RFID tag element and tool having RFID tag element

Abstract

To minimize a deviation between a forward radiation gain and a backward radiation gain, where an RFID tag element itself has a ground plane.SOLUTION: An RFID tag element 100 includes a substrate 110, a first through hole 170A provided at one end of the RFID tag element 100 in the substrate, a second through hole 170B provided at the other end, a foundation layer 120 located at a bottom part of the substrate and having one end close to one end of the RFID tag element 100 and the other end close to the other end of the RFID tag element 100, an intermediate layer 130 which is located between the top part and the bottom part of the substrate, and has one end electrically connected to one end of the foundation layer 120 through the first through hole, and the other end extending toward the other end of the RFID tag element 100, and an uppermost layer which is located at the top part of the substrate, and has the other end electrically connected to the other end of the foundation layer 120 through the second through hole 170B, and one end separated from the first through hole 170A.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

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

[0002] With the development of sensors with various frequency bands and low-power Bluetooth technology, RFID technology has been widely applied in many industries. In static environments, issues of RFID tag sensitivity and identification range, as well as polarization mismatch between the RFID reader antenna and the items being identified, are becoming increasingly prominent. In particular, when managing inventory in small tool warehouses or performing bulk identification at gates, tools are randomly arranged, making it difficult to ensure that RFID-tagged tools maintain a fixed position or ensure that the distance between the tag and the reader is roughly consistent. Multiple items to be identified may be in random positions and cannot be uniformly positioned. When items made of different materials are placed adjacent to each other, the center frequency of the RFID tag may shift. Furthermore, depending on the rotation direction of the item being identified, the orientation and polarization direction of the attached RFID tag may not match, thereby limiting the tag's maximum induction distance.

[0003] When an RFID tag is attached to an object with a symmetrical structure or a cylindrical shape (for example, small tools, wood, furniture, etc.), it is difficult to directly confirm the installation position and orientation from the outside when inserting the tag element. Summary of the Invention [Means for solving the problem]

[0004] The present invention aims to overcome the above-mentioned problems in the prior art by providing a new RFID tag design in which the RFID tag element itself has a ground plane, minimizing the discrepancy between the forward radiation gain and the backward radiation gain, thereby improving the identification performance of bulk RFID tags even when used in an application environment where multiple identification targets are placed in any direction.

[0005] According to a first aspect of the present invention, there is provided an RFID tag element having one end and the other end along a longitudinal direction, the RFID tag element comprising: a substrate; a first through-hole provided in the substrate at one end of the RFID tag element; a second through-hole provided in the substrate at the other end of the RFID tag element; a base layer located at a bottom of the substrate, one end of which is close to one end of the RFID tag element and the other end of which is close to the other end of the RFID tag element; an intermediate layer located between the top and bottom of the substrate, one end of which is electrically connected to one end of the base layer through the first through-hole and the other end of which extends toward the other end of the RFID tag element; a top layer located at the top of the substrate, the other end of which is electrically connected to the other end of the base layer through the second through-hole and the one end of which is spaced apart from the first through-hole, with a gap; and a chip bonded to the top layer across the gap in the top layer, wherein the distance between the other end of the intermediate layer and the one end of the RFID tag element does not exceed the distance between the gap and the one end of the RFID tag element.

[0006] According to a second aspect of the present invention, there is provided an RFID tag element having one end and the other end along a longitudinal direction, the RFID tag element comprising: a substrate; a first through-hole provided in the substrate at one end of the RFID tag element; a second through-hole provided in the substrate at the other end of the RFID tag element; a base layer located at the bottom of the substrate, one end of which is close to one end of the RFID tag element and the other end of which is close to the other end of the RFID tag element; and a base layer located between the top and bottom of the substrate, one end of which is electrically connected to one end of the base layer through the first through-hole. an intermediate layer having a gap between the substrate and the base layer, the other end of which is electrically connected to the other end of the base layer through the second through hole; a chip bonded to the intermediate layer across the gap in the intermediate layer; and a top layer located on top of the substrate, one end of which is spaced apart from one end of the RFID tag element and the other end of which is spaced apart from the other end of the RFID tag element, the top layer having a machine hole that at least partially overlaps the gap in the intermediate layer and houses the chip within the machine hole.

[0007] According to a third aspect of the present invention, there is provided a tool having a cavity configured to accommodate an RFID tag element as described in any one of the preceding claims, the RFID tag element being arranged in the cavity along a longitudinal direction.

