Impedance stabilizer RFID tag antenna

Abstract

An RFID tag is disclosed, comprising a conductive layer disposed on a dielectric substrate layer. The conductive layer features a double slot structure and a plurality of meandered slots, cooperatively providing impedance stabilization across diverse attachment surfaces and environments. The configuration enables the conductive layer to maintain a resonance frequency within ±5% of a target frequency when applied to containers of varying materials and contents with different permittivities. The double slot structure creates multiple resonant paths, while the meandered slots increase electrical length in a compact form factor. The antenna incorporates anti-tampering features through strategically placed cut lines designed to provide visible evidence of tampering attempts.

Description

IMPEDANCE STABILIZER RFID TAG ANTENNARELATED APPLICATION

[0001] The present application claims priority to US Provisional Application No. 63 / 729,770 filed on December 9, 2024, the entire contents and disclosure of which is hereby incorporated by reference.FIELD OF THE INVENTION

[0002] The present disclosure relates generally to the field of Radio Frequency Identification (RFID) technology and, more particularly, to RFID tag antennas designed for universal application across a wide range of substrate materials.BACKGROUND

[0003] Radio Frequency Identification (RFID) technology has become increasingly prevalent in tracking and managing inventory across various industries. RFID tags, consisting of a radio frequency chip and an antenna, are attached to items or packaging to provide unique identification and wireless communication capabilities. However, the design and production of RFID tags that function efficiently across a wide range of packaging materials and containers have presented significant challenges to the industry.

[0004] The performance of RFID tag antennas is heavily influenced by the material to which they are attached. Different substrates, such as cardboard, plastic, glass, or metal, possess unique dielectric characteristics that substantially impact the antenna's impedance matching and overall efficiency. This variability in substrate properties often leads to decreased antenna performance, such as reduced read range due to destructive interference, detuning and / or signal loss, when a tag designed for one type of material is used on another.

[0005] Conventional RFID tag designs are typically adapted for a specific or limited range of substrates. When these tags are placed on materials with different dielectric properties, their radiation efficiency can decrease dramatically from the intended level. This reduction in efficiency is primarily due to changes in impedance matching between the RFID chip and its antenna, and can adversely affect energy transfer and proper tag functionality.

[0006] Current solutions to this problem have included encapsulating the RFID tag and antenna system on a known substrate before attaching it to the packaging. However, this approach results in bulky, expensive tags that are difficult to mount and prone to damage or detachment during handling. Also, such encapsulation increases cost, which in turn limits its adoption.

[0007] There is a clear need in the industry for an RFID tag antenna design that can maintain consistent impedance and radiation efficiency across a diverse range of substrate materials. Such a design would need to address the challenges posed by varying dielectric properties without compromising the tag's form factor, durability, or ease of application.SUMMARY

[0008] The present disclosure relates to an RFID tag and a method for stabilizing impedance in an RFID tag antenna. The antenna comprises a conductive layer, which operates as an antenna, disposed on a dielectric substrate layer. The conductive layer includes a double slot and multiple meandered slots. This configuration allows the antenna to maintain a stable resonance frequency across a wide range of container materials and contents with varying permittivities. The double slot and meander slot cooperatively provide impedance stabilization, enabling the antenna to maintain a resonance frequency within ±5% of a target frequency across a range of containers and permittivity. This design enables effective operation on a wide range of attachment surfaces.

[0009] In another aspect of the subject matter, a method for stabilizing impedance in an RFID tag is provided. The method involves providing a dielectric substrate layer, forming a conductive layer with a double slot and meandered slots, and configuring these elements to provide impedance stabilization. The method enables the antenna design to maintain a stable resonance frequency across various container materials and contents.

[0010] The RFID tag may have characteristic attributes such as:Specific dimensions and orientations of the slots;Operational frequency bands (FCC and ETSI);RFID chip connection methods;Anti-tampering mechanismsResistance to various environmental factorsStructural elements such as a printable surface, protective features, and adhesive components

[0011] As described herein, the present disclosure addresses the challenges of designing RFID tags that can function effectively across a wide range of packaging materials and contents, offering a versatile and robust solution for RFID tagging applications. This design enables the RFID tags' antenna to adapt to various container materials, including conductive materials, glass, plastic, liquid, and rubber, while maintaining consistent performance.BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a top view of an RFID tag according to a first embodiment of the subject matter, showing the double slot placed between two meander slots along the cross direction.

