JP2008289192A - Tag communication apparatus, tag communication system, tag communication method of tag communication apparatus, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tag communication apparatus capable of covering a wide communication area, with no communication disabled portion, using a small number of antennas with strong directivity. <P>SOLUTION: An RFID reader/writer 2 which performs radio communication with an RFID tag 3 via a radio wave, comprises a beam scan antenna 40 capable of scanning a radio beam to be transmitted and a control unit 20 for controlling the scan. The beam scan antenna 40 transmits a beam to a part of the space wherein the RFID tag 3 may be present, is disposed to communicate with the RFID tag 3 existing in the space by performing the scan by the control unit 20, and transmits, in the space, such a beam as to make a radio intensity different between a direct wave DW of the beam directly transmitted from the beam scan antenna 40 to the RFID tag 3 and a reflection wave RW of the beam reflected on a floor surface 7 and then transmitted to the RFID tag 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tag communication device, a tag communication system, a tag communication method of a tag communication device, and a program for performing wireless communication with an RFID tag via radio waves.

  Recently, RFID technology in which a tag communication device that is a reader and / or writer communicates wirelessly with an RFID (Radio Frequency Identification) tag (wireless tag) is being used. Further, RFID tags are expected to replace barcodes, particularly in the field of logistics, and are expected to spread explosively in the near future.

  Communication methods between the RFID tag and the tag communication device include an electromagnetic induction method and a microwave method. The electromagnetic induction method is used in a frequency band of 125 k to 135 kHz band or 13.56 MHz band. On the other hand, the microwave system is used in a frequency band such as a 2.45 GHz band, and is considered to be used in a so-called UHF band around 800 MHz to 960 MHz.

At present, the electromagnetic induction method is spreading. However, in general, the microwave method is easier to extend the communication distance than the electromagnetic induction method, and the size of the RFID tag antenna can be reduced as the frequency band becomes higher. The spread of the wave method is expected. For this reason, the development of microwave-type RFID tags and tag communication devices is also in progress.
JP 2002-151944 (May 24, 2002) Japanese Patent Laid-Open No. 9-5431 (published on January 10, 1997) JP 2002-198722 A (published July 12, 2002)

  As described above, in the case of the microwave method, the communication distance between the tag communication device and the RFID tag can be easily extended from about several centimeters to several meters in comparison with the electromagnetic induction method. It is easy to expand the communication area, which is an area that can communicate with the RFID tag. However, when the communication area is expanded, the following problems occur.

  As a tag communication antenna that is an antenna of a tag communication apparatus, there are a case where a non-directional antenna or a weakly directional antenna is used, and a case where a highly directional antenna is used. For example, Patent Document 1 discloses an RFID system that uses a highly directional Yagi antenna. However, an antenna with strong directivity has a narrow communication area compared to an antenna with low directivity, and it is difficult to construct a system that can simultaneously read and write a large number of RFID tags with a small number of antennas.

  On the other hand, as an antenna configuration of a system for simultaneously reading and writing a large number of RFID tags, an antenna configuration as shown in FIGS. 13 and 14 is generally considered. FIG. 13 shows a communication area when an antenna with weak directivity is used, and FIG. 14 shows a communication area when an antenna with strong directivity is used.

  When using antennas with low directivity, it is possible to cover a wide communication area 101 with a small number of antennas 100 as shown in FIG. However, when the wide communication area 101 is covered with a small number of antennas 100, a large number of RFID tags 102 exist in the communication area 101 at the same time. For this reason, many communication collisions (collisions) occur between a small number of antennas 100 and a large number of RFID tags 102, and the quality of communication deteriorates.

  In addition, when using an antenna with weak directivity, communication in which the tag communication device cannot communicate with the RFID tag due to so-called multipath interference in which the direct wave from the tag communication device interferes with the reflected wave reflected on the floor or wall surface. An impossible part will occur in the communication area. In this case, an RFID tag that cannot communicate within the communication area may occur, which is not desirable. Further, the multipath interference increases the possibility that a communicable portion where the tag communication device can communicate with the RFID tag is generated outside the communication area. This is not desirable when it is desired to limit the communication area to a predetermined area.

  On the other hand, it is conceivable to adjust the position, direction, output, etc. of the antenna so as not to cause a communication impossible portion. However, since this adjustment needs to be performed while confirming that communication is possible in each part in the communication area, much time and labor are required.

  On the other hand, when using a highly directional antenna 110 as shown in FIG. 14, compared to using a weakly directional antenna 100 as shown in FIG. 13, the communication area 111 covered by one antenna. Therefore, the occurrence of the above-mentioned communication collision can be suppressed, and the deterioration of the communication quality can be suppressed. In addition, when the antenna 110 having high directivity is used, the problem caused by the multipath interference can be avoided by suppressing the intensity of the radio wave propagating to the floor surface or the wall surface.

  However, in order to cover a wide communication area with the highly directional antenna 110, a large number of antennas are required as shown in FIG. Furthermore, the antenna 110 having a high directivity has a larger antenna scale than the antenna 100 having a low directivity. Therefore, the scale of the antenna portion of the tag communication device is significantly increased.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a tag communication device that can cover a wide communication area without a communication impossible portion with a small number of highly directional antennas. is there.

  In order to solve the above problems, the inventor of the present application considered using a beam scan antenna as an antenna for tag communication of an RFID system. The beam scan antenna is a highly directional antenna that narrows down a radio wave beam and can scan the beam. As described in Patent Documents 2 and 3, the beam scan antenna is generally used for radar, but is not yet used as a tag communication antenna for an RFID system. Therefore, the inventors of the present application have devised the following means for solving the problems by variously changing the beam shape, traveling direction, scanning direction, and the like using the beam scanning antenna.

  That is, a tag communication device according to the present invention is a tag communication device that performs radio communication with an RFID tag via radio waves, and controls a tag communication antenna capable of scanning a beam of radio waves to be transmitted and the scan. The tag communication antenna transmits the beam to a part of the space where the RFID tag can exist, and the scan is performed by the scan control unit, so that the space is placed in the space. A direct wave of a beam directly transmitted from the tag communication antenna to the RFID tag and a reflection surface in which the beam is disposed in the space so as to be communicable with the existing RFID tag. Transmitting a beam that has a different radio wave intensity from the reflected wave that is reflected by and transmitted to the RFID tag

  A tag communication method for a tag communication device according to the present invention is a tag communication device that performs radio communication with an RFID tag via radio waves, the tag communication antenna capable of scanning a beam of radio waves to be transmitted; Scanning control means for controlling scanning, and the tag communication antenna transmits the beam to a part of a space where the RFID tag may exist, and the scanning is performed by the scanning control means. A tag communication method of a tag communication device arranged so as to be communicable with the RFID tag existing in the space, wherein the beam is transmitted directly from the tag communication antenna to the RFID tag in the space The radio wave intensity of the direct wave and the reflected wave of the beam reflected by a certain reflecting surface and transmitted to the RFID tag are different. By sending a beam is characterized by carrying out the RFID tag and wireless communication.

