EP3072244A1

EP3072244A1 - Method and device for locating mobile elements provided with standard nfc tags

Info

Publication number: EP3072244A1
Application number: EP14809487.3A
Authority: EP
Inventors: Valentin LEFÈVRE; Laurent Chabin; Christophe Duteil
Original assignee: EPAWN
Current assignee: Starbreeze Paris SAS
Priority date: 2013-11-20
Filing date: 2014-11-18
Publication date: 2016-09-28
Also published as: BR112016010267A2; FR3013482B1; KR102243347B1; US20160301449A1; KR20160110941A; BR112016010267B1; JP6509854B2; FR3013482A1; US10090888B2; CN105765875A; CN105765875B; WO2015075370A1; JP2016541180A

Abstract

The invention relates to the location of mobile elements provided with standard NFC tags. The location device (200) includes transmission means (215) for transmitting a signal to query said at least one tag, monitoring means (205, 245) and a plurality of receiving means (225) selectively connected to said monitoring means, said receiving means being receptive to said querying signal and to a response signal from said at least one tag. Said monitoring means are configured such as to measure in sequence signals from receiving means connected to said monitoring means and to estimate the position of said at least one tag by interpolating measurements.

Description

METHOD AND DEVICE FOR LOCATING MOBILE ELEMENTS

PROVIDED WITH STANDARD TAGS OF NFC TYPE

Field of the invention

The present invention relates to the interfaces between users and computer systems, particularly in the field of games, and more particularly a method and a device for locating mobile elements provided with standard NFC type tags (Near Field Communication acronym in English terminology). ), that is to say tags using a near field communication technology, with a computer system, further offering conventional functions of reading and writing.

Context of the invention

In many situations, it may be necessary for a computer system to detect moving elements as well as their position and / or orientation to enable the latter to react accordingly. Thus, for example, in a chess game allowing a user to play against a virtual player simulated by the computer system, the application implemented on the computer system must know all the pieces of the chessboard and their position, particularly the pieces moved by the user and their position, to calculate his shot.

There are solutions for detecting real objects on a game board using NFC technology or RFID (Radio Frequency IDentification), it being observed that NFC technology is a particular extension of RFID technology. The game board includes an NFC reader, also called NFC reader, generally placed under the game board. In addition, each object is provided with an NFC type tag including a unique identifier. Thus, by reading all the NFC tags located near the game board, it is possible to detect all the objects present on the game board. However, such a system does not generally make it possible to precisely determine the position and / or the orientation of the objects.

There are also solutions to detect real objects on a game board and determine their position and / or orientation to use these objects as interface of a computer system.

Thus, for example, a technology developed by the company N TRIG consists of equipping NFC tags with a contact tip making it possible to establish contact with a capacitive surface of a screen. The location of the point of contact makes it possible to locate the NFC tag. Such a solution, however, requires a modification of the NFC tags resulting in an increase in their manufacturing costs and the use of a capacitive surface whose price is significant.

There are also solutions using, in the NFC reader, several antennas that can be used sequentially by multiplexing. Each antenna corresponding to a box of a game board makes it possible to detect the presence of an NFC tag on the corresponding box and to obtain its identifier. Knowing the position of the antenna, it is possible to deduce the position of the NFC tag. The precision here is related to the size of the boxes including the antennas. Such boxes may, for example, be squares measuring 4 cm square. The precision is then 4 cm. However, if such a solution makes it possible to use standard NFC tags, it requires predetermining all the positions to which NFC tags must be detected. Summary of the invention

The invention solves at least one of the problems discussed above.

The invention thus relates to a device for locating at least one mobile element provided with at least one tag using a near-field communication technology, this device comprising the following means, transmitting means for transmitting an interrogation signal of said at least one tag;

- control means;

a plurality of reception means selectively connected to said control means, said reception means being receptive to said interrogation signal and to a response signal of said at least one tag;

said control means being configured to sequentially measure signals from receiving means connected to said control means and to estimate the position of said at least one tag by interpolation of measurements.

The device according to the invention thus makes it possible to know in real time the number of tags using a near-field communication technology, present near a detection surface, the identifiers of these tags as well as their position with a precision that can be less than one millimeter. The tags used may in particular be standard tags, in particular NFC tags, for example bipolar NFC tags including an antenna using a carrier frequency of 13.56 MHz.

According to a particular embodiment, the device further comprises switching means controlled by said control means for sequentially selecting said receiving means. The device according to the invention thus makes it possible to improve the tag location accuracy in a simple manner.

According to a particular embodiment, the device further comprises adaptation means for tuning said receiving means to the frequency of a carrier of a signal transmitted by said transmitting means.

According to a particular embodiment, the method further comprises a specific component connected to said control means and to said transmitting means for performing specific tag reading functions.

According to a particular embodiment, said control means comprise means for determining a value representative of the amplitude of a component corresponding to a carrier of a signal received via said reception means. According to a particular embodiment, said control means comprise means for determining a value representative of the amplitude of a useful component of a signal received via said reception means, used to exchange data.

According to a particular embodiment, said receiving means comprise at least one set of loops extending along at least one dimension of a surface on which the position of said at least one tag must be estimated.

According to a particular embodiment, each of said receiving means comprises two parts, each of said two parts being located on either side of said transmitting means. The device thus makes it possible to improve the location of tags.

According to a particular embodiment, said transmission means and said control means are configured to read at least one piece of data stored in said at least one tag or write at least one piece of data in said at least one tag. The device according to the invention offers standard functions for reading or writing on these tags.

According to a particular embodiment, the device further comprises selection means and processing means selectively connected to said reception means and to said control means, said selection means, said processing means and said control means being configured to determining the position of at least one tag implementing a communication technology distinct from the near-field communication technology. The device according to the invention is thus able to determine the position of standard tags using near-field communication technology and tags using a different communication technology.