[0013] FIG. 2 is a top view of an RFID tag according to a second embodiment of the subject matter, showing the double slot placed between two meander slots along the machine direction.

[0014] FIG. 3 illustrates a view of a layered structure of the RFID tag with different layers underlying the tag in accordance with another embodiment of the subject matter.

[0015] FIG. 4 shows an overhead view of an RFID tag for application on metal, featuring an anti-tampering mechanism, according to an embodiment described herein.

[0016] FIG. 5 depicts a cross-sectional view of the RFID tag for application on metal with the placement of the different layers and cut lines for the anti-tampering mechanism according to an embodiment herein.

[0017] FIG. 6 illustrates an RFID tag with a disrupted / broken antenna due to a tampering attempt to remove the RFID tag from the attached metal surface, according to an embodiment herein.

[0018] FIGS. 7A-7D, 8A-8D, and 9A-9D illustrate different types of cut lines and their layouts in the RFID tag for the anti-tampering mechanism, according to some embodiments herein.

[0019] FIG. 10 illustrates different cut line patterns for the anti-tampering mechanism.

[0020] FIG. 11 illustrates that the antenna's read range performance remains largely stable despite variations in the material being tagged.DETAILED DESCRIPTION

[0021] The present subject matter is now described concerning the drawings, wherein reference numerals are used to refer to elements throughout. In the following description, for the purposes of explanation, numerous specific details are outlined to provide a thorough understanding thereof. It may be evident, however, that the present subject matter can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate a description.

[0022] The present subject matter provides a versatile and robust RFID tag designed to tag a wide range of materials and items to be tagged. Items of tagging involve a wide range of container materials and contents with varying permittivity. Container materials can be glass, rubber, plastic, and metal. The contents could also vary, and can include any or more liquids, meat, and so on, which alter permittivity.

[0023] The subject matter of the present disclosure can maintain a resonance frequency within a close range of a target frequency across diverse attachment surfaces, which represents a significant improvement over conventional RFID antennas that often suffer from detuning when applied to different materials with varying content and permittivity. The RFID tag of the present subject matter maintains a consistent resonance frequency when attached to conductive surfaces such as glass, plastic, liquid, and rubber, enabling it to radiate well in the FCC frequency band. The RFID tag also operates well in the ETSI band.

[0024] A versatile RFID tag is provided in one embodiment of the subject matter. The RFID tag involves an antenna with impedance stabilization (and adjustment) capabilities designed to maintain consistent performance across a wide range of attachment surfaces and environmental conditions. The technical advancement of the subject matter lies in its unique structure and configuration, which enables it to overcome the challenges typically associated with RFID tag performance on diverse materials.

[0025] Referring to FIG. 1 and FIG. 2, the RFID tag involves an antenna 100, 200 as a conductive layer disposed on a dielectric substrate layer (not shown in FIGS. 1 or 2). Theconductive layer features two key elements: a double slot structure 1 and multiple meandered slots 2. The conductive layer is a single-layer structure, and the double slot and the meander slot are coplanar. The conductive layer is secured on an antenna substrate (not shown in FIGS. 1 or 2) along the opposite side of the dielectric substrate layer. The antenna substrate may be made of, for example, a polymeric material and generally provides mechanical support to the conductive material. The double slot and multiple meander slot may work cooperatively to provide impedance stabilization, allowing the antenna to maintain a resonance frequency within a close range of the target frequency, such as the resonance frequency, across a range of container sizes and permittivity values. Preferably, the conductive layer is adhesively disposed on the dielectric layer. The dielectric substrate layer is illustrated and described in FIG. 3. In some embodiments, the conductive layer is configured to operate as an antenna of the RFID tag.

[0026] The RFID tag comprises a printable surface, such as a face stock or a top coating, on the opposite side of the conductive layer. It is disposed of over the antenna substrate according to an embodiment herein. In some embodiments, the RFID tag may additionally comprise a punched hole configured to protect an RFID chip.

[0027] The double slot and meander slot can have individual widths and lengths. Each meander slot is folded spatially in both the machine direction and the cross direction, and in a combination of the machine and cross directions, according to an embodiment. The meander slots are larger in dimension than the double slots. Alternatively, the meander slots are smaller than the double slots.

[0028] In one embodiment of the RFID tag, the meander slot may extend beyond the double slots by length or width. The meander slot extends in the machine direction. The meander slots and double slots are coplanar.

