An RFID tag antenna based on a flexible substrate and a spiral involute structure

Abstract

This invention relates to the field of radio frequency antenna technology and discloses an RFID tag antenna with a helical involute structure based on a flexible substrate. The antenna includes a flexible substrate and an antenna radiator disposed above the flexible substrate. The antenna radiator includes a loop antenna located at the center of the flexible substrate, used to cover the end of a cylinder. This RFID tag antenna with a helical involute structure based on a flexible substrate effectively solves the problem in the prior art where many identified objects have non-planar structures, and the demand for identifying cylindrical objects is increasing. Traditional planar antennas typically have a fixed planar radiation pattern. When attached to a cylinder, their radiated energy cannot simultaneously cover the end of the cylinder and the curved area of ​​its outer circumference, resulting in low identification success rate and blind spots when the reader approaches from a fixed direction.

Description

Technical Field

[0001] This invention relates to the field of radio frequency antenna technology, and more specifically to a CNC milling cutter. Background Technology

[0002] RFID technology, as a non-contact automatic identification technology, has been widely used in logistics tracking, asset management, and supply chain management. Among these technologies, the RFID tag antenna, as the core component for energy coupling and signal transmission between the tag and the reader, directly determines the tag's identification distance, stability, and applicable scenarios.

[0003] In existing technologies, many objects being identified have non-planar structures, and the demand for identifying cylindrical objects is increasing. The radiation pattern of traditional planar antennas is usually a fixed planar distribution. When attached to a cylinder, its radiation energy is difficult to cover the ends of the cylinder and the curved areas of the outer circumference at the same time, resulting in a low recognition success rate and the existence of recognition blind spots when the reader approaches from a fixed direction. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides an RFID tag antenna based on a flexible substrate with a spiral involute structure. This effectively solves the problem that in existing technologies, many identified objects have non-planar structures, and the demand for identifying cylindrical objects is increasing. Traditional planar antennas typically have a fixed planar radiation pattern. When attached to a cylinder, their radiation energy cannot simultaneously cover the ends and curved areas of the outer circumference of the cylinder, resulting in low identification success rate and blind spots when the reader approaches from a fixed direction.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides an RFID tag antenna based on a flexible substrate with a helical involute structure, comprising:

[0007] Flexible substrate;

[0008] An antenna radiator is disposed above a flexible substrate. The antenna radiator includes a loop antenna located at the center of the flexible substrate and used to cover the end of a cylinder. The loop antenna is connected to a branch antenna disposed on the flexible substrate via a bent antenna disposed at its outer end, which is used to cover the outer circumference of the cylinder. The loop antenna, the bent antenna and the branch antenna are designed as a single piece.

[0009] The protective layer includes a circular membrane covering the loop antenna, the upper surface of the branch antenna being covered with a rectangular membrane connected to the outer surface of the circular membrane, and an anti-tilting component being provided on the upper surface of the circular membrane.

[0010] Furthermore, the innermost ring antenna of the antenna radiator is surrounded by a blank area, which is used to accommodate the RFID chip.

[0011] Furthermore, several loop antennas, bent antennas, and branch antennas are provided, and several loop antennas are distributed in a circular array with the blank area as the center.

[0012] Furthermore, the loop antenna adopts a spiral structure design, and the branch antenna adopts a serpentine strip structure design. Several loop antennas spirally contract from the outside to the center simultaneously to form a spiral involute structure.

[0013] Furthermore, the thickness of the bent antenna is designed to be gradually increased, with the thickness at both ends being greater than the thickness in the middle.

[0014] Furthermore, the outer surface of the branch antenna is provided with an adhesive layer connected to the lower surface of the rectangular film, and a fixing strip is fixedly connected to the side of the rectangular film away from the circular film. The thickness of the fixing strip is greater than the thickness of the rectangular film, and an arc groove is formed on the side of the fixing strip close to the rectangular film.