The invention also relates to a method for locating at least one mobile element provided with at least one tag using a near-field communication technology, the method being implemented in a device comprising transmission means for transmit at least one interrogation signal of at least one tag, control means and a plurality of receiving means selectively connected to said control means and receptive to signals transmitted by said transmitting means and by at least one tag, the method comprising the following steps,

control for transmitting an interrogation signal of said at least one tag;

sequential selection of reception means and measurement of at least one signal received via said selected reception means, said received signal resulting from at least one signal transmitted by said transmission means and a signal transmitted by at least one tag in response to said signal transmitted by said transmitting means; and

estimating the position of said at least one tag by interpolation of signal measurements received via selected reception means.

The method according to the invention thus makes it possible to know in real time the number of tags using a near-field communication technology, present near a detection surface, the identifiers of these tags as well as their position with a precision which can be less than one millimeter. The tags used may in particular be standard tags, in particular NFC tags, for example bipolar NFC tags including an antenna using a carrier frequency of 13.56 MHz.

According to a particular embodiment, the method comprises a first step of estimating an approximate position of said at least one tag and a second step of estimating the position of said at least one tag, said second step of estimating the a position comprising said steps of controlling transmission of an interrogation signal, sequential selection of reception means and measurement of at least one signal received via said selected reception means and estimation of the position of said at least one a tag by interpolation of signal measurements received via selected receiving means.

According to a particular embodiment, said first step of estimating a position comprises a step of measuring the amplitude of a component corresponding to a carrier of a signal received via said means receiving and / or amplitude of a useful component of a signal received via said receiving means, used to exchange data.

According to a particular embodiment, the method comprises an initial step of obtaining a number of identified tags and identified tag identifiers.

According to a particular embodiment, said steps for controlling the transmission of an interrogation signal, sequential selection of reception means and measurement of at least one signal received via said selected reception means and estimation of the position of said at least one tag by interpolation of received signal measurements via selected receiving means is performed for each identified tag.

According to a particular embodiment, said step of measuring at least one received signal comprises a step of measuring the amplitude of a component corresponding to a carrier of a signal received via said reception means and / or amplitude of a useful component of a signal received via said receiving means used to exchange data.

According to a particular embodiment, the method further comprises a step of reading at least one piece of data stored in said at least one tag or writing at least one piece of data in said at least one tag. The method according to the invention thus offers standard reading or writing functions on these tags.

The invention also relates to a computer program comprising instructions adapted to the implementation of each of the steps of the method described above when said program is run on a microcontroller. The advantages provided by this computer program are similar to those mentioned above with regard to the method.

Brief presentation of the figures

Other advantages, aims and features of the present invention will emerge from the detailed description which follows, given by way of non-limiting example, with reference to the accompanying drawings in which: - Figure 1 schematically illustrates the principle of communication between a tag reader using the near field communication technology and such a tag;

FIG. 2 illustrates an exemplary device for locating tags according to one embodiment of the invention;

FIG. 3 illustrates an exemplary architecture of the filtering and adaptation unit represented in FIG. 2;

FIG. 4 illustrates an example of Descartes of the software embedded in the microcontroller represented in FIG. 2, that is to say an example of steps implemented in the device described with reference to FIGS. 2 and 3 to determine the positioning tags on a detection surface and allowing reading and writing of data with a tag;

FIG. 5, comprising FIGS. 5a and 5b, illustrates the measurement of the amplitude of the component corresponding to the carrier of the signal received at the terminals of a given loop;

FIG. 6 illustrates a simplified example of configuration of loops used to estimate the abscissa of the position of a tag in a device such as that described with reference to FIG. 2;

FIG. 7 illustrates the theoretical variation of the amplitude of the retro-modulated carrier of a received signal as a function of the relative positions of the loop used (theoretically) and of the tag as well as the local approximation of the variation of this amplitude by a parabola, from measurements made using several loops, to deduce the position of a tag;

FIG. 8, comprising FIGS. 8a, 8b and 8c, illustrates the measurement of the average amplitude of the useful component (used to exchange data) of a received signal;

FIG. 9 illustrates the theoretical variation of the amplitude of the useful component of a retro-modulated signal as a function of the relative positions of the loop used (theoretically) and of the tag as well as the local approximation of the variation of this amplitude by a parabola, from measurements made using several loops, to deduce the position of a tag; FIG. 10, comprising FIGS. 10a and 10b, illustrates an example of mounting of double loops used for measuring response signals of a tag and determining its position; and

FIG. 11 illustrates an exemplary device enabling the location of different types of tags according to one embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION For the sake of clarity, the following description aims to implement a tag reader and tags exchanging signals with a carrier frequency of 13.56 MHz. commonly used. However, other carrier frequencies may be used. Similarly, if the targeted tags are essentially passive tags using a near field communication technology, that is to say NFC tags, the invention can be implemented with other types of tags, including RFID tags.

It is first recalled that the NFC technology is a technology based on the load modulation technique (or load modulation in English terminology), also called retro-modulation.

By varying the resistance or the capacitance at the terminals of the antenna of a tag implementing this technology, that is to say by modulating the charge represented by this tag, the tag modifies the energy consumption that it represents in the magnetic field emitted by the tag reader used. Due to the magnetic coupling existing between the antenna of the tag and that of the tag reader, this energy consumption tends to modify the value of the current flowing in the circuit of the antenna of the tag reader (this circuit being also called base station in Anglo-Saxon terminology).

Figure 1 schematically illustrates the principle of communication between a tag reader using near field communication technology and such a tag.

In a first phase (reference 100), the antenna of the tag reader emits a signal consisting simply of a carrier, here a carrier having a frequency of 13.56 MHz, to bring energy to the tag and "wake up". In a next phase (reference 105), the tag reader transmits, via its antenna, information (typically a command) to the tag by modulating the carrier.

After receiving energy and information, a tag can respond (typically based on the information received, by comparison with previously stored information), in a next phase (reference 1 10), by changing the impedance of its antenna, for example using a switch to short circuit or not its antenna. Such changes make it possible to introduce level changes on the carrier transmitted by the antenna of the tag reader as illustrated in FIG. 1 (reference 1 15).

