FR3153443A1 - Tunable resonant frequency chip document. - Google Patents

Abstract

The invention relates to a smart document (100) with a tunable resonant frequency, comprising: • a first antenna (110), for carrying out exchanges with a card reader, and having a first resonant frequency. It is characterized in that it further comprises: • a second antenna (120), comprising a first set of turns (121) and at least one capacitive loop (122), and having: o a first value of a second resonant frequency when an electrical conductor is at a distance from the capacitive loop, this first value being greater than the first resonant frequency, o a second value of a second resonant frequency when an electrical conductor is near the capacitive loop, this second value being substantially equal to the first resonant frequency.

Description

Tunable resonant frequency chip document.

The present invention relates to the field of smart documents, in particular those with tunable resonant frequency.

A smart card contains a resonant electronic circuit that has a resonant frequency. This resonant frequency can be standardized, for example, for exchanges between the card and a reader in the identity domain, including for secure access, or banking.

There are electronic circuits that resonate at two resonant frequencies. For example, document CA3009493 discloses a ticket reader comprising an antenna that includes a first loop tuned to a first frequency and a second loop tuned to a second frequency, which makes it possible to interact with several transport cards.

The present invention, for its part, aims at a resonant circuit with tunable resonant frequency, for a use very different from that of the prior art cited above.

Indeed, more and more applications are emerging for communicating between a smart document and a smartphone. Many uses are now being proposed, in the banking sector for payment, or in the identity sector for authentication, identification, or signing documents using a smartphone and an identity card.

In these areas, it is common to at least go through an enrollment phase, which involves biometrics. The biometrics market is growing, but a current obstacle to this deployment is the need to enroll the user's fingerprint, particularly due to the time required for this biometric enrollment step, typically several tens of seconds.

A known solution at this stage is to carry out this enrollment step using a cradle, which is a support that allows the smart document to be correctly positioned in relation to the smartphone's NFC antenna. The cradle can integrate an antenna to improve communication between the smart document and the smartphone.

• du fait de la petite taille de l’antenne du smartphone au regard des antennes des terminaux de paiements ou de lecteur de bureau ;
• du fait de la présence d’une batterie et de l’environnement métallique à proximité de l’antenne dans le smartphone qui peuvent perturber les ondes électromagnétiques ;
• du fait de la puissance disponible dans un smartphone, qui peut être relativement faible ;
• du fait du positionnement différent de l’antenne NFC dans chaque smartphone, qui fait qu’un même berceau aura des effets différents selon le smartphone ;
• etc.

But this solution is not optimal and there are still interoperability problems between a smart document and the smartphone, for example for at least one of the following reasons:

• due to the small size of the smartphone antenna compared to the antennas of payment terminals or desktop readers;
• due to the presence of a battery and the metallic environment near the antenna in the smartphone which can disrupt electromagnetic waves;
• due to the power available in a smartphone, which can be relatively low;
• due to the different positioning of the NFC antenna in each smartphone, which means that the same cradle will have different effects depending on the smartphone;
• etc.

However, there is a need for precise relative positioning of the smart document and the smartphone, more precisely of their respective antennas, so that the coupling between the radiofrequency circuits is optimal in order to avoid reading or enrollment errors.

In this context, according to a first of its objects, the present invention relates to a smart document (100) with tunable resonance frequency, comprising:

• a card body (101),

• an external face,

• a module (140), comprising a secure element,

• a first antenna (110), configured to be able to carry out a transfer of data and energy between the module (140) and a card reader when the smart document (100) is in the field of said reader and having a first resonance frequency.

It is essentially characterized in that it also includes:

• a second antenna (120), comprising:

or a first set of turns (121),

o a first set of at least one capacitive loop (122), connected with the first set of turns (121),

• such that the second antenna (120) has:

o a first value of a second resonant frequency when the smart document (100) is in the field of said reader and an electrical conductor is at a distance greater than a threshold value from the capacitive loop, the first value of the second resonant frequency being greater than the first resonant frequency,

o a second value of a second resonant frequency when the smart document (100) is in the field of said reader and an electrical conductor is at a distance less than a threshold value from the capacitive loop, the second value of the second resonant frequency being substantially equal to the first resonant frequency.

