GB2311399A - Universal card interface module for contact free cards - Google Patents

Abstract

A Card and Card Reader each contain a broadly m-shaped antenna consisting of thin conducting layers between plastic laminates wherein the middle branch 18 oscillates in anti-phase with the two outer branches 16 and 17 for proximity coupling applications, whereas all three branches oscillate in phase in distant read/write applications. The prevailingly capacitive positions 15,13,14 of the antenna can be utilised for card readers where it is preferred to draw a card through a slot into the interior of a sensor unit where the card may be tested, processed, or if need be, withdrawn. Capacitive transfer may be also useful in cases where the temporary clipping of the card to a piece of equipment will unite its data base to a digital system.

Description

CARD-READER PROXIMITY COUPLING SYSTEM UTILISING LAMINATED VHF ANTENNA MODULE In the field of personal cards containing a micro-processor, one distinguishes between contact cards wherein the terminal or Reader unit supplies electric power to the card chip by means of delicate contact feelers, and non-contact cards which receive the requisite electrical power by electromagnetic radiation or close proximity inductive transfer. The present paper relates to the latter type.

Also in this field, innovative efforts arose quite early, an example being the British patent GB 1,314,021 (Digital data carrying component and associable data transfer device) wherein it was intended to replace magnetic stripe cards by inductively-coupled card components in automatic fare assessment and collection installations, on railways and buses. Meanwhile, the demand for stored value cards evolved in many other fields as well. One can divide them into three groups, namely (a) those cards which are required to be read, and written on, inside a machine so that the card, if invalid for one reason or another, can be retained. In such cases, the card is inserted through a slot and then drawn mechanically to the transaction location.

(b) cards required in situations where the emphasis is on user convenience and transaction speed; the card remains hand-held and passes the Reader at fairly close proximity (15 150mm).

(c) cards which are in visual line with a Reader position at a distance of 1 - 10 metres, and are required to deliver a signal identifying the card holder to the interrogating station.

At present, no cards are available that could perform well in all of the named cases. While it is feasible for persons to carry several stored value cards, in practice this is an inconvenience and creates confusing accounting problems. It would be desirable to have to handle only one type of card for the various application cases. This would also avoid the need to install different update equipment for each card group.

There are, however, considerable obstacles to the producing of a single type of card capable of satisfying the above listed operation modes.

The aim of the present invention is to point out the principles for a non-contact energy and data transfer system which permits the card to be read at very close distance, at a medium range of proximity (say, 20mm to 150mm), as well as at a distance of several metres; using a card which can be manufactured at a low cost, will not age through frequent usage, will not deteriorate over time and will not generate electronic pollution through radiation.

It is not irrelevant from the economic point of view whether or not these apparently high-staged objectives are achieved or not. If they were shown to be non-achievable, this would mean a very large increase in the production of plastic cards and card Readers of different types. In terms of total cost, this may well exceed the total cost to the economy of minting coins and printing currency notes. This would contrast with the declared pwpose of modern cards to reduce the overheads of value exchanges and trade.

In my preceding patent applications nr. 9605050.4 and 9606764.0 I have set out the design principles of an antenna module built into the card which would permit the use of a single card for the card groups (a) and (b) referred to in the introduction.

To this will now be added a demonstration of suitability of essentially the same antenna module also for card communication with a distant Reader Station. The description that follows is largely a repetition of the material already deposited (as quoted) although there are minor amendments and insertions. This is followed by a new chapter which explains how the card would perform responsive to a gigahertz electromagnetic communication channel.

For most financial transactions it would not be desirable for a Reader Emitter to power up a card at a distance of more than 3 - 4 inches. It would, on the other hand, be desirable that on bringing a card closer to the Reader Plate, there should be a steep rise in the injected power level, reaching its peak at about 2 inches distance. Upon approaching the Card Reader still further the power level should remain constant, or at least, nearly constant.

