Chip card, antenna carrier for a chip card and method for producing an antenna carrier for a chip card

Abstract

The present invention relates to a chip card designed to communicate data with a card reader operating at a read frequency in a contactless mode. The resonant frequency of the chip card can be changed according to the chip capacitance used in the contactless mode of the chip card. In order to be able to use various chips without changing the gain antenna design, a capacitive element is provided in the card antenna circuit so that the chip card including the card antenna circuit and the chip module has two different resonant frequencies, one of which is equal to or lower than the read frequency and the other is equal to or greater than the read frequency. This establishes a wide band in which the read frequency falls.

Description

[0001] The present invention relates to the field of chip cards, which are also called smart cards. Chip cards are well known to the public and have multiple uses: payment cards, transportation cards, identity cards, etc.

[0002] Chip cards include transmission means for transferring data from an electronic chip (integrated circuit) to a card reader device (reading) or from the device to the card (writing). These transmission means can be "contact", "contactless" or "dual interface" when they combine the two methods mentioned above.

[0003] like Figure 1 As shown, the chip card 1 generally comprises a rigid card body 2 made of a material of the PVC, PVC / ABS, PET or polycarbonate type, which forms the bulk of the card incorporating an electronic module 3. The electronic module 3 generally comprises a flexible printed circuit equipped with an electronic chip. In chip cards and dual interface cards with contacts, the electronic module comprises contact pads electrically connected to the chip pads. On the surface of the card body, the contact pads are flush with the electronic module so as to be connected by electrical contact with a card reader device. Contactless chip cards and dual interface chip cards also comprise at least one antenna for transmitting data between the chip and a radio frequency system, thereby allowing data to be read or written contactlessly.

[0004] Some contactless chip cards and dual-interface chip cards have an antenna in the card body that is directly electrically connected to the electronic module. Other contactless chip cards and dual-interface chip cards have an antenna inserted into the card body layer that is inductively coupled to a coupling coil located in the electronic module. In such cards, the antenna inserted into the card body is called a "booster antenna".

[0005] The present invention relates to contactless chip cards and dual-interface chip cards with booster antennas. In such cards, the electronic module comprises a module antenna and is housed in a cavity (e.g. a cavity cut or milled in a card body layer) for efficient inductive coupling to a coupling coil located in the card body. An example of an electronic module with a coupling coil is described, for example, in patent document FR2994005B1.

[0006] When designing a chip card with a booster antenna, one of the technical problems encountered is to obtain a resonant frequency of the booster antenna that is within the frequency range specified by the data communication standard between the chip of the electronic module and the contactless reader. For example, the resonant frequency should be between 13 MHz and 15 MHz.

[0007] The resonant frequency of the card antenna circuit depends on parameters such as the impedance of the chip and the impedance of the various antennas or antenna components (module antenna, coupling coil and booster antenna). For example, the chip can have a capacitance in the range of 40 picofarads to 100 picofarads. Replacing the chip usually causes a shift in the resonant frequency, which may result in an inefficient coupling of the card antenna circuit with the card reader. Therefore, when replacing the chip, the card antenna circuit usually needs to be debugged and redesigned. In order to meet interoperability requirements and be able to use various chips without changing the design of the card antenna circuit, it is appropriate to have a resonant frequency within a relatively wide frequency band.

[0008] Furthermore, designing a chip card with a booster antenna should address other challenges related to the card size, the location of the electronic module as specified by the standard, the area of ​​the card that must be left free due to possible embossing of the card body, etc.

[0009] The present invention is directed to at least partially improving a chip card with a booster antenna and proposes a chip card according to claim 1 .

[0010] Thanks to the invention, the bandwidth of the frequency response of the card antenna circuit is widened and includes the reading frequency of the card reader in this bandwidth. Moreover, when the chip module is placed in its cavity, the bandwidth of the frequency response of the card antenna circuit does not completely shift out of the reading frequency range. In fact, due to the capacitive element of the card antenna circuit, the sensitivity of the frequency response of the card antenna circuit to the chip capacitance value is reduced.

[0011] The chip card may have one or more of the features specified in claims 2 to 17 , considered alone or in combination with one or more other features.

