Chipless radiofrequency identification (RFID) tags

Abstract

The present invention relates to a chipless RFID tag. The present invention relates more particularly to a compact chipless RFID tag with a high coding capacity. The present invention also relates to a set of compact chipless RFID tags with a high coding capacity, for example a strip of tags or the corresponding roll thereof.

Description

[0001] Title of Invention: Chipless Radio Frequency Identification (“RFID”) Tags

[0002] The present invention relates to a chip-less RFID tag. The present invention relates more particularly to a compact and high-coding capacity chip-less RFID tag. The present invention also relates to a set of compact and high-coding capacity chip-less RFID tags, for example a strip of tags or its corresponding reel.

[0003] These tags will advantageously be included in chipless radio frequency identification devices (called "RFID", with "RF" designating radio frequency); by "device" is meant a package, a document, in particular a security document as well as possibly any object comprising a portion of the strip comprising at least one chipless RFID tag.

[0004] Data transmission systems using radio frequency identification technology are commonly used to identify all types of objects and living beings (e.g., animals or humans) carrying a suitable device (tag). RFID technology has become increasingly widespread in recent decades as a device for storing and transmitting information.

[0005] This RFID technology uses a radio tag, also called a transponder (from the English "transponder", a contraction of the words "transmitter" and "responder"), which is placed on an object, and a reader, also called an interrogator, to read and identify the radio tag. RFID technologies are generally classified into categories using "active" or "passive" radio tags. Active radio tags have a local power source (such as a battery) through which they send a signal to the reader; they are therefore generally characterized by a relatively long transmitted signal range.On the other hand, passive radio tags do not have an internal power source because their signal transmission energy comes from the reader itself, and in particular from the reception of the signal emitted by the reader; thus, passive radio tags have a much lower signal range, generally less than 8 meters.

[0006] From a practical point of view, RFID technology uses radio frequencies ("RF") which have much higher material penetration characteristics than optical signals. Thus, in comparison with barcode labels, RFID technology will allow use in much more hostile environmental conditions; for example, RFID tags can be read through any kind of material such as paper, cardboard, wood, paint, water, dirt, dust, animal or human body, concrete or even through the tagged item itself or its packaging. This has opened up a wide range of applications for RFID tags, including, for example, the identification of goods and people, in particular packaging, cars (parking, tolls, etc.).), inventory management, electronic access cards, not forgetting all security documents such as, for example, a means of payment, such as a banknote, a check or a restaurant voucher, an identity document, such as an identity card, a visa, a passport or a driving license, a lottery ticket, a transport ticket or even an entry ticket to cultural or sporting events.

[0007] There are mainly two types of RFID tags: tags comprising an integrated electronic circuit, known as chip (electronic) tags, and tags not comprising an integrated electronic circuit, generally referred to in the art as "chip-less RFID tags".

[0008] RFID chip tags (active or passive) generally include an antenna, an electronic circuit, and a memory for storing an identification code. The electronic circuit is used to receive the signal emitted by the reading terminal and to transmit in response, in a specific frequency band, a modulated signal containing the identification code stored in the memory. For passive RFID chip tags, part of the energy carried by the radio waves emitted by the reading terminal is used to electrically power the chip.

[0009] Due to the presence of electronic circuits (such as the RFID chip or the antenna part) in smart RFID tags, these tags have a significant cost. It is in particular to reduce this cost that it has been proposed to produce tags without a chip or antenna. This type of chipless RFID tag therefore requires neither integrated circuit nor discrete electronic components, such as for example a transistor and / or a coil and / or a capacitor and / or an antenna; it is their conductive geometric characteristic that generates a specific behavior, in particular of the resonator type. This resonance characteristic at a given frequency makes it possible to print chipless RFID tags directly on an object at lower costs than traditional RFID tags.

[0010] Among the different families of chipless tags, they can be differentiated by the presence or absence of an RF antenna at the tag level. Classically, like RF systems, this antenna's role is to recover part of the EM wave emitted by the reader, to convert it into a guided wave at the tag level so that it is conducted through a filter which will give the tag's code. This filtered signal, and therefore including the identifier ("ID"), will be re-emitted towards the reader, most often with a second antenna which plays the same role as the first but by performing the reverse process. These RFID tags have been used mainly to make a chipless proof of concept, however in application terms they are very limited. The antennas are bulky and lead to significantly increasing the size of the tag.Likewise, the antenna is generally very sensitive to its immediate environment, this can completely mismatch it, meaning that it will no longer be able to convert the radiated wave into a guided wave to power the filter. This results in a loss of efficiency of the tag, including a significant reduction in the reading distance when these tags with antenna are positioned on objects. To address these problems, chipless RFID tags without antenna, still based on the same principle of information coding, appeared in the 2010s, as illustrated in the following publications.

[0011] E. Perret, S. Tedjini, V. Deepu, A. Vena, F. Garet and L. Duvillaret, Patents published under the numbers FR2956232 (Bl) and US8556184 (B2); and VENA, Arnaud, PERRET, Etienne, and TEDJINI, Smail. Chipless RFID based on RF encoding particle: realization, coding and reading system. Elsevier, 1st Edition - August 2, 2016.

[0012] The major difference with the tags that are the subject of the present invention, sometimes called REP (for "RF encoding particle"), is linked to the fact that they do not involve different RF blocks, namely an antenna part, an RF transmission line part, a filter part, but simply resonant RF patterns that make it possible to code the identifier on the basis of the resonance frequencies that they contain. These tags are artificial radar targets designed to resonate at specific frequencies and which are compatible with the possibility of encoding an identifier ("ID") but also of finding the ID of the tag from the acquisition of the signal backscattered by the tag.

