Antenna for RFID tag

Abstract

An antenna for use in an RFID tag, said antenna comprising a core, a metal wire or cable and a protective jacket wherein said core comprises a textile made of a polymer or organic material and preferably consists of a textile made of a polymer or organic material, the metal wire or cable is coiled or spiraled around the antenna core in a Z or S direction to form a composite structure, and the protective jacket is made of one or more winding layers around the composite structure and comprises a textile made of a polymer or organic material, and preferably by a textile made of a polymer or an organic material.

Description

Technical Field

[0001] The present invention relates to the field of antennas suitable for RFID (Radio Frequency Identification) tags. The present invention also relates to RFID tags including such an antenna, and the RFID tags can be attached to objects, such as laundry items, such as clothes and sheets used in hospitals or hotels, or, for example, pneumatic rubber tires for motor vehicles at different locations. Background Art

[0002] WO2014 / 204322A1 discloses an RFID tag particularly suitable for use as a linen or laundry tag. The RFID tag in a specific embodiment includes a backing layer, a first adhesive layer covering the backing layer, an RFID transponder chip and an antenna covering the first adhesive layer, and a second adhesive layer covering the RFID transponder chip and the antenna. These layers are laminated together to hermetically seal the RFID transponder chip and the antenna within the RFID tag. In a preferred embodiment, the antenna includes an elongated multi-strand stainless steel wire, for example having 49 strands. The diameter of the wire is preferably between 0.3 mm and 0.5 mm and is encapsulated in nylon or other polymer insulating materials. It has been mentioned that it has been found that a multi-strand wire structure with a diameter of 0.3 mm - 0.5 mm and having 49 strands has sufficient flexibility and is less prone to kinking than prior art antennas. The antenna can be stitched to the reinforcing adhesive layer before lamination. The stitching can include cotton thread, polyester-cotton thread or other substantially durable threads, and preferably holds the antenna in place in combination with the reinforcing adhesive layer during lamination and during subsequent use of the RFID tag.

[0003] WO2017 / 060222A1 discloses an RFID tag, particularly an antenna for an RFID tag. The antenna includes an antenna yarn made of metal fibers. The metal fibers are stainless steel fibers. The antenna yarn is wound by at least one winding yarn so as to cover the entire surface of the antenna yarn or a metal wire or a bundle of metal wires. The at least one winding yarn includes non-conductive fibers.

[0004] It has been found that due to the incompatibility between the antenna wire and the embedded system, the RFID antenna wire may break under various stresses. These embedded systems do not allow the antenna to move freely when stressed, so the antenna is subject to a large amount of stress. This may cause damage or failure of the RFID tag and render the RFID tag inoperable or unusable. Summary of the Invention

[0005] The object of the present invention is to provide an improved RFID antenna with high durability.

[0006] A specific object of the present invention is to provide an improved RFID antenna that provides desired properties in an embedded RFID system. Here, the embedded system can be rubber, epoxy resin, composite material, or other housing.

[0007] According to a first aspect of the present invention, there is provided an antenna for an RFID tag. The antenna includes a core, a metal wire or cable, and a protective sleeve. Wherein, the core includes a fabric made of a polymer or organic material, and preferably consists of a fabric made of a polymer or organic material. The metal wire or cable is wound or spiraled around the antenna core in the Z or S direction to form a composite structure. The protective sleeve is made of one or more winding layers around the composite structure, and the protective sleeve includes a fabric made of a polymer or organic material, and preferably consists of a fabric made of a polymer or organic material.

[0008] According to the present invention, the fabric of the core or the protective sleeve can be in the form of yarn, wire, multifilament, or monofilament. The core or the protective sleeve includes a polymer selected from polyester, polyamide, polyimide, (para- or meta-) aramid, liquid crystal polymer (LCP), or a material with the trademark The equivalent diameter of the textile core is in the range of 0.10 mm to 0.30 mm, and the linear density is in the range of 110 dtex to 2000 dtex. Preferably, the textile core exists as filaments arranged in a parallel untwisted arrangement. This means that the filaments are not twisted or cabled, so that the filaments are substantially parallel to each other and substantially parallel to the axis of the antenna yarn. Due to the low bending stiffness of this core, it better absorbs the stress that the final product may undergo.