It can be provided that the second antenna (120) further comprises at least one of:

• a second set of turns (123),

• a second set of at least one capacitive loop (124), connected with the first set of turns (121) or with the second set of turns (123).

A concentrator (130) may further be provided, connected to the first antenna (110).

It can be predicted that:

• The first antenna (110) and the second antenna (120) are arranged on a respective support; or

• The first antenna (110) and the second antenna (120) are arranged on the same support comprising two opposite faces, such that:

i. The first antenna (110) and the second antenna (120) are arranged on the same face of the support,

ii. The first antenna (110) and the second antenna (120) are arranged on a respective face of the support,

iii. at least one of the first antenna (110) and the second antenna (120) is arranged on either side of the support.

It can be provided that the second antenna (120) is configured so that, when the smart document (100) is in the field of said reader and an electrical conductor is at a distance less than a threshold value from the capacitive loop, the coupling between said reader and said smart document (100) is optimal.

It is also possible to provide a biometric module (160), in galvanic or electromagnetic connection with the module (140).

It can be provided that the shape of the first set of at least one capacitive loop (122) locally matches the shape of the second set of at least one capacitive loop (124).

It can be provided that the shape of the first set of at least one capacitive loop (122) and the shape of the second set of at least one capacitive loop (124) locally form a set of at least one ripple.

It is also possible to provide a marking element arranged in line with at least one of the first set of at least one capacitive loop (122), and the second set of at least one capacitive loop (124), to mark the position of said set of at least one capacitive loop.

According to another of its objects, the invention also relates to a system comprising a smart document (100) according to the invention, and a card reader in the form of a smartphone (200).

Other characteristics and advantages of the present invention will appear more clearly on reading the following description given by way of illustrative and non-limiting example and made with reference to the appended figures.

Figures are not necessarily to scale. Some details may have been omitted or others enlarged for ease of understanding.

Figures

FIG. 1 illustrates an embodiment of a chip document according to the invention,

FIG. 2 illustrates another embodiment of a smart document according to the invention,

FIG. 3 illustrates a biometric enrollment with an embodiment of a smart document according to the invention,

FIG. 4 illustrates another embodiment of the shape of a first capacitive loop and a second capacitive loop according to the invention.

Detailed description

There FIG. 1 illustrates an embodiment of a smart document 100 according to the invention. In this case, the smart document 100 is a smart card. In a manner not illustrated, and not exhaustively, the smart document 100 may also be a passport or an identity card.

When the smart document 100 is a smart card, it can be implemented for banking, security or identity applications.

It comprises a card body 101 and an external face (not referenced in the figures).

Typically, it also includes a 140 module, which includes a secure element.

Finally, it also classically includes a first 110 antenna.

The first antenna 110 is for example known by the terminology “ID-1” in reference to the ISO/IEC 7810 standard in the field of smart cards.

The first antenna 110 is configured to be able to carry out a transfer of data and energy between the module 140 and a card reader when the smart document 100 is in the field of said reader.

The reader is for example an ad hoc device such as a terminal, for example a payment terminal when the chip document 100 is a bank card, or a smartphone type device 200.

The first antenna 110 is configured to be able to have a first resonant frequency. For example, the first resonant frequency is standardized, for example 13.56 MHz.

According to the invention, the smart document 100 further comprises a second antenna 120.

The second antenna 120 comprises a first set of turns 121. For example, the turns of the first set of turns 121 are concentric with respect to the module 140.

The second antenna 120 comprises a first set of at least one capacitive loop 122, connected with the first set of turns 121, so that the first set of at least one capacitive loop 122 can have an influence on the resonance frequency of the second antenna 120 in the following manner. Those skilled in the art will understand that the antenna technology can be wire (copper), etched or additive (copper, aluminum, silver).