[0008] Other features and aspects will become apparent from the following detailed description, drawings, and claims. [Brief explanation of the drawings]

[0009] [Figure 1a] 1A and 1B are a side view and an exploded view of an RFID tag element according to an embodiment of the present invention. [Figure 1b] 1A and 1B are a side view and an exploded view of an RFID tag element according to an embodiment of the present invention. [Figure 2a] 10A and 10B are a side view and an exploded view of an RFID tag element according to another embodiment of the present invention. [Figure 2b] 10A and 10B are a side view and an exploded view of an RFID tag element according to another embodiment of the present invention. [Figure 3a] 10 shows impedance characteristics of an RFID tag element according to one embodiment of the present invention and an RFID tag element according to another embodiment of the present invention when various parameters are set based on the 920 MHz center frequency band of the UFH frequency band. [Figure 3b] 10 shows impedance characteristics of an RFID tag element according to one embodiment of the present invention and an RFID tag element according to another embodiment of the present invention when various parameters are set based on the 920 MHz center frequency band of the UFH frequency band. [Figure 3c] FIG. 10 is a process diagram for fine-tuning the center frequency of an RFID tag element by adjusting the length D1 of the top layer. [Figure 4a] 1 is a schematic diagram showing RFID tag elements of a first embodiment and a second embodiment of the present invention attached on a planar tool surface and in tool surface grooves. [Figure 4b] 1 is a schematic diagram showing RFID tag elements of a first embodiment and a second embodiment of the present invention attached on a planar tool surface and in tool surface grooves. [Figure 4c] 10 is a schematic diagram of a third embodiment of the present invention in which RFID tag elements are attached to a tool surface in opposite directions. [Figure 5a] 10 shows the radiation patterns in the cross-sectional direction of the RFID tag elements of the first and second embodiments of the present invention when the RFID tag elements are attached on a planar tool surface and in a tool surface groove. [Figure 5b] 10 is a diagram showing radiation patterns in a cross-sectional direction when an RFID tag element according to a second embodiment of the present invention is attached to tools with different widths and grooves with the same depth. FIG. [Figure 6] FIG. 10 is a diagram showing the change in tag discernible distance performance when a tool is rotated about its longitudinal axis when an RFID tag element of a third embodiment of the present invention is attached to the tool. [Figure 7] FIG. 10 is a schematic diagram showing an RFID tag element according to a fourth embodiment of the present invention provided in a tool. [Figure 8]10A and 10B are diagrams showing radiation patterns in the cross-sectional direction of the RFID tag element when the RFID tag element of the fourth embodiment of the present invention is inserted into a tool at multiple angles. [Figure 9] FIG. 10 is a diagram showing changes in tag identification distance performance with changes in angle when the RFID tag element of the fourth embodiment of the present invention is inserted into a tool at multiple angles. DETAILED DESCRIPTION OF THE INVENTION

[0010] The drawings are for illustrative purposes and are not to be considered to scale unless specifically stated to be to scale. The drawings are schematic diagrams to aid understanding and may not include all aspects or information compared to realistic representations.

[0011] In the drawings, similar components and / or features may be labeled with the same reference numeral, and various components of the same type may be distinguished by a letter following the reference numeral. When only a preceding reference numeral is used in the specification, the description applies to any similar component having the same preceding reference numeral.

[0012] 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.

[0013] 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 embodied in other ways than those described herein, and those skilled in the art may make similar extensions without departing from the scope of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] In this application, all embodiments and preferred embodiments, all technical features and preferred features described in this specification can be combined with each other to form new technical solutions, unless otherwise specified.

[0018] In 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.

[0019] As RFID tag usage expands across various industries, not only is the readability and identification distance of RFID tags in static environments crucial, but so is the versatility of RFID tags to adapt to various environmental and variance factors in actual applications. In particular, the unique appearance characteristics of objects to which RFID tags are attached make it difficult to intuitively identify their location. Furthermore, when RFID tags are inserted into specific spaces within the object to protect them from the external environment and ensure their stability, it is difficult to achieve optimal identification between the RFID reader antenna and the identified object. During the storage, transportation, or packaging of objects, especially in large warehouses, RFID tags may be placed in any orientation or on shelves at different heights. In this case, the tag's omnidirectional identification capability is key to ensuring the stability of the RFID system. Therefore, if RFID tags are mounted high on conductive shelves in a large warehouse, and the radiation gains at the front, rear, and sides are similar, using a ground-based RFID reader can maintain high identification rates and flexibility. The technical solution provided by the present invention can reduce radio wave scattering, jamming and interference when simultaneously identifying multiple objects passing through a gate, and significantly improve the identification performance of object tags in any direction or rotation.

