EP1886382A2

EP1886382A2 - Electronic entity with magnetic antenna

Info

Publication number: EP1886382A2
Application number: EP06764680A
Authority: EP
Inventors: Yves Eray; Guy Enouf
Original assignee: Oberthur Card Systems SA France
Current assignee: Idemia France SAS
Priority date: 2005-05-25
Filing date: 2006-05-24
Publication date: 2008-02-13
Also published as: FR2886466B1; US20090315799A1; WO2006125916A3; FR2886466A1; US8378911B2; WO2006125916A2

Abstract

The invention concerns an electronic entity (2) comprising an electronic circuit (4) whereto is connected an antenna. The antenna includes a loop (6) electrically connected to the electronic circuit (4) and a resonator (8) coupled with said loop (6).

Description

Magnetic antenna electronic entity

The invention relates to an electronic entity with a magnetic antenna.

Electronic entities of this type generally comprise an electronic circuit having in particular two terminals to which is connected a magnetic antenna generally formed of a winding of several turns made of conductive material.

This type of electronic entity covers in particular contactless microcircuit cards (where the magnetic antenna constitutes the only means of communication of the microcircuit with the outside) and "dual" or "hybrid" microcircuit cards (where contacts electrical devices are provided on one of the faces of the card which provide an alternative mode of communication of the microcircuit with the outside). In microcircuit cards of one or the other type, the turns of the magnetic antenna are generally made in the form of windings of copper wires or conductive tracks, arranged in both cases at the same time. within the layers physically constituting the map.

In all cases, in order to increase the induced current that the magnetic antenna delivers to the electronic circuit, the designer of the electronic entity is forced to increase the number of turns to increase the magnetic flux through the antenna .

The increase in the number of turns, however, quickly raises problems: on the one hand, the increase in the area that carries the turns relative to the available surface can pose congestion problems, especially since the geometry of the turns is relatively fixed, which is particularly troublesome in the case of small electronic entities; on the other hand, the reduced number of surfaces generally available for receiving the turns (often for example deposited in the same plane) necessitates bridge techniques for looping the electrical circuit, as described for example in the patent application FR 2 769,390.

The aim of the invention is to limit these problems and thus to propose a magnetic antenna electronic entity whose design allows easier integration of the antenna into the electronic entity, for example by a more great freedom of its design and a decrease of its surface, without that compromising the performances of this one.

Thus, the invention proposes an electronic entity comprising an electronic circuit to which an antenna is connected, characterized in that the antenna comprises a loop electrically connected to the electronic circuit and a resonator formed of a conductive winding with free ends and coupled to said loop.

The introduction of the resonator coupled to the loop makes it possible, on the one hand, to amplify the electrical signals traversed by it and, on the other hand, a greater flexibility in the design of the antenna.

The resonator for example is coupled to the loop by capacitive coupling, which allows a particularly interesting operation of the antenna as explained below.

To do this, the resonator comprises for example a turn located opposite the loop on at least part of its perimeter.

To maximize the capacitive coupling, the turn is located opposite the loop on almost all of its perimeter and / or the turn and the loop are located at a distance of less than 0.5 mm on said perimeter portion.

According to one possible embodiment, the resonator may comprise a plurality of turns. In this case, in order to obtain a particularly efficient resonator, the turns are separated in pairs by a distance of less than 0.5 mm.

According to a possible embodiment, the loop is located inside the resonator. According to another embodiment, the resonator is located inside the loop.

The loop and the resonator can be deposited on the same plane support.

In a variant, the loop is made in a first plane, the resonator is made in a second plane different from the first plane and the resonator is located at the right of the loop, for example a median coil of the resonator is placed at the right of the loop for obtain a particularly effective coupling.

The resonance frequency of the resonator alone (or frequency of the vacuum resonator) is, for example, not more than 10% greater than a communication frequency of the electronic circuit with the devices outside electronics (eg a contactless reader). Thus, coupling the loop involving a resonance frequency of the circuit as a whole slightly less than the resonance frequency of the resonator alone, the resonant frequency of the circuit as a whole is particularly adapted to take advantage of the amplification phenomenon.