These level changes are detected and decoded by the tag reader. Decoding makes it possible to form a bitstream representing the response of the tag. The latter does not respond directly by a radio technology, but according to this coupling mismatch phenomenon, this technique is called feedback by retro-modulation.

As illustrated in FIG. 1, the part of the signal resulting from the retro-modulation feedback (reference 1 15) comprises a component corresponding to the carrier and a useful component represented in the form of slots, permitting the transfer of data.

It is observed here that the signals exchanged between a tag reader and a tag are scrambled to make the exchanges more reliable. The nature of the scrambling is such that the binary distribution of the high states and the low states is homogeneous (there are on average as many bits in the high state as in the low state).

According to a general embodiment, a set of nested loops is placed above and / or below the antenna of the tag reader, thus forming a detection surface. The set of loops here comprises two types of loops, horizontal loops forming lines and vertical loops forming columns. They delimit the detection surface. The loops forming the lines are used to determine the ordinate of the position of a tag and the loops forming the columns are used to determine the abscissa of the position of the tag.

These loops receive the signal emitted by the antenna of the tag reader, placed under them. They are tuned to the frequency of the carrier transmitted by the antenna of the tag reader, for example a carrier having a frequency of 13.56 MHz. The quality factor of the tuning of the loops is preferably adjusted to limit the absorption of the electromagnetic field emitted by the antenna of the tag reader, while ensuring the minimum level of power received for a correct location.

When a tag is placed on the detection surface, i.e. above the tag reader antenna and the loop set, and a query is issued by the tag reader , the tag placed on the detection surface slightly detunes the inductive coupling between the loops on which it is placed and the antenna of the tag reader. This disagreement is measured over several loops to estimate, by interpolation, the position of the tag.

More specifically, the set of loops is configured such that several adjacent and nested loops are detuned, preferably at least three, by the presence of a tag. The measurement of characteristics of the signal at the terminals of these three adjacent loops (signal corresponding to the carrier transmitted by the tag reader, modified by a retro-modulation feedback linked to a response of a tag) then makes it possible, by interpolation, to calculate the exact position of the tag in a frame linked to the detection surface.

According to a particular embodiment (described more specifically with reference to FIGS. 5 to 7), the determination of the position of a tag is performed by measuring the amplitude of the component corresponding to the carrier of the signal received at the terminals of each of three adjacent and nested loops (this carrier typically having a frequency of 13.56 Mhz).

According to another particular embodiment (described more specifically with reference to FIGS. 8 and 9), which can be combined or not with the preceding one, the determination of the position of a tag is carried out by measuring the amplitude of the useful component ( used to exchange data) of the signal received at the terminals of each of three adjacent and nested loops.

These embodiments can be implemented with the device described with reference to FIG. 2. Indeed, the filtering and amplification unit used can preferably provide the two signals (amplitude of the component corresponding to FIG. carrier of a signal received at the terminals of a loop and amplitude of the useful component of a signal received at the terminals of a loop) to a microcontroller in charge of determining the position of a tag.

According to a particular configuration, each loop has a shape close to a rectangle. The length of the loops forming the lines is preferably substantially equal to the width of the tag location area (i.e. the detection surface). Similarly, the length of the loops forming the columns is preferably substantially equal to the height of the tag location area. Although this is not necessary, the widths of the loops forming the lines are substantially equal to each other, the widths of the loops forming the columns are substantially equal to each other and the width of the loops forming the lines is substantially equal to that of the loops forming the columns.

The tags here have a smaller antenna area than the area of the location area. It is observed that when the tags have circular shaped antennas (typically a spiral), the amplitude of the field detected by the loops forming the lines and the columns is maximized when the width of these loops is substantially equal to the diameter of the antenna tags.

In the case of tags having antennas of more complex shape, for example rectangle, an optimization of the coupling can be carried out by adjusting the width of the loops.

FIG. 2 illustrates an exemplary device for locating tags according to one embodiment of the invention. This device comprises here a tag reader. It should be noted that, for the sake of clarity, only three vertical loops are illustrated. However, the set of loops comprises more than three loops, their number being determined according to their dimensions and the size of the detection surface, and comprises vertical loops and horizontal loops as previously described. Similarly, the representation of these loops is schematic. Their arrangement is described with reference to FIGS. 6 and 10.

As illustrated, the device 200 here comprises a microcontroller 205 (also called MCU) to which is connected a specific component 210 (called chipset in English terminology) to perform specific functions of a tag reader. An antenna 215 for reading and / or writing tags is connected to the specific component 210 via an impedance adapter 220 (called antenna matching in English terminology). The elements 210, 215 and 220 are standard elements of tag reader for reading data stored in a tag and writing data in a tag.

The device 200 further comprises loops, in particular the vertical loops 225-i, 225-j and 225-k. It also includes horizontal loops (not shown). As illustrated, the terminals of the vertical loops shown are connected to multiplexers 230-1 and 230-2 via impedance adapters 235-i, 235-j and 235-k and signal attenuators 240-i, 240-j and 240-k, respectively.

Thus, for example, one of the terminals of the loop 225-i is connected to the multiplexer 230-1 via the impedance adapter 235-i and the signal attenuator 240-i while the other terminal of the Loop 225-i is connected to multiplexer 230-2 via the same impedance adapter 235-i and the same 240-i signal attenuator. The terminals of the loops 225-j and 225-k are connected in a manner similar to the multiplexers 230-1 and 230-2.

The loops used, in particular the loops 225-i, 225-j and 225-k are tuned to the frequency of the carrier transmitted by the antenna 215 of the tag reader, for example the frequency of 13.56 MHz. This agreement is made here by impedance adapters, especially adapters impedance 235-i, 235-j and 235-k. Such impedance adapters typically consist of an RLC circuit for obtaining a resonant frequency corresponding to the carrier frequency transmitted by the antenna of the tag reader (typically 1 3.56 MHz). At resonance, each loop therefore captures the signal comprising the carrier transmitted by the antenna 215 of the tag reader.

