RF tag system

Abstract

To provide an RF tag system which enables use of general-purpose inlays and reader-writers without requiring a complex configuration, structure, and the like, and ensures reliable communication only with a target RF tag from among a plurality of necessary tags without errors.SOLUTION: An RF tag system 1 comprises a transceiving antenna 11, RF tags 20, and a relay device 30. The relay device 30 comprises conductors 31 and a support 32 for supporting the conductors 31 and is installed at the middle between the transceiving antenna 11 and the RF tags 20. The conductors 31 are configured to re-emit a radio wave received from the transceiving antenna 11 or the RF tags 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an RF tag system for performing product management and logistics management by reading RF tags attached to articles and objects to be managed, such as products flowing on a logistics line or conveyed objects carried by a forklift.

Background Art

[0002] Generally, a so-called RF tag incorporating an IC chip capable of reading and writing predetermined information regarding an article or object is widely used for any article or object. The RF tag is also called an RFID (Radio Frequency Identification) tag, an IC tag, a non-contact tag, etc., and is a so-called inlay in which an electronic circuit including an IC chip and a wireless antenna is sealed and coated with a base material such as a resin film, formed in the shape of a tag (luggage), and is a ultra-small communication terminal. Predetermined information can be wirelessly read and written to the IC chip in the tag by a reading / writing device (reader / writer), and reading and writing (read-only, write-once, read / write) can be performed.

[0003] By writing predetermined information into such an RF tag and attaching it to an arbitrary article, object, etc., the information recorded in the RF tag can be picked up by a reader / writer, and the information recorded in the tag can be recognized, output, displayed, updated, etc. as predetermined information regarding the article. Such an RF tag can record data of several hundred bits to several kilobits in the memory of the IC chip, can record a sufficient amount of information as information regarding articles, etc., and can communicate with the reader / writer side in a non-contact manner, so there is no need to worry about wear, scratches, dirt, etc. of the contacts. Furthermore, since the tag itself can be made power-free, processing according to the object, miniaturization, and thinning are possible.

[0004] By using such RF tags, various information about the item to which the tag is attached can be recorded, such as the item's name, identification code, contents, ingredients, manager, user, usage status, and usage conditions. This allows for accurate reading and writing of a wide variety of information that would be impossible with text or barcodes printed on a label surface, simply by attaching the miniaturized and thin tag to the item. For this reason, RF tags are widely used, for example, in the industrial sector as a means of logistics management and product management for handling large quantities of products.

[0005] In order to read RF tags attached to multiple objects in a logistics system, a system is needed—an RF tag system—that can correctly identify and read each individual RF tag on each object, especially products flowing along a logistics line or goods being transported by forklifts. For example, in industries that handle products for customers, there can be no errors in product management, and RF tag systems are required to communicate with RF tags attached to objects with 100% certainty.

[0006] A common method for achieving such goals is to adjust the output of the RF tag reader / writer so that it can communicate with the RF tag attached to the object with sufficient margin. On the other hand, in actual logistics situations, there are surrounding items with RF tags attached in addition to the target object, and there is a problem of misreading where RF tags attached to surrounding items communicate with the target object.

[0007] Furthermore, depending on the condition of the item to which the RF tag is attached, and individual differences in the RF tags themselves, the sensitivity of RF tags located at a distance (nearby items) may be relatively increased, potentially leading to misreading. Common countermeasures against misreading of such RF tags include installing radio wave absorbing sheets or anechoic boxes (gates), and setting up restricted areas for surrounding items (with unwanted RF tags attached). However, new problems have arisen, such as the high cost of radio wave absorbing sheets and the reduced convenience caused by restricted areas.

[0008] Here, as for technologies related to RF tag systems that can correctly read and communicate with RF tags as described above, there are, for example, those proposed in Patent Documents 1-3. Patent Document 1 proposes an "RFID tag booster antenna" that aims to extend the communication range of an RF tag by installing the RF tag and the booster antenna at a distance from each other and installing the booster antenna on a separate plane, thereby improving the performance of the tag while avoiding dimensional problems.

[0009] Furthermore, Patent Document 2 proposes an "RFID system" aimed at enabling communication only with necessary RF tags. This system involves setting up an antenna and RF tags (fixed tags) opposite each other on either side of the path the target moving object is traveling. When the target moving object is not present, the fixed tags are read, and when the target moving object is present, the signal from the fixed tags is buried, allowing the system to read the moving object.

[0010] Furthermore, Patent Document 3 proposes a "communication improvement device, communication system, and goods information handling equipment" that aims to improve the communication environment by having a permeable through-hole in a part of the radio wave absorber, which acts as a slot antenna to control the directivity of the antenna. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2010-263404 [Patent Document 2] Japanese Patent Publication No. 2012-098863 [Patent Document 3] Japanese Patent Publication No. 2008-099266 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, the technologies proposed in Patent Documents 1-3 require a dedicated RF tag structure equipped with a booster antenna, a complex reader / writer device configuration, and the installation of expensive radio wave absorbers. This results in a complex and large RF tag system and RF tag itself, making miniaturization and cost reduction difficult. Furthermore, in dedicated systems that require complex configurations and structures different from those of standard RF tags (inlays) and reader / writers, general-purpose inlays and reader / writers cannot be used as is. Dedicated tags and antenna structures must be prepared, which poses problems in terms of tag versatility and expandability.

[0013] Furthermore, such complex, specialized tag structures not only increase production costs but also make the tags themselves larger and heavier, undermining the greatest advantages of RF tags: their small size, thin profile, light weight, and ease of handling. RF tags can leverage the advantages of being a low-cost, compact, lightweight, and high-capacity wireless communication method by utilizing inexpensive, mass-produced general-purpose tags (inlays). However, a dedicated tag (inlay) structure requiring a complex configuration may reduce the advantages and characteristics of RF tags.

