Near Field Communication Device and Method

Abstract

Embodiments of the present disclosure relate to near field communication devices and methods. A method includes: detecting, by a first near field communication device, the presence of a second near field communication device. In a case where the second device is intended to be charged in the near field by the first device, the method further includes: adjusting, by a control device, an impedance of an impedance matching circuit that forms a part of a near field communication circuit of the first device.

Description

Technical Field

[0001] The present disclosure generally relates to electronic devices. More specifically, the present disclosure relates to electronic devices integrating a Near Field Communication circuit (NFC) (more commonly referred to as NFC devices) and Near Field Communication devices implemented by these devices. Background Art

[0002] In addition to the method of near-field data exchange between NFC devices, NFC devices capable of implementing a near-field power transfer method designed to charge an NFC device with another NFC device are known. However, such NFC devices become complex, bulky, and expensive. Summary of the Invention

[0003] There is a need to improve Near Field Communication devices and their known communication methods.

[0004] Embodiments overcome all or part of the disadvantages of Near Field Communication devices and their known communication methods.

[0005] Embodiments provide a method including the following steps:

[0006] a) Detecting the presence of a second Near Field Communication device by a first Near Field Communication device; and

[0007] b) Adjusting the impedance of an impedance matching circuit forming part of the Near Field Communication circuit of the first device in the case where the second device is intended to be charged in the near field by the first device.

[0008] Embodiments provide a Near Field Communication circuit intended to be integrated in a first Near Field Communication device capable of detecting the presence of a second Near Field Communication device, the Near Field Communication circuit including:

[0009] An impedance matching circuit; and

[0010] A control device configured to adjust the impedance of the impedance matching circuit in the case where the second device is intended to be charged in the near field by the first device.

[0011] Embodiments provide a Near Field Communication device including:

[0012] A Near Field Communication circuit such as described; and

[0013] A Near Field Communication antenna coupled to the Near Field Communication circuit.

[0014] According to an embodiment, the impedance is set to:

[0015] A first value in the absence of the second device; and

[0016] A second value in the presence of the second device.

[0017] According to an embodiment, the detection is adjusted by detecting a change in the current flowing through the impedance matching circuit.

[0018] According to an embodiment, the detection is adjusted by detecting a change in the amplitude and phase of a signal transmitted by the first device.

[0019] According to an embodiment, the detection is adjusted by detecting the transmission of at least one data frame between the first device and the second device.

[0020] According to an embodiment, the impedance is adjusted by controlling at least one variable capacitance element of the impedance matching circuit.

[0021] According to an embodiment, the impedance is adjusted by connecting at least one second capacitance element in parallel with the first capacitance element of the impedance matching circuit.

[0022] According to an embodiment, the circuit further includes a near field communication controller coupled to the impedance matching circuit.

[0023] According to an embodiment, the control device is coupled to the near field communication controller and the impedance matching circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The foregoing and other features and advantages of the present disclosure will be discussed in detail in the following non-limiting description of specific embodiments and implementation modes in conjunction with the accompanying drawings, in which:

[0025] Figure 1 An example of a near field communication system to which the described embodiments and implementation modes are applicable is schematically shown in block form;

[0026] Figure 2 An example of a near field communication circuit is schematically shown in block form;

[0027] Figure 3 is a Figure 2 electrical diagram of a near field communication circuit according to an embodiment;

[0028] Figure 4 is a Figure 2 electrical diagram of a near field communication circuit according to another embodiment;

[0029] Figure 5 A method of controlling a near field communication circuit according to an implementation mode is shown;

[0030] Figure 6 An example of applying the described embodiments and implementation modes to data exchange between two near field communication devices is shown; and

[0031] Figure 7 Another example of applying the described embodiments and implementation modes to charging one device by another device is shown. DETAILED DESCRIPTION

[0032] In the various figures, similar features are designated by similar reference numerals. Specifically, structural and / or functional elements common to different embodiments and implementations may be designated by the same reference numerals and may have the same structure, dimensions, and material properties.

[0033] For the sake of clarity, only those steps and elements that are useful for understanding the described embodiments and implementation modes are shown and will be detailed. Specifically, the generation and interpretation of radio frequency signals are not detailed, and the described embodiments and implementation modes are compatible with common techniques for the generation and interpretation of such signals.

[0034] Unless otherwise indicated, when referring to two elements connected together, this means a direct connection without any intermediate elements other than conductors, and when referring to two elements coupled together, this means that the two elements may be connected, or they may be coupled via one or more other elements.

[0035] In the following description, when referring to terms that modify absolute positions (such as the terms "front", "back", "top", "bottom", "left", "right", etc.) or relative positions (such as the terms "above", "below", "upper", "lower", etc.) or terms that modify directions (such as the terms "horizontal", "vertical", etc.), unless otherwise specified, it refers to the orientation of the figure.