The signal attenuators used (in particular the 240-i, 240-j and 240-k signal attenuators) are intended to attenuate the signals received from the impedance adapters in order to limit the voltage of the signals transmitted to the multiplexers 230-1. and 230-2. The maximum voltage of these signals is generally the supply voltage of the device 200.

The signal attenuators may each consist of a resistor network or a resistor connected in series, the value of these resistors being determined as a function of the power of the signal transmitted by the antenna 215 of the tag reader.

The output of the multiplexers 230-1 and 230-2, controlled by the microcontroller 205, is directed towards a filtering and matching unit 245. One of these outputs, for example the output of the multiplexer 230-1, is connected. GND ground (ground in English terminology). The other output, here the output of the multiplexer 230-1, represents the output signal S of one of the loops (according to the control of the multiplexer).

The filtering and adaptation unit 245 is connected to the microcontroller 205 to transmit to it the signal SE representing the amplitude of the component corresponding to the carrier of the signal S received at the terminals of the loop to which it is connected (via the multiplexers 230-1 and 230-2), ie the amplitude of the envelope of the carrier of the signal S received by this loop and / or the signal SR representing the amplitude of the useful component (used for exchanging data) of the signal received at the terminals of the loop to which this unit is connected.

Finally, the microcontroller 205 is also connected to a host computer 250 which controls the microcontroller 205 according to the application requirements, for example according to the rules of a game executed by the host computer 250, and to whom The estimated positions of tags are transmitted (as well as, preferably, the number of tags detected and their identifiers).

The device 200 thus comprises a set of loops each connected to an impedance adapter and a signal attenuator and, selectively to a filtering and adaptation unit.

It is observed here that the loops are not connected to each other (there is no common mass). It is therefore possible to isolate the loops from each other and thus avoid propagating a signal received by a loop on other loops.

The microcontroller 205 addresses the multiplexers 230-1 and 230-2, in parallel, to select a particular loop on which measurements are made. Thus, the multiplexer 230-1 makes it possible to connect one of the terminals of a particular loop to ground while the multiplexer 230-2 makes it possible to connect the other terminal of this loop to the filtering and adaptation unit 245. to transmit the signal S to be measured at this unit.

The device 200 makes it possible to estimate the position of a tag 255.

FIG. 3 illustrates an exemplary architecture of the filtering and adaptation unit 245 represented in FIG. 2.

The filtering and adaptation unit 245 essentially has two functions:

extraction of the component corresponding to the carrier of the signal S received at the terminals of the loop to which this unit is connected, typically a carrier having a frequency of 13.56 MHz, to enable the transmission of a signal SE representing the amplitude this component; and

extraction of the bit stream transmitted by the interrogated tag, while retaining the amplitude information of the retro-modulated signal S obtained at the terminals of the loop to which this unit is connected, to enable transmission of a signal SR representing the amplitude of the useful component (used to exchange data) of the signal received at the terminals of the loop to which this unit is connected. The filtering and adaptation unit 245 connected, at the input, to the multiplexer 230-1 and, at the output, to the microcontroller 205 comprises an operational amplifier 300 for amplifying the received signal, a first rectifier 305 for cutting a portion of the amplified signal and a rejector filter 310 to attenuate the contribution of the carrier frequency (typically 1 3.56 MHz). The output of the rejector filter 310 is a voltage which represents the amplitude of the component corresponding to the carrier of the received signal (signal SE).

In addition, the filtering and adaptation unit 245 comprises a gain element 31 and a bandpass filter 320 for extracting the bit stream resulting from the response of the interrogated tag. The terminals of the bandpass filter used may be of the order of 26 KHz and 213 KHz. A gain controller 325 is used to increase the range of the filtered signal where the circuit does not saturate. Finally, an integrating rectifier filter attenuates the high frequency noise of the signal by summing and rectifies the signal in the positive voltages to allow an analog-to-digital conversion within the microcontroller 205. Each bit transmitted by the interrogated tag makes the integrating filter perform a no integration.

It is first recalled here that the binary distribution of the high states and the low states in the bit stream resulting from the response of a tag is homogeneous and that, therefore, the integration of this signal is representative of its amplitude. .

It is also observed that if the NFC standard imposes a response of the interrogated tag within a maximum period following its interrogation, the response is carried out, in practice, after a constant time following a read command.

This delay can be characterized in the laboratory or evaluated by the microcontroller 205 for each tag, by measuring the delay between the command and the return of the reading from the specific component 210. This delay includes the response times of the entire chain of processing and includes the response time of the tag. The part of the independent delay of the tag can be pre-characterized in the laboratory (it does not vary), the delay of the tag can be determined easily.

Following the subtraction of the portion of the delay independent of the tag to the observed response time, the microcontroller stores the delay of the tag. This time being determined, the microcontroller is able to release the 'reset' of the integrator just before the start of the response phase of the interrogated tag.

In order for the filter to have the time to integrate data over a sufficiently long period to obtain a good accuracy of the measurement of the received power (that is to say of the amplitude of the useful component), the controls of Reading tags should require reading a minimum of bits or bytes.

The output of the integrating rectifier filter 330 corresponds to the signal SR representing the amplitude of the useful component of the signal received at the terminals of the loop to which the unit 245 is connected.

FIG. 4 illustrates an example of Descartes of the software embedded in the microcontroller represented in FIG. 2, that is to say an example of steps implemented in the device described with reference to FIGS. 2 and 3 for determining the position tags on a detection surface and allow the reading of data stored in tags and the writing of data in tags.

The execution of these steps is here controlled by the microcontroller 205 which comprises for example a firmware (or firmware in English terminology) adapted to this control.

As illustrated, a first step (step 400) is for transmitting an inventory request of all the tags present on the detection surface in order to obtain the number of tags and their identifiers. Such a request is here transmitted by the microcontroller 205 to the specific component 210. This is, for example, a request compliant with the SPI standard (Serial Peripheral Interface acronym in English terminology).

