Chipless RFID Tags

Abstract

The present invention relates to chipless (personalized) radio frequency identification devices (RFID), and more particularly to chipless (personalized) RFID tags, also known as chipless RFID tags.

Description

[Technical Field]

[0001] The present invention relates to chipless RFID tags, which are individualized radio frequency identification devices (RFIDs) that do not include a chip. [Background technology]

[0002] By "device" is meant packaging, documentation, especially security documentation, or any object incorporating a chipless RFID tag as claimed.

[0003] Data transmission systems using radio frequency identification technology are widely used to identify all types of objects and living organisms (animals, humans, etc.) carrying respective adapted devices (tags). In recent decades, RFID technology has been increasingly used for storing and transmitting information.

[0004] This RFID technology uses radio frequency tags placed on objects, also called transponders (a contraction of "transmitter" and "responder"), and readers, also called interrogators, to read and identify the radio frequency tags. RFID technology is generally categorized as either "active" or "passive" radio frequency tags. Active radio frequency tags typically have a relatively long transmission signal range because they have a local energy source (such as a battery) that they use to transmit a signal to the reader. Passive radio frequency tags, however, do not have an internal power source. This is because their signal transmission energy comes from the reader itself, specifically from receiving the signal transmitted by the reader. Therefore, passive radio frequency tags have a much smaller signal range, typically less than 8 meters.

[0005] From a practical standpoint, RFID technology uses radio frequency (RF) signals, which have much higher material penetration properties than optical signals. This allows RFID technology to be used in significantly more challenging environments than barcodes. For example, RFID tags can be read through all kinds of materials, including paper, cardboard, wood, paint, water, soil, dust, animal and human bodies, and concrete, as well as through the tagged item itself or its packaging. This property has led to a wide range of applications for RFID tags, including property and person identification, specifically packaging, automobiles (parking, tolls, etc.), inventory management, and electronic access cards. This also naturally includes all security documents, including payment instruments such as banknotes, checks, and restaurant coupons; identity documents such as ID cards, visas, passports, and driver's licenses; and lottery tickets, transportation tickets, and admission tickets to cultural and sporting events.

[0006] RFID tags can be broadly divided into two types: tags that contain an electronic integrated circuit, called an IC tag, and tags that do not contain an electronic integrated circuit, typically called chipless RFID tags.

[0007] An RFID tag (active or passive) typically comprises an antenna, electronic circuitry, and a memory for storing an identification code. The electronic circuitry is used, among other things, to receive the signal transmitted by the reader and to transmit a response in the form of a signal modulated in a specific frequency band and containing the identification code stored in the memory. In the case of passive RFID tags, part of the energy carried by the radio waves transmitted by the reader is used to power the chip.

[0008] The cost of IC RFID tags is not negligible due to the presence of electronic circuits within them. To reduce this cost, the applicant has proposed the development of chipless tags. This type of RFID tag does not require integrated circuits or discrete electronic components such as transistors, coils, capacitors, or antennas. It is the properties of the conductor geometry of this RFID tag that result in a specific behavior, specifically a resonator-type behavior. This resonant characteristic at a set frequency allows chipless RFID tags to be read directly on an object at a lower cost than conventional RFID tags.

[0009] A significant challenge to the prior art is increasing the coding capacity of chipless radio frequency identification devices and the manufacturing of these devices, particularly the industrial manufacturing of identification devices.

[0010] Non-Patent Document 1 proposes a retransmitting chipless tag based on a high-Q CSRR structure operating in the UWB frequency band. The tag consists of two orthogonally polarized microstrip wideband monopole antennas for transmitting and receiving, each equipped with multiple CSRR resonators. In Chapters 6 and 7, the experimental section of this paper, a Rogers 4350-type dielectric substrate is first used (dielectric constant: 3.66, loss tangent: 0.004, thickness: 0.508 mm). Tests are also conducted with substrates of various thicknesses (0.3 mm, 0.508 mm, and 0.8 mm, respectively). Next, the dielectric substrate is replaced with a plastic substrate (dielectric constant: 3.1, loss tangent: 0.008, thickness: 1 mm) and a foam substrate (dielectric constant: 1.06, loss tangent: 0.0015, thickness: 1 mm). The only conclusion drawn from these modifications is that the output spectrum correctly represents the coding state, with no other implications.

[0011] Non-Patent Document 2 presents a highly efficient microstrip patch antenna element developed as part of an EU research project on "green radio" technology. Figure 1 shows a stacked patch configuration coupled with a wideband aperture, with a substrate including three layers of Rogers Duroid 5880 and one layer of 10 mm thick foam. These antennas do not have the same functionality / practicality as the chipless tag of the present invention; therefore, the design issues are different.

[0012] Non-Patent Document 3 describes a "Dipole Array Plate Chipless RFID Tag with Large Encoding Capacity." The last paragraph of Section III on the topology of the 20-bit chipless RFID tag states that the substrate is composed of Rogers RO4350 (dielectric constant 3.66, loss tangent 0.003, thickness 0.1 mm) and a foam layer (dielectric constant 1.3, loss tangent 0.02, thickness 1 mm).

[0013] Non-Patent Document 4 describes a "chipless humidity sensor for wearable applications," that is, a humidity sensor for clothing.

[0014] Non-Patent Document 5 describes a scalar method for reading chipless RFID tags. Figure 9(a) of this document illustrates a chipless RFID tag equipped with a dipole resonator array. The dipole resonator array includes a ground plane with an intermediate layer, which is composed of an RO4350 substrate (Rogers-type dielectric, dielectric constant 3.66, loss tangent 0.003, thickness 0.1 mm) and a foam layer (dielectric constant 1.3, loss tangent 0.02, thickness 1 mm) inserted between the ground plane and the substrate.