The antenna considered here is a magnetic antenna, that is to say an antenna that essentially generates an induction current.

For example, the electronic circuit operates at a communication frequency less than 100 MHz. Said communication frequency may especially be between 1 MHz and 50 MHz, in particular between 13 MHz and 15 MHz.

In the latter case, the resonance frequency of the resonator alone can then advantageously be between 13.6 MHz and 17 MHz.

The external dimensions of the electronic entity are for example less than 100 mm, or even less than 30 mm. The resonator is particularly interesting in these conditions where the available surface is reduced.

The resonator can then advantageously comprise more than ten turns. The electronic entity can thus be an electronic pocket entity. This is for example a microcircuit card. In this case, the antenna can advantageously only extend over approximately half of the surface of the card.

Other characteristics and advantages of the invention will become apparent in the light of the description which follows, made with reference to the appended drawings in which:

FIG. 1 represents a first example of an electronic entity produced in accordance with the teachings of the invention;

FIG. 2 represents an equivalent electronic diagram for modeling the general principles of the electrical behavior of the electronic entity of FIG. 1;

FIG. 3 represents an antenna used in a second embodiment of the invention; FIG. 4 represents an antenna according to a third embodiment of the invention;

- Figure 5 shows a top view of a support carrying an antenna according to a fourth embodiment of the invention; - Figure 6 shows in a view from below the support of Figure 5;

FIG. 7 represents a fifth example of implementation of the invention;

FIG. 8 represents an antenna according to a sixth example of implementation of the invention; FIG. 9 represents an antenna according to a seventh exemplary implementation of the invention;

FIG. 10 represents an antenna according to an eighth exemplary implementation of the invention;

FIG. 11 represents an antenna according to a ninth exemplary implementation of the invention;

FIG. 12 represents a first part of an antenna according to a tenth example of implementation of the invention;

FIG. 13 represents a second part of the antenna in the tenth embodiment of the invention; FIG. 14 represents an antenna according to an eleventh embodiment of the invention

FIG. 15 represents a first part of an antenna according to a twelfth example of implementation of the invention;

- Figure 16 shows a second part of the antenna in the twelfth embodiment of the invention.

FIG. 1 schematically represents a first example of an electronic entity produced in accordance with the teachings of the invention. This is a microcircuit card 2 which has been shown the essential elements for understanding the invention, namely an electronic circuit 4 (such as an integrated circuit) at the terminals of which is connected an antenna formed of on the one hand by a loop 6 and on the other hand by a resonator 8.

The electronic circuit 4 is for example received in a module that is just deposited on the electronic entity 2 in order to make the connection of the circuit 4 to the antenna (here in practice to the loop 6), for example as described in the document FR 2 863 747.

The antenna allows the electronic circuit 4 to communicate remotely with other electronic devices such as for example a card reader. The antenna is a magnetic antenna which allows not only the exchange of information between the electronic circuit 4 and the external electronic device at a predetermined frequency, but also the remote power supply of the electronic circuit 4.

For handheld portable electronic entities of common dimensions (namely of the order of or less than 10 cm), which exchange information with a range of the order of one meter or even a few meters, such an antenna works in a magnetic field (that is to say, at most at a distance of the order of the wavelength) up to frequencies of the order of 100 MHz (where the wavelength is 3 m) . The electronic entity 2 described here is for example a non-contact type card which can exchange information with an external electronic device, for example such as according to the ISO 14 443 standard on a carrier with

13.56 MHz.

The loop 6 is here made by a single turn and thus forms, as already indicated, a conductive circuit connected at each of its ends to one of the terminals of the electronic circuit 4.

The loop 6 is for example made by etching a copper track on a support 10 made of dielectric material which constitutes a layer of the electronic entity 2, particularly in the case described here where the electronic entity is a microcircuit card. . Other embodiments of the loop 6 are naturally conceivable, such as for example the deposition of a copper wire or a conductive ink.