  According to the above configuration, the beam scanning antenna capable of scanning the radio wave beam to be transmitted is used as the tag communication antenna, and the radio wave beam transmitted from the tag communication antenna is scanned under the control of the scan control means. As a result, the communication area can be expanded as compared with a normal antenna having high directivity. Therefore, a wide communication area can be covered with a small number of antennas.

  By the way, the incommunicable part due to multipath interference occurs when the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave are approximately the same. Therefore, in the present invention, a radio wave of a direct wave of a beam directly transmitted from the tag communication antenna to the RFID tag and a reflected wave transmitted to the RFID tag after the beam is reflected by a reflection surface. Transmitting beams with different intensities.

  In this case, if the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave from the reflecting surface are different in the incommunicable portion, multipath interference is suppressed and communication between the tag communication device and the RFID tag is performed. Is possible. Therefore, the tag communication apparatus according to the present invention can cover a wide communication area having no communication disabled portion.

  Moreover, the tag communication apparatus according to the present invention is characterized in that, in the above configuration, the tag communication antenna is disposed apart from the reflection surface where the portion where communication is impossible due to the reflected wave is generated.

  According to the above configuration, it is possible to secure a space in which the incommunicable portion is suppressed between the tag communication antenna and the reflection surface, and it is possible to reliably communicate with a large number of RFID tags passing through the space.

  Note that the tag communication antenna preferably scans the beam by changing the phase of a signal transmitted from the phase shifter to the plurality of antenna elements. In this case, since a mechanical configuration for scanning the beam is not necessary, reliability can be improved.

  The radio wave to be transmitted is preferably a microwave. The microwave is a radio wave having a frequency of about 300 MHz to about 300 GHz. By using the microwave, it becomes easy to extend the communication distance between the tag communication device and the RFID tag to several meters or more.

  It is desirable to provide a plurality of tag communication antennas. In this case, since the scan range of each tag communication antenna can be narrowed, the scan time can be shortened.

  Furthermore, it is desirable that at least two of the tag communication antennas are arranged apart from each other in a direction substantially perpendicular to a reflection surface where a portion where communication is impossible due to the reflected wave occurs. In this case, since the angle formed by the beam traveling direction and the reflecting surface can be reduced, the influence of the reflected wave is reduced, and multipath interference can be reliably suppressed.

  By the way, since the beam scan is to change the traveling direction of the beam by fixing the position of the antenna, the communication area that can be communicated with the RFID tag by the scan is narrower and farther from the tag communication antenna. Become wider. For this reason, there is a possibility that an incommunicable area may occur due to the beam not reaching the area close to the tag communication antenna.

  Therefore, it is desirable that at least two tag communication antennas are arranged to face each other. In this case, since the area close to one tag communication antenna is the communication area of the opposing tag communication antenna, it is possible to prevent the occurrence of the incommunicable area. Furthermore, if the tag communication antennas facing each other are arranged so as to be shifted in a direction substantially perpendicular to the reflecting surface, the areas where the communication areas overlap each other are reduced, and radio waves from a plurality of tag communication antennas may interfere. Can be prevented.

  Further, the tag communication device according to the present invention is configured such that, in the above-described configuration, the number of the RFID tags in which the communication means performs wireless communication with the RFID tag via the tag communication antenna, and the communication means completes the wireless communication. Counting means, and the tag communication antenna instructs the scan control means to scan a certain scanning range at a certain step angle at a certain scanning time, and the counting means counts during the scanning. Obtain the number of completed RFID tag communications, repeat this for various scan times, scan ranges, and step angles, then determine the scan time, scan range, and step angle that maximizes the number of RFID tag communications completed By doing so, it further comprises a scan adjusting means for adjusting the scan of the beam.

  According to the above configuration, the scan adjustment unit automatically adjusts the scan time, the scan range, and the step angle so that the number of completed RFID tag communication is maximized. It becomes easy to tune the antenna so that the area becomes the communication area.

  The tag communication system according to the present invention includes a tag communication device configured as described above and a reflection for reducing the radio wave intensity of the reflected wave of the radio wave provided on a reflection surface of the radio wave transmitted by the tag communication antenna of the tag communication device. It is characterized by comprising a strength reducing body.

  Here, examples of the reflection intensity reducing body include a radio wave absorber that is an object that absorbs radio waves well, and a diffuse reflector that is an object that diffuses and reflects radio waves.

  According to the above configuration, among the reflective surfaces that reflect the radio waves transmitted by the tag communication antenna of the tag communication device, the reflection intensity reduction is reduced on the surface provided with the reflection intensity reducing body, so that the reflected radio wave intensity is reduced. The surface where the body is not provided can be identified as a reflective surface where the strongest reflected wave is generated, that is, a reflective surface where a portion where communication is impossible due to the reflected wave is generated. Therefore, the same effect as described above can be obtained by changing the beam direction of the radio wave to a direction perpendicular to the reflecting surface where the strongest reflected wave is generated.

  In addition, each means in the said tag communication apparatus can be performed on a computer by a program. Furthermore, the program can be executed on an arbitrary computer by storing the program in a computer-readable recording medium.

  As described above, the tag communication device according to the present invention uses a beam scan antenna capable of scanning a beam of radio waves to be transmitted as a tag communication antenna, and is controlled by the scan control means from the tag communication antenna. By scanning a beam of radio waves to be transmitted, the communication area can be expanded as compared with a normal antenna having high directivity, and a wide communication area can be covered with a small number of antennas. Further, the radio wave intensity of the direct wave of the beam directly transmitted from the tag communication antenna to the RFID tag and the reflected wave of the beam reflected by a reflection surface and transmitted to the RFID tag are different. Since a simple beam is transmitted, multipath interference can be suppressed, and the tag communication device and the RFID tag can communicate with each other, thereby providing an effect of covering a wide communication area having no communication disabled portion.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an overview of an RFID system (tag communication system) according to the present embodiment. The RFID system 1 automatically identifies non-contact items such as air baggage at an airport, luggage in logistics, and a work (intermediate product) in a manufacturing process. Specifically, the RFID system 1 uses an RFID reader / writer (hereinafter simply referred to as a “reader”) with respect to the RFID tags 3 attached to a large number of articles 4 that are transported by a transport means 5 such as an automatic transport vehicle or a belt conveyor. 2) performs wireless communication to read / write data.