[0009] The metal wire or cable can be made of stainless steel, etched copper, or aluminum. Preferably, the metal wire or cable is made of stainless steel fibers (for example, stainless steel filaments), and the stainless steel fibers have an equivalent diameter of less than 20 microns, preferably less than 15 microns (such as 14 microns or 12 microns). The equivalent diameter of a fiber with a non-circular cross-section is the diameter of a circle having the same area as the cross-sectional area of the fiber with a non-circular cross-section. Preferably, the metal wire includes or consists of stainless steel filaments; the twist is less than 200 turns / meter, more preferably less than 150 turns / meter, and even more preferably less than 120 turns / meter. As an example, the metal cable is made of multiple single filaments with a diameter greater than 25 microns, or made of a bundle of ultra-fine wires with a diameter less than 25 microns (that is, the diameter of a single wire is less than 25 microns). For example, the metal cable can be a bundle of 275 stainless steel filaments with a diameter of 12 microns twisted 100 turns per meter of the antenna yarn length.

[0010] The preferred stainless steel fibers are manufactured by the bundle drawing method. The stainless steel fibers can exist as filaments (a filament refers to a fiber of virtually infinite length); or the stainless steel fibers can exist as fibers of discrete length. Preferably, the stainless steel fibers have a polygonal, more preferably hexagonal cross-section.

[0011] Preferably, the stainless steel fibers - whether fibers of discrete length or filaments - have an equivalent diameter of less than 20 microns, preferably less than 15 microns; for example, an equivalent diameter of 14 microns or 12 microns. Preferably, the stainless steel fibers - whether fibers of discrete length or filaments - are prepared by the bundle drawing process, resulting in a typical polygonal cross-section of the stainless steel fibers or filaments.

[0012] Preferably, the martensite weight percentage of the stainless steel fibers is less than 5%, preferably less than 3%, more preferably less than 2%, more preferably less than 1%, more preferably less than 0.35%, more preferably less than 0.25%, more preferably less than 0.1%. Even more preferably, the stainless steel fibers do not contain martensite.

[0013] For the present invention, stainless steel refers to a steel grade containing at least 10.5% by weight of chromium. Preferably, the stainless steel is a 300 series or 200 series stainless steel conforming to ASTM A240, such as alloy 316 or alloy 316L. Preferably, the stainless steel fibers are made of an alloy containing: at least 12% by weight of nickel and at least 16% by weight of chromium; and preferably between 2% - 2.5% by weight of molybdenum. Even more preferably, it is an alloy having the same specifications as alloy 316L but with a modified nickel content (between 12% - 15% by weight), a modified chromium content (between 17% - 18% by weight), and a modified molybdenum content (between 2% - 2.5% by weight).

[0014] Preferably, the stainless steel fibers are made of a stainless steel alloy containing between 12% - 15% by weight of nickel, between 17% - 18% by weight of chromium, between 2% - 2.5% by weight of molybdenum, less than 0.03% by weight of carbon, and less than 0.1% by weight of nitrogen. This alloy is preferred because it has a small amount of martensite in the end-drawn microstructure of the bundle-drawn fibers.

[0015] Preferably, the stainless steel fibers comprise or are made of high nitrogen austenitic stainless steel (HNASS). High nitrogen austenitic stainless steel alloy is a stainless steel alloy with a nitrogen content greater than 0.4% by weight. The HNASS steel grade remains fully austenitic during wire drawing or bundle fiber drawing processes; no strain-induced martensite is formed during the drawing process.

[0016] A first example of the HNASS steel grade useful in the present invention contains 0.2% carbon by weight, 17% chromium by weight, 0.05% nickel by weight, 0.53% nitrogen by weight, 3.3% molybdenum by weight, and 10.50% manganese by weight.

[0017] A second example of the HNASS steel grade useful in the present invention contains 0.08% carbon by weight, 21% chromium by weight, 0.3% nickel by weight, 1% nitrogen by weight, 0.7% molybdenum by weight, and 23% manganese by weight.

[0018] The stainless - steel fibers can be present in the antenna as filaments; or the stainless - steel fibers can be present in the antenna as fibers of discrete length. A filament is a stainless - steel fiber of virtually infinite length. A metal cable containing stainless - steel filaments can be provided as a bunch of twisted parallel filaments, or as a multi - strand (e.g., two - strand) twisted or cabled yarn. Fibers of discrete length are fibers that have a finite length and in most cases have a length distribution. An antenna yarn made of fibers of discrete length can be manufactured by a yarn - spinning process (e.g., ring - spinning). A wire or cable made of fibers of discrete length can be a single - layer yarn or a multi - strand (e.g., two - strand) yarn.

