RFID tag assembly and identification object having RFID tag assembly

Abstract

The present invention provides a radio frequency identification tag assembly including: a conductive radiating medium having a first portion and a second portion with a gap between the first portion and the second portion; a thin film antenna including a PCB and metal wires extending in different directions from both sides of the PCB; and an insulating attachment that separates the conductive radiating medium from the thin film antenna.

Description

[Technical Field]

[0001] The present invention relates to the field of radio frequency identification (RFID), and more particularly to radio frequency identification tag assemblies and identification objects having radio frequency identification tag assemblies. [Background technology]

[0002] In recent years, passive RFID technology has been closely integrated with sensors, beacons, and other devices in various fields into the Internet of Things (IoT), and can be further integrated with Bluetooth Low Energy (BLE) technology. In particular, RFID technology can be used in advanced ways for intelligent management of the production, distribution, storage, and transportation of construction equipment. It can simultaneously identify multiple UHF RFID passive tags in a contactless manner, which is more efficient than repeatedly identifying a single tag. Construction equipment is typically rented for use on construction sites, but it requires storage, installation, and management during the rental period. Automation and more intelligent management methods are needed to improve repetitive management processes, reduce management costs, prevent equipment loss and storage / retrieval errors, and manage the equipment's useful life to ensure employee safety.

[0003] Passive RFID technology offers the advantages of cost savings and ease of use. When identifying construction equipment with a curved, three-dimensional structure, RFID tags must be attached to the surface of the equipment to identify and manage the equipment. However, the curved surface makes it difficult to attach RFID tags. For use in construction sites, thin RFID tags that do not protrude significantly from the surface of the equipment are advantageous. At construction sites, cylindrical metal support rods that support the substructure during maintenance after the exterior walls of a building are formed and concrete is poured are a typical example of such construction equipment, and they are used frequently and require frequent and continuous maintenance. Due to the harsh construction environment, tags attached to construction equipment must be able to withstand external impacts and drops during use and transportation. Furthermore, when attaching tag assemblies by processing the curved surface of equipment, tag structures that protrude a certain thickness from the curved surface are vulnerable to physical damage during installation, storage, and transportation of the equipment. Considering the diversity of curved, three-dimensional metal instruments, their difficult-to-process characteristics, and the harsh usage environments in which they may be subjected to impacts, drops, water, and chemical erosion, dedicated RFID tags that are metal-resistant, impact-resistant, and chemical-resistant are required.

[0004] FIG. 1 shows an RFID tag assembly attached to the surface of a cylindrical metal object. The RFID tag assembly 120 is attached to the surface of the metal object 100 using a bracket 110 in the form of striped protrusions. Metal objects with this structure are used not only for construction purposes but also for oil and gas pipelines, pipelines installed in buildings and facilities, and underground pipelines for laying and protecting electrical conduits and communication cables. Due to the cylindrical structure and uneven surface of metal objects, if an RFID tag assembly is attached to one side of a cylindrical metal object, the grounding surface below the tag may come into contact with the metal material, making it difficult to maintain electrical stability. Even with the same tag assembly, the performance of the RFID tag assembly may vary depending on the attachment environment and usage conditions. To attach a tag assembly to the surface of a curved cylindrical metal object, a special bracket designed to accommodate the curved surface radius must be used, or the plastic case must be modified to accommodate attachment to a curved surface, which increases the cost of use.

[0005] When a small RFID tag assembly is attached to a cylindrical metal object, the identification performance, identification distance, and identification rate of the RFID tag assembly change sensitively with changes in the radius of the cylindrical metal object and the tag identification angle (φ). When the radius of the cylindrical object is large, or when the tag assembly is identified in a direction that is different from the tag's attached direction or even opposite to the tag's attached direction, identification capability decreases significantly, seriously affecting the practicality and usability of the tag assembly. When used on an actual construction site, it is almost impossible to arbitrarily adjust the tag angle to take into account the tag reading direction after the equipment has been installed and used. This requires aligning the tag's orientation with the reader when using the equipment, increasing management and labor costs and reducing the efficiency of RFID tags. Therefore, the electrical performance of the RFID tag must be designed to prevent the identification distance from changing sensitively depending on the RFID tag's attachment direction. Therefore, the identification rate at different identification directions (φ changes) on cylindrical metal objects is an important design factor.