[0014] On the other hand, reliably reading RF tags attached to multiple objects and identifying them with 100% accuracy is an essential requirement, especially in industrial logistics systems. Therefore, there is a strong demand, particularly in industry, for the development of an RF tag system that can accurately and reliably identify multiple RF tags without compromising the versatility and miniaturization / lightweight nature of RF tags, while also avoiding system complexity. However, no RF tag system has been proposed that can reliably and cost-effectively communicate with RF tags on multiple objects while simultaneously achieving these two goals.

[0015] The present invention is proposed to solve the problems of the above-mentioned conventional technologies. Without requiring a complex configuration, structure, etc., it can directly use general-purpose inlays and readers / writers, and can surely and accurately communicate only with the target RF tag among a plurality of necessary RF tags. In particular, it aims to provide an RF tag system suitable for logistics management and product management that handle a large number of products, etc.

Means for Solving the Problems

[0016] To achieve the above object, the present invention is an RF tag system including a transceiver antenna, an RF tag, and a relay device. The relay device includes a conductor and a support for supporting the conductor, and is installed between the transceiver antenna and the RF tag. The conductor re-radiates the radio waves received from the transceiver antenna or the RF tag Furthermore, the interference effect of radio waves re-radiated by multiple conductors makes it possible to increase the radio wave intensity at a specific location. as a configuration.

Effects of the Invention

[0017] According to the present invention, without requiring a complex configuration, structure, etc., general-purpose inlays and readers / writers can be directly used, and it is possible to surely and accurately communicate only with the target RF tag among a plurality of necessary RF tags. As a result, it becomes possible to provide an RF tag system suitable for logistics management and product management that handle a large number of products, etc. S

Brief Description of the Drawings

[0018] [Figure 1] It is an explanatory diagram schematically showing the configuration of an RF tag system according to an embodiment of the present invention, where (a) is a conventional system and (b) is the system of the present invention. [Figure 2] It is an explanatory diagram showing the principle of polarization conversion in an RF tag system according to an embodiment of the present invention, where (a) is a case without a relay device and (b) is a case with a relay device. [Figure 3]It is an explanatory diagram for explaining the twist angle Φ and the received power in the RF tag system according to an embodiment of the present invention. (a) schematically shows the analysis environment, and (b) is a table for comparing the analysis results and the influence of the twist angle Φ. [Figure 4] It is an explanatory diagram for explaining the tilt θ1 or θ2 and the received power when the twist angle is Φ = 90° in the RF tag system according to an embodiment of the present invention. (a) schematically shows the analysis environment, and (b) is a table for comparing the analysis results and the influence of the tilt θ1 or θ2. [Figure 5] It is an explanatory diagram for explaining the re-radiation of radio waves in the relay device of the RF tag system according to an embodiment of the present invention. (a) shows the state before receiving radio waves by the relay device (conductor), (b) shows the state after receiving radio waves by the relay device (conductor), and (c) shows the state where the relay device (conductor) radiates (re-radiates) the received radio waves. [Figure 6] It is an explanatory diagram schematically showing the arrangement configuration of the RF tag system according to an embodiment of the present invention. (a) is a conventional system, and (b) is the system of the present invention. [Figure 7] It is an explanatory diagram for explaining the synthesis of radio waves in the RF tag system according to an embodiment of the present invention. (a) shows the synthesis of radio waves with the same phase, and (b) shows the synthesis of radio waves with the opposite phase. [Figure 8] It is an explanatory diagram for explaining the range of the half-value angle where the relay device of the RF tag system according to an embodiment of the present invention is arranged. [Figure 9] (a) to (d) are explanatory diagrams schematically showing the configuration of the relay device included in the RF tag system according to an embodiment of the present invention. [Figure 10] It is an explanatory diagram for explaining an example of the RF tag system of the present invention. (a) is a conventional system as a comparative example, and (b) shows the system of the present invention as an example. [Figure 11] It is an explanatory diagram for explaining the details of the installation positions of unnecessary tags in the example and comparative example shown in FIG. 10. [Figure 12]Figure 10 is an explanatory diagram illustrating the details of the installation location of the relay device in the embodiment shown. [Figure 13] Figure 10 is an explanatory diagram illustrating the details of the relay device in the embodiment shown. [Figure 14] Figure 10 is a line graph showing the relationship between frequency and electromotive force of RF tags, illustrating the communication characteristics of RF tags in the examples and comparative examples shown. [Figure 15] Figure 10 is an explanatory diagram illustrating the details of the results of the examples and comparative examples shown. [Modes for carrying out the invention]

[0019] Hereinafter, embodiments of the RF tag system according to the present invention will be described with reference to the drawings. Figure 1 is a schematic diagram illustrating the configuration of an RF tag system 1 (the present system 1) according to one embodiment of the present invention, where (a) is a conventional system and (b) is the present system 1. As shown in the figure, System 1 (and the conventional system) is an RF tag system that can communicate with an RF tag 20 attached to an object 100 by a reader / writer 10 equipped with a transmitting / receiving antenna 11 and read out tag information.

[0020] [This system / Previous system] Specifically, in this system 1 (and the conventional system), a reader / writer 10 is installed at a predetermined location on a logistics line through which the object 100 / surrounding items 200 to be managed and monitored are moved and transported, and communication is performed with the RF tag 20 attached to the object 100. Radio waves are emitted from a transmitting / receiving antenna 11 connected to the reader / writer 10, which enables communication with the RF tag 20 on the object 100 and reads out predetermined tag information. Furthermore, unlike conventional systems, this system 1 is equipped with a relay device 30 installed between the reader / writer 10 and the RF tag 20 moving along the logistics line, and a transmitting / receiving antenna 11 connected to the reader / writer 10.

