Data transaction card having a coil antenna with reduced footprint

Abstract

A data transaction card having a substrate supporting a chip module coupled to opposite ends of a coil antenna wound so as to form a substantially integral number of main loops and having a supplementary loop having an active area that is different from an active area of the main loops. In one embodiment, the data transaction card has a substantially rectangular substrate having major and minor edges, which supports a substantially rectangular coil antenna having a major dimension that is substantially equal to a dimension of the major edge of the substrate. The coil antenna is positioned relative to the substrate so that a footprint of the coil antenna does not overlap an area of the substrate that is reserved for embossing data therein.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, some embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 is schematic representation of a prior art contactless smart card dimension compliant with ISO/IEC 14443;

FIG. 2 is a pictorial representation of a prior art coil antenna for use in the smart card shown in FIG. 1;

FIGS. 3 a, 3b and 3c are pictorial representations of coil antennas wound according to alternative embodiments of the invention;

FIGS. 4 a and 4b are schematic representations of a smart card having a coil antenna according to the invention of reduced dimension that is located so as to avoid fouling embossing areas; and

FIG. 5 is a flow diagram showing how a coil antenna according to the invention is calibrated to a desired tuned frequency during manufacture.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description of some embodiments, identical reference numerals are used in different figures to refer to components that are identical or serve the same or similar function.

FIGS. 3 a and 3b are pictorial representations of coil antennas 11 wound according to alternative embodiments of the invention. Thus, both figures show a chip module 20 mounted on a substrate and coupled to opposite ends of the coil antenna 11, which is wound so as to form a substantially integral number of main loops 21 and having a supplementary loop 22 that is dimensioned so that an overall active area of the coil antenna is different than that of a single main loop.

As shown in FIG. 3a, the supplementary loop 22 is internal to the main loops 21. Alternatively, the supplementary loop 22 may be external to the main loops 21 as shown in FIG. 3b. According to yet another embodiment shown in FIG. 3c, the main loops 21 are of a length that is less than that of the card and the supplementary loop 22 comprises a first part 22a that is internal to the main loops 21 and a second part 22b that is external to the main loops 21.

FIG. 4 a shows schematically a data transaction card 40 (also known in the art as a contactless smart card) according to an embodiment of the invention having a coil antenna 11 of substantially rectangular form that is located so as to avoid intersecting an embossing area 13 that is located in near a lower edge 23 of the data transaction card 20 for containing embossed data 24. Again, it is to be noted that the embossing area 13 actually spans about half the area of the card since it contains not only data 24 near the lower edge of the card, typically relating to the card-holder's name, but also contains embossed data that relates to the card number and expiry date that is situated higher up, typically toward the center of the card.

It is generally required to maximize the area of the main loop without risking fouling with the embossing area or getting too close to the edges of the card. In practice, cards may be mass-produced on a single inlay, and sufficient border must be left between the coil and the periphery of each card in order to cater for the low accuracy associated with the final cutting of the inlay to separate the individual cards.

In accordance with one non-limiting embodiment of the invention, the data transaction card 20 has a substantially rectangular substrate 25 having major and minor edges 26 and 27, respectively. The coil antenna 11 has a long side 28 having a dimension (constituting a major dimension) that is substantially equal to a dimension of the major edge of the substrate. The coil antenna 11 has a short side 29 having a dimension (constituting a minor dimension) that is preferably substantially half a length of the minor edge of the substrate so as to allow the coil antenna 11 to be positioned relative to the substrate 25 so that a footprint of the coil antenna 11 does not overlap the embossing area 13 while maximizing the footprint of the coil antenna. Preferably, the coil antenna 11 is wound around a partial periphery of the substrate 25 so that the long side 28 of the coil antenna is proximate the major edge 26 of the substrate remote from the embossing area 23.

In the embodiment shown in FIG. 4a, the coil 11 is kept clear of the complete area of the substrate containing embossed data, this whole area thus constituting the embossed area 13. FIG. 4b shows an alternative configuration where the embossed area 13 is divided into three embossed areas shown as 13a, 13b and 13c for displaying cardholder name, card number and expiry date, respectively. In such an embodiment, the coil 11 is preferably dimensioned so that its upper edge is proximate the upper edge of the substrate and its lower edge is between the areas 13b and 13c. This results in the coil antenna 11 having a somewhat larger footprint than that shown in FIG. 4a.