[0036] Unless otherwise specified, the expressions "around", "approximate", "substantially", and "about" mean within 10%, preferably within 5%.

[0037] In this description, the term NFC device designates an electronic device that integrates at least one near field communication circuit (NFC).

[0038] Figure 1 An example of a near field communication system of the type to which the described embodiments and implementation modes apply is shown very schematically.

[0039] In the example shown, a first NFC device 100A (DEV1) is capable of communicating with a second NFC device 100B (DEV2) through near field electromagnetic coupling. Depending on the application, for communication, one of the NFC devices 100A, 100B operates in a so-called reader mode, while the other NFC device 100B, 100A operates in a so-called card mode, or the two NFC devices 100A and 100B communicate in peer-to-peer mode (P2P).

[0040] Each NFC device 100A, 100B integrates, for example, a near field communication circuit, in Figure 1It is symbolized by frames 101A and 101B. For example, each of the near-field communication circuits 101A and 101B includes various components or electronic circuits for generating or detecting radio frequency signals by means of an antenna (not shown), such as modulation or demodulation circuits. During communication between NFC devices 100A and 100B, a radio frequency signal generated by one of the NFC devices 100A and 100B is captured, for example, by the other NFC device 100B or 100A within its range.

[0041] In the example shown, it is assumed that NFC device 100A emits an electromagnetic field (EMF) to initiate communication with NFC device 100B. Once within its range, the EMF field is captured, for example, by the second NFC device 100B. Then, in the case of the antennas of NFC device 100A and NFC device 100B, a coupling is formed between the two oscillating circuits. This coupling causes, for example, a change in the load formed by the circuit of NFC device 100B on the oscillating circuit for generating the EMF field of NFC device 100A.

[0042] For communication, the corresponding phase or amplitude change of the emitted field is detected, for example, by device 100A, and then the NFC communication protocol with device 100B is initiated. On the side of NFC device 100A, it is detected, for example, whether the voltage amplitude across the oscillating circuit and / or the phase shift relative to the signal generated by circuit 101A exceeds the amplitude and / or phase ranges respectively defined by the thresholds.

[0043] In the case of communication, once NFC device 100A detects the presence of NFC device 100B in its field, it starts the procedure for establishing communication, for example, implementing the transmission of requests by NFC device 100A and the transmission of responses by NFC device 100B (a polling sequence, such as defined in the NFC Forum specification).

[0044] For example, the application aims to utilize the EMF field to implement data exchange between NFC devices 100A and 100B. This corresponds, for example, to the case where NFC device 100A is a mobile terminal (such as a cellular phone or a touchpad), and NFC device 100B is, for example, a mobile terminal similar to NFC device 100A or a microcircuit card (such as a personal identification card). Then, the mobile terminal 100A reads data from or writes data to the mobile terminal, or reads data from or writes data to the microcircuit card 100B.

[0045] For example, other applications are more aimed at using the EMF field to implement power exchange between NFC devices 100A and 100B. Generally, this corresponds, for example, to the case where device 100B has a power source (not shown) (such as a battery) that can be charged by NFC device 100A. This more specifically corresponds, for example, to the following situation: NFC device 100A is a mobile terminal, such as a cellular phone or a touchpad, and NFC device 100B is a connected object, such as a connected watch, a connected bracelet, a pair of wireless earphones, a digital pen, etc. In this case, NFC device 100A, for example, has a battery with a larger capacity than NFC device 100B.

[0046] As an example, in the case where NFC device 100A is used to charge NFC device 100B, NFC device 100A is a wireless charging poller (WLC-P), and NFC device 100B is a wireless charging listener (WLC-L). In this case, NFC devices 100A and 100B, for example, implement wireless power transfer (WPT) such as defined in the NFC Forum specifications.

[0047] Generally, the near-field communication circuit 101A of NFC device 100A differs depending on whether it is implementing data exchange or power exchange with NFC device 100B. Therefore, if NFC device 100A is equipped with a circuit 101A optimized for data exchange with NFC device 100B, then this circuit generally cannot effectively charge NFC device 100B. Conversely, if NFC device 100A is equipped with a circuit 101A optimized for power exchange with NFC device 100B, then this circuit generally cannot effectively communicate with NFC device 100B. This limits the functionality of NFC device 100A.

[0048] To overcome this problem, for example, it can be provided that NFC device 100A is equipped with two optimized near-field communication circuits, one for data exchange and the other for charging NFC device 100B. However, this will result in an increase in the complexity, size, and cost of NFC device 100A.

[0049] For example, as a variant, it can be provided that NFC device 100 is equipped with a near-field communication circuit 101A and a wireless charging circuit using a standard other than the NFC standard, such as a circuit according to the "Qi" standard. In addition to the fact that this will increase the complexity, size, and cost of NFC device 100A, this will have the disadvantage of not being applicable to charging devices with small-sized power sources (such as connected objects).