[0006] Therefore, it is necessary to consider the above factors in the application environment and improve the protection, durability and identification of the attached RFID tag assembly. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to overcome the above and / or other problems in the prior art. The proposed RFID tag assembly of the present invention is attached to a cylindrical metal object so as to surround the surface of the cylindrical metal object, thereby improving the omnidirectional readability and identification distance performance of the tag. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a radio frequency identification tag assembly comprising: a conductive radiating medium having a first portion and a second portion with a gap between the first portion and the second portion; a thin film antenna including a PCB and metal wires extending in different directions from opposite sides of the PCB; and an insulating attachment separating the conductive radiating medium and the thin film antenna.

[0009] According to a second aspect of the present invention, there is provided an identification object having on its exterior a radio frequency identification tag assembly as described above.

[0010] The present invention conformally wraps and attaches an RFID tag assembly packaged with a special material to a curved, three-dimensional metal object. This avoids the inherent problems associated with protruding RFID tag assemblies when the curved, three-dimensional metal object is used in building and construction sites, eliminating the need for conventional handling procedures during storage, transportation, and installation of the object. In particular, in special environments such as construction sites, where external impacts, drops, and collisions can occur frequently during transportation, installation, storage, and loading of the object, the RFID tag assembly of the present invention provides the advantage of enhancing the durability of the RFID tag assembly attached to the curved, three-dimensional metal object, thereby extending its service life. Furthermore, since it is difficult to ensure that the antenna direction of a tag reader and the radiation polarization plane of the RFID tag assembly are always aligned at construction sites, the RFID tag assembly of the present invention enhances omnidirectional identification capabilities, allowing for easy identification not only in all directions but also from relatively far away. Furthermore, taking into account harsh application environments, a special packaging process is used to improve the durability of the RFID tag assembly.

[0011] Other features and aspects will become apparent from the following detailed description, drawings, and claims.

[0012] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the following will briefly describe the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without paying creative labor. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows a schematic diagram of an RFID tag assembly attached to the surface of a cylindrical metal object. [Figure 2a] 1A and 1B show perspective and cross-sectional views of an RFID tag assembly surrounding a surface of a cylindrical metal piece according to an embodiment of the present invention. [Figure 2b]1 shows a front view of an RFID tag assembly surrounding a surface of a cylindrical metal piece of equipment according to an embodiment of the present invention. [Figure 2c] 1 shows a rear view of an RFID tag assembly surrounding a surface of a cylindrical metal piece of equipment according to an embodiment of the present invention. [Figure 2d] 10 shows a rear view of an RFID tag assembly surrounding a surface of a cylindrical metal piece according to another embodiment of the present invention. [Figure 3a] 1 shows a top view of a deployed RFID tag assembly according to an embodiment of the present invention. [Figure 3b] 1 shows a side exploded view of an RFID tag assembly according to an embodiment of the present invention. [Figure 4a] 3 shows an enlarged view of a PCB 310 portion of a thin film antenna 300 according to an embodiment of the present invention. [Figure 4b] 3 shows an enlarged view of a PCB 310 portion of a thin film antenna 300 according to an embodiment of the present invention. [Figure 5a] 4 shows a graph of the real and imaginary components of the input impedance versus frequency when the ends of a conductive radiating medium 400 are truncated, according to an embodiment of the present invention. [Figure 5b] 4 shows a graph of the real and imaginary components of the input impedance versus frequency when the ends of a conductive radiation medium 400 are shorted according to an embodiment of the present invention. [Figure 6a] 10 shows a graph of the distinguishable distance of an RFID tag assembly 200 versus frequency when the RFID reader is rotated 0°, 90°, and 180° relative to a PCB 310 when an end of a conductive radiating medium 400 is cut off according to an embodiment of the present invention. [Figure 6b] 10 shows a graph of the distinguishable distance of the RFID tag assembly 200 versus frequency when the RFID reader is rotated 0°, 90°, and 180° relative to the PCB 310 when the ends of the conductive radiating medium 400 are shorted according to an embodiment of the present invention. [Figure 7] 1 illustrates a radiation pattern of an RFID tag assembly in the axial plane of a cylindrical metal object according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] In order to make the above objects, features and advantages of the present invention more clearly comprehensible, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0015] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention; however, the present invention may be practiced in other ways than those described herein, and those skilled in the art will be able to make similar applications without departing from the spirit and scope of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0016] The present invention will now be described in detail with reference to schematic diagrams, and in describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional views showing the device structure are not enlarged to a general scale, and the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of the present invention herein, and the actual fabrication should include three-dimensional spatial dimensions of length, width and depth.