[0029] In one embodiment, as shown in FIG. 1, the double slot 1 is placed between two meandered slots 2 along the cross direction of the antenna. This configuration allows efficient use of the antenna's surface area and provides balanced impedance characteristics. This configuration of the double slot 1 between two meander slots 2 may help to lower the resonance frequency, considering the material and content of the item to which the antenna is attached.

[0030] An alternative embodiment, illustrated in FIG. 2, is the RFID tag 200, which has a double slot 1 positioned between two meandered slots 2 along the machine's direction. Thisarrangement may be preferred in certain applications where the antenna's form factor needs to be adapted for specific packaging requirements. This configuration of a double slot 1 between two meandered slots 2 along the machine direction may help to tune the resonance frequency higher, considering the material and content of the item to which the antenna is attached.

[0031] In one embodiment of the subject matter, an RFID chip (not shown in FIGS. 1 or 2) is electrically connected to the double slot 1 along the conductive pads, which are generally four in number. This connection can be made either at the center of the double slot or offset from the center of the slot, depending on the specific impedance-matching requirements of the chosen RFID chip or the material / content to be tagged.

[0032] In accordance with one embodiment of the subject matter, the double slot and multiple meander slot work cooperatively to provide impedance stabilization, allowing the antenna to maintain a resonance frequency within ±5% of the target frequency across a range of container sizes and permittivity values. The RFID tag is preferably configured to maintain a resonance frequency within ±5% of the center frequency, more preferably within ±3%, even more preferably within ±2%, and most preferably within ±1.5% of the center frequency, across a range of container types and permittivity values. For example, the FCC band allocates a frequency range of 902-928 MHz for the UHF RFID in the United States. A typical center frequency for a UHF RFID tag, which falls within the present subject matter, is often considered to be 915 MHz. Different materials can significantly affect the resonance frequency of any given RFID tag. For example, metal surfaces tend to detune the antenna, causing the resonance to shift to higher frequencies. High-dielectric materials, such as meat or liquids, tend to lower the resonance frequency.

[0033] For an RFID tag to operate across diverse materials, it should maintain its resonance within the range, such as retaining a resonance frequency within ±1.5% of the center frequency, which allows for these shifts while staying within the allocated band. An exemplary target would be:Lower bound: Approximately 902-905 MHz Upper bound: Approximately 925-928 MHz

[0034] Given these considerations, an effective resonance frequency range for the versatile UHF RFID tag of the present subject matter in the FCC band could be 902 MHz to 925MHz. This is roughly within ±2 to 1.5% around 915 MHz, ensuring compliance while allowingfor material-induced shifts. For example, this allows for upward frequency shifts when placed on metal surfaces and downward shifts when placed on high-dielectric materials, thereby maintaining operation within the FCC-allocated band.

[0035] In some embodiments for operation in the ETSI band, which allocates a frequency range of 865 MHz to 868MHz, the center frequency is often considered to be 866.5 MHz. Given the material-induced shifts, maintaining a resonance frequency within ± 1.5% of the center frequency would target a range of approximately 853.5 MHz to 879.5 MHz. However, to remain within the allocated ETSI band and allow for material shifts, an effective operating range for the versatile UHF RFID tag is preferably 865 MHz to 868 MHz.

[0036] In one embodiment, the target frequency used to assess resonance stability tolerance (±5%, ±3%, or ±1.5%) is the center frequency of the operational band selected for the RFID tag. The operational band may be the FCC UHF RFID band, the ETSI UHF RFID band, or both. For the FCC band, the center frequency is approximately 915 MHz. For the ETSI band, the center frequency is approximately 866.5 MHz. In embodiments designed for global operation, resonance stability may be evaluated against the center frequency of each applicable band, and tolerances may be expressed relative to the corresponding center frequency.

[0037] It is to be understood that the recitation of specific tolerance values (i.e., ±5%, ±3%, or ±1.5%) is intended to be exemplary and non-limiting. These discrete values do not preclude the application or claiming of other discrete measures, intermediate values, or subranges (e.g., ±4%, ±2.5%, ±1.0%, or other customized tolerances) that may be achieved or required depending on specific operational environments or target frequency bands.

[0038] The double slot 1 is the primary radiating element, providing complex impedance matching. The double slot configuration allows for fine-tuning of the antenna's impedance characteristics. The meandered slots 2 are designed to adapt the antenna's performance to various substrates, such as metal surfaces. By adjusting the parameters of the meandered slots, such as their length and gap width, the antenna's resonance can be significantly altered for on-metal applications while having minimal impact on performance on other dielectric materials.