[0019] The stainless - steel fibers for use in the present invention, whether filaments or fibers of discrete length, can be prepared according to the bundle - drawing method as described in US - A - 2050298. The bundle - drawn fibers have a characteristic polygonal cross - section. Preferably, the equivalent diameter of the bundle - drawn stainless - steel fibers for use in the present invention is greater than 4 microns, preferably greater than 10 microns; and preferably less than 30 microns, more preferably less than 20 microns; even more preferably less than 15 microns.

[0020] Single - end - drawn stainless - steel filaments can also be used in the present invention. Such filaments have a circular cross - section in most cases. Preferably, the cross - section of the single - end - drawn stainless - steel filaments is greater than 40 microns and preferably less than 100 microns, such as 50 microns, 60 microns, or 80 microns. An example is a cable composed of 24 stainless - steel filaments with a diameter of 50 microns twisted together at 100 turns / meter.

[0021] The composite structure according to the present invention has a "helical" structure, which includes a textile core around which a metal wire or cable is wound in a defined pattern. As an example, the "defined pattern" can be defined such that the metal wire or cable can be wound around the textile core with a defined fixed pitch length. For example, the pitch length can be in the range between 0.1 cm and 5 cm, preferably in the range between 0.5 cm and 3 cm, and most preferably in the range between 0.8 cm and 2 cm. Alternatively, the textile core can be completely covered by the metal wire or cable. In addition, the metal wire or cable can be in the form of a strip, i.e., multiple wires or cables are adjacent to each other to form a strip. Such a strip of metal wire or cable can be wound around the textile core with a fixed defined pitch length. The strip shape can be maintained during processing, and there are no intersection points or overlaps of the metal wire or cable. It is designed such that the textile core absorbs most of the stresses that the final product may undergo. In other words, it increases the mechanical properties of the final product. These stresses are mainly tensile stresses, stresses caused by torsion, stresses caused by pressure, stresses caused by bending, etc. The structure can also have some "anti-slip" properties to enable the correct winding of the metal antenna wire.

[0022] A metal wire or cable is provided to achieve the antenna function of the antenna. The metal wire or cable "spiraling" around the central textile core is ideally a very durable and corrosion-resistant wire / filament cable that has good reading performance in the radio frequency spectrum.

[0023] It has been noted that the metal wire or cable can cause compaction of the textile core, reducing its diameter. The wound metal wire or cable itself is also very thin. The compaction is more obvious when using a textile core with a low twist (low twist: for example, less than 200 turns / meter, or even less than 150 turns / meter, or even less than 120 turns / meter) or when using a non-twisted textile core. The low-twist textile core or non-twisted textile core has a certain bulkiness. The metal wire or cable compresses and compacts the textile core.

[0024] The composite structure is wound by at least one winding layer so as to cover the entire surface of the core, the metal wire or the metal cable. The at least one winding layer comprises a non-conductive material and is preferably made of a non-conductive material. Compared with the prior art extrusion-coated antenna, the at least one winding layer of the wound composite structure creates an alternative electrical insulation for the antenna. The beneficial technical effect of using the at least one winding layer is that a thinner antenna with a lower bending stiffness can be obtained compared to the prior art version of the extrusion-coated antenna. In extrusion coating, a certain minimum coating thickness is required to ensure that the entire antenna surface is covered with an insulating coating. This is especially important when the antenna yarn has an irregular surface; the entire surface needs to be coated. The result after extrusion coating is a rather thick antenna. In addition, compared with the coated antenna, the winding layer results in much less increase in bending stiffness. The protective sheath ensures that the metal wire or cable is electrically insulated, it adds additional protection to the metal antenna cable, and may increase the adhesion to the embedded system (rubber, epoxy resin, composite material, etc.) by having a higher specific surface area available for increasing adhesion. The protective sheath structure will also absorb any stress formed by elongation, bending, pressure, etc. The diameter of the composite structure can be between 0.25 mm and 0.45 mm, while the diameter of the antenna with the protective sheath can be in the range of 0.30 mm to 0.70 mm.