It is observed here that the division of tasks between the microcontroller 205 and the specific component 210 may vary according to the firmware of the microcontroller 205 and the type of specific component 210 used. According to the example illustrated in FIG. 4, the specific component 210 is responsible for obtaining the number of tags present on the detection surface and their identifiers.

Thus, after having received an inventory request, the specific component 210 modulates the carrier transmitted by the antenna of the tag reader to encode a tag identification command (step 402).

The specific component 210 decodes the responses received in order to count the number of tags, noted T, present and memorize their identifiers in an array referenced here IDQ. The number of tags and the array of tag identifiers are then transmitted to the microcontroller 205 (step 404). Again, the SPI standard can be used for this transmission.

A variable t representing a tag index among all the tags identified is initialized to the value 1 (step 406).

A test is then performed to determine if the value of the index t is less than or equal to the variable T (step 408). If the value of the index t is greater than the variable T, the variable T, the array of identifiers ID () and a table P () representing the positions of the identified tags are transmitted by the microcontroller 205 to the host computer 250 ( step 410).

The algorithm then returns to step 400 to re-perform a tag identification and localization cycle. Such a return can be automatic and / or controlled by the host computer 250.

On the other hand, if the value of the index t is less than or equal to the variable T, a query for interrogating the tag having the index t is addressed by the microcontroller 205 to the specific component 210 (step 412). Again, it may be a request compliant with the SPI standard.

After receiving an interrogation request, the specific component 210 modulates the carrier transmitted by the antenna of the tag reader to encode the interrogation command (step 414).

A variable n representing a loop index among all the loops forming the lines, considering that the device represented in FIG. 2 comprises N loops forming the lines, is initialized to the value 1 (step 416). A test is then performed to determine if the value of the index n is less than or equal to the variable N (step 418).

If the value of the index n is less than or equal to the variable N, the microcontroller controls the multiplexers 230-1 and 230-2 to connect one terminal of the loop n to the ground and the other terminal of this loop to the filtering and adaptation unit 245 (step 420).

According to the embodiment implemented, the amplitude of the component corresponding to the carrier of the received signal (signal SE) and / or the amplitude of the useful component (used to exchange data) of the received signal (signal SR) are transmitted to the microcontroller 205 where they are converted (analog-to-digital conversion) and then stored in an SL () array (step 422).

The variable n is then incremented by one (step 424) and the algorithm continues in step 418.

If the value of the index n is greater than the variable N, a variable p representing a loop index of all the loops forming the columns, considering that the device represented in FIG. 2 comprises P loops forming the columns, is initialized. at value 1 (step 426).

A test is then performed to determine if the value of the index p is less than or equal to the variable P (step 428).

If the value of the index p is less than or equal to the variable P, the microcontroller controls the multiplexers 230-1 and 230-2 to connect one terminal of the loop p to ground and the other terminal of this loop to the filtering and adaptation unit 245 (step 430).

According to the embodiment implemented, the amplitude of the component corresponding to the carrier of the received signal (signal SE) and / or the amplitude of the useful component (used to exchange data) of the received signal (signal SR) are transmitted to the microcontroller 205 where they are converted (analog-to-digital conversion) and then stored in an SC () array (step 432). The variable p is then incremented by one (step 434) and the algorithm continues in step 428. On the contrary, if the value of the index p is greater than the variable P, the abscissa of the tag t, denoted x (t), in a reference linked to the detection surface, is calculated from the values stored in the SC () array (step 436) and the ordinate of the tag t, denoted y (t), in this same frame, is calculated from the values stored in the SLQ array. The values x (t) and y (t) are stored in the table P ().

The index f is then incremented by one (step 440) and the algorithm continues in step 408.

It should be noted that if, for the sake of clarity, the loops are addressed one by one by a single filtering and matching unit 245, it is possible to use several filtering and adaptation units to perform measurements. in a parallel way. Thus, for example, it is possible to use two filtering and matching units, one receiving a signal from one of the loops forming the lines and the other from one of the loops forming the columns. .

As indicated above, the fact of positioning a tag close to the loops used locally detunes the inductive coupling of the loops.

According to a first embodiment, a measurement of the amplitude of the component corresponding to the carrier of the received signal (signal SE) is carried out for each loop.

Advantageously, to avoid a measurement of the signals at the terminals of each loop, the determination of the position of a tag comprises two phases, a so-called 'search' phase and a so-called 'tracking' phase. For the sake of clarity, these two phases are not illustrated in Figure 4 where only a measurement is performed systematically on all loops for each identified tag.

In the 'search' phase, the tag whose position is to be estimated is located approximately, i.e., for example, within one or two loops. This first location is performed by sampling the power of the signal SE from one loop out of two or one loop out of three (among the set of loops). Indeed, the measured signal has a minimum local for rows and a local minimum for columns near the tag whose position is to be estimated.

In the 'tracking' phase, the amplitude of the received signal is measured only for the three or five adjacent loops centered on each of the two loops defining the rows and columns which presented a local minimum for the signal SE.

This measurement cycle is repeated quickly enough that between two series of measurements, the position of the local minimum is always in the central position or offset by a loop at most. The group of three or five measured loops is dynamically chosen to refocus the local minimum. An extrapolation of the tag movement based on the evolution of the tag position during the previous cycles makes it possible to better localize the local minimum to the current cycle.

In this embodiment, this magnitude can be measured by measuring the peak-to-peak value of the carrier (typically 13.56Mhz) using the SE output of the filtering and matching unit 245.

The three or five values obtained allow, by interpolation, to estimate the position of the tag 255.

FIG. 5, comprising FIGS. 5a and 5b, illustrates the measurement of the amplitude of the component corresponding to the carrier of the signal received at the terminals of a given loop.

FIG. 5a represents a carrier, here a carrier having a frequency of 13.56 MHz, retro-modulated by a tag whose position is to be estimated. The slots 500 correspond to the useful component of the signal, that is to say to the bit stream of the response of the tag. By way of illustration, the level of such a signal may be 6V peak-to-peak for the carrier.

