WO2022223912A1 - Near-field communication antenna relay - Google Patents

Abstract

The invention relates to a near-field communication antenna relay (1) comprising a primary antenna (10) for communicating with a near-field reader, at least one control circuit (50) connected to the primary antenna (10), and at least two secondary antennas (20) connected to the primary antenna (10) via multiplexers (30, 40). The control circuit (50) generates a supply voltage (VCC) and communicates with the reader so as to order the multiplexers (30, 40) to select the secondary antenna (20) to be linked to the primary antenna (10). Figure for the abstract: Fig. 1

Description

Description

Title of Invention: Near Field Communication Antenna Relay

[0001] Technical Area

The present invention relates to a near-field communication antenna relay. More particularly, the invention relates to a relay which makes it possible to transform the antenna of a reader in the near field into a plurality of communication antennas in the near field.

[0003] Technological Background

[0004] Patent application WO 2021/038167 describes a device for locating objects on a plate which uses near field communication better known by the acronym NFC (Near Field Communication). The principle implemented consists of arranging a plurality of NFC antennas in a tray intended to receive objects provided with an electronic tag. The tray includes one or more NFC readers connected to the antennas in order to communicate with the electronic tags of the objects placed on the tray. A successive selection of each antenna is carried out to interrogate the tags located in the field of the selected antenna. Depending on the responses of the tags obtained for each antenna, it is possible to determine the position of each tag on the plate. Such a locator tray can be used as a display or store shelf to allow accurate product inventory without moving. Also, it is possible to use such boards as a game board to locate figurines. However, the use as a game board is currently hampered by the cost of such a board. Indeed, the total cost of the board includes a power supply for the electronics comprising one or more NFC readers and one or more interfaces to interact with the players or a player's computer.

[0005] Furthermore, in terms of games, it is also known to use a smart phone of the smartphone type to interact with a board game. US patent application 2019/0370621 describes a game board in which intelligence is deported. Such a game board corresponds to an antenna relay which comprises an array of selectable secondary antennas and a primary antenna intended to communicate with an NFC reader, for example the NFC reader of a smartphone. Thus, it is possible to download an application to the telephone to use it together with the game board with the intelligence of the board remote in the smartphone. Nevertheless, the game board cost described in this application is still quite high because the board still includes a power supply for the antenna selection electronics and several interfaces for interacting with the smartphone.

[0006] Summary of the Invention

The invention proposes a near-field communication antenna relay which makes it possible to transform a simple near-field communication reader into a reader having a plurality of antennas at low cost. Thus, a near-field communication reader can be transformed into a reader controlling a tracking platform having a plurality of antennas using a suitable program. The antenna relay proposed by the invention makes it possible in particular to provide a game board which can be coupled to a smart phone which has a near-field reader function by downloading an application into the phone and simply placing it ci on the game board. The board is simplified to the maximum and the power supply of the board is supplied by the telephone. However, the invention is not limited to game boards but can be used to transform any type of near-field reader into a reader with several individually selectable antennas.

More particularly, the invention provides a near-field communication antenna relay comprising a primary antenna, at least one control and energy recovery circuit, at least one first multiplexer and at least two secondary antennas. The primary antenna is intended to be placed in the field of a near-field reader, the primary antenna having a first terminal and a second terminal. The at least one control and energy recovery circuit is connected to the first and second terminals of the primary antenna in order on the one hand to produce a voltage supply and on the other hand to communicate with the reader, the control circuit having at least one control output. The at least one first multiplexer is powered by the supply voltage and has at least one control input of a primary signal input/output and at least two secondary signal inputs/outputs, the input control being connected to the control output of the control circuit and the primary signal input/output being connected to the first terminal of the primary antenna. The at least two secondary antennas each have a first terminal and a second terminal, the first terminal of each secondary antenna being connected to one of the secondary signal inputs/outputs of the first multiplexer and the second terminal of each antenna secondary being connected to the second terminal of the primary antenna.

In a particular embodiment, the relay may comprise at least a second multiplexer powered by the supply voltage and having at least one control input for a primary signal input/output and at least two secondary signal inputs/outputs, the control input being connected to the control output of the control circuit and the primary signal input/output being connected to the second terminal of the primary antenna, the second terminal of each secondary antenna being connected to the second terminal of the primary antenna via one of the secondary signal inputs/outputs of the second multiplexer.

