio wave from the antenna 21. Specifically, the controller 12 sends the inquiry radio wave from the antenna 21. In the meantime, the elevating means (elevating motor 25, reflecting plate elevating mechanism 24) is operated to move the radio wave reflecting plate 23 up and down, thereby constituting distance changing means for changing the relative distance between the antenna 21 and the radio wave reflecting plate 23. ing. The controller 12 constitutes tag recognition means for recognizing the wireless tag located in the tag recognition area A from the response radio wave received by the antenna 21.

  FIG. 4 is a graph showing the relationship between the electric field intensity (vertical axis) of the radio wave radiated from the antenna 21 and the distance (horizontal axis) from the antenna 21. A solid line M in the figure indicates a state where the radio wave reflector 23 is not present. The broken line N indicates the time when the radio wave reflector 23 is located at a distance D from the antenna 21. Further, the electric field strength P indicates the lowest electric field strength at which the wireless tag that has received the inquiry radio wave can operate normally.

  As shown in the figure, when there is no radio wave reflector 23, the electric field intensity P of the radio wave radiated from the antenna 21 decreases as the distance from the antenna 21 increases. And if it exceeds predetermined distance D2, it will fall below electric field strength P. However, this distance D2 fluctuates back and forth under the influence of noise from the external environment.

  On the other hand, when the radio wave reflecting plate 23 is provided, the radio wave (traveling wave) radiated from the antenna 21 overlaps with the reflected wave from the radio wave reflecting plate 23, so that it is lowered while repeating amplification and attenuation. The increase rate and attenuation rate are larger as the distance from the reflection surface of the radio wave reflection plate 23 is closer.

  FIG. 6 shows a composite wave of a traveling wave and a reflected wave at a distance of one wavelength (λ) from the reflecting surface of the radio wave reflector 23 when the tag recognition table 20 of the present embodiment is installed in an ideal space without noise. It is a graph showing a waveform change, in which a thick solid line S0 indicates when the traveling wave phase is 0 degrees, a thin solid line S1 indicates when the traveling wave phase is 15 degrees, and a thick broken line S2 indicates the traveling wave phase. Indicates a time when the phase of the traveling wave is 45 degrees, and an alternate long and short dash line S4 indicates a time when the phase of the traveling wave is 90 degrees.

  As is apparent from the figure, the combined wave has the maximum amplitude at a position of 1/2 wavelength from the reflecting surface. That is, the electric field strength is amplified. On the contrary, the amplitude is “0” at the position of the quarter wavelength and the distance of the quarter wavelength from the reflecting surface. That is, the electric field strength is attenuated. Incidentally, since the wavelength is about 12 cm in the case of 2.45 GHz microwave, the electric field strength increases at a point about 6 cm ahead of the radio wave reflector 23 and the electric field strength decreases at points about 3 cm and 9 cm ahead.

FIG. 5 shows the waveform of the traveling wave, the waveform of the reflected wave, and the waveform of the combined wave at points D1, D2, and D3 (D1 <D2 <D3) from the antenna 21 in FIG.
At the point of the distance D1 that is relatively close to the antenna 21, the electric field strength is attenuated by the overlapping of the reflected waves due to the reflection plate 23 being located at the distance D, but the attenuation rate is small, and the radio wave radiated from the antenna 21 (progress The radio tag placed at this point reliably reacts to the inquiry radio wave from the antenna 21 regardless of the presence or absence of the radio wave reflector 23.

  At a point of distance D2 where the electric field strength is far from the antenna 21 and there is no radio wave reflector 23 and the electric field strength P approaches the electric field strength P, the electric field strength is attenuated by the overlapping of the reflected waves and becomes lower than the electric field strength P. The wireless tag placed in is not responsive to inquiry radio waves. However, even if there is no radio wave reflector 23, the recognition rate is a low region due to external noise and environmental influences.

  At a point at a distance D3 where the electric field intensity is further away from the antenna 21 and the radio wave reflection plate 23 is not present and the electric field intensity P is lower than the electric field intensity P, the electric field intensity is amplified by the overlapping of the reflected waves and becomes higher than the electric field intensity P. Therefore, the wireless tag placed at this point responds to the inquiry radio wave due to the effect of the radio wave reflector 23.

  In the present embodiment, while the inquiry radio wave is transmitted from the antenna 21, the reflector 21 is operated by operating the lift motor 25 to raise and lower the radio wave reflector 23 to the upper limit, thereby causing the antenna 21 and the radio wave to move. The relative distance D with respect to the reflecting plate 23 is changed. As a result, the region in which the electric field intensity is amplified more than the electric field intensity of the traveling wave also fluctuates in the vertical direction due to the overlapping of the reflected waves.

  For example, as shown in FIG. 7A, when the radio wave reflector 23 is positioned at the highest position just below the table 22, the electric field strength is amplified by the overlapping of the reflected waves to become a strong electric field. Assume that the region B is located approximately in the middle between the antenna 21 and the table 22. In this case, since the wireless tag 51 attached to the product 41 stored in the shopping basket 40 (not shown) is located in the region B, it reacts reliably and is recognized and processed by the tag recognition processing unit 10.

  From this state, the radio wave reflector 23 descends. Then, as shown in FIG. 5B, when the radio wave reflector 23 is lowered approximately half from the highest position, the area B is also lowered to the table 22 side, and the wireless tag 52 attached to the product 42 is located in the area B. to go into. Thereby, the wireless tag 52 reacts reliably and is recognized and processed by the tag recognition processing unit 10.