[0020] The key advantage of ultra-high frequency (UHF) passive RFID tag technology is its ability to simultaneously identify multiple tags remotely without contact, using a backscattering communication protocol. Due to the characteristics of ultra-high frequency electromagnetic waves, the loss and dielectric constant of the tag-attached material have a significant impact on tag performance. The tag's spatial radiation gain pattern is not only influenced by its own design, but is also closely related to the object to which the tag is attached, its position, the polarization matching of the reader antenna, and the surrounding electromagnetic environment. When a tag is attached to a dielectric material such as plastic, glass, or high-dielectric ceramics, a dipole-shaped tag inserted into these materials forms a uniform radiation pattern around the insertion axis. While the specific radiation gain is affected by the material's loss and dielectric constant, the tag's spatial omnidirectional radiation pattern remains nearly constant as long as the material's symmetry is maintained.

[0021] In practical applications, if the tag is attached to a dielectric material and the tag's radiation gain needs to be concentrated in a specific direction (usually a surface), the tag may be provided with a grounding function or coated with an additional conductive medium to maintain the appropriate spacing.

[0022] When an RFID tag must be attached to a metal surface, it is usually necessary to perform complex impedance matching with the tag chip and attach a ground plane to the tag. While this method allows the tag's ground plane and the metal conductive medium to be used as a convenient ground plane, it can reduce the tag's input impedance bandwidth, and the tag's electrical characteristics can be significantly affected by the size and attachment position of the conductive medium. Furthermore, the asymmetry of the ground plane can cause significant variations in the tag's radiation pattern. When the size of the metal attachment object is relatively large, the tag's radiation gain tends to be concentrated at the top of the ground plane. When a tag is attached to a large conductive object, the difference in radiation gain between the front (facing the reader) and back of the tag is significant compared to the tag's size, and this difference is particularly noticeable between the front of the label and the back of the conductive object.

[0023] To improve this polarized radiation gain pattern, one method is to cut or process the metal material itself into a closed-loop groove as part of the tag antenna, but this method is not widely used because the radiation gain is relatively low, and in practical applications it is difficult to process metal objects arbitrarily, and the final packaging process, including chip molding, is difficult.

[0024] To achieve the maximum read distance when an RFID tag is identified by an RFID reader, the RFID tag's cross-sectional area (RCS) must ensure that its surface is oriented as close as possible to the reader antenna's radiation area. Most RFID tags designed for metal surfaces aim to maximize radiation gain in a direction perpendicular to the metal surface. However, if the tag and reader antenna are not aligned at the same height or the tag is attached at an oblique angle, the RCS decreases sharply and the receiving sensitivity drops significantly. In applications such as managing high-rise shelves in logistics warehouses and preventing product loss on shelves, a wider radiation gain angle is important in addition to the tag's static identification performance. Furthermore, when multiple tagged objects are arranged in random directions rather than with a uniform surface orientation, maintaining a uniform radiation pattern on a specific plane of the tag is crucial for improving the practicality of RFID systems.

[0025] When the polarization of the RFID reader antenna and the tag attached to the metal surface are mismatched and the tag's radiation gain is biased to a specific direction, the tag's identification rate varies significantly depending on the identification angle of the reader antenna, which results in a significant drop in the batch identification rate when multiple objects to be identified are loaded in random directions.

[0026] Therefore, there is a need for an RFID tag element that can maintain tag performance whether attached to a conductive object or a dielectric object, and that can maintain the tag's radiation gain and a uniform radiation pattern in a particular direction when attached to conductive and dielectric objects in any orientation, thereby increasing the usability of RFID tags in practical environments.

[0027] 1a and 1b are a side view and an exploded view of an RFID tag element 100 according to one embodiment of the present invention. The RFID tag element 100 has one end 100A and the other end 100B along the longitudinal direction (the x-axis shown in FIG. 1a). The RFID tag element 100 includes a substrate 110, a base layer 120, an intermediate layer 130, and a top layer 140. The substrate 110 may be made of a dielectric material, while the base layer 120, the intermediate layer 130, and the top layer 140 may be made of a conductive material such as copper and may be fabricated in the form of very thin sheets. The base layer 120 is located at the bottom of the substrate 110 and extends along the longitudinal direction of the RFID tag element 100. One end 120A of the base layer 120 is close to the one end 100A of the RFID tag element 100, and the other end 120B is close to the other end 100B of the RFID tag element 100. The middle layer 130 is located between the top and bottom of the substrate 110, with one end 130A of the middle layer 130 being close to the end 100A of the RFID tag element 100 and the other end 130B extending toward the other end 100B of the RFID tag element 100. The top layer 140 is located on top of the substrate 110, with the other end 140B of the top layer 140 being close to the other end 100B of the RFID tag element 100 and the one end 140A of the top layer 140 extending toward but not reaching the end 100A of the RFID tag element 100. The top layer 140 and the intermediate layer 130 at least partially overlap in the vertical direction (y-axis in FIG. 1a), that is, a projection of the top layer 140 on the base layer 120 and a projection of the intermediate layer 130 on the base layer 120 at least partially overlap in the vertical direction (y-axis in FIG. 1a). The top layer 140 further has a gap 150, and the chip 160 of the RFID tag element 100 is bonded to the top layer 140 across the gap 150. Preferably, the chip 160 is covered with a protective layer such as epoxy resin.