[0012] The invention also relates to an antenna support for a chip card according to claim 18 and to a process according to claims 19 to 21 .

[0013] Other features and advantages of the present invention will become apparent through reading the following detailed description and the accompanying drawings. In these drawings:

[0014] - Figure 1 A perspective view schematically showing an embodiment of a chip card according to the invention;

[0015] - Figure 2 Schematically represented in perspective and exploded view Figure 1 The embodiment of the chip card shown;

[0016] - Figure 3 Schematically indicates that you can insert Figure 1 and Figure 2 An embodiment of an antenna support between chip card layers shown in;

[0017] - Figure 4 yes Figure 3 an enlarged view of the capacitive element region of the antenna support shown;

[0018] - Figure 5 yes Figure 3 An enlarged cross-sectional view of the capacitor element region of the antenna support shown;

[0019] - Figure 6 and Figure 7 Respectively represent two different chips, according to the corresponding Figures 3 to 5 A frequency response waveform of a chip card of an embodiment;

[0020] - Figure 8 Schematically indicates that you can insert Figure 1 and Figure 2 Another embodiment of an antenna support between chip card layers shown in;

[0021] - Fig. 9 Schematically Figure 8 The directions of the currents flowing in the booster antenna, the coupling coil and the capacitive element, respectively, in the embodiment of the antenna support shown;

[0022] - Fig.10 and Fig.11 Respectively represent two different chips, according to the corresponding Figures 3 to 5 A frequency response waveform of a chip card of an embodiment;

[0023] In this document, the terms "front", "rear", "above", "below", "upper", "lower" and the like are merely conventional and, where appropriate, refer to the orientation as shown in the accompanying drawings.

[0024] Figure 1 and Figure 2 A first exemplary embodiment of a chip card 1 according to the invention is shown. The chip card 1 comprises a card body 2 and an electronic module 3. It should be noted that one or more layers / sheets besides those represented may be laminated above and / or below its main faces.

[0025] The electronic module 3 is, for example, of the banking type and corresponds to the ISO 7816 standard. The electronic module 3 is housed in a cavity 4 made in the card body 2 (see Figure 2 ). The cavity 4 can be milled from one of the main faces of the card body 2 after one of the main faces of the card body 2 has been made by laminating several plastic material sheets 5, 6, 7. Alternatively, the cavity 4 is cut out of the plastic material sheet 5 before laminating it with other plastic material sheets 6, 7 to form the card body 2.

[0026] The electronic module 3 is manufactured according to the prior art (see for example patent document FR2994005A1). For example, the chip installed in the module has a capacitance ranging from 40 pF to 100 pF. For example, as shown below, tests were performed using chips with a capacitance of 69 pF and 78 pF, respectively.

[0027] Figure 1 and Figure 2 The card shown in is of the dual interface type. The electronic chip of the module 3 is connected to both the contact pads 8 on the front of the module 3, which is flush with the surface of the card 1, and the module antenna (not shown, but located on the back of the module 3 opposite the front or contact surface of the module 3). It can be operated in "contact" mode or in "contactless" mode. The chip module 3 may include six or eight contact pads 8.

[0028] Figure 1 and Figure 2 The card shown comprises at least one bottom layer 7, an intermediate layer 6 forming an antenna support or antenna inlay, and a top layer 5. As already mentioned, each of these three layers 5, 6, 7 may consist of several sub-layers (for example, the top layer 5 and the bottom layer 7 may comprise a finishing layer, a printing layer, etc.).

[0029] For example, the top sheet 5 and the bottom sheet 7 consist of one or more layers of PVC. The antenna support 6 consists of one or more layers, wherein a booster antenna 9 is incorporated on or between the one or more layers, the booster antenna 9 comprising a wire coil having at least one winding turn. Alternatively, the booster antenna 9 may comprise a coil made of a conductive trace etched in a metal layer and forming at least one winding turn. The booster antenna 9 occupies most of the area of ​​the antenna support 6. The one or more winding turns of the booster antenna 9 may have a substantially rectangular shape with sides close to the edge 11 of the chip card. For example, one or more of the different component layers of the antenna support 6 are also made of a PVC sheet with a thickness of 210 to 240 microns.