  In the present embodiment, the frequency band of the radio wave transmitted by the reader / writer (tag communication device) 2 is a so-called UHF band around 800 MHz to 960 MHz. Thereby, the area where the reader / writer 2 can communicate with the RFID tag 3 is about several meters from the antenna of the reader / writer 2. In general, the microwave method using radio waves in the UHF band and 2.45 GHz band expands the communication distance compared to electromagnetic induction methods using electromagnetic induction in the 125 k to 135 kHz band and 13.56 MHz band. There is an advantage that it is easy. In addition, the UHF band radio wave has an advantage that it easily sneaks into the shadow as compared to the 2.4 GHz band radio wave.

  The RFID tag 3 includes a wireless communication IC (Integrated Circuit) and an antenna. The general RFID tag 3 does not have a power source such as a battery, and a circuit is operated by electric power transmitted from the reader / writer 2 by radio waves to perform wireless communication with the reader / writer 2.

  In this case, since the reader / writer 2 needs to transmit the power that can operate the RFID tag 3 several meters away by radio waves, the radio wave transmission output is as large as several W (watts). For this reason, in the RFID system 1 that transmits radio waves, it is necessary to take an EMI (Electro-Magnetic Interference) countermeasure that reduces leakage of radio waves transmitted from the reader / writer 2 from a predetermined area. Further, since the transmission output of the radio wave is large, the intensity of the reflected wave reflected from the floor 7, the side wall 8, the ceiling 9, etc. by the radio wave transmitted from the reader / writer 2 is also large, and due to multipath interference between the direct wave and the reflected wave Occurrence of incommunicable parts becomes a problem.

  In order to avoid these problems, in the RFID system 1 according to the present embodiment, the side wall 8 and the ceiling 9 to which the radio wave transmitted from the reader / writer 2 arrives have a radio wave absorber that absorbs the radio wave and the radio wave. A reflection intensity reducing body 6 that reduces the intensity of the reflected wave is provided, such as a diffuse reflector that diffusely reflects light. Thereby, it is possible to reduce the leakage of radio waves from a predetermined region, and it is possible to reduce the intensity of reflected waves.

  As the material of the radio wave absorber, known materials used for EMI countermeasures can be used. For example, a resistance film, a composite material of rubber and carbon, a fiber to which carbon is attached, a polystyrene foam, a carbon-containing urethane foam, Examples include ferrite and carbon / ferrite composites. In addition, examples of the diffuse reflector include those having irregularities that are the same as or higher than the wavelength of radio waves, and those having various dielectric constants.

  As described above, since the radio wave absorber and the radio wave scatterer are soft or uneven, it is not desirable to provide the radio wave absorber or the radio wave scatterer on the floor surface 7 on which a human moves or loads are transported. For this reason, the influence of the reflected wave from the floor surface 7 cannot be ignored, and multipath interference due to the direct wave and the reflected wave from the floor surface 7 becomes a problem.

  In contrast, the reader / writer 2 of the present embodiment uses a beam scan antenna that can scan a beam of radio waves to be transmitted. Thereby, the traveling direction P of the beam can be changed, so that the communication area can be expanded as compared with a normal antenna having high directivity. Therefore, a wide communication area can be covered with a small number of antennas.

  By the way, since the beam scanning direction Sc changes corresponding to the beam traveling direction P, the beam scanning is specified by the plane including the scanning direction Sc. For example, in the case of FIG. 1, the plane including the beam scanning direction Sc is a plane parallel to the drawing. In the reader / writer 2 of the present embodiment, the beam is scanned so that the surface including the beam scanning direction intersects the floor surface 7 which is the reflecting surface where the strongest reflected wave is generated.

  In this case, the traveling direction P of the beam changes toward the floor surface 7 by scanning. As a result, the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave from the floor surface 7 change at an arbitrary position in the communication area.

  FIG. 2 shows a direct wave DW transmitted directly from the antenna of the reader / writer 2 to a certain RFID tag 3 and a reflected wave RW reflected by the floor surface 7 and transmitted. FIGS. 9A and 9B show a case where the beam scan antenna 40 of the present embodiment is used, and shows a case where the traveling direction P of the beam differs depending on the scan. FIG. 2C shows a case where the antenna 100 having a low directivity according to the prior art is used.

  In the figure, when the radio wave intensity of the direct wave DW received by the RFID tag 3 and the radio wave intensity of the reflected wave RW are approximately the same, the direct wave DW and the reflected wave RW are indicated by solid lines, but are different. The solid line indicates the stronger radio wave intensity, and the broken line indicates the weaker one. Further, the shape of the beam is indicated by a one-dot chain line.

  Referring to FIG. 2, in the conventional case, as shown in FIG. 2C, the radio wave intensity of the direct wave DW received by the RFID tag 3 and the radio wave intensity of the reflected wave RW are approximately the same. For this reason, when the RFID tag 3 at the illustrated position has the direct wave DW and the reflected wave RW weakening each other due to multipath interference, the RFID tag 3 receives a significantly lower radio wave intensity, and the reader / writer Communication with 2 is disabled.

  On the other hand, as shown in FIG. 2A, when the RFID tag 3 is present in the beam traveling direction P by the beam scanning, the radio wave intensity of the direct wave DW is larger than the radio wave intensity of the reflected wave RW. . For this reason, even when the RFID tag 3 at the position shown in the figure has the direct wave DW and the reflected wave RW weakening each other due to multipath interference, the radio wave intensity of the received direct wave DW is not so low. Communication with the reader / writer 2 becomes possible.

  Further, as shown in FIG. 2B, the beam traveling direction P becomes lower than that in FIG. 2A due to the beam scanning, and the beam traveling direction P is symmetrical with respect to the floor surface 7 of the RFID tag 3. When there is a position, the radio wave intensity of the reflected wave RW is greater than the radio wave intensity of the direct wave DW. For this reason, even if the direct wave DW and the reflected wave RW weaken each other due to the multipath interference, the RFID tag 3 at the illustrated position does not have a very low radio wave intensity of the received reflected wave RW. Communication with the reader / writer 2 becomes possible.

  As described above, when the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave from the floor surface 7 are different in the part where communication is not possible due to multipath interference, the multipath interference is suppressed, and the reader / writer 2 and the RFID Communication with the tag 3 becomes possible. Therefore, it is possible to cover a wide communication area with no communication disabled portion. In the present embodiment, only the antenna of the reader / writer 2 and its control need be changed, and there is no need to make a special change to the RFID tag 3.

  Hereinafter, specific configurations of the reader / writer 2 and the RFID tag 3 will be described with reference to FIGS.