[0013] Increasing the coding capacity of chipless radio frequency identification tags is a major challenge in the state of the art. Although chipless RFID technology has a bright future, the fact remains that we are still looking to improve the reading performance of chipless RFID tags. By reading performance we mean the ability of the tag to be read and identified, for example, the increase in the signal level of the tag (useful signal carrying the tag's information) compared to other signals such as measurement noise or signals backscattered by other objects close to the tag. Specific work on the tag itself, particularly its geometry, compactness and the materials it is made of, is essential to address the issue of reading performance as well as the manufacturing and cost of these tags.

[0014] As an illustration, the prior art can be represented by the article by VENA, Arnaud, PERRET, Etienne, and TEDJINI, Smaii, entitled “A compact chipless RFID tag using polarization diversity for encoding and sensing.” [published in 2012 IEEE International Conference on RFID (RFID). IEEE, 2012. p. 191-197] which describes a chipless RFID tag that exploits the advantage offered by polarization diversity to encode more information in a given area size. The tag comprises 3 split-ring resonators with variable air gap configuration. Depending on the linear polarization used, different resonance modes can be measured for the same resonator to increase the coding capacity.

[0015] The article by Feng, C., Zhang, W., Li, L., Han, L., Chen, X., & Ma, R. (2015), titled “Angle-based chipless RFID tag with high capacity and insensitivity to polarization.” [published in IEEE Transactions on Antennas and Propagation, 63(4), 1789-1797] presents a chipless radio frequency identification (RFID) tag with high capacity and insensitivity to polarization. Its diffuser is designed to be V-shaped with two diagonals of equal length. The tag encodes data using the angle between the two diagonals of the V and is identified by measuring the field in two orthogonal polarization directions.

[0016] The fact remains that improving the coding capacity in combination with the objective of making the label compact remains a significant challenge to which the present invention responds advantageously as explained in the remainder of the description of the present invention.

[0017] US 2022 / 0083748 describes the search for a positioning and the identification of a 3D object in a mass from at least one resonator.

[0018] Statement of the invention

[0019] Thus, the present invention provides a promising solution to this problem by proposing a chip-less RFID tag. In the context of the present invention, the term "personalized" is often assigned to the tags because this confirms that the identification / discrimination of said tag is possible.

[0020] Label

[0021] In particular, the present invention relates to a chipless radio frequency identification tag comprising a planar geometric pattern of n resonators made of conductive material, n being greater than or equal to 3, the resonators being V-shaped whose respective length of each diagonal of the V is pL and (lp)L with 0 < p < 1 per resonator and L being the cumulative length of the two diagonals of a resonator, with an angle a between the diagonals of the V of the resonators substantially identical, a bisector of the V-shaped resonators substantially identical, and characterized in that at least one value of p of a resonator is different from 0.5.

[0022] As will be demonstrated by way of illustration in the exemplary embodiments of the invention, this type of label fully meets the dual objective of compactness and coding capacity of the labels which are the subject of the present invention.

[0023] The term "diagonal" used herein to denote the arms of the character V comes from the typographic glossary and the corresponding anatomy of the letter V.

[0024] The expression "angle a between the diagonals of the V of the resonators substantially identical" used in the present invention to characterize the V-shaped resonators can alternatively be replaced by the fact that the resonators are V-shaped with two parallel diagonals two by two between the resonators.

[0025] The radio frequency identification tag of the invention is chipless. As already explained in the introductory part, the chipless radio frequency tag therefore requires neither an integrated circuit nor discrete electronic components, such as for example a transistor and / or a coil and / or a capacitor and / or an antenna. This tag is therefore characterized by passive behavior because it will not have to integrate a local energy source (such as a battery); the same is preferably true of the identification device integrating said tag.

[0026] It is thus the conductive geometric characteristic of the label which generates a specific behavior, notably of the resonator type as explained in the rest of the description.

[0027] The present invention therefore relates to a chipless radio frequency identification tag comprising a planar geometric pattern of n resonators made of conductive material, n being greater than or equal to 3, the resonators being V-shaped whose respective length of each diagonal of the V is pL and (lp)L with 0 < p < 1 per resonator and L being the cumulative length of the two diagonals of a resonator, with an angle a between the diagonals of the V of the resonators being substantially identical, a bisector of the V-shaped resonators being substantially identical, and characterized in that at least one value of p of a resonator is different from 0.5.

[0028] The angle α formed by the diagonals of the V of the resonators is substantially identical. Those skilled in the art of producing chipless radio frequency identification tags understand that the term "substantially" applied to the angle α formed by the diagonals of the V of the resonators stems from the precision of the manufacturing method of said tag and the tolerance in this area. A tolerance of 5%, preferably 1%, or even 0.1%, will be possible around the desired angle α value of said resonators. For illustration purposes, if the desired angle α is 120°, angles between 114° and 126° will be tolerated, even if it will be preferable to maintain this tolerance between 118.8 and 121.2 degrees, or even between 119.88 and 120.12 degrees; a precise production at 120° being ideally preferred.

[0029] The bisector of the V-shaped resonators is substantially identical. Those skilled in the art of making chipless radio frequency identification tags understand that the term "substantially" as applied to the bisector of the diagonals of the V of the resonators stems from the precision of the method of manufacturing said tag and the tolerance therein. A precise realization with a single common bisector is ideally preferred.

[0030] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the majority of the V-shaped resonators have p values ​​different from 0.5.

[0031] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the majority of the V-shaped resonators have different p values ​​from each other.

[0032] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the p values ​​of the V-shaped resonators are between 0.05 and 0.95.