According to one embodiment, the primary antenna may comprise at least one turn connected in parallel to a primary tuning capacitor, the terminals of the capacitor corresponding to the first and second terminals of the primary antenna.

According to another embodiment, the primary antenna may comprise a plurality of turns connected in parallel to the primary tuning capacitor.

[0012] In a preferred embodiment, each secondary antenna may comprise a turn in parallel on a secondary tuning capacitor.

To avoid interference between secondary antennas, the relay may include at least a third multiplexer and at least two circuits of secondary antenna neutralization coupled to each of the secondary antennas, the third multiplexer and the neutralization circuits being powered by the supply voltage, a control input of each neutralization circuit being connected to an output of the third multiplexer.

Preferably, each neutralization circuit may include at least one transistor short-circuiting the secondary tuning capacitor of the secondary antenna.

To facilitate the positioning of the reader circuit relative to the primary antenna, the relay may include a coupling indicator circuit which gives visual information depending on the electromagnetic coupling of the primary antenna with the reader circuit.

[0016] According to one embodiment, the coupling indicator circuit may be a light-emitting diode thermometric circuit which lights a number of diodes proportional to the supply voltage provided by the control circuit.

[0017] The invention also proposes a plate incorporating a near-field communication antenna relay, said plate comprising a location zone corresponding to a secondary antenna array making it possible to locate an electronic tag when a near-field reader is positioned on the primary antenna.

As a variant, the invention also proposes a plate integrating a near-field communication antenna relay, said plate comprising a plurality of communication zones each corresponding to a secondary antenna, the secondary antennas being sufficiently spaced so as not to not be able to communicate with an electronic tag located in a neighboring communication zone.

[0019] Brief Description of Figures

The invention will be better understood and other characteristics and advantages thereof will appear on reading the following description of particular embodiments of the invention, given by way of illustrative and non-limiting examples, and referring to the attached drawings, among which:

[0021] [Fig. 1] shows an example of a block diagram of the relay according to the invention, [0022] [Fig. 2] and [Fig. 3] show a model of the resonant circuit equivalent to the diagram in figure 1 according to different operating modes,

[0023] [Fig. 4] shows a functional diagram of a reader device coupling assistance circuit,

[0024] [Fig. 5] shows a preferred embodiment of a primary antenna,

[0025] [Fig. 6] shows a variant of the diagram of figure 1 using an array of antennas,

[0026] [Fig. 7] shows another variant of the diagram of figure 1,

[0027] [Fig. 8] and [Fig. 9] illustrate examples of use of the relay according to the invention.

[0028] Detailed Description

The following description will describe a main embodiment as well as possible variants and improvements based on the main example. In order to simplify the following description, the same reference will be used in different figures when the referenced object is the same or of the same nature. In addition, certain elements will be omitted from certain figures in order to avoid overloading them unnecessarily.

Figure 1 shows a block diagram of an embodiment of a relay 1 according to the invention. The relay 1 comprises a primary antenna 10 and two secondary antennas 20. The primary antenna 10 has a first terminal 11 and a second terminal 12. Each secondary antenna 20 also has a first terminal 21 and a second terminal 22. The first terminals 21 of the secondary antennas 20 are connected to the first terminal 11 of the primary antenna 10 via a first multiplexer 30. The second terminals 22 of the secondary antennas 20 are connected to the second terminal 12 of the primary antenna 10 via a second multiplexer 40. The first and second multiplexers 30 and 40 also have a control input connected to a control output of a control circuit 50, the first and second multiplexers 30 and 40 receiving the same control signals in order to select the secondary antenna 20 to be brought into contact with the primary antenna 10. Alternatively, it is possible to remove one of the first or second multiplexers 30 or 40. In this case, all the first terminals 11 and 21 or second terminals 12 and 22 of the first and second antennas 10 and 20 are connected together, the selection of secondary antennas being done respectively only by the second or the first multiplexer.

