FR3076087A1 - CONTACTLESS COMMUNICATION DEVICE WITH MULTIPLE ANTENNA WINDINGS - Google Patents

Abstract

The invention proposes a contactless communication device (2) comprising a near-field communication antenna (AT1), said antenna comprising: a first winding (W1) and a second winding (W2) connected together in series, each winding comprising at least one conductive turn (L1, L2) formed in a winding plane (P1, P2), these winding planes being parallel to one another; the winding being arranged so that when an induced current travels the antenna from one end to the other through the windings, the current flows in a first direction of rotation (S1) in each turn of the first winding and circulates according to a second direction of rotation (S2), opposite the first direction of rotation, in each turn of the second winding.

Description

Background of the invention The invention relates to the field of contactless communication devices and relates more particularly to a particular antenna arrangement allowing secure communication in the near field,

Near field communication, sometimes referred to by the acronym MFC for "Near Field Communication", is a well-known short-range contactless communication technique, typically a few centimeters. This technique uses high frequency radio waves to exchange information between terminals, peripherals etc. provided for this purpose. The MFC technology is an extension of the ISO / CEI14443 standard relating to radio-identification cards, called RFID.

NFC technology is experiencing a growing development due to its many possible applications, in smartphones, tablets or connected objects for example, to allow their users to perform contactless communications in a wide variety of situations. In everyday life, for example, NFC technology is commonly used for access control (in transport in particular) or in payment applications. RFID devices, for example, can be configured to perform near-field communications.

Unlike other contactless communication techniques whose range is greater, the NFC technique can only be used over very short distances, generally a few centimeters, although longer distances are achievable in theory. This technique therefore presupposes a voluntary reuse process and thus limits the risks of information gathering without the knowledge; of the user. The increasing use of near-field communication devices, however, presents a major security risk insofar as sensitive or confidential information is: frequently exchanged: during contactless exchanges. Frauds include: maliciously collecting information exchanged during a near field communication, The phishing technique is for example used by some fraudsters to obtain personal information during such communications contactless, in particular to perpetrate identity theft. The invention aims to mulch the problems and drawbacks set out above and aims in particular to secure the exchange of data during contactless communication in the near field.

OBJECT AND SUMMARY OF THE INVENTION For this purpose, the present invention relates to a contactless communication device comprising a near-field communication antenna, said antenna comprising: a first winding and a second winding connected together in series, each winding comprising at at least one conductive turn formed in a winding plane, said winding planes of the first and second windings being parallel to one another; said windings being arranged so that when an induced current flows through the antenna from one end to the other through said windings, the current circulated in a first direction of rotation in each turn of said first winding and flows in a second direction of rotation, opposite to the first direction of rotation, in each turn of said second winding.

According to a particular embodiment, the first direction of rotation is clockwise and the second direction of rotation is counterclockwise.

According to a particular embodiment, the respective winding planes of said first winding and said second winding each have an upper face and a lower face, said first and second windings being arranged in opposite winding directions so that, when a magnetic field is incident on the upper faces of the winding planes of said first winding and said second winding or incident on the lower faces of the winding planes of said first winding and said second winding, the current induced in said first winding and the current induced in said second winding cancel each other out.

According to a particular embodiment, the pfemièr and second windings are configured so that the total of the surfaces defined by each turn of the first winding is equal, to within plus or minus 20%, to the total of the surfaces defined by each turn of the second winding .

According to a particular embodiment, the antenna comprises a continuous electrically conductive track forming, in series with one another, said first winding and said second winding.

According to a particular embodiment, the conductive track is a conductive wire or a conductive material deposited on a substrate.

According to a particular embodiment, the winding plane of the first winding and the winding plane of the second winding are merged with each other.

According to a particular embodiment, the communication device is a smart card in which said antenna is integrated.

According to a particular embodiment, the communication device further comprises a processing module connected at both ends: of the antenna, the processing module being configured to detect, from a current induced in the antenna by a magnetic field, at least one signal received by the antenna according to near field communication.