[0033] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the distance on the bisector between each intersection of the diagonals of two successive V-shaped resonators is less than 1 cm, for example less than 0.5 cm.

[0034] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that at least two values ​​of L are different.

[0035] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the majority of the resonators are different.

[0036] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the angle a between the diagonals of the V of the resonators is different from 90°. This advantageously makes it possible to obtain a field coverage of 180 degrees with a single family of at least 3 resonators according to the invention.

[0037] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the angle a between the diagonals of the V of the resonators is substantially equal to 120°, for example equal to 120°.

[0038] The present invention also relates to a chipless radio frequency identification tag comprising a planar geometric pattern comprising at least two families, for example three families, of n resonators made of conductive material, n being greater than or equal to 3 in each family, the resonators being V-shaped whose respective length of each diagonal of the V is pL and (lp)L with 0 < p < 1 per resonator and L being the cumulative length of the two diagonals of a resonator in each family, with an angle a between the diagonals of the V of the resonators substantially identical in each family, with a bisector of the V-shaped resonators substantially identical in each family, and characterized in that at least one value of p of a resonator is different from 0.5 in each family.

[0039] In a particular embodiment of the present invention, when the chipless radio frequency identification tag comprising a planar geometric pattern comprises more than two families, for example three families of n resonators made of conductive material, the bisectors of the families preferably intersect at the same point.

[0040] In a particular embodiment of the present invention, when the chipless radio frequency identification tag comprising a planar geometric pattern comprises several families of n resonators made of conductive material, for example three families, said tag has in each family one, two or more or all of the following characteristics:

[0041] - the majority of V-shaped resonators have p values ​​different from 0.5;

[0042] - the majority of V-shaped resonators have different p values ​​between them;

[0043] - the p values ​​of V-shaped resonators are between 0.05 and 0.95;

[0044] - the distance on the bisector between each intersection of the diagonals of two successive V-shaped resonators is less than 1 cm, for example less than 0.5 cm;

[0045] - at least two values ​​of L are different;

[0046] - the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the majority of resonators are different;

[0047] - the angle a between the diagonals of the V of the resonators is substantially equal to 120°, for example equal to 120°.

[0048] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention consists of three families of resonators as described above, each family having an angle α between the diagonals of the V of the resonators substantially equal to 120°, for example equal to 120°, with the bisectors of the families preferably intersecting at the same point.

[0049] In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention has an area equal to or less than 11000 mm 2 ; this surface can advantageously be equal to or less than 7770 mm 2 , or even equal to or less than 4620.7 mm 2 . In a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention has an area equal to or greater than 375 mm 2; this surface can advantageously be equal to or greater than 3000 mm 2 .

[0050] For illustrative purposes, the chipless radio frequency identification tag of the present invention has a dimension close to that of a typical bank card format (credit cards, debit cards, ATM cards, etc.), namely an ID-1 format of 85.60 mm x 53.98 mm; some driver's licenses also have very similar sizes.

[0051] Although the bank card-sized label is preferred, it is obvious that the label dimensions can be either larger or smaller; for example, twice as large or half as small.

[0052] For illustrative purposes, the chipless radio frequency identification tag of the present invention has a dimension close to that of an ID-2 format with dimensions of the order of 105 mm x 74 mm, an ID-3 format with dimensions of the order of 125 mm x 88 mm, or an ID-000 format with dimensions of the order of 25 mm x 15 mm.

[0053] Although it is preferable to reduce the size of the label from a compactness point of view, the person skilled in the art will have to find a compromise in order to maintain the desired coding capacity.

[0054] Figures

[0055] [Fig.l] Figure 1 represents an example of a label and, in particular, of a label geometry produced in connection with the invention

[0056] [Fig. 2] Figure 2 represents an example of a label and, in particular, of a label geometry produced in connection with the invention

[0057] [Fig. 3] Figure 3 represents an example of a label and, in particular, of a label geometry produced in connection with the invention

[0058] [Fig.4] Figure 4 represents an example of a label and, in particular, of a label geometry produced in connection with the invention

[0059] [Fig.4] Figure 5 represents an example of a label and, in particular, of a label geometry produced in connection with the invention

[0060] [Fig.4] Figure 6 represents an example of a label and, in particular, of a label geometry produced in connection with the invention Label

[0061] By way of illustration, the chipless RFID tag according to the present invention has the following characteristics: o A conductive pattern or a set of conductive patterns characterizing its geometry, preferably with at least one or more or all of the asymmetric patterns, o An identifier which comprises at least one resonance frequency fr and, preferably, at least one quality factor Q, o Resonant in an ultra-wide frequency band (ULB) characterized by a bandwidth greater than or equal to 500 MHz, preferably between 3.1 and 10.6 GHz, and o With or without a ground plane, preferably with a ground plane.

[0062] Label - Geometry

[0063] As an example, Figure 1 is a simplified representation of a chipless radio frequency identification tag comprising a planar geometric pattern of 3 V-shaped resonators made of conductive material; these 3 V-shaped resonators have a substantially identical angle which is approximately 120° between the diagonals of the V and an identical angular positioning in the plane (3 vertical diagonals at 90° (or 270°) relative to a horizontal of the plane and 3 diagonals at 120° (or 300°) relative to a horizontal of the plane (these angles can easily be measured in a virtual trigonometric circle by taking as the center of the circle the intersection of the two diagonals of a V); the positioning of the resonators in the plane is arranged in such a way that the bisector of the V-shaped resonators is substantially identical (this bisector would therefore pass through the center of the virtual trigonometric circle mentioned above).In particular, it can be seen that the values ​​of L and p of the three resonators are selected so that the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the resonators are different (approximately 100°, 120° and 140° in this graphical representation). Thus, in a particular embodiment of the present invention, the chipless radio frequency identification tag of the present invention is also characterized in that the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the majority of the resonators are different.