[0025] According to the present invention, the protective sheath can consist of one or more textile winding layers. These textile windings can be carried out in the S, Z directions or a combination of the S and Z directions. The textile can be (but not exclusively) any textile, ranging from polymer-based yarns, wires, multifilaments, monofilaments, etc., i.e., polyester, polyamide, polyimide, (para- or meta-) aramid, LCP, etc., to organic materials in yarns, wires, multifilaments, monofilaments, i.e., cotton, linen, etc.

[0026] Depending on the properties of the textile used, the diameter of the material used for the protective winding ranges from any value between 0.10 mm and 0.30 mm, corresponding to a decitex range of 110 decitex to 2000 decitex, increasing the diameter of the final product to a maximum of 0.70 mm. Each of the at least one winding material can be wound around the composite structure at a rate of more than 1000 turns per meter of antenna length.

[0027] The protective sheath of the antenna can be coated with, for example, a rubber-metal adhesive or resorcinol formaldehyde latex (RFL) with the trade name The adhesive can be a mixture of polymers, organic compounds and mineral fillers dissolved or dispersed in an organic solvent system. The said adhesive is used to construct a rubber-metal adhesive system.

[0028] As an example, one or more of the winding yarns are multifilament yarns, or spun fiber yarns, or monofilaments. Preferred multifilament winding yarns are texturized multifilament yarns, such as polyester multifilament yarns. More preferred are non-tangled texturized multifilament yarns, as they provide the best coverage.

[0029] Preferably, each of the winding yarns in at least one winding yarn is wound around the antenna yarn at a rate of more than 1000 turns per meter of the composite structure length; more preferably, it is wound around the antenna yarn at a rate of more than 2000 turns per meter of the composite structure length. One or more winding yarns can be, for example, one or more tapes.

[0030] In a preferred embodiment, at least one winding yarn is at least one tape. A tape is a specific type of monofilament yarn: the tape has a substantially flat cross-section, showing a thickness and a width. For the present invention, the tape used preferably has an aspect ratio of the cross-section of at least 10, preferably at least 15. Preferably, the aspect ratio of the tape is less than 50, more preferably less than 35. Preferably, the winding of the tapes does not overlap, but rather they contact each other in subsequent winding turns. Such tapes of polyester, polyamide, polyolefin (such as polyethylene or polypropylene) can be used. However, polyester tapes are preferred because they have an interesting combination of properties. Preferred tapes have a cross-section with a thickness between 10 microns and 40 microns, more preferably between 10 microns and 25 microns, even more preferably between 12 microns and 25 microns. Preferably, the width of the cross-section of the tape is at least 100 microns, more preferably at least 200 microns, even more preferably at least 300 microns. Preferably, the width of the tape is less than 500 microns. Specific examples of the cross-section of the tape (such as a polyester tape) that can be used in the present invention are, for example, 250 microns × 12 microns, 350 microns × 12 microns, 370 microns × 12 microns, and 250 microns × 23 microns.

[0031] The winding direction of the yarn is indicated by the capital letter S or Z. If when the wound yarn is held vertically, the winding helix slopes in the same direction as the middle part of the letter S, the winding is in the S direction. If when the wound yarn is held vertically, the winding helix slopes in the same direction as the middle part of the letter Z, the winding is in the Z direction.

[0032] As an example, preferably the winding yarn winds the composite structure in the S direction. More preferably, the multifilament winding yarn winds the composite structure in the S direction, more preferably the deformed multifilament winding yarn winds the composite structure in the S direction, and more preferably the non-tangled deformed multifilament winding yarn winds the composite structure in the S direction. More preferably, the multifilament winding yarn winds the composite structure in the S direction at a rate greater than 1000 turns per meter of the composite structure length, and more preferably at a rate greater than 2000 turns per meter of the composite structure length. Preferably, the winding yarn winds the composite structure in the Z direction. More preferably, the multifilament winding yarn winds the composite structure in the Z direction, more preferably the deformed multifilament winding yarn winds the composite structure in the Z direction, and more preferably the non-tangled deformed multifilament winding yarn winds the composite structure in the Z direction. More preferably, the winding yarn winds the composite structure in the Z direction at a rate greater than 1000 turns per meter of the antenna yarn length, and more preferably at a rate greater than 2000 turns per meter of the antenna yarn length.