The resonator 8, also formed here by conductive tracks (for example obtained by copper etching with a width of about 0.15 mm, for example between 0.12 mm and 0.2 mm, and a spacing of about 0 , 15 mm, for example between 0.12 mm and 0.2 mm), is arranged at a sufficiently small distance from it to allow capacitive coupling between these two elements. In the example shown in Figure 1, the resonator 8 is formed of straight portions which form a conductive spiral with free ends, formed of two turns in the case described.

One of the turns of the resonator 8 (the outer turn in FIG. 1) is located opposite the loop 6, on a substantial part of at least its perimeter (here almost all of it), and at a short distance of this (ie less than 0.5 mm and for example less than 0.15 mm) in order to ensure a good capacitive coupling.

As a variant, the proximity of the turn of the resonator 8 and of the loop 6 can take place only over a part of their perimeter (for example of the order of half of this one), which in certain cases ensures sufficient capacitive coupling.

According to another variant, the capacitive coupling could be achieved by connecting the loop 6 and the resonator 8 by means of a capacitor. The arrangement of the resonator 8 in the form of turns generates an inductive behavior of this element, whereas the proximity of the portions (here rectilinear) of the spiral two by two and the absence of looping (due to the free ends of the spiral) induced a capacitive behavior.

The resonator thus has a high overvoltage coefficient at a resonant frequency.

This resonance overvoltage coefficient will advantageously be used to amplify, at the communication frequency used, the signals to which the resonator is subjected. These amplified signals are transmitted to the loop by capacitive coupling. To do this, the resonator 8 is designed (by the arrangement of these tracks, the width thereof and the spacing between them, and by the materials used for the resonator 8 and the support 10) to have inductive and capacitive effects which cause resonance at a frequency close to the communication frequency of the electronic circuit, as illustrated in the examples described below. For the calculation of the inductance and capacitance values generated for given characteristics of the resonator, reference is made for example to the documents "Inductance Calculation Techniques, part II: Calculations and Handbook Methods", by Marc T. Thompson, in Power Control and Intelligent Motion, December 1999, "Design and Optimization of a 10 nH Square-Spiral Inductor for Si RF ", Tuan Huu Bui, University of North Carolina, October

1999, "Capacity Limits and Matching Properties of Integrated Capacitors",

Robert Aparicio and AI Hajimiri, in IEEE Journal of Solid State Circuits, Vol. 37 No.

3, March 2002, "Interdigital sensors and transducers" by Alexander V. Mamishev et al., In Proceedings of the IEEE, Vol. 92, No. 5, May 2004 and "Be Careful of Self and Mutual Inductance Formulae" by H. Kim and C. C-P. Chen, University of

Wisconsin, Madison, 2001.

The use of a plurality of turns in the resonator, as is the case in the embodiment of the invention presented in FIG. 1, not only makes it possible to increase the inductive effect by increasing the length of the conductor used, but also the capacitive effect by the cooperation of each rectilinear portion of the resonator 8 with another rectilinear portion thereof.

Moreover, as for the loop 6, there are many possibilities for producing the resonator 8 other than the tracks of conductive material, such as for example the use of a copper wire (width between 0.088 mm and 0.15 mm). mm and with spacing between

0.112 mm and 0.2 mm) or the deposition of a conductive ink (width between 0.15 mm and 0.3 mm and with a spacing between 0.3 mm and 0.5 mm). Finally, although the resonator given by way of example above is imposed rectilinear portions, it is understood that one could use instead of curved portions.

FIG. 2 shows a possible equivalent electrical diagram for modeling the general principles of the electrical behavior of the electronic entity of FIG. 1, which makes it possible to easily understand the electrical operation thereof.

The electronic circuit 4 is conventionally represented by a resistor R | _C and a capacity C | _C in parallel. In the case where the electronic circuit is an integrated circuit, these data are generally provided by the manufacturer of the electronic circuit, or can be measured.

The loop 6 is represented mainly by the series combination of an inductor L ₈ and a resistor RB. To model also the cases where the loop 6 is formed of a plurality of turns, it is expected also an inter-turn capacity CB connected in parallel with the inductance L _B of the loop 6.

The resonator 8 is represented by an LC circuit which associates an inductance LR and a capacitance CR whose explanation of the physical origin is given above.