[0030] The coupler coil 10 is also supported by the antenna support 6. The coupler coil 10 is advantageously made at the same time as the booster antenna 9 and using the same technique (eg wire embedding or electrochemical etching).

[0031] Figure 3 A specific embodiment of an antenna support 6 according to the invention is shown. It comprises a substrate having two main surfaces. Figure 3The view is taken from above one of the main surfaces of the antenna support 6. The antenna support 6 is made of PVC. It has a substantially rectangular shape corresponding to the ISO / IEC 7810 ID-1 specification. The booster antenna 9 and the coupling coil 10 comprise a single conductive material (e.g. copper or aluminum alloy with a diameter of 80 to 112 microns) embedded in the antenna support 6 according to methods well known to those skilled in the art (see, for example, patent document EP0753180A1).

[0032] The booster antenna 9 comprises about six turns between a first end 12 and a second end 13. For example, the booster antenna wire starts from the first end 12 and extends along a substantially rectangular shape having two long sides substantially parallel to the longest sides of the antenna support 6 and two short sides substantially parallel to the shortest sides of the antenna support 6. The rectangular shape covers about the upper two thirds of the width of the antenna support 6 and almost the entire length of the antenna support 6, so as to leave one third of the surface of the antenna support 6 free at the bottom of the antenna support 6 for relief that may need to be made. The first turn starting from the first end 12 corresponds to an inner turn (i.e. wound inside the other turns).

[0033] The coupling coil 10 comprises approximately six turns of winding between a third end 14 and a fourth end 15, the third end 14 being connected to the first end 12 of the gain antenna 9. The number of turns of the coupling coil 10 can vary, for example, depending on the type of chip module 3. The number of turns can vary, for example, from four turns to eight turns. For example, for a chip module 3 with eight contact pads (also called an 8-pin module), the number of turns can be six. For a chip module 3 with six contact pads (also called a 6-pin module), the number of turns can be more.

[0034] The coupling coil 10 has a substantially square shape, the four sides of which surround an area corresponding to the cavity of the electronic module 3. The coupling coil 10 is wound counterclockwise from the fourth end 15 to the third end 14. The first turn winding starting from the fourth end 15 corresponds to the inner turn winding (i.e., wound inwardly relative to the other turn windings).

[0035] The capacitor element 16 includes a substrate 17 made of a dielectric material (see Figure 5 ) and a conductive layer 18 on the substrate 17. For example, the substrate 17 is made of epoxy glass, PET or PVC. The thickness of the substrate 17 ranges from 50 microns to 120 microns. For example, the conductive layer 18 is made of copper alloy, aluminum alloy, silver paste or carbon nanoparticles. The thickness of the conductive layer 18 ranges from 5 microns to 50 microns, preferably 30 microns.

[0036] The capacitive element 16 includes two regions 19, 20 electrically isolated from each other. Each of the regions 19 or 20 includes a conductive sheet 21 or conductive sheet 22 and a series of fingers 23 (e.g., a series of 20 fingers). For example, each finger is 10 mm long and 250 μm wide. The fingers of each region are spaced 50 μm to 150 μm apart (see FIG. Figure 5 ). The fingers of the two zones are interdigitated in a finger-like manner. In other words, the fingers of each of the two zones are arranged head-to-foot opposite to the fingers of the other zone. The fingers of one zone have borders on both sides and are longitudinally adjacent to the fingers of the other zone, and the gap width between the fingers is 50 microns to 150 microns. The longer the fingers, the higher the capacitance value. The more fingers, the higher the capacitance value.

[0037] The capacitive element 16 is attached to the antenna support 6. For example, the capacitive element 16 is glued to the antenna support 6 or laminated with the antenna support 6. The advantage of this solution is that for various chips and various applications, the gain antenna 9 and the coupling coil 10 can have the same parameters (wire diameter, number of turns, etc.) when manufacturing the antenna support 6, and the capacitive element 16 may be the only component that can be designed and adapted (number of fingers, length, width, thickness, etc., and the gap between the fingers) in order to optimize the coupling between a specific chip module 3 and a card reader and / or meet specific specifications.