[0028] The distance D1 between the other end 130B of the intermediate layer 130 and the one end 100A of the RFID tag element 100 does not exceed the distance D2 between the gap 150 and the one end 100A of the RFID tag element 100.

[0029] The RFID tag element 100 further includes a first through-hole 170A disposed in the substrate 110 at one end 100A of the RFID tag element 100, and a second through-hole 170B disposed in the substrate 110 at the other end 100B of the RFID tag element 100. A perforated structure is manufactured by machining, and then a conductive material (e.g., copper) can be applied to the inner surface of the perforated structure to allow electrical continuity between different objects that are conductively connected to the conductive material, thereby forming the through-hole. The first through-hole 170A connects one end 130A of the middle layer 130 to one end 120A of the base layer 120, and the second through-hole 170B connects the other end 140B of the top layer 140 to the other end 120B of the base layer 120.

[0030] 1a and 1b, the base layer 120 functions as a ground layer for the RFID tag element 100. There is a distance H1 between the base layer 120 and the intermediate layer 130 (e.g., through the first through-hole 170A), and a distance H2 between the intermediate layer 130 and the top layer 140. There is a distance H1+H2 between the base layer 120 and the top layer 140 (e.g., through the second through-hole 170B). The RFID tag element 100 having such a three-dimensional structure can effectively reduce the area of ​​the tag element in a limited space, and by coupling the top layer 140 and the intermediate layer 130 at a short distance so as to be disconnected rather than short-circuited, the operating impedance bandwidth of the RFID tag element 100 can be improved and adjustable.

[0031] By changing various design variables of the RFID tag element 100, it is possible to adjust the center frequency, the distance H1 between the base layer 120 and the intermediate layer 130, the distance H2 between the intermediate layer 130 and the top layer 140, the position of the other end 130B of the intermediate layer 130, the length T1 of the top layer 140, the position of the chip 160 on the top layer 140 (here represented by the distance off1 between the chip 160 and the other end 140B of the top layer 140), etc. In the assembled state, it is difficult to adjust the distance H1 between the base layer 120 and the intermediate layer 130, the distance H2 between the intermediate layer 130 and the top layer 140, and the position of the other end 130B of the intermediate layer 130. On the other hand, if the distance D1 between the other end 130B of the intermediate layer 130 and the one end 100A of the RFID tag element 100 exceeds the distance D2 between the gap 150 and the one end 100A of the RFID tag element 100, even a very small change in other variables will have a significant effect on the center frequency of the RFID tag element 100. Therefore, in this embodiment, the distance D1 between the other end 130B of the intermediate layer 130 and the one end 100A of the RFID tag element 100 is preset so as not to exceed the distance D2 between the gap 150 and the one end 100A of the RFID tag element 100. In FIG. 1a, the other end 130B of the intermediate layer 130 and the side of the gap 150 closer to the one end 100A of the RFID tag element 100 are basically aligned. Then, by predetermining the distances H1 and H2 and fine-tuning the position off1 of the chip 160 and the length T1 of the top layer 140, fine adjustment of the center frequency and impedance matching of the RFID tag element 100 is achieved.

[0032] Furthermore, since the width W1 of the RFID tag element 100 is designed to be very narrow compared to its length, the base layer 120 and the connected through-holes 170A and 170B on both sides realize equivalent capacitance through short-range coupling between the top layer 140 and the middle layer 130, making it easy to achieve complex impedance matching of the RFID tag element chip 160. Furthermore, by providing a ground plane to the RFID tag element 100 itself, the RFID tag element 100 can be attached to a metal surface or inserted into a metal environment or various dielectric materials.