[0015] While chipless RFID technology holds promise, there is currently room for improvement in the readability of chipless RFID tags. Readability refers to a tag's ability to be read and identified, i.e., to increase the tag's signal level (the desired signal carrying tag information) compared to other signals, such as measurement noise or signals backscattered by other objects in the tag's vicinity. To address the challenges of readability as well as tag manufacturing and cost, it is essential to apply certain treatments to the tag itself, particularly the materials that make up the tag. The materials used to manufacture the tag directly affect the desired signal backscattered by the tag. [Prior art documents] [Non-patent literature]

[0016] [Non-Patent Document 1] Zhong-Hua Ma, JianHong Yang, Chih-Cheng Chen, Cheng-Fu Yang, "Microsystems Technologies," 2018, Vol. 24, pp. 4373-4382 [Non-patent document 2] Peixeiro Custodio, "2013 IEEE Antennas and Propagation Society International Symposium (APSURSI)", Conference: July 7-13, 2013, IEEE Xplore: January 27, 2014, INSPEC Accession Number: 14058155, DOI: 10.1109 / APS.2013.6711573, pp. 1828-1829 [Non-patent document 3] Svanda Milan et al., "IEEE Access," Vol. 7, pp. 138707-138720, August 14, 2019, Electronic ISSN: 2169-3536, INSPEC Accession Number: 19088375, DOI: 10.1109 / ACCESS.2019.2935258 [Non-patent document 4] Laura Corchia et al., "2019 IEEE International Conference on RFID Technology and Applications (RFID-TA)," Conference Date: September 25-27, 2019, INSPEC Accession Number: 19135523, pp. 174-177 [Non-Patent Document 5] Jan Kracek, "Scalar Method For Reading of Chipless RFID Tags Based on Limited Ground Plane Backed Dipole Resonator Array," IEEE Transactions on Microwave Theory and Techniques, November 11, 2019, Vol. 67, pp. 4547-4558 Summary of the Invention [Problem to be solved by the invention]

[0017] Therefore, the present invention provides a promising solution to the above problems by proposing a new type of chipless (individualized) radio frequency identification device (RFID), specifically a chipless (individualized) RFID tag, also called a "chipless RFID tag." [Means for solving the problem]

[0018] The present invention A chipless RFID tag is a chipless RFID tag that does not have integrated circuits and discrete electronic components such as transistors, coils, capacitors, and antennas, One or more layers of conductive material conductor Dielectric substrate with pattern placed on it and the dielectric substrate having resonance characteristics has a relative permittivity of 1 to 2 measured at an arbitrary frequency of 3 to 10 GHz and a relative permittivity of 10 measured at an arbitrary frequency of 3 to 10 GHz. -3 has a loss tangent value smaller than It is characterized by:

[0019] As explained in more detail below, solid foam preferably refers to a dielectric material that contains a significant proportion of air or gas bubbles, and thus occupies a volume, but may be rigid or flexible, and contains little solid-state material. The solid state is preferably a state of matter characterized by a lack of freedom between molecules or ions, and thus foams are generally characterized by a very low dielectric constant, i.e., a dielectric constant of around 1, which is the dielectric constant value of air. [Effects of the Invention]

[0020] In fact, the applicant has unexpectedly discovered that the assembly of the dielectric and conductor pattern according to the present invention allows for devices that not only exhibit optimal resonance characteristics, but also excellent radiation efficiency and read performance. Therefore, the resonance characteristics of the device according to the present invention are determined by the combination of at least two layers: the dielectric and the conductor pattern. This discovery opens up a wide range of new applications in the field of chipless RFID tags, because, as shown herein, such devices are easily identifiable (while their RF signatures remain recognizable) and easy to manufacture. This is all the more unexpected and counterintuitive, since the prior art has known that maintaining the conductive properties of the tag surface is a manufacturing requirement for the tag to maintain a valid radio frequency signal. Furthermore, the prior art has known that the presence of a substrate with a high dielectric constant can improve the resonance ability of the tag (increasing the quality factor of the tag's resonator). In fact, the higher the dielectric constant of the substrate, the larger the electric field maintained at the location of the dielectric near the conductor layer, improving resonance (increasing the quality factor). On the other hand, when it comes to reader capabilities, a high quality factor is known as a fundamental criterion for reading tags in a real environment, i.e., an environment that contains other objects than the RFID tag. The higher the quality factor, the greater the chance of separating the signal transmitted by the tag from the surrounding signals in time. This allows for accurate measurement of the tag, which is what we actually aim for.

[0021] In the present invention, the use of the modifier "individualized" with respect to a claimed device / tag simply confirms that the device / tag is capable of being identified / distinguished. [Brief explanation of the drawings]

[0022] [Figure 1] 1A-1C are diagrams of various tag geometries made in accordance with the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0023] Dielectric Substrate As mentioned above, the chipless RFID device / tag according to the present invention is characterized by including a particular dielectric substrate.

[0024] This particular dielectric substrate is advantageously selected from among dielectric substrates that fulfill at least one of the following conditions: Bulk density of 250 kg m -3 smaller than, for example, 100 kg m -3 Less than and / or a dielectric constant less than 3, preferably less than 2, preferably less than 1.25. For example, the dielectric constant is less than 1.10. In one particular embodiment according to the invention, the dielectric constant is approximately 1. The dielectric constant is preferably greater than 1.001. For example, the dielectric constant is greater than 1.01, and / or Loss tangent value is 10 -2 smaller than 10, preferably -3 smaller than, say, 2 × 10 -4 is smaller than.

[0025] This particular dielectric substrate is advantageously chosen from among dielectric substrates made of solid foam, foam board, cardboard, cellular board or fabric (e.g., a material consisting of intertwined threads or fibers of cotton, hemp, flax or synthetic materials such as nylon, polyamide, viscose, etc.).

[0026] The dielectric substrate is advantageously rigid or flexible and is preferably provided in the form of a film.

[0027] The thickness of the dielectric substrate is advantageously greater than 0.1 mm, preferably greater than 0.5 mm, for example greater than 0.75 mm.

[0028] The thickness of the dielectric substrate is advantageously less than 3 mm, said thickness is preferably less than 1.5 mm, for example said thickness is less than 1.25 mm.

[0029] Any dielectric substrate that meets the performance goals of reading, resonance, and identification in accordance with the present invention may be used advantageously within the scope of the present invention, including, for example, fabrics (e.g., materials made from intertwined threads or fibers of cotton, hemp, flax, or synthetic materials such as nylon, polyamide, viscose, etc.), corrugated cardboard, cellular board, foam board, and solid foams such as polymers and biopolymers.