According to a particular embodiment, the processing module is configured to detect said induced current from a first magnetic field incident on a first winding face of said first winding and from a second magnetic field incident on the second winding face of said second winding, said first face being opposite to said second; face. The invention also relates to a method of manufacturing a contactless communication device as defined above. More particularly, the invention relates to a method of manufacturing a contactless communication device, comprising the following steps: - providing a substrate; and - formation, on or in the substrate, of a near-field communication antenna, the antenna comprising a first winding and a second winding connected together in series, each winding comprising at least one conductive turn formed in a plane of winding, said winding planes of the first and second windings being parallel to one another; the said windings being formed so that when an induced current flows through the antenna from one end to the other through the said windings, the current flows in a first direction of rotation in each turn of said first winding and flows in a second direction of rotation, opposite; in the first direction of rotation, in each turn of said second winding.

It will be noted that the various embodiments mentioned above in relation to the contactless communication device of the invention as well as the associated advantages apply analogously to the manufacturing process of the invention.

According to a particular embodiment, the method further comprises a step of positioning an electronic component on or in the substrate, the antenna being electrically connected to the electronic component.

According to a particular embodiment, the respective winding planes of said first winding and said second winding each have an upper face and a lower face, and in which, during the forming step, said first and second windings are formed according to opposite winding directions so that when a magnetic field is incident on the upper faces of the winding planes of said first winding and said second winding or incident on the lower faces of the winding planes of said first winding and said second winding, the current induced in said first winding and the current induced in said second winding cancel each other out.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate examples of embodiment which are devoid of any limiting character. In the figures: - Figure 1 is a schematic view of a contactless communication device according to a particular embodiment of the invention; - Figure 2 schematically shows a communication system comprising a contactless communication device and a corresponding reading terminal, according to a particular embodiment of the invention; - Figure 3 schematically shows the field lines of a magnetic field emitted by a reading terminal, according to a particular embodiment; - Figures 4A and 4B schematically represent the interaction of a contactless communication device and a reading terminal in a particular embodiment of the invention; - Figures 5A and 5B schematically represent the interaction of a contactless communication device and a reading terminal in a particular embodiment of the invention; - Figures 6 and 7 schematically represent the interaction of a contactless communication device and a reading terminal, in a particular example; - Figures 8A is a view illustrating the embodiment shown in Figures 5A and 5B;

- Figures SB is a view illustrating the embodiment shown in Figures 4A and 4B - Figure 9 schematically shows an arrangement: particular of an antenna, according to a particular embodiment of the invention; - Figure 10 shows, in the form of a diagram, the steps of a manufacturing process, according to a particular embodiment of the invention; and - Figure 11 schematically shows an antenna arrangement according to a particular embodiment.

Detailed description of several embodiments

As indicated above, the invention relates to contactless communication devices and relates more particularly to a particular antenna arrangement allowing secure communication in the near field.

In this document is meant by a near field communication device or a near field communication antenna, means configured to perform contactless near field communications, for example according to an HF (high frequency) frequency band of the RFID applications (for "radio frequeney identification"), in accordance with at least one of the following standards: 1SO / IËC 14443A, ISO / IEC 14443B, ISO / IEC 15693, FELICA (JIS X 6319-4), ISO / IEC 18000-3. The frequency used is for example equal, or substantially equal, at 13.56 MHz. The invention proposes, according to a particular embodiment, to implement a particular antenna arrangement in order to secure contactless communications carried out in the near field (NFC). To do this, the invention provides for the implementation of a near-field communication antenna having particular windings comprising a first winding of turns wound in a first winding direction (clockwise for example) and a second winding of turns wound in a second winding direction (counterclockwise for example), opposite to the first direction of rotation. The direction of winding designates in this document the direction, clockwise or counterclockwise, that the antenna follows from a starting point (point of origin) of the winding located at the heart of the winding (closest to i ' winding axis) up to an end point (opposite to the starting point) of the winding located on the outer periphery of the winding. It follows that a current capable of being induced in an antenna within the meaning of the invention passes through the antenna from one end to the other so that it necessarily follows a first direction of rotation in the first winding and necessarily follows a second direction of rotation, opposite to the first, in the second winding. This circulation in opposite directions of rotation in the two parts of the antenna has the effect that normal operation of the antenna is only possible if it is in a particular position vis-à-vis the terminal of reading with which it interacts. As explained below, the antenna can exchange information during a near field communication only if it is in a particular region of the magnetic field generated by the reading terminal. Outside this particular region, no near field communication is possible, which limits the risk of fraud, such as "phishing" for example.