[0050] Figure 2 An example of a near-field communication circuit 200 is schematically shown in block form. As an example, circuit 200 corresponds to Figure 1All or part of the frame 101A of the NFC device 100A.

[0051] In the illustrated example, the circuit 200 includes a near field communication controller 201 (NFC controller) or an NFC controller. The NFC controller 201 is, for example, an electronic chip or an electronic circuit capable of implementing near field communication. As an example, the NFC controller 201 is a microcontroller.

[0052] In the illustrated example, the NFC controller 201 is coupled to an electromagnetic interference filtering device 203 (EMI filter), more simply referred to as a filter. The filter 203 is, for example, a circuit including electronic components that are selected and arranged to attenuate one or more frequency bands of signals that can be transmitted or received by the NFC controller 201. As an example, the filter 203 includes at least one capacitive element (e.g., a capacitor) and at least one inductor (e.g., a coil).

[0053] In the illustrated example, the electromagnetic interference filter 203 is coupled to an impedance matching circuit 205 (matching network). The impedance matching circuit 205 is generally configured to maximize the amplitude of signals that can be transmitted or received by the NFC controller 201.

[0054] In the illustrated example, the impedance matching circuit 205 is coupled to an antenna 207 (antenna), such as a near field communication antenna. Generally, the circuit 205 is specifically designed to adapt to the electrical characteristics of the antenna 207. More specifically, the impedance matching circuit 205 includes, for example, a capacitor whose capacitance value is selected according to the impedance of the antenna 207. The capacitance value can also depend on the filter 203. As an example, when manufacturing the near field communication circuit 200, the capacitance value of the capacitor of the impedance matching circuit 205 can be set in the factory to accurately correspond to the actual electrical characteristics of the antenna 207 and the filter 203.

[0055] The near field communication circuit 200 may also include Figure 2 other elements or circuits shown by a single functional block 209 (FCT) in

[0056] Figure 3 is according to an embodiment Figure 2 electrical diagram of the near field communication circuit 200.

[0057] In the illustrated example, the NFC controller 201 (NFC controller) includes a core 301 (core) and an amplifier circuit 303 (driver). As Figure 3 illustrated, the amplifier circuit 303 includes, for example, two amplifiers 305 and 307 (“drivers”). For example, each amplifier 305, 307 includes output terminals 309, 311.

[0058] The amplifiers 305 and 307 of the amplifier circuit 303 are controlled, for example, by the core 301 of the NFC controller 201. As an example, the core 301 transmits radio frequency signals to the amplifiers 305 and 307. These radio frequency signals are then amplified by the amplifiers 305 and 307 and then transmitted to the filter 203 and the impedance matching circuit 205.

[0059] The filter 203 (EMI filter) is connected, for example, to the respective output terminals 309 and 311 of the amplifiers 305 and 307. In the example shown, the filter 203 includes inductors 313 and 315, such as coils. The coil 313 is connected, for example, to the terminal 309 and the node 317 of the filter 203. The coil 315 is connected, for example, to the terminal 311 and another node 319 of the filter 203. In the example shown, the filter 203 also includes capacitive elements 321 and 323, such as capacitors. The capacitor 321 is connected, for example, to the node 317 and the node 325 to which the reference potential is applied, such as ground. The capacitor 323 is connected, for example, to the node 319 and the node 325.

[0060] According to an embodiment, the impedance matching circuit 205 includes at least one variable capacitive element. In the example shown, the impedance matching circuit 205 includes variable capacitive elements 327, 329, and 331, such as capacitors having variable capacitance. The capacitor 327 is connected, for example, to the node 317 and the node 333 of the impedance matching circuit 205. The capacitor 329 is connected, for example, to the node 319 and another node 335 of the impedance matching circuit 205. The capacitor 331 is connected, for example, to the node 333 and the node 335.

[0061] In the example shown, the antenna 207 is connected to the nodes 333 and 335. The variable capacitance capacitors 327 and 329 are connected in series between the NFC controller 201 and the antenna 207. The variable capacitance capacitor 331 is connected in parallel with the antenna 207. For simplicity, the capacitors 327 and 329 are referred to as series capacitors, and the capacitor 331 is referred to as a parallel capacitor.

[0062] In the example shown, the capacitors 327, 329, and 331 are controlled by the NFC controller 201. More specifically, the NFC controller 201 is configured, for example, to transmit control signals capable of modifying their capacitance to each of the capacitors 327, 329, 331. In this case, the NFC controller 201 forms, for example, a control device configured to adjust the impedance of the circuit 205.

