EP2842081A1

EP2842081A1 - Radio-frequency identification device

Info

Publication number: EP2842081A1
Application number: EP13724855.5A
Authority: EP
Inventors: Christophe Loussert; Philippe Martin
Original assignee: Tagsys SAS
Current assignee: Tagsys SAS
Priority date: 2012-04-23
Filing date: 2013-04-23
Publication date: 2015-03-04
Also published as: US10192160B2; WO2013160611A1; US20150170018A1

Abstract

The invention relates to a radio-frequency identification device of the non-contact type, suitable for fixing to an object to be identified, said device comprising: a module (1) comprising at least one electronic chip and at least one electrical and/or magnetic so-called primary antenna used to supply signals to said at least one electronic chip, and an electrical and/or magnetic so-called secondary antenna (60). According to the invention, the secondary antenna is a conductive element (60) that forms part of said object or is produced by modifying a constituent of said object, said secondary antenna being coupled to said primary antenna without an electrical connection.

Description

RADIO IDENTIFICATION DEVICE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a radio identification device or RFID identification device (acronym for Radio Frequency Identification which means in French radio-identification) adapted to be attached to an object to be identified.

BACKGROUND OF THE INVENTION

In the field of RFID identification devices, labels

RFIDs are commonly used routinely for identifying, tracking, and managing objects. These tags generally include an RFID chip connected to an antenna formed by a magnetic loop. This is called magnetic RFID tags.

Devices using RFID technology thus enable more reliable and faster automated management of objects in many areas.

However, there are areas where the use of such RFID magnetic tags is limited. This limitation is often due to the nature of the objects to be identified or the environment in which these objects are located.

In the field of the management of objects such as shoes surgical instruments, trolleys or pairs of glasses, their use is limited because of the disturbances caused by the metals constituting these objects on the propagation of radio waves, difficulties encountered during the integration of these labels in these objects, for example because of the size of the label, and the nature of the label to integrate which can then have a reduced reading range due to structural constraints related to the object.

The label is then arranged at best on said object to overcome these disadvantages. The scope of these labels is however limited. For to increase it, it is known to add an antenna, called secondary antenna, on said object, this secondary antenna being coupled to the antenna of the tag.

However, metal parts of objects can still cause radio frequency disturbances. Moreover, the manufacture of the secondary antenna generates an additional cost of the device.

The present invention provides a solution to overcome all or part of the disadvantages of the state of the art. SUMMARY OF THE INVENTION

According to the invention, it is proposed to use the metal or conductive parts of the object as a secondary antenna to improve the range of the label.

The invention relates to a non-contact type radio-identification device capable of being fixed on an object to be identified, said device comprising

a module comprising at least one electronic chip and at least one electrical and / or magnetic antenna, called a primary antenna, intended to supply said at least one electronic chip with signals,

an electrical and / or magnetic antenna, called a secondary antenna, remarkable in that said secondary antenna is a conductive element constituting said object or is made by modifying a constituent element of said object, said secondary antenna being coupled, without electrical connection, to said primary antenna.

Thus, according to the invention, a conductive element of the object to be identified is used as a secondary antenna. The latter is electromagnetically coupled to the primary antenna. This conductive element may be a constituent element of the object, for example a metal arm of a pair of spectacles, or may be a modified component of said object, for example a slot in a metal plate of an object. A constituent element of the object to be identified is therefore an integral part of the radio-identification device.

Preferably, the module is positioned near the secondary antenna to allow the best possible electromagnetic coupling between said primary antenna and said secondary antenna.

Alternatively or in addition, the module is positioned relative to said secondary antenna to adapt the mechanical strength and / or chemical and / or thermal and / or radio device at the expense of electromagnetic coupling.

According to a particular embodiment of the invention, the device further comprises means for fixing said module to said object. The module is for example glued to said object.

According to a particular embodiment of the invention, the module is disposed in a stirrup for fixing said module to the object, said stirrup thus forming an intermediate antenna coupled on the one hand to the primary antenna of the module and to secondly to the secondary antenna of the object.

According to a particular embodiment of the invention, the dimensions of the module are much smaller than the dimensions of the conductive element, forming the secondary antenna, of the object so that the attachment of the module to the object does not change. the mechanical characteristics of the object. The module is for example rigid and the conductive element, forming the secondary antenna, is flexible. The small size of the module allows it, although rigid, not to significantly mitigate the flexible nature of the secondary antenna.

According to a particular embodiment of the invention, the secondary antenna is deformable and has electromagnetic characteristics which depend on the deformation applied to the secondary antenna.