As indicated below, the principle of the invention can be applied to two or more windings, so that there are at least two windings in opposite directions, that is to say at least one winding in the first direction of rotation and at least one winding in the second direction of rotation, opposite to the first direction of rotation, as described in this document. Other aspects and advantages of the present invention will emerge from the exemplary embodiments described below with reference to the drawings mentioned above,

In this document, examples of implementation of the invention are described in the context of a contactless card configured to communicate in the near field with a corresponding reading terminal. It will be understood, however, that the invention does not apply exclusively to contactless cards but can be implemented more generally in any contactless communication device.

Unless otherwise indicated, the elements common or analogous to several figures share the same reference signs and have identical or analogous characteristics, so that these common elements are generally not described again for the sake of simplicity.

FIG. I schematically represents the structure of a near field communication device 2 in accordance with a particular embodiment of the invention. This device 2 is in this example in the form of a card, although variants are possible.

More specifically, the contactless communication device 2 comprises a communication antenna (or radio frequency antenna), denoted ATI, configured to carry out near field communications, called NFC communications. This ATI antenna comprises a first winding W1 of a plurality of electrically conductive turns L1 and a second winding W2 of a plurality of electrically conductive turns L2. In general, it is understood that each of the windings W1 and W2 can comprise at least one conductive turn Li and L2. These antenna windings are intended to collect, in the form of a current, electromagnetic energy supplied by a magnetic field to which the antenna is exposed.

In a particular example, the device 2 is an RFID device configured to communicate in the near field with the outside according to RFID technology.

The first and second windings W1, W2 of the device 2 are electrically connected together in series. Each of the windings Wl and W2 thus form a portion (or part) of rantennê ÂTi through which a current can flow

These antenna windings W1 and W2 are arranged respectively in winding planes PI and P2 which are parallel with respect to each other. In this particular case, the planes PI and P2 specific to the windings W1 and W2 are combined, although variants are possible as described later with reference to FIG. 9

As shown in Figure 1, the ATI antenna is formed by an electrically conductive and continuous track 4. This conductive track thus forms, in series with respect to each other, the first winding W1 and the second winding W2. The characteristics of this conductive track can be adapted by those skilled in the art according to each case. In this example, track 4 is formed from a conductive wire, in copper or aluminum for example (wired manufacturing technique) possibly coated with a sheath of insulating material (in plastic for example). As a variant, the track 4 can consist of a conductive material deposited on a substrate denoted 8 as indicated below. The shape and dimensions of the track section, the length of the track, the type of conductive material used, etc. may in particular be chosen appropriately by a person skilled in the art according to the case in hand.

In this example, the ATI antenna is arranged on a substrate 8 so that its two ends 4a and 4b are electrically connected to the terminals of any electronic component 6, Able to use the ATI antenna to communicate in the near field with an external entity, such as the reading terminal T shown in FIG. 2.