[0017] Specific embodiments of the present invention will be described below. However, for the sake of brevity, it is not possible to fully describe all features of actual embodiments in this specification. It should be understood that in the actual implementation of any embodiment, various specific decisions are often made in the course of any engineering or design project to achieve the specific goals of the developer and to satisfy system-related or commercial constraints, and these decisions may vary from one embodiment to another. It should also be understood that such development may require complex and lengthy efforts, but for those skilled in the art related to the content disclosed in this invention, some changes in design, manufacturing, production, etc. made based on the technical content disclosed in this disclosure are merely existing technical means, and should not be understood as deficient in the content of this disclosure.

[0018] Unless otherwise defined, technical or scientific terms used in the claims and the specification shall have the ordinary meaning understood by a person of ordinary skill in the art to which the invention pertains. The terms "first," "second," and similar terms used in the specification and claims of this invention patent application do not denote any order, quantity, or importance, but are used merely to distinguish different components. Similar terms such as "one" or "1" do not denote a quantitative limitation, but indicate the presence of at least one. Similar terms such as "comprise" or "include" mean that the element or object preceding "comprise" or "include" encompasses the elements or objects listed after "comprise" or "include" and their equivalents, but do not exclude other elements or objects. Similar terms such as "connected" or "connected" do not limit connections to physical or mechanical connections, whether direct or indirect.

[0019] In this application, all embodiments and preferred embodiments described in this specification can be combined with each other to form new technical solutions unless otherwise specified. In this application, all technical features and preferred features described in this specification can be combined with each other to form new technical solutions unless otherwise specified.

[0020] In the description of the embodiments of the present application, the term "and / or" is merely a relational relationship describing related objects, and means that three types of relationships may exist. For example, A and / or B can mean that A exists alone, that A and B exist simultaneously, or that B exists alone. In addition, the character " / " in the text generally indicates that the related objects before and after it are in an "or" relationship.

[0021] The present invention divides the conductive radiation medium into a first portion and a second portion using a gap, electrically couples the conductive radiation medium and the thin film antenna at a certain distance, and surrounds the cylindrical metal substrate with a certain thickness between them, thereby providing good omnidirectional identification performance for the RFID tag assembly. The present invention also provides a PCB for the thin film antenna with an undercut groove for accommodating an IC chip, and a welding structure within the peripheral range of the PCB. The PCB is covered by a package structure, and the thin film antenna is covered with an insulating layer, thereby protecting the RFID tag assembly from the influence of the external environment and improving its durability and service life. The present invention also tilts the metal wire of the thin film antenna relative to the gap in the conductive radiation medium and shorts or cuts both ends of the conductive radiation medium, allowing the RFID tag assembly to adapt to different cylindrical metal substrate structures and shapes, providing different impedances to achieve impedance matching between the conductive radiation medium and the thin film antenna.

[0022] FIG. 2a shows a perspective view and a cross-sectional view of an RFID tag assembly surrounding the surface of a cylindrical metal workpiece according to an embodiment of the present invention. FIG. 2b shows a front view of an RFID tag assembly surrounding the surface of a cylindrical metal workpiece according to an embodiment of the present invention. FIG. 2c shows a rear view of an RFID tag assembly surrounding the surface of a cylindrical metal workpiece according to an embodiment of the present invention. FIG. 2d shows a rear view of an RFID tag assembly surrounding the surface of a cylindrical metal workpiece according to another embodiment of the present invention. In the above description, the side on which a printed circuit board (PCB) is mounted is referred to as the front (as shown in FIG. 2b), the direction aligned with the PCB (i.e., the direction perpendicular to the cut surface of the PCB in the circumferential direction when the RFID tag assembly surrounds the cylindrical metal workpiece) is defined as φ=0°, the side of the RFID tag assembly facing the PCB after surrounding the cylindrical metal workpiece is referred to as the back / rear side, and this rear side (facing the direction of φ=0° around the periphery of the cylindrical metal workpiece) is defined as φ=180°. However, those skilled in the art will understand that terms such as "front," "back," "rear," "front view," "rear view," etc. are intended to indicate relative positions in a certain state only and are not intended to limit a particular orientation. Although the present invention has been shown with respect to a cylindrical metal article as an exemplary embodiment, those skilled in the art will understand that the present invention can be widely applied to articles having various curved three-dimensional structures.

