Patent Publication Number: US-2022239335-A1

Title: Nfc device postion finder

Description:
BACKGROUND 
     Technical Field 
     The present disclosure generally relates to electronic circuits, and more specifically to electromagnetic transponders or electronic tags. The present description in particular applies to electronic devices incorporating a near-field communication (NFC) circuit, more commonly called NFC devices, and the detection of the presence of such a device in the field of another device. 
     Description of the Related Art 
     Electromagnetic transponder communication systems are increasingly common, in particular, since the development of near-field communication technologies. These systems typically use a radiofrequency electromagnetic field generated by an NFC device (terminal or reader) to be coupled (for example be detected, and then communicate) with another NFC device (card) located within range. More precisely, the radiofrequency electromagnetic fields are generated and/or detected by the antennas of the NFC devices. The antenna position in NFC devices is not standardized, so the NFC antenna position may vary in devices of the same type of product (for example in mobile phone or smartphone). As the coupling factor between the devices depends on the respective positions of the antennas, it is desirable to obtain information about these respective positions. 
     The radiofrequency electromagnetic field generated by an NFC device allows the detection, and then the communication, with another NFC device if their respective antennas are close enough to each other. Detection distances are usually less than 10 cm, and in some cases less than 4 cm, which increase the importance of being able to identify the respective positions between two paired devices. 
     BRIEF SUMMARY 
     There is a need to improve NFC device coupling. 
     In particular, there is a need to improve the speed of reaching an acceptable or optimum coupling between two NFC devices. 
     One or more embodiments of the present disclosure addresses all or some of the drawbacks of the known methods and circuits for detecting the presence of an NFC device by another NFC device emitting an electromagnetic field. 
     One embodiment provides a method, implemented by a first NFC device configured in reader mode, comprising: 
     a step of evaluating an information about the coupling between the first NFC device and a second NFC device configured in card mode, as a function of the position of an antenna of the first NFC device with respect to an antenna of the second NFC device; and a step of indicating said information by means of a user interface of the first device. 
     One embodiment provides a system comprising a first NFC device configured in reader mode and a second NFC device configured in card mode, the first NFC device being adapted to implement the method as described. 
     According to an embodiment, said indication of the information representative of the coupling is a visual indication. 
     According to an embodiment, said indication of the information representative of the coupling is an audible indication. 
     According to an embodiment, said evaluation step comprises a measurement step, by the first NFC device, of RSSI values from the second NFC device, according to the relative position of the first NFC device antenna with respect to the second NFC device antenna. 
     According to an embodiment, the method or he system further comprising a comparison step of the measured RSSI values with a target value. 
     According to an embodiment, the target value is stored in an internal memory of the first NFC device. 
     According to an embodiment, the target value is stored in a remote server. 
     According to an embodiment, the indication step comprises a mapping of said information representative of the coupling, based on a distribution of the RSSI values in, at least, three ranges of values. 
     According to an embodiment, a color is affected to each range of value. 
     According to an embodiment, a sound is affected to each range of value. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing features and advantages, as well as others, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which: 
         FIG. 1  shows, very schematically and in block diagram form, an exemplary near field communication system, of the type to which, as an example, the described embodiments and modes of implementation apply; 
         FIG. 2  shows, schematically and in block diagram form, an embodiment of a near field communication system; 
         FIG. 3  is a graph showing the evolution of the RSSI value according to the position of an NFC device, of the system illustrated in  FIG. 2 , along an axis X; 
         FIG. 4  is a graph showing the evolution of the RSSI value according to the position of an NFC device, of the system illustrated in  FIG. 2 , along an axis Y; 
         FIG. 5  shows, schematically, an example of the embodiment of a near field communication system described in  FIG. 2 ; 
         FIG. 6  shows, in the form of block diagrams, a method for implementing the system illustrated in  FIG. 2 ; and 
         FIG. 7  shows, in the form of block diagrams, another method for implementing the system illustrated in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Like features have been designated by like references in the various figures. In particular, the structural and/or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties. 
     For the sake of clarity, only the operations and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail. In particular, the generation of the radiofrequency signals and their interpretation have not been described in detail, the described embodiments and modes of implementation being compatible with the standard techniques for generating and interpreting these signals. 
     Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements. 