It is feasible to design a coupling system so that this is achieved, based on the provision that the Antenna is connected to an oscillator whose frequency is lower than the resonance frequency of the Reader Antenna. As the card antenna comes closer to the Reader Plate, the mutual inductance of the antenna pair increases, in such a manner that the joint resonance frequency coincides with the preset frequency of the Reader driving oscillator. This may be set to be the case at a distance of, say, two inches. If the user brings the card still closer to the Reader unit (beyond the critical coupling) the energy transfer would tend to become less efficient; however, the flux interlinkage would increase still further.

In balance, adequate power will be transferred to the Card between zero to 2 inches proximity. - In the absence of a card in its environment the Reader Antenna 'falls asleep', there will be but low radiation from the Reader. This would be further reduced because of a degree of mutual cancellation of the twin coils of the Reader Antenna at non-proximity distances. The Figure 5 of GB 2291725 indicates the basic circuitry in the card when receiving input from the Reader twin radiator elements which operate in antiphase.

In Figure 5 of the named patent, (reproduced on Fig. 7 in this paper) the coupling elements are two capacitor pairs 1800 out of phase; even the voltage parameters which characterise individual data bits occur in the coupling pairs in opposite directions relative to a steady state condition.

Their separate interface sections (32, 33) produce therefrom a single input signal to a circuit group (34) which translates the signal into a high or low data bit, and into a clock pulse, both inputted to a microprocessor (30).

Whereas thus in close proximity (say, between lmm to 60mm), the antiphased signals can be read out separately and become additively effective within the card antenna and connected circuits, at a spacing beyond 100mm the two signal elements intermingle and cancel each other. (The behaviour at VHF frequencies will, however, have to be established experimentally.) In the present paper, the capacitor plates are widened portions of the coil elements. It is envisaged that a coil is made of thin conductor stripes deposited on thin laminate insulating material of which the card is to be made up. The purpose of this arrangement is to avoid the strain on the coil material if it were constituted of solid wires or relatively thick metal deposits.

It is reported that coils of the latter kind when subject to frequent bending, become brittle and develop discontinuities which understandably ruin the resonance effect.

By making the width of the inductive conductor strips fairly wide (see Figure 4), its thickness can be made small enough to avoid any undue strain during the bending of the card. At the same time, however, it is no longer possible to accommodate several turns; a single loop for the left and the right winding must suffice. This circumstance largely determines the frequency at which this configuration can oscillate. - There are interdependent limitations to this project, but within these limitations working conditions could be established.

Descriptions of a feasible mode. The antenna for the Card Reader would consist of two inverted U conductors wherein the two middle legs are combined into one (8, see the equivalent circuit of Fig. 1), the two outer ones being 6 and 7. 3,4 are capacitive loads; 5 is a coupling capacitor connected to a conductor 2, driven by an a.c. generator 1.

The Reader antenna configuration (Fig. 2) is almost a replica of its electrical equivalent circuit of Figure 1. Fig. 2 shows the electrical deposits on the plastic substrate of the Reader Plate.

The strip conductors of the coils (6,8,7) are widened at the bottom (6a,8a,7a) to form capacitive areas conjointly with the grounded strip patches 3 and 4. The patch S is connected to a coaxial link 2 leading to a VHF drive unit (not shown).

As explained in the introduction, the VHF drive unit will operate at a frequency which is below the resonance point of the described antenna configuration. Therefore, the capacitive impedance will prevail and the current flow in the antenna will be small.

Figures 3 and 4 show the equivalent and real conductors for the card component. They are selfexplanatory. In Fig. 3, the item 20 is a load element, usually a microprocessor and/or memory chip.

When a card antenna such as shown in Figure 4 approaches a Reader as shown in Fig. 2, the mutual inductance of the two coil pairs is added to the one which each has for itself. When they are spaced by two inches the added mutual inductance will be sufficient to lower the joint response frequency to the same level as the VHF applied to the Reader unit.