[0039] FIG. 3 illustrates the dielectric substrate layer of an RFID tag 300 in accordance with one embodiment of the subject matter. The dielectric substrate layer may occur as a single or multi-layer, the latter of which is shown in FIG. 3. The dielectric substrate layerunderlies the conductive layer, including double slot 1 and meander slot 2. The conductive layer underlies an antenna substrate (not marked in FIG. 3), which provides strength and support to the conductive layer, which can be fragile otherwise. The antenna substrate is made of a polymeric material such as PET.

[0040] The dielectric substrate layer plays a significant role in the antenna's performance and durability, which may be required for a given application. The dielectric substrate layer is preferably made of polyethylene, PVC (Polyvinyl Chloride), PET (Polyethylene Terephthalate), or PU (Polyurethane), according to an embodiment herein. The subject matter of the RFID tag is designed, along with the design of the double slot and meander slot, to allow a thinner dielectric substrate layer to be used compared to what has been practiced in conventional art. It is estimated that a thickness of less than 1 mm works well in meeting and / or maintaining the antenna's electrical properties, such as allowing impedance stabilization or adjustment, meeting varying resonance frequencies and providing mechanical support. The dielectric substrate's thin profile also contributes to the RFID tag's overall flexibility, allowing it to conform to curved surfaces, such as metal pipes or cylindrical containers. In some embodiments, the dielectric substrate layer has a thickness in the range of 0.1 mm to 1 mm, wherein the dielectric substrate layer comprises one or more layers or films laminated together.

[0041] In a preferred embodiment, the dielectric substrate layer includes a hole 4 that accommodates the RFID chip (not shown in the Figures), which is electrically connected to the double slot 1. The hole 4, also called a protective hole, can run across the thickness of the dielectric layer and / or across the thickness of the multi-layer structure of the dielectric layer. The depth of the hole can be adjusted to match the thickness and dimensions of the RFID chip. The hole 4 provides mechanical protection to the RFID chip and / or the connection between the RFID chip and the conductive layer, including the double slot and meander slot. The hole 4 also allows for a flexible structure, allowing attachment to curved surfaces and durability to withstand various environmental stresses. The location or position of hole 4 can be adjusted based on the connection position between the RFID chip and the double slot.

[0042] FIGS. 4 and 5 illustrate an overhead and cross-sectional view of an RFID tag 400 and 500 for application on metal / metal surfaces and with an anti-tampering mechanism according to an exemplary embodiment. FIG. 5 illustrates the RFID tag 500, which involves amulti-layer laminate construction and describes the different layers. The conductive layer 3, which may be made of any conductive metal, includes double slots, meander slots (not shown in FIGS. 4 and 5), and the RFID chip 2a. The conductive layer 3 underlies an antenna substrate 1. This makes the antenna substrate 1 the topmost layer. A dielectric substrate layer 6 underlies the conductive layer 3. A dielectric adhesive layer 4b secures the dielectric substrate layer 6 to the conductive layer 3. Opposite the conductive layer 3, the dielectric substrate layer is configured for attachment to a surface 7, which can be of a different material and composition, by an attachment adhesive 4b. A liner (not shown in the Figures) may be attached to the dielectric substrate layer over the dielectric adhesive layer 4b to prevent exposure of the dielectric adhesive layer, which is generally tacky at room temperature, until the RFID tag is applied to an intended container through the adhesive. The liner is peeled off and disposed of from the RFID tag before the RFID tag is applied to an intended surface. In other words, the liner is adhesively attached to the underside of the dielectric substrate layer.

[0043] One or more cut lines are introduced into the dielectric layer 6 as an antitampering feature. The cut line runs through the thickness of the dielectric layer 6, spanning from the conductive layer 3 toward the surface 7. The cut line(s) can have different layouts and shapes, as illustrated in FIG. 5. Two-cut lines 5a and 5b are shown as an example. 5a and 5b can be extensions of the same cut line occurring at two different locations of the dielectric layer 6. Alternatively, 5a and 5b can be two distinct cut lines of the same shape or layouts or other shapes and layouts. There can be varying densities of the cut lines. The cut lines are intentionally created to introduce structural weaknesses. They are strategically placed to intersect with the fragile areas of conductive layer 3, causing breakage, disruption, and electrical discontinuity of the conductive layer / antenna when tampered with, rendering the tag non-functional. These cut lines, which can vary in pattern (e.g., straight, wavy, or sawtoothed, etc.), are designed to break or deform upon removal attempts, providing visible evidence of tampering and potentially disrupting the antenna's functionality.