[0021] By providing such a relay device 30, the system 1 can re-radiate radio waves received from the transmitting / receiving antenna 11 or RF tag 20 via the conductor 31 of the relay device 30, thereby enabling communication only with the target RF tag 20 from among multiple RF tags 20. More specifically, in the example shown in Figure 1, for example, in a site equipped with two logistics lines (conveyors, etc.) in front and behind, only the objects 100 flowing along the front logistics line are read by the reader / writer 10, while surrounding items 200 flowing along the rear logistics line are not read.

[0022] In this case, in the conventional system without a relay device 30, as shown in Figure 1(a), there are surrounding items 200 flowing along the rear line in addition to the target object 100 on the forward line, and the radio waves emitted from the transmitting and receiving antenna 11 communicate not only with the RF tag 20 on the target object 100 but also with the RF tags 20 attached to the surrounding items 200, resulting in a problem of misreading. Furthermore, depending on the condition of the item to which the RF tag 20 is attached (target item 100 / surrounding item 200), and individual differences in the RF tag 20, the sensitivity of the RF tag 20 of surrounding item 200 located further back may be relatively higher, potentially leading to misreading.

[0023] In contrast, in the system 1 equipped with a relay device 30, as shown in Figure 1(b), radio waves radiated from the transmitting and receiving antenna 11 pass through the conductor 31 of the relay device 30, and through linear polarization conversion and re-radiation (see Figures 2 and 5) and interference effects due to radio wave synthesis (see Figure 7), communication is made impossible, power amplified, and power canceled out. As a result, among multiple items (target object 100 / surrounding items 200) to which RF tags 20 are attached, communication is only possible with the RF tag 20 of the target object 100, and communication with the RF tags 20 of the other surrounding items 200 is not possible.

[0024] In this way, in this system 1, direct waves from the transmitting and receiving antennas 11 do not affect communication with any of the RF tags 20, and the interference effect of radio waves re-radiated from the relay device 30 allows for the creation of areas with strong and weak radio wave strength, making it possible to reconstruct the communication environment with radio waves that have passed through the relay device 30, and to amplify the radio waves at any point so that communication and transmission / reception occur only with the target RF tag 20. This makes it possible to easily and reliably eliminate the problem of misreading caused by communication between the RF tags 20 and unnecessary peripheral items 200 in conventional systems, without requiring, for example, expensive radio wave absorbers.

[0025] Furthermore, System 1 is characterized by the addition of a relay device 30 to a conventional RF tag system consisting of a reader / writer 10, a transmitting / receiving antenna 11, and an RF tag 20. The reader / writer 10, transmitting / receiving antenna 11, and RF tag 20, other than the relay device 30, can be configured and structured in the same way as in the conventional system. In other words, compared to conventional systems, System 1 can be realized simply by equipping a relay device 30 with a simple configuration, without requiring a dedicated RF tag structure equipped with a booster antenna, a complex reader / writer device configuration, or the installation of expensive radio wave absorbers, as proposed in the aforementioned Patent Documents 1-3.

[0026] Therefore, in this system 1, the RF tag system and the configuration of the RF tags themselves do not become more complex or larger, and the system can be made smaller and less expensive. Furthermore, since it is possible to use standard RF tags (inlays) and reader / writers from conventional systems, general-purpose inlays and reader / writers can be used as they are, and this system 1 can be realized without compromising the versatility and expandability of tags and reader / writers. This ensures that the greatest advantages of RF tags, such as their small size, thin profile, light weight, and ease of handling, which are characteristic of general-purpose inlays, are not compromised.

[0027] [Reader / Writer / RF Tag] In this system 1, the general-purpose inlay used as the RF tag 20 constitutes an RF tag that allows for wireless reading and writing of predetermined information to a general reader / writer (reading / writing device) 10. Examples of such tags include read-only, write-once, and read-write types. This type of inlay includes an IC chip that stores predetermined information and an antenna made of a conductive material that is electrically connected to the IC chip. The IC chip and antenna are mounted and laminated on the surface of an inlay substrate, which consists of a single sealing film made of a support material such as PET resin.

[0028] The IC chip and antenna mounted on the inlay substrate can be sealed and protected by being sandwiched between the sealing films that make up the inlay substrate, for example, by placing them between two folded sealing films, or by overlapping two sealing films. In this embodiment, a rectangular, strip-shaped inlay is used as the RF tag 20, in which an IC chip and antennas extending from both sides of the IC chip are sandwiched and sealed between rectangular inlay substrates. The IC chip of the RF tag 20 has a loop circuit formed by connecting loop-shaped circuit conductors around the chip, and antennas are connected to both the left and right sides of the IC chip via this loop circuit.

[0029] Then, via this antenna, wireless reading and writing (data retrieval, registration, deletion, update, etc.) is performed between the reader / writer 10 (transmitting / receiving antenna 11) and the IC chip, and the data recorded on the IC chip is recognized. Such RF tags (inlays) 20 have IC chips (semiconductor chips) such as memory on which they are mounted, which are capable of recording, for example, several hundred bits to several kilobits of data. The data recorded on the IC chip can include, for example, any data such as product identification code, name, weight, net weight, manufacturer / seller name, place of manufacture, date of manufacture, and expiration date, and can also be rewritten.

[0030] The communication frequency band used for communication between the reader / writer 10 and the RF tag 20 can be, for example, the 860MHz to 960MHz band, which belongs to the so-called UHF band. Generally, RF tags use several frequency bands, such as the band below 135 kHz, the 13.56 MHz band, the 860 MHz to 960 MHz band (part of the UHF band), and the 2.45 GHz band. The communication range varies depending on the frequency band used, and the optimal antenna length and wiring pattern also differ depending on the frequency band.