According to the invention, the antenna windings W1 and W2 are wound in opposite winding directions with respect to each other. As already indicated, the direction of winding here designates the direction of rotation that the antenna follows from a first end of the winding located at the heart (at the point of origin) of the winding to a second end ( opposite the first end) of the antenna located at the outer periphery of the winding, In the example shown in FIG. 1, the first winding W1 is wound in a clockwise winding direction while the second winding W2 is wound according to a counterclockwise winding direction. In other words, the windings W1 and W2 are arranged so that when an induced current flows through the antenna ΔTÏ from one end to the other (from 4a to 4b, or vice versa) through said windings, the current flows according to a first direction of rotation SI in each turn L1 of the first winding W1 and flows in a second direction of rotation $ 2, opposite to the first direction of rotation SI, in each turn L2 of the second winding W2. Such a current can be generated by magnetic induction under the action of a magnetic field to which the antenna windings W1 and / or W2 are exposed. As indicated below, the direction of rotation Si or S2 which the current induced in the windings W1 and W2 then follows is a function of the magnetic field to which the windings are: exposed, and depends in particular on the winding face by which the magnetic field reaches the windings Wl, W2, In the example shown in FIG. 1, the direction of rotation SI of the current in the first winding Wl is counterclockwise and the direction of rotation S2 of the current in the second winding is clockwise , although the reverse configuration is possible.

As explained below, this arrangement in opposite winding directions of the windings W1 and W2 of the ATI antenna makes it possible to prevent any near-field communication with the outside in certain particular cases. Near Field communication is possible or blocked depending on the position of the device 2 relative to the reading terminal with which it interacts and, more precisely, depending on the position of the windings Wl and W2 relative to the magnetic field emitted by the reading terminal,

FIG. 2 represents the contactless communication device 2 of FIG. 1, this device 2 being configured to communicate in the near field with a reading terminal T provided for this purpose. The device 2 and the reading terminal T together form a communication system SY.

More particularly, the terminal T is configured to generate a magnetic field F to which the device 2 can be exposed. This magnetic field F is here generated by induction from a current flowing in a circuit of the terminal T comprising conductive turns. By way of example, the device 2 can be a contactless card (of the RFID type for example) that its user presents near a reader to allow: access, for identification, to carry out a payment transaction.

In the example considered here, the electronic component 6 of the device 2 comprises a processing module 10 connected to the ends 4a, 4b of the antenna ATI. The electronic component 6 is for example a processor. Furthermore, the processing module 10 is here configured to use the ATI antenna in order to communicate in the near field with the reading terminal T.

More particularly, the magnetic field F emitted by the terminal T makes it possible: to carry out a short distance transfer of electromagnetic energy to the component 2 through its antenna: AT1. The incident magnetic flux excites: the ATI antenna so as to cause a displacement of electric charges which can give rise to an electric current.

The processing module 10 is configured to detect, from a current induced in the antenna ATI by the magnetic field F, at least one signal SG received by the antenna according to a communication in the near field. A current induced by the magnetic field F can thus flow from one end to the other of the ATI antenna so as to transmit one or more pieces of information that can be used by the processing module 10. The general principle of near-field communication being known to those skilled in the art, the way in which information is exchanged and processed between the device 2 and the terminal T will not be described in more detail in this document.

It will be noted that the specifics of the magnetic field F liable to be emitted by the terminal T may vary depending on the case. By way of example, FIG. 3 represents, in the form of a set of field lines 20, a magnetic field (or magnetic flux) generated by the terminal T. As shown in this figure, the magnetic field circulates according to a particular direction along the field lines 20, this direction being a function of the polarity of the source of the magnetic field. These field lines 20 in particular in this example have the shape of lateral lobes in the vicinity of two opposite edges of the terminal T. Note that certain elements generally present in an N FC reading terminal or in an NFC communication device have been deliberately omitted because they are not necessary for the understanding of the present invention.

It should be recalled that the device 2 shown in Figures 1 and 2 is only a non-limiting embodiment, other implementations being possible in the context of the invention.

The operation of the device 2 in cooperation with the reading terminal T is now described according to particular embodiments, with reference to FIGS. 4A-4B, SÀ-5B> and 6-9.

More specifically, the figures 4A and 4B are two different views (perspective view and top view) schematically representing a first case where the device 2 shown in figures i-2 interacts with the reading terminal T. In this first case, we assumes that a user positions the device 2 in the close vicinity of the terminal T so that the antenna ATI is within detection range of the magnetic field F emitted by the terminal T, The device 2 is here approximately positioned with regard to a region central Ta of an active face of terminal T.