[0023] FIG. 3a shows a top view of an deployed RFID tag assembly according to an embodiment of the present invention, and FIG. 3b shows a side exploded view of an RFID tag assembly according to an embodiment of the present invention.

[0024] In the embodiment of FIGS. 2a-3b, the RFID tag assembly 200 includes a thin-film antenna 300, a conductive radiating medium 400, and an insulating attachment 350. The conductive radiating medium 400 has an area L×W and is divided into a first portion 410 and a second portion 420 by a gap 430 having a width d. Preferably, the gap 430 may be linear, and the first portion 410 and the second portion 420 may have the same shape. However, it should be understood that the gap may be formed in other shapes, and the first portion 410 and the second portion 420 may have different shapes. Considering the high temperatures during final packaging and assembly, the RFID tag assembly 200 may be formed using a method such as heat pressing using materials such as polyester (PET), polyimide (PI), and aluminum foil. The PET may be used as the bottom surface of the product, and the PI may be used to protect the chip. The thin-film antenna 300 includes a PCB 310 and metal wires extending in different directions from both sides of the PCB 310. An IC chip is included in the PCB 310, and the IC chip is connected to metal wires on both sides of the PCB 310. Although the metal wires on both sides in Figures 3a and 3b have the same length, it is possible to select for the metal wires on both sides of the PCB 310 to have different lengths. Alternatively, as shown in Figures 3a and 3b, the projection of the PCB 310 in the plane of the conductive radiating medium 400 is aligned with the gap 430, and the metal wires extend above the first portion 410 and the second portion 420 of the conductive radiating medium 400, respectively. When the length of the thin film antenna 300 is T L and the length T of the thin film antenna 300 is determined based on the resonant frequency of the RFID tag assembly 200. L The thin film antenna 300 is oriented in one direction in a plane parallel to the conductive radiation medium 400, for example, in the embodiment shown in FIG. 3a, the thin film antenna 300 is oriented at an angle ST with respect to the direction in which the gap 430 of the conductive radiation medium 400 extends in the plane parallel to the conductive radiation medium 400. ang Alternatively, as shown by the dashed line in Figure 3a, the tilt angle ST ang can be changed to, for example, 90 degrees. angThe design variable is to increase the length of the thin film antenna 300 without increasing the size of the RFID tag assembly 200. L can be changed to provide a more uniform radiation pattern and obtain omnidirectional distinguishable performance. ang It is believed that this adjustment allows for finer impedance adjustment so that the thin film antenna 300 is impedance-matched to the conductive radiating medium 400 without changing other variables of the RFID tag assembly. The thin film antenna 300 and the conductive radiating medium 400 are electrically coupled with a certain thickness T2 between them. As shown in FIG. 3b, this spacing thickness T2 is provided by an insulating attachment 350 having a thickness T2 below the thin film antenna 300. The insulating attachment 350 may be formed in the form of an insulating adhesive tape. The shape of the insulating attachment 350 may be larger than the shape of the thin film antenna 300. For example, the edge of the insulating attachment 350 may surround the edge of the thin film antenna 300, and the insulating attachment 350 may support the thin film antenna 300 so as not to directly contact the conductive radiating medium 400.

[0025] In the RFID tag assembly 200 of the present invention, the maximum electric field is concentrated at the center of the thin film antenna 300 connected to the PCB and at the center of the conductive radiation medium 400 divided into the first and second parts, and it is used as a long-distance radiation groove of the RFID tag assembly substantially regardless of the cylindrical metal object 100. In practical application, the size of the conductive radiation medium 400, the length T of the thin film antenna 300, L and the tilt angle ST of the thin film antenna 300 ang Coupling is a key design variable for achieving maximum radiation gain and impedance matching for the RFID tag assembly 200 of the present invention.