[0033] In a preferred antenna, the winding yarn winds the composite structure in the S direction; and the winding yarn winds the composite structure in the Z direction. In such an example, each winding yarn can be a tape. Preferably, the number of turns per meter length of the winding in the S direction is the same as the number of turns per meter length of the winding in the Z direction. The winding yarn can wind the composite structure at a rate greater than 1000 turns per meter of the antenna length. More preferably, it winds the composite structure at a rate greater than 2000 turns per meter of the antenna length. The manner of winding in the Z direction and the S direction around the axis of the composite structure is to wind some of the winding yarns in the S direction around the axis of the composite structure and some of the winding yarns in the Z direction. The advantage of the described example is that a more stable antenna is obtained. Preferably, the antenna includes the same number of winding yarns wound in the S direction as in the Z direction, resulting in optimal stability of the antenna and enhancing the coverage of the composite structure. For example, the metal filaments are wound by an equal number of winding yarns, with half of the winding yarns winding the metal filaments in the S direction and the other half winding the metal filaments in the Z direction. The advantage is the stability of the antenna.

[0034] A second aspect of the present invention is an RFID tag including a transponder chip and an antenna as in the first aspect of the present invention. The antenna is coupled to the transponder chip. The antenna can be inductively coupled to the transponder chip.

[0035] Preferably, the RFID tag includes a transponder chip and two antennas as in the first aspect of the present invention. For example, each of the two antennas is coupled to the transponder chip; the antenna can be inductively coupled to the transponder chip. Preferably, the included angle between the two antennas is 180°.

[0036] A third aspect of the present invention is a component including an inflatable rubber tire for a motor vehicle and an RFID tag as in the second aspect of the present invention. The RFID tag includes a transponder chip and an antenna according to the present invention, wherein the antenna is coupled to the transponder chip. A protective sleeve of the antenna of the RFID is embedded in the inflatable rubber. Due to the winding process, the protective sleeve is not firmly attached to the spiral structure, but is firmly enough to remain on the spiral structure. This construction of the protective sleeve enables it to have protective properties under stress conditions. Due to the properties of the protective sleeve (due to the characteristics of textile winding), good adhesion between the protective sleeve and the embedded system can be obtained. This enables the embedded system not to adhere to the metal wire / cable, so it only "adheres" to the protective sleeve. The RFID antenna cable of the present invention is electrically insulated by the protective sleeve, so that the RFID tag can be immediately integrated into the tire without having to be first covered with a non-conductive material and without the need to do so before being manually loaded into, for example, non-conductive rubber.

[0037] The RFID tag of the present invention can have a carrier or substrate facilitating RFID processing (such as being embedded in inflatable rubber). The transponder chip can be fixed to the textile fabric (as the carrier or substrate), for example, by a laminated foil or by an epoxy resin drop or by an adhesive. One or more antennas can be fixed to the textile fabric by one or more stitching yarns. The antenna of the present invention is developed for RFID solutions with mechanical coupling or inductive coupling.

[0038] Preferably, the RFID tag is fixed to the textile fabric such that the antenna forms a loop with overlapping ends on the textile fabric. The transponder chip can be present on the fabric inside the loop with overlapping ends.

[0039] Preferably, the antenna is fixed to the textile fabric such that the antenna undulates on the textile fabric. Preferably, the antenna is fixed to the textile fabric by one or more than one stitching yarn. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A cross-section of an antenna for an RFID tag according to the first aspect of the present invention is shown.

[0041] Figure 2 A cross-section in a plane passing through and along the axis of an antenna for an RFID tag according to the first aspect of the present invention is shown.

[0042] Figure 3 A textile fabric and an RFID tag fixed to the textile fabric are shown. DETAILED DESCRIPTION

[0043] Figure 1 A cross-section 100 of an exemplary antenna for an RFID tag according to the first aspect of the present invention is shown.Figure 2 Figure 200 shows a cross-section in a plane passing through and along the axis of an exemplary antenna for an RFID tag according to the first aspect of the present invention.

[0044] A high-performance multifilament yarn spun from liquid crystal polymer (e.g., trademarked or para-aramid filaments (e.g., trademarked is used as the textile core 110 to fabricate the exemplary RFID antenna. Preferably, the linear density of the core is 440 decitex. The core is wound with a bundle of drawn stainless steel filaments of equivalent diameter 12 μm of 316L stainless steel conforming to ASTM A240 standard. A parallel bundle of 275 stainless steel filaments is twisted at 100 turns per meter to obtain a twisted yarn. The twisted yarn 120 is wound around the core 110 in the S direction or Z direction to form a composite structure.