[0044] In some embodiments, the RFID tag incorporates a tamper-evident mechanism comprising one or more intentionally introduced cut lines in the dielectric substrate layer. These cut lines extend fully through the thickness of the dielectric substrate layer and are strategically placed to intersect with the conductive layer (antenna), defining a fragile area. This configuration ensures that any forceful attempt to remove the RFID tag from the attached surface causes the cut line to propagate a tear, resulting in immediate breakage andelectrical discontinuity in the conductive layer, thereby permanently rendering the tag nonfunctional.

[0045] Furthermore, the pattern of the cut lines can be selected to enhance the antitampering feature, with options including straight, wavy, and saw-toothed patterns. These patterns are specifically designed to leave visible evidence of tampering upon removal, making it difficult or impossible to conceal the attempted theft or transfer of the tag.

[0046] FIG. 6 illustrates an RFID tag 600 with a disrupted / broken antenna due to a tampering attempt to remove the RFID tag from the attached metal surface, according to an embodiment herein. Any tampering attempt, such as removing the RFID tag from surface 7, caused the conductive layer 3 to break apart into 3a and 3b, resulting in an electrical discontinuity and rendering the RFID tag non-functional. The cut line, such as 5b, helps propagate the removable material and ultimately intersects with, and causes the breaking of, the conductive layer / antenna 3.

[0047] FIGS. 7A-7D, 8A-8D, and 9A-9D illustrate different types of cut lines and their layouts in the RFID tag for the anti-tampering mechanism, according to some embodiments herein. FIG. 10 illustrates different cut line patterns for the anti-tampering mechanism. Antitampering mechanisms, such as introducing cut lines in the dielectric layer 6, are not just provided for circuit disruptions. The cut lines leave visible evidence, as many patterns of cut lines (straight, wavy, saw-toothed, etc.) are designed to leave visible evidence of tampering. When the RFID tag is forcibly removed or manipulated, these lines are difficult to conceal or repair. The cut lines can offer customized fragility (as shown in FIG. 7) and varying degrees of fragility, creating a fragile area around the intersection with the conductive layer. For instance, straight lines provide a clean break; saw-toothed lines create a more jagged, obvious tear; wavy lines make it nearly impossible to realign the tag after removal in accordance with some embodiment of the subject matter.

[0048] In another instance, the cut lines can provide tailored sensitivity. The design of cut lines can be tailored to meet the specific needs of each application. For instance, more sensitive applications might use more intricate or densely packed cut lines, while less critical applications might use simpler patterns.

[0049] In yet another embodiment of the subject matter, a method for stabilizing impedance in an RFID tag antenna, particularly designed for use across a wide range of container materials and contents with varying permittivity, is described. The method beginswith providing a dielectric substrate layer, which serves as the base for the antenna structure as a conductive layer. On this dielectric substrate, the conductive layer is formed, and the conductive layer contains a double slot structure and a plurality of meandered slots.

[0050] The double slot structure is created within the conductive layer, serving as a primary element for impedance matching. Complementing this, multiple meandered slots are formed, strategically positioned to work in concert with the double slot. These meandered slots are uniquely designed, folded spatially into both the machine direction and cross direction. This spatial folding technique allows for an increased electrical length while maintaining a compact physical footprint.

[0051] An aspect of the method involves carefully configuring the double slot and meandered slots. These elements are designed to cooperatively provide impedance stabilization, enabling the RFID tag to function effectively when attached to a diverse range of containers. The materials of these containers may vary significantly, as may their contents, resulting in a wide range of permittivity values that the antenna must accommodate.

[0052] The configuration process for the double slot and meandered slots ensures the antenna maintains its resonance frequency within ±5%, or preferably ±3%, or more preferably ±1.5% of a target frequency across the entire range of container materials and permittivities. The frequency range for resonances has already been described herein. This wide tolerance allows for effective operation on diverse attachment surfaces / contents, significantly enhancing the versatility of the RFID tag.

[0053] In some embodiments, this step of "carefully configuring" as mentioned before is executed through a process of adapting the geometric parameters of the slot elements to meet strict tolerance thresholds.