[0031] Generally, the antenna provided on the RF tag 20 is composed of a dipole antenna or the like, consisting of conductors extending linearly or meanderingly on both sides (left and right) of the IC chip. The conductors constituting the antenna are configured to extend linearly and symmetrically on both sides of the IC chip, for example, with a length of half a wavelength of the IC chip's communication frequency. The transmitting and receiving antenna 11 of the reader / writer 10 is generally a rectangular antenna, but it is often configured so that one side of a pair of opposing antennas is half the length of the communication frequency. In such RF tag antennas 20 and reader / writer 10 transceiver antennas 11, communication and transmission / reception are performed using linear polarization (vertical polarization / horizontal polarization) where the electric field oscillates along the direction of extension of the antenna, which extends to half a wavelength of the communication frequency.

[0032] [Linear Polarization (Vertical Polarization / Horizontal Polarization)] Figure 2 is an explanatory diagram illustrating the principle of polarization conversion in this system 1, where (a) is the case without the relay device 30 and (b) is the case with the relay device 30. As described above, in this system 1, the radio waves radiated from the antenna of the RF tag 20 and the transmitting / receiving antenna 11 of the reader / writer 10 are linearly polarized (vertical polarization / horizontal polarization) for communication and transmission / reception. Radio waves (electromagnetic waves) propagate through the interaction of electric and magnetic fields. The direction in which the electric field vibrates when radio waves propagate through space is called polarization, and waves in which this vibration direction is always the same are called linearly polarized waves. The direction of polarization is crucial for the reception and reflection of radio waves, and linear polarization is generally used in RF tag communication. Generally, when the direction of polarization is parallel to the ground, it is called horizontal polarization, and when it is perpendicular to the ground, it is called vertical polarization. In the drawings of this specification (Figures 2, 6, 10-12), the case where the polarization direction is parallel to the x-axis direction is referred to as horizontal polarization, and the case where the polarization direction is parallel to the y-axis direction is referred to as vertical polarization.

[0033] For linear polarization to work this way, the direction of vibration of the electric field (polarization direction) must match or be approximated at the transmitting and receiving ends of the radio waves. For example, as shown in Figure 2(a), if the polarization direction of the transmitted wave of the transmitting / receiving antenna 11 of the reader / writer 10 is vertical (vertical polarization), and the polarization direction of the antenna of the receiving RF tag 20 is horizontal (horizontal polarization), then the RF tag 20 will not be able to receive or communicate radio waves. In this system 1, by utilizing the characteristics of linear polarization (vertical polarization / horizontal polarization), the polarization direction of the transmitting and receiving antenna 11 of the transmitting reader / writer 10 (for example, the vertical direction) and the polarization direction of the antenna of the receiving RF tag 20 (for example, the horizontal direction) are made different.

[0034] In other words, in this system 1, the radio waves emitted by the transmitting / receiving antenna 11 and the RF tag 20 are both linearly polarized, and the installation positions of the transmitting / receiving antenna 11 and the RF tag 20 are set so that the polarization directions of the transmitting / receiving antenna 11 and the RF tag 20 are twisted by a predetermined angle Φ. As a result, the radio waves emitted from the transmitting / receiving antenna 11 will not be received or communicated with by the RF tag 20, regardless of whether they are directed at the target object 100 or surrounding items 200, thus preventing unwanted surrounding items 200 from directly receiving the radio waves emitted from the transmitting / receiving antenna 11.

[0035] Here, the predetermined angle Φ at which the polarization directions of the transmitting / receiving antenna 11 and the RF tag 20 are twisted is preferably 90°, where the polarization directions of both are orthogonal. When the polarization direction is twisted by 90°, it becomes possible to reliably prevent the transmission and reception of radio waves between the transmitting / receiving antenna 11 and the RF tag 20. However, this predetermined angle Φ is not limited to 90°, but can be set to any angle less than or equal to 90°, for example, in the range of approximately 72 to 90°. Within this range, the power transmitted from the transmitting / receiving antenna 11 to the RF tag 20 can be suppressed to less than 10% of the maximum efficiency, and the direct waves from the transmitting / receiving antenna 11 do not affect communication with any of the RF tags 20, making it possible to achieve the goal of reconstructing the communication environment using radio waves that have passed through the relay device 30.

[0036] Here, the maximum efficiency of power transmitted to the RF tag 20 is the efficiency of power transmitted when the torsion angle Φ is 0°, in other words, when the polarization directions of the transmitting / receiving antenna 11 and the RF tag 20 are parallel. If we let Wmax be the received power when the twist angle is 0°, and WΦ be the received power when the twist angle is Φ, then the relationship between Wmax and WΦ can be expressed as follows. WΦ = Wmax × (cosΦ)^2 If the twist angle Φ is, for example, 72°, WΦ = 0.095Wmax < 0.1Wmax As a result, the power transmitted from the transmitting / receiving antenna 11 to the RF tag 20 can be suppressed to less than 10% of the maximum efficiency.

[0037] Figure 3 is an explanatory diagram illustrating the relationship between the torsion angle Φ and the received power. (a) schematically shows the analysis environment, and (b) is a table comparing the analysis results with the effect of the torsion angle Φ. As shown in Figure 3(b), the power transmitted from the transmitting / receiving antenna 11 to the RF tag 20 for maximum efficiency can be calculated from the torsion angle Φ. The analysis equipment used here was the CST Studio Suite manufactured by AET Corporation. The analysis frequency was set to 920 MHz, and identical antennas resonating at 920 MHz were installed at the transmit and receive ports. The transmit and receive ports were spaced 600 mm apart, and the output power of the transmit port was set to 1000 mW.