As indicated with reference to FIG. 1, the loop 6 and the resonator 8 are associated by capacitive coupling, which is represented in the equivalent diagram of FIG. 2 by the connection of the part representing the loop 6 (mainly inductance LB and resistance R ₈ ) to the part representing the resonator 8 (inductance L _R and capacitance CR) through a capacitor Cc corresponding to the capacitive coupling.

FIG. 3 represents a second example of an antenna according to the teachings of the invention, which is naturally associated with an electronic circuit as has been described with reference to FIG. 1 to form an electronic entity of the microcircuit card type.

Such an antenna is adapted here to a card type ID1, of dimensions 85.6 mm x 54 mm.

The antenna shown in FIG. 3 comprises a loop 36 formed by a single turn (intended to be connected at each of its ends to the electronic circuit) and a resonator 38 formed by about fifteen turns, the winding formed by these turns having free ends 31, 32.

All the elements of the antenna, namely the loop 36 and the resonator 38, are here formed in the same plane, for example by depositing on a support of dielectric material, for example paper or a plastic material (permittivity relative between 2 and 7).

The conductive tracks are here made of copper by etching.

This exemplary embodiment, produced here for a card having a dimension of 81 mm × 50 mm, makes it possible to obtain a capacitance of the CR resonator of 0.6165 pF and an inductance of the resonator L _R of 219.7 μH, which defines a frequency resonance circuit (i.e. resonator considered alone) of 13.678 MHz. The coupling with the loop having the effect of very slightly reducing the resonant frequency compared to the vacuum resonator, the antenna is particularly interesting for a microcircuit card whose electronic circuit communicates with the outside at a frequency of 13.56 MHz (for example a PHILIPS MIFAR PRO X electronic circuit).

The loop 36 naturally ends at each end intended to be connected to the electronic circuit by a connection pad 33, 34. Due to the use of a single turn for the loop 36 and a winding with free ends (c that is, without loopback) for the resonator 38, the antenna proposed in FIG. 3 does not require the use of a bridge. However, thanks to the use of the resonator, its magnetic performance is particularly good. FIG. 4 represents an antenna used in a third exemplary implementation of the invention, of design relatively close to the antenna described with reference to FIG.

Thus, as for the antenna described with reference to FIG. 3, the antenna of FIG. 4 comprises a loop 46 formed by a single turn provided at its two ends 43, 44 with connection pads to the electronic circuit.

Within the zone delimited by the loop 46, the antenna comprises a resonator 48 formed by the winding with free ends of about forty turns. Each turn is made by four straight portions.

The characteristics of the antenna of FIG. 4, provided for a card of dimension 61 mm × 40 mm, makes it possible to obtain, as in the previous case, a resonance frequency close to 13.56 MHz. Indeed, we obtain here an inductance of the resonator LR of 122,113 μH, a capacitor of the resonator C _R of

1, 11 pF and thus a vacuum resonance frequency of 13.653 MHz.

As for the example of Figure 3, the antenna shown in Figure 4 does not require the establishment of a loop bridge between elements of the antenna circuit.

A fourth exemplary implementation of the invention will now be described with reference to FIGS. 5 and 6.

According to this exemplary embodiment, a support 55 carries on a first face represented in FIG. 5 a loop 56 made in the form of a single turn with connection pads 53, 54 at each of its ends for connection with the electronic circuit of FIG. electronic entity considered in this fourth embodiment. On a second face of the support 55, opposite to the first face and represented in FIG. 6, the electronic entity receives a resonator 58 formed of rectilinear portions of conductive tracks which form a spiral (here formed by three turns) with free ends 51, 52. The loop 56 and the resonator 58 are respectively positioned on the first face and the second face of the support 55 so that at least a substantial part of the length of the loop 56 is in line with the resonator 58, preferably in rectilinear portion portions of the resonator 58, for example external portions thereof, or alternatively in median portions thereof (which increases the capacitive coupling phenomenon between the loop 56 and the resonator 58).

Thus, certain portions of the resonator 58 and the loop 56 are separated only by the thickness of the support 55 made of dielectric material and the arrangement just mentioned thus also performs a capacitive coupling between the loop 56 and the resonator 58.