The control circuit 50 is an integrated circuit of the microcontroller type, or of the hard-wired logic automaton type, having two terminals to be connected to a near-field communication antenna and which also has configurable inputs/outputs GPIO type (General Purpose Input Output). The control circuit 50 can also self-power on the communication magnetic field and supply a supply voltage VCC to other circuits. By way of example, the control circuit can be the SIC4310 circuit offered by the company Silicon Craft, or an equivalent circuit offered by the company NXP. The two near-field communication terminals of the control circuit 50 are respectively connected to the first and second terminals 11 and 12 of the primary antenna 10 in order to be able to recover energy from a magnetic field and also to communicate on the magnetic field. The configurable input/output terminals constitute the control output which is connected to the control input of the multiplexers 30 and 40. Depending on the type of multiplexer 30 and 40 used, the number of inputs/outputs used may vary according to whether it is a serial or parallel type control bus. A tank capacitor 51 may be connected in parallel between the VCC supply voltage and ground outputs of the control circuit 50 in order to stabilize the supply voltage supplied to the multiplexers 30 and 40.

The general operating principle of relay 1 consists of placing a reader circuit in the field of primary antenna 10 in order to receive a modulated magnetic field. The primary antenna 10 transforms the magnetic field into electrical signals supplied to the control circuit 50. The control circuit 50 transforms the electrical signals into supply energy stored in the reservoir capacitor 51 and identifies itself to the reader circuit. The reader circuit can then send a selection command to the control circuit 50. The selection command is then transformed by the control circuit 50 into a command for the multiplexers 30 and 40. The command received by the multiplexers 30 and 40 makes it possible to bring a selected secondary antenna 20 into contact with the primary antenna 10. All the commands subsequent readings of the reader circuit received by the primary antenna 10 are then retransmitted by the secondary antenna 20 selected.

In order to ensure the supply of relay 1 and good signal transmission at the level of a secondary antenna 20, it should be ensured that the primary antenna 10 and the secondary antenna 20 are permanently tuned on the field of the reader circuit in order to enter into resonance to amplify the field received from the reader and restore an amplified field at the level of the secondary antenna 20. In the embodiment of FIG. 1, the primary antenna 10 comprises a turn 13 and a tuning capacitor 14 and the secondary antennas 20 each comprise a turn 23 and a tuning capacitor 24. Those skilled in the art will understand that the size and the number of turns 14 and 24 of the antennas 10 and 20 can be variable depending on the frequency of the communication magnetic field and also depending on possible values for the tuning capacitors 14 and 24.

[0035] In order to enable a person skilled in the art to size the antennas 10 and 20 as well as possible, three modes of operation should be considered. A first mode of operation relates to the approach of a reader to the primary antenna 10. During this first mode of operation the first and second multiplexers 30 and 40 are not powered. A second mode of operation corresponds to a communication established between the reader and the control circuit 50 in which the first and second multiplexers 30 and 40 are powered but do not establish any connection with a secondary antenna 20. A third mode of operation corresponds to a communication established between the reader and the control circuit 50 in which the first and second multiplexers 30 and 40 are powered and establish a connection with a secondary antenna 20. FIG. 2 corresponds to a model of the resonant circuit equivalent to the diagram of FIG. 1 in the first and second modes of operation and FIG. 3 corresponds to a modeling of the resonant circuit equivalent to the diagram of FIG. 1 in the third mode of operation.

For these two figures 2 and 3, the primary antenna 10 is modeled by an inductor L13 and a capacitor C14 corresponding respectively to the turn 13 and to the tuning capacitor 14 in parallel. A capacitor C50 corresponds to the capacitor of the inputs of the control circuit 50 which comes in parallel on the capacitor C14. The first and second multiplexers 30 and 40 are respectively modeled by capacitors C30 and C40 placed between one of the terminals of capacitor C14 and the ground line. In FIG. 3, the modeling of the connected secondary antenna 20 consists in adding in parallel to the capacitor C14 a capacitor C24 and an inductor L23 corresponding respectively to the tuning capacitor 24 and to the turn 23. The first and second multiplexers 30 and 40 being identical and receiving the same supply voltages and the same control signals, the capacitors C30 and C40 are identical.