[0026] In the embodiment of Fig. 3b, the packaging process can bond the conductive radiation medium 400 to the metal workpiece at a thickness T1 away from the curved surface of the metal workpiece, which can be provided by a bottom insulating layer 600 typically made of insulating tape or a foam-based material. The spacing thickness T1 between the RFID tag assembly 200 and the curved surface of the cylindrical metal workpiece 100 is an important design variable that determines the identification distance performance of the RFID tag assembly 200 of the present invention, and the greater the spacing thickness T1, the greater the identification distance of the RFID tag assembly 200. However, the greater the thickness T1 of the bottom insulating layer 600, the more difficult it is for the RFID tag assembly 200 to surround and adhere to the cylindrical metal workpiece 100 and the greater the flexibility of the packaging material (e.g., the bottom insulating layer 600). Therefore, it is necessary to select an appropriate thickness of the bottom insulating layer T1 so as to improve the tag identification performance of the RFID tag assembly 200 and make the RFID tag assembly 200 easy to attach.

[0027] Alternatively, as shown in FIG. 3b, a top insulating layer 500 may be coated on top of the RFID tag assembly 200. Such an upper top insulating layer 500 may be integrally formed with a bottom insulating layer 600 for separating the RFID tag assembly 200 from the curved surface of the cylindrical metal substrate 100 through a packaging process. To clearly illustrate the structure of the RFID tag assembly, the top insulating layer 500 is not explicitly shown in FIGS. 2a-2b and 3a. However, it should be understood by those skilled in the art that the top insulating layer 500 may be formed on the outside of the RFID tag assembly 200 of FIGS. 2a-2b based on the structure shown in FIG. 3b. The top insulating layer 500 protects the RFID tag assembly 200 from corrosion in the external environment and enhances protection of the RFID tag assembly 200 by embedding the thin film antenna 300 therein. In an embodiment of the present invention, embedding the RFID tag assembly 200 in a special packaging material can increase the durability of the RFID tag assembly in incidents such as drops and impacts that may occur in the storage, transportation, and installation environments of cylindrical metal objects.

[0028] The structure in which the thin film antenna 300 and the conductive radiation medium 400 are coupled at a fixed distance within a specific packaging material can prevent the performance of the RFID tag assembly from changing sensitively due to errors that may occur during the packaging process or manufacturing. In addition, the structure of the RFID tag assembly spaced a fixed thickness T1 from the surface of the cylindrical metal article 100 can improve the drawback of sensitive changes in identification performance depending on changes in the radius of the cylindrical metal article 100.

[0029] 2a to 2d, the RFID tag assembly 200 described above with reference to FIGS. 3a to 3b surrounds the exterior of the curved surface of a cylindrical metal workpiece along the extension direction of the gap 430. In other words, when the RFID tag assembly 200 surrounds the exterior of the cylindrical metal workpiece, the gap 430 surrounds the circumferential direction of the cylinder. The thin conductive radiation medium 400 is attached in a curved form at a certain thickness from the surface of the cylindrical metal workpiece 100. This thickness can be formed by the bottom insulating layer 600, which can be realized by a special resin material and formed by integrally molding the top insulating layer 500 with the top insulating layer 500. In particular, when the top insulating layer 500 and the bottom insulating layer 600 are integrally molded and packaged using a special resin material, the layer can be realized by a UV resin or a foaming resin-based material that reacts to light of a specific wavelength and has properties similar to the solidification of plastic. A thin conductive radiation medium 400 can be attached to the bottom insulating layer 600. In the embodiments shown in FIGS. 2a-2d and 3a-3b, the conductive radiation medium 400 is divided into a first portion 410 and a second portion 420, and the width of the gap 430 between the first portion 410 and the second portion 420 is d. Since a processing temperature of approximately 70°C to 75°C is typically required for packaging resin materials, the conductive material forming the conductive radiation medium 400 can be selected from aluminum foil, PET material, and high-temperature PI material that can withstand such processing temperatures. In the embodiment shown in FIG. 2c, the end of the conductive radiation medium 400 is cut on the back surface, while in the embodiment shown in FIG. 2d, the end of the conductive radiation medium 400 is short-circuited on the back surface (φ=180°). The structure of the short circuit or cut of the conductive radiation medium 400 depends on the radius of the cylindrical metal substrate 100. Considering the expansion of the radiation groove of the RFID tag assembly 200 and the impedance matching between the conductive radiation medium 400 of the RFID tag assembly 200 and the thin film antenna 300, it is possible to select whether the end of the conductive radiation medium 400 is short-circuited or cut based on the size (cross-sectional size, radius) of the cylindrical metal object 100 and corresponding design variables.