[0054] In some embodiments, the configuration process for the double slot and meandered slots ensures the antenna maintains its resonance frequency within a close range of a target frequency across the entire range of container materials and permittivities, wherein said configuring may comprise adapting the geometric parameters of the conductive layer— including adjusting the electrical length, gap widths, and capacitive coupling of the double slot and meandered slots— to tune the antenna's inductive and capacitive reactance, thereby enabling the antenna to maintain a resonance frequency (such as ±5%, or ±3%, or ±1.5%) of the target frequency irrespective of the container's material permittivity. In the antenna layout, the double slot is positioned between two meander slots, either along thecross or machine direction. Importantly, the double slot and all meandered slots are designed to be co-planar, ensuring a uniform and thin profile for the antenna.

[0055] The method includes configuring the antenna to operate in specific frequency bands. It can be tailored to operate in the FCC frequency band, the ETSI frequency band, or both, enabling the RFID tag to have global applicability.

[0056] An RFID chip is electrically connected to the double slot as part of the antenna assembly. This connection can be made either at the center of the double slot or offset from the center, providing flexibility in chip placement and potentially influencing the antenna's performance characteristics.

[0057] The method also incorporates several features to enhance the durability and security of the RFID tag. An anti-tampering mechanism is integrated, designed to induce damage to a fragile area of the conductive layer if an attempt is made to remove the tag from its tagged container. Additionally, the antenna is engineered to be resistant to various environmental factors, including heat, vibration, mechanical shock, and water. It is also designed to withstand home washing, broadening its applicability to items that may undergo regular cleaning. In some embodiments, the antenna is flexible and configured to be attached to concave or convex surfaces.

[0058] For added protection of the RFID chip, a protective hole is formed in the dielectric substrate layer, positioned directly beneath the chip. This feature provides mechanical protection, safeguarding the chip from physical stress or impact.

[0059] The method further includes applying a printable surface to the antenna, allowing for customization or additional information to be added to the tag. To facilitate easy application of the tag, an adhesive layer is applied to the underside of the dielectric substrate layer. Finally, a liner is adhesively attached to the underside of the dielectric substrate layer, protecting the adhesive until the tag is ready for use.

[0060] This comprehensive method results in an RFID tag antenna that offers superior performance across a wide range of applications, combining impedance stability, durability, and security features in a single, versatile design

[0061] FIG. 11 illustrates a graph showing that the antenna's read range performance is largely stable, despite variations in the material being tagged. The graph illustrates the performance of the RFID tag of the present subject matter across various dielectric materials. The X-axis represents the frequency sweep, while the Y-axis denotes the corresponding readactivation of the tag antenna. Several materials were tested, including metal, glass, rubber, plastic, and liquid, each with differing dielectric properties. Liquid (such as water) and metal represent two extreme ends among these materials. Liquid has a dielectric constant of approximately 80 and absorbs radio waves, while metal reflects radio waves and generates image currents that alter the antenna impedance. Nevertheless, the resonance remains consistent for the RFID tag as designed with a double and meander slot, demonstrating a satisfactory read range within the FCC frequency band.

[0062] As described hereinbefore and according to a preferred embodiment of the RFID tag of the present subject matter, the conductive layer of the RFID tag, which is essentially the antenna for the RFID tag, features a novel combination of a double slot structure and a plurality of meandered slots, which cooperatively provide impedance stabilization across a wide range of attachment surfaces and environments. The double slot structure consists of two distinct slots positioned strategically within the antenna design, potentially creating multiple resonant paths for current flow when exposed under a given Radio Frequency. This configuration broadens the antenna's bandwidth and provides multiple resonance points, offering greater flexibility in impedance matching, stabilization, or adjustment. The meandered slots, which are folded spatially in both machine and cross directions, increase the antenna's electrical length while maintaining a compact physical size. These meandered slots introduce inductive loading and allow precise tuning of the antenna's reactance. The synergistic interaction between the double slot structure and the meandered slots creates a distributed reactance network across the antenna surface, enabling the antenna to maintain a resonance frequency within the close range of a target frequency when attached to containers of varying materials (such as conductive materials, glass, plastic, or rubber) and contents with different permittivity (like liquids, meats or solids). This stability is achieved by creating multiple current paths and resonance points, compensating for impedance variations caused by different attachment surfaces. This design approach differs from prior art solutions that typically rely on a single antenna structure adapted for a specific substrate or a narrow range of materials. Instead, an embodiment uses the interplay between the double slot and meandered slots to create a more versatile and adaptable antenna and RFID Tag. Moreover, the antenna is designed to minimize any manufacturing complexity or additional costs associated with the antenna or its manufacturing tools.