[0015] Furthermore, the anti-warping component includes a connecting film, which is fixedly connected to the upper surface of the circular film. The outer circumference of the connecting film has a notch, which is triangular in design. Multiple notches are arranged in a circumferential array around the circular film. A gap-sealing film is provided on the outer circumference of the connecting film, and a placement groove is provided on the outer surface of the rectangular film. The gap-sealing film is used to cover the gap between two adjacent rectangular films, and the side of the gap-sealing film closest to the rectangular film has adhesive backing.

[0016] Furthermore, a buckle is fixedly connected to the upper surface of the connecting membrane, and a retaining ring is slidably connected to the outer surface of the buckle.

[0017] The technical solution provided by this invention has the following advantages compared with the prior art:

[0018] This invention features an antenna radiator comprising a loop antenna, a bent antenna, and a branch antenna. The loop antenna covers the end face of the cylinder, and the branch antenna covers the outer surface. The smooth transition design of the bent antenna effectively solves the problem of large blind spots. The spiral involute structure of the loop antenna enhances end-face radiation, while the serpentine structure of the branch antenna optimizes circumferential coverage. Both are integrated into a single bent antenna, achieving lossless signal transmission. Simultaneously, the coordinated design of the flexible substrate and protective layer ensures the antenna can be smoothly bent from a planar state to a form where the end face and curved surface coexist, closely fitting the composite surface of the cylinder. This eliminates blind spots and ensures the stability of the mechanical structure. It also achieves full coverage of one end face and the outer surface of the cylinder, providing a wide recognition range. This avoids the problem of traditional planar antennas, where the radiation range is concentrated along the axial direction. When the reader approaches from the side (circumferential direction), the signal strength attenuates sharply, easily creating blind spots. Conversely, if only fitted to the outer surface of the cylinder, the antenna radiation direction is mainly distributed along the circumference, leading to reading failures due to insufficient signal coverage when the reader approaches from the axial direction (end direction). Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0020] Figure 1 This is a three-dimensional structural diagram of an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the initial separation structure of the flexible substrate, antenna radiator, circular film, and connecting film in an embodiment of the present invention.

[0022] Figure 3 This is a schematic cross-sectional view of the connecting membrane according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the separation structure of the flexible substrate, antenna radiator, circular film, adhesive layer and connecting film in another state according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the antenna radiator and blank area according to an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the separation structure of the protective layer in an embodiment of the present invention;

[0026] Figure 7 This is an embodiment of the present invention. Figure 3 A magnified structural diagram of part A in the middle.

[0027] The labels in the diagram represent: 1. Flexible substrate; 2. Antenna radiator; 21. Loop antenna; 22. Bent antenna; 23. Branch antenna; 3. Protective layer; 31. Circular film; 32. Rectangular film; 321. Fixing strip; 3211. Arc groove; 322. Placement groove; 33. Anti-warping component; 331. Connecting film; 332. Notch; 333. Seam sealing film; 334. Buckle; 335. Ring; 34. Adhesive layer; 4. Blank area. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] The present invention will be further described below with reference to embodiments. Example

[0030] Please see Figures 1-7 This invention provides a technical solution: an RFID tag antenna based on a flexible substrate with a helical involute structure, comprising:

[0031] Flexible substrate 1;

[0032] Antenna radiator 2 is disposed above flexible substrate 1. Antenna radiator 2 includes a loop antenna 21, which is located at the center of flexible substrate 1 and is used to cover the end of the cylinder. The loop antenna 21 is connected to a branch antenna 23 disposed on the flexible substrate 1 through a bent antenna 22 disposed at its outer end, which is used to cover the outer circumference of the cylinder. The loop antenna 21, the bent antenna 22 and the branch antenna 23 are designed as a single piece.

[0033] The protective layer 3 includes a circular membrane 31 covering the loop antenna 21, and a rectangular membrane 32 connected to the outer surface of the circular membrane 31 covering the upper surface of the branch antenna 23. An anti-tilting component 33 is provided on the upper surface of the circular membrane 31.