FIG. 5b illustrates the value of the signal SE (505) at the output of the filtering and matching unit 245, obtained for the signal illustrated in FIG. 5a. As illustrated, this value corresponds to the difference between the extreme values of the retro-modulated carrier, that is to say the largest amplitude over a given time interval. FIG. 6 illustrates a simplified example of configuration of loops used to estimate the abscissa of the position of a tag in a device such as that described with reference to FIG. 2.

As illustrated, the three loops 225'-i, 225'-j and 225'-k, preferably adjacent, forming columns here, are nested so that there is overlap. However, they are isolated from each other (i.e. there is no electrical contact between these loops).

It is observed that if the loops represented seem of different sizes (for the clarity of the presentation), they are in fact, here, of equal or substantially equal sizes.

These loops are used here to estimate the abscissa of the position of the tag 255 placed above these loops, it being observed that the more the tag whose position is to be estimated is at the center of a loop, the more it disables the coupling between the antenna of the tag reader and this loop. Therefore, the more the tag whose position is to be estimated is at the center of a loop, the lower the value measured in the amplitude loop of the back-modulated carrier.

Conversely, the more the tag whose position is to be estimated is at the edge of a loop, the less it disables the coupling between the antenna of the tag reader and this loop. Thus, the larger the tag whose position is to be estimated is at the edge of a loop, the larger the value measured in the amplitude loop of the back-modulated carrier.

Measuring the amplitude of the retro-modulated carrier (signal SE) in the loops 225'-i, 225'-j and 225'-k gives here the values Si, Sj and Sk, respectively. Therefore, given the relative position of the tag 255 with respect to the loops 225'-i, 225'-j and 225'-k, the values of the measurements obtained are ordered as follows: Sk> Si> Sj.

Locally, the variation of the amplitude of the retro-modulated carrier with respect to the distance between the loop used and the tag can be approximated by a parabola (polynomial of order 2). Thus, knowing the values Si, Sj and Sk, it is possible to deduce the extremum of the parabola representing locally the amplitude of the retro-modulated carrier and, therefore, the abscissa of the position of the tag.

FIG. 7 illustrates the theoretical variation 700 of the amplitude of the retro-modulated carrier of a signal received as a function of the relative positions of the loop used (theoretically) and of the tag as well as the local approximation of the variation of the this amplitude by a parabola, from measurements made using several loops, to deduce the position of a tag.

As illustrated, the values Si, Sj and Sk measured in the loops 225'-i, 225'-j and 225'-k, correspond to the positions x (i), x (j) and x (k), respectively. The local approximation of the amplitude of the retro-modulated carrier by a second-order polynomial leads here to the parabola 705. The extremum of the latter makes it possible to estimate the abscissa of the position of the tag x (t). .

The interpolation presented here to estimate the abscissa of the position of a tag is advantageously used to estimate its ordinate. In addition, if it is possible to interpolate the abscissa and the ordinate of the position of a tag from three measurements made by loops forming columns and three loops forming lines, it is possible to use more loops, for example five loops forming columns and five loops forming lines. The number of loops used for the interpolation of the abscissa may be different from the number of loops used for the interpolation of the ordinate.

It is observed that the position of the loops can be regular (the distance between two adjacent loops is constant) or not.

According to a second embodiment, a measurement of the amplitude of the useful component (used to exchange data) of a received signal (SR signal) is performed for each loop to determine the position of a tag.

It is noted here that the level of the SR signal measured in a loop is maximum when the tag is centered on this loop. Indeed, the surface ratio between the tag and this loop (located at least partly under the tag) is such that the loop is more sensitive to retro-modulation when the tag is centered on this loop. Conversely, the further away the tag is from the loop, the lower the measured level of the retro-modulated signal. Thus, in other words, if the amplitude of the component corresponding to the carrier of the received signal increases with the distance (due to the coupling adaptation), the amplitude of the useful component (used to exchange data ) of the received signal decreases with the distance (due to the power drop).

Once again, the determination of the position of a tag preferably comprises two phases, a 'search' phase and a 'tracking' phase. As indicated above, these two phases are not illustrated in FIG. 4 where, for the sake of clarity, only one measurement is performed systematically on all the loops for each identified tag.

In the 'search' phase, the tag whose position is to be estimated is located approximately, i.e., for example, within one or two loops. This first location is performed by sampling the signal SR from one loop out of two or one loop out of three (among the set of loops). Indeed, the measured signal (SR signal) has a local maximum for the lines and a local maximum for the columns located near the tag whose position must be estimated.

In the tracking phase, the amplitude of the useful component of the received signal is measured only for the three or five adjacent loops centered on each of the two loops defining the rows and columns which presented a local maximum for the SR signal.

This measurement cycle is repeated quickly enough that between two series of measurements, the position of the local maximum is always in the central position or offset by a loop at most. The group of three or five measured loops is dynamically chosen to refocus the local maximum. An extrapolation of the tag movement based on the evolution of the tag position during the previous cycles allows to better localize the local maximum to the current cycle.

In this embodiment, the amplitude of the useful component of the received signal can be measured as follows: the filtering and matching unit 245 demodulates the retro-modulated signal and then amplifies it and the filter to provide the SR signal, as previously described. The three or five values obtained from adjacent loops allow, by interpolation, to estimate the abscissa or the ordinate of the position of the tag 255 (these operations are performed independently for the abscissa and the ordinate using loops defining columns and loops defining lines).

This embodiment makes it possible to locate the interrogated current tag while avoiding constraints such as the presence of unwanted metal objects on the detection surface.

FIG. 8, comprising FIGS. 8a, 8b and 8c, illustrates the measurement of the average amplitude of the useful component (used to exchange data) of a received signal.