[0063] The antenna is designed to operate in both the FCC and likely in ETSI frequency bands, making it suitable for global use. This dual-band capability is achieved by precisely tuning the dimensions and configurations of the slot.

[0064] To enhance the robustness and versatility of the RFID tag, several additional features may be incorporated, according to an embodiment:

[0065] 1. An anti-tampering mechanism to induce damage to a fragile area of the conductive layer upon removal of the tag from the tagged container. This ensures the security and integrity of the tagged items.

[0066] 2. An antenna that is engineered to be heat-resistant, vibration-resistant, mechanical shock-resistant, water-resistant, and home washing-resistant. These properties make it suitable for use in harsh industrial environments and consumer applications.

[0067] 3. A white printable surface may be applied to the antenna along the antenna substrate, allowing for custom printing or labeling as required by the end-user.

[0068] 4. A hole or a protective hole in the dielectric substrate layer may be positioned directly beneath the RFID chip to provide mechanical protection.

[0069] 5. An adhesive layer may be disposed on the side of the dielectric substrate layer opposite to the conductive layer, facilitating easy attachment to various surfaces.

[0070] 6. A liner may be adhesively attached to the underside of the dielectric substrate layer for protection during shipping and easy application.

[0071] The method for manufacturing this RFID tag antenna may involve several steps, according to an embodiment:

[0072] 1. Providing an antenna substrate, which could be of any polymeric material, such as PET.

[0073] 2. Forming a conductive layer on the antenna substrate layer, including creating the double slot structure and a plurality of meandered slots.

[0074] 3. Configuring the slots to stabilize impedance across various container materials and contents.

[0075] 4. Electrically connecting an RFID chip to the double slot.

[0076] 5. Incorporating a dielectric material.

[0077] 6. Incorporating additional features such as the anti-tampering mechanism, protective elements, and adhesive components.

[0078] Alternative embodiments may include variations in the dimensions and orientations of the slots, different substrate materials or thicknesses, and various combinations of the additional features described above. The specific configuration can be tailored to meet the requirements of different applications while maintaining the core principle of impedance stabilization across diverse materials.

[0079] In conclusion, this RFID tag antenna represents a significant advancement in RFID technology, offering a versatile and robust solution for tagging a wide range of items and containers. Its consistent performance across various materials and environmental conditions makes it particularly valuable for supply chain management, asset tracking, and inventory control applications in diverse industries.

[0080] As used herein, "machine direction" and "cross direction" are terms commonly used in manufacturing processes, particularly in industries involving sheet or web materials like paper, textiles, and, in this case, RFID tag production. These terms refer to the orientation of the material as it moves through the manufacturing process:

[0081] Machine direction refers to the direction in which the material moves through the manufacturing machine or production line. It refers to the longitudinal direction of the material. In RFID tags, machine direction typically refers to the length of the tag as it's produced in a continuous process. Cross direction refers to the direction perpendicular to the machine direction. It refers to the width of the material as it passes through the machine.

[0082] The orientation of slots and other antenna elements relative to the machine and cross directions can affect the antenna's performance characteristics. For example, the arrangement of meandered slots in both directions allows for more complex and effective impedance matching structures.

[0083] In the context of the RFID tag, the method specifies folding the meandered slots spatially into both the machine and cross directions. This approach likely allows for efficient use of space on the tag, creation of longer electrical paths in a compact area, and potentially different resonant characteristics in machine and cross directions, all of which may contribute to the tag's versatility across different materials and orientations

[0084] The terms "FCC" and "ETSI" as used herein refer to the following:

[0085] The FCC band refers to the UHF (Ultra-High Frequency) range of 902-928 MHz, regulated by the Federal Communications Commission in regions such as the United States, which allows for higher transmission power (up to 4 Watts EIRP) and longer read ranges.

[0086] The ETSI band refers to the UHF frequency range of 865-868 MHz, regulated by the European Telecommunications Standards Institute in Europe, with stricter power limits (up to 2 Watts EIRP) and listen-before-talk (LBT) requirements for interference management.

[0087] The descriptions above include examples of the claimed subject matter. It may be, of course, impossible to describe every conceivable combination of components or methodologies to describe the claimed subject matter. Still, one of ordinary skill in the art may recognize that many further combinations and permutations of the claimed subject matter are possible while remaining within the scope of the present disclosure. Accordingly, the claimed subject matter may be intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. An RFID tag comprising: a conductive layer disposed on a dielectric substrate layer, the conductive layer comprising: a double slot; and a plurality of meandered slots; wherein the RFID tag is adapted to be tagged into a range of containers of varying material and content with varying permittivity, the double slot and meandered slots being configured to cooperatively provide impedance stabilization, such that the tag maintains a resonance frequency within ±5% of a target frequency across the range containers and permittivity, thereby enabling effective operation on diverse attachment surfaces.