[0034] The innermost ring antenna 21 of the antenna radiator 2 is surrounded by a blank area 4, which is used to accommodate the RFID chip. The shape of the blank area 4 matches the RFID chip, and conductive adhesive dots or elastic conductive contacts are set in the blank area 4. After the chip is placed in the blank area 4, it can achieve accurate positioning and fixation of the chip, and ensure a stable electrical connection between the chip and the ring antenna 21, thereby improving the reliability of the tag operation.

[0035] Several loop antennas 21, bent antennas 22 and branch antennas 23 are provided, and several loop antennas 21 are distributed in a circular array with the blank area 4 as the center.

[0036] The loop antenna 21 adopts a spiral structure design, and the branch antenna 23 adopts a serpentine strip structure design. Several loop antennas 21 spirally contract from the outside to the center at the same time to form a spiral involute structure.

[0037] The thickness of the bent antenna 22 is designed with a gradual change, with the thickness at both ends being greater than that in the middle. This gradual transition structure makes the transition from the loop antenna 21 to the bent antenna 22 and then to the branch antenna 23 smoother, reducing signal reflection and loss at the transition points, improving the mechanical strength and fatigue resistance of the bent antenna 22, and extending the antenna's service life.

[0038] The outer surface of the branch antenna 23 is provided with an adhesive layer 34 that is connected to the lower surface of the rectangular film 32. A fixing strip 321 is fixedly connected to the side of the rectangular film 32 away from the circular film 31. The thickness of the fixing strip 321 is greater than the thickness of the rectangular film 32. An arc groove 3211 is opened on the side of the fixing strip 321 close to the rectangular film 32.

[0039] The anti-warping component 33 includes a connecting film 331, which is fixedly connected to the upper surface of the circular film 31. The outer circumference of the connecting film 331 has a notch 332, which is triangular in design. Multiple notches 332 are arranged in a circumferential array around the circular film 31. A gap-sealing film 333 is provided on the outer circumference of the connecting film 331. A placement groove 322 is provided on the outer surface of the rectangular film 32. The gap-sealing film 333 is used to cover the gap between two adjacent rectangular films 32, and an adhesive backing is provided on the side of the gap-sealing film 333 closest to the rectangular film 32.

[0040] A buckle 334 is fixedly connected to the upper surface of the connecting membrane 331, and a retaining ring 335 is slidably connected to the outer surface of the buckle 334.

[0041] The flexible substrate 1 is made of a material with high flexibility and bending resistance, preferably a polyimide film or a polyethylene terephthalate film. The flexible substrate 1 can adapt to the arc structure of the cylindrical surface and bend with the shape of the cylindrical surface during the bonding process, ensuring that the entire tag antenna is tightly bonded to the cylindrical surface and avoiding lifting or falling off due to excessive rigidity of the flexible substrate 1.

[0042] Antenna radiator 2 is disposed above flexible substrate 1 and is made of conductive material through an integral molding process. The conductive material is preferably copper foil, silver paste, or graphene conductive ink. Antenna radiator 2 is integrally molded from copper foil through etching or printed with silver paste or graphene conductive ink and disposed above flexible substrate 1. It includes a loop antenna 21, a bent antenna 22, and a branch antenna 23. Among them, four loop antennas 21 are arranged in a circular array with blank area 4 as the center. They adopt a spiral structure design, which spirals inward from the outside to the center to form a spiral involute structure, used to cover the end of the cylinder and enhance axial signal coverage. The bent antenna 22 connects the loop antenna 21 and the branch antenna 23. Its thickness adopts a gradual design, with thicker ends that are the same thickness as the loop antenna 21 and the branch antenna 23, and thinner middle. Carbon fiber microfilaments are added to the material, and the surface is coated with polyimide coating to improve mechanical strength and fatigue resistance. The branch antenna 23 adopts a serpentine strip structure and is connected to the loop antenna 21 through the bent antenna 22. It is used to cover the arc surface of the outer circumference of the cylinder to optimize impedance matching and bending adaptability.