Advantageously, the primary antenna of the module has an area of between 1 mm ² and 1000 cm ² , preferably between 4 mm ² and 400 mm ² , and a thickness of between 0.2 mm and 5 mm, preferably between 0, 2 mm and 2 mm. According to a particular embodiment of the invention, the electronic chip and the primary antenna coupled to the secondary antenna are able to receive and / or transmit signals in at least one of the following frequency bands:

a frequency band between 120 KHz and 135 KHz;

a frequency band between 6.765 MHz and 6.795 MHz; a frequency band between 13,553 MHz and 13,567 MHz; a frequency band between 26.957 MHz and 27.283 MHz; a frequency band between 40.660 MHz and 40.700 MHz; a frequency band between 433.050 MHz and 434.790 MHz; a frequency band between 865.6 MHz and 867.6 MHz;

a frequency band between 840.5 MHz and 844.5 MHz; a frequency band between 902 MHz and 928 MHz;

a frequency band between 952 MHz and 952.6 MHz;

a frequency band between 2.4 GHz and 2.5 GHz;

a frequency band between 5.725 GHz and 5.875 GHz; a frequency band between 24 GHz and 24.25 GHz;

a frequency band between 61 GHz and 61.5 GHz;

a frequency band between 122 GHz and 123 GHz; and a frequency band between 244 GHz and 246 GHz.

The radio-identification device of the invention can have various applications. The conducting element forming the secondary antenna is for example one of the following elements:

- a conductive part of a surgical instrument or a tool or an electronic device;

- a conductive branch of a pair of glasses;

a metal identification plate provided with a slot;

- a shank or metallic heel of a shoe;

- a conductive bra frame;

- a conductive part of a piece of luggage, - a metal protrusion or a slot in a tire rim;

- a metal part in the neck of a bottle;

- a wire in a drawstring of a luggage tag;

- a metal part of a gas cylinder;

- a metal part of a metal prosthesis;

- a metal part of a tire;

a metal part, already forming an antenna, of an electronic device.

The device of the invention can thus be used to perform the management of objects at the time of their production (production monitoring) or their marketing (inventory in warehouse or in store).

BRIEF DESCRIPTION OF THE FIGURES

Other advantages and characteristics of the invention will appear better on reading the description of a preferred embodiment which will follow, with reference to the accompanying drawings, carried out as indicative and non-limiting examples:

- Fig.1 shows a detailed schematic view of a first module used in the device according to the invention;

FIG. 2 represents a detailed schematic view of a second module that can be used in the device according to the invention;

3 represents an exploded view of a sole and a shank of a shoe, said shank being provided with the module of FIG. 2 so as to form a radio-identification device according to the invention;

- Fig.4 shows a schematic view of a pair of surgical scissors provided with the module of Fig.1;

- Fig.5 shows a schematic view of a pair of glasses provided with the module of Fig.1. - Figure 6 shows a schematic view of an identification plate provided with a slot and a module according to the module of Fig.1, the assembly forming a device according to the invention;

- Fig.7 shows a schematic view of a carriage with an identification plate according to Fig.6;

- Fig.8 shows a perspective view illustrating the introduction of the module of Fig.1 in a stirrup; and

- Fig.9 shows the module in the stirrup. DETAILED DESCRIPTION OF THE INVENTION

According to the invention, it is proposed to use a conductive element of the object to be identified to form the secondary antenna which is coupled to the antenna of the RFID module.

FIG. 1 represents a schematic view of a rigid RFID module 1 comprising an electronic chip 2 connected to an antenna, called a primary antenna 3, of magnetic type. The antenna 3 comprises a metal loop made on a support or rigid substrate 4. The antenna 3 is connected to two terminals of the chip 2, which is fixed to the substrate 4 by bonding, soldering or other equivalent means. The assembly is arranged in a housing not shown in the figure.

Fig.2 shows a schematic view of another flexible RFID module 10 comprising a small rigid (less than 1 cm ² ) rigid electronic chip 20 connected to a magnetic type primary antenna 30 having a single metal loop. This loop is performed on a flexible support 40, the electronic chip 20 being connected by two terminals to the metal loop. The chip 20 is connected to the support 40 by appropriate means, for example by welding to the magnetic loop. This support can be adhesive on one of its faces to fix the module on an object. To improve the range of these RFID modules and reduce the cost of the device, it is proposed according to the invention to couple the primary antenna module to a conductive element of the object on the module must be placed, said conductive element then forming a antenna, called secondary antenna, coupled to the primary antenna of the module. This invention is described in the following description through multiple application examples.