[0033] 2a and 2b are a side view and an exploded view of an RFID tag element 200 according to another embodiment of the present invention. The RFID tag element 200 has one end 200A and the other end 200B along the longitudinal direction (x-axis). The RFID tag element 200 includes a substrate 210, a base layer 220, a middle layer 230, and a top layer 240. The substrate 210 may be made of a dielectric material, while the base layer 220, the middle layer 230, and the top layer 240 may be made of a conductive material such as copper and may be fabricated in the form of very thin sheets. The base layer 220 is located at the bottom of the substrate 210 and extends in the x-axis direction. One end 220A of the base layer 220 is close to the one end 200A of the RFID tag element 200, and the other end 220B is close to the other end 200B of the RFID tag element 200. The intermediate layer 230 is located between the top and bottom of the substrate 210, with one end 230A of the intermediate layer 230 being close to one end 200A of the RFID tag element 200 and the other end 230B being close to the other end 200B of the RFID tag element 200. The intermediate layer 230 has a gap 250. The gap 250 is located at the middle position of the intermediate layer 230 in the x-axis direction. The chip 260 of the RFID tag element 200 is bonded to the intermediate layer 230 across the gap 250, and a protective layer may be covered on the chip 260. The top layer 240 is located on top of the substrate 210, with one end 240A of the top layer 240 being spaced apart from the one end 200A of the RFID tag element 200 and the other end 240B being spaced apart from the other end 200B of the RFID tag element 200. The top layer 240 has machine holes 280 that at least partially overlap the gaps 250 of the intermediate layer 230 in the vertical direction (y-axis in FIG. 2a), and the machine holes 280 can accommodate the chips 260 and any protective layers for the chips 260. The machine holes 280 define a cavity structure in the top layer 240, which makes it easier to mount the chips 260 on the intermediate layer 230 and can also serve to avoid and protect the chips 260. Preferably, the top layer 240 is symmetrical about a center line c1 in the x-axis direction with respect to the RFID tag element 200. The top layer 240 and the intermediate layer 230 at least partially overlap in the vertical direction (y-axis in FIG. 2a).

[0034] The RFID tag element 200 further includes a first through-hole 270A provided at one end 200A of the RFID tag element 200 within the substrate 210, and a second through-hole 270B provided at the other end 200B of the RFID tag element 200. The first through-hole 270A connects one end 230A of the intermediate layer 230 to one end 220A of the base layer 220, and the second through-hole 270B connects the other end 230B of the intermediate layer 230 to the other end 220B of the base layer 220.

[0035] 2a and 2b, the base layer 220 functions as a ground layer for the RFID tag element 200. There is a gap H3 between the base layer 220 and the middle layer 230, and a gap H4 between the middle layer 230 and the top layer 240. The length D1 of the top layer 240 along the x-axis direction can be a design variable, and fine-tuning of the RFID tag element 200 can be achieved by adjusting the design variable D1 according to changes in the material and installation depth of the installation object. Increasing the length D1 of the top layer 240 increases the equivalent capacitance between the top layer 240 and the middle layer 230, thereby reducing the center frequency of the RFID tag element 200. Conversely, decreasing the length D1 decreases the equivalent capacitance, thereby increasing the center frequency of the RFID tag element 200. Such a sheet structure of the top layer 240 can easily improve variations caused by changes in the ambient environment outside the RFID tag element 200 and changes in the installation environment, and can also reduce the protrusion of the top of the RFID tag element 200, reducing friction during installation and improving convenience. The structure shown in this embodiment can be a technical solution that can efficiently and easily achieve impedance matching of a chip in the UHF band using a conventional PCB manufacturing process.

[0036] 3a and 3b show impedance characteristics of the RFID tag device 100 according to one embodiment of the present invention and the RFID tag device 200 according to another embodiment of the present invention when various parameters are set based on the 920 MHz center frequency band of the UFH frequency band. As shown in Fig. 3a and 3b, the imaginary part of the input impedance of the RFID tag device 100 is set to a relatively low value of 0.23 + j137.57 Ω (f0 = 920 MHz), while the imaginary part of the input impedance of the RFID tag device 200 is set to a relatively high value of 7.48 + j212.47 Ω (f0 = 920 MHz). The most important design variables of the RFID tag element 100 / 200 of this patent are the distance between the through holes on both sides of the RFID tag element (the distance between through holes 170A and 170B, and the distance between through holes 270A and 270B, hereinafter referred to as the "through hole spacing") and the spacing between each layer in the multi-layer RFID tag element (the spacing between H1 and H2 in RFID tag element 100 and the spacing between H3 and H4 in RFID tag element 200, hereinafter referred to as the "layer spacing"). The through hole spacing is the most important design variable for adjusting the inductance component of the RFID tag element, and the layer spacing is the most important design variable for adjusting the capacitance of the RFID tag element. However, these design variables, namely the thickness of the RFID tag element, the thickness of each layer, and the length of each layer passing through the through holes, cannot be significantly changed once the manufacturing process of the RFID tag element has been determined and must be fine-tuned by other means.