The second antenna 120 has two resonance frequencies, i.e. two values of a second resonance frequency depending on the conditions of use, when the smart document 100 is in the field of the reader:

When an electrical conductor is at a distance greater than a threshold value from the first set of at least one capacitive loop 122, then the second antenna 120 has a first value of the second resonant frequency, greater than the first resonant frequency.

Preferably, it is provided that the first value of the second resonant frequency is at least 3 MHz, and preferably at least 5 MHz higher than the first resonant frequency. For example, for a first resonant frequency of 13.56 MHz, the first value of the second resonant frequency is at least 16 MHz, and preferably greater than 20 MHz.

Thus, in use by a standard reader, when an electrical conductor is at a distance from the first set of at least one capacitive loop 122, i.e. at a distance greater than a threshold value, then the smart document 100 resonates at the frequency of the first resonance frequency, and the presence of the second antenna 120 is transparent to the operation of the smart document 100.

On the other hand, when an electrical conductor is at a distance less than a threshold value from the first set of at least one capacitive loop 122, then the second antenna 120 has a second value of the second resonant frequency, the second value of the second resonant frequency being substantially equal to the first resonant frequency.

By "substantially equal" is meant that the second value of the second resonant frequency is equal to the first resonant frequency plus or minus 20%.

For example, the electrical conductor is a piece of metal, or a finger of the user, in particular placed on the smart document 100, as illustrated in the FIG. 3 .

Preferably, to obtain the second value of the second resonant frequency, the electrical conductor is as close as possible to the first set of at least one capacitive loop 122, and in particular in contact with the card body 101 of the smart document 100, as illustrated in the FIG. 3 .

Thus, in use by a standard reader, when an electrical conductor is close to the first set of at least one capacitive loop 122, i.e. at a distance less than a threshold value, then the second antenna 120 resonates at the second value of the second resonant frequency.

In this case, when the smart document 100 is in the field of the reader and an electrical conductor is at a distance less than a threshold value from the capacitive loop, then the second antenna 120 resonates at the second value of the second resonant frequency, which allows optimal coupling between the reader and the smart document 100, the second antenna 120 functioning as an electromagnetic waveguide making it possible to concentrate the waves from the reader towards the first antenna 110 in the case of a galvanically connected chip or towards the module 140 in the case of an inductively coupled chip.

Preferably, it is provided that the second antenna 120 further comprises at least one of:

• a second set of turns 123,

• a second set of at least one capacitive loop 124, connected with the first set of turns 121 or with the second set of turns 123.

By conciseness, we mean indistinctly “first set of at least one capacitive loop 122” and “first capacitive loop 122”, as well as “second set of at least one capacitive loop 124” and “second capacitive loop 124”.

The first capacitive loop 122 and the second capacitive loop 124 form a capacitive connection pad. The presence or absence of an electrical conductor near or in contact with this connection pad determines the capacitance of the electrical circuit, which amounts to selectively activating the first value of the second resonant frequency or the second value of the second resonant frequency.

Preferably, the shape of the first set of at least one capacitive loop 122 locally matches the shape of the second set of at least one capacitive loop 124, as illustrated in the FIG. 1 and on the FIG. 2 .

In a non-limiting example, the shape of the first set of at least one capacitive loop 122 and the shape of the second set of at least one capacitive loop 124 locally form a set of at least one ripple, as illustrated in the FIG. 1 and on the FIG. 2 .

It can also be provided that the shape of the first set of at least one capacitive loop 122 and the shape of the second set of at least one capacitive loop 124 locally form a set of staircase steps, as illustrated in the FIG. 4 .

the shape of the first set of at least one capacitive loop 122 locally matches the shape of the second set of at least one capacitive loop 124.

Advantageously, the shape and arrangement of the first set of at least one capacitive loop 122 and the shape and arrangement of the second set of at least one capacitive loop 124 are such that when an adult finger is placed on the first set of at least one capacitive loop 122, then the finger also at least partially covers the second set of at least one capacitive loop 124, so as to present desensitization to the position of the finger.

For this purpose, it can be provided that the card body 101 comprises a marking element 170, as illustrated in the FIG. 3 , arranged in line with at least one of the first set of at least one capacitive loop 122 and the second set of at least one capacitive loop 124, to mark the position of said set of at least one capacitive loop.