  FIG. 3 shows a schematic configuration of the reader / writer 2. As illustrated, the reader / writer 2 includes a control unit 20, a storage unit 21, a wireless processing unit (communication means) 22, an antenna unit (tag communication antenna) 23, a timer unit 24, and an external I / F (interface). It is the structure provided with the part 25. FIG.

  The control unit 20 controls the operations of the various components described above in the reader / writer 2 in an integrated manner. The control unit 20 is configured by, for example, a PC (Personal Computer) -based computer. And operation control of various composition is performed by making a computer run a control program. This program may be in the form of reading and using what is recorded on a removable medium such as a CD-ROM, or may be in the form of reading and using what is installed on a hard disk or the like. In addition, a mode in which the program is downloaded via the external I / F unit 25, installed on a hard disk, and the like is also conceivable.

  The storage unit 21 is configured by a nonvolatile storage device such as the hard disk described above. The contents stored in the storage unit 21 include the above-described control program, OS (operating system) program, various other programs, and various data. In the present embodiment, the storage unit 21 stores data of an antenna scan range, a step angle, and a holding time in the antenna unit 22.

  The radio processing unit 22 converts the data received from the control unit 20 into a format suitable for radio transmission, transmits the converted radio signal to the outside via the antenna unit 23, and receives the converted radio signal from the outside via the antenna unit 23. The converted radio signal is converted into the original format, and the converted data is transmitted to the control unit 20. As the wireless processing unit 22, an A / D (Analog to Digital) conversion circuit, a D / A (Digital to Analog) conversion circuit, a modulation / demodulation circuit, an RF circuit, or the like is used.

  The antenna unit 23 converts the radio signal from the radio processing unit 22 into a radio wave and transmits it to the outside, and converts the radio wave received from the outside into a radio signal and transmits it to the radio processing unit 22. An antenna, a resonance circuit, or the like is used for the antenna unit 23. In the present embodiment, the antenna unit 23 is a beam scan antenna that can scan the beam direction of a radio wave transmitted to the outside. Details of the beam scan antenna will be described later.

  The timer unit 24 measures various times based on an instruction from the control unit 20 and transmits the measured time data to the control unit 20. In the present embodiment, the timer unit 24 is used to adjust the beam direction of the radio wave transmitted from the antenna unit 23.

  The external I / F unit 25 communicates with an external device such as a PC. Examples of the interface standard of the external I / F unit 25 include USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), and the like.

  FIG. 4 shows a schematic configuration of the RFID tag 3. As illustrated, the RFID tag 3 includes an antenna unit 30 and a wireless communication IC 31.

  The antenna unit 30 receives radio waves from the reader / writer 2 as a power source for operating the wireless communication IC 31. The antenna unit 30 converts the radio wave received from the reader / writer 2 into a radio signal and transmits it to the radio communication IC 31, and converts the radio signal from the radio communication IC 31 into radio wave and transmits it to the reader / writer 2. Is. As the antenna unit 30, an antenna, a resonance circuit, or the like is used.

  The wireless communication IC 31 stores data from the reader / writer 2 based on a signal received from the reader / writer 2 via the antenna unit 30, or stores the stored data via the antenna unit 30. Or send to. As shown in FIG. 4, the wireless communication IC 31 includes a power supply unit 32, a wireless processing unit 33, a control unit 34, and a memory unit 35.

  The power supply unit 32 rectifies the induced voltage generated when the antenna unit 30 receives radio waves with a rectifier circuit, adjusts the induced voltage to a predetermined voltage with the power supply circuit, and then supplies the rectified voltage to each unit of the wireless communication IC 31. . For the power supply unit 32, a bridge diode, a voltage adjusting capacitor, or the like is used.

  The radio processing unit 33 converts the radio signal received from the outside via the antenna unit 30 into the original format, transmits the converted data to the control unit 34, and the data received from the control unit 34 is suitable for radio transmission. The converted wireless signal is transmitted to the outside through the antenna unit 30. As the wireless processing unit 33, an A / D (Analog to Digital) conversion circuit, a D / A (Digital to Analog) conversion circuit, a modulation / demodulation circuit, an RF circuit, or the like is used.

  The control unit 34 comprehensively controls the operations of the various configurations described above in the wireless communication IC 31. The control unit 34 includes a logic operation circuit, a register, and the like, and functions as a computer. And operation control of various composition is performed by making a computer run a control program. For example, this program may be used by reading and installing a program installed in a ROM (Read Only Memory) or the like of the memory unit 35, or from the reader / writer 2 via the antenna unit 30 and the wireless processing unit 33. The program may be downloaded, installed in the memory unit 35, and executed.

  In particular, the control unit 34 stores data from the reader / writer 2 in the memory unit 35 based on data received from the reader / writer 2 via the antenna unit 30 and the wireless processing unit 33, or stores data in the memory unit 35. The stored data is read out and transmitted to the reader / writer 2 via the wireless processing unit 33 and the antenna unit 30.

  The memory unit 35 is configured by a semiconductor memory such as the above-described ROM, SRAM (Static RAM), or FeRAM (ferroelectric memory). The contents stored in the memory unit 35 include the above-described control program, various other programs, and various data. Note that the wireless communication IC 31 uses a radio wave transmitted from the reader / writer 2 as a power source. Therefore, it is desirable to use a non-volatile memory such as a ROM or a memory with low power consumption such as an SRAM or FeRAM.

  Next, a beam scan antenna used for the antenna unit 23 of the reader / writer 2 will be described with reference to FIGS. As a beam scan antenna capable of scanning the beam direction of a radio wave transmitted to the outside, for example, as described in Patent Document 3, a method of swinging the antenna itself or a method of switching and using a plurality of antennas having different beam directions And a method using a phase shifter.

  Among these, the method of swinging the antenna itself requires mechanical drive means, which increases the scale of the apparatus and requires regular maintenance. Further, in the method of switching and using a plurality of antennas, mechanical driving means are not required, but since all antennas are not used at the same time, the antenna utilization efficiency is low. In contrast to these methods, a method using a phase shifter is superior in that a mechanical driving means is not required and that all antennas are used simultaneously, so that the antenna utilization efficiency is high.

  Therefore, in the present embodiment, a patch antenna using a phase shifter is used as a beam scan antenna. Note that the patch antenna is a kind of planar antenna, and includes a plurality of patch-like conductors that function as antenna elements and a dielectric.

  FIG. 5 shows an outline of a beam scan antenna using a phase shifter. The beam scan antenna 40 has a configuration in which a plurality of antenna elements 41 are arranged and a variable phase shifter (phase shifter) 42 is connected to each antenna element 41.

  When all the antenna elements 41 transmit radio waves with the same phase, the radio waves propagate as plane waves in a direction perpendicular to the arrangement direction of the antenna elements 41. On the other hand, in order to incline the propagation direction of the radio wave by an angle θ (rad) from the direction perpendicular to the arrangement direction of the antenna elements 41, the phase of the radio wave transmitted by each antenna element 41 may be shifted as follows.