In this first case illustrated in FIGS. 4A and 4B, a first part F1 and a second part F2 of the magnetic field F respectively reach the antenna windings Wi and W2 via the upper face 2a of the device 2. In other words, the magnetic field F1 (and vice versa F2) excites the antenna winding W1 (and vice versa W2) by crossing the respective winding plane PI (and vice versa P2) from its upper face Pla (and vice versa P2a) towards its lower face Pib (and vice versa P2b), In this particular case, the incident magnetic fields F1 and F2 then both tend to induce a current flowing in the same direction of rotation 52 in the parts W1 and W2 of the antenna, namely: clockwise in this example. Since the bearings Wl and W2 have opposite winding directions, the displacements of electric charges induced in these two windings are mutually opposed, thus canceling (partially or totally) the current resulting from the excitation of the magnetic field F. In other words, the arrangement according to ibvërses winding directions of the antenna parts W1 and W2 has the consequence that no current is globally induced in the antenna ATI when the magnetic field is incident on the same face (superior in this case) of the windings Wl and W2. In some cases, the cancellation of the displacement of charges is not total. March leads to the induction of a negligible current, that is to say less than a predetermined threshold value which is necessary, for example, to be exploitable by component 6.

In the same way, if the device 2 is placed at a position relatively distant from the terminal T, it is then immersed in a distant magnetic field F which is incident on the same face of the windings Wl and W2 which prevents the induction of a current in the ATI antenna as already described with reference to FIGS. 4A and 4B, As described below, the arrangement in opposite winding directions of the antenna parts W1 and W2 thus makes it possible to prevent fraudulent collection of information contained in the device 2 by a “phishing” technique. The phishing technique can indeed occur when the device 2 is located at a distance from the magnetic source so that it is exposed to a far-reaching magnetic field: F which is incident on the same winding face of the windings W1 and W2.

Furthermore, FIGS. 5A and SB are two different views (perspective view and top view) schematically showing a second case where the device 2 shown in figures; 1-2 interacts with the reading terminal T. This second case differs from the first case illustrated in FIGS. 4A-4B in the position of the device 2 with respect to the terminal T, and more particularly with respect to the magnetic field F generated by the terminal T. In this second case illustrated in FIGS. 5A and 5B, it is assumed that the user positions the device 2 at: close vicinity: of an edge of the terminal T so that the antenna ATI is also within detection range of the magnetic field F emitted by the terminal T. In this example, the device 2 is here approximately positioned with regard to a lateral region Tb of an active face of the terminal T.

As already described: with reference to FIG. 3, the field lines 20 of the magnetic field F generated at the edge of the terminal T are closed and adopt a substantially circular, oval or lobe shape. This is why, in this second case illustrated in FIGS. 5A and 5B, a first part F1 of the magnetic field F reaches the antenna winding W1 by the lower face 2b of the device 2 while the second part F2 of the magnetic field F reaches the antenna winding W2 by the upper face 2a of the device 2. In other words, the magnetic field F1 excites the antenna winding W1 by crossing the respective winding plane PI from its lower face Pib to its upper face Pla , while the magnetic field F2 excites the antenna winding W2 by crossing the respective winding plane P2 from its upper face P2a to its lower face P2b. In this particular case, the incident magnetic fields F1 and F2 then tend to induce a current flowing in the direction of rotation SI respectively (counterclockwise in this example) and the direction of rotation S2 (clockwise in this example) in the parts W1 and W2 of the antenna. Since the windings W1 and W2 respect opposite winding directions, the displacements of electric charges induced in these two windings are added, thus contributing together to the generation of an induced current resulting from the excitation of the magnetic field F , The arrangement according to opposite winding directions of the antenna parts W1 and W2 therefore has the consequence of creating by magnetic induction a current in the ATI antenna when magnetic fields (or fluxes) are incident on opposite faces of the windings Wl, W2,

It follows that communication in the near field is possible between the device 2 and the terminal T in the particular case of FIGS. 5A-5B, that is to say when the device 2 is positioned at the edge of the magnetic field generated by terminal T so that the antenna parts W1 and W2 are magnetically excited via opposite faces. The processing module 10 of the component 6 is then able to detect one or more signals SG (FIG. 2) emitted by the terminal T from the current collected at the ends of the antenna ATI. Such detection occurs for example if the induced current reaches a predetermined threshold value.