[0030] 4a and 4b show enlarged views of a PCB 310 portion of a thin film antenna 300 according to an embodiment of the present invention. In the embodiment of FIG. 4a, the metal wire is welded to the PCB 310 on the outside, whereas in the embodiment of FIG. 4b, the weld 320 between the metal wire and the PCB 310 is not exposed to the outside around (especially the top surface of) the PCB 310. To maximize the durability and service life of the RFID tag assembly in accordance with the harsh usage environment of the present invention, the RFID tag assembly is electrically connected to a conductive radiation medium in the form of a wire, rather than using a ceramic type including a PCB, as in a typical RFID tag. The metal wires connected to both sides of the PCB 310 can maintain the structure of the RFID tag assembly even in the event of an external impact or drop, and can withstand high temperature and high pressure environments during special packaging or assembly. The metal wires can be surface-treated to make them easier to weld, and metals (e.g., copper) of various radii can be selected for the metal wires. A small PCB block 310 can be selected as a medium for electrically connecting metal wires to the IC chip 360. To further protect the IC chip 360 from the external environment, the PCB 310 can be configured with an undercut 380 to accommodate the PCB 310 and allow electrical bonding operations therein, and then epoxy resin molding is used to protect the IC chip 360 from exposure to the external environment.

[0031] In the embodiment shown in FIG. 4a, the length of the metal wire is selected based on the center frequency of the RFID tag assembly 200. The metal wire is connected to the PCB 310 by welding it to both the upper left and right sides of the PCB 310. The IC chip 360, installed in the undercut 380, is connected to the external weld 320 via a through-hole 340 in the PCB 310. The weld 320, which electrically connects the IC chip 360 to the metal wire, protrudes from the surface of the PCB 310, which can cause drawbacks when packaging with insulating tape or when using a thin PCB. Therefore, in the embodiment shown in FIG. 4b, the originally protruding weld 320 is accommodated around the periphery of the PCB 310, thereby preventing the weld from protruding outside the periphery of the PCB. In certain usage scenarios, accommodating the weld 320 around the periphery of the PCB 310 can disperse pressure that would otherwise be concentrated around the protruding portion 320 during, for example, the final packaging process or high-pressure application, thereby reducing the risk of damage.

[0032] FIG. 5a shows the change in the real and imaginary components of the input impedance with frequency when the end of the conductive radiating medium 400 according to the embodiment of the present invention is cut (i.e., the configuration corresponding to FIG. 2c), and FIG. 5b shows the change in the real and imaginary components of the input impedance with frequency when the end of the conductive radiating medium 400 according to the embodiment of the present invention is short-circuited (i.e., the configuration corresponding to FIG. 2d). As can be seen from FIGS. 5a and 5b, the change in the input impedance with frequency does not change significantly depending on whether the end of the conductive radiating medium 400 is cut or short-circuited. That is, cutting or shorting the end of the conductive radiating medium 400 does not significantly affect the trend of the impedance change with frequency. In the structure in which the end of the conductive radiating medium 400 is cut as shown in FIG. 5a, the input impedance at the center frequency of 0.92 GHz is 22-j162Ω, while in the structure in which the end of the conductive radiating medium 400 is short-circuited as shown in FIG. 5b, the input impedance at the center frequency of 0.92 GHz is 17-j154Ω, showing no significant difference. Therefore, if other design variables are the same, the structure of cutting and shorting the ends of the conductive radiation medium 400 does not significantly change the input impedance or radiation gain of the RFID tag assembly 200, and can therefore be widely applied to the structure of cylindrical metal objects with various cross-sectional radii.

[0033] 6a shows a change in the distinguishable distance of RFID tag assembly 200 when an RFID reader is rotated 0°, 90°, and 180° relative to PCB 310 when an end of conductive radiating medium 400 according to an embodiment of the present invention is cut (i.e., the configuration corresponding to FIG. 2c ), and FIG. 6b shows a change in the distinguishable distance of RFID tag assembly 200 when an RFID reader is rotated 0°, 90°, and 180° relative to PCB 310 when an end of conductive radiating medium 400 according to an embodiment of the present invention is short-circuited (i.e., the configuration corresponding to FIG. 2d ). Here, reading RFID tag assembly 200 from the front of PCB 310 is defined as φ=0°, reading RFID tag assembly 200 from a direction rotated 90° relative to the front of PCB 310 is defined as φ=90°, and reading RFID tag assembly 200 from the back of PCB 310 (i.e., the direction shown in FIG. 2c or 2d ) is defined as φ=180°. Even if the end of the conductive radiation medium 400 is cut or shorted, when reading the RFID tag assembly 200 from the front of the PCB 310, the tag identification distance is approximately 7 m or more at the reader's standard power, showing excellent readability performance, while when φ=90° and φ=180°, the tag identification distance decreases to 5 m and 3 m, respectively.