[0064] As an example, Figure 2 is a simplified representation of a chipless radio frequency identification tag comprising a planar geometric pattern of 3 families of 3 V-shaped resonators made of conductive material; in each family, the 3 V-shaped resonators have a substantially identical angle which is approximately 120° between the diagonals of the V and an identical angular positioning in the plane with respect to a horizontal of the plane; in each family, the positioning of the resonators in the plane is arranged so that the bisector of the V-shaped resonators is substantially identical; it can be seen that the positioning in the plane of the three families is arranged so that the three bisectors of the three families preferably intersect at the center of the virtual trigonometric circle in which the tag is inscribed;we can also see that the resonators are positioned in such a way as to minimize the dimensions of said virtual circle.;

[0065] As an example, Figure 3 is a simplified representation of a chipless radio frequency identification tag comprising a planar geometric pattern of 3 families of 4 V-shaped resonators made of conductive material.; in each family, the 4 V-shaped resonators have a substantially identical angle which is approximately 120° between the diagonals of the V and an identical angular positioning in the plane relative to a horizontal of the plane; in each family, the positioning of the resonators in the plane is organized so that the bisector of the V-shaped resonators is substantially identical; it can be seen that the positioning in the plane of the three families is organized so that the three bisectors of the three families preferably intersect at the center of the virtual trigonometric circle in which the label is inscribed; it can also be seen that the resonators are positioned so as to minimize the dimensions of said virtual circle.

[0066] As an example, Figure 4 is another simplified representation of a chipless radio frequency identification tag comprising a planar geometric pattern of 3 families of 3 V-shaped resonators made of conductive material; in each family, the 3 V-shaped resonators have a substantially identical angle which is approximately 120° between the diagonals of the V and an identical angular positioning in the plane with respect to a horizontal of the plane; in each family, the positioning of the resonators in the plane is arranged so that the bisector of the V-shaped resonators is substantially identical; it can be seen that the positioning in the plane of the three families is arranged so that the three bisectors of the three families preferably intersect at the center of the virtual trigonometric circle in which the tag is inscribed;we can also see that the resonators are positioned in such a way as to minimize the dimensions of said virtual circle.;

[0067] Label - Identifier

[0068] The tag according to the present invention will preferably be characterized by an identifier which comprises at least one resonance frequency fr and at least one quality factor Q.

[0069] Resonant Label

[0070] The tag according to the present invention is therefore resonant in an ultra-wide frequency band (ULB) characterized by a bandwidth greater than or equal to 500 MHz, preferably between 3.1 and 10.6 GHz.

[0071] Passive Label

[0072] As already explained in the introductory part, our type of chipless radio frequency identification device therefore does not require an integrated circuit or discrete electronic components, such as a transistor and / or a coil and / or a capacitor and / or an antenna. This type of device is therefore characterized by passive behavior because it will not need to integrate a local energy source (such as a battery).

[0073] The label can therefore easily characterize a package, a document, a label, in particular a security document as well as possibly any object and / or living being on which the marking of the identification by RFID without chip can be carried out or on which a marking support can be attached.

[0074] Label with or without ground plane

[0075] The label according to the present invention can be characterized in that it has or does not have a ground plane. In its simplest expression, a label with a ground plane according to the present invention is defined as a structure comprising a flat dielectric substrate with a thickness generally less than 3 mm and generally greater than 100 μm sandwiched between two metal layers (the layer of the conductive pattern surmounting the dielectric substrate and the other conductive layer located under the dielectric substrate).

[0076] By way of illustration, the thickness of the conductive layer (located under the dielectric substrate when the patterns consisting of a layer of conductive material are located above said dielectric substrate) will advantageously be selected from the following thicknesses.

[0077] In a particular embodiment according to the present invention, the conductive layer located under the substrate is characterized by a thickness of conductive material greater than 100 nm. For example, a thickness of more than 150 nm will be used. For example, a thickness of more than 200 nm will be used. For example, a thickness of more than 250 nm will be used. For example, a thickness of more than 300 nm will be used. For example, a thickness of more than 400 nm will be used. For example, a thickness of more than 500 nm will be used.

[0078] In a particular embodiment according to the present invention, the conductive layer located under the substrate is characterized by a thickness of conductive material less than 20 microns, for example less than 10 microns, or even less than 2 microns. For example, a thickness of less than 1.5 microns will be used. For example, a thickness of less than 1 micron will be used.

[0079] In a particular embodiment according to the present invention, the total of the layers (conductive pattern - dielectric - conductive layer) could for example have a thickness of 0.1 to 3 mm.

[0080] Although we speak of a label with or without a ground plane, in the art, the term "ground plane" is often associated with the metal layer (located under the substrate) whose surface preferably corresponds completely to that of the substrate.

[0081] In a particular embodiment according to the present invention, the material of the conductive 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 mixtures thereof, preferably copper and / or silver and / or aluminum. In a particular embodiment according to the present invention, the material of the conductive layer constituting the ground plane is different from or identical to that of the conductive pattern, preferably identical.

[0082] The second metal layer (the pattern(s)) will advantageously be shaped so as to have a particular geometric shape corresponding to the patterns of the label (like the patterns shown in the figures as well as those which are the subject of the present invention). A label with a ground plane is therefore a structure comprising two metal layers whereas its analogue without a ground plane will comprise a single layer, namely the one where the pattern of the label is produced. A label with a ground plane has the advantage, once positioned on the ground plane side on an object, of electromagnetically isolating the label from the object. In this case, the influence of the object on the label is less compared to a label without a ground plane.