At very close proximity, say when the card is inserted into a slot, the intensity of the flux linkage will be so great that in spite of the too tight coupling factor, the energy transfer will be sufficient to operate the card processor chip 20, even though the card is not inserted over its full length.

Greater stability in the transfer conditions can in certain cases be obtained when the useful load 20 is not connected in parallel to capacitor 15. Serial connection of the load is shown in Fig.

3A.

It is feasible that the power transfer conditions would be improved if, instead of only one laminate in the card, several identical laminates and strip antennas exist in parallel. The connecting point between the load and the several antenna strips 18 may be produced by a soldered through-going rivet. Fig. S shows a preferred version using 4 laminated substrates, ll, 12, 11, 12.. These have conductive deposits (except 11) in the shape of the m-shaped antenna with the capacitive end portions 13, 14 and 15 (Fig.4).

Fig. 5 shows a cross section through the capacitor position, the card thickness d' is enlarged in the d-dimension. The centre conductor 19 serves as a neutral electrode and can be used in place of a ground terminal.

This illustration (of Fig.5) also shows something important: the feasibility of using the card in a shallow capacitive card reader unit (such as shown in Fig.9). The metal layers 21 and 22 are part of a capacitive energy and data transfer arrangement similar to that shown in Fig. 7 except that the proposed module requires one of the two electrodes (say 4a) to be split into two halves (13/13 and 14/4) whereas the other one (4 ) is represented by electrode 15/15.

Fig. 6 shows the equivalent circuit for the double laminate antenna module. The reference numbers are the same as used in the cross section of Fig. 5, the functional correlation is therefore easily established.

Item 24 is a generator of VHF sin waves such as may be produced, for example, by the carrier of a mobile telephone set. The purpose of the card in this context would be the possibility (described in GB ) of connecting the card to a remote bank computer - if the PIN on the keyboard has been entered correctly - to update the card from the holder's own bank or credit account revalue re-loadl. Mobile card update devices could be built, with or without also offering an audio communication link.

In Fig 6, item 23 is a modulator unit controlled by the data input derived from a computer or card processor unit.

From the description, it is clear that this invention relates to a card read/write system which combines the capability of a card readable at very close proximity to the RIW transfer elements with the capability of R/W transfer over a distance of up to 100mm.

In practice, both are expected to be needed in different usage situations, and it is a matter of economy and personal convenience that there is now the possibility of a card becoming available which is equally functional in both cases.

The question shall now be pursued, how would the conductive pattern of Figure 4 behave if the magnetic field changes that passed through the left half and those that pass through the right half were not - as so far described - 180t out of phase, but in phase? It is believed that there will be also a resonance point, or even several such, yet at considerably higher periodicities. The three inductive elements (16, 17 and 18, Figure 10) would oscillate at frequencies which are close to each other if not at exactly the same frequencies. By appropriate adjustment of the L-C factors uniform tuning should be achievable.

It may therefore be possible to excite an oscillation in a card antenna by sending a beam of fast rising pulses from the antenna of a monitoring point towards a card some distance away. The monitoring point would receive the radiation emitted by the card, detect any modulation, and register the digital data contained therein.

The presence of a card when crossing the monitoring beam is detected simply by the occurrence of the selectively received card scatter frequency. A binary "1" is detected by an occurrence of a sudden depression in or disappearance of the received signal. The modulation of the reflected radiation is produced in the card antenna (Fig. 10), by the sequential digital output produced in the card chip L. The output data do (Fig. 13) are applied to the gates of two field effect transistors, as shown. A logic high voltage level makes the transistor conductive thereby loading or short circuiting any differential voltage between points a and c, or respectively between b and c.

As can be seen from Fig. 10, thin wires connect the chip L with correspondingly marked points in the antenna structure.

When the card antenna is excited by a distant radiation source, the card antenna-points a and c develop node points of different electrostatic potential.