[0034] The conductive radiation medium 400 and the thin film antenna 300 structure used in this embodiment of the present invention are electrically coupled at a constant distance T2, and the strongest electric field is formed in the gap 430 that separates the conductive radiation medium 400 into a first portion 410 and a second portion 420. This configuration optimizes tag identification distance performance. In the graphs shown in Figures 6a and 6b, the identification distance of the RFID tag assembly changes with the rotation angle, but the RFID tag assembly can be identified even when the rear surface is φ=180°. In actual application environments, tag identification performance does not change sensitively depending on the rotation angle of the cylindrical metal object.

[0035] Furthermore, when the metal wiring length in the thin film antenna 300, the design variables of the conductive radiation medium 400, and the gap distance T2 between the thin film antenna 300 and the conductive radiation medium 400 remain unchanged, the tag readability performance remains almost unchanged when the end of the conductive radiation medium is cut or short-circuited. Due to this characteristic, even if the radius of the cylindrical metal object changes, cutting or shorting the end of the conductive radiation medium does not have a significant effect on the tag readability, so the same RFID tag assembly structure can be widely applied to cylindrical metal objects of various radii.

[0036] FIG. 7 shows the radiation pattern of an RFID tag assembly in the axial plane of a cylindrical metal object according to an embodiment of the present invention. To compare the performance of RFID tag assemblies 200 in which the end of the conductive radiation medium is cut or shorted at a center frequency of 920 MHz in the UHF frequency band, the radiation patterns of the RFID tag assemblies with the cut end and the short end are shown together on a unified coordinate system. Conventional UHF frequency band RFID tag assemblies concentrate their radiation gain in a specific direction depending on the shape of the ground surface and the attachment position, resulting in variations in the antenna directivity and identification performance of the RFID tag assembly depending on the rotation angle during identification. The present invention reduces the variation in recognition performance in the horizontal plane (i.e., circumferential direction) of a cylindrical metal object due to the rotation angle, thereby enabling easy recognition in actual application environments without the need to precisely control the attachment direction and angle of the tag assembly. In particular, the axial radiation pattern of the cylindrical metal piece does not change significantly when the end of the conductive radiation medium 400 is cut or shorted, and the two cases show almost similar performance, and the axial discrimination performance of the cylindrical metal piece is slightly better when the end of the conductive radiation medium 400 is cut than when the end of the conductive radiation medium 400 is shorted.

[0037] From this, the RFID tag assembly 200 of the present invention, in which the conductive radiation medium 400 is divided into a first portion 410 and a second portion 420 by the gap 430 and the conductive radiation medium 400 and the thin film antenna 300 are electrically coupled at a constant distance T2, exhibits the characteristic that its identification performance does not change sensitively depending on the identification angle when surrounding a cylindrical metal object.

[0038] An object of the present invention is to provide an RFID tag assembly with improved durability and to mitigate changes in tag identification performance caused by differences in the identification direction of the RFID tag assembly. Because cylindrical metal equipment requires multiple attachments, movements, installations, and identifications during rental, use, and return, matching the orientation of the RFID tag assembly with the polarization direction of the reader antenna to read tags in the optimal direction is difficult to achieve at construction sites or requires excessive management costs, reducing management efficiency and convenience. Therefore, the identification performance of the RFID tag assembly is not sensitive to changes in the orientation of the cylindrical metal equipment, and the omnidirectional identification performance of the RFID tag assembly of the present invention improves usability and flexibility.

[0039] Therefore, the conductive radiation medium of the RFID tag assembly of the present invention surrounds the cylindrical metal substrate at a certain distance. Alternatively, the conductive radiation medium of the RFID tag assembly may be divided into a first portion and a second portion by a gap, and the ends of the conductive radiation medium may be cut off when surrounding the cylindrical metal substrate. The metal wire of the thin film antenna is disposed above the first and second portions of the conductive radiation medium, and the thin film antenna is electrically coupled to the conductive radiation medium at a certain distance. The metal wire itself can increase the durability of the structure against external impacts, drops, vibrations, waterproofing, etc.