With reference to FIG. 3, the module 10 is disposed on the metal shank 50 of a boot. This metal piece, which is present in the sole thickness of the shoe, generally has the function of supporting the arch and maintain the arch of the shoe. According to the invention, it is used as a secondary antenna for the module 10. The shank is indeed an electric dipole able to form an electrical antenna for the module.

But, to be used as a secondary antenna at radio-identification frequencies, the conductive element must of course have minimum characteristics. It must be electrically conductive. It can therefore be made of an electrically conductive material, for example metal or carbon. In the example of Fig.3, the shank is metallic.

This conductive element must also be capable of receiving the radio-identification signals. In the case of the shank, the conductive element is an electric dipole. This electric dipole is an open circuit that picks up the electric field, in opposition to a magnetic loop which is a closed circuit. Its length is advantageously of the order of half a wavelength of the radio-identification signals (approximately 15 cm at 900 MHz), which is the case of the shank. Its thickness is advantageously greater than or equal to the skin thickness at the frequency considered (2μηη at 900MHz +/- 60MHz UHF ISM band). Moreover, the module is preferably placed in the middle of this electric dipole, at the point where the current is maximum, as shown in FIG. Note that the electric dipole is not necessarily straight but may have zigzags or meanders. It has the advantage of being more compact.

Fig.4 illustrates another example of application where the secondary antenna conductor element is an electric dipole. In this example, the RFID module 1 is attached to one of the scissors of a pair of surgical scissors 60. It is fixed to the chisel by means of a slide fastener which may be metallic. This chisel then serves as a secondary antenna to the RFID module.

Fig.5 illustrates another application where the conductive element forming a secondary antenna is also an electric dipole. In this example, the RFID module with primary antenna is disposed on a metal arm 71 of a pair of spectacles 70.

The conductive element forming the secondary antenna is not necessarily a wire element as in the examples of FIGS. 3 to 5. The conductive element may for example be a slot antenna. The conductive element can then be in the form of a metal plate having a slot, this slot being initially present in the plate or being made later to form the secondary antenna.

This case is illustrated by FIGS. 6 and 7. In these figures, the RFID module is disposed on a metal identification plate 81 of an object. This object is for example a carriage 80 as illustrated in FIG. The identification plate 81 is an integral part of said object 80. It comprises, for example, an identification number 82 engraved for a visual identification. According to the invention, a constituent element of the object, namely the identification plate, is modified to transform it into a secondary antenna. In this case, a slot 83 is made in the plate so as to create a slot antenna which will serve as a secondary antenna for the RFID module placed at one of the ends of the slot. The length of the slot is advantageously of the order of a quarter of a wavelength of the radio-identification signals (7.5 cm for a signal at 900 MHz) and the RFID module is placed at one of its ends, point where the current is maximum and where the electromagnetic coupling between the primary antenna and the secondary antenna is the strongest.

In these examples (Figs.3 to 7), the primary antenna is a magnetic antenna (magnetic loop of the module) and the secondary antenna is electric (electric dipole). But, more generally, the primary antenna can be electric or magnetic as well as the secondary antenna.

Similarly, in these examples, the module 1 or 10 is positioned relative to the antenna to allow optimum electromagnetic coupling between the primary antenna of the module and the secondary antenna (module placed in the middle of a dielectric dipole having a length of λ / 2 or module placed at the end of a slot antenna of length λ / 4). It should also be noted that in order to obtain this electromagnetic coupling, there is no need for an electrical connection between the primary antenna and the secondary antenna.

In other applications, it may be more important to guarantee the resistance or mechanical strength of the assembly formed by the module and the secondary antenna or its chemical or thermal resistance. The module is then positioned on said object at a location where the electromagnetic coupling between the primary antenna and the secondary antenna is not maximum. In the case of an object comprising an electric dipole forming a secondary antenna and having a length close to λ / 2, the module can be fixed at a point remote from the middle of the electric dipole to improve the mechanical strength of the device because the midpoint of the electric dipole can in some cases constitute a vulnerable point of the object. The coupling between the two antennas being reduced, the reading range of the RFID device will be reduced. For example, in the case of surgical scissors, the module may be shifted relative to the center of the chisel, at a point where the attachment of the module on the chisel will be more resistant. It is possible to adjust the reading range by varying the position of the module with respect to the point maximum current (midpoint in the case of a dipole length λ / 2 and end point in the case of a slot length λ / 4).