     In the following disclosure, unless indicated otherwise, when reference is made to absolute positional qualifiers, such as the terms “front”, “back”, “top”, “bottom”, “left”, “right”, etc., or to relative positional qualifiers, such as the terms “above”, “below”, “higher”, “lower”, etc., or to qualifiers of orientation, such as “horizontal”, “vertical”, etc., reference is made to the orientation shown in the figures. 
     Unless specified otherwise, the expressions “around”, “approximately”, “substantially” and “in the order of” signify within 10%, and preferably within 5%. 
       FIG. 1  shows, very schematically and in block diagram form, an exemplary near field communication system, of the type to which, as an example, the described embodiments and modes of implementation apply. 
     The case is arbitrarily considered of two electronic devices, for example a mobile phone and another electronic device, but what is described applies more generally to any system in which a reader, terminal or device radiates an electromagnetic field able to be detected by a device operating as transponder. To simplify, reference will be made to NFC devices in order to designate electronic devices incorporating one or several near-field communication (NFC) circuits. 
     In the illustrated example, a first NFC device  100 A (DEV 1 ) is able to communicate, by near-field electromagnetic coupling, with a second NFC device  100 B (DEV 2 ). Depending on the applications, for a communication, one of the NFC devices  100 A,  100 B operates in so-called reader mode, while the other NFC device  100 B,  100 A operates in so-called card mode, or both NFC devices  100 A,  100 B communicate in peer-to-peer (P 2 P) mode. The device operated in a card mode can comprise a passive tag. 
     Each NFC device  100 A,  100 B incorporates a near-field communication circuit symbolized, in  FIG. 1 , by a block  102 A,  102 B. The near-field communication circuits  102 A and  102 B each have various elements or electronic circuits for generating or detecting a radiofrequency signal using respective antennas  104 A,  104 B, for example modulation or demodulation circuits. During a communication between the NFC devices  100 A and  100 B, the radiofrequency signal generated by one of the NFC devices  100 A,  100 B is detected by the other NFC device  100 B,  100 A located within range. 
     It is arbitrarily considered, as illustrated in  FIG. 1 , that the first NFC device  100 A emits an electromagnetic field (EMF) in order to initiate a communication with the second NFC device  100 B. The field EMF is detected by the second NFC device  100 B once it is within range. A coupling is then formed between the respective oscillating circuits of the first NFC device  100 A and the second NFC device  100 B. This coupling is reflected by a variation of the charge made up of the circuits of the NFC device  100 B on the oscillating circuit for generating the field EMF of the NFC device  100 A. 
     In practice, for a communication, a corresponding phase or amplitude variation of the transmitted field is detected by the device  100 A, which then begins an NFC communication protocol with the device  100 B. On the NFC device  100 A side, in practice it is detected whether the amplitude of the voltage across the terminals of the oscillating circuit and/or the phase shift relative to the signal generated by the circuit  102 A differ from the amplitude and/or phase ranges (or windows) each delimited by first and second thresholds. For example, the first threshold is below the second threshold. Reference will be made hereinafter to lower and upper thresholds. 
     The range of a radiofrequency signal is, usually, lower than 10 cm and can be, for example, lower than 4 cm. As the coupling factor between the devices depends on the respective positions of the antennas, theses low values make the NFC optimal coupling determination between two NFC devices, sometimes difficult in order to generate a communication. If an optimal coupling between both devices isn&#39;t found, the communication will then be impacted, such as its speed which will be reduced or errors will break the communication. 
     In order to respect speed constraints of the near-field communication and due to the fact that at least one of the devices moves during the communication, it is important that the coupling factor between two NFC devices remains sufficient and thus that the respective positions of two paired devices is acceptable. When the coupling factor between two devices is too low, the communication can be lost. 
     A solution could be to print on the surface of each device an identifier of the location of the antenna. However, such solution is not always acceptable by the manufacturers in view of the shape, the aesthetic, the size, etc., of the device. 
     The present disclosure provides, in order to solve this problem, mapping of the coupling factor between a device in card mode and a device in reader mode, according to the relative position of the devices. For example, the present disclosure provides mapping of the coupling factor when the surface of the device in card mode is scanned with the device in reader mode. The mapping of the coupling factor according to the relative position of the devices is, for example, a visual or an audible mapping. 