FIG. 8a represents a carrier, here a carrier having a frequency of 13.56 MHz, retro-modulated by a tag whose position is to be estimated. The slots 800 correspond to the useful component of the received signal, that is to say to the bit stream of the response of the tag. By way of illustration, the level of such a signal may be 6V peak-to-peak for the carrier. The signal shown in Figure 8a is identical to the signal shown in Figure 5a.

FIG. 8b illustrates the useful component (ie used to transmit data) of the retro-modulated signal, ie the tag response bit stream, whose signal value SR (800), obtained at the output of FIG. the filtering and matching unit 245, for the signal illustrated in FIG. 8a, represents the amplitude. The amplitude of such a signal is typically a few millivolts.

To improve the accuracy of the measured values, the signal SR does not represent a measured amplitude of the useful component of the retro-modulated signal but an average value obtained by integration, as previously described with reference to FIG. 3 (it is recalled that the distribution high states being substantially equal to that of low states, the integration of the retro-modulated signal is representative of its average amplitude).

Thus, a gain, for example a gain equal to 20, is applied to the signal shown in FIG. 8b. The result is filtered in a bandpass filter and then made positive as illustrated in FIG. 8c (its amplitude can then be between 0 and 3 volts). The result is then integrated to determine a mean value representative of the amplitude of the useful component of the retro-modulated signal (SR signal).

The configuration of the loops used to carry out measurements of the retro-modulated signal (average amplitude of the useful component) and to deduce the position of a tag is similar to that described in the first embodiment, with reference to FIG. 6.

However, if the configuration of the loops is identical or similar, it is recalled here that the more the tag whose position must be estimated is in the center of a loop, the higher the amplitude of the useful component of the signal received in this loop is high .

Conversely, the more the tag whose position is to be estimated is remote from the center of a loop, the lower the amplitude of the useful component of the signal received in this loop.

The measurement of the amplitude of the useful component of the received signal (signal SR) in the loops 225'-1, 225'-j and 225'-k gives the values Si, Sj and Sk, respectively. Consequently, given the relative position of the tag 255 with respect to the loops 225'-i, 225'-j and 225'-k, the values of the measurements obtained are ordered as follows: Sj> Si> Sk.

Locally, the amplitude of the useful component of the retro-modulated signal can be approximated by a parabola (polynomial of order 2). Thus, knowing the values Si, S and Sk, it is possible to deduce the extremum of the parabola locally representing the amplitude of the useful component of the retro-modulated signal. The position of this extremum corresponds to the abscissa of the position of the tag.

FIG. 9 illustrates the theoretical variation 900 of the amplitude of the useful component of a retro-modulated signal as a function of the relative positions of the loop used (theoretically) and of the tag as well as the local approximation of the variation of this amplitude by a parabola, from measurements made using several loops, to deduce the position of a tag.

As illustrated, the values Si, Sj and Sk measured in the loops

225'-i, 225'-j and 225'-k, correspond to the positions x (i), x (j) and x (k), respectively. The local approximation of the amplitude of the useful component of signal retro-modulated by a polynomial of order 2 leads here to the parabola 905. The extremum of the latter makes it possible to estimate the abscissa of the position of the tag x (t).

Again, the position of the loops can be regular (the distance between two adjacent loops is constant) or not.

To improve the reception sensitivity of the loops used, it is possible to replace each of them by a double loop.

FIG. 10, comprising FIGS. 10a and 10b, illustrates an example of mounting of double loops used for measuring response signals of a tag and determining its position.

Figure 10a schematically shows the mounting of a double loop while Figure 10b shows a sectional view of the device 200 in which are integrated double loops.

As illustrated, each loop 225-j of the device 200 is replaced by two loops 225a-j and 225b-j located on either side of the antenna 215 of the tag reader. Each of these loops is nested with adjacent loops (e.g. loops 225a-i and 225a-k for loop 225a-j and loops 225b-i and 225b-k for loop 225b-j) as previously described.

The two terminals of each of the loops 225a-j and 225b-j are connected to an impedance adapter 235a-j and 235b-j, respectively, the output of which is connected to the same signal attenuator 240-j whose outputs are connected to multiplexers 230-1 and 230-2 as previously described. Moreover, one of the terminals of one of the loops 225a-j and 225b-j and connected to the equivalent terminal of the other of the loops 225a-j and 225b-j, as illustrated. Each of the loops 225a-j and 225b-j is tuned to the carrier frequency transmitted by the tag reader (typically 13.56 MHz) using the impedance adapters 235a-j and 235b-j.

Such an arrangement makes it possible to increase the sensitivity of the device: the output of the double loop corresponds to the difference of the signals received by each of the loops of the double loop, which makes it possible to eliminate a substantial part of the carrier.

When a tag transmits a retro-modulation signal above this double loop, each loop of the latter receives a retro-modulation signal with a different level (due to the stacking of the loops). Consequently, the difference of the signals received by these loops makes it possible to receive the retro-modulation signal with less noise.

FIG. 11 illustrates an exemplary device for locating different types of tags according to one embodiment of the invention.

The device 200 "here comprises the elements 205", 210 ", 215", 220 ", 225" -1, 225 "-1, 225" -k, 230 "-1, 230" -2, 235 "-1, 235 "-245" -k, 240 "-i, 240" -248 "-k, 245" and 250 "which are similar to elements 205, 210, 215, 220, 225-i, 225-j , 225-k, 230-1, 230-2, 235-i, 235-d, 235-k, 240-i, 240-d, 240-k, 245 and 250 described with reference to Fig. 2, respectively. The device 200 "further comprises other loops forming columns and loops forming lines (not shown).

The device 200 "also comprises two multiplexers 1 100-1 and 1 100-2 As illustrated, the terminals of the vertical loops represented are connected to the multiplexers 1 100-1 and 1 100-2 and to the multiplexers 230" -1 and 230 " - 2.

Thus, for example, one of the terminals of the loop 225 "-i is connected to the multiplexer 1 100-1 while the other terminal of the loop 225" -i is connected to the multiplexer 1 100-2. The terminals of the loops 225 "-j and 225" -k are connected similarly to the multiplexers 1100-1 and 1100-2.