That is, as shown in FIG. 5, the wavelength of the radio wave to be transmitted or received is λ (m), the distance between the reference antenna element 41a and the kth antenna element 41 is dk (m), and FIG. Of the equiphase surfaces indicated by broken lines, if the distance between the equiphase surface passing through the reference antenna element 41a and the kth antenna element 41 is lk (m), k relative to the phase of the reference antenna element 41a. The phase shift φk of the second antenna element 41 is as follows.
φk = (lk / λ) × 2π = (dk × sin θ / λ) × 2π (1).

  In this way, the beam scan antenna using the phase shifter can direct the radio wave beam in the target direction by shifting the phase of the signal so that each variable phase shifter 42 satisfies the above equation. On the other hand, when receiving radio waves, the direction of the received radio waves can be determined by detecting the phase shift of each antenna element 41.

  FIG. 6 shows a beam shape 45 of a radio wave transmitted by the beam scan antenna 40 of the present embodiment. 2A is a plan view, FIG. 2B is a front view, and FIG. 2C is a side view as viewed from the side facing the beam scan antenna 40. FIG. FIGS. 5B and 5C also show how the beam shape 45 changes by scanning.

  As shown in FIGS. 6A to 6C, the beam shape 45 transmitted from the beam scan antenna 40 of this embodiment is narrow in the scan direction Sc and wide in other directions. That is, the beam is a beam having high directivity in the scan direction Sc and weak directivity in the other directions. Since the beam shape 45 is wide in directions other than the scan direction Sc, a wide communication area as large as a beam having weak directivity as shown in FIG. 13 can be secured in one scan.

  FIG. 7 shows the distribution of the communication area in which the reader / writer 2 can communicate with the RFID tag 3 and the incommunicable area in which communication is impossible in the area of 2.5 m in width and 2.5 m in height. Show. In the figure, radio waves are transmitted in the right direction from a point at a height (H) of 1.25 m at the left end (x = −1.25 m). Also, the white area is a communication area, the black area is an incommunicable area, and the gray area is an unstable communication area.

  FIGS. 7A to 7C correspond to FIG. 6B and show the distribution of the communication area when the beam scan antenna 40 of the present embodiment is used, and FIG. ) Shows, as a comparative example, the distribution of communication areas when the conventional antenna 100 with low directivity is used. Furthermore, (a) to (c) in the figure show the distribution of communication areas when radio waves are transmitted obliquely upward, horizontally, and obliquely downward, respectively.

  As shown in FIG. 7D, when a radio wave is transmitted from an antenna with low directivity, a wide communication area is obtained, but many incommunicable portions are generated particularly at a low position. On the other hand, as shown in FIGS. 4A to 4C, when transmitting radio waves from a highly directional antenna, the communication area is narrow, but the communication area is secured in the traveling direction of the radio wave beam. can do. Therefore, as in the present embodiment, by scanning a radio wave beam, the communication areas shown in FIGS. 5A to 5C can be overlapped, and the incommunicable area can be eliminated.

  When FIG. 7B is compared with FIGS. 7A and 7C, when a radio wave beam is transmitted in the horizontal direction, it may be a good communication area corresponding to the traveling direction of the radio wave beam. Understandable. This can suppress the influence of multipath interference by transmitting radio waves in a direction parallel to the floor surface 7 on which the reflected wave reducing body 6 is not provided, that is, the surface that is most likely to be affected by the reflected wave. This is thought to be possible. Therefore, it is desirable that the traveling direction of the radio wave beam includes a case in which the traveling direction of the radio wave beam is parallel to a surface that is most likely to be affected by the reflected wave.

  Moreover, as shown in FIG. 6B and FIGS. 7A to 7C, it is desirable that the antenna be arranged apart from the floor surface. Further, as shown in FIG. 7C, the distance between the antenna and the floor surface is such that, when the traveling direction of the transmitted radio wave beam is directed toward the floor surface, the beam traveling direction and the floor surface are It is desirable that the angle is determined based on the angle formed, the space necessary for reading the RFID tag 3, and the absence of an incommunicable portion in the necessary space. In this case, it is possible to secure a space in which the incommunicable portion is suppressed between the antenna and the floor surface, and it is possible to reliably communicate with a large number of RFID tags 3 passing through the space.

  Next, radio wave scan adjustment from the reader / writer 2 will be described with reference to FIGS. The reader / writer 2 of the present embodiment has a scan range indicating the range of the radio wave transmission direction (traveling direction), a step in the transmission direction, and a certain step so that it can communicate with almost all RFID tags 3 at a predetermined time. It has a function of adjusting and optimizing the holding time for holding transmission of radio waves in the transmission direction.

  FIG. 8 shows functional blocks for adjusting the radio wave transmission direction in the control unit 20 of the reader / writer 2. As illustrated, the control unit 20 includes a communication completion number counting unit (counting unit) 50, a scan range adjusting unit (scan adjusting unit) 51, a step angle adjusting unit (scan adjusting unit) 52, and a holding time adjusting unit (scan adjustment). Means) 53, and a scan direction instruction section (scan control means) 54. 9A to 9C show the adjustment of the radio wave transmission direction in the scan range adjustment unit 51, the step angle adjustment unit 52, and the holding time adjustment unit 53, respectively.

  The communication completion number counting unit 50 counts the number of RFID tags 3 that have completed communication by receiving information from the wireless processing unit 22 of the RFID tag 3 that has been successfully completed through wireless communication. The communication completion number counting unit 50 transmits the count information of the RFID tag 3 that has completed the communication to the scan range adjusting unit 51, the step angle adjusting unit 52, and the holding time adjusting unit 53.

  The scan direction instruction unit 54 controls the antenna unit 23 based on an instruction of the radio wave transmission direction θ received from the scan range adjustment unit 51, the step angle adjustment unit 52, and the holding time adjustment unit 53. Specifically, the scan direction instruction unit 54 calculates the phase φk of the radio wave transmitted from each antenna element 41 shown in FIG. 5 based on the above equation (1) based on the instruction of the radio wave transmission direction θ. The calculated phase φk is transmitted to each variable phase shifter 42 of the antenna unit 23.

  As shown in FIG. 9A, the scan range adjustment unit 51 adjusts the scan start angle a (rad) and the scan end angle b (rad) with respect to the radio wave transmission direction. The scan range adjustment unit 51 stores the adjusted start angle a and end angle b in the storage unit 21 and is used in actual operations. Note that an arbitrary direction such as a horizontal direction or a vertical direction can be selected as a direction serving as a reference for the angle.