  Furthermore, it is assumed that the radio wave reflector 23 is lowered and the radio wave reflector 23 is positioned at the lowest position as shown in FIG. As a result, the region B descends to just above the table 22. At this time, since the wireless tag 53 attached to the product 43 is located in the region B, it reacts with certainty and is recognized and processed by the tag recognition processing unit 10.

  In this way, in the tag recognition area A1 on the table 22 side from the substantially intermediate point between the antenna 21 and the table 22, the strong electric field region B moves up and down corresponding to the up and down movement of the radio wave reflector 23. A wireless tag located in the recognition area A1 can be reliably recognized. In addition, in the tag recognition area A2 on the antenna 21 side from the substantially intermediate point between the antenna 21 and the table 22, the electric field strength of the radio wave (traveling wave) radiated from the antenna 21 is sufficiently high. The wireless tag located can also be recognized reliably. Thus, according to the present embodiment, the recognition rate of the wireless tag in the tag recognition area A (A1 + A2) can be remarkably improved.

  In particular, since a high recognition rate can be obtained even at a site away from the antenna 21 that has conventionally had a low recognition rate, it is very useful. For example, as in the present embodiment, when the wireless tags attached to a plurality of products put in the shopping basket 40 are collectively read in a non-contact manner, the shopping basket 40 is placed on the table 22, but at this time If the distance between the antenna 21 and the table 22 is small, it is difficult to place the shopping basket 40 and the product may not be placed when the product protrudes from the top of the basket. On the other hand, according to the present embodiment, since the recognition rate of the part away from the antenna 21 is increased, the distance between the antenna 21 and the table 22 can be designed to be long, and the problem as described above can be avoided. be able to.

The present invention is not limited to the one embodiment.
For example, in the above-described embodiment, the case where the present invention is applied to the wireless tag recognition device of the merchandise sales registration system has been described. However, the present invention is not limited to this, for example, a registered mail in a mail bag. It is also possible to apply the present invention to a wireless tag recognition device of a system that collectively reads wireless tags attached to the above.

  Moreover, in the said embodiment, although the antenna 21 was arranged above the table 22 for mounting the article | item with which the radio | wireless tag was attached | subjected, and the electromagnetic wave reflecting plate 23 was arranged below, the antenna 21 is arranged below. The radio wave reflector 23 may be disposed above. Further, an antenna may be arranged on one side, and the radio wave reflector 23 may be arranged on the other side facing the antenna. However, when applied to the wireless tag recognition device of the merchandise sales registration system, it is easier to place the shopping basket 40 on the table 22 when the antenna 21 is disposed above the table 22 and the radio wave reflector 23 is disposed below. In addition, the space of the checkout counter can be used effectively, which is effective.

  In the above embodiment, the radio wave reflector 23 is moved in order to change the relative distance between the antenna 21 and the radio wave reflector 23. For example, the antenna 21 may be moved with the support 26 being telescopic. . Further, the moving mechanism is not particularly limited, and can be changed as appropriate according to the needs of the user.

The block diagram which shows the principal part structure in one embodiment of this invention. The side surface schematic diagram and front surface schematic diagram which show the structure of the tag recognition stand in the embodiment. The flowchart which shows the principal part of the control procedure which the controller of the tag recognition process part in the embodiment performs. The graph which shows the relationship between the electric field strength of the electromagnetic wave radiated | emitted from an antenna in the same embodiment, and the distance from an antenna. The schematic diagram which shows an example of the wave of a traveling wave, a reflected wave, and a synthetic wave in each distance point from an antenna. The graph which shows the waveform change of the synthetic wave of a traveling wave and a reflected wave in the distance of 1 wavelength from the reflective surface of the electromagnetic wave reflector in an ideal space without noise. The schematic diagram which shows the position change of the strong electric field area | region by the change of the relative distance of an antenna and a radio wave reflector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Tag recognition process part, 12 ... Controller, 17 ... Motor driver, 20 ... Tag recognition stand, 21 ... Antenna, 22 ... Table, 23 ... Radio wave reflector, 24 ... Reflector raising / lowering mechanism, 25 ... Elevator motor

Claims (2)

A wireless tag recognition device comprising an antenna having at least a tag recognition area as a communication area, and receiving a response radio wave from a radio tag with respect to an inquiry radio wave from the antenna by the antenna to recognize a radio tag located in the tag recognition area In
A radio wave reflector placed on a position facing the antenna across the tag recognition area and reflecting radio waves radiated from the antenna , with a radio wave reflection surface as a plane ;
While the inquiry radio wave is being transmitted from the antenna, the relative distance between the antenna and the radio wave reflection surface of the radio wave reflector is changed to a close direction and a separate direction, and the electric field strength is a traveling wave due to the overlap of the reflected waves. a distance changing means for the Ru varying the region to be amplified than the electric field strength,
A wireless tag recognition device comprising: An antenna for transmitting an inquiry radio wave to the radio tag in the tag recognition area and receiving a response radio wave from the radio tag for the inquiry radio wave;
A table for placing an article that is fixed in the tag recognition area below the antenna and to which the wireless tag is attached;
A radio wave reflector that is provided at a position facing the antenna across the table and reflects radio waves radiated from the antenna;
Elevating means for elevating and lowering the radio wave reflector on the lower side of the table;
While changing the inquiry radio wave from the antenna, distance changing means for moving the radio wave reflector up and down by operating the elevating means,
Tag recognition means for recognizing a wireless tag located in the tag recognition area from a response radio wave received by the antenna;
A wireless tag recognition device comprising:

Images