The other loops not shown are connected in a manner similar to the multiplexers 1 100-1 and 1 100-2. The multiplexers 1 100-1 and 1 100-2, as the multiplexers 230 "-1 and 230" -2 are controlled by the microcontroller 205 ".

As illustrated, the outputs of the multiplexers 1 100-1 and 1 100-2 are connected to the element 1 105 whose output is itself connected to the microcontroller 205 ".

The position of a tag is determined using the signals from the multiplexers 230 "-1 and 230" -2 as previously described or, alternatively, using the signals from the multiplexers 1 100-1 and 1 100-2.

The signals coming from the multiplexers 1100-1 and 1100-2 are processed in the element 1 105. It may be, for example, a set of components enabling the implementation of a positioning system such as than that described in patent application FR1255334. The element 1 105 then typically comprises a bandpass filter, an automatic gain controller and a demodulator.

Thus, the device 200 "can, using the 230" -1 multiplexers and

230 "-2, determine the position of standard type tags, for example the position of the tag 255, and, using the multiplexers 1 100-1 and 1 100-2, determine the position of tags of a particular type, in particular the position of the tag 1 1 10, for example tags such as those described in the patent application FR1255334.

Naturally, to meet specific needs, a person skilled in the field of the invention may apply modifications in the foregoing description.

In particular, there are mobile phones equipped with NFC means including smartphones, able to activate an NFC tag function so that the phone behaves like a mobile element with an NFC tag (eg Samsung Galaxy S II, Samsung Galaxy Nexus, Samsung , Galaxy and Nexus are trademarks). However, as described above, the method according to the invention applies to any mobile element provided with a tag using a near-field communication technology, and therefore also to the phones on which such a tag function can be activated.

Claims

Device (200) for locating at least one mobile element provided with at least one tag (255) using a near-field communication technology and comprising a unique identifier, this device being characterized in that it comprises the following means ,

transmitting means (215) for transmitting an interrogation signal of said at least one tag;

control means (205, 245);

a plurality of reception means (225) selectively connected to said control means, said reception means being receptive to said interrogation signal and to a response signal of said at least one tag;

2. Device according to claim 1 further comprising switching means (230) controlled by said control means for sequentially selecting said receiving means.

3. Device according to claim 1 or claim 2 further comprising adaptation means (235) for tuning said receiving means to the frequency of a carrier of a signal transmitted by said transmitting means.

4. Device according to any one of claims 1 to 3 further comprising a specific component (210) connected to said control means and said transmitting means for performing specific functions of reading tags.

5. Device according to any one of claims 1 to 4 wherein said control means comprises means for determining a value representative of the amplitude of a component corresponding to a carrier of a signal received via said receiving means.

6. Device according to any one of claims 1 to 5 wherein said control means comprises means for determining a value representative of the amplitude of a useful component of a signal received via said receiving means, used to exchange Datas.

7. Device according to any one of claims 1 to 6 wherein said receiving means comprises at least one set of loops extending in at least one dimension of a surface on which must be estimated the position of said at least one tag .

8. Device according to any one of claims 1 to 7 wherein each of said receiving means comprises two parts, each of said two parts being located on either side of said transmitting means.

9. Device according to any one of claims 1 to 8 wherein said transmitting means and said control means are configured to read at least one data stored in said at least one tag or write at least one data in said at least one a tag.

10. Device according to any one of claims 1 to 9 further comprising selection means (1 100-1 and 1 100-2) and processing means (1 105) selectively connected to said receiving means and said means for control, said selection means, said processing means and said control means being configured to determine the position of at least one tag implementing a communication technology distinct from the near-field communication technology.

11. Method for locating at least one mobile element provided with at least one tag (255) using a field communication technology close and comprising a unique identifier, the method being implemented in a device comprising transmission means (215) for transmitting at least one interrogation signal of at least one tag, control means (205, 245) and a plurality of receiving means (225) selectively connected to said control means and receptive to signals transmitted by said transmitting means and by at least one tag, the method being characterized in that it comprises the following steps,

- Transmitting command (412) of an interrogation signal of said at least one tag;

sequential selection (420, 430) of reception means and measurement of at least one signal received via said selected reception means, said received signal resulting from at least one signal transmitted by said transmission means and a signal transmitted by at least one tag in response to said signal transmitted by said transmitting means; and

estimating (422, 432) the position of said at least one tag by interpolating signal measurements received via selected receiving means.

12. A locating method according to claim 11 comprising a first step of estimating an approximate position of said at least one tag and a second step of estimating the position of said at least one tag, said second step of estimating the position comprising said steps of controlling transmission of an interrogation signal, sequential selection of reception means and measurement of at least one signal received via said selected reception means and estimation of said position at said least one tag by interpolation of signal measurements received via selected reception means.

13. A method of locating according to claim 1 2 wherein said first step of estimating a position comprises a step of measuring the amplitude of a component corresponding to a carrier of a signal received via said receiving means and / or the amplitude of a useful component of a signal received via said receiving means, used to exchange data.

14. The locating method according to any one of claims 1 1 to 13 comprising an initial step of obtaining a number of identified tags and identifiers identified tags.

15. The locating method as claimed in claim 14, wherein said steps for controlling transmission of an interrogation signal, sequential selection of means for receiving and measuring at least one signal received via said selected reception means, and estimation of the position of said at least one tag by interpolation of signal measurements received via selected reception means are performed for each tag identified.

16. The method of locating according to any one of claims 1 1 to 15 wherein said step of measuring at least one received signal comprises a step of measuring the amplitude of a component corresponding to a carrier of a signal. received via said receiving means and / or the amplitude of a useful component of a signal received via said receiving means, used to exchange data.

17. A method of locating according to any one of claims 1 1 to 16 further comprising a step of reading at least one data stored in said at least one tag or writing at least one data in said at least one a tag.

18. Computer program comprising instructions adapted to the implementation of each of the steps of the method according to any one of claims 1 1 to 17 when said program is run on a microcontroller.