[0045] The composite structure is insulated by a protective sheath 125 made of polyester. Preferably, a polyester yarn of linear density 76 decitex or 167 decitex is applied. More preferably, two winding layers are applied. The composite structure is wound with a non-entangled texturized polyester multifilament yarn of 76 decitex (= 7.6 tex) in the S direction and Z direction. The winding is completed at 2250 turns per meter of antenna length. The wound non-entangled texturized polyester multifilament yarn covers the entire surface of the composite structure.

[0046] Figure 3 A substrate is shown, such as a textile fabric 330 and an RFID tag 340 fixed to the textile fabric. The RFID tag 340 includes a transponder chip 350 and an antenna 360 as in the first aspect of the present invention. The antenna 360 is disposed in a wavy shape on the textile fabric and forms a loop 365 with overlapping ends in the middle of its length. The antenna 360 is inductively coupled to the transponder chip 350. The RFID tag 340 is fixed to the textile fabric substrate. The antenna 360 is fixed to the textile fabric 330 by one or more stitching yarns 370. The transponder chip 360 is fixed to the textile fabric by, for example, a transparent laminate foil 355. Alternatively, the transponder chip can be fixed to the textile fabric by, for example, an epoxy drop or an adhesive.

[0047] The above RFID tag is embedded in pneumatic rubber and exhibits improved bending and fatigue life.

[0048] In this example, 316L stainless steel fibers are used; however, other stainless steel grades can also be used for the present invention.

[0049] Instead of the non-entangled texturized multifilament winding yarn, other yarns or tapes can be used as the winding fiber material for the protective sheath.

[0050] Although a protective cover wound in both the S direction and the Z direction is preferred, in the present invention, winding in only one direction (S or Z) may be used.

Claims

1. An antenna for use in an RFID tag, the antenna comprising a core, a metallic wire or cable, and a protective sheath, wherein the core comprises a textile made of a polymer or organic material and preferably consists of a textile made of a polymer or organic material, the metallic wire or cable being wound or helically coiled around the core of the antenna in a Z or S direction to form a composite structure, and the protective sheath being made of one or more winding layers surrounding the composite structure, and the protective sheath comprising a textile made of a polymer or organic material and preferably consisting of a textile made of a polymer or organic material.

2. The antenna for use in an RFID tag according to claim 1, wherein, The textile of the core or the protective sheath is in the form of yarns, wires, multifilaments or monofilaments.

3. The antenna for use in an RFID tag according to claim 1 or 2, wherein, The core or the protective sheath comprises a polymer selected from polyester, polyamide, polyimide, (para- or meta-) aramid or liquid crystal polymer (LCP).

4. An antenna for use in an RFID tag according to any one of the preceding claims, wherein, The core or the protective sheath comprises an organic material selected from cotton or linen.

5. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, The textile core has an equivalent diameter in the range of 0.10 mm to 0.30 mm and / or has a linear density in the range of 110 decitex to 2000 decitex.

6. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, The metallic wire or cable is made of stainless steel, etched copper or aluminum.

7. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, The metallic cable is made of a plurality of monofilaments with a diameter greater than 25 microns or a bundle of ultra-fine wires with a diameter less than 25 microns.

8. An antenna for use in an RFID tag according to any one of the preceding claims, wherein, The composite structure has a diameter between 0.25 mm and 0.45 mm.

9. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, The antenna has a diameter in the range of 0.30 mm to 0.70 mm.

10. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, Each of at least one winding material is wound around the composite structure at a rate of more than 1000 turns per meter of antenna length.

11. The antenna for use in an RFID tag according to any one of the preceding claims, wherein, The protective sheath is coated with a rubber-metal adhesive or resorcinol formaldehyde latex (RFL).

12. An RFID tag, comprising a transponder chip and an antenna according to any one of the preceding claims, wherein, The antenna is mechanically coupled or inductively coupled to the transponder chip.

13. An inflated rubber tire for a motor vehicle, comprising the RFID tag according to claim 12, wherein, The protective sheath of the antenna of the RFID is embedded in an inflatable rubber.

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