[0037] The electrical parameters of the RFID tag element 100 in FIGS. 1a and 1b can be adjusted by adjusting the length T1 of the top layer 140 and the bonding position off1 of the chip 160. The center frequency of the RFID tag element 200 in FIGS. 2a and 2b can be fine-tuned by adjusting the length D1 of the top layer 240. FIG. 3c schematically illustrates the process of fine-tuning the center frequency of the RFID tag element 200 by adjusting the length D1 of the top layer 240. Fine-tuning the design variables of the RFID tag element in this manner provides a convenient means for easily adjusting the frequency to accommodate variations and tolerances in the materials of various attachment objects. As an example, the input impedances of the RFID tag elements 100 and 200 of this patent are designed to be 0.23 + j137.57 Ω and 7.48 + j212.47 Ω, respectively, based on 920 MHz. This means that the imaginary input impedance, which would otherwise need to be redesigned as the chip changes, can be adjusted by adjusting the area of ​​the distribution, thereby improving the availability of RFID tag elements.

[0038] Generally, an RFID tag attached to a metal surface has a ground plane. If the ground plane is short-circuited to the metal surface, the metal surface itself becomes the common ground plane for the RFID tag. Therefore, if the area of ​​the attached metal object is relatively large, the radiation gain and spatial radiation pattern of the RFID tag will be significantly affected as the attachment position changes. RFID tag attached to a metal object has a significant difference in radiation gain pattern between its front and back surfaces. To improve aesthetics and reduce the risk of damage to the RFID tag in practical applications, RFID tag is commonly embedded in a groove on the metal surface. As the groove depth increases, the radiation efficiency of the tag decreases, reducing the spatial radiation gain and further affecting its identification distance.

[0039] 4a is a schematic diagram of an RFID tag element 100 of a first embodiment of the present invention being attached to a planar tool 400. Here, the RFID tag element 100 has a protruding tip covered with a protective layer, and the tool 400 is made of a narrow and long metal piece. The planar surface 401 of the tool 400 does not have any cavity or groove for accommodating the RFID tag element 100.

[0040] Fig. 4b shows an RFID tag element 100 according to a second embodiment of the present invention attached to the surface of a tool 410, and Fig. 4c shows an RFID tag element 100 according to a third embodiment of the present invention attached in the opposite direction to the surface of the tool 410. In Figs. 4b-4c, the RFID tag element 100 has a protruding mold-protected tip, and the tool 410 is made of a narrow, long metal. A groove 411 for accommodating the RFID tag element 100 is provided on the surface of the tool 410.

[0041] The tool may be made of metal or other materials, such as dielectric materials, plastic, or wood. For ease of testing and simulation experiments, a wrench is shown as a representative tool, but tools made of other materials are equally applicable. FIGS. 4a to 4c show the RFID tag element 100 of FIGS. 1a to 1b installed on the tool 400 and tool 410. Those skilled in the art should understand that the RFID tag element 200 of FIGS. 2a to 2b can also be installed on the tool 400 and tool 410 as shown in FIGS. 4a to 4c. When the RFID tag element is installed in the reverse direction, as shown in FIG. 4c, the chip portion is located in a groove in the metal surface and is not exposed to the outside, effectively reducing the risk of damage to the RFID tag element due to environmental factors. When selecting the RFID tag element 100, it is preferable that the chip 160 protrudes a certain height from the top layer 140. This increases the thickness of the protective layer, forming a certain distance between the surface of the groove 411 and the top layer of the RFID tag element 100, and can form an additional equivalent capacitance, which can be used as an additional parameter to adjust the center frequency of the RFID tag element 100. By adjusting the distance between the RFID tag element 100 and the surface of the groove 411 (for example, by changing the thickness of the protective layer), the center frequency of the RFID tag element 100 can be adjusted.

[0042] Compared with the prior art, the RFID tag element of the present invention can significantly reduce the difference between the forward radiation gain and the backward radiation gain under different attachment conditions, whether attached to a metal object or to materials with different dielectric constants.

[0043] FIG. 5a shows the cross-sectional radiation patterns of the RFID tag element 100 of the first and second embodiments of the present invention when the RFID tag element 100 is attached to the flat surface 401 of the tool 400 (FIG. 4a) and in a groove 411 on the surface of the tool 410 (FIG. 4b). By way of example, the groove 411 is formed to have a depth of 0.4 mm to 0.8 mm, but the present invention is not limited to this. Here, the cross section refers to a plane perpendicular to the longitudinal direction, i.e., a plane defined by the y-axis and z-axis in FIG. 4a. With a reference frequency of 920 MHz, the RFID tag element 100 exhibits a radiation gain of 2.2 dBi on the front surface (+y direction) and 1.3 dBi on the back surface (-y direction) when attached to the front surface 401 and when embedded in the groove 411. In the side direction, the side radiation gain of the RFID tag element 100 attached to the front surface 401 is 1.6 dBi, and that of the RFID tag element 100 embedded in the groove 411 is 1.5 dBi. Although the back radiation gain is 0.9 dBi lower than the front radiation gain, this difference is significantly reduced compared to tags attached to conventional metal surfaces.