On the other hand, when the card is read in close proximity, differences of potential will occur in both a and b. With the occurrence of a binary "1" when scanned by a proximity monitoring point, the amplitude modulation of the induced card radiation will therefore be deeper.

The points a,b,c are also indicated in the electrical equivalent circuit of Fig. 11. Incidentally, the elements marked with the index 25 are intended to indicate the occurrence of capacitive magnitudes in the conductors by an increase of their width, making them behave differently from a simple wire connection. The connection between L and b is shown by an interrupted line in Fig.ll to signify that the bconnection to the chip has no relevance in the case of longdistance card scanning.

It is also possible to enter data into the card by a shorter long-distance source. This is indicated by Fig. 12. As the node points, a or b acquires a potential difference against point c, the dc output across the terminals d and e becomes larger than zero provided diodes 26 with a low forward voltage drop are employed. These rapidly pulsed d c voltages can be used in a voltage multiplier section of the chip L for providing an operating power, as well as for detecting data in them.

Two-way communication between card and a monitoring post should be readily realisable where a spatially well-defined beam working over relatively short distances is involved.

The inventive importance of the m-shaped card antenna is that it can be electro-magnetically coupled to a similar antenna in the Reader Unit, the radiation of which is so constituted that it can have an effect only at short distances. Beyond a distance of about 4 inches perpendicular to the centre axis of the antenna, hardly any radiation is expected to be seen. And even sideways, the radiation vectors would be abnormally reduced. It is therefore the sort of Card Station which will not disturb neighbouring equipment or communication channels.

Another aspect of the described card antenna's versatility is that it can be purely capacitively coupled in very close proximity to other equipment. It would only be needed to clip the card to a surface of another piece of equipment where the plates 3, 5 and 4 (Fig.2) are mounted in congruence with similar plates in the card. Not only can simple shallow-height Readers be made such as shown in Figures 5, 6 and 9. A card might be clipped to the rear of a mobile telephone or inserted into a shallow slot therein, enabling it to transfer purchase power to another subscriber, or to connect to the card owner's bank account in order to request a card update, a display of a status report, or any other detail of his or her portfolio.

The mobile phone keyboard would in this connection be used for entering the secret PIN into the card, for comparison with a pre-recorded PIN held in the card. Only if the comparison is successful will the card's own data be accessible to the outside world.

Apart from providing facilities on a mobile phone for integrating a (clipped-on or inserted) stored value card of the described type with the data transmission/reception capability of said mobile phone, it is also possible to build self comwned financial mobile communication devices which can be coupled to a card according to the present invention by close proximity, and which have a keyboard, a display window and a VHF antenna, the former for calling forth any desired data from the card memory, and to display them; the latter, for selective calling up one of the computer stations for updating one of the card accounts, in accordance with agreed protocols.

There are also useful practical application forms for the medium-range proximity (10 to 100mm) version of the card. In automatic fare collection, the normal use of the card would be that it is and remains handheld during the duration of the transaction cycles. This is no problem since the duration is in most cases measured in milliseconds.

However, with the rising tide of tourism, many travellers carry also luggage; housewives carry shopping bags - sometimes two or three. Taking out a card and retrieving it from a wallet takes time; meanwhile, other passengers have to wait behind the tourist.

Some suppliers of contactless cards offer a solution in that the traveller may keep the card in the wallet, which may even be left in the person's coat or shirt pocket. This is based on the Reader antenna's radiation having a much larger working radius. While this may be satisfactory in most cases, the danger of involuntary transaction exists (for example, where there are several rows of turnstiles, one of the persons passing through may carry a sheet of metal or a tool box.

Reflection therefrom may reinforce the level of a freak reception by the wrong card; the person affected may have to pay a major fare or find the card invalidated by reason of an incomplete response to a protocol.