[0043] The innermost ring antenna 21 of the antenna radiator 2 forms a blank area 4. The size of the blank area 4 is slightly larger than the RFID chip shell, placing it in the center. The shape of the blank area 4 matches the RFID chip, and conductive adhesive dots are placed inside to achieve chip positioning, fixation, and stable electrical connection with the ring antenna 21. The RFID chip is placed in the blank area 4, and the conductive adhesive dots are cured by a dispensing machine to achieve electrical connection between the RFID chip and the ring antenna 21.

[0044] Initial state of the RFID tag antenna:

[0045] The circular membrane 31 and the four rectangular membranes 32 on the outer ring of the protective layer 3 are designed as an integral structure. The loop antenna 21, the bent antenna 22 and the branch antenna 23 are designed as an integral structure. The connecting membrane 331 and the slit membrane 333 are also designed as an integral structure. The shape of the flexible substrate 1 is the same as that of the circular membrane 31 and the rectangular membranes 32 on its outer surface.

[0046] In its initial state, the flexible substrate 1 is planar, with adhesive backing on its lower surface, and is placed on the upper surface of the base paper. The loop antenna 21, bent antenna 22, and branch antenna 23 are all on the same horizontal plane, laid flat on the upper surface of the flexible substrate 1 without any bending or deformation. The four loop antennas 21 are arranged in a 90-degree circular array centered on the blank area 4, with spacing between adjacent loop antennas 21. The outer edge of their spiral involute structure smoothly connects to one end of the bent antenna 22, without any steps or protrusions at the connection. The bent antenna 22 has an arc-shaped transition, with both ends integrally formed with the outer ring of the loop antenna 21 and the starting end of the branch antenna 23, respectively. Due to its gradually changing thickness design, it smoothly transitions from the thicker end of the loop antenna 21 to the thinner middle section, and then to the thicker end of the branch antenna 23, presenting a symmetrical shape that is thinner in the middle and thicker at both ends. The surface is uniformly coated with a polyimide coating, free of bubbles or scratches. Four branch antennas 23 are laid flat along the rectangular extension of the flexible substrate 1. The straight length of each segment of the serpentine bending structure is fixed, the bending angle is 90 degrees, and the line width remains unchanged.

[0047] The circular membrane 31, fixing strip 321, and rectangular membrane 32 are all on the same horizontal plane and laid flat on the upper surface of the antenna radiator 2. The lower surface of the circular membrane 31 is pre-coated with an adhesive layer matching the area of ​​the loop antenna 21, with its edges aligned with the outer ring of the loop antenna 21. The lower surface of the rectangular membrane 32 is attached to the adhesive layer 34 on the branch antenna 23. The fixing strip 321 is located at the end of the rectangular membrane 32, with the arc groove 3211 facing the center area of ​​the blank area 4 and parallel to the long side of the rectangular membrane 32. Correspondingly, the connecting membrane 331 of the anti-warping component 33 is laid flat on the upper surface of the circular membrane 31, with the edges of the multiple triangular notches 332 on the periphery neat. The distance from the center point of the connecting membrane 331 to the starting end of the notch 332 is equal to the radius of the circular membrane 31. At this time, the adhesive protective layer of the outer circumference of the connecting membrane 331 on one side of the notch 332 and the sealing membrane 333 has not yet been removed. This adhesive protective layer is located between the connecting membrane 331 and the circular membrane 31 and the rectangular membrane 32. The buckle 334 is L-shaped, and the retaining ring 335 is restricted to the upper surface of the connecting membrane 331 by four buckles 334. The radius of the retaining ring 335 is larger than the radius of the end of the cylinder, and the radius of the cross-section of the retaining ring 335 is the same as the radius of the cross-section of the arc groove 3211.

[0048] The backing paper is made of release paper with a smooth surface. The flexible substrate 1 is completely adhered to the backing paper by the adhesive on its lower surface, without any lifting, offset, or air bubbles. The coverage area of ​​the adhesive is completely consistent with the size of the flexible substrate 1, and there is no adhesive leakage at the edges. At this time, the entire tag antenna is in a state of preparation for assembly.