[0083] It is also noted that a tag with a ground plane is a special case of a tag comprising two metallized layers where the substrate is sandwiched. Indeed, in this preferred configuration, one of the two layers is preferably entirely metallized. However, intermediate tag configurations are possible, for example, a tag with ground planes, where on the ground plane side, openings (removals of metal areas) are made to achieve a particular behavior. This can, for example, make it possible to create new resonances, or to modify those already present on the first conductive layer. They can also promote the isolation of the different resonators of the second metal layer, thus improving the decoupling of these resonances and therefore having an effect that can improve the reading performance of the tag.

[0084] The conductive material layer of the ground plane can be deposited, preferably directly on the dielectric substrate, by any suitable deposition method. The deposition methods mentioned above for the deposition of conductive patterns will already be repeated for illustrative purposes.

[0085] It is also noted that a chipless label comprising two conductive layers with the dielectric layer in the middle, for cost reasons, can also be produced by surrounding the substrate with the conductive layers, for example by folding. In this case, the conductive layer can have a surface area at least twice that of the substrate, typically a width at least twice as large with the same length. Once this surface comprising the conductive patterns and / or the ground plane is manufactured, it will advantageously be transferred in one go around the dielectric layer. This is possible by folding it all around. The only difference compared to the traditional approach (transferring one by one of the two metallized layers on each of the faces of the dielectric) is the presence of the metallized layer on one or more of the sides of the dielectric.If this part is not metallized, there is no significant difference compared to the more traditional approach. However, the possibility of metallizing this part (one or more sides of the dielectric) will allow the creation of more complex structures, which, like a resonant cavity with metal walls, will improve the quality factor. Thus, a person skilled in the art is able to take advantage of this structure, which is generally simpler to create because it requires fewer manufacturing steps. Indeed, this latter approach reduces the number of technological steps: printing a single conductive support, and bonding a single support as well.

[0086] In a particular embodiment according to the present invention, the dielectric substrate (with or without a ground plane) will be selected from commercial materials used in thermal insulation or acoustic insulation, the characteristics of which correspond to the characteristics of the present invention (and / or to those claimed in the present invention); and the desired conductive patterns will be directly affixed to these commercial materials.

[0087] Although the present invention applies to both ground plane and non-ground plane labels, a ground plane label configuration is preferred.

[0088] In a particular embodiment according to the present invention, the chipless RFID tag (and / or tag strip) has a ratio between the total upper surface of the dielectric substrate and the upper surface of the dielectric substrate covered with pattern(s) consisting of a layer of conductive material greater than 2.

[0089] In a particular embodiment according to the present invention, the chipless RFID tag (and / or tag strip) with ground plane has a ratio between the lower surface area of ​​the dielectric substrate covered with the layer of conductive material and the total lower surface area of ​​the dielectric substrate greater than 0.9.

[0090] Drive

[0091] By way of illustration, in the context of the present invention, the reader is an electromagnetic wave transmitter-receiver reader; the operating principle of said reader is based on the emission of an electromagnetic signal towards the identification tags which will return said signal according to their geometry (and for example their own resonance characteristics) and on the capture by the reader of said reflected signal - thus, the processing of the received signal (in particular through a decoding step) will make it possible to trace the information contained in the tag.

[0092] Thus, in general, the chipless radio frequency identification tags according to the present invention are part of an RFID system which also comprises one or more RFID readers which are themselves connected or not to supervisory computers or to an electronic card which carries out processing of the information received and which can for example make the link with existing databases. These readers therefore make it possible to identify objects thanks to the RFID tags which are affixed to them, said chipless RFID tags being comparable to a static radar target with a specific electromagnetic signature. Thus, in a particular embodiment of the present invention, the RFID readers are therefore comparable to a radar in terms of operation, for example an aerial radar detecting the signature of aircraft to a close scale and power ratio.By way of illustration, chipless RFID tags can be seen as radar targets having a particular time or frequency signature. Any type of radar suitable for receiving / identifying the signal retro-emitted by the RFID tag may advantageously be used within the scope of the invention; by way of illustration and not limitation, we will cite pulsed radar.

[0093] The coding capabilities obtained by means of the chipless radio frequency identification tags according to the present invention meet the standards in force because the tags obtained allow for at least 40 bits of information, which corresponds to EAN13 type bar codes. As an illustration, values ​​of more than 40 bits for a credit card format [i.e. 40 / (85.60 x 53.98 mm) = 40 / 46 bits / cm 2] have been obtained; thus, in a particular embodiment according to the present invention, the labels of the strip which is the subject of the present invention are characterized by a coding capacity value greater than 0.85 bits / cm 2 , for example greater than 1 bits / cm 2 , greater than 2 bits / cm 2 , or even higher than 5 bits / cm 2 .