     Information representative of the coupling factor is, for example, displayed, through a color code, on a screen of the reader mode device. For example, a red area in the screen corresponds to a high coupling factor while a green area in the screen corresponds to a low coupling factor. 
     When a user wants to couple his mobile phone with an NFC device, he can then easily find the correct position of his mobile phone with respect to the NFC device in order to have an optimal coupling factor. He is thus able to maintain this position during all the communication steps. 
       FIG. 2  shows, schematically and in block diagram form, an embodiment of a near field communication system. 
     The system includes an NFC device  200 A and an NFC device  200 B. According to the present description, the NFC devices  200 A operates in reader mode, while the other NFC device  200 B operates in card mode. The NFC device  200 A is, for example, a mobile phone or a smartphone. The device  200 B is, for example, another mobile phone, a wireless speaker, a pair of earbuds, a television, a laptop, a car, a coffee machine, any electronic device or any other NFC device. 
     The system of  FIG. 2  provides the determination of the relative position of the device  200 A with respect to the device  200 B in which the coupling factor is the highest. In  FIG. 2 , the device  200 A is represented three times of which two times are in dotted lines and one time is in solid lines aligned with the device  200 B. 
     The dotted line representations of the device  200 A correspond to two possible intermediate positions of the device  200 A in the orthogonal system during the process of determining the relative position of the device  200 A with respect to the device  200 B. The solid line representation of the device  200 A corresponds to the position of the device  200 A at the end of the process. 
     Each NFC device  200 A,  200 B incorporates a near-field communication circuit symbolized, in  FIG. 2 , by a block  202 A,  202 B and an antenna symbolized, in  FIG. 2 , by a block  204 A,  204 B. One of the antennas can be passive. 
     In  FIG. 2 , the device  200 A is scanning the surface of the device  200 B in a three- dimensional orthogonal system. The three-dimensional orthogonal system comprises an axis X that corresponds to the horizontal axis going through the center of the antenna  204 B, an axis Y that corresponds to the vertical axis going through the center of the antenna  204 B, and an axis Z orthogonal to the axis X and Y. 
     During this scanning step, the device  200 A detects, through its antenna  204 A, and evaluates, during an evaluation step, the strength of the load modulation (active or passive) sent by the device  200 B according to the position of the device  200 A. The received signal strength indication value or RSSI value provides information about the coupling factor. The RSSI value is maximal at the optimal coupling. 
     In practice, optimal coupling is not always obtained when both antennas  204 A and  204 B are geometrically aligned. Indeed, the integrated circuit and more generally the conductor parts (enclosures, shields, printed circuit boards) of the devices  200 A and  200 B located around the antennas  204 A and  204 B can modify the coupling factor. 
     The evolution of the coupling factor with respect to the axis X and the axis Y is described in relation with  FIGS. 3 and 4 . 
       FIG. 3  is a graph showing the evolution of the RSSI value according to the position of the device  200 B along the axis X. 
       FIG. 4  is a graph showing the evolution of the RSSI value according to the position of the device  200 B along the axis Y. 
     The graphs illustrated in  FIGS. 3 and 4  were obtained by scanning, as described in  FIG. 2 , the surface of the device  200 B with the device  200 A respectively along axes X and Y. 
     These graphs are based on devices containing planar antennas but those skilled in the art can easily adapt the description of  FIGS. 3 and 4  to other antenna shapes. Moreover, these graphs are based on the shapes of the devices  200 A and  200 B shown in  FIG. 2 . Indeed, these graphs are based on devices wherein the antenna of each device is not aligned with the geometric center of the device. More precisely, in this example, the antenna of each device is horizontally, but not vertically aligned with the center of the device. Such a misalignment leads to the fact that the antenna efficiency is impaired due to conductive part located around the antennas. 
     The evolution of the RSSI value, according to the position of the device  200 A along the axis X ( FIG. 3 ), is approximately symmetric with respect to a position corresponding to the geometric alignment of both antennas  204 A and  204 B. Furthermore, the highest value of RSSI and therefore the optimal coupling factor are obtained along the axis X at the position when both antennas  204 A and  204 B are geometrically aligned. 
     The evolution of the RSSI value, according to the position of the device  200 A along the axis Y, is not symmetric due to the conductive part located around the antennas with impair their efficiencies. Furthermore, the highest value of RSSI and therefore the optimal coupling factor are obtained along the axis Y when the center of the antenna  204 A is lowly shifted down of the center of the antenna  204 B. 