  Specifically, the scan range adjustment unit 51 first performs one scan at a certain scan start angle a and end angle b, a predetermined step angle Δθ (rad), and a predetermined scan time T (s). The scan direction instruction unit 54 is instructed to do so. Thereafter, the number of RFID tags 3 that have completed communication within a predetermined scan time T is acquired from the communication completion number counting unit 50. Then, by repeating these operations while changing the scan start angle a and end angle b in various ways, the scan start angle a and end with the largest number of RFID tags 3 that have completed communication in one scan. Determine the angle b.

  As shown in FIG. 9B, the step angle adjusting unit 52 adjusts the step angle Δθ indicating the amount of change when the radio wave transmission direction is changed. Further, the step angle adjustment unit 52 stores the adjusted step angle Δθ in the storage unit 21 and is used in an actual operation.

  Specifically, the step angle adjustment unit 52 first performs one scan at the scan start angle a and end angle b determined by the scan range adjustment unit 51, a certain step angle Δθ, and a predetermined scan time T. The scan direction instruction unit 54 is instructed to do so. Thereafter, the number of RFID tags 3 that have completed communication within a predetermined scan time T is acquired from the communication completion number counting unit 50. These operations are repeated by changing the step angle Δθ in various ways, thereby determining the step angle Δθ with the largest number of RFID tags 3 that have completed communication in one scan.

  As shown in FIG. 9C, the holding time adjustment unit 53 adjusts a holding time t (s) for holding transmission of radio waves in a certain direction. The holding time adjustment unit 53 stores the adjusted holding time t in the storage unit 21 and is used in actual operation.

  Specifically, the holding time adjustment unit 53 first starts the scan start angle a and end angle b determined by the scan range adjustment unit 51, the step angle Δθ (rad) determined by the step angle adjustment unit 52, and certain The scan direction instruction unit 54 is instructed to perform scanning at the holding time t. Thereafter, the number of RFID tags 3 that have completed communication in one scan is acquired from the communication completion count unit 50. Then, by repeating these operations while changing the holding time t in various ways, the holding time t having the largest number of RFID tags 3 that have completed communication in one scan is determined.

  FIG. 10 shows a flow of processing for adjusting the transmission direction of the radio wave from the reader / writer 2 in the RFID system 1 having the above configuration. This adjustment is performed in an operating state in accordance with actual operation.

  First, a reference workpiece is set (step S10. Hereinafter, it may be simply referred to as “S10”. The same applies to other steps). Specifically, for example, when considering a case of automatically recognizing air baggage without contact, first, the RFID tag 3 is attached to a work 4 such as a suitcase or cardboard that actually flows on a belt conveyor that is a transport means 5. Install. On the other hand, the reader / writer 2 installs an antenna at an appropriate place, and the surrounding environment of the antenna is the same as that during operation. Next, the workpiece 4 having the RFID tag 3 is caused to flow on the conveyor 5 at an actual transport speed so that a predetermined number of the workpieces 4 pass through the communication area with the reader / writer 2 within a predetermined time T.

  Next, the scan range adjustment unit 51 performs the adjustment operation described above to optimize the scan ranges a and b (S11), and the step angle adjustment unit 52 performs the adjustment operation described above to perform the step angle Δθ. (S12), the holding time adjustment unit 53 performs the above-described adjustment operation to optimize the holding time t (S13).

  As described above, the optimum scanning operation condition is determined, and this condition is stored in the storage unit 21 as an initial condition and used for actual operation.

  Therefore, in this embodiment, the optimum scanning operation conditions are automatically determined, so that the antenna can be tuned so that the desired area becomes the communication area at the time of initial setting or maintenance of the antenna. It becomes easy. Further, it can be appropriately performed not only during initial setting and maintenance but also during actual operation.

  Note that the order of the adjustment operations of the scan ranges a to b, the step angle Δθ, and the holding time t can be variously changed. Further, instead of adjusting the holding time t, the predetermined time T may be adjusted.

  Next, the number and installation positions of the beam scan antennas 40 used in the reader / writer 2 will be described with reference to FIG. FIG. 11 shows a scan range of radio waves transmitted by the beam scan antenna 40 of the reader / writer 2. FIG. 4A shows a case where only one beam scan antenna 40 is provided, and FIG. 5B shows a case where two beam scan antennas 40 are provided in the vertical direction. FIG. 4C shows a case where two beam scan antennas 40 are provided facing each other and shifted in the vertical direction.

  When FIG. 11A is compared with FIGS. 11B and 11C, when one beam scan antenna 40 is provided, the scan range 60 is wide, so that the time required for one scan becomes longer. . In addition, since the downward inclination is large, the angle formed between the radio wave transmission direction and the floor surface 7 increases, and the reflected wave reflected by the floor surface 7 spreads backward (right side of the drawing), increasing multipath interference. There is a risk of doing.

  On the other hand, as shown in FIGS. 11B and 11C, when two beam scan antennas 40 are provided in the vertical direction, the scan range 60 is narrow, so the time required for one scan is obtained. Becomes shorter. In addition, since the downward inclination is small, the upper beam scan antenna 40 can prevent multipath interference because the transmission direction of radio waves does not intersect the floor surface. Furthermore, the lower beam scan antenna 40 has a small angle between the radio wave transmission direction and the floor surface, and the reflected wave reflected by the floor surface does not spread so far backward, so that multipath interference can be suppressed.

  Therefore, the reader / writer 2 desirably uses a plurality of beam scan antennas 40. Further, in order to suppress multipath interference due to a reflected wave from the floor surface, the reader / writer 2 is preferably provided with a plurality of beam scan antennas 40 in the vertical direction, that is, in a direction perpendicular to the floor surface.

  By the way, as can be understood from FIGS. 11A to 11C, the communication area in which the reader / writer 2 can communicate with the RFID tag 3 via the beam scan antenna 40 is narrower near the beam scan antenna 40. , The farther away becomes wider. For this reason, as shown in FIGS. 11A and 11B, there is a region where the beam does not reach even when scanning, in the region close to the beam scan antenna 40, and this region may become an incommunicable region. There is. Further, as shown in FIG. 11B, in a region far from the beam scan antenna 40, there is a region where communication regions of the beam scan antennas 40 overlap each other, and there is a possibility of interference in this region.

  Therefore, as shown in FIG. 11C, it is desirable to arrange a plurality of beam scan antennas 40 so as to face each other. In this case, since the area close to one beam scan antenna 40 is a communication area of the opposite beam scan antenna 40, it is possible to prevent the occurrence of the incommunicable area. Furthermore, if the beam scan antennas 40 facing each other are arranged so as to be shifted in a direction substantially perpendicular to the floor surface 7, as shown in FIG. It is possible to prevent radio waves from the beam scan antenna 40 from interfering.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

  For example, in the above embodiment, the reader / writer 2 reads / writes information from / to the RFID tag 3, but may have only a reader function for reading information from the RFID tag 3, It may have only a writer function for writing information. Further, the reader / writer 2 may receive a radio wave transmitted by the RFID tag 3 with a beam scan antenna or may be received with a separately provided antenna.