More specifically, the processing module 10 is configured to detect an induced current from the first magnetic field Fl incident on the lower face Pib of the winding Wl and from the second magnetic field F2 incident on the upper face P2a of the winding W2, the faces Pib and P2a being opposite one another.

By limiting the collection of a current in the device 2 to the particular case of FIGS. 5A-5B or to similar cases, this advantageously avoids the fraudulent collection of information contained in the device 2, in particular by the "phishing" technique. .

It is understood, however, that the specifics of the magnetic field F capable of being generated by a reading terminal, in terms in particular of the shape or dimensions of the field lines, may vary as the case may be. In general, [Invention makes it possible to limit near-field communication as a function of the positioning of the antenna windings of the device 2 with respect to the magnetic fluxes emitted by the reading terminal. The arrangement of the antenna windings in opposite directions of rotation makes it possible to prevent near-field communication: in some. Case and to allow near field communication in other cases. By way of example, FIG. SA illustrates, in another form, the second case represented in FIGS. 5A-4B (case of device 2 positioned opposite a region at the edge of the terminal). Similarly, still by way of example, FIG. 8B illustrates, in another form, the first case represented in FIGS. 4A-4B (case of the device 2 positioned opposite a central region of the terminal).

In order to assist in understanding (Invention, FIGS. 6 and 7 represent the use of a near-field communication device 30 according to another exemplary embodiment. This device 30 differs from the device 2 previously described in that it includes an antenna AT2 consisting of two windings W3 and W4 of turns which are wound in the same direction of rotation.

Thus, in the first case of FIG. 6 (analogous to FIGS. 4a-4b) where the device 30 is positioned opposite a central region of the terminal T, magnetic fields F3 and F4 of the magnetic field F excite this time the windings W3 and W4 in the same direction (i.e., from top to bottom in this example). Consequently, in this first case, a current can be generated by magnetic induction in the antenna AT2, thus authorizing a near field communication between the device 30 and the terminal T.

Conversely, in the second case of the figure? (analogous to FIGS. 5a-5b) where the device 30 is positioned opposite a region bordering the terminal T, magnetic fields F3 and F4 of the magnetic field F this time excite the windings W3 and W4 in opposite directions ( namely, from bottom to top and from top to bottom respectively, in this example). Consequently, in this second case, a current cannot be generated by magnetic induction in the antenna AT2, thus preventing near-field communication between the device 30 and the terminal T.

Furthermore, as indicated above with particular reference to FIG. 1, the antenna windings W1 and W2 of the device 2 extend in respective winding planes PI and P2, these planes being parallel with respect to one another. to the other. In the particular case of FIG. 1, the planes PI and P2 are combined. According to a variant shown diagrammatically in FIG. 9, the winding planes PI and P2 specific to the antenna windings W1 and W2 can be parallel and distinct from one another. The spacing between the two winding planes can be adapted by a person skilled in the art according to each case.

Referring to Figures 1 and 10, a method of manufacturing a communication device according to the invention is now described according to a particular embodiment. It is assumed, for example, that the manufacturing process makes it possible to manufacture the device 2 described above (Figures 1-2).

In this particular example, the method comprises during a supply step E2 supplying (or forming) a substrate 8. This substrate is here formed of an insulating material (in plastic for example) and may have mechanical characteristics adapted to the formation of a card.

During a positioning step E4, the electronic component 6 described above is positioned (and possibly fixed) on or in the substrate 8.