[0049] The process of mounting the tag antenna onto the surface of a cylinder:

[0050] Clean the surface of the cylinder, wipe the ends and outer circumference of the cylinder with alcohol, peel off the release layer of the bottom paper on the flexible substrate 1, align the central circular area of ​​the flexible substrate 1 with the end of the cylinder, and correspondingly align the center points of the loop antenna 21 and the circular film 31 with the center points of the cylinder end, so that the four rectangular films 32 are evenly distributed along the circumference of the outer surface of the cylinder, and the included angle between the center lines of adjacent rectangular films 32 is 90 degrees. After the central circular area of ​​the flexible substrate 1 is attached to the end of the cylinder, simultaneously bend the rectangular area of ​​the flexible substrate 1, together with the adhesive layer 34, the branch antenna 23 and the rectangular films 32, along the part of the bent antenna 22, along the outer diameter of the end of the cylinder by 90 degrees. (The thicker parts at both ends of the bent antenna 22 provide support, while the thinner part in the middle bends naturally with the flexible substrate 1, forming a smooth arc transition. The polyimide coating and carbon fiber microfilaments on the surface effectively resist bending stress, preventing cracks or deformation.) After aligning the center line of the rectangular area of ​​the flexible substrate 1 with the generatrix of the cylinder, press it from the center line of the rectangular area of ​​the flexible substrate 1 to both sides onto the outer circumference of the cylinder. This allows the serpentine structure of the branch antenna 23 to fit tightly against the circumferential curved surface of the cylinder along with the flexible substrate 1. The bending angle of the serpentine unit naturally adjusts with the curvature of the cylinder, and the line width and spacing remain stable. The rectangular area of ​​the flexible substrate 1 forms a surface contact with the outer surface of the cylinder. Repeating the above process, multiple rectangular areas of the flexible substrate 1, the adhesive layer 34, the branch antenna 23, and the rectangular film 32 are bent and fitted to the outer surface of the cylinder.

[0051] At this time, the side of the rectangular membrane 32 coincides with the generatrix of the cylinder and is perpendicular to the end of the cylinder. There is a gap between the sides of two adjacent rectangular membranes 32, and the side of the rectangular membrane 32 closest to the circular membrane 31 coincides with the outer diameter of the end of the cylinder.

[0052] Remove the protective adhesive layer from the outer perimeter of the connecting film 331 and the seam-sealing film 333. The adhesive layer on the outer perimeter of the connecting film 331 is divided into multiple parts by the notch 332. First, bend the portion of the connecting film 331 between two adjacent notches 332 along the outer diameter of the cylindrical end. Align the center line of this portion of the connecting film 331 with the center line of the rectangular film 32. Apply the film evenly from one end closer to the circular film 31 towards the end of the rectangular film 32. During the application process, apply uniform pressure along the surface of the seam-sealing film 333 with your fingertips to ensure full contact between the adhesive and the rectangular film 32 and the cylindrical surface. Simultaneously, expel air from under the seam-sealing film 333 to avoid air bubbles. Cover the gap between the circular film 31 and the rectangular film 32, forming a cover at the end of the cylinder to prevent warping during transportation. Then, remove the protective adhesive layer of the seam-sealing film 333 and cover the gap between two adjacent rectangular films 32. Scrape and press from the center of the gap outwards to both sides to seal the gap between the adjacent rectangular films 32. After bonding, the gap-sealing film 333 is tightly bonded to the rectangular film 32 and the cylindrical surface to form a continuous protective barrier, which can effectively block dust and moisture from entering through the gap and protect the internal branch antenna 23 from corrosion.