  Further, in the above embodiment, the traveling direction of the transmitted radio wave beam is changed to a direction perpendicular to the floor surface. However, when the reflective surface where the strongest reflected wave is generated is the side surface 8, the radio wave beam is transmitted. It is desirable to change the direction of travel to a direction perpendicular to the side surface 8. Thus, it is desirable that the plane including the traveling direction of the transmitted radio wave beam is substantially perpendicular to the reflecting surface.

  In the above embodiment, the surface including the scanning direction Sc is a surface perpendicular to the floor surface 7 as shown in FIG. 6, but intersects with a surface other than a surface parallel to the floor surface 7, that is, the floor surface 7. Any surface can be selected as long as it is a surface. For example, FIG. 12 corresponds to FIG. 6C, and shows a case where the surface including the scanning direction Sc is inclined 45 degrees from the floor surface 7. Even in this case, the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave from the floor surface 7 are changed, so that it is possible to suppress the occurrence of an incommunicable region due to multipath interference.

  Furthermore, as shown in FIGS. 2A and 2B, if the beam is narrowed in a direction perpendicular to the floor surface 7, it is possible to suppress the occurrence of an incommunicable region due to multipath interference. Therefore, the beam is narrowed in at least one direction regardless of the scanning direction Sc, and at least one of the directions in which the beam is narrowed may intersect with the reflecting surface where the strongest reflected wave is generated.

  Each block of the reader / writer 2 may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the reader / writer 2 is a storage device (such as a CPU that executes instructions of a control program that realizes each function, a ROM that stores the program, a RAM that expands the program, a memory that stores the program and various data, and the like. Recording medium). An object of the present invention is to provide a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program for the reader / writer 2 which is software for realizing the above-described functions is recorded so as to be readable by a computer. This can also be achieved by supplying the data to the reader / writer 2 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a disk system including a magnetic disk such as a flexible disk / hard disk and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R, and an IC card. A card system such as an optical card (including a memory card) or a semiconductor memory system such as a mask ROM / EPROM / EEPROM / flash ROM can be used.

  The reader / writer 2 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a carrier wave or a data signal sequence in which the program code is embodied by electronic transmission.

  The present invention may be configured as follows.

  That is, the tag communication antenna according to the present invention is a tag communication antenna used in a tag communication device that performs radio communication with an RFID tag via radio waves, and scans a beam of radio waves to be transmitted. In this configuration, the light is focused in at least one direction, and at least one of the directions in which the beam is focused intersects the reflective surface where the strongest reflected wave is generated.

  Here, when the beam is scanned, the direction in which the beam is focused changes, but the changed direction also intersects with the reflecting surface.

  According to said structure, a communication area can be expanded compared with the normal antenna with strong directivity by utilizing the beam scan antenna which can scan the beam of the radio wave to transmit. Therefore, a wide communication area can be covered with a small number of antennas.

  By the way, the incommunicable part due to multipath interference occurs when the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave are approximately the same. Therefore, the beam transmitted by the tag communication antenna according to the present invention is focused in at least one direction, and at least one direction in which the beam is focused intersects the reflecting surface. .

  In this case, since the beam is narrowed in the direction intersecting with the reflection surface, the beam is also narrowed in the direction perpendicular to the reflection surface. In this case, when the beam is scanned, and either one of the traveling direction of the direct wave and the traveling direction of the wave before the reflected wave is reflected matches the traveling direction of the beam, The radio wave intensity of the reflected wave from the reflecting surface changes. At this time, if the radio wave intensity of the direct wave differs from the radio wave intensity of the reflected wave from the reflecting surface at the incommunicable portion, multipath interference is suppressed and communication between the tag communication device and the RFID tag is performed. Is possible. Therefore, the antenna for tag communication according to the present invention can cover a wide communication area without a communication impossible portion.

  In addition, it is desirable that a direction intersecting with the reflection surface in a direction in which the beam is focused is a scan direction of the beam. In this case, since the scanning is performed in the direction in which the beam is focused, the predetermined area can be effectively scanned.

  Further, it is desirable that the surface including the scanning direction is substantially perpendicular to the reflecting surface. In this case, since the radio wave intensity of the direct wave and the radio wave intensity of the reflected wave from the reflecting surface are effectively changed, the incommunicable portion due to multipath interference is reliably suppressed, and the tag communication device and the RFID tag Can reliably communicate.

  Furthermore, it is desirable that the traveling direction of the beam includes a direction substantially parallel to the reflecting surface. When the beam travels in a direction substantially parallel to the reflecting surface, the intensity of the radio wave propagating to the reflecting surface is reduced and the intensity of the reflected wave is also reduced, so that the incommunicable portion due to multipath interference can be further reliably suppressed. be able to.

  Further, it is desirable that the beam is focused only in the scanning direction. In this case, the beam has a narrow shape in the scanning direction and a wide shape in the other directions, and this beam is scanned. Therefore, as shown in FIG. A communication area can be secured.

  When the tag communication antenna is arranged to be separated from the reflecting surface, the distance of the separation is the traveling direction of the beam when the traveling direction of the beam is directed to the reflecting surface. It is desirable that the distance is determined based on the angle formed by the reflection surface, the space necessary for reading the RFID tag, and the absence of a communication disabled portion in the necessary space.

  A tag communication apparatus according to the present invention is a tag communication apparatus that performs radio communication with an RFID tag, and controls a tag communication antenna having the above-described configuration and scanning of a beam of a radio wave transmitted from the tag communication antenna. And a scan control means.

  The tag communication device having the above-described configuration includes the tag communication antenna having the above-described configuration, and the beam of the radio wave transmitted from the tag communication antenna is scanned by the control of the scan control unit, so that the same effect as described above can be obtained. Can do.

  A beam adjustment method for a tag communication apparatus according to the present invention is a scan adjustment method for adjusting a scan of a radio wave beam transmitted by a tag communication antenna having the above-described configuration, and has a certain scan range at a certain scan time. A scan step for performing the scan at a step angle, a count step for counting the number of completed RFID tag communications during the scan, and the scan step and the count step with various scan times and scan ranges. And a repetition step that repeats with respect to the step angle, and a determination step that determines a scan time, a scan range, and a step angle so that the number of communication completions of the RFID tag is maximized by the repetition step. Yes.