[0038] The second end 13 of the booster antenna 9 is electrically connected to a conductive sheet 22 of the capacitor element 16, and the fourth end 15 of the coupling coil is electrically connected to another conductive sheet 21 of the capacitor element 16. The electrical connection between the wire ends 13, 15 and the conductive sheets 21, 22 of the capacitor element 16 is achieved by, for example, thermal compression or ultrasonic bonding.

[0039] Figure 6 and Figure 7 The graphs show the relationship between the signal amplitude and the frequency measured in the reflection mode (S11) for two different chips, respectively Infineon SLE78- and NXPP60. These curves show two short dips contained in a relatively large bandwidth. More specifically, Figure 6 The curve of shows two short dips at 12.7MHz and 15.0MHz respectively. The bandwidth between these two short dips is about 2.3MHz. Figure 6 The measured chip capacitance is 78 pF. Figure 7 The curve of shows two short dips at 12.7 MHz and 15.6 MHz respectively. The bandwidth between these two short dips is about 2.9 MHz. Figure 7 The measured chip capacitance is 60 pF.

[0040] The card reader has a reading frequency of about 13.5 MHz. It can be seen that this reading frequency is approximately in the middle of the bandwidths obtained for the two different values ​​of chip capacitance. This proves that Figure 3 The interoperability of the antenna circuit shown in . In addition, the broadband response allows the reader to detect and read even when the card frequency is detuned.

[0041] Figure 8 Another specific embodiment of the antenna support 6 according to the present invention is shown. It comprises a substrate having two main surfaces. Figure 8 The view is taken from above one of the main faces of the antenna support 6. The antenna support 6 may be similar to the antenna support already described in connection with the previous embodiment and its description will not be repeated for the sake of brevity.

[0042] The booster antenna 9 comprises about five turns of winding between a first end 24 and a second end 25. For example, the wire starts from the second end 25 and extends along a substantially rectangular shape ( Figure 8 The rectangular shape covers about the upper two thirds of the width of the antenna support 6 and almost the entire length of the antenna support 6, so as to leave one third of the surface of the antenna support 6 free at the bottom of the antenna support 6 for possible relief printing. The first winding starting from the second end 25 corresponds to the outer winding (i.e. wound outside the other windings).

[0043] The coupling coil 10 comprises about eight to nine turns of winding (and more generally, four to eight turns of winding, depending on, for example, the type of chip module - 6 or 8 pins, as explained above) between a third end 26 and a fourth end 27, the third end 26 being connected to the first end 24 of the booster antenna 9. The coupling coil 10 has a substantially square shape with four sides surrounding an area corresponding to the cavity of the electronic module 3. The coupling coil 10 is wound clockwise from the third end 26 to the fourth end 27. The first turn of winding starting from the third end 26 corresponds to the outer turn winding (i.e. wound outwardly relative to the other turns of winding).

[0044] Capacitive element 16 includes two wire ends 28, 29 as part of a wire, and gain antenna 9 and coupling coil 10 are made of this wire. The wire end 28 extends beyond the second end 25 from the gain antenna 9, and the other wire end 29 extends beyond the fourth end 27 from the coupling coil 10. The two wire ends 28, 29 are interlaced but not connected in the area of ​​​​capacitive element 16. They are arranged so that one wire end starts near the free end of the other wire end. Parallel folding parts are formed between the two wire ends 28, 29, wherein they are substantially parallel to each other. There are two folding parts that extend substantially between the two shortest sides of the gain antenna. Their length is approximately 74 mm to 78 mm. There are two folding parts that extend substantially between the shortest sides of the coupling coil and the gain antenna. Their length is approximately 58 mm. Each folding part has two sides spaced approximately 260 microns apart.

[0045] The second end 25 of the booster antenna 9 is electrically connected to a wire end 28 of the capacitive element 16 , and the fourth end 27 of the coupling coil 10 is electrically connected to the other wire end 29 of the capacitive element 16 .