[0094] This significant increase in coding capacity is achieved by combining two coding principles, each of which contributes to the total coding capacity. Indeed, this chipless tag geometry allows for frequency coding, traditionally used in chipless technology, which is recognized for being efficient in terms of coding capacity relative to the surface area of ​​the tag. This coding is based on the use of resonators of different lengths, which therefore also have different resonance frequencies. The reader used to read this tag must be able to retrieve information on the different resonance frequencies present on the tag positioned in its reading area. NbitF denotes the number of bits corresponding to the implementation of this frequency coding principle.To these NbitF will be added the bits related to the cumulative use of another type of coding (generally referred to as hybrid coding) which is independent of the one previously mentioned and which is based on the orientation of the resonators within the tag. We note NbitA the number of bits obtained by the implementation of this angular coding. As these two codings are independent of each other, the total coding capacity of the tag in bits corresponds to the sum: NbitF + NbitA. The angular coding is based on the fact that the resonators will be arranged with different orientations on the tag, and in an efficient manner by covering the entire plane, namely 360 degrees. The field backscattered by the tag, in addition to containing information on the frequencies of these resonators, contains information on their respective angular position.Also on the reader side, a specific algorithm allows to recover for each resonator its orientation in the plane of the tag, and this information contributes to the angular coding and therefore to NbitA. In order to make the angular decoding technique robust, it is preferable to use one resonator per tag as a reference resonator which will have the role of indicating the angular reference (the 0 angular degree). Thus the angles of the other resonators will have this angle as an angular reference. Obviously, reserving a resonator as an angular reference is a compromise between coding capacity and reading robustness. By using it as an angular reference resonator, it no longer contributes directly to the angular coding, however it makes it easier to fully decode the tag.

[0095] Regarding the total capacity of the tag, NbitF is mainly limited by the allocatable frequency band (typically between 3.1 and 10.6 GHz), the quality factor of the resonators and the number of resonators that can be put on a tag. Taking all the regulatory and technical constraints into account, it is difficult to encode more than 20 bits (NbitF=20) simply with the frequency approach. NbitA is directly linked to the number of permitted angular positions. The higher this number, the greater the coding capacity. However, the limitations come from both the possible angular resolution in relation to the reader and the surface of the tag where a limited number of resonators can be positioned.The geometries used in the present invention make it possible to optimize the distribution of the resonators on the label so as to have a large number of different angles for a given label surface. Taking into account the various limitations, a number of bits NbitA approximately equal to or greater than 20 is achievable in practice. It can thus be seen that the patterns used for the production of chipless labels make it possible to achieve a total of around 40 bits.

[0096] The present invention thus also relates to an assembly comprising one or more chipless radio frequency identification tags as described in the present invention as well as one or more electromagnetic wave transmitter-receiver readers which identify said tag(s), this identification being characterized by a combination of frequency coding and angular coding.

[0097] In an alternative embodiment of the present invention, the label which is the subject of the present invention may be affixed to any type of object and / or living being (for example an animal or a human). In an alternative embodiment of the present invention, the object on which the label will be affixed (preferably glued) may be selected from a large number of materials, of which we will cite as non-limiting examples metal, paper, fabric, plastic, for example a methacrylic copolymer resin, polyester, polycarbonate, polyethylene, polypropylene, and / or polyvinyl chloride, or even cellulosic-type materials such as, for example, wood, plywood or crystalline materials such as glass or ceramics, for example complex materials comprising one or more of these components such as, for example, milk cartons.

[0098] In an alternative embodiment of the present invention and provided that the dielectric substrate of the label which is the subject of the present invention meets the requirements of one or more of the aforementioned requirements, said dielectric substrate may be selected from a large number of materials, of which we will cite as non-limiting examples paper, fabric, plastic, for example a methacrylic copolymer resin, polyester, polycarbonate, polyethylene, polypropylene, and / or polyvinyl chloride, or even cellulosic-type materials such as, for example, wood, plywood or crystalline materials such as glass or ceramics, for example complex materials comprising one or more of these components such as, for example, milk cartons.

[0099] The morphological characteristics of our chipless radio frequency identification tag, with its dielectric substrate layer and the patterns made of a layer of conductive material representing the tag resonators are important in the context of our invention because they guarantee the proper functioning of said tags (with good recognition of the resonances induced by an emitted / reflected electromagnetic signal).

[0100] Dielectric substrate

[0101] In a preferred embodiment, the chipless radio frequency identification tags according to the present invention are therefore characterized in that they comprise a dielectric substrate layer.

[0102] Any dielectric substrate meeting the objectives of reading and resonance and discrimination performance according to the present invention may advantageously be used within the framework of the present invention.

[0103] This dielectric substrate will be advantageously selected from among the dielectric substrates meeting at least one, two or all three of the following properties: • an apparent density of less than 250 kg.irT 3 ; for example less than 100 kg.m“ 3 ; and / or

[0104] • a relative permittivity less than 3; preferably less than 2; preferably less than 1.25. For example, this relative permittivity will be less than 1.10.

[0105] In a particular embodiment according to the present invention, this relative permittivity will be close to 1. This relative permittivity will preferably be greater than 1.001. For example, this relative permittivity will be greater than 1.01; and / or

[0106] • a loss angle tangent value less than 10' 2 , preferably less than 10' 3 , for example less than 2.10" 4 .

[0107] As an illustration, a dielectric substrate with an apparent density of between 25 and 75 kg.m” will be cited. 3 ; a relative permittivity between 1.05 and 1.09; and a loss angle tangent value tan 5 between 10' 5 and 2.10 -4 at a frequency of 3.9 GHz.

[0108] This particular dielectric substrate will advantageously be selected from among the dielectric substrates made of solid foam, foam board, corrugated board, honeycomb board or fabric (for example made of a material made of interwoven threads or fibers made of cotton, hemp, linen or synthetic materials such as nylon, polyamide or viscose).

[0109] This dielectric substrate will advantageously be rigid or flexible; it will preferably be in the form of a film.

[0110] The thickness of the dielectric substrate will advantageously be greater than 0.1 mm. This thickness will preferably be greater than 0.5 mm. This thickness will, for example, be greater than 0.75 mm.

[0111] The thickness of the dielectric substrate will advantageously be less than 10 mm, for example equal to or less than 5 mm. This thickness will preferably be less than 3 mm. This thickness will for example be less than 1.5 mm.