If the positioning of the RFID module near the conductive element of the object proves difficult because, for example, the conductive element is covered with plastic, it is also possible to add intermediate resonant structures. These structures will allow, despite the distance between the RFID module and the conductive element, to couple them.

The addition of resonant structures makes it possible to couple the RFID module containing or not an RFID integrated circuit to the radiating conductive element of the object. SCMR (for Strongly Coupled Magnetic Resonator) or resonant magnetic circuits strongly coupled in French allow to couple two circuits at frequencies LF, HF and VHF with a 90% efficiency at 85MHz. This type of circuit is described in the document entitled "Wireless Powering Based on Strongly Coupled Magnetic Resonance with SRR Elements" IEEE Hao Hu, Stavros V. Georgakopoulos, Department of Electrical and Computer Engineering, Florida International University. At these frequencies, they are formed of discrete distributed elements L- C. These intermediate resonant circuits thus make it possible to couple the rigid or flexible RFID module to the conductive element of the object even if the latter had to be separated for practical and unavoidable reasons due to the application.

It is also possible to use SRR (Split Ring Resonator) circuits to enable this coupling. SRRs are metamaterial patterns with dimensions of a few centimeters on the side for UHF frequencies. The perimeter of the pattern is rectangular or circular and of length close to λ / 2. These circuits make it possible to focus the electromagnetic field strongly and locally and thus improve the coupling between the conductive element of the object and the RFID module if these two elements were to be too distant from each other to function effectively.

As indicated above, the RFID module can be attached to the object. The fixing means used may be various: fixing by gluing, nailing, sewing, encapsulation in the object, screwing, clipping by stirrup or slide.

In the example of the shank, the module is for example glued into a machined cavity in the sole of the shoe so as to be arranged tangentially relative to the shank of the shoe. In the example of the glasses, the module is also glued on the glasses branch. Similarly, in the example of the identification plate, the RFID module is glued to one end of the slot 83.

According to a particular embodiment of the invention illustrated in FIGS. 7 and 8, this fixing means may be a stirrup 90 in which the module 1 is inserted. The stirrup then forms an intermediate antenna coupled on the one hand to the primary antenna of the module and on the other hand to the secondary antenna of the object. The stirrup is fixed by any means to the object, by gluing, by welding, etc. It is also possible to use tabs 91 present on the stirrup. It is possible to multiply the intermediate antennas to couple the primary antenna to the secondary antenna. In some applications, the dimensions of the module are much smaller than the dimensions of the conductive element, forming a secondary antenna, of the object so that the attachment of the module to the object does not alter the mechanical characteristics of the object. In the UHF band, the module 1 or 10 is for example in the form of a hexahedron of length 7 mm, width 7 mm and thickness 1.5 mm. If the conductive element, forming the secondary antenna, of the object has a much greater length, for example 10 cm, the module 1 or 10 can be rigid and fixed to a flexible secondary antenna without affecting the flexible nature of the the secondary antenna. For example, to identify flexible metal pipes, we can fix a module 1 or 10 of small size on the metal channel, the latter then serving as secondary antenna. The small dimensions of the module allow the pipe to maintain its flexibility.

According to a particular embodiment of the invention, the secondary antenna forming element is deformable and has electromagnetic characteristics which depend on the deformation applied to said secondary antenna. For example, in the case of a folding chair having a metal support structure, the latter can serve as a secondary antenna for an RFID module that would be stuck on it. The electrical characteristics of this secondary antenna change when folding or unfolding the chair. It could thus be arranged that the secondary antenna has appropriate electrical characteristics to operate with the RFID module only in one of the two states (folded or unfolded) of the chair.

The radio-identification device of the invention may be adapted to transmit and / or receive signals in one or more frequency bands from among the following frequency bands:

• [120 KHz, 135 KHz]

• [6.765 MHz, 6.795 MHz]

[13,553 MHz, 13,567 MHz]

[26.957 MHz, 27.283 MHz]

[40.660 MHz, 40.700 MHz]

[433.050 MHz, 434.790 MHz]

[840.5 MHz, 844.5 MHz]

[865.6 MHz, 867.6 MHz]

[902 MHz, 928 MHz]

[952 MHz, 952.6 MHz]

[2.4 GHz, 2.5 GHz]

[5.725 GHz, 5.875 GHz]

[24 GHz, 24.25 GHz] • [61 GHz, 61, 5 GHz]

• [122 GHz, 123 GHz]

• [244 GHz, 246 GHz]

As shown above, the device of the invention can be used for the radio-identification of a shoe, a surgical instrument, a container or a carriage, a pair of glasses. Of course, it can be implemented for the identification of other objects comprising a conductive element, for example a brassiere, the metal armature of the bra then serving as a secondary antenna, or a baggage comprising a part metallic, a bottle having a metal neck, a luggage tag comprising a cord with a wire, a metal gas bottle, a metal prosthesis, a tire comprising a metal frame.