[0046] like Fig. 9 As shown, the windings of the booster antenna are wound in the same direction (e.g., counterclockwise). The windings of the coupling coil are also wound in the same direction but in the opposite direction compared to the booster antenna (e.g., clockwise). In the capacitor element, the ends of the wires are routed in the same direction.

[0047] Fig.10 and Fig.11 The relationship between the signal amplitude and the frequency measured in the reflection mode (S11) is shown for two different chips (Infineon SLE78 and NXPP60 respectively).

[0048] These curves show two short dips contained within a relatively large bandwidth. More specifically, Fig.10 The curve of shows two short dips at 12.5MHz and 15.4MHz respectively. The bandwidth between these two short dips is about 2.9MHz. Fig.10 The measured chip capacitance is 78 pF. Fig.11 The curve of shows two short dips at 12.7 MHz and 15.7 MHz respectively. The bandwidth between these two short dips is about 3.0 MHz. Fig.11 The measured chip capacitance is 60 pF.

[0049] The card reader has a reading frequency of about 13.5 MHz. It can be seen that this reading frequency is approximately in the middle of the bandwidths obtained for the two different values ​​of chip capacitance. This proves that Figure 8The interoperability of the antenna circuit shown in . In addition, the broadband response allows the reader to detect and read even when the card frequency is detuned.

[0050] An advantage of this embodiment is that the booster antenna 9, the coupling coil 10 and the capacitive element 16 can be manufactured in one continuous step by wire embedding.

Claims

1. A chip card, the chip card being designed for data communication in contactless mode with a card reader operating at a reading frequency of about 13.5 MHz, the chip card (1) comprising: - a card body (2); a chip module (3) having a chip and a module antenna, the chip module (3) being accommodated in a cavity (4) made in the card body (2), - a card antenna, the card antenna comprising a booster antenna (9) located on an antenna support (6) integrated in the card body (2), and a coupling coil (10) connected in series with the booster antenna (9), the coupling coil (10) being inductively coupled to the module antenna, - a capacitive element (16) connected to the card antenna, wherein the assembly including the capacitive element (16) and the card antenna is arranged to have a first resonant frequency, The chip card (1) comprising the card antenna, the capacitive element (16) and the chip module (3) is configured to have a second resonant frequency and a third resonant frequency, the second resonant frequency is lower than the reading frequency, the third resonant frequency is greater than the reading frequency, and the bandwidth between the second resonant frequency and the third resonant frequency is equal to or greater than 2 MHz. 2 . The chip card according to claim 1 , wherein the second resonance frequency and the third resonance frequency are lower than the first resonance frequency. 3 . The chip card as claimed in claim 1 , wherein the capacitive element ( 16 ) has a capacitance value between 10 picofarads and 30 picofarads.

4. A chip card according to any one of the preceding claims, wherein the booster antenna (9) is located on an antenna support (6) comprising two main surfaces, the booster antenna (9) comprising at least one turn of a conductive winding arranged on at least one main surface of the support and extending between a first end (12) and a second end (13), the coupling coil (10) comprising at least one turn of a conductive winding arranged on at least one main surface of the support and extending between a third end (14) and a fourth end (15), the third end (14) being connected to the first end (12) of the booster antenna, the capacitive element comprising at least one first finger-shaped portion and at least one second finger-shaped portion, the first finger-shaped portion and the second finger-shaped portion being interlaced with each other and extending side by side with each other, and the second end of the booster antenna and the fourth end (15) of the coupling coil (10) being respectively connected to one of the first finger-shaped portion and the second finger-shaped portion.

5. A chip card according to claim 4, wherein the capacitive element (16) comprises two areas (19, 20) made of conductive material, the two areas (19, 20) being electrically isolated from each other, and on the one hand, each of the two areas (19 or 20) comprises a conductive sheet (21 or 22) connected to the second end (13) or the fourth end (15), and on the other hand, each of the two areas (19 or 20) comprises one of the first finger portion and the second finger portion.

6. The chip card as claimed in claim 5, wherein at least one of the two regions (19, 20) comprises a plurality of fingers.

7. The chip card according to claim 5 or 6, wherein the two regions (19, 20) comprise a plurality of fingers which are interlaced with one another in the form of fingers.