The coil antenna 11 is formed in a manner as described above with reference to FIGS. 3a, 3b and 3c of the drawings and connected directly to the IC module 20 without the need for intermediate coupling coils.

FIG. 5 is a flow diagram showing how the coil antenna 11 according to the invention is calibrated to a desired tuned frequency during manufacture. The coil antenna 11 is wound so as to form a substantially integral number of main loops 21. The tuned frequency of the coil antenna 11 is measured and additional complete loops are wound until the measured tuned frequency is less the desired resonance frequency. The last loop is now removed, and one additional loop which is wound to form a supplementary loop 22 as shown in FIGS. 3a, 3b or 3c. The tuned frequency of the coil antenna 11 is then measured, and if the measured frequency deviates from the desired resonance frequency, the dimensions of the supplementary loop 22 are adjusted until the measured frequency equals the desired resonance frequency. In accordance with one embodiment, the substrate 25 is laminated prior to measuring the tuned frequency of the coil antenna 11. This is done since, as noted above, the high temperatures of the lamination process may cause slight shrinkage of the coil, thus de-tuning the coil. It is therefore preferable to check the effect of any adjustments to the dimensions of the supplementary loop after lamination, and to repeat the process by trial and error until a card is produced whose tuned frequency is correct. Once this is done, the dimensions of the coil may be replicated in respect of all further cards, which may be laminated so as to produce data transaction cards that are reliably tuned to the desired frequency.

It will be appreciated that modifications may be made without departing from the scope of the invention as claimed in the appended claims. For example, while the coil antenna has been described as having a rectangular form, it will be appreciated that this is not a requirement and the principles of the invention may be applied to other coil geometries, for example, circular or other shapes.

Claims

1. A data transaction card having a substrate supporting a chip module coupled to opposite ends of a coil antenna wound so as to form a substantially integral number of main loops and having a supplementary loop having an active area that is different from an active area of the main loops.

2. The data transaction card according to claim 1, wherein the supplementary loop is internal to the main loops.

3. The data transaction card according to claim 1, wherein the supplementary loop is external to the main loops.

4. The data transaction card according to claim 1, wherein the supplementary loop is both internal and external to the main loops.

5. The data transaction card according to claim 1, wherein the active area of the supplementary loop is smaller than the active area of the main loop.

6. The data transaction card according to claim 1, wherein the active area of the supplementary loop is larger than the active area of the main loop.

7. The data transaction card according to claim 1, wherein: the substrate is substantially rectangular having major and minor edges, andthe main loops of the coil antenna are substantially rectangular having a major dimension that is substantially equal to a dimension of the major edge of the substrate, and are positioned relative to said substrate so that a footprint of the coil antenna does not overlap an area of the substrate that is reserved for embossing data therein.

8. The data transaction card according to claim 7, wherein the main loops of the coil antenna are wound around a partial periphery of the substrate so that a long side of the coil antenna is proximate the major edge of the substrate.

9. The data transaction card according to claim 7, wherein a minor dimension of the coil antenna is about half the length of the minor edge of the substrate.

10. The data transaction card according to claim 7, wherein the card bears embossed data depicting card number and expiry date and the coil is dimensioned so that an upper edge thereof is proximate an upper edge of the substrate and a lower edge thereof is between the areas of the substrate on which the card number and expiry date are embossed.

11. A method for producing a data transaction card having a substrate supporting a chip module coupled to opposite ends of a coil antenna tuned to a predetermined frequency, the method comprising: winding the coil antenna so as to form a substantially integral number of main loops;winding one of the main loops to form a supplementary loop having an active area that is of different from an active area of the main loops;measuring a tuned frequency of the coil antenna; andif the measured frequency deviates from said predetermined frequency, adjusting the dimensions of the supplementary loop until the measured frequency equals the predetermined frequency.

12. The method according to claim 11, further including laminating the substrate prior to measuring the tuned frequency of the coil antenna and wherein any adjustments to the dimensions of the supplementary loop are made in respect of the effect of the lamination process.