[0038] Next, linearly polarized waves radiated with a predetermined twist angle Φ as described above can be received and communicated when the polarization directions of the transmitting and receiving sides approach or approximate each other to a certain extent. For example, as shown in Figure 2(b), if the polarization direction twist between the radio waves transmitted from the reader / writer 10's transmitting / receiving antenna 11 and the RF tag 20 on the receiving side is about 45°, the transmitted radio waves can be received and communicated with by the RF tag 20 on the receiving side. In this system 1, the characteristics of the communication range due to this polarization direction twist are utilized to convert (tilt) the polarization direction of the radio waves radiated from the transmitting / receiving antenna 11 of the transmitting reader / writer 10 so that it can be received and communicated with using the polarization direction of the antenna of the receiving RF tag 20.

[0039] In other words, in this system 1, by installing a relay device 30 between the transmitting / receiving antenna 11 and the RF tag 20, the polarization directions of the transmitting / receiving antenna 11 and the RF tag 20, which are set to be twisted by a predetermined angle Φ as described above, are re-radiated via the relay device 30. This converts and corrects the twist in the polarization direction, so that the polarization direction of the radio waves received from the transmitting / receiving antenna 11 (or RF tag 20) is tilted by a predetermined angle θ with respect to the polarization direction of the RF tag 20 (or transmitting / receiving antenna 11) before propagation and reception.

[0040] Specifically, when radio waves are received by the relay device 30, electrons vibrate along the direction of the conductor 31, and the conductor 31 re-emits the radio waves, with the polarization direction of the re-emitted electromagnetic waves being in the direction of the conductor 31 (see Figure 5). As a result, by arranging the conductor 31 of the relay device 30 at an angle to the polarization direction of the received radio waves, the polarization direction of the received radio waves can be converted to a direction along the conductor 31 and re-emitted. As a result, radio waves emitted from the transmitting and receiving antenna 11 are received and communicated with only when they are re-radiated via the relay device 30 and their polarization direction is converted and corrected, thereby preventing communication and misreading of unnecessary surrounding items 200, and ensuring that communication takes place only with the RF tag 20 of the target object 100.

[0041] In the relay device 30 described above, the predetermined angles θ1 and θ2 used to correct and tilt the polarization directions of the RF tag 20 and the correction and tilt of the correction and tilt of the RF tag 11 are preferably set to θ1 = θ2 = Φ / 2°. By tilting the radio waves, which have a twist angle of Φ between the transmitting / receiving antenna 11 and the RF tag 20, by Φ / 2 using the relay device 30, it becomes possible to transmit and receive radio waves and communicate between them. However, these predetermined angles θ1 and θ2 are not limited to the case of Φ / 2°; for example, the inclination θ1 and θ2 can be set in the range of approximately (Φ / 2-9)° to (Φ / 2+9)°. Within this range, the power transmitted from the transmitting / receiving antenna 11 to the RF tag 20 via the relay device 30 can be increased to more than 90% of its maximum efficiency, making it possible to achieve the goal of reconstructing the communication environment using radio waves transmitted via the relay device 30.

[0042] Here, the maximum efficiency of the power transmitted to the RF tag 20 via the relay device 30 is the efficiency of the power transmitted when the inclinations θ1 and θ2 are Φ / 2. For example, if the received power when the twist angle is 90° and the inclination is θ1=θ2=Φ / 2° is Wmax, and the received power when the inclination is θi (i=1, 2) is Wθi, then the relationship between Wmax and Wθi can be expressed as follows. Wθi=Wmax×(cosθ1)^2×(cosθ2)^2 If the twist angle Φ is 90° and the inclinations are θ1 = 54° and θ2 = 36°, Wθi = 0.905Wmax > 0.9Wmax As a result, the power transmitted from the transmitting / receiving antenna 11 to the RF tag 20 can be maintained at over 90% of its maximum efficiency.

[0043] Figure 4 is an explanatory diagram illustrating the relationship between the tilt θ1 or θ2 and the received power when the torsion angle is Φ = 90°. (a) schematically shows the analysis environment, and (b) is a table comparing the analysis results with the influence of the tilt θ1 or θ2. As shown in Figure 4(b), it can be seen that the power transmitted from the transmitting / receiving antenna to the RF tag 20 with maximum efficiency can be calculated from the slope θ1 or θ2. Furthermore, the transmitting port and the relay device, or the relay device and the receiving port, are spaced 300 mm apart. The relay device uses a rectangular conductor, and the output of the transmitting port is 1000 mW.

[0044] [Re-radiation via relay device] Here, we will explain the re-radiation by the relay device 30, which corrects and tilts the polarization direction. Figure 5 is an explanatory diagram for illustrating the re-radiation of radio waves in the relay device 30 (conductor 31) of this system 1, where (a) shows the state before the conductor 31 receives radio waves, (b) shows the state after the conductor 31 has received radio waves, and (c) shows the state after the conductor 31 has radiated (re-radiated) the received radio waves. In this system 1, radio wave re-radiation means that the conductor 31 of the relay device 30 acts as an antenna, thereby relaying radio waves.

[0045] The relay device 30 of this system 1 is constructed by attaching and laminating one or more conductors 31, formed by etching or other processes on the surface of a support 32 made of a dielectric material such as a PET film, at predetermined positions in predetermined shapes, sizes (length, area) and angles (see Figures 1 and 9). Furthermore, as the material constituting the support 32 that supports the conductor 31, a dielectric material that does not hinder re-radiation by the conductor 31 is preferred. Examples include thermoplastic resins and thermoplastic elastomers such as polycarbonate resin, acrylonitrile-ethylene-styrene copolymer (AES) resin, polypropylene resin, polyethylene resin, polystyrene resin, acrylic resin, polyester resin, polyphenylene sulfide resin, acrylonitrile-butadiene-styrene copolymer (ABS) resin, polyvinyl chloride resin, polyurethane resin, fluororesin, and silicone resin.