[0030] In one particular embodiment according to the invention, the dielectric substrate has a bulk density of 250 kg m -3 smaller than, for example, 100 kg m -3 Bulk density can be measured by any suitable method, such as weighing. Unless otherwise specified, bulk density is given for an object at normal atmospheric pressure (1,013 hPa) and a temperature of 20°C. Therefore, the measurement of this bulk density can advantageously be performed using the ASTM or ISO method applicable to the type of material selected for the dielectric substrate. Therefore, whether the method selected (and the method applicable to the type of material selected) is ASTM or ISO, the measured bulk density is preferably less than 250 kg m -3 smaller than, for example, 100 kg m -3 is smaller than.

[0031] In one particular embodiment according to the invention, the dielectric substrate is characterized by its dielectric properties, i.e. a relative permittivity of less than 3, preferably less than 2. The relative permittivity is less than 1.25. For example, the relative permittivity is less than 1.10. In one particular embodiment according to the invention, the relative permittivity is approximately 1. The relative permittivity is preferably greater than 1.001. For example, the relative permittivity is greater than 1.01.

[0032] In one particular embodiment according to the present invention, the dielectric substrate has a dielectric property, i.e., a loss tangent value of 10 -2 smaller than 10, preferably -3 smaller than, say, 2 × 10 -4 is characterized by being smaller than

[0033] The dielectric constant is a physical property that describes the response of a material when an electric field is applied. The loss tangent is also called the dielectric loss tangent.

[0034] The dielectric constant and loss tangent (tan δ) can be measured by any suitable method. Examples include the use of dielectric spectroscopy or resonant cavity methods, which are commonly used dielectric analysis techniques. These techniques are based on measuring the complex impedance of a sample at a specific frequency and, moreover, at a specific temperature. The present invention is directed to temperatures near ambient temperature (typically between -20°C and +80°C). In this temperature range, the dielectric constant and dielectric loss of dielectric materials commonly found around us can be considered relatively constant, especially over the bandwidth of interest, which is the ultra-low-temperature band of 3 to 10 GHz.

[0035] The above method makes it possible to obtain the dielectric constant value of a material, and also its loss factor tan δ, at a particular frequency. The values ​​given in this specification and the appended claims correspond to values ​​measured at a temperature of 20°C and at any frequency within the frequency range of 3 to 10 GHz.

[0036] Specifically, the values ​​shown in the following examples were measured using a Damaskos 08 model (thin plate tester - Cavity), which is excellent for evaluating the dielectric constant of dielectric substrates. This Damaskos thin plate tester also allows for non-destructive measurement of the loss tangent of dielectrics in the 800-4000 MHz band, which is particularly suitable for the substrates of this application. Measurements are performed using common vector and scalar analyzers controlled by Damaskos equipment, and data processing is performed using Damaskos' "Cavity" software, which has excellent reproducibility.

[0037] solid foam Solid foams (e.g., polymer foams) are used in many applications, such as thermal insulation, acoustic insulation, packaging, and the automotive industry. The foam can be likened to a continuous solid network containing trapped gas (usually air) bubbles. This trapped gas allows the properties of a foam (density, lightness) to be combined with those of a solid.

[0038] The solid foam may be advantageously characterized by its properties: density, closed or open cell structure, cell size and spatial arrangement.

[0039] Solid foams contain more than 90% gas (bulk density 100 kg m -3 foams with average density are those with a density between 100 and 600 kg m -3 Finally, a dense solid foam contains less than 60% gas, which is 600 kg m -3 Bulk density corresponds to a bulk density exceeding 1013 hPa. Bulk density can be measured by any suitable method, for example by weighing. Unless otherwise specified, bulk density is given for an object at normal atmospheric pressure (1,013 hPa) and a temperature of 20°C.

[0040] The solid foam used in the present invention preferably has a compressive strength of 250 kg m -3 For example, the solid foam has a bulk density of 100 kg m -3 It has a bulk density less than

[0041] The solid foam used in the present invention is preferably 10 4 ~10 9 pieces / cm 3 For example, the solid foam may have a cell density of 10 5 ~10 8 pieces / cm 3 The foam density is

[0042] The solid foam used in the present invention preferably has a cell size with an average diameter of 5 μm to 1 mm, for example, the solid foam has an average diameter of 20 to 200 μm.

[0043] Any material that provides the foam properties claimed in the present invention can be advantageously selected. Examples include foam board, polymers, or biopolymers. A polymer generally refers to an aggregate of macromolecules (molecules made up of many repeating subunits). Generally, if the molar mass of the material is greater than 2,000 g / mol, it is called a polymer.

[0044] In one particular embodiment according to the invention, the solid foam is a polymer foam, for example a polymer chosen among thermosetting polymers such as polyurethanes, epoxides, or preferably a polymer chosen among thermoplastics such as polystyrene, polyvinyl chloride, polypropylene, polyethylene, polyethylene terephthalate (PET), and / or mixtures of one or more of these polymers. Foams made of polyethylene (PE) or polyethylene terephthalate (PET) containing more than 80% by weight, for example more than 90% by weight, of gas are advantageously selected within the scope of the present invention.

[0045] The morphology of the foam, specifically the size and density of the cells, can be determined by any suitable method. For example, a foam (e.g., a polymer foam) is fractured under liquid nitrogen below the glass transition temperature of the polymer. The fracture surface is clean, the cells are not deformed, and can be observed under a microscope. A preferred electron microscope coupled to image analysis software capable of counting the number of cells is used. The image analysis software can also calculate the average surface area of ​​the cells per image. This allows the determination of the average cell diameter, or equivalent average diameter if the cells are not spherical. The cell density (1 cm 3 The number of bubbles per unit area is calculated using the formula (n / A) (3 / 2)where n is the number of bubbles in the image and A is the surface area of ​​the image.

[0046] Polymer foams can be prepared by any suitable method, including physical foaming by gas injection (such as CO or nitrogen (N)), or chemical foaming by the addition and decomposition of a blowing agent, such as 5-phenyltetrazole, p-toluenesulfonylsemicarbazide, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, pp-oxybis(benzene)sulfonylhydrazide, and / or azodicarbonamide, which are preferably used.

[0047] Blow extrusion processes are particularly suitable for making polymer foam films that may be used under the present invention.

[0048] Advantageously, nucleating agents can be added to the polymer, which also makes it possible to obtain small bubbles. Examples include inorganic fillers (e.g., stearic acid, calcium stearate, zinc stearate, calcium carbonate, magnesium silicate, talc, sodium benzoate, etc.), organic phases (e.g., elastomers, rubber particles, etc.), carbon black, and / or nanoparticles (e.g., nanoclays, carbon nanoparticles such as nanotubes, etc.).