2. The RFID tag of claim 1, wherein the target frequency is the center frequency of the operational frequency band for the RFID tag.

3. The RFID tag of claim 2, wherein the operational frequency band is the FCC frequency band or the ETSI frequency band.

4. The RFID tag of claim 3, wherein the center frequency is approximately 915 MHz for operation in the FCC frequency band, or approximately 866.5 MHz for operation in the ETSI frequency band.

5. The RFID tag of claim 1, wherein the conductive layer is configured to operate as an antenna of the RFID tag6. The RFID tag of claim 1, wherein the RFID tag is configured to maintain a resonance frequency within ±3% of a target frequency across the range containers and permittivity, thereby enabling effective operation on diverse attachment surfaces.

7. The RFID tag of claim 1, wherein each of the meandered slot is folded spatially into machine direction and in cross direction.

8. The RFID tag of claim 1, wherein the meandered slots are larger in dimension than the double slot.

9. The RFID tag of claim 1, wherein the meandered slots are extended along the machine direction.

10. The RFID tag of claim 1, wherein the meandered slots extend, by length, beyond the double slot.

11. The RFID tag of claim 1, wherein the meandered slots are smaller in dimension than the double slot.

12. The RFID tag of claim 1, wherein the double slot extends, by width, beyond the double slot.

13. The RFID tag of claim 1, wherein the double slot extends along the machine direction.

14. The RFID tag of claim 1, wherein the double slot is placed between two meander slots along the cross direction.

15. The RFID tag of claim 1, wherein the double slot is placed between two meander slots along the machine direction.

16. The RFID tag of claim 1, wherein the double slot and the plurality of meander slots are co-planar.

17. The RFID tag of claim 1, further comprising an anti-tampering mechanism configured to induce damage to a fragile area of the conductive layer upon removal of the tag from the tagged container.

18. A method for stabilizing impedance in an RFID tag antenna, the method comprising: providing a dielectric substrate layer; forming a conductive layer on the dielectric substrate layer, wherein forming the conductive layer comprises: creating a double slot; and creating a plurality of meandered slots; configuring the double slot and meandered slots to cooperatively provide impedance stabilization for the RFID tag antenna being tagged into a range of containers of varying material and content with varying permittivity; adapting the double slot and meandered slots such that the antenna maintains a resonance frequency within ±5% of a target frequency across the range of containers and permittivity, thereby enabling effective operation on diverse attachment surfaces.

19. The method of claim 18, wherein the target frequency is the center frequency of the operational frequency band for the RFID tag antenna.

20. The method of claim 19, further comprising configuring the antenna to operate in the FCC frequency band or the ETSI frequency band.

21. The method of claim 19, wherein the center frequency is approximately 915 MHz for operation in the FCC frequency band, or approximately 866.5 MHz for operation in the ETSI frequency band.

22. The method of claim 18, wherein creating the plurality of meandered slots comprises folding the slots spatially into machine direction and cross direction.

23. The method of claim 18, further comprising: positioning the double slot between two meander slots along either the cross direction or the machine direction; and ensuring the double slot and the plurality of meander slots are co-planar.

24. The method of claim 18, further comprising configuring the antenna to operate in theFCC frequency band or the ETSI frequency band, or both.

25. The method of claim 18, further comprising electrically connecting an RFID chip to the double slot.

26. The method of claim 25, wherein the electrical connection between the RFID chip and the double slot is at the center of the double slot.

27. The method of claim 25, wherein the electrical connection between the RFID chip and the double slot is offset from the center of the double slot.

28. The method of claim 18, further comprising: incorporating an anti-tampering mechanism configured to induce damage to a fragile area of the conductive layer upon removal of the tag from the tagged container; and ensuring the antenna is heat resistant, vibration resistant, mechanical shock resistant, water resistant, and home washing resistant.

29. The method of claim 18, further comprising: forming a protective hole in the dielectric substrate layer positioned directly beneath the RFID chip to provide mechanical protection; applying a printable surface to the antenna; applying an adhesive layer to the underside of the dielectric substrate layer; and attaching a liner adhesively to the underside of the dielectric substrate layer.

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