The resonance frequency F of the circuit of Figure 2 corresponds to the following formula:

[0038] [math 1]

[0040] Although the formula for determining the resonance frequency is the same, it should be noted that the capacities C30 and C40 vary according to the supply state of the first and second multiplexers 30 and 40. variation of the capacitances C30 and C40, it is necessary to size the tuning capacitor 14 so that its capacitance C14 is large enough to make the variation of the capacitances C30 and C40 negligible. By way of example, the variation of the capacitors C30 and C40 being of a few picofarads, it is possible to choose a capacitor C14 greater than 500 picofarads so that the variation in resonance frequency is less than one percent. Once the value of capacitor C14 has been chosen, inductance L13 should be determined according to the desired resonance frequency and the value of capacitors C14, C30, C40 and C50. The inductance L13 being determined, the person skilled in the art can dimension the turn 13. The resonance frequency F of the circuit of Figure 3 corresponds to the following formula:

[0042] [math 2]

In the case of Figure 3, it should be noted that the turns 23 can be drawn according to the surface that they must occupy on a plate and the resulting inductance L23 will be calculated according to the drawing of said turns 23. Once the inductance L23 has been calculated, the capacitance C24 is determined to bring the frequency F back to the value of the frequency of the field produced by the reader. It should be noted that, if the turns 24 have a relatively small surface with significant conductor lengths to connect them to the first and second multiplexers 30 and 40, the conductors will also have to be taken into account for the calculation of the inductance L23 of each secondary antenna 20. Thus, the capacitances C24 of the tuning capacitors 24 may be different for each secondary antenna 20.

As indicated above, the dimensioning of the turn 13 of the primary antenna 10 is constrained by the dimensioning of the tuning capacitor 14. Typically the value of the inductance is given by the following formula:

[0046] [math 3]

1

[0047] L13 =

(27TF) ^2X (C14+C50+— )

By way of example, the ISO/IEC 14443 standard defines a frequency of the communication field at a frequency of 13.56 MHz. Having defined a tuning capacitor having a capacitance greater than 500pF, the sum of the capacitances C14, C30, C40 and C50 will also be greater than 500pF. Thus, the inductance L13 must be less than 275 nanohenrys. A simplified calculation of the inductance L of a rectangular turn of sides A and B printed on a printed circuit with conductors having a width E can be done using the following formula:

[0049] [math 4]

[0051] with mq which corresponds to the magnetic constant. A person skilled in the art can calculate that a rectangular turn made with conductors 2 mm wide must be smaller than a rectangle of 6 cm by 8 cm. The person skilled in the art will take care to adjust the size of the turn 13 in order to obtain the inductance value which suits him best. It should be noted that for such a small inductance, it is also necessary to take into consideration the inductance corresponding to the conductors connected to the turn 13. An adjustment of the capacitance C14 can also be carried out after having produced the final design of the turn 13 and conductors connecting it to the tuning capacitor 14.

The turn 13 determined is relatively small. Considering a reader circuit of the mobile telephone type which also comprises an antenna whose surface is of the same order of magnitude, it is advisable to best position the mobile telephone on the primary antenna in order to ensure optimum coupling. Considering that the position of a near-field communication antenna can be placed in different places inside a mobile phone depending on the model, registration marks may not be enough to correctly position a phone on the antenna. primary 10.

An improvement making it possible to ensure optimum coupling can be the addition of a coupling aid circuit. The coupling aid circuit can be a circuit of the thermometric type with light-emitting diodes (hereinafter LEDs) which will make it possible to indicate by illuminating a number of LEDs proportional to the coupling between the reader and the primary antenna 10. Thanks to such a circuit, a user can move the reader at the level of the primary antenna until all the LEDs are lit.

[0054] Figure 4 shows a block diagram of an example of a coupling aid circuit 400. Typically, the coupling aid circuit 400 is connected to the supply voltage VCC and ground outputs of the circuit control 50 which provides a supply voltage which is proportional to the actual coupling between the primary antenna 10 and the reader. Those skilled in the art will understand that the coupling aid circuit of Figure 4 is given by way of example and can be replaced by other types of thermometric circuits.