     The following graphs were, for example, obtained for an antenna  204 B having a length along the X axis of 40 mm and a width along the Y axis of 22 mm. 
       FIG. 5  shows, schematically, an example of the embodiment of a near field communication system described in  FIG. 2 . 
     The example of  FIG. 5  is based on the optimal coupling search between a reader mode smartphone  500 A and a card mode wireless speaker  500 B. 
     In  FIG. 5 , the user is scanning the surface of the device  500 B with the smartphone  500 A in order to localize the position of the smartphone  500 A leading to the optimal coupling factor in order to generate a communication. The movement of the scan can be evaluated thanks to existing sensors embedded into the smartphone  500 A such as an accelerometer and/or a LiDAR sensor and/or a camera in order to determine the position of the measurement relative to the device  500 B. 
     During the scanning step, the smartphone  500 A measures the RSSI. The smartphone  500 A generates, thanks to a dedicated application/program, a mapping of the RSSI values. This mapping is then provided to the user via a user interface, for example, a visual or audible interface. 
     According to the embodiment shown in  FIG. 5 , the mapping is a visual mapping. 
     For example, the mapping, displayed on a screen of the smartphone, corresponds to a colored map in which each color is associated with a range of RSSI values. For example, in the colored map: 
     positions of the smartphone  500 A where the RSSI value is higher than 50 dB are represented in red; 
     positions of the smartphone  500 A where the RSSI value is comprised between 40 dB and 50 dB are represented in yellow; 
     positions of the smartphone  500 A where the RSSI value is comprised between 30 dB and 40 dB are represented in green; and positions of the smartphone  500 A where the RSSI value is less than 30 dB are represented in blue. 
     According to another example, the mapping corresponds to a grey scale representation in which each grey level is associated with a range of RSSI values. 
     According to another embodiment, the mapping is an audible mapping. For example, a sound is emitted with a frequency depending on the RSSI value, preferably with a high frequency when the RSSI value is high and with a low frequency when the RSSI value is low. According to another example, a sound with the same tone is repeated at a different frequency depending on the RSSI value. The audible mapping can also be based on the volume of a sound. 
     According to another embodiment, the mapping is based on the vibration frequency of the smartphone  500 A. For example, the vibration frequency of the smartphone is high when the smartphone  500 A detects a high RSSI value and the vibration frequency of the smartphone is low when the smartphone  500 A detects a low RSSI value. 
     The example shown in  FIG. 5  is based on a coupling between a smartphone and a wireless speaker. However, it also applies to a coupling between a smartphone and another mobile phone, a pair of earbuds, a television, a laptop, a car, a coffee machine, any electronic device or any other NFC device. 
       FIG. 6  shows, in the form of block diagrams, a method for implementing the system illustrated in  FIG. 2 . 
     The method illustrated in  FIG. 6  allows the determination of the optimal coupling factor between the device  200 A ( FIG. 2 ) and the device  200 B ( FIG. 2 ). The method illustrated in  FIG. 6  also allows the record of the RSSI measurements. 
     A first step  601  (Initialization) consists in the initialization of the searching of the optimal coupling between both devices  200 A and  200 B ( FIG. 2 ). During step  601 , the user can, for example, start the device  200 A or start the dedicated application on device  200 A. During step  601 , the user can also bring the device  200 A close to the device  200 B in order to detect the device  200 B. 
     The step  601  is followed by the scanning step  603  corresponding to the scanning step disclosed in relation with  FIGS. 2 to 5 . 
     The step  603  consists in making, in a loop, successive RSSI measurements as long as a movement of the device  200 A is detected or until the end of a preset time. During the scanning step  603 , the device  200 A creates, via its user interface, a mapping of the RSSI measurements according to its position. 
     The step  603 , comprises two sub-steps consisting in the RSSI measurement (block  603 A, Measure RSSI) and a movement of the device  200 A (block  603 B, User moves the phone). The RSSI measurement is periodic depending on parameters of device  200 A. Each measurement corresponds to a position of the device. 
     When the RSSI is measured, information about its value is returned to the user via the user interface. If the user sees that the position indicated by the measure interface does not correspond to an optimal position, he can continue move the device  200 A with respect to the device  200 B in order to reach a better position. Another measure of the RSSI is then made at the new position. 