[0049] In one particular embodiment according to the invention, the solid foam is selected from foam board, also known by the trade name Carton Plume. This type of material typically comprises three layers: a main inner layer of polymer foam (e.g., polystyrene, polyurethane, polyethylene, and / or polyethylene terephthalate (PET)), which is covered by a thin film of paper, plastic, or the like. The type of paper or plastic that forms the optional layer overlying the dielectric substrate on which one or more patterns of layers of conductive material are placed is not critical, since its thickness is negligible compared to the thickness of the solid foam, as will be explained in more detail below.

[0050] In general, and in one particular embodiment according to the invention, a dielectric substrate (e.g., solid foam, foam board, corrugated cardboard, cellular board and / or fabric, preferably solid foam) having the characteristics as described and / or claimed herein occupies at least 95% of the volume and / or 95% of the thickness and / or 95% of the weight of the entire dielectric substrate on which one or more patterns of layers of conductive material are disposed, and preferably occupies at least 99% of the volume and / or 99% of the thickness and / or 99% of the weight of the entire dielectric substrate on which one or more patterns of layers of conductive material are disposed. Accordingly, the present invention also relates to a chipless RFID tag consisting of a dielectric substrate on which is deposited a thin dielectric layer on which one or more patterns of layers of conductive material are disposed, said dielectric substrate itself having the characteristics as described and / or claimed herein. The thickness occupied by the thin dielectric layer (e.g. paper, paperboard or a film of plastic material, such as polyethylene (PE), polypropylene (PP) or preferably polyethylene terephthalate (PET)) is therefore advantageously less than 5% of the total thickness of the dielectric substrate, or even less than 1%.

[0051] While of course optional and not critical, applicant has determined that this thin dielectric layer or film provides many additional advantages to the claimed RFID tags if it meets certain preferred requirements.

[0052] First, it is important to note that the "associated" dielectric constant and loss tangent values ​​of the laminate dielectric of the claimed tag always have values ​​that satisfy the respective claimed characteristic values, and therefore, with respect to such criteria, the additional dielectric film has little effect on the dielectric assembly.

[0053] Next, and this is a great advantage in one embodiment according to the present invention, the applicant has recognized that the flatness and / or surface condition of the dielectric surface on which the conductor pattern is disposed can be an additional challenge in tag manufacturing. Indeed, it is often the case that the layer covering the main dielectric of the tag (e.g., solid foam, foam board, corrugated cardboard, cellular board and / or fabric, preferably solid foam) does not exhibit sufficient flatness and / or good surface condition, and better results / performance can be achieved by using an additional dielectric film, since this dielectric film specifically provided the required flatness and / or surface condition. In this way, better performance was obtained by disposing one or more patterns consisting of layers of conductor material directly on the dielectric film. Any suitable method can be used to characterize the flatness and / or surface condition of the conductor film. For example, to avoid the need for difficult-to-implement measures, the claimed tag is advantageously characterized in that the variation in its total thickness at all points is less than 100 μm, preferably less than 50 μm, for example less than 40 μm, less than 20 μm, less than 10 μm, or even less than 2 μm. Arranging one or more patterns of conductive material layers directly on the dielectric film can be achieved by any suitable method, as described below, for example, by printing, such as inkjet printing. The dielectric film covered with one or more patterns of conductive material layers can then be added to a main dielectric substrate (solid foam, foam board, corrugated cardboard, cellular board, and / or fabric, preferably solid foam) in any direction and in any order. The applicant has found it advantageous to stack the elements in the following order: (1) main dielectric substrate, (2) conductive patterns, and (3) dielectric film. This is because this stacking order advantageously protects the conductor pattern during handling and / or use of the tag, since the conductor pattern is simultaneously protected by the main dielectric substrate on one side and by the dielectric film on the other side.

[0054] In one particular embodiment, the dielectric film is characterized by one or more of the following features: a relative permittivity measured at any frequency between 3 and 10 GHz that is greater than the relative permittivity of the main dielectric substrate (solid foam, foam board, cardboard, cellular board and / or fabric, preferably solid foam), preferably greater than 1.25, for example greater than 2, preferably less than 3.5; and / or - the loss tangent value measured at any frequency between 3 and 10 GHz is greater than the loss tangent value of the main dielectric substrate (solid foam, foam board, cardboard, cellular board and / or fabric, preferably solid foam), and is preferably 2 x 10 -2 and / or a loss tangent value less than - at least one tenth the thickness of the main dielectric substrate (solid foam, foam board, cardboard, cellular board and / or fabric, preferably solid foam), preferably less than 100 μm, for example less than 50 μm; and / or - Consisting of a plastic material such as polyethylene, polypropylene or polyethylene terephthalate.

[0055] In one particular embodiment, the primary chemical makeup of the dielectric film is the same as the chemical makeup of the main dielectric substrate, for example, if the main dielectric substrate is polyethylene terephthalate foam, then the additional dielectric film is also polyethylene terephthalate-based.

[0056] paperboard As already explained, the dielectric substrate according to the present invention may be selected from, for example, corrugated cardboard or cellular structure board, such as B-flute corrugated cardboard (also called PC, generally having a thickness of 2.5 to 3.5 mm), E-flute corrugated cardboard (also called micro-flute corrugated cardboard, generally having a thickness of 2 to 1.5 mm), F-flute corrugated cardboard (also called mini-micro, generally having a thickness of about 1.2 mm), G-flute or N-flute corrugated cardboard (also called nano-flute, generally having a thickness of about 0.8 mm), O-flute corrugated cardboard (also called O-flute, generally having a thickness of about 0.5 mm), or a combination of two or more of the above corrugated cardboards.

[0057] The paperboard used in the present invention preferably has a strength of 250 kg m -3 For example, the paperboard has a bulk density of 100 kg m -3 It has a bulk density less than

[0058] In one particular embodiment according to the invention, a chipless RFID tag consisting of a dielectric substrate on which one or more patterns of layers of conductive material are deposited is characterized in that the upper side of the dielectric substrate is in contact with the one or more patterns of layers of conductive material. Indeed, in addition to the advantages of the flat / smooth surface of the upper side of the dielectric substrate mentioned above, the applicant has found it preferable that no other material is present between the layers (between the substrate / optional film / conductive patterns). For example, no adhesive is used between these parts of the tag.