The coupling aid circuit 400 comprises a voltage regulator 410 which makes it possible to supply LEDs 420, for example three in number. To this end, each LED 420 is connected in series with a resistor 430 and the channel of a transistor 440. The branch thus formed is connected between a regulated voltage output of the voltage regulator 410 and ground. Each resistor 430 is sized to limit the current in LED 420 when the channel of transistor 440 is saturated. Each transistor 440, for example of the MOSFET (Metal Oxide Semiconductor Field Effect Transistor) type, has its source connected to ground and its gate connected to the midpoint of a voltage divider bridge 450 which is connected between the voltage VCC power supply and ground. Each voltage divider bridge 450 comprises two resistors R1 and R2 in series whose values are adjusted so that the midpoint corresponds to the threshold voltage of the transistor 440 to which it is connected when the supply voltage corresponds to an ignition threshold. of the associated diode 420. The ignition thresholds are different for each 450 voltage divider bridge in order to light one, two or three 420 LEDs depending on the VCC supply voltage.

Another possibility of improving the coupling may consist in adapting the primary antenna so that it occupies a larger surface without however changing the inductance of said antenna. Such an enhancement can be used instead of or in combination with a coupling aid circuit.

By way of non-limiting example, FIG. 5 shows a primary antenna 10 comprising four turns 13′ connected in parallel to the tuning capacitor 14. The four turns 13′ are juxtaposed so as to cover a larger surface. only one whorl. In addition, the parallel mounting of the turns 13' has the effect of presenting an inductance equivalent to a quarter of the inductance of a single turn 13', which makes it possible to use larger turns. Many other antenna configurations using juxtaposed turns can be used by coupling the turns in parallel or by connecting branches of turns connected in series in parallel. The circuit of Figure 1 showed an embodiment using two secondary antennas. However, to produce a location plate, it is necessary to use a matrix of secondary antennas 20, like what is implemented in patent application WO 2021/038167. FIG. 6 shows an embodiment of a relay 1 according to the invention having a plurality of secondary antennas 20 arranged in rows and columns of a matrix making it possible to identify an electronic tag on a plane. The secondary antennas 20 are produced on two faces of a printed circuit or on two layers of printed circuit in order to insulate them electrically. The printed circuit or printed circuit layers can be made using one of many known technologies, using an epoxy resin, polyimide, paper, cardboard substrate covered with an etched copper conductive layer, in screen-printed conductive ink, in cut aluminum foil, the person skilled in the art, being able to choose what is most suitable according to the desired application. However, when a secondary antenna 20 is activated, the magnetic field will have the effect of exciting the secondary antennas 20 which are superimposed on it and causing them to resonate. To avoid such a coupling between the secondary antennas 20, it is necessary to neutralize the antennas which are not selected. The same coupling phenomenon can also occur with juxtaposed antennas when the latter are too close to each other. If the configuration of the secondary antennas presents a significant risk of coupling, it is then advisable to add neutralization circuits. In order not to overload FIG. 6, an example embodiment of neutralization circuits is shown in FIG. 1 although it is not necessary to neutralize the secondary antennas 20 if these are two in number and if they are far enough away from each other. A person skilled in the art can easily transpose them to the diagram in Figure 6.

In order to neutralize the secondary antennas 20, the relay 1 comprises a third multiplexer 60, which can be of the same nature as the first and second multiplexers 30 and 40 or which can be simply mono directional, the important thing being that the third Multiplexer 60 has one signal input and a plurality of signal outputs. The third multiplexer has a control input connected to a control output of a control circuit 50 and receives the same control signals as the first and second multiplexers 30 and 40 to select a signal output corresponding to the secondary antenna 20 selected. The signal input of the third multiplexer is connected to a logic control level, for example a low level corresponding to ground. Each signal output of the third multiplexer 60 is connected to a control input of a neutralization circuit 70 associated with a secondary antenna 20. By default, if the control input of the neutralization circuit 70 does not receive a logic level of control which deactivates said neutralization circuit 70, the latter is activated and neutralizes the secondary antenna which is associated with it.