[0046] Furthermore, the conductor 31 of the relay device 30 receives radio waves transmitted from the reader / writer 10's transmitting / receiving antenna 11 and RF tag 20, and re-radiates them in the direction of propagation while changing and tilting the polarization direction of the radio waves by a predetermined angle θ. Specifically, as shown in Figure 5(a), first, the conductor 31 of the relay device 30 receives radio waves transmitted from the transmitting / receiving antenna 11 or RF tag 20. As shown in Figure 5(b), the electrons in the conductor 31 vibrate due to the influence of the radio waves. As a result of the vibration of the electrons in the conductor 31, as shown in Figure 5(c), the conductor 31 acts as an antenna and emits radio waves that depend on the orientation, length, and shape of the conductor 31.

[0047] In this system 1, the process by which radio waves received by such a relay device 30 are radiated using the conductor 31 as an antenna is referred to as "re-radiation." Then, the radio waves received by the relay device 30 cause electrons to vibrate along the direction of the conductor 31, and the conductor 31 reflects (re-radiates) the radio waves, and the polarization direction of the reflected (re-radiated) electromagnetic waves is in the direction of the conductor 31. In this way, by arranging the conductor 31 of the relay device 30 at a predetermined angle θ (for example, 45°) oblique to the polarization direction of the received radio waves, it becomes possible to receive a portion of the energy of the transmitted wave, change the direction of polarization, and reflect (re-radiate) the radio waves.

[0048] [Placement of relay devices] Next, we will explain the arrangement configuration of the relay device 30 that performs the re-radiation of radio waves as described above, and the radio wave synthesis based on it. Figure 6 is a schematic diagram illustrating the configuration of System 1, where (a) is the conventional system and (b) is System 1. As shown in the figure, in this system 1, one or more relay devices 30 that convert the polarization direction of radio waves and re-radiate them are installed at predetermined positions between the transmitting and receiving antennas 11 and the RF tag 20. Furthermore, the relay device 30 is configured to allow one or more conductors 31 to be arranged and stacked on the surface of the support 32 (see Figures 1 and 9).

[0049] By installing multiple relay devices 30, and by equipping each relay device 30 with multiple conductors 31, the interference effect of the radio waves re-radiated by the multiple relay devices 30 and the multiple conductors 31 makes it possible to increase (strengthen) the radio wave intensity at a specific location and decrease (weaken) the radio wave intensity at other specific locations. This enables reliable communication between the RF tag 20 attached to the object 100, which is moving to a specific location where the radio wave strength is high (or has become high), and the object 100. Furthermore, it becomes possible to prevent communication with RF tags 20 attached to surrounding items 200 that are not moving and are located at other specific locations where the radio wave intensity is high (or has increased).

[0050] [Radio wave synthesis using relay devices] Control of the re-radiated radio wave intensity by such multiple relay devices 30 / conductors 31 can be achieved through the interference effect of radio waves. Figure 7 is an explanatory diagram for illustrating the interference effect of radio waves in System 1, where (a) shows the synthesis of in-phase radio waves and (b) shows the synthesis of out-of-phase radio waves. The interference effect of radio waves can be explained by the phase difference caused by the difference in the paths the radio waves take to reach a given point. When radio waves are in phase, for example, when multiple waves all travel along the same path length, the waves are amplified because their phases are also equal, as shown in Figure 7(a), and the intensity of the combined radio wave becomes stronger. On the other hand, if the radio waves are in opposite phase, for example, if the path difference between multiple radio waves is 1 / 2λ and one of the waves propagates 1 / 2 wavelength longer (shorter), then as shown in Figure 7(b), the phases will also shift by 1 / 2λ, causing the waves to cancel each other out, and the intensity of the combined radio wave will be weaker.

[0051] The radio wave strength obtained by combining radio waves in this way can be set and controlled by adjusting the path difference of multiple radio waves by adjusting the position and manner in which one or more relay devices 30 / conductors 31 are installed between the transmitting / receiving antenna 11 of the reader / writer 10 and the RF tag 20. Therefore, depending on the configuration of one or more relay devices 30 / conductors 31, even if the radio waves transmitted from the transmitting / receiving antenna 11 are of low power, the radio wave intensity at a specific point can be increased and the radio wave intensity at other specific points can be decreased, thereby enabling communication only between the RF tag 20 of the target object 100 and the reader / writer 10, and preventing communication with the RF tags 20 of other unnecessary surrounding items 200.

[0052] [Half-power angle of the antenna] Furthermore, it is desirable to install the relay device 30 for radio wave synthesis within the half-power angle range of the reader / writer 10's transmitting / receiving antenna 11. Figure 8 is an explanatory diagram illustrating the range of half-width angles in which the relay device 30 of this system 1 is located. The half-power angle is the angle between the point where the radiation intensity of electromagnetic waves emitted from an antenna is maximal and the point where it drops by 3 dB. It is also called the 3 dB beamwidth or beamwidth. By installing the relay device 30 within the half-power angle range of the reader / writer 10's transmitting / receiving antenna 11, the strength of the radio waves received and re-radiated by the relay device 30 can be strongly maintained, making communication with the RF tag 20 of the target object 100 more reliable.

[0053] [Example of relay device configuration] Next, we will describe a specific configuration example of the relay device 30 of this system 1 as described above. As described above, the relay device 30 is constructed such that a conductor 31 made of a thin metal film or the like is supported and held by a support 32 made of a dielectric or the like, and its configuration can be as shown in Figure 9, for example. Figures 9(a) to 9(d) are schematic diagrams illustrating the configuration of the relay device 30 included in this system 1.

[0054] The relay device 30 in Figure 9(a) is an example in which multiple (two) conductors 31 are arranged on the surface of a support 32 made of a dielectric material configured in a rectangular shape, and this relay device 30 can be positioned in a predetermined location by any method. Figure 9(b) shows the case where multiple (two) relay devices 30, as shown in Figure 9(a), are provided. Figure 9(c) shows the case where multiple (two) conductors 31 are arranged on the surface of a parabolic antenna-shaped support 32. Figure 9(d) shows a case where the support 32 is configured as a pole-shaped, stationary stand, and multiple (two) relay devices 30, each with a conductor 31 attached to its tip (upper end), are provided.