[0059] Conductor layer As mentioned above, the chipless radio frequency identification device, preferably a chipless RFID tag, according to the present invention is characterized in that it consists of a particular dielectric substrate on which one or more patterns made of layers of conductive material are deposited. In this particular case specific to the present invention, the chipless radio frequency identification device, preferably a chipless RFID tag, also comprises one or more layers of conductive material underneath the dielectric substrate, preferably underneath the entire surface of the dielectric substrate. A configuration comprising two conductor layers (one underneath the dielectric substrate and one or more patterns on top of the dielectric substrate) is a particularly interesting case of the present invention (dielectric substrate sandwiched between two conductor layers), as will be explained below for tags with a ground plane.

[0060] In one particular embodiment according to the invention, the material of the conductor layer constituting the pattern comprises (or preferably consists of) a material selected from the group consisting of graphite, copper, nickel, silver, aluminum, platinum and / or combinations thereof, preferably copper and / or silver and / or aluminum.

[0061] In one particular embodiment according to the invention, the conductor layer constituting the pattern is characterized in that the thickness of the conductor material is greater than 100 nm. For example, a thickness greater than 150 nm is used. For example, a thickness greater than 200 nm is used. For example, a thickness greater than 250 nm is used. For example, a thickness greater than 300 nm is used. For example, a thickness greater than 400 nm is used. For example, a thickness greater than 500 nm is used.

[0062] In one particular embodiment of the present invention, the conductive layer constituting the pattern is characterized in that the thickness of the conductive material is less than 20 μm. The thickness of the conductive material is preferably less than 10 μm, or even less than 2 μm. For example, a thickness of less than 1.5 μm is used. For example, a thickness of less than 1 μm is used.

[0063] The layer of conductive material is deposited by any suitable deposition method, preferably directly onto the dielectric substrate or onto an optional dielectric film.

[0064] In one particular manufacturing method according to the present invention, the dielectric substrate is generally provided in the form of a film having rectangular or square dimensions, for example, a thick sheet or, in an optional embodiment using a dielectric film, a thin film. The sheet (or film) is generally moved into the printing machine by a substrate transport system along a transport path oriented along a longitudinal axis from at least one inlet store supplying the printable and / or individualizable substrate to at least one outlet store receiving the printed and / or individualized substrate, thus covered with a pattern of conductive material according to the present invention. The "side edges" of the substrate refer to the two edges located on either side of the longitudinal axis. The leading edge and / or trailing edge refer to the lateral edges of the substrate. The substrate can also be in the form of a reel in a roll-to-roll machine.

[0065] Examples of suitable methods for manufacturing the claimed devices / tags include conductive ink printing methods, particularly digital conductive ink printing methods, and more particularly on-demand inkjet digital conductive ink printing methods, which preferably use piezoelectric printheads.

[0066] An alternative suitable method for applying a pattern consisting of a layer of conductive material includes digitally printing a first pattern consisting of a printed material, preferably a dielectric material, such as ink, varnish, and / or toner. This digital printing step is followed by an application step, which involves overlaying an identical pattern consisting of a conductive film including an adhesive film on top of the first printed pattern. The adhesive film contacts the printed material and the conductive film. An example of a suitable method for printing the first pattern includes any digital printing method, particularly on-demand inkjet digital printing. This on-demand jet printing preferably uses a piezoelectric printhead. For example, the application step of the film to the first pattern is performed under pressure / temperature conditions that selectively bond the printed material and the adhesive film of the conductive film to each other, for example, by one or more pinch roller sets and / or one or more pressure rollers.

[0067] Another suitable alternative method for depositing a pattern of a layer of conductive material is by thermal transfer of the conductive material.

[0068] An alternative method suitable for tag production involves the sequential assembly of films. This method involves creating a conductor film (e.g., a cut-out aluminum layer, e.g., 5-20 μm thick), which can be attached to an optional carrier film (e.g., PET) before or after cutting, followed by a foam layer and then the conductor film (e.g., aluminum layer). These films / layers can be held together using a suitable adhesive, although wrapping or welding methods, as described below, are preferred because they eliminate the need for adhesive. From an illustrative perspective, this method corresponds to the production of a tag characterized by the creation of two "composite" layers and one cutting step. For example, one "composite" metal layer (the figure below shows an example of aluminum) "Aluminum / PET (with adhesive)" is created. -- Aluminum -- Thickness example: 5~20μm -- glue -- --PET-- This layer is then cut out to create the tag.Then the final remaining "composite" metal layer (the example below shows an example of aluminum) "foam / aluminum" must be created. -- Foam -- -- Aluminum -- Finally, these two composite layers must be assembled to form the tag. -- Aluminum -- Thickness example: 5~20μm -- glue -- --PET-- -- Foam -- -- Aluminum --

[0069] An alternative method suitable for manufacturing tags involves the creation of two "composite" layers and one chemical reaction step: First, a "composite" metal layer (the example below shows the case of aluminum) "Aluminum / PET" must be created. -- Aluminum -- Thickness 5 to 20 μm (tested at 12 μm) -- Adhesive -- (Optional) --PET-- A protective varnish is then applied and the tag is drawn onto the aluminum surface (the varnish only protects the aluminum used for the tag). This varnished layer is then immersed in a chemical bath that removes the aluminum not protected by the varnish, after which the final remaining "composite" metal layer (the example below shows an example for aluminum) "foam / aluminum" must be created. -- Foam -- -- Aluminum -- Finally, these two composite layers must be assembled to form the tag. An example of such successive layers is shown below: -- Varnish -- Equivalent to tag -- Aluminum -- Thickness 5~20μm, equivalent to tag -- Adhesive -- (Optional) --PET-- -- Foam -- --PET-- -- Adhesive -- (Optional) -- Aluminum --

[0070] It is also possible to envisage using cellophane tape / aluminium to create the tag: simply cut out the conductor pattern, which is then glued to a suitable specific substrate.