To neutralize a resonant antenna composed of a turn in parallel on a capacitor, many possibilities are offered, such as detuning the resonant circuit or opening the resonant circuit. According to a preferred embodiment, it is proposed to detune the circuit by shorting the tuning capacitor 24. Such a shorting can be achieved using a transistor. However, the secondary antenna 20 not being connected to a reference potential, it is preferred to use a neutralization circuit 70 which comprises two transistors 71 and 72 having their channel respectively connected between one of the terminals of the capacitor d chord 24 and mass. The gates of the two transistors 71 and 72 are connected together to an output of the third multiplexer 60 and to a first terminal of a pull-up resistor 73. A second terminal of the pull-up resistor 73 is connected to the supply voltage VCC. In order to reduce the consumption of the neutralization circuits as much as possible, the transistors 71 and 72 are preferably of the MOSFET type and the pull-up resistor 73 has a very high resistance.

When a secondary antenna 20 is not selected, the corresponding signal output of the third multiplexer 60 is not connected to ground, the gates of transistors 71 and 72 then receive the supply voltage VCC by the intermediary of the pull-up resistor 73 and become on. Transistors 71 and 73 being on, the terminals of tuning capacitor 24 are then connected to ground, which puts tuning capacitor 24 in short circuit, thus neutralizing the secondary antenna 20 which is not selected.

When a secondary antenna is selected, the corresponding signal output of multiplexer 60 is connected to ground as well as the gates of transistors 71 and 72, which blocks the transistors. The transistors being blocked, the secondary antenna 20 selected can resonate freely.

According to the embodiment of Figures 1 and 6, the number of secondary antennas 20 can be limited by the capacities of the multiplexers 30, 40 and 60 and by the number of control outputs of the control circuit 50. Indeed , the control circuit 50 only transcodes commands received from the reader circuit into signals on its inputs/outputs. Addressing a serial bus requires that the reader circuit send to the control circuit 50 one command per bit sent on the serial bus, which requires a relatively large number of commands to address the multiplexers 30, 40 and 60. use of a parallel bus to control the multiplexers 30, 40 and 60 is however limited by the number of inputs/outputs available on the control circuit 50. If the control circuit 50 has only four inputs/outputs of type GPIO multiplexers can address at most eight secondary antennas 20.

If it is desired to address a number of antennas greater than eight, it is possible to add a second control circuit 50' as represented in FIG. 7 which shows another variant of the diagrams of FIGS. 1 and 6. The second control circuit 50' is identical to the control circuit 50. The two near-field communication terminals of the second control circuit 50' are connected in parallel to the two near-field communication terminals of the control circuit 50. Thus the reader circuit can address either of the control circuits 50 and 50'. In addition, the second control circuit 50' also has supply voltage VCC and ground outputs also connected in parallel to the supply voltage VCC and ground outputs of the control circuit 50. Thus the control circuits 50 and 50' both contribute to the supply of the multiplexers 30, 40 and 60. The configurable inputs/outputs of the second control circuit 50' can be juxtaposed with the inputs/outputs of the control circuit 50 which makes it possible to doubling the size of a parallel control bus, increasing the maximum bus size from four to eight control signals, which can address up to 128 secondary antennas. For this purpose it is possible to use multiplexers having a greater number of inputs/outputs or even to add additional multiplexers 30', 40' and 60' increasing the addressing capacity of secondary antennas 20 .

In Figure 7, the first, second and third multiplexers 30, 40 and 60 are doubled. The control inputs of the 30, 30', 40, 40', 60 and 60' multiplexers only receive part of the control bus. However, it is possible to add a larger number of multiplexers provided that you remain within the supply capacity limit that can be obtained from the communication field provided by the reader.

According to a first example of implementation, FIG. 8 shows a game board 800 intended to cooperate with a smart mobile phone 810, commonly called a smartphone. To this end, the game board 800 incorporates in its thickness a printed circuit on which the various components constituting the relay 1 object of the invention have been drawn or welded depending on the type of component. By way of example, the game board includes a game zone 820 itself printed according to the game. of a piece provided with an electronic identification tag placed on said game area 820. Turns 13' of a primary antenna 10 are placed under a deposit area 830 located on a side part of the game board 800. The other components of relay 1 are grouped together in a neutral zone 840 of game board 800, preferably as far as possible from turns 13' and 23 in order to reduce the risk of interference. An 850 indication zone can group 420 LEDs inside the 840 neutral zone.