[0044] Figure 5b shows cross-sectional radiation patterns of RFID tag elements 100 according to a second embodiment of the present invention when they are attached to grooves of the same depth on tools of different widths. RFID tag elements with a ground plane typically exhibit a tendency for the front radiation gain to increase and the back radiation gain to decrease as the metal area of ​​the attachment tool increases. Figure 5b shows radiation pattern data for tool widths of W, 2W, and 3W (where W is the reference width). The difference in the front radiation gain for different widths is 0.1 dBi to 0.3 dBi, and the difference in the back radiation gain is 0.3 dBi to 0.5 dBi. Due to the deviation in radiation patterns caused by different tool widths, it is believed that the tool width does not significantly affect the readability and identification distance performance of RFID tag elements in actual application environments.

[0045] 6 shows the change in the readable identification distance performance of the RFID tag element 100 according to the third embodiment of the present invention when the RFID tag element 100 is attached to a tool 400 (FIG. 4c) and the tool 400 is rotated around its longitudinal axis (x-axis direction). As shown in the upper left corner of FIG. 6, the orientation of the tool 400 when the surface radiation direction of the RFID tag element 100 faces the RFID reader is defined as 0°, the orientation of the tool 400 when the surface radiation direction is perpendicular to the direction from the tool 400 to the RFID reader is defined as 90°, and the orientation of the tool 400 when the back radiation direction faces the RFID reader is defined as 180°. It can be seen that the maximum readable distance performance of the RFID tag element 100 is best when the tool 400 is at 0° relative to the RFID reader. When the orientation is rotated by 90°, the maximum distinguishable distance of the RFID tag element 100 decreases by 0.5 m, and when the tool 400 is rotated by 180° relative to the RFID reader, the maximum distinguishable distance of the RFID tag element 100 decreases by another 0.5 m, but this difference does not have much impact in a practical application environment.

[0046] For tools and furniture with different dielectric materials, RFID tag elements can be embedded in the dielectric material when managing assets using an RFID system. This embedded installation method not only protects RFID tag components from harsh environments but also improves the tool's appearance. However, RFID tag elements may have a specific directional radiation gain preference, making their orientation and position inside the tool difficult to intuitively determine. Therefore, when reading from the outside using an RFID reader, not all tools with embedded tags will face the reader. Therefore, uniform radiation gain characteristics of RFID tag elements are particularly important when identifying multiple tools in any orientation.

[0047] 7 is a schematic diagram of an RFID tag element 200 according to a fourth embodiment of the present invention, which is mounted in a tool 700. The tool 700 is made of a dielectric material. The RFID tag element 200 is first mounted in an intermediate case 710, and then the intermediate case 710 together with the RFID tag element 200 can be inserted into the tool 700.

[0048] FIG. 8 shows the radiation patterns in the cross-sectional direction of the RFID tag element 200 of the fourth embodiment when the RFID tag element 200 is inserted into the tool at various angles. The left side of FIG. 8 shows a bottom view of the tool 700 as seen from the viewing angle A shown in FIG. 7, where the angles between the plane on which the RFID tag element 200 is located (the plane defined by the x-axis and z-axis in FIG. 2b) and the reference horizontal plane of the tool are 0°, 45°, and 90°, respectively. When the RFID tag element 200 is inserted into the tool 700 at 0°, 45°, and 90°, respectively, the ground plane of the RFID tag element 200 faces the RFID reader from the front, inclined, and side, respectively. As shown on the right side of FIG. 8, the measurement results for the RFID tag element 200 inserted into the tool 700 at 0°, 45°, and 90° show that the spatial radiation gain is relatively high when inserted at 45°, but is still about 0.1 dBi lower than when inserted at 0° and 90°. The measurement results shown in Fig. 8 show that no significant radiation deviation occurs with changes in the insertion angle in a practical application environment.

[0049] FIG. 9 shows the change in the distinguishable distance performance of the RFID tag element 200 according to the fourth embodiment of the present invention when the RFID tag element 200 is inserted into the tool 700 at various angles, depending on the angle of the RFID tag element 200. The relative orientation of the RFID tag element 200 to the reference horizontal plane of the tool 700 in the figure remains unchanged, but by changing the insertion direction of the RFID tag element 200 within the tool 700, the RFID tag element 200 rotates around its vertical axis (the x-axis in FIG. 2a). When the RFID tag element is installed within the tool 700 at angles of 0°, 45°, or 90° relative to the reference horizontal plane of the tool 700, its maximum distinguishable distance performance does not change significantly. It can be seen that the RFID tag element proposed in this application has uniform radiation characteristics in various directions.

[0050] Although the RFID tag element 200 is shown in the description and drawings of FIGS. 7 to 9, an RFID tag element 100 as shown in FIGS. 1a to 1b may also be provided.