[0071] An alternative and preferred method for manufacturing the tag involves sequentially assembling the layers by rolling or welding the edges of each layer. The goal of this particular embodiment is to eliminate the need for adhesive between successive contact surfaces of the layers of the RFID tag while simultaneously ensuring intimate contact between said contact surfaces. Any means suitable for achieving these two goals may be advantageously used. The technique of rolling the layers and maintaining contact between their surfaces has been successfully tested. The technique of welding the edges of the layers (near the outer edges of the tag) has also been successfully implemented. By way of example, this welding may be advantageously performed by a roll-to-roll machine, in which the stacked layers of the tag are first wound onto a roll, then unwound from the roll and welded at the appropriate location for tag removal / assembly. It is not necessary to first cut out the main dielectric substrate (e.g., solid foam).

[0072] Thus, a chipless RFID tag constituting one preferred embodiment of the present invention comprises, from bottom to top: - consisting of an optional but preferred conductor layer, - thereon an optional but preferred dielectric film is placed, - thereon a main dielectric substrate is placed (for example solid foam, foam board, cardboard, cellular board and / or fabric, preferably solid foam), - on top of which is placed a dielectric film on which one or more patterns of layers of conductive material are arranged, said conductive patterns being able to be located on the upper side of the tag or advantageously between said main dielectric substrate and said dielectric film.

[0073] As mentioned above, the present invention relates to a device, preferably a tag, having resonant properties. In one particular embodiment according to the invention, the claimed tag is composed of a claimed dielectric substrate and a claimed conductor layer.

[0074] tag By way of example, a (personalized) chipless RFID tag according to the present invention has the following characteristics: one or a set of conductor patterns that characterize the geometry of the tag, preferably at least one or more or all patterns being asymmetric; an identifier comprising at least one resonance frequency fr and preferably at least one quality factor Q; Resonating in the ultra-wideband (UWB) frequency band, characterized by a bandwidth of 500 MHz or more, preferably 3.1 to 10.6 GHz; With or without a ground plane, Polarization, or preferably depolarization.

[0075] Tags - Geometry The encoding possibilities provided by the claimed method have also led the Applicant to develop a series of new tag families. Thus, in a particular embodiment, the tag is preferably configured with at least one pattern, preferably at least two asymmetric patterns. By way of example, FIG. 1 shows a ground plane tag specifically developed within the scope of the present invention. This figure shows four tags, each with six resonators. To optimize tag performance, two resonator families (dark grey double L-shapes and light grey double parallel lines with a 45-degree incline) are used. The frequency bands in which the respective resonant frequencies are located are indicated at the bottom left of each tag. The various geometries of each tag were developed in conjunction with the claimed method.

[0076] Tag - Identifier A tag according to the invention is preferably characterized in that it has an identifier comprising at least one resonance frequency fr and preferably at least one quality factor Q.

[0077] Resonant Tag Therefore, the tag according to the invention resonates in the ultra-wideband (UWB) frequency band, characterized by a bandwidth of 500 MHz or more, preferably between 3.1 and 10.6 GHz.

[0078] Passive Tags As already explained in the introduction, chipless radio frequency identification devices of the present type do not require integrated circuits or discrete electronic components such as transistors, coils, capacitors, antennas, etc. This type of device is therefore characterized by a passive operation, since it does not require the incorporation of a local power source (such as a battery).

[0079] It should be noted that "device" refers to packaging, documents, tags, especially security documents, or any object and / or living thing on which a chipless RFID identification marking can be carried or on which a carrier carrying an identification marking can be placed.

[0080] Tags with or without a ground plane Tags according to the invention can be characterized as having or not having a ground plane. In simplest terms, a tag with a ground plane according to the invention is defined as a structure characterized by a flat dielectric substrate, typically less than 3 mm thick and typically greater than 100 μm thick, sandwiched between two metal layers (a layer of conductor patterns resting on the dielectric substrate and another conductor layer located below the dielectric substrate).

[0081] By way of example, the thickness of the conductor layer underlying the substrate is advantageously chosen from the following thicknesses:

[0082] In one particular embodiment according to the invention, the conductive layer located below the substrate is characterized in that the thickness of the conductive material is greater than 100 nm. For example, a thickness greater than 150 nm is used. For example, a thickness greater than 200 nm is used. For example, a thickness greater than 250 nm is used. For example, a thickness greater than 300 nm is used. For example, a thickness greater than 400 nm is used. For example, a thickness greater than 500 nm is used.

[0083] In one particular embodiment according to the invention, the conductive layer located below the substrate is characterized in that the thickness of the conductive material is less than 20 μm, for example less than 10 μm, or even less than 2 μm, for example a thickness of less than 1.5 μm is used, for example a thickness of less than 1 μm is used.

[0084] In one particular embodiment of the present invention, the total thickness of the layers (conductor pattern-dielectric-conductor layer) is, for example, 0.1 to 3 mm.

[0085] With respect to tags, whether or not there is a ground plane, the term "ground plane" is often associated in the art with a metal layer that preferably corresponds completely to the surface of the substrate (located below the substrate).

[0086] In one particular embodiment according to the invention, the material of the conductor layer constituting the ground plane comprises (or preferably consists of) a material selected from the group consisting of graphite, copper, nickel, silver, aluminum, platinum and / or combinations thereof, preferably copper and / or silver and / or aluminum. In one particular embodiment according to the invention, the material of the conductor layer constituting the ground plane is different from or the same as the material of the conductor pattern, preferably the same.

[0087] The second metal layer (pattern) is made to represent a specific geometric shape (such as the pattern shown in Figure 1) that corresponds to the tag pattern. Thus, a tag with a ground plane has a structure with two metal layers, while a tag without a ground plane has only a single layer, namely the layer containing the tag pattern. A tag with a ground plane has the advantage that when placed with its ground plane side on an object, it is electromagnetically isolated from the object. In this case, the object has less influence on the tag than a tag without a ground plane.

[0088] It should be noted that a tag with a ground plane is a specific case of a tag that includes two metal layers sandwiched between the substrate. Indeed, in this preferred configuration, one of the two layers is preferably entirely metallized. However, intermediate tag configurations are possible. For example, there are tags with a ground plane in which openings are made in the ground plane side (removal of metal sections) to enable specific operations. This makes it possible, for example, to realize new resonances or modify existing resonances on the first conductor layer. The openings also have the effect of favoring the isolation of separate resonators on the second metal layer, thus improving the decoupling of these resonances and thereby improving tag reading performance.

[0089] The layer of conductive material of the ground plane may be deposited by any suitable deposition method, preferably directly onto the dielectric substrate, by way of example repeating the deposition methods described above for depositing the conductive pattern.