[0112] Solid foam

[0113] Solid foam (e.g. polymer foam) is a solid foam used for illustrative purposes in many applications such as thermal insulation, acoustic insulation, packaging, automotive, etc. This foam can be thought of as a solid continuous network comprising trapped gas bubbles (usually air), which makes it possible to combine the properties of a foam (density, lightness) with those of a solid.

[0114] The solid foam used in the context of the present invention will preferably have an apparent density of less than 250 kg.m" 3 . For example, it will have an apparent density of less than 100 kg.m” 3 .

[0115] The solid foam used in the present invention will preferably have a bubble density of between 10 4 and 10 9 bubbles / cm 3 . For example, it will have a bubble density of 10 5 and 10 8 bubbles / cm 3 .

[0116] The solid foam used in the context of the present invention will preferably have a bubble size with an average diameter of between 5 microns and 1 millimeter. For example, it will have an average diameter of between 20 microns and 200 microns.

[0117] Any material having the foam characteristics defined within the scope of the present invention may advantageously be selected. We will cite by way of illustration foam board, polymers or biopolymers. By polymer we generally understand a set consisting of several macromolecules (molecule consisting of the repetition of numerous sub-units); in general, when the molar mass of the material is greater than 2,000 g / mole we speak of polymer.

[0118] Generally, and in a particular embodiment according to the present invention, the dielectric substrate (for example solid foam, foam board, corrugated board, honeycomb board and / or fabric, preferably solid foam) with its characteristics as described herein represents at least 95% by volume and / or 95% by thickness and / or 95% by weight of the entire dielectric substrate of the strip which is the subject of the present invention, preferably at least 99% by volume and / or 99% by thickness and / or 99% by weight of the entire dielectric substrate.The present invention therefore also relates to a chipless RFID tag strip comprising (see consisting of) a dielectric substrate which is itself made up of a dielectric substrate with its characteristics as described here above (and / or claimed) and one or more thin dielectric layers, for example a thin dielectric layer on which is (are) affixed the pattern(s) made up of a layer of conductive material; this (these) thin dielectric layer(s) (for example a film of paper or cardboard or plastic material (for example: a film of polyethylene (PE), polypropylene (PP) or preferably polyethylene terephthalate (PET)) therefore advantageously represents less than 5%, or even less than 1% of the thickness of the entire dielectric substrate.

[0119] Although a priori optional and not critical, the Applicant has found that this thin dielectric layer or dielectric film provides numerous additional advantages to the RFID label which is the subject of the present invention, subject to a few preferred requirements.

[0120] In a particular embodiment, the dielectric film is characterized by one, two or more of the following characteristics:

[0121] - a relative permittivity measured at any frequency between 3 and 10 GHz higher than that of the main dielectric substrate (solid foam, foam board, corrugated board, honeycomb board and / or fabric, preferably solid foam); preferably a relative permittivity greater than 1.25, for example greater than 2; preferably a relative permittivity less than 3.5; and / or

[0122] - a loss angle tangent value measured at any frequency between 3 and 10 GHz higher than that of the main dielectric substrate (solid foam, foam board, corrugated board, honeycomb board and / or fabric, preferably solid foam); preferably a loss angle tangent value less than 2.10' 2 ; and / or

[0123] - a thickness at least ten times less than that of the main dielectric substrate (solid foam, foam board, corrugated board, honeycomb board and / or fabric, preferably solid foam); preferably a thickness less than 100 microns, for example less than 50 microns; and / or

[0124] - made of plastic material, for example polyethylene, polypropylene or polyethylene terephthalate.

[0125] Cardboard

[0126] As indicated above, the dielectric substrate according to the present invention may, for example, be selected from corrugated cardboard or honeycomb cardboard. For example, the corrugated cardboard will be selected from B-flute cardboard (also called PC, generally with a thickness of between 2.5 and 3.5 mm), E-flute cardboard (also called micro-flute, generally with a thickness of between 2 and 1.5 mm); F-flute cardboard (also called Minimicro, generally with a thickness of approximately 1.2 mm), G or N-flute cardboard (called Nano-flute) with a thickness of approximately 0.8 mm, O-flute cardboard, with a thickness of approximately 0.5 mm, or a mixture of two or more of the aforementioned cardboards.

[0127] The cardboard used in the context of the present invention will preferably have an apparent density of less than 250 kg.m” 3 . For example, it will have an apparent density of less than 100 kg.m"” 3.

[0128] Conductive layer

[0129] The chipless radio frequency identification tags (chipless RFID tags) according to a preferred embodiment of the present invention are therefore characterized in that they comprise a dielectric substrate and patterns consisting of a layer of conductive material. In a particular case specific to the present invention, the tags also comprise under the dielectric substrate one or more layers of conductive material; preferably under the entire surface of the dielectric substrate. The configuration comprising two conductive layers, one under the dielectric substrate and that of the pattern(s) above the dielectric substrate, is a particularly interesting case for the invention (dielectric substrate sandwiched between the two conductive layers) as explained below in the description of the tags with ground plane.

[0130] In a particular embodiment according to the present invention, the material of the conductive 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 mixtures thereof, preferably copper and / or silver and / or aluminum.

[0131] In a particular embodiment according to the present invention, the conductive layer constituting the pattern is characterized by a thickness of conductive material greater than 100 nm. For example, a thickness of more than 150 nm will be used. For example, a thickness of more than 200 nm will be used. For example, a thickness of more than 250 nm will be used. For example, a thickness of more than 300 nm will be used. For example, a thickness of more than 400 nm will be used. For example, a thickness of more than 500 nm will be used.

[0132] In a particular embodiment according to the present invention, the conductive layer constituting the pattern is characterized by a thickness of conductive material less than 20 microns. The thickness of conductive material will preferably be less than 10 microns, or even less than 2 microns. For example, a thickness of less than 1.5 microns will be used. For example, a thickness of less than 1 micron will be used.

[0133] For illustration, the layer of conductive material may be deposited, preferably directly onto the dielectric substrate or onto the optional dielectric film, by any suitable deposition method.

[0134] Coil

[0135] The labels, the subject of the present invention, can, for example, be produced on a strip of labels, a strip which can advantageously be integrated into an industrial roll-to-roll process (also known as roll-to-roll processing) while providing numerous other advantages which will be described in the remainder of this description.

[0136] The present invention also relates to a coil of chipless radio frequency identification tag strip which is the subject of the present invention, said strip comprising a dielectric substrate layer and patterns made of a layer of conductive material representing the tag resonators, characterized in that the coil strip has dimensions of length L, width 1 and thickness Ep and in that it comprises grooves of depth Pr of the strip and oriented in the direction of the width of the strip.

[0137] Preparation of tapes and tape reels

[0138] The present invention also relates to a method for preparing the chipless RFID tag strip and its corresponding reel. Any prior art roll-to-roll (or reel-to-reel) method may advantageously be used within the scope of the present invention. The method for preparing the chipless radio frequency identification tag strip and / or its corresponding reel according to the present invention will advantageously use a roll-to-roll method which incorporates a cutting station for making the grooves.

[0139] The present application describes various technical features and advantages with reference to the Figures and / or various embodiments. Those skilled in the art will understand that the technical features of a given embodiment may in fact be combined with features of another embodiment unless the opposite is explicitly mentioned or it is obvious that these features are incompatible or that the combination does not provide a solution to at least one of the technical problems mentioned in the present application. In addition, the technical features described in a given embodiment may be isolated from the other features of this embodiment unless the opposite is explicitly mentioned.

[0140] It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered illustrative, but may be modified within the scope defined by the scope of the appended claims, and the invention should not be limited to the details given above.

Claims

Claims 1. A chipless radio frequency identification tag comprising a planar geometric pattern of n resonators made of conductive material, n being greater than or equal to 3, the resonators being V-shaped, the respective length of each diagonal of the V being pL and (1 -p)L with 0 < p < 1 per resonator and L being the cumulative length of the two diagonals of a resonator, with an angle a between the diagonals of the V of the resonators being substantially identical, a bisector of the resonators being substantially identical V-shaped, and characterized in that at least one value of p of a resonator is different from 0.

5.

2. Chipless radio frequency identification tag according to claim 1 characterized in that the majority of the V-shaped resonators have p values ​​different from 0.

5.

3. Chipless radio frequency identification tag according to claim 1 characterized in that the majority of the V-shaped resonators have different p values ​​from each other.

4. Chipless radio frequency identification tag according to claim 1 characterized in that the p values ​​of the V-shaped resonators are between 0.05 and 0.

95.

5. Chipless radio frequency identification tag according to claim 1 characterized in that the distance on the bisector between each intersection of the diagonals of two successive V-shaped resonators is less than 1 cm.

6. Chipless radio frequency identification tag according to claim 1 characterized in that at least two values ​​of L are different.

7. Chipless radio frequency identification tag according to claim 1 characterized in that the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the majority of the resonators are different.

8. A chipless radio frequency identification tag according to claim 1. characterized in that the angle a between the diagonals of the V of the resonators is different from 90°.

9. Chipless radio frequency identification tag according to claim 1 characterized in that the angle a between the diagonals of the V of the resonators is substantially equal to 120°.

10. A chipless radio frequency identification tag comprising a planar geometric pattern comprising at least two families of n resonators made of conductive material, n being greater than or equal to 3 in each family, the resonators being V-shaped whose respective length of each diagonal of the V is pL and (1 -p)L with 0 < p < 1 per resonator and L being the cumulative length of the two diagonals of a resonator in each family, with an angle a between the diagonals of the V of the resonators substantially identical in each family, with a bisector of the V-shaped resonators substantially identical in each family, and characterized in that at least one value of p of a resonator is different from 0.5 in each family.

11. A chipless radio frequency identification tag comprising a planar geometric pattern comprising three families of n resonators made of conductive material according to claim 10.

12. Chipless radio frequency identification tag comprising a planar geometric pattern comprising three families of n resonators made of conductive material according to claim 10 characterized in that the three bisectors of the three families intersect at the same point. 13 Chipless radio frequency identification tag according to any one of claims 10 to 12 having in each family one, two or more or all of the following characteristics: - the majority of V-shaped resonators have p values ​​different from 0.5; - the majority of V-shaped resonators have different p values ​​between them; - the p values ​​of V-shaped resonators are between 0.05 and 0.95; - the distance on the bisector between each intersection of the diagonals of two resonators successive V-shaped is less than 1cm; - at least two values ​​of L are different; - the angles formed in the plane between a horizontal of the plane and the virtual lines connecting the two isolated ends of the diagonals of the V of the majority of resonators are different; - the angle a between the diagonals of the V of the resonators is approximately equal to 120°.

14. A chipless radio frequency identification tag according to any one of claims 10 to 13 having in each family an angle a between the diagonals of the V of the resonators different from 90°.

15. A chipless radio frequency identification tag consisting of three families of resonators according to any one of claims 10 to 14, each family having an angle a between the diagonals of the V of the resonators substantially equal to 120° with the bisectors of the families intersecting at the same point.

16. An assembly comprising one or more chipless radio frequency identification tags according to any one of the preceding claims and one or more electromagnetic wave transmitter-receiver readers which identify said tag(s), this identification being characterized by a combination of frequency coding and angular coding.

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