8. A chip card according to any one of claims 5 to 7, wherein the capacitive element (16) comprises a substrate (17) made of a dielectric material and a conductive layer (18) located on the substrate (17), and the two areas (19, 20) made of a conductive material are present in the conductive layer (18) and the substrate (17) located on the antenna support (6).

9. The chip card as claimed in claim 8, wherein the two regions (19, 20) of electrically conductive material are etched into the electrically conductive layer (18).

10. A chip card according to any of the preceding claims, wherein the booster antenna (9) and the coupling coil (10) are formed by wires embedded in the antenna support (6), and the capacitive element (16) comprises two conductive material areas (19, 20) etched in a conductive layer (18).

11. The chip card according to any one of claims 1 to 4, wherein the booster antenna (9), the coupling coil (10) and the capacitive element (16) are formed by conductive lines embedded in the antenna carrier (6).

12. The chip card as claimed in claim 11, wherein the capacitive element (16) comprises two free ends.

13. The chip card according to claim 11 or 12, wherein one end of the capacitive element (16) is connected to the inner winding of the coupling coil, the other end is connected to the outer winding of the booster antenna, and the other two ends are not connected.

14. The chip card according to any of the preceding claims, wherein the booster antenna (9) forms an outer coil and the capacitive element (16) and the coupling coil (10) are both located inside the outer coil.

15. A chip card according to any one of the preceding claims, wherein the booster antenna (9) is substantially rectangular in shape having upper parallel long sides and lower parallel long sides and two lateral parallel short sides, the coupling coil (10) is located inside the booster antenna (9), the coupling coil (10) has upper and lower sides substantially parallel to the upper parallel long sides and the lower parallel long sides of the booster antenna (9), and the capacitive element (16) is arranged in a region extending inside the booster antenna (9) to below the upper parallel long sides of the booster antenna (9) and a line, the line being parallel to the lower side of the coupling coil (10) and being on the same horizontal plane as the lower side.

16. A chip card according to claim 1, wherein the booster antenna (9) is basically rectangular in shape with two parallel long sides and two parallel short sides, and the capacitive element includes finger-like portions that are interlaced with each other, and the finger-like portions extend in a direction basically parallel to the long sides of the booster antenna (9).

17. A process for producing a chip card according to any one of the preceding claims, wherein - the chip card is designed for data communication in contactless mode with a card reader operating at a reading frequency of approximately 13.5 MHz, - providing an antenna support (6), - a booster antenna (9) and a coupling coil (10) are formed on a main surface of the antenna support (6), the booster antenna (9) comprising at least one turn of a conductive winding extending between a first end (12) and a second end (13), the coupling coil comprising at least one turn of a conductive winding extending between a third end (14) and a fourth end (15), the third end (14) being connected to the first end (12) of the booster antenna (9), - a capacitive element (16) connected to the booster antenna (9) and the coupling coil (10), the capacitive element (16) comprising at least one first finger-shaped portion and at least one second finger-shaped portion, the first finger-shaped portion and the second finger-shaped portion being interlaced with each other and extending side by side with each other in a finger-shaped manner, the second end (13) of the booster antenna (9) and the fourth end (15) of the coupling coil (10) being connected to one of the first finger-shaped portion and the second finger-shaped portion, respectively; -The boost antenna (9), the coupling coil (10), the capacitive element (16) and the chip module (3) are configured to obtain a second resonant frequency and a third resonant frequency, wherein the second resonant frequency is lower than the reading frequency, and the third resonant frequency is greater than the reading frequency, and the bandwidth between the second resonant frequency and the third resonant frequency is equal to or greater than 2 MHz.

18. Process according to claim 17, wherein the booster antenna (9), the coupling coil (10) and the capacitive element (16) are constituted by a single continuous wire embedded in the antenna support (6).

19. A process according to claim 17, wherein the booster antenna (9) and the coupling coil (10) are constituted by a continuous wire embedded in the antenna support (6), and the capacitive element (16) comprises a substrate (17) made of a dielectric material, on which a conductive layer (18) is located, in which the finger-shaped portions are etched.

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