The marking element 170 is a graphic representation which is presented for example in the form of a self-adhesive label or a marking directly on the surface of the card, for example by embossing, engraving, painting, etc.

For example, not shown, the marking element 170 has an oval shape or a fingerprint, so as to facilitate the positioning of the user's finger on the face of the smart document 100 during biometric enrollment.

Furthermore, it can be provided that the second set of turns 123 is concentric with respect to the module 140, as illustrated for example in the FIG. 1 . More generally, it can be provided that at least one of the first set of turns 121 and the second set of turns 123 is concentric around the module 140, in particular if the module 140 itself comprises an antenna.

It can be provided that the smart document 100 further comprises a concentrator 130, connected to the first antenna 110. The concentrator 130 optimizes the coupling between the module 140 and the first antenna 110. Generally the module 140 comprises an antenna (not illustrated) and the concentrator 130 is preferably concentric with the antenna of the module 140.

According to the invention, the coupling between the module 140 and the first antenna 110 can be either galvanic or inductive.

It can be provided that the smart document 100 comprises a set of at least one antenna support.

In a first variant, the first antenna 110 and the second antenna 120 are arranged on a respective support.

In a second variant, the first antenna 110 and the second antenna 120 are arranged on the same support, the support comprising two opposite faces.

• sur la même face du support, ou
• une face respective du support.

In this case, the first antenna 110 and the second antenna 120 can be arranged:

• on the same side of the support, or
• a respective face of the support.

It is also possible to provide that at least one of the first antenna 110 and the second antenna 120 is arranged on either side of the support.

• le premier ensemble de spires 121 et le premier ensemble d’au moins une boucle capacitive 122 sont disposés sur une face du support,
• le deuxième ensemble de spires 123 et le deuxième ensemble d’au moins une boucle capacitive 124 sont disposés sur l’autre face du support,
• l’épaisseur du premier ensemble de spires 121 et du premier ensemble d’au moins une boucle capacitive 122 peut être différente de l’épaisseur du deuxième ensemble de spires 123 et du deuxième ensemble d’au moins une boucle capacitive 124 ;
• le premier ensemble de spires 121 et le deuxième ensemble de spires 123 étant en connexion électrique par un dispositif de liaison électrique 150.

According to a non-limiting variant, it can be provided that the smart document 100 comprises an antenna support on which the second antenna 120 is arranged and that:

• the first set of turns 121 and the first set of at least one capacitive loop 122 are arranged on one face of the support,
• the second set of turns 123 and the second set of at least one capacitive loop 124 are arranged on the other face of the support,
• the thickness of the first set of turns 121 and of the first set of at least one capacitive loop 122 may be different from the thickness of the second set of turns 123 and of the second set of at least one capacitive loop 124;
• the first set of turns 121 and the second set of turns 123 being electrically connected by an electrical connection device 150.

Depending on the antenna technology implemented, the electrical connection device 150 is a via (or crimp ) or a bridge (or jump ).

In one embodiment, the smart document 100 further comprises a biometric module 160, as illustrated in the FIG. 1 The biometric module 160 is in galvanic or electromagnetic connection with the module 140. By “electromagnetic connection” is meant any one of the connections (or indistinctly coupling) among: an electrical connection, a capacitive connection, an optical connection and an inductive connection.

For biometric enrollment, illustrated in the FIG. 3 , the user can act in the following ways:

He places his 100 chip document on a stable support then his 200 smartphone, reader server, on the 100 chip document.

The user then places a finger to be enrolled on the biometric module (or sensor) 160 and another finger on at least one of the first set of at least one capacitive loop 122 and the second set of at least one capacitive loop 124.

Since the finger is an electrical conductor, the second antenna 120 then has the second value of a second resonant frequency and acts as a waveguide between the smartphone 200 and the module 140 of the smart document 100, which promotes enrollment thanks to the optimal coupling between the smartphone 200 and the module 140 of the smart document 100. The coupling can be between the second antenna 120 and the antenna of the module 140 (for the modules 140 with inductive connection), or between the second antenna 120 and the first antenna 110 (for the modules 140 with galvanic connection).