  According to the above method, the scan time, the scan range, and the step angle are automatically adjusted so that the number of completed RFID tag communication is maximized, so that the desired area is set as the communication area at the time of antenna installation or maintenance. Thus, the antenna can be easily tuned.

  The scan adjustment means in the tag communication device can be executed on a computer by a scan adjustment program. Furthermore, by storing the scan adjustment program in a computer-readable recording medium, the scan adjustment program can be executed on any computer.

  The RFID system according to the present invention scans a beam so that a plane including the scan direction of a radio wave beam transmitted from an antenna of a reader / writer intersects a reflective surface where the strongest reflected wave is generated, thereby multipath interference. Therefore, any RFID system that transmits radio waves can be applied to radio waves of any frequency.

It is a front view which shows the outline | summary of the RFID system which is one Embodiment of this invention. FIG. 2 is a front view showing a direct wave and a reflected wave transmitted from an antenna of an RFID reader / writer to a certain RFID tag. FIGS. 5A and 5B show the direct beam traveling direction is the direct wave. The traveling direction of the wave and the traveling direction of the wave before reflection of the reflected wave are the same as those of the RFID system, and FIG. Shows the case. It is a block diagram which shows schematic structure of the RFID reader / writer in the said RFID system. It is a block diagram which shows schematic structure of the RFID tag in the said RFID system. It is a schematic diagram which shows the outline | summary of the beam scan antenna using the phase shifter provided in the said RFID reader / writer. The beam shape of the radio wave transmitted by the beam scan antenna is shown. FIG. 4A is a plan view, FIG. 4B is a front view, and FIG. 4C is opposed to the beam scan antenna. It is the side view seen from the side. It is a graph which shows distribution of the communication area | region of the said RFID reader / writer and the said RFID tag, The figure (a)-(c) transmitted the radio wave with strong directivity diagonally upward, a horizontal direction, and diagonally downward. Each case is shown, and FIG. 4D shows a case where a radio wave with weak directivity is transmitted as a comparative example. It is a block diagram which shows the function structure which performs the scanning adjustment of the beam of the radio wave to transmit in the control part of the said RFID reader / writer. FIGS. 9A to 9C are diagrams showing the contents of adjustment of the scan range, the step angle, and the holding time regarding the scan adjustment. It is a flowchart which shows the flow of the process of the said scan adjustment. It is a front view which shows the scanning range of the electromagnetic wave which the beam scan antenna of the said RFID reader / writer transmits, The figure (a) shows the case where only one beam scan antenna is provided, The figure (b) Shows a case where two beam scan antennas are provided in the vertical direction, and FIG. 8C shows a case where the two beam scan antennas are opposed to each other and shifted in the vertical direction. . It is the side view which looked at another beam shape of the electric wave which the said beam scan antenna transmits from the side facing a beam scan antenna, and has shown the case where the surface containing a scanning direction is inclined 45 degree | times from the floor surface. When an RFID reader / writer uses an antenna with weak directivity, it is a side view showing an area where it can communicate with an RFID tag. FIG. 3 is a side view showing an area where an RFID reader / writer can communicate with an RFID tag when using a highly directional antenna.

Explanation of symbols

1 RFID system (tag communication system)
2 RFID reader / writer (tag communication device)
3 RFID tag 6 Reflection intensity reduction body 22 Wireless processing part (communication means)
23 Antenna section (tag communication antenna)
40 Beam scan antenna (antenna for tag communication)
41 Antenna element 42 Variable phase shifter (phase shifter)
50 Communication completion count section (counting means)
51 Scan range adjustment section (scan adjustment means)
52 Step angle adjuster (scan adjustment means)
53 Holding time adjustment unit (scan adjustment means)
54 Scan direction indicating section (scan control means)

Claims (11)

A tag communication device that performs radio communication with an RFID tag via radio waves,
A tag communication antenna capable of scanning a beam of radio waves to be transmitted;
Scanning control means for controlling the scan,
The tag communication antenna is
The beam is transmitted to a part of the space where the RFID tag can exist, and the scan is performed by the scan control means, so that the RFID tag can communicate with the RFID tag existing in the space. ,And,
In the space, the radio wave intensity of the direct wave of the beam directly transmitted from the tag communication antenna to the RFID tag and the reflected wave of the beam reflected by a reflection surface and transmitted to the RFID tag is A tag communication device that transmits different beams.   The tag communication device according to claim 1, wherein the tag communication antenna is arranged apart from the reflection surface where a portion where communication is impossible due to the reflected wave is generated.   3. The tag communication device according to claim 1, wherein the beam is scanned by shifting a phase of a signal transmitted from the phase shifter to the plurality of antenna elements.   The tag communication device according to any one of claims 1 to 3, wherein the radio wave to be transmitted is a microwave.   The tag communication device according to any one of claims 1 to 4, wherein a plurality of the tag communication antennas are provided.   6. The tag communication device according to claim 5, wherein at least two of the tag communication antennas are arranged apart from each other in a direction substantially perpendicular to a reflection surface where a portion where communication is impossible due to the reflected wave occurs.   The tag communication device according to claim 5 or 6, wherein at least two antennas for tag communication are arranged to face each other. Communication means for performing wireless communication with the RFID tag via the tag communication antenna;
Counting means for counting the number of the RFID tags with which the communication means has completed wireless communication;
The RFID tag communication antenna instructs the scan control means to scan a certain scan range at a certain step angle at a certain scan time, and the RFID tag communication completion count counted by the count means during the scan And repeating this for various scan times, scan ranges, and step angles, and then determining the scan time, scan range, and step angle that maximizes the number of RFID tag communications completed. The tag communication device according to claim 1, further comprising: a scan adjustment unit that adjusts a scan. The tag communication device according to any one of claims 1 to 8,
A tag communication system comprising: a reflection intensity reducing body that is provided on a reflection surface of a radio wave transmitted by a tag communication antenna of the tag communication device and reduces a radio wave intensity of the reflected wave of the radio wave. A tag communication device that performs radio communication with an RFID tag via radio waves, comprising: a tag communication antenna capable of scanning a beam of radio waves to be transmitted; and a scan control means for controlling the scan. The communication antenna transmits the beam to a part of the space where the RFID tag can exist, and the scan control means performs the scan so that the communication antenna can communicate with the RFID tag existing in the space. A tag communication method for a tag communication device arranged in
In the space, the radio wave intensity of the direct wave of the beam directly transmitted from the tag communication antenna to the RFID tag and the reflected wave of the beam reflected by a reflection surface and transmitted to the RFID tag is A tag communication method for a tag communication apparatus, wherein wireless communication is performed with the RFID tag by transmitting different beams.   A program for operating the tag communication device according to any one of claims 1 to 8, wherein the program causes a computer to function as each of the means.

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