During a training step E6, the ATI antenna as previously described is formed on or in the substrate 8. In this example, the ATI near field communication antenna thus formed (E6) comprise a first winding W1 and a second winding W2 connected together in series, each winding comprising at least one conductive turn L1, L2 formed in a winding plane PI, P2, these winding planes specific to each winding being parallel with respect to the 'other (combined in this example). In addition, the windings W1 and W2 are formed in step E6 so that when an induced current flows through the antenna ATI from one end to the other through the windings W1 and W2, the current flows according to a first direction of rotation in each turn Li of the first winding and flows in a second direction of rotation, opposite to the first direction of rotation, in each turn L2 of the second winding.

More generally, during the training step E6, the ATI antenna thus formed may comprise at least a first winding and at least a second winding connected together in series, each winding comprising at least one conductive turn formed in a plane winding, said winding planes specific to each winding being parallel to each other; the said winding being formed so that when an induced current travels the antenna from one end to the other through the said windings, the current flows according to a first direction of rotation in each turn of said at least one first winding and flows according to a second direction of rotation, opposite to the first direction of rotation, in each turn of said at least one second winding. In other words, the formation step E6 is carried out so that the respective winding planes of said at least one first winding and of said at least one second winding each comprising an upper face and a lower face; and said at least one first winding and said at least one second winding are formed so that when a magnetic flux is incident on the upper faces of the winding planes of said at least one first winding and said at least one second winding or incident on the lower faces ·· of the winding planes of said at least one first winding and of said at least one second winding, the current (or the displacement of electric charges) induced in said at least one first winding and the current (or the displacement of electric charges) induced in said at least one second winding cancel each other out.

Once the ends of the ATI antenna are electrically connected to the electronic component 6, it is possible to carry out a covering step E8 aimed at covering the antenna Al and the electronic component 8 with a protective coating (insulating layer, plastic or other ). On the other hand, as described previously in the first case illustrated in FIGS. 4A-4B, the incident magnetic fields F1 and F2 tend to induce charge displacements which oppose each other, thus partially or totally canceling the current resulting from the excitation of the magnetic field F. In certain cases, the cancellation of the charge displacements can however not be total but lead to the induction of a negligible global current, that is to say less than a threshold value predetermined which is necessary, for example, to be detected or exploited by the component 6. In the case where the cancellation is not total, the global induced current resulting from the opposition of the charge displacements is a function of the configuration of the windings W1 and W2 of the ATI antenna (Figure 1), and more particularly of the surface defined by each turn of the windings W1 and W2.

According to a particular example, the accumulation - denoted CM1 - of the surfaces defined respectively by each turn L1 of the first winding W1 and the accumulation - denoted CM2 - of the areas defined respectively by each turn L2 of the second winding W2 (FIG. 1) are substantially equal. According to a particular example, the cumulations CM! and CM2 are such that CM1 is equal to CM2 at plus or minus 20% (a ratio of 20% maximum is tolerated). Any difference between CM1 and CM2 can result in an incomplete cancellation of the total induced current.

A surface defined by a turn corresponds to the surface entwined by this turn in the winding plane. The cumulation CM1 (and respectively CM2) therefore corresponds to the surface: equivalent defined by the set of turns of the first (and respectively second) winding. By way of example, FIG. 11 illustrates the configuration of the ATI antenna of the device 2 (FIG. 1) according to a particular embodiment. In this example, the first winding W1 is composed of a single conductive turn Lia while the second winding W2 is composed of 3 conductive turns L2a, L2b and LZc, the two windings W1 and W2 respecting opposite directions of winding. The magnetic fields F1 and F2 induce here collectively a current I flowing in the direction of rotation SI in the first winding W1 and in the direction of rotation S2 in: the second winding W2. In the example shown in FIG. 11, the first cumulative surface GM1 is equal to the surface defined by the single turn Lia of the first winding W1. Likewise, the second cumulative surface CM2 is equal to the sum of the surfaces; defined respectively by the turns L2a, L2b and L2c of the second winding W2. ..According to a particular example, CM1 is equal to CM2 within plus or minus 20%, or even: plus or minus 10% or 5%. Note also that: the embodiments described in this document relate to a near-field communication device 2 comprising two: windings W1, W2 respecting opposite winding directions. The invention can however be applied to such a device comprising two or more windings, so that there are at least two windings in opposite directions, that is to say at least one winding in a first '. winding direction ... and had at least one winding in a second winding direction, opposite to the first winding direction, in a similar manner to what is described above.