If it is desired to obtain a particularly effective coupling, a support of small thickness, for example less than 0.5 mm, or even less than 0.3 mm, and even less than 0.15 mm, is used.

The operation of the electronic entity using the antenna described in FIGS. 5 and 6 therefore follows the same principles already described for the electronic entity of FIG. 1 with reference to FIG.

Fig. 7 shows an antenna in a fifth embodiment of the invention.

This antenna comprises a resonator 78 formed of a plurality of turns made by means of rectilinear conductive track portions. The conductive track which draws the resonator 78 thus forms a spiral with two free ends 71, 72.

It will be noted here, as is the case in FIG. 7, that the number of turns that form the resonator is not necessarily an integer without this compromising the design or the physical operation of the antenna. This remark also applies to the other embodiments.

The inner coil of the resonator (that is to say the coil which terminates at one end by the free end 72) provides a zone which receives, as clearly visible in FIG. 7, a loop 76 formed by a single turn intended to be connected to an electronic circuit by means of connection pads 73, 74 each located at one end of the turn.

The loop 76 is located at a sufficiently small distance from the inner turn of the resonator 78 (over at least part of their perimeter, and in the example described here over the entire perimeter of the turn forming the loop 76) so that there is a capacitive coupling between the loop 76 and the resonator 78.

The operation of the antenna according to this fifth embodiment therefore follows the same principles as for the previous embodiments which have been explained with reference to FIGS. 1 and 2. FIG. 8 represents an antenna according to a sixth exemplary embodiment of FIG. the invention.

The antenna shown in FIG. 8 comprises a loop 86 which has at each of its ends a connection pad 83, 84.

The antenna also includes a resonator 88 located in the inner surface defined by the coil 86.

The resonator is formed by a conductive track parallel to the loop

86 and located at a short distance therefrom, and extends on either side near the connection pads 83, 84 to two pads 87, 89 situated facing each other, also at a short distance from each other. one of the other and each formed by an enlargement of the width of the conductive track which forms the resonator 88.

The two studs 87, 89 allow the connection of a capacitor whose capacitive behavior is added to the inductive behavior of the conductive track of the resonator which forms approximately one turn. These two combined effects make it possible to obtain the resonator effect. In addition, because of the proximity of the conductive track which forms the resonator 88 with the loop 86 and, on the other hand, the connection spaces 83, 84, there is a capacitive coupling between the loop 86 and the resonator 88.

The sixth exemplary embodiment thus operates according to the same principles as the previously described embodiments. The exemplary embodiment described in FIG. 8 makes it possible to obtain, for a 23.6 mm × 20.4 mm size card, the following electrical characteristics, by associating a capacitance with the 1325 pF resonator: resonator inductance 104.4 nH and thus a frequency of the vacuum resonator: 13.625 MHz. FIG. 9 represents a bank card in which an antenna is implanted according to a seventh exemplary implementation of the invention.

The map schematically represented in FIG. 9 is a map of the ID1 type with dimensions of 85.6 mm × 54 mm. FIG. 9 shows the zones of the card in which it is possible to implant electrical and electronic circuits (including a telecommunication antenna of the microcircuit of the card with the outside) and the zones in which such an implantation is impossible, for example because of mechanical stresses subsequent to the assembly of the different layers of the card (typically by lamination), such as embossings for making inscriptions on the card.

Thus, the map includes in its vertical half shown on the left in FIG. 9 an embossing zone 91 (in which the implantation of the antenna is impossible) of considerable size relative to the whole of this half, and which thus leaves only a narrow zone 92 for the possible implantation of the antenna.

In its vertical half located on the right in FIG. 9, the magnetic strip to be carried by the card defines a corresponding zone 97 on which it is preferable to limit the locations of electrical circuits. This zone corresponding to the magnetic strip 97 leaves, however, on both sides, regions of relatively large dimensions where the implantation of electrical and electronic circuits is possible, namely an elongated region 99 located between the corresponding zone. to the magnetic strip 97 and the right edge of the card and a main zone 95 located between the embossing zone 91 and the zone corresponding to the magnetic strip 97.