[0053] The placement groove 322 on the outer surface of the rectangular membrane 32 can be divided into a horizontal groove and a vertical groove. After the outer periphery of the connecting membrane 331 and the sealing membrane 333 are bent, they can be embedded into the placement groove 322 on the outer surface of the rectangular membrane 32. The outer periphery of the connecting membrane 331 is embedded in the horizontal groove, and the sealing membrane 333 is embedded in the vertical groove. At this time, the outer periphery of the connecting membrane 331 and the sealing membrane 333 are flush with the outer surface of the rectangular membrane 32.

[0054] The diameter of the retaining ring 335 is larger than the diameter of the cylinder formed by multiple rectangular membranes 32 covering the outer surface of the cylinder (ensuring that the retaining ring 335 can be smoothly fitted into the cylinder and that it can form uniform circumferential pressure on the protective layer 3 after installation). The bottom end of the buckle 334 is located at the junction of the circular membrane 31 and the rectangular membrane 32. After the outer periphery of the connecting membrane 331 and the sealing membrane 333 are bent, the retaining ring 335 is moved downward from the end of the cylinder. During this process, the surface of the retaining ring 335 contacts the outer surfaces of the rectangular membrane 32, the outer periphery of the connecting membrane 331, and the sealing membrane 333. The inner surface of the retaining ring 335 first contacts the outer periphery of the connecting membrane 331. Because the inner diameter of the retaining ring 335 is slightly larger than the outer diameter of the protective layer 3 after bending, its chamfered inner ring surface first adheres to the connecting membrane 331, and then gradually covers the outer surfaces of the rectangular membrane 32 and the sealing membrane 333. The retaining ring 335 at this time acts as a scraper, applying uniform circumferential pressure to the protective layer 3 through its own rigidity.

[0055] When passing through the area of ​​the connecting membrane 331, the retaining ring 335 further compacts the joint between the connecting membrane 331 and the circular membrane 31, expelling any remaining micro-air bubbles and ensuring there are no gaps between them. When sliding to the area of ​​the rectangular membrane 32, the inner surface of the retaining ring 335 rolls along the length of the rectangular membrane 32, applying secondary pressure to the adhesive layer 34 between the rectangular membrane 32 and the flexible substrate 1, enhancing the adhesion of the pressure-sensitive adhesive. Especially for the protruding parts of the serpentine structure of the branch antenna 23, the pressure of the retaining ring 335 ensures that the rectangular membrane 32 tightly wraps around the antenna, preventing localized gaps. When passing through the area of ​​the sealing membrane 333, the retaining ring 335 compacts the joint between the sealing membrane 333 and the rectangular membrane 32 and the cylindrical surface, eliminating any curling edges on the sealing membrane 333 and ensuring a tight seal.

[0056] The bottom edge of the gap-sealing membrane 333 extends to the bottom edge of the rectangular membrane 32. When the retaining ring 335 slides to the position of the fixing strip 321, the arc groove 3211 on the inner wall of the fixing strip 321 precisely engages with the outer surface of the retaining ring 335, thus fixing the retaining ring 335. At this time, the outer circumference of the retaining ring 335 is covered by the gap-sealing membrane 333, which wraps between the arc groove 3211 and the retaining ring 335. The retaining ring 335 firmly fixes the connecting membrane 331, the rectangular membrane 32, and the gap-sealing membrane 333 to the cylindrical surface through circumferential pressure, forming a dual fixing structure of rigid clamping and flexible fit. The rigidity of the retaining ring 335 ensures that the protective layer 3 does not shift under the action of vibration and collision external forces, while the flexibility of the protective layer 3 ensures a tight fit with the cylindrical curved surface.

[0057] In summary, this RFID tag antenna has the following advantages:

[0058] Advantage 1: In its initial state, the flexible substrate 1, antenna radiator 2, and protective layer 3 are all planar. The adhesive backing of the lower surface of the flexible substrate 1 is attached to the release liner, facilitating storage and transportation and avoiding structural deformation caused by premature bending. During installation, it can be easily attached to the end and outer circumference of the cylinder through a simple bending operation, without the need for complicated tools or processes.