It is therefore held that involuntary transactions should be avoided as a matter of principle; a deliberate action on the part of the traveller should always be required. That means that the card must be brought into the relatively close range within which a transaction can take place, and beyond which there is no radiation at all.

This can be achieved with the antenna module according to this invention, but it remains undesirable for housewives or tourists to search for a card as mentioned above. It would be possible, however, to provide shopping bags 40 with a small internal pocket (see Figure 14) into which the fare card can be placed. Outwardly, the exact location of the farecard may be marked. By lifting the shopping bag and touching the Reader area therewith, the required transaction at an entry or exit tumstile would be performed, the turnstile unlocks and the passenger moves on.

A similar situation can be produced for the tourist carrying a heavy suitcase, 43 (Fig. 14, lower figure). By standardising the height at which the read/write elements are built into the tumstile, it is possible to attach a pocket, 42, inside the suitcase wall in such a manner that, by rolling the suitcase through the tumstile, the optimum interface between Card and Reader is established.

Again, all delay is avoided.

Claims (12)

1. WHAT I CLAIM IS: 1. An embedded antenna module for a non-contact integrated circuit card which comprises two coils or coil loops driven in counter-phase by the electromagnetic flux emanating from a card reader unit when brought into spatial vicinity and which antenna module consists of conductive deposits on laminates which are one of the physical constituents of said IC card.
2. 2. An embedded antenna module for noncontact IC cards as in Claim 1 wherein adjacent winding portions of the said two coils are combined into a single winding portion (8).
3. 3. An embedded antenna module for non-contact IC cards as in Claims 1 or 2 wherein the card consists of more than one laminate sheet and whereof several or all of the laminate sheets have identical patterns of conductive deposits.
4. 4. An embedded antenna module for non-contact IC cards as in Claims 1 to 3 wherein the integrated data processor chip is connected to the antenna module at that point of the middle branch (8) where its average load resistance is best matched to the antenna impedance at the operating frequency.
5. 5. An embedded antenna module as in any of the preceding claims which has m-shape and the lower tips of which are widened to form a part of capacitive elements (13,14,15) opposite a common ground plane (19).
6. 6. An embedded antenna module in the Reader of a card transaction device which is equal or similar to that characterised in claims 1 to 5 except that the middle branch (18) is connected to a . feed line leading to the data- and sensor electronics of the said card transaction station.
7. 7. A non-contact IC card system comprising a portable data carrier and a transaction station for reading data from said carrier or card, and for entering new data therein, characterized by the frequency of the carrier wave emitted by said station being not tuned to the antenna nodule in the card, nor to the antenna module of the station, but to the combined antennas when the card isat a specified optimal spacing from the station.
8. 8. A non-contact I C card system as in Claims 1, 6 and 7 w h e r e i n the antenna module comprises portions which are prevailingly inductive and other portions which are prevailingly capacitive, and that the de signer of a particular data interchange station for the bidirectioiial transfer of data between card and station reader has the option of uti lizing either the spatial electro-magnetic field, or the electrostatic field derived from the said capacitive portions of the card antenna for designing the read/write configuration of the Reader Station.
9. 9. A non-contact IC card system for the optional embodiment of inductive or capacitive data transfer sensors as in Claim 8, w h e r e i n the embedded antenna module can also be utilized, without any switching ac tion, for the sending and receiving of data by radiation, based on an ability of the said antenna module to develop in the three conductor stems (6,8,7, Fig. 1) also an 'in-phase' resonance responsive to homoyenous field changes passing through it.
10. 10. A shopping bag, a suitcase, a piece of clothing, furnished. with a fastened on card pocket to contain the card safely and to assist the owner of the card in presenting it in proximity to a Card Reader without danger of losing the card while carrying said other items through an access control or payment station.
11. 11. A Card pocket as referred to in Claim 10 which is detachable from the shopping bag, suitace, or piece of clothing.
12. 12.A non-contact card system including features as described in the afore-going description and in the accompaning drawings.