It will be noted that a small portion of the main zone 95 can not receive electrical circuit implantation as shown in FIG. 9. However, because of its small size, this zone does not call into question the explanations that follow. . It will also be noted that the main zone 95 includes an implantation zone 90 of the electronic circuit of the card.

When it is desired to obtain a sufficient range for the ID1 card which has just been described, it is impossible to use the narrow zone 92 because it can receive only a limited number of turns. We are therefore forced to implant the antenna in the vertical half

(shown on the right in Figure 9) which does not contain the embossing zone 91, which however involves a division by two of the antenna surface, and therefore according to the conventional design a division by two of the magnetic flux used for telecommunication.

Here, as shown in FIG. 9, it is proposed to implant a loop 96 whose perimeter approximately corresponds to that of the vertical half shown on the left in FIG. 9. The loop 96 thus extends mainly in the main zone 95 and to a lesser extent in the elongated region 99.

The loop 96 comprises a single turn connected at both ends to the electronic circuit of the card by means of connection pads 93, 94 which extend naturally into the implantation zone 90.

It is further proposed to implant a resonator 98 inside the loop 96.

The resonator is formed of rectilinear conductive track portions that form a spiral winding with free ends.

The resonator 98 extends, like the loop 96, mainly over the region of the main regions 95 and the elongate region 99. The resonator 98 is obtained here by spirally winding 0.112 mm-wide wires with a interspiracy width of 0.088 mm.

The resonator 98 thus makes it possible to amplify the signals at the communication frequency of the electronic circuit (here 13.56 MHz), the signals being furthermore exchanged between the resonator 98 and the loop 96 by capacitive coupling between these two elements, as already described for the previous embodiments.

Thus, although the external dimensions of the antenna (namely here the loop 96) are reduced (here to slightly less than half the surface of the ID1 card), a sufficient sensitivity of the antenna, and thus a sufficient range of the card in remote operation. FIG. 10 represents an antenna according to an eighth exemplary embodiment of the invention.

This antenna consists on the one hand of a loop 106 comprising a single turn and connection pads 103, 104 to the electronic circuit of the electronic entity considered here, and on the other hand a resonator 108 formed of the spiral winding of a plurality of turns (here about twenty turns), the two ends of the winding 101, 102 being left free. As described with reference to FIG. 1, the outer turn of the resonator 108 is sufficiently close (precisely furthermore parallel at each point) to the loop 106 to achieve a capacitive coupling between the loop 106 and the resonator 108.

In this embodiment, provision is furthermore made for the presence of a conductive element 109 of small dimensions (such as a conductive track portion) directly linking the resonator 98 and the loop 96. This conductive element 99 may slightly modify the electrical characteristics. circuit (for example to better adapt to the communication frequency of the electronic circuit used), but does not question the principles of operation of the antenna according to the invention as described mainly with reference to Figures 1 and 2.

FIG. 11 represents an antenna for an electronic entity according to a ninth embodiment of the invention.

The antenna represented in FIG. 11 comprises a loop 116 formed, when the electronic entity is assembled, of the winding of two turns: the two turns are formed by conductive tracks deposited in the same plane and intended to be connected to the electronic circuit of the electronic entity by connection pads 113, 114; the looping loop 116 is made in the electronic entity by means of a bridge that allows one turn to stride the other at the contact pads of the bridge 115, 116.

The antenna also comprises a resonator 118 formed of conducting tracks located in the same plane which draws a general shape of spiral with free ends 111, 112.

The outer turn of the resonator 118 is sufficiently close on an essential part of its periphery of at least one of the turns of the loop 116 to generate a capacitive coupling between the loop 116 and the resonator 118, in order to obtain an operation of the antenna shown in Figure 6 according to the same principles as those described with reference to Figures 1 and 2.

In this embodiment, it was desired to use a loop 116 with a plurality of turns (here two turns), which necessitated the use of a bridge. However, thanks to the resonator 118, the number of turns of the loop 116 could be reduced, which makes it possible, for example, to solve problems implantation. This solution is indeed satisfactory especially when the number of turns connected to the electronic circuit (that is to say to the connection pads 113, 114) must be limited, but the surface defined inside these turns can be used. Furthermore, with equal surface area and equal number of turns, the presence of the resonator makes it possible to increase the range of the electronic entity with respect to an electronic entity without such a resonator.