[0059] Advantage 2: When identifying cylindrical objects, traditional tag antennas can only be attached to the end face or outer surface of the cylinder, failing to achieve full coverage of both surfaces simultaneously, resulting in significant limitations in identification. If only attached to the end face, the radiation range of a traditional planar antenna is concentrated along the axial direction. When the reader approaches from the side (circumferential direction) of the cylinder, the signal strength attenuates sharply, easily creating a blind spot. If only attached to the outer surface, the antenna radiation direction is mainly distributed along the circumference. When the reader identifies from the axial direction (end direction), it often fails to read the object due to insufficient signal coverage. In this invention, the loop antenna 21 covers the end face of the cylinder, the branch antenna 23 covers the outer surface, and the smooth transition design of the bent antenna 22 solves the problem of large blind spots. The spiral involute structure of the loop antenna 21 enhances end face radiation, and the serpentine structure of the branch antenna 23 optimizes circumferential coverage. Both are integrated into the bent antenna 22 to achieve lossless signal transmission. Meanwhile, the collaborative design of the flexible substrate 1 and the protective layer 3 ensures that the antenna can be smoothly bent from a planar state into a form where the end face and the curved surface coexist, closely fitting the composite surface of the cylinder, which not only eliminates the identification blind spot, but also ensures the stability of the mechanical structure.

[0060] Advantage 3: If the tag antenna protective layer 3 covers a multi-segment structure of curved or flat surfaces, it is prone to sealing failure due to loose adhesion and edge lifting. However, the connecting film 331 can cover the junction of the circular film 31 and the rectangular film 32 (i.e., the transition area between the end of the cylinder and the circumference), which is an arc-shaped transition surface from a flat surface to a curved surface. If the circular connecting film 331 without the notch 332 is attached, it is prone to wrinkles or gaps due to the curvature of the curved surface, leading to sealing failure. However, the triangular notch 332, through structural segmentation and deformation compensation, divides the outer periphery of the connecting film 331 into multiple independent fan-shaped bonding units. The edges of the fan-shaped units form a gradually changing width, with a narrow width near the inner side of the circular film 31 and a flat end; and a wide width near the outer side of the rectangular film 32 and a curved circumference. This gradual structure can smoothly transition the curvature change from a flat surface to a curved surface, ensuring that the connecting film 331 forms a surface contact with the cylindrical surface without any gaps, thereby strengthening the sealing protection at the junction of the circular film 31 and the rectangular film 32. The sealing film 333 is longer than the rectangular film 32, ensuring full coverage of the gap by extending from the edge of the circular film 31 to the interior of the arc groove 3211 in the fixing strip 321. Simultaneously, the outer surface of the rectangular film 32 has a pre-set vertical placement groove 322. After the sealing film 333 is applied, it can be embedded into the groove, flush with the surface of the rectangular film 32, avoiding wear or lifting caused by protrusions and structurally eliminating the potential for damage to the sealing edge. The anti-lifting component 33 ensures complete sealing of the gap between adjacent rectangular films 32 and circular films 31, solving the problem that traditional label protective layers 3 cannot completely cover the gaps and improving the label's protective performance.

[0061] Fourthly, the thickness of the bent antenna 22 gradually changes, with a thinner middle section resisting cracking and thicker sections at both ends maintaining low resistance. The reduced thickness in the middle region of the bent antenna 22 significantly lowers the bending stiffness, giving this area greater flexibility. When the label is bent from a plane to fit a cylinder at a 90-degree angle, the thinner middle section can naturally bend with the flexible substrate 1. The bending stress (outer layer tension, inner layer compression) generated during deformation is significantly reduced, far below the material's yield strength, fundamentally preventing cracks or fractures caused by stress exceeding the limit. Simultaneously, the increased thickness at both ends of the bent antenna 22 correspondingly increases the conductive cross-sectional area, significantly reducing DC resistance. This ensures that the energy received by the loop antenna 21 can be efficiently transmitted to the branch antenna 23, or that the signal from the branch antenna 23 can be stably fed back to the loop antenna 21, avoiding energy loss due to excessive resistance.