[0040] Furthermore, the electrically coupled thin film antenna and conductive radiating medium are packaged in a resin material, ultimately surrounding the cylindrical metal object. Hard materials such as plastic are not suitable for use as packaging materials because they may crack or break when impacted or dropped. In the present invention, the conductive radiating medium and thin film antenna are installed and sealed inside the resin material, which solves the problems of waterproofing and vibration isolation and relatively increases the durability of the RFID tag assembly in harsh construction environments.

[0041] Furthermore, the present invention achieves impedance matching by controlling the impedance of the conductive radiation medium and the thin film antenna of the RFID tag assembly, and can control each design variable of the resonant frequency, making it applicable to devices made of various materials, and its identifiable performance is not sensitive to changes in the attachment position. This coupling configuration makes the identifiable performance of the RFID tag assembly insensitive to specific design variables, installation, or manufacturing errors, thereby improving the yield of products in mass production.

[0042] Several exemplary embodiments have been described above. However, it should be understood that various modifications can be made to the above-described exemplary embodiments without departing from the spirit and scope of the present invention. For example, suitable results can also be achieved if the described techniques are performed in a different order, and / or if the components in the described systems, architectures, devices, or circuits are combined in a different manner, and / or if other components or their equivalents are substituted or supplemented, and therefore these modified other embodiments also fall within the scope of protection of the claims.

Claims

1. an electrically conductive radiation medium having a first portion and a second portion, with a gap between the first portion and the second portion; a thin film antenna including a printed wiring board and metal wires extending in different directions from both sides of the printed wiring board; an insulating attachment separating the conductive radiating medium and the thin film antenna.

2. 2. The radio frequency identification tag assembly of claim 1, wherein the thin film antenna is positioned so that the printed wiring board is aligned with the gap.

3. 2. The radio frequency identification tag assembly of claim 1, wherein the metal wire extends above each of the first and second portions of the conductive radiating medium.

4. 2. The radio frequency identification tag assembly of claim 1, wherein impedance matching between the thin film antenna and the conductive radiation medium is achieved by adjusting the lengths of metal wires on both sides of the printed wiring board.

5. 2. The radio frequency identification tag assembly of claim 1, wherein the thin film antenna is angled in a plane parallel to the conductive radiating medium relative to the direction in which the gap extends.

6. 2. The radio frequency identification tag assembly of claim 1, wherein the thin film antenna is attached to the insulating attachment, and the insulating attachment is attached to the conductive radiating medium.

7. 7. The radio frequency identification tag assembly of claim 6, wherein the shape of the insulating attachment is larger than the shape of the thin film antenna.

8. 2. The radio frequency identification tag assembly according to claim 1, further comprising an undercut groove for mounting an IC chip in said printed wiring board.

9. 9. The radio frequency identification tag assembly of claim 8, wherein the weld between the IC chip and the metal wire is above the top surface of the printed wiring board.

10. 9. The radio frequency identification tag assembly of claim 8, wherein the printed wiring board further includes a groove for accommodating a welded portion between the IC chip and the metal wire.

11. 2. The radio frequency identification tag assembly of claim 1, further comprising a bottom insulating layer and a top insulating layer, wherein the conductive radiation medium, the thin film antenna, and the insulative attachment are encapsulated between the bottom insulating layer and the top insulating layer.

12. 12. The radio frequency identification tag assembly of claim 11, wherein the material of the bottom insulating layer and the top insulating layer is the same as the material of the insulating attachment.

13. 12. The radio frequency identification tag assembly of claim 11, wherein the bottom insulating layer and the top insulating layer are integrally molded.

14. An object to be identified, characterized in that it has a radio frequency identification tag assembly according to any one of claims 1 to 13 on the outside.

15. The object to be identified according to claim 14, wherein the object to be identified has a curved three-dimensional structure, and the radio frequency identification tag assembly surrounds the curved three-dimensional structure.

16. The object to be identified according to claim 15, characterized in that when the radio frequency identification tag assembly surrounds the object to be identified in a direction extending along the gap, the first part and / or the second part surround at least a portion of the cylindrical part of the object to be identified along a circumferential direction.

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