Figures 12 and 13 show an antenna made in a microcircuit card on two layers of this card respectively shown in Figures 12 and 13.

On a first layer 125 of the microcircuit card is deposited a loop 126 adapted to be connected to the electronic circuit of the card by means of connection pads 123, 124, located substantially in the center of the surface of the first layer 125. From of the connection pad 124 extends spirally a first strand

127 of the loop 126, referred to in the following external strand. The outer strand 127 includes a rectilinear portion that extends substantially between the connection pad 124 and an edge of the card and four straight portions that extend over substantially the entire perimeter of the card, a short distance from the edge of the card. it. The second strand 129 of the loop 126 extends spirally from the connection pad 123 into the spiral formed by the outer strand 127.

The second strand 129 is thereby referred to as inner strand.

The outer strand 127 and the inner strand 129 are connected to each other at their opposite ends to the connection pad 123, 124 by a connecting portion 130. The loop 126 is thus able to form, together with the electronic circuit of the map, a closed circuit.

Note that the different spacings between the various conductive track portions forming the loop 126 (that is, the spacing between the two strands) are (taken in pairs) of the same order of magnitude, and substantially equal to two. two in each direction, in order firstly to limit the formation of interspire capacitors and, secondly, to provide a sufficient surface inside the loop 126. On a second layer 131 shown in Figure 13, the microcircuit card carries a resonator 128 formed of the spiral winding of a conductive track with free ends (here formed a little more than two turns).

The first layer 125 and the second layer 131 are close enough that there is a capacitive coupling between the resonator 128 and the loop 126, and in particular its outer strand 127 which is arranged according to the example given here substantially to the right of the turns which form the resonator 128.

An operation of the type described in its principles is thus obtained with reference to FIGS. 1 and 2. FIG. 14 represents an antenna used in an eleventh embodiment of the invention.

This antenna comprises a loop 146 formed of an outer strand 147 and an inner strand 149.

Each strand 147, 149 extends spirally from a connection pad 143, 144 located substantially in the center of the card.

The outer strand 147 is formed by a spiral which extends in particular over almost the entire perimeter of the card (generally more than% of this perimeter, and here more than 7/8 ^th of this perimeter). Thus, in particular, the outer strand 147 extends, seen from the connection pad 143, over more than one turn (that is to say, more than 360 °). In other words, any half-line (imaginary) coming from the connection pad 143 has at least one intersection with the outer strand 147.

The inner strand 149 extends spirally from the connection pad 144 and into the surface defined by the outer strand 147, so that it is interwoven with the outer strand 147. The strand 147 and the inner strand 149 are connected, at their end opposite their respective connection pad 143, 144, by a connecting portion

145 and thus form a flat closed circuit when the electronic circuit is connected to the connection pads 143, 144.

The antenna also comprises a resonator 148 formed by a conductive track with free ends 141, 142 wound in a spiral.

The resonator 148 comprises approximately two turns wrapped around the loop 146, a turn of which is at a short distance from the outer strand 147 of the loop

146 on almost the entire perimeter of the map. The resonator 148 also comprises a second portion electrically connected to the first and wound in spiral inside the loop 146, partly near the outer strand 147 and partly near the inner strand 149, almost to the connection range of the latter.

The proximity of the resonator 148 and the loop 146 over a large part of the length of the loop 146 allows a capacitive coupling between the resonator 148 and the loop 146 and thus an operation as already given in its principles with reference to FIGS. 2.

Figures 15 and 16 show an antenna made within a microcircuit card on two layers of this card respectively shown in Figures 15 and 16.