[0090] For cost reasons, chipless tags with two conductor layers and a dielectric layer in between can also be produced by wrapping the conductor layer around a substrate, e.g., by folding it. In this case, the conductor layer can have a surface at least twice the size of the substrate surface, typically the same length and at least twice the width. This surface can contain conductor patterns and / or ground planes, which, once produced, can be advantageously transferred to both sides of the dielectric layer in a single operation. This is possible by folding the conductor layer around. The only difference from the conventional approach (where two metal layers are transferred, one on each side of the dielectric) is whether the metal layer is on one or both sides of the dielectric. If this part is not metallized, there is no significant difference compared to the conventional approach. However, if this part (on one or both sides of the dielectric) can be metallized, more complex structures can be produced, which can improve the quality factor, as with the metal-walled cavities of the resonator. Therefore, those skilled in the art can take advantage of this structure, which requires fewer manufacturing steps and is therefore easier to manufacture. In fact, this latter approach reduces the number of technological steps to printing a single conductive medium, as well as gluing a single support.

[0091] In one particular application according to the invention, the dielectric substrate (with or without a ground plane) is selected from among commercially available materials used for thermal or acoustic insulation, the properties of which correspond to those claimed in the present invention, and the desired conductor patterns are placed directly on these commercially available materials.

[0092] Thus, the present invention is advantageously applicable to both ground planeless and ground plane tags.

[0093] Depolarization Tag The tag according to the invention is preferably characterized as being polarisable or preferably depolarisable. A depolarised tag is a tag that is able to emit a wave with a polarisation oriented perpendicular to the incident wave (cross polarisation will be explained below).

[0094] In one particular embodiment according to the present invention, the chipless RFID tag has a ratio of the total top surface of the dielectric substrate to the top surface of the dielectric substrate covered with a pattern of a layer of conductive material that is greater than two.

[0095] In one particular embodiment according to the present invention, the ground plane chipless RFID tag has a ratio of the bottom surface of the dielectric substrate covered with a layer of conductive material to the total bottom surface of the dielectric substrate greater than 0.9.

[0096] Leader By way of example, within the scope of the present invention, this reader is an electromagnetic wave transmitting / receiving reader, the working principle of which is based on the fact that it emits an electromagnetic signal in the direction of an identification device (e.g. a tag), which is reflected by said identification device according to its geometry (and for example its inherent resonance characteristics), and that once the reader captures the reflected signal, it processes the received signal (in particular in the decoding stage) and is thereby able to access the information contained in said device (e.g. a tag).

[0097] Thus, in general, the chipless radio frequency identification device according to the present invention is part of an RFID system, which also includes one or more RFID readers. The RFID reader may or may not be connected to a supervisory computer or to a processing electronic board capable of, for example, forming a link with an existing database. The reader is thus used to identify an object to which an RFID tag is attached using the RFID tag. The chipless RFID tag corresponds to a static radar target with a specific electromagnetic signature. In a specific embodiment of the present invention, the chipless RFID reader thus corresponds in operation to a radar, for example, an aviation radar that detects aircraft signatures within a certain magnitude-to-power ratio range. By way of example, the chipless RFID tag may be considered a radar target with a specific timing or frequency signature. Any type of radar suitable for receiving and identifying signals emitted and returned by an RFID tag may be advantageously used within the scope of the present invention. Examples include, but are not limited to, impulse radar.

[0098] The coding capacity obtained by the chipless radio frequency identification device according to the invention meets current standards, i.e. the resulting tag can carry at least 40 bits of information, which corresponds to an EAN13 type barcode. For example, for a credit card size, 40 bits [i.e. 40 / (85.60 x 53.98 mm) = 40 / 46 bits / cm]. 2 Thus, in one particular embodiment according to the invention, the claimed device has a coding capacity value of 0.85 bits / cm 2 greater than, say, 1 bit / cm 2 Greater than 2 bits / cm 2 even 5 bits / cm 2 is characterized by being larger than

[0099] In one variant of the invention, the claimed tag may be placed on any type of object and / or living thing (e.g., animal, human, etc.). In one variant of the invention, the object to which the tag is attached (preferably glued) may be chosen from a wide range of materials, non-limiting examples of which include metal, paper, fabric, plastics such as methacrylic copolymer resin, polyester, polycarbonate, polyethylene, polypropylene, and / or polyvinyl chloride, as well as cellulosic materials such as wood or plywood, or crystalline materials such as glass or ceramic, and composite materials containing one or more of the above components, such as milk cartons.

[0100] In one variant of the invention, the dielectric substrate of the claimed tag may be chosen from a wide range of materials, provided that it meets the requirements of one or more of claims 1 to 13. Non-limiting examples of these include paper, fabrics, plastics such as methacrylic copolymer resins, polyester, polycarbonate, polyethylene, polypropylene, and / or polyvinyl chloride, as well as cellulosic materials such as wood or plywood, or crystalline materials such as glass or ceramic, as well as composite materials containing one or more of the above components, such as milk cartons.

[0101] Various technical features and advantages are described herein with reference to drawings and / or various embodiments. As will be understood by those skilled in the art, technical features of a particular embodiment may in fact be combined with features of other embodiments, unless expressly indicated to the contrary, or unless the incompatibility of the features is clear, or unless the combination does not provide a solution to at least one of the technical problems described herein. Furthermore, technical features described in a particular embodiment may be separated from other features of that embodiment, unless expressly indicated to the contrary.

[0102] It will be apparent to those skilled in the art that the present invention allows for embodiments in many other specific forms without departing from the scope of the invention as defined in the claims. The embodiments of the present invention should therefore be considered as illustrative, but modifiable within the scope defined by the appended claims, and the invention should not be limited to the details given above.

[0103] Example Packaging Materials - Features Polymer film, thickness 1mm Bulk density: 60kg / m 3 Measured relative permittivity: 1.036 (at 3.21 GHz), 1.035 (at 3.89 GHz) Measured loss tangent: 1.9×10 -5 (at 3.21GHz), 3.7×10 -5 (at 3.89GHz).

[0104] Using off-the-shelf packaging material with the above properties as the dielectric substrate, a ground plane tag was constructed with the following characteristics: - a 10 μm thick aluminum layer beneath the entire surface of the substrate, - A conductor pattern similar to that in Figure 1, made of aluminum and 10 μm thick.