[0062] Advantage 5: The inner diameter of the retaining ring 335 is slightly larger than the outer diameter of the protective layer 3. During installation, it slides axially, combining the functions of scraper compaction and rigid clamping. During installation: the retaining ring 335 compacts the connecting film 331, rectangular film 32, and sealing film 333 during sliding, expelling air bubbles and ensuring a tight fit between each protective layer. This replaces manual scraper operation, improving compaction uniformity and increasing the contact area between the flexible substrate 1 and the outer surface of the cylinder. During use, the rigid retaining ring 335 generates circumferential pressure, completely encasing the sealing film 333 within the arc groove 3211 and itself, preventing the edges of the sealing film 333 from lifting. This firmly fixes the protective layer 3 to the outer surface of the cylinder, preventing edge lifting or displacement caused by vibration or collision, and solving the problem of traditional labels easily falling off when fixed only by adhesive backing.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. An RFID tag antenna based on a flexible substrate with a helical involute structure, characterized in that, include: Flexible substrate (1); Antenna radiator (2), the antenna radiator (2) is disposed above the flexible substrate (1), the antenna radiator (2) includes a loop antenna (21), the loop antenna (21) is located at the center of the flexible substrate (1) and is used to cover the end of the cylinder, the loop antenna (21) is connected to a branch antenna (23) disposed on the flexible substrate (1) through a bent antenna (22) disposed at its outer end, and is used to cover the outer circumference of the cylinder, the loop antenna (21), the bent antenna (22) and the branch antenna (23) adopt an integral molding design; The protective layer (3) includes a circular film (31) covering the loop antenna (21), and the upper surface of the branch antenna (23) is covered with a rectangular film (32) connected to the outer surface of the circular film (31). The upper surface of the circular film (31) is provided with an anti-tilting component (33). The anti-warping component (33) includes a connecting membrane (331), which is fixedly connected to the upper surface of the circular membrane (31). The outer circumferential surface of the connecting membrane (331) is provided with a notch (332), which is triangular in design. Multiple notches (332) are provided and arranged in a circumferential array with the circular membrane (31) as the center. A gap-sealing membrane (333) is provided on the outer circumferential surface of the connecting membrane (331). A placement groove (322) is provided on the outer surface of the rectangular membrane (32). A buckle (334) is fixedly connected to the upper surface of the connecting membrane (331), and a retaining ring (335) is slidably connected to the outer surface of the buckle (334).

2. The RFID tag antenna based on a flexible substrate with a spiral involute structure according to claim 1, characterized in that: The innermost ring antenna (21) of the antenna radiator (2) is surrounded by a blank area (4) for accommodating the RFID chip.

3. The RFID tag antenna based on a flexible substrate with a spiral involute structure according to claim 2, characterized in that: Several loop antennas (21), bent antennas (22) and branch antennas (23) are provided, and several loop antennas (21) are distributed in a circular array with the blank area (4) as the center.

4. The RFID tag antenna based on a flexible substrate with a helical involute structure according to claim 3, characterized in that: The loop antenna (21) adopts a spiral structure design, and the branch antenna (23) adopts a serpentine strip structure design.

5. The RFID tag antenna based on a flexible substrate with a spiral involute structure according to claim 3, characterized in that: The thickness of the bent antenna (22) is designed to be gradually increased, with the thickness at both ends of the bent antenna (22) being greater than the thickness in the middle.

6. The RFID tag antenna based on a flexible substrate with a helical involute structure according to claim 4, characterized in that: The outer surface of the branch antenna (23) is provided with an adhesive layer (34) connected to the lower surface of the rectangular film (32). A fixing strip (321) is fixedly connected to the side of the rectangular film (32) away from the circular film (31). The thickness of the fixing strip (321) is greater than the thickness of the rectangular film (32). An arc groove (3211) is opened on the side of the fixing strip (321) close to the rectangular film (32).

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