By removing the user's finger from the second antenna 120, the smart document 100 returns to its first resonance frequency and can be used conventionally for banking, security or identity purposes.

Thanks to the present invention, the coupling is optimal between a reader and the smart document, thanks to a second antenna 120 which allows frequency tuning and which is advantageously integrated into said document. Thus, it is not necessary to resort to a support / template / label, etc. which would integrate such a second antenna.

The second antenna 120 is not necessarily physically accessible from outside the smart document 100.

In particular when the smart document 100 is a smart card 100, it can be provided that the second antenna 120, in particular at least one of the first set of turns 121 and the second set of turns is physically accessible from the outside of the smart card 100, in this case via the edge thereof.

The present invention promotes interoperability between a reader (smartphone) and a smart document 100, by punctually increasing the performance of the radiofrequency circuit of the smart document 100.

Nomenclature

100 Chip Document

101 card bodies

110 first antenna

120 second antenna

121 first set of turns

122 first capacitive loop

123 second set of coils

124 second capacitive loop

130 concentrator

140 module

150 electrical connection device

160 biometric module

170 marking element

200 smartphones

Claims (10)

Tunable resonant frequency chip document (100), comprising:

• a card body (101),
• an external face,
• a module (140), comprising a secure element,
• a first antenna (110), configured to be able to carry out a transfer of data and energy between the module and a card reader when the smart document (100) is in the field of said reader and having a first resonance frequency;

characterized in that it further comprises

• a second antenna (120), comprising:
  • a first set of turns (121),
  • a first set of at least one capacitive loop (122), connected with the first set of turns (121),
• such that the second antenna (120) has:
  • a first value of a second resonant frequency when the smart document (100) is in the field of said reader and an electrical conductor is at a distance greater than a threshold value from the capacitive loop, the first value of the second resonant frequency being greater than the first resonant frequency,
  • a second value of a second resonant frequency when the smart document (100) is in the field of said reader and an electrical conductor is at a distance less than a threshold value from the capacitive loop, the second value of the second resonant frequency being substantially equal to the first resonant frequency.

The smart document (100) of claim 1, wherein the second antenna (120) further comprises at least one of:

• a second set of coils (123),
• a second set of at least one capacitive loop (124), connected with the first set of turns (121) or with the second set of turns (123).

A smart document (100) according to any preceding claim, further comprising a hub (130), connected to the first antenna (110) and arranged around the module (140). A smart document (100) according to any preceding claim, wherein:

• Either the first antenna (110) and the second antenna (120) are arranged on a respective support;
• Either the first antenna (110) and the second antenna (120) are arranged on the same support comprising two opposite faces, such that:
  1. The first antenna (110) and the second antenna (120) are arranged on the same face of the support,
  2. The first antenna (110) and the second antenna (120) are arranged on a respective face of the support, or
  3. at least one of the first antenna (110) and the second antenna (120) is arranged on either side of the support.

A smart document (100) according to any preceding claim, wherein the second antenna (120) is configured such that when the smart document (100) is in the field of said reader and an electrical conductor is at a distance less than a threshold value from the capacitive loop, the coupling between said reader and said smart document (100) is optimal. A smart document (100) according to any preceding claim, further comprising a biometric module (160), in galvanic or electromagnetic connection with the module (140). Smart document (100) according to any one of claims 2 to 6, in which the shape of the first set of at least one capacitive loop (122) locally matches the shape of the second set of at least one capacitive loop (124). A smart document (100) according to claim 7, wherein the shape of the first set of at least one capacitive loop (122) and the shape of the second set of at least one capacitive loop (124) locally form a set of at least one ripple. A smart document (100) according to any preceding claim, comprising a marking element arranged in line with at least one of the first set of at least one capacitive loop (122), and the second set of at least one capacitive loop (124), for marking the position of said set of at least one capacitive loop.
System comprising a smart document (100) according to any one of the preceding claims, and a card reader in the form of a smartphone (200).