[0105] These tags are characterized by having different identifiers and a larger quality factor.

[0106] In one particular embodiment according to the present invention, the chipless RFID tag, in turn, - an optional but preferred conductor layer having a thickness between 200 nm and 20 μm, for example less than 10 μm or even less than 2 μm, - thereon is placed an optional but preferred dielectric film having a thickness of 5 to 100 μm, - thereon a main dielectric substrate (e.g. solid foam, foam board, cardboard, cellular board and / or fabric, preferably solid foam) having a thickness of 0.5 to 3 mm is placed, - on top of which is deposited a dielectric film having a thickness of 5 to 100 μm, on which one or more patterns of layers of conductive material are arranged, each having a thickness of 200 nm to 20 μm, for example less than 10 μm, or even less than 2 μm.

[0107] This RFID tag is also advantageously characterized in that the width and length dimensions of all layers (excluding the conductor patterns, of course) are close to those of a credit or bank card: by way of example, these dimensions are preferably 86±2 mm in length and 54±2 mm in width (more precise preferred dimensions are 85.725 mm x 53.975 mm).

Claims

1. A chipless RFID tag that does not have integrated circuits and discrete electronic components such as transistors, coils, capacitors, and antennas, comprising a dielectric substrate on which one or more conductor patterns made of a layer of conductive material are mounted, the dielectric substrate having resonance characteristics having a relative permittivity of 1 to 2 measured at any frequency between 3 and 10 GHz and a relative permittivity of 10 or less measured at any frequency between 3 and 10 GHz. -3 A chipless RFID tag having a loss tangent value less than

2. 2. The chipless RFID tag according to claim 1, wherein the dielectric substrate has a relative dielectric constant of 1.001 to 1.

25.

3. The loss tangent value is 2 x 10 -4 3. The chipless RFID tag according to claim 1, wherein the chipless RFID tag has a capacitance smaller than 100 Ω.

4. The bulk density of the dielectric substrate is 250 kg m -3 The chipless RFID tag according to any one of claims 1 to 3, characterized in that it is smaller than

5. The chipless RFID tag according to any one of claims 1 to 4, characterized in that the dielectric substrate has a dielectric film mounted thereon, and one or more of the conductor patterns made of a layer of the conductor material are disposed on the dielectric film.

6. The dielectric film has the following characteristics: - said dielectric constant measured at any frequency between 3 and 10 GHz being greater than the dielectric constant of said dielectric substrate; and / or a loss tangent value measured at any frequency between 3 and 10 GHz that is greater than the loss tangent value of the dielectric substrate; and / or a thickness at least ten times smaller than that of said dielectric substrate, and / or The chipless RFID tag of claim 5, characterized by one or more of the following: - being made of a polyethylene, polypropylene or polyethylene terephthalate plastic material.

7. The chipless RFID tag of any one of claims 1 to 6, characterized in that the top side of the dielectric substrate is in contact with the one or more conductor patterns made of the layer of conductive material.

8. The chipless RFID tag according to any one of claims 1 to 7, wherein the thickness of the dielectric substrate is greater than 0.5 mm.

9. The chipless RFID tag according to any one of claims 1 to 8, wherein the thickness of the dielectric substrate is less than 3 mm.

10. 10. The chipless RFID tag according to claim 1, wherein the conductor layer constituting the conductor pattern has a thickness of conductor material greater than 200 nm and less than 20 μm.

11. 11. The chipless RFID tag according to claim 1, wherein the conductor layer constituting the conductor pattern has a thickness of the conductor material that is greater than 400 nm and less than 2 μm.

12. The chipless RFID tag with ground plane according to any one of claims 1 to 11, comprising a layer of said conductive material below said dielectric substrate.

13. 13. The chipless RFID tag of claim 12, wherein the layer of conductive material beneath the dielectric substrate has a thickness greater than 200 nm and less than 20 μm.

14. 13. The chipless RFID tag of claim 12, wherein the layer of conductive material beneath the dielectric substrate has a thickness greater than 400 nm and less than 2 μm.

15. 15. The chipless RFID tag of claim 1, wherein the dielectric substrate is selected from the group consisting of solid foam, foam board, corrugated board, cellular structure board, and dielectric substrates made of fabric.

16. 16. The chipless RFID tag of claim 15, wherein the dielectric substrate is a solid polymer foam.

17. The dielectric substrate has a cell density of 10 4 ~10 9 pieces / cm 3 17. The chipless RFID tag of claim 16, wherein the tag is a solid polymer foam having a

18. The chipless RFID tag according to any one of claims 1 to 17, characterized in that the dielectric substrate is a solid polymer foam having a cell size of 20 to 200 μm in average diameter.

19. The chipless RFID tag according to any one of claims 1 to 18, characterized in that the ratio of the entire top surface of the dielectric substrate to the top surface of the dielectric substrate covered with the conductor pattern made of the layer of conductor material is greater than 2.

20. 20. The chipless RFID tag with ground plane according to claim 12, wherein the ratio of the bottom surface of the dielectric substrate covered with the layer of conductive material to the overall bottom surface of the dielectric substrate is greater than 0.

9.

21. In order, - composed of conductor layers, - a first dielectric film is placed on top of the conductor layer, - the dielectric substrate is placed on top of the first dielectric film, A chipless RFID tag according to any one of claims 1 to 4, characterized in that a second dielectric film on which one or more conductor patterns made of a layer of conductor material are arranged is placed on the dielectric substrate, the layer of conductor material being in contact with the top surface of the dielectric substrate.

22. the conductor layer has a thickness between 200 nm and 20 μm, - on the conductor layer, the first dielectric film is placed, the thickness of which is between 5 and 100 μm, - the dielectric substrate having a thickness of 0.5 to 3 mm is placed on the first dielectric film, 22. The chipless RFID tag of claim 21, characterized in that the second dielectric film having a thickness of 5 to 100 μm is placed on the dielectric substrate, and the second dielectric film has arranged thereon one or more conductor patterns made of a layer of the conductor material having a thickness of 200 nm to 20 μm.

23. 23. A method for manufacturing a chipless RFID tag according to any one of claims 1 to 22, characterized in that the edges of each layer of the tag are rolled or welded together to keep the layers of the tag in contact without bonding.

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