     These sub-steps are repeated until no more movement is detected or until the preset time ends (block  605 , Timer elapsed or no more movement). 
     For example, the expression “no more movement” refers to a speed limit below which the system considers that the user is no longer moving the device  200 A. 
     The preset time is, for example, determined by the user through the user interface of the device  200 A. As an alternative, the preset time is determined by the manufacturer(s) of the devices  200 A and  200 B. The preset time depends, for example, on the type and/or size of the device  200 B. 
     The step  605  is followed by a step  607  (Stored measurement results) in which the measurement results or RSSI measurements are recorded or stored. 
     The RSSI measurements are, for example, stored in the internal memory of the device  200 A and/or in a remote server, for example, an Internet server, such as the cloud (block  609 , Update on the cloud). 
     The recorded measurements are, for example, classified, in at least one of the memories cited above, by type and model of the device  200 B. In other words, the RSSI measurements of the coupling between a smartphone and a model A of wireless speaker are associated together, while the RSSI measurements of the coupling between a smartphone and a model B of wireless speaker are separately associated together. 
     This allows to retrieve the optimal coupling based on previous measurements with the same association of devices. 
       FIG. 7  shows, in the form of block diagrams, another method for implementing the system illustrated in  FIG. 2 . 
     The method illustrated in  FIG. 7  allows the guidance, of the user, to a target position for which the RSSI measurement is similar or close to an optimal RSSI value or target value. 
     The target value of the method illustrated in  FIG. 7  corresponds, when it exists, to the highest RSSI value, stored in memory during the method disclosed in relation with  FIG. 6 . As an alternative, the target value corresponds to the average of the respective highest RSSI values of all sets of measurements stored. The target value is specific to each type and model of device. 
     A first step  701  (Identify tag device) consists in the identification of the device  200 B by the device  200 A. This first step  701  allows the type and the model of the device  200 B to be known. The identification of the device  200 B is, for example, based on an initial communication in which device  200 B sends an identifier to device  200 A. As an alternative, the first step  701  consists in reading a bar code of the device  200 B using a camera that equips the device  200 A. 
     The step  701  is followed by a step  703  (Best RSSI value for the tag and reader is present in memory?) that corresponds to the search of RSSI values related to the device  200 B in the internal memory of the device  200 A. 
     If stored RSSI values are not found in the internal memory (output N of block  703 ), the step  703  is followed by a step  705  (Best RSSI value for the tag and reader is present in the Cloud?) that corresponds to the search of RSSI values related to the device  200 B in a remote server, for example in the Cloud. 
     If RSSI values are not found in the Cloud (output N of block  705 ), step  705  is followed by a step  709  (Communication established) during which the method illustrated in  FIG. 6  is implemented. 
     If RSSI values are either found in the internal memory during the step  703  (output Y of block  703 ), or found in the cloud during step  705  (output Y of block  705 ), a step  707  is performed. 
     The step  707  consists in making, in a loop, successive RSSI measurements as long as the target position is not reached. 
     The step  707  starts with a sub-step  707 A of RSSI measurement (Measure and store RSSI). 
     Similarly to what has been described in  FIG. 6 , the RSSI measurement is periodic depending on parameters of device  200 A. Each measurement corresponds to a position of the device. 
     According to an embodiment, when the RSSI is measured, its value is added to a set of RSSI measurements, made of between, for example, 5 to 20 values. 
     The sub-step  707 A is followed by a sub-step  707 B in which it is determined whether the number of RSSI measurements is sufficient in order to determine the position of the device  200 A (Enough values?). If the set of RSSI measurements doesn&#39;t have enough values (output N of block  707 B), no feedback is provided to the user who can continue to move the device  200 A during a sub-step  707 F (User moves the phone). Sub-steps  707 F,  707 A and  707 B are repeated until the number for values is reached. 
     When the set of RSSI measurements has enough values (output Y of block  707 B), the sub-step  707 B is followed by a sub-step  707 C determining whether the set of RSSI measurements has a corresponding set of values in the memory (Corresponding set of values exists in memory?). If no correspondence is found (output N of block  707 C), no feedback is provided to the user who can continue to move the device  200 A during the sub-step  707 F, the sub-steps  707 F,  707 A,  707 B and  707 C are then repeated until an equivalence is found. 