[0051] The present invention relates to a special RFID tag element that can improve the identification rate of an RFID tag element by minimizing the difference between the forward radiation gain and the backward radiation gain of the RFID tag element, thereby reducing the deviation from the identification distance of a tool to which the RFID tag element is attached in any direction or the identification distance when multiple tools are arranged in any direction.

[0052] The RFID tag element of the present invention forms a laminated structure with through-holes on both ends to reduce tag size, and controls the coupling capacitance with the ground plane of the underlying layer to adjust the complex impedance matching of the RFID tag element chip. This is achieved by connecting the top layer and middle layer to the ground plane of the underlying layer in an interdigital structure or by maintaining a constant gap. This structural design exposes the sensitive design variable that controls the RFID tag's center frequency, allowing the RFID tag's electrical performance to be easily adjusted in response to changes and errors in the attached object. Furthermore, the RFID tag element chip is recessed, creating a low profile, reducing the risk of damage from the external environment and improving aesthetics. In a multi-layer PCB structure, the gap between different layers is an important design variable for the RFID tag element's electrical performance and effective tag matching, providing a wide range of adjustment possibilities.

[0053] The technical solution of the present invention realizes complex impedance matching between the conductive medium and the tag chip, reduces the tag size, and provides the tag with a ground plane, making it widely applicable to objects with different dielectric constants, high-dielectric liquids in specific containers, and conductive materials.In particular, the structural features of this label are constructed using laminated PCB manufacturing technology commonly used in electronic circuits, realizing low-cost, precise, and standardized production of general-purpose tags.

[0054] 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 RFID tag element having one end and the other end along a longitudinal direction, A substrate; a first through hole provided in the substrate at one end of the RFID tag element; a second through hole provided in the substrate at the other end of the RFID tag element; a base layer located at the bottom of the substrate, one end of which is close to one end of the RFID tag element and the other end of which is close to the other end of the RFID tag element; an intermediate layer located between the top and bottom of the substrate, one end of which is electrically connected to one end of the base layer through the first through hole and the other end of which extends toward the other end of the RFID tag element; a top layer having a gap, the other end of which is electrically connected to the other end of the underlayer through the second through-hole and the other end of which is spaced apart from the first through-hole; a chip joined to the top layer across the gap in the top layer, The RFID tag element is characterized in that the distance between the other end of the intermediate layer and one end of the RFID tag element does not exceed the distance between the gap and one end of the RFID tag element.

2. The RFID tag element according to claim 1 , wherein the center frequency of the RFID tag element can be adjusted by adjusting the length of the top layer and / or the length of the intermediate layer.

3. 2. The RFID tag element according to claim 1, wherein the other end of the intermediate layer is aligned with the side of the gap that is closer to the one end of the top layer.

4. The RFID tag element according to claim 1 , wherein the projection of the intermediate layer onto the base layer at least partially overlaps the projection of the top layer onto the base layer.

5. An RFID tag element having one end and the other end along a longitudinal direction, A substrate; a first through hole provided in the substrate at one end of the RFID tag element; a second through hole provided in the substrate at the other end of the RFID tag element; a base layer located at the bottom of the substrate, one end of which is close to one end of the RFID tag element and the other end of which is close to the other end of the RFID tag element; an intermediate layer having a gap, the intermediate layer being located between the top and bottom of the substrate, one end of the intermediate layer being electrically connected to one end of the underlying layer through the first through-hole and the other end of the intermediate layer being electrically connected to the other end of the underlying layer through the second through-hole; a chip joined to the intermediate layer across the gap of the intermediate layer; a top layer located on top of the substrate, one end of which is spaced apart from one end of the RFID tag element and the other end of which is spaced apart from the other end of the RFID tag element, the top layer having a machine hole, the machine hole at least partially overlapping the gap of the intermediate layer, and the top layer accommodating the chip within the machine hole; An RFID tag element comprising:

6. The RFID tag element according to claim 5 , wherein the gap is located at a middle position of the intermediate layer in a direction from one end of the intermediate layer to the other end of the intermediate layer.

7. The RFID tag element according to claim 5 , wherein the projection of the top layer onto the base layer at least partially overlaps the projection of the intermediate layer onto the base layer.

8. The RFID tag element of claim 5 , wherein the top layer is symmetrical about a midline between one end and the other end of the RFID tag element.

9. The RFID tag element according to claim 5, wherein the center frequency of the RFID tag element can be adjusted by adjusting the length of the top layer.

10. A tool having a cavity configured to accommodate an RFID tag element according to any one of claims 1 to 9, wherein the RFID tag element is arranged in the cavity with its longitudinal direction parallel to an axial direction of the tool.

Images