[0055] It should be noted that the configurations shown in Figures 9(a) to (d) above are merely examples, and the configuration and structure of the relay device 30 are not limited to the example shown in Figure 9. In other words, the relay device 30 of this system 1 can have any configuration or structure as long as it can install and support a conductor 31 at a predetermined location that relays radio waves transmitted and received between the reader / writer 10's transmitting / receiving antenna 11 and the RF tag 20, and converts and corrects the polarization direction before re-radiating them. The physical configuration itself is not particularly limited. [Examples]

[0056] The following describes a specific example of the RF tag system 1 according to this embodiment. The present invention will be described in more detail by the following examples, but the present invention is not limited in any way by the following examples. Figure 10 is an explanatory diagram illustrating one embodiment of System 1, where (a) shows a conventional system as a comparative example and (b) shows System 1 as an embodiment.

[0057] As shown in the figure, for a reading test of multiple RF tags 20, an environment is assumed in which a "target tag" and relatively high-performing "unnecessary tags" exist around it. "Tag 1," which is the "target tag," and "Tag 2," which is the "unnecessary tag," are placed behind it. In this embodiment, the polarization direction of the transmitting and receiving antennas is set to "vertical" (Y-axis direction), the polarization direction of the RF tags (tag 1 and tag 2) is set to "horizontal" (X-axis direction), and two relay devices 1 and 2 are installed between the transmitting and receiving antennas and the RF tag (tag 1). In the comparative example, both the transmitting and receiving antennas and the RF tag were polarized horizontally (in the X-axis direction), and no relay device was installed.

[0058] Specifically, we are considering an environment where, in relation to the target tag (tag 1), the unnecessary tag (tag 2) may be placed and passed through the following locations. Tag 1 (the target tag) was positioned at position 1: (x,y,z)=(0,0,50)cm, with the transmitting / receiving antenna 11 as the origin. Tag 2 (unnecessary tag) was placed at positions 2-1 to 2-6 after Tag 1, with each tag 2 being positioned differently (positions 2-1, 2-2, 2-3, 2-4, 2-5, and 2-6). Figure 11 is an explanatory diagram illustrating the details of the placement of unnecessary tags in the examples and comparative examples shown in Figure 10. As shown in the figure, the devices were placed at the following positions: 2-1: (x,y,z)=(0,0,80)cm, 2-2: (x,y,z)=(0,0,110)cm, 2-3: (x,y,z)=(0,0,140)cm, 2-4: (x,y,z)=(30,0,80)cm, 2-5: (x,y,z)=(30,0,110)cm, and 2-6: (x,y,z)=(30,0,140)cm.

[0059] The relay devices consisted of two devices, relay device 1 and relay device 2, each composed of a PET film support and an aluminum sheet conductor. Figures 12 and 13 are explanatory diagrams illustrating the details of the relay device of the embodiment shown in Figure 10. As shown in the figure, the relay device 1 consists of conductors, each 11 cm long and 1 cm wide, placed parallel to each other at a 45° angle at the center of a square-shaped support (x,y) = (±5.0,±5.0) cm, and positioned at (x,y,z) = (0,0,20) cm relative to the origin of the transmitting and receiving antennas. The relay device 2 consists of conductors, each 17 cm long and 1 cm wide, positioned parallel to each other at a 45° angle at the center of a square-shaped support structure (x,y)=(±2.5,±2.5) cm. These conductors are placed 20 cm behind the relay device 1, at a position (x,y,z)=(0,0,40) cm with the transmitting and receiving antennas as the origin.

[0060] In the above-described environment, both the example and comparative example transmitted radio waves at a frequency of 920 MHz from the transmitting and receiving antenna (reader / writer), and the difference in output of the reader / writer when the target tag (tag 1) and the unnecessary tag (tag 2) were activated was measured as "output margin" (Measurement 1: Comparative Example, Measurement 2: Example), and the evaluation was performed based on the difference in "output margin" between the environment of the present invention (Example) and the normal environment (Comparative Example). Figure 14 is a graph showing the frequency characteristics of the RF tags used in the comparative example and the example. Tag 2 (unnecessary tag) was an RF tag that started up at approximately 3.0 dB lower power than Tag 1 (target tag). In both the example and comparative examples, the reader / writer used was a Voyantic product, Tagformance, and the transmitting / receiving antenna was a Voyantic product, Standard Patch Antenna.

[0061] As shown in the same figure, Figure 15 shows the details of the results for the examples and comparative examples. In the comparative example (Measurement 1: see Figure 11), it was found that when the unwanted tag was placed and passed through position 2-1, the difference in starting power (output margin) between it and the target tag (position 1) was "0.0 dB," making it impossible to avoid misreading. On the other hand, in the example (Measurement 2: see Figure 11), it was found that regardless of where the unwanted tag passed within the range of position 2, there was a difference of at least approximately 6.5 dB in the communicable activation power between the target tag and the unwanted tag, and that misreading could be avoided by setting the output of the reader / writer to, for example, 13.0 dB.

[0062] Furthermore, comparing the output margins at each position (positions 2-1 to 2-6) between the comparative example and the embodiment, it was found that the embodiment had a larger output margin at all positions, indicating that the communication environment was improved in accordance with the objective. Note that in the example shown in Figure 15, there are items marked "-" in the tag activation reader / writer output [dB] for unnecessary tags. This indicates that the tags did not activate even when outputting the maximum output of 27.0 [dB] of the reader / writer used in this example. Therefore, the output margin is set to 14.0 or higher.