[0067] Prior to the implementation of the game, it is necessary to download an application in the smartphone 820 which includes a method for locating electronic tags such as for example described in patent application WO 2021/038167 and modified to take into account relay 1. Once the program has been loaded, the smartphone 820 is placed by a user on the zone of deposit 830. The smartphone 820 is then moved over this deposit zone until the three LEDs 420 are lit. The smartphone 820 establishes a first communication with the control circuit 50 during an initialization of the game. Thereafter, each time a secondary antenna 20 must be selected the smartphone 820 will send a command to the control circuit 50 indicating to it the value of the output signals which must be positioned on the control outputs. The rest of the location process can then be implemented by the smartphone 820 identical to what is described in application WO 2021/038167. Those skilled in the art will be able to appreciate that the use of such a method makes it possible to have a location precision which is approximately four times less than the width of a turn 23 of secondary antennas, which makes it possible to avoid use a greater number of secondary antennas 20.

Other examples of implementation can be considered. It is relatively common in restaurants for customers to request that the bill be split between them. The EMV standard (acronym for Europay MasterCard Visa) only authorizes a contactless banking transaction if there is only one bank card in the communication field of a payment terminal. A distributed payment is therefore not possible unless there are several antennas on the payment terminal.

According to a second example of implementation, FIG. 9 shows a payment tray 900 intended to cooperate with a payment terminal 910 to make a contactless payment distributed on several bank cards. To this end, the payment plate 900 incorporates in its thickness a printed circuit equipped with the various components constituting the relay 1 which is the subject of the invention. The payment tray 900 comprises a plurality of payment areas 920, for example eight, identified by rectangles of a size slightly larger than the size of a bank card. Eight turns 23 of secondary antennas 20 are each arranged under each payment zone 920. In order to be able to communicate only with the bank card located in the payment zone 920, each turn 23 is of small size and is placed in the center of each payment zone 920. Those skilled in the art will notice that it is not necessary to neutralize the secondary antennas 20 in this type of application because these these do not interfere with each other. Turns 13' of a primary antenna 10 are placed under a deposit zone 930 located on a side part of the payment platform 900. The other components of the relay 1 are grouped together in a neutral zone 940 of the payment platform 900. A zone indication 850 can group the LEDs 420 inside the neutral zone 940.

To make a distributed payment, the payment terminal 910 has a distributed payment mode intended to cooperate with the payment platform. When the merchant wants to make a distributed payment, he will place the bank cards on which the payment must be distributed on the payment zones 920, at the rate of one card per payment zone 920. Then, the merchant will enter the payment terminal 910 the total to be paid. The payment terminal 910 is then placed on the deposit area 930 by adjusting the position of said terminal 910 until the three LEDs 420 are lit. The merchant can then launch the distributed payment application.

[0071] Distributed payment operates in two phases. A first phase consists of determining how many bank cards are present. To this end, the payment terminal will send secondary antenna selection commands 20 to the control circuit 50 and then detect whether a bank card is present for each antenna. After having selected and interrogated all the secondary antennas 20, the payment terminal 910 knows the number of bank cards to be debited as well as the location corresponding to a secondary antenna 20. At the end of this first phase, the payment terminal displays the number of cards detected, calculates the amount to be paid for each bank card and requests confirmation of the debit. After confirmation of the debit, the payment terminal 910 will go into a second debit phase by performing debit operations for each bank card. An antenna selection command is sent to the control circuit 50 then a deselection command is sent to the control circuit so that the latter no longer responds to the commands sent by the payment terminal. The payment according to the EMV protocol is then launched to make the payment with the card positioned on the selected secondary antenna 20 which happens to be the only one to respond to the commands sent by the payment terminal 910. At the end payment, the payment terminal 910 sends a selection command to the control circuit 50 so that the latter can again interact with the payment terminal 910. Another secondary antenna 20 is selected to proceed with the next payment after having again deselected the control circuit 50. The operation is thus repeated until all the payments have been made.