A person skilled in the art will understand that the embodiments and variants described above only constitute non-limiting examples of implementation of the invention. In particular, a person skilled in the art can envisage any adaptation or combination of the embodiments and variants described above in order to meet a very specific need.

Claims (13)

1. Contactless communication device (2) comprising a near field communication antenna (ATI), said antenna comprising: a first winding (Wl) and a second winding (W2) connected together in series / each winding comprising at least one conductive turn (LL, L2) formed in a winding plane (PI, P2), said winding planes of the first and second windings being parallel to one another; said windings being arranged so that when an induced current flows through the antenna from one end to the other through said windings, the current flows in a first direction of rotation (SI) in each turn of said first winding and flows according to a second direction of rotation (S2), opposite to the first direction of rotation, in each turn of said second winding. 2. Device according to claim 1, wherein the first direction of rotation is clockwise and the second direction of rotation is counterclockwise. 3. Device according to claim 1 or 2, wherein the respective winding planes of said first winding and said second winding each have an upper face and a lower face, said first and second windings being arranged in opposite winding directions of so that when a magnetic field is incident on the upper faces of the winding planes of said first winding and of said second winding or incident on the lower faces of the winding planes of said first winding and of said second winding, the current induced in said first winding and the current induced in said second winding cancel each other out. 4. Device according to any one of claims 1 to 3, in which the first and second windings are configured so that the total of the surfaces defined by each turn of the first winding is equal, within plus or minus 20%, to accumulation of the surfaces defined by each of the second winding. 5. Device according to any one of claims 1 to 4, in which the antenna comprises a continuous electrically conductive track forming, in series with respect to each other, said first winding and said second: winding 6. Device according to claim 5. wherein the conductive track is a conductive fit or a conductive material deposited on a substrate. 7. Device according to any one of claims 1 to 6, wherein the winding plane of the first winding and the winding plane of the second winding are merged with each other. 8. Device according to any one of claims 1 to 7, wherein the communication device is a smart card in which said antenna is integrated. 9. Device according to any one of claims 1 to 8, in which the communication device further comprises a processing module connected to the two ends of the antenna, the processing module being configured to detect, from a current induced in the antenna by a magnetic field, at least one signal received by the antenna according to near-field communication. 10. Device according to any one of claims i to 9, in which the processing module is configured to detect said induced current from a first magnetic field incident on a first winding face of said first winding and from a second magnetic field incident on the second winding face of said second winding, said first face being opposite to said second face. 11. A method of manufacturing a contactless communication device, comprising the following steps: - supply (E2) of a substrate (8); and - formation (E6), on or in the substrate, of a near-field communication antenna (ATI), the antenna comprising a first winding (Wl) and a second winding (W2) connected together in series, each winding comprising at least one conductive turn (11, LZ) 'formed in a winding plane (PI, P2), said winding planes of the first and second windings being parallel to one another; said husks being formed so that when an induced current flows through the antenna from one end to the other: through said windings, the current flows in a first direction of rotation in each turn of said first husk and flows in a second direction of rotation, opposite to the first direction of rotation, in each turn of said second hoarse. 12. The method of claim 11, further comprising a positioning step (E4) of an electronic component (6) on or in the substrate, the antenna being electrically connected to the electronic component. 13. The method of claim 11 or 12, the respective winding planes of said first winding and said second winding each comprising an upper face and a lower face, and wherein, during the forming step (E6), said first and second windings are formed in opposite winding directions so that when a magnetic field is incident on the upper faces of the winding planes of said first winding and said second winding or incident on the lower faces of the winding planes from said first winding and from said second winding, the current induced in said a first winding and the current induced in said second winding cancel each other out.