On a first layer (shown in FIG. 15) is deposited a loop 156 adapted to be connected to the electronic circuit of the card by means of connection pads 153, 154 so as to form, with the electronic circuit of the card, a closed circuit . The first layer also carries a first portion 158 of a resonator made in the form of a winding with free ends, and located here inside the loop 156. The outer turn of this first portion 158 is located a short distance from the loop 156 so as to allow a capacitive coupling between these two elements. The end of the first portion 158 opposite its outer turn ends in a first metal pad 159 forming a frame as described below.

On a second layer shown in Figure 16, the microcircuit card carries a second portion 160 of the resonator, also formed of the spiral winding of a conductive track with free ends. At one of its ends (here its inner end), the second portion 160 ends with a second metal pad 161 forming a frame.

It will be noted in this regard that FIGS. 15 and 16 represent the different windings seen from the same direction, so that the first metal strip 159 is located at the right of the second metal strip 161.

The first layer and the second layer are also sufficiently close so that there is a capacitive coupling between the first portion 158 of the resonator and its second portion 160, particularly at the level of the first and second portions. second metal pads 159, 161 located vis-à-vis and thereby forming a capacitor.

Note that the embodiment described here provides a winding in the opposite direction of the two parts of resonator 158, 160. Alternatively, one could provide the same winding direction for the two parts.

The examples which have just been given naturally represent only possible embodiments of the invention.

The electronic entity may in particular be other than a microcircuit card, such as for example a digital personal assistant or an electronic passport.

Claims

An electronic entity comprising an electronic circuit to which an antenna is connected, characterized in that the antenna comprises a loop electrically connected to the electronic circuit and a resonator formed of a conductive winding with free ends and coupled to said loop.

2. Electronic entity according to claim 1, wherein the resonator is coupled to the loop by capacitive coupling.

3. Electronic entity according to claim 2, wherein the resonator comprises a turn located opposite the loop on at least part of its perimeter.

4. Electronic entity according to claim 3, wherein the turn is located opposite the loop on almost all of its perimeter.

An electronic entity according to claim 3 or 4, wherein the turn and the loop are located at a distance of less than 0.5 mm on said perimeter portion.

6. Electronic entity according to one of claims 1 to 5, wherein the loop forms a conductive circuit connected at each of its ends to a terminal of the electronic circuit.

7. Electronic entity according to one of claims 1 to 6 / wherein said conductive winding comprises a plurality of turns.

8. Electronic entity according to claim 7, wherein the turns are separated in pairs by a distance of less than 0.5 mm.

9. Electronic entity according to one of claims 1 to 8, wherein the loop is located inside the resonator.

10. Electronic entity according to one of claims 1 to 8, wherein the resonator is located inside the loop.

11. Electronic entity according to one of claims 1 to 10, wherein the loop and the resonator are deposited on the same plane support.

12. Electronic entity according to one of claims 1 to 10, wherein the loop is made in a first plane, wherein the resonator is made in a second plane different from the first plane and in which the resonator is located at the right of the loop.

13. Electronic entity according to claim 12, wherein a median coil of the resonator is placed in line with the loop.

14. Electronic entity according to one of claims 1 to 13, wherein the resonance frequency of the resonator alone is greater than a maximum of 10% to a communication frequency of the electronic circuit.

15. Electronic entity according to one of claims 1 to 14, wherein the antenna is a magnetic antenna.

16. Electronic entity according to one of claims 1 to 15, wherein the electronic circuit operates at a communication frequency less than 100 MHz.

An electronic entity according to claim 16, wherein said communication frequency is between 1 MHz and 50 MHz.

An electronic entity according to claim 17, wherein the communication frequency is between 13 MHz and 15 MHz.

The electronic entity of claim 18, wherein the resonance frequency of the resonator alone is between 13.6 MHz and 17 MHz.

20. Electronic entity according to one of claims 1 to 19, having external dimensions less than 100 mm.

The electronic entity of claim 20, wherein the resonator comprises more than ten turns.

22. Electronic entity according to claim 20 or 21, wherein said outer dimensions are less than 30 mm.

23. Electronic entity according to one of claims 1 to 22, characterized in that it is an electronic pocket entity.

24. Electronic entity according to one of claims 1 to 23, characterized in that it is a microcircuit card.

The electronic entity of claim 24, wherein the antenna extends over approximately half of the surface of the card.