Other applications can be envisaged, such as for example contactless charging of electronic devices which it is desired to charge one after the other. It is even possible to envisage simultaneous recharging provided that several antennas are selected at the same time, which can be done by using two control circuits in parallel and/or by multiplying the number of multiplexers.

Claims

Claims [Claim 1] A near-field communication antenna relay (1) comprising a primary antenna (10) intended to be placed in the field of a near-field reader (810, 910), the primary antenna (10) having a first terminal (11) and a second terminal (12), characterized in that it comprises: - at least one control (50, 50') and energy recovery circuit connected to the first and second terminals (11, 12) of the primary antenna (10) in order on the one hand to produce a supply voltage (VCC) and on the other hand to communicate with the reader, the control circuit (50, 50') having at least one control output, - at least one first multiplexer (30, 30') powered by the supply voltage (VCC) and having at least one control input for a primary signal input/output and at least two inputs/outputs secondary signal, the control input being connected to the control output of the control circuit (50, 50') and the primary signal input/output being connected to the first terminal (11) of the primary antenna ( 10), - at least two secondary antennas (20) each having a first terminal (21) and a second terminal (22), the first terminal (21) of each secondary antenna (20) being connected to one of the inputs /secondary signal outputs of the first multiplexer (30, 30 ') and the second terminal (22) of each secondary antenna (20) being connected to the second terminal (12) of the primary antenna (10). [Claim 2] Near-field communication antenna relay according to the preceding claim, which comprises at least a second multiplexer (40, 40') powered by the supply voltage (VCC) and having at least one input of control of a primary signal input/output and at least two secondary signal inputs/outputs, the control input being connected to the control output of the control circuit (50, 50') and the input/ primary signal output being connected to the second terminal (12) of the primary antenna (10), the second terminal (22) of each secondary antenna (20) being connected to the second terminal (12) of the primary antenna (10) via one of the secondary signal inputs/outputs of the second multiplexer (40). [Claim 3] Near-field communication antenna relay according to one of the preceding claims, in which the primary antenna (10) comprises at least one turn (13, 13') connected in parallel to a tuning capacitor primary (14), the terminals of the capacitor (14) corresponding to the first and second terminals (11, 12) of the primary antenna (10). [Claim 4] A near field communication antenna relay according to the preceding claim, wherein the primary antenna (10) has a plurality of turns (13') connected in parallel across the primary tuning capacitor (14). [Claim 5] A near field communication antenna relay according to any preceding claim, wherein each secondary antenna (20) includes a coil (23) in parallel to a secondary tuning capacitor (24). [Claim 6] A near-field communication antenna relay according to one of the preceding claims, which comprises at least a third multiplexer (60, 60') and at least two secondary antenna disabling circuits (70) coupled to each of the secondary antennas (20), the third multiplexer (60, 60') and the neutralization circuits (70) being powered by the supply voltage (VCC), a control input of each neutralization circuit (70) being connected to an output of the third multiplexer (60, 60'). [Claim 7] Near-field communication antenna relay according to the preceding claim when dependent on claim 5, wherein each neutralization circuit (70) comprises at least one transistor (71, 72) shorting the secondary tuning capacitor (24) of the secondary antenna (20). [Claim 8] A near-field communication antenna relay according to any preceding claim, which includes a coupling indicator circuit (400) which provides visual information as a function of the electromagnetic coupling of the primary antenna (10) with the reader circuit (810, 910). [Claim 9] A near field communication antenna relay according to the preceding claim, wherein the coupling indicator circuit (400) is a light emitting diode thermometric circuit (420) which lights a number of diodes proportional to the supply voltage (VCC) provided by the control circuit (50). [Claim 10] Tray (800) integrating a relay (1) according to one of Claims 1 to 8, which comprises a location zone (820) corresponding to a matrix of secondary antennas (20) making it possible to locate an electronic tag when a near field reader is positioned on the primary antenna. [Claim 11] Plate (900) incorporating a relay according to one of claims 1 to 8, which comprises a plurality of communication zones (920) each corresponding to a secondary antenna (20), the secondary antennas (20) being sufficiently spaced apart so as not to be able to communicate with an electronic tag located in a neighboring communication zone (920).