[0063] As a result, in the comparative example, for example at position 2-1, the output of the reader / writer that can respond to both tag 1 and tag 2 is the same (4.5 [dB]), making it impossible to set the output to communicate only with tag 1. In contrast, in the embodiment, the output of the reader / writer that can respond can be made different for tag 1 (13.0 [dB]) and tag 2 (19.5 [dB]), making it possible to set the output to communicate only with tag 1 with ample margin (see Figure 10). Therefore, in this system 1, it was found that by increasing the startup power of the RF tags 20 at any predetermined location due to the interference effect of the relay device 30, an environment can be created in which only the target RF tags 20 can communicate.

[0064] In the above examples and comparative examples, for the sake of explanation, the transmit / receive antenna of the reader / writer was set as the origin, the positions of tag 1 and the relay device were fixed, and measurements were taken with tag 2 at multiple different positions. However, in this system 1, regarding the relative positions of the RF tag 20 and the relay device 30, as long as a position that allows communication only with the target RF tag 20 can be identified and set, any position of the reader / writer 10, transmitting / receiving antenna 11, RF tag 20, and relay device 30 may be fixed, or any position may be moved or changed. For example, in the above embodiment, by fixing the position of tag 2 and varying the positions of tag 1 and / or the relay device, it is of course possible to identify a location or area where communication is possible only with tag 1.

[0065] As described above, the RF tag system 1 of this embodiment does not require a specific, dedicated structure or configuration like conventional RF tags. It uses general-purpose inlays and reader / writers as they are, and communicates only with the RF tag 20 of the target object 100, preventing communication with the RF tags 20 of unnecessary surrounding items 200. Therefore, according to the RF tag system 1 of this embodiment, it is possible to provide an RF tag system that is not limited to the flow paths and transport routes of the target object 100 and surrounding items 200, but is applicable to logistics sites and distribution sites where various target objects 100 and surrounding items 200 are handled. It is also possible to use existing readers / writers 10 and general-purpose inlays as they are, the entire system can be configured inexpensively and simply, and it is possible to realize a highly reliable RF tag system that is excellent in versatility and expandability and can reliably eliminate misreadings.

[0066] Thus, according to the present invention, general-purpose inlays and reader / writers can be used as they are without requiring complex configurations or structures, and it is possible to reliably communicate with only the target RF tag from among the necessary multiple RF tags without errors. This will enable us to provide an RF tag system that is suitable for logistics management and product management involving large quantities of products.

[0067] Although the RF tag system of the present invention has been described above with reference to preferred embodiments and examples, it goes without saying that the RF tag system according to the present invention is not limited to the embodiments and examples described above, and various modifications can be made within the scope of the present invention. In the embodiments described above, the RF tag system according to the present invention was explained using an example where it is used in a logistics system that manages and monitors a large number of products moving along a logistics line. However, it goes without saying that the RF tag system of the present invention can be applied to systems other than product management in logistics systems. For example, the present invention can be applied to any situation or environment where it is necessary to manage and monitor objects using an RF tag system, such as warehouses, factories, and port facilities that transport products using forklifts.

[0068] Furthermore, in the embodiments described above, products handled in large quantities by logistics companies and the like were used as examples of objects targeted by the RF tag system according to the present invention. However, the articles and objects targeted by the RF tag system of the present invention are not particularly limited. In other words, the RF tag system according to the present invention can be applied to any item or object that uses an RF tag and has predetermined information or data read and written via a reader / writer, and it can of course be used for items and objects other than products handled by logistics companies, etc. [Industrial applicability]

[0069] The present invention can be suitably used as an RF tag system for product management and logistics management by reading RF tags attached to items or objects to be managed, such as products flowing through a logistics line or goods being transported by a forklift. [Explanation of symbols]

[0070] 1 RF Tag System 10 Leaders and Writers 11 Transmitting and Receiving Antennas 20 RF tags 30 Relay device 31 Conductor 32 Support 100 Objects 200 Peripheral items

Claims

1. An RF tag system comprising a transmitting and receiving antenna, an RF tag, and a relay device, The relay device is, The device comprises a conductor and a support for the conductor, It is installed between the transmitting / receiving antenna and the RF tag, The conductor re-radiates radio waves received from the transmitting / receiving antenna or the RF tag. The interference effect of radio waves re-radiated by multiple conductors makes it possible to increase the radio wave intensity at a specific location. An RF tag system characterized by the following features.

2. The transmitting and receiving antenna and the RF tag are, The radio waves emitted are both linearly polarized, and the polarization directions of the transmitting and receiving antenna and the RF tag are installed so that they are twisted by a predetermined angle Φ. The aforementioned conductor is The polarization direction of the radio waves received from the transmitting and receiving antenna is tilted by a predetermined angle θ1 and then re-radiated. The polarization direction of the radio waves received from the RF tag is tilted by a predetermined angle θ2 and then re-radiated. The RF tag system according to feature 1.

3. The predetermined angle Φ is any angle less than or equal to 90°. The predetermined angle θ1 is such that 0 < θ1 < Φ, The predetermined angle θ2 is such that 0 < θ2 < Φ. The RF tag system according to claim 2, characterized in that it is the same as described in claim 2.

4. The relay device is composed of at least two or more conductors. The RF tag system according to any one of claims 1 to 3.

5. The support is composed of a dielectric material. The RF tag system according to any one of claims 1 to 4.

6. The aforementioned support is Supporting one or more of the conductors The RF tag system according to any one of claims 1 to 5.

7. The relay device is, One or more are installed between the transmitting / receiving antenna and the RF tag. The RF tag system according to any one of claims 1 to 6.

8. The relay device is, It is installed within the half-power angle range of the aforementioned transmitting and receiving antenna. The RF tag system according to any one of claims 1 to 7.

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