     A correspondence between a set of RSSI measurements and a set of values in the memory allows the determination of the position of the device  200 A with respect to the target position. 
     The sub-step  707 C is, when a correspondence is found (output Y of block  707 C), followed by a sub-step  707 D in which it is determined whether the target position is reached 
     (Target position reached?). During the sub-step  707 D, the RSSI measurement is, for example, compared to the target value. An information about the RSSI measurement is, for example, returned to the user. This information about the RSSI measurement can correspond to a color indication. 
     For example: 
     if the RSSI measurement is greater than 75% of the target value, a red light is displayed on the user interface; 
     if the RSSI measurement is comprised between 75% and 50% of the target value, a yellow light is displayed on the user interface; and 
     if the RSSI measurement is lower than 50% of the target value, a green light is displayed on the user interface. 
     If the target value is reached (output Y of block  707 D), the communication between both devices  200 A and  200 B is established in a step  707 G (Communication established) and the loop ends. 
     If the target value is not reached (output N of block  707 D), the sub-step  707 D is followed by a sub-step  707 E indicating to the user the position of the device  200 A with respect to the target position (Indicate to the user if near or far from the target position). 
     During the sub-step  707 E, information about the distance between the device  200 A and the target position is provided to the user through the user interface. For example, this information is an audible information or a visual information. 
     According to an embodiment, this information corresponds to a sound, with the same tone, which is repeated at a different frequency depending on the distance between the position of the device  200 A with respect to the target position. For example, if the device  200 A is located close to the target position, the sound is repeated with a high frequency while the sound is repeated with a low frequency if the device  200 A is far from the target position. 
     According to another embodiment, this information corresponds to a visual display, such as arrows, indicating the direction of the target position. Existing sensors of the device are preferably used to indicate the relative position of the phone with the target position to the user. 
     After the sub-step  707 E, the user can move the phone during the sub-step  707 F. The sub-steps  707 A,  707 B,  707 C,  707 D,  707 E and  707 F are then repeated until the target position is reached. 
     For example, the user interface of the device  200 A allows the user to determine if he wants to execute the method disclosed in relation with  FIG. 6  or the method disclosed in relation with  FIG. 7 . 
     An advantage of the disclosed embodiments is that the target position is quickly reached. 
     Another advantage of the disclosed embodiments is that it allows to have a high coupling factor between both devices. 
     Another advantage of the disclosed embodiments is that it allows to have a fast communication. 
     Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these embodiments can be combined and other variants will readily occur to those skilled in the art. In particular, those skilled in the art are capable of adapting the embodiments and modes of implementation previously disclosed to other embodiments and modes of implementation in which audible and visual information are different from those indicated in the present disclosure. 
     Finally, the practical implementation of the embodiments and variants described herein is within the capabilities of those skilled in the art based on the functional description provided hereinabove. 
     A method, implemented by a first NFC device ( 200 A;  500 A) configured in reader mode, may be summarized as including a step of evaluating ( 603 ;  707 ) an information about the coupling between the first NFC device and a second NFC device ( 200 B;  500 B) configured in card mode, as a function of the position of an antenna ( 204 A) of the first NFC device with respect to an antenna ( 204 B) of the second NFC device; and a step of indicating ( 603 ;  707 E) said information on a user interface of the first device. 
     A system may be summarized as including a first NFC device ( 200 A;  500 A) configured in reader mode and a second NFC device ( 200 B;  500 B) configured in card mode, the first NFC device being adapted to implement the method. 
     Said indication of the information representative of the coupling may be a visual indication. 
     Said indication of the information representative of the coupling may be an audible indication. 
     Said evaluation step ( 603 ;  707 ) may include a measurement step ( 603 A;  707 A), by the first NFC device ( 200 A), of RSSI values from the second NFC device ( 200 B), according to the relative position of the first NFC device antenna ( 204 A) with respect to the second NFC device antenna ( 204 B). 
     The method or system may further include a comparison step ( 707 D) of the measured RSSI values with a target value. 
     The target value may be stored ( 607 ) in an internal memory of the first NFC device. 
     The target value may be stored ( 609 ) in a remote server. 
     The indication step ( 603 ) may include a mapping of said information representative of the coupling, based on a distribution of the RSSI values in, at least, three ranges of values. 
     A color may be affected to each range of value. 
     A sound may be affected to each range of value. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above- detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.