[0063] The variable capacitance capacitors 327, 329, and 331 are specifically capable of adjusting the impedance of the impedance matching circuit 205. In the example of the integrated circuit 200 of the NFC device 100A, the capacitance values of the capacitors 327, 329, and 331 can be adjusted, for example, according to the type of the device 100B within its range. As an example, for instance, in the case of data exchange between the NFC devices 100A and 100B, it can be provided to adjust the capacitance values of the capacitors 327, 329, and 331 according to a first configuration aimed at optimizing data transmission of the antenna 207. For example, in the case of the NFC device 100A charging the NFC device 100B, it can also be provided to adjust the capacitance values of the capacitors 327, 329, and 331 according to a second configuration aimed at optimizing power exchange of the antenna 207.

[0064] Although an example including two series capacitance elements 327 and 329 and one parallel capacitance element 331 has been described herein, it is within the ability of those skilled in the art to adapt the number of parallel capacitance elements and series capacitance elements according to the target application. Further, although Figure 3 the embodiment is discussed with respect to an application example of the communication circuit 200 connected to an antenna including two terminals or ends ("two-terminal antenna"), this embodiment can be switched by those skilled in the art to a communication circuit connected to an antenna that includes a single terminal or end ("single-terminal antenna").

[0065] Regarding Figure 3 An advantage of the embodiment of the circuit 200 described is the fact that the variable capacitance elements 327, 329, and 331 can adjust the impedance of the circuit 205 according to the type of the NFC device 100B within its range. Thus, for example, integrating multiple near-field communication circuits and / or multiple antennas in the NFC device 100A is avoided. This makes it possible to reduce the complexity, size, and cost of the NFC device 100A.

[0066] Figure 4 is according to another embodiment of Figure 2 the electrical diagram of the near-field communication circuit 200. Figure 4 The circuit 200 of Figure 3 includes elements common to the circuit 200 of Figure 4 These common elements will not be elaborated further hereinafter. Figure 3 The circuit 200 of Figure 4 differs from the circuit 200 of

[0067] In the example shown, the terminals of the NFC controller 201 (NFC controller) are connected to the terminals of the control circuit 401. As an example, this enables the control circuit 401 to receive a synchronization signal, a selection signal, a data signal to be transmitted by the antenna 207, etc.

[0068] In the example shown, the terminals of the control circuit 401 are connected to the impedance matching circuit 205 (matching network). More specifically, the terminals 403, 405 of the control circuit 401 are respectively connected to the terminals 407, 409 of a transformer 411 (e.g., an isolation transformer). Two other terminals 413, 415 of the isolation transformer 411 are coupled or connected to the nodes 417, 419 of the impedance matching circuit 205, respectively. The node 419 is, for example, a node to which a reference potential is applied, such as ground.

[0069] In the example shown, a capacitor 421 is connected to the terminal 413 of the isolation transformer 411 and the node 417 of the impedance matching circuit 205. Another capacitive element 423 is connected to the nodes 417 and 419 of the impedance matching circuit 205, for example. The antenna 207 is connected to the nodes 417 and 419 of the impedance matching circuit 205 in parallel with the capacitive element 423, for example. For example, the capacitive elements 421 and 423 are capacitors having a fixed capacitance.

[0070] In the example shown:

[0071] Another terminal 425 of the control circuit 401 is connected to the terminal 413 of the isolation transformer 411;

[0072] Another terminal 427 of the control circuit 401 is connected to the node 417 of the impedance matching circuit 205;

[0073] Another terminal 429 of the control circuit 401 is connected to the node 417 of the impedance matching circuit 205; and

[0074] Another terminal 431 of the control circuit 401 is connected to the node to which the reference potential is applied, which is ground in this example.

[0075] In the example shown, the control circuit 401 includes a variable capacitive element 433 connected between the terminals 425 and 427. The control circuit 401 also includes another variable capacitive element 435 connected between the terminals 429 and 431. In the example shown, the variable capacitive element 433 is connected in parallel with the capacitive element 421 of the impedance matching circuit 205. The variable capacitive element 435 is connected in parallel with the capacitive element 423 of the impedance matching circuit 205. By adjusting the capacitance values of the variable capacitive elements 433 and 435 of the control circuit 401, it is possible, for example, to modify the series and parallel capacitive elements of the impedance matching circuit 205.

[0076] As an example, the variable capacitance elements 433 and 435 of the control circuit 401 are formed by components of capacitance elements, such as capacitors, connected in parallel with each other and individually selectable. For example, by using a control signal transmitted from the NFC controller 201 to the control circuit 401, it is possible to select a plurality of capacitance elements to be connected in parallel with the capacitance elements 421 and 423 of the impedance matching circuit 205 to adjust its impedance. In this case, the control circuit 401 forms, for example, a control device configured to adjust the impedance of the circuit 205.

[0077] In the example shown, the NFC controller includes terminals 437 and 439 