According to a particular embodiment, it is possible to use, for an electronic device, a conductive element already serving as an antenna as a secondary antenna. For example, if the object is a telephone, the antenna of the phone can serve as a secondary antenna to an RFID module attached to or in the phone.

All of the embodiments described above use an RFID module comprising an electronic chip. Here is meant by electronic chip a semiconductor circuit comprising memories. It could be envisaged to use, instead of this module with an electronic chip, a so-called passive module without an electronic chip.This module is described in the patent application FR 2 956 232. This is known as a "chipless" technique. The chip is replaced by disjoint conductive strips formed on a dielectric support The geometry and dimensions of these bands are determined to, when receiving a given RF signal, reflect this signal with a specific spectral signature.

Claims

claims

1. Non-contact type radio-identification device adapted to be fixed on an object to be identified, said device comprising

a module (1; 10) comprising at least one electronic chip (2; 20) and at least one electrical and / or magnetic antenna, called a primary antenna (3; 30), for supplying said at least one electronic chip with signals ,

an electrical and / or magnetic antenna, referred to as a secondary antenna (50, 60, 71, 81),

characterized in that said secondary antenna is a conductive element (50,60,71, 81) constituting said object or is made by modifying a constituent element of said object, said secondary antenna being coupled, without electrical connection, to said primary antenna.

2. Device according to claim 1, characterized in that said module (1; 10) is positioned close to said secondary antenna (50,60,71, 81) to allow electromagnetic coupling between said primary antenna (2; 20) and said secondary antenna.

3. Device according to any one of the preceding claims, characterized in that said module (1; 10) is positioned relative to said secondary antenna (50,60,71, 81) to adapt the mechanical and / or chemical resistance and and / or thermal and / or radioelectric of said device.

4. Device according to any one of the preceding claims, characterized in that it further comprises means for fixing said module to said object.

5. Device according to claim 4, characterized in that said module is disposed in a bracket for fixing said module to said object, said stirrup forming an intermediate antenna coupled on the one hand to the primary antenna of the module and on the other hand to the secondary antenna of the object.

6. Device according to claim 4, characterized in that the dimensions of said module are smaller than the dimensions of said conductive element forming a secondary antenna, said object so that the attachment of said module to said object does not modify the mechanical characteristics of said object.

7. Device according to claim 6, characterized in that said module is rigid and the conductive element forming a secondary antenna, said object is flexible.

8. Device according to any one of the preceding claims, characterized in that said secondary antenna (50,60,71, 81) is deformable and has electromagnetic characteristics which depend on the deformation applied to said secondary antenna.

9. Device according to any one of the preceding claims, characterized in that said primary antenna has an area of between 1 mm ² and 1000 cm ² , preferably between 4 mm ² and 400 mm ² , and a thickness between 0, 2 mm and 5 mm, preferably between 0.2 mm and 2 mm.

10. Device according to any one of the preceding claims, characterized in that said electronic chip (1; 10) and said primary antenna (2; 20) coupled to said secondary antenna (50,60,71,81) are suitable receiving and / or transmitting signals in at least one of the following frequency bands:

- the frequency band between 120 KHz and 135 KHz;

- the frequency band between 6.765 MHz and 6.795 MHz; - the frequency band between 13,553 MHz and 13,567 MHz;

- the frequency band between 26.957 MHz and 27.283 MHz;

- the frequency band between 40.660 MHz and 40.700 MHz;

- the frequency band between 433.050 MHz and 434.790 MHz;

- the frequency band between 865.6 MHz and 867.6 MHz; - the frequency band between 840.5 MHz and 844.5 MHz;

- the frequency band between 902 MHz and 928 MHz;

- the frequency band between 952 MHz and 952.6 MHz;

- the frequency band between 2.4 GHz and 2.5 GHz;

- the frequency band between 5.725 GHz and 5.875 GHz;

- the frequency band between 24 GHz and 24.25 GHz;

- the frequency band between 61 GHz and 61.5 GHz;

- the frequency band between 122 GHz and 123 GHz; and

- the frequency band between 244 GHz and 246 GHz.

1 1. Device according to any one of the preceding claims, characterized in that the conductive element (50,60,71, 81) is one of the following elements:

a conductive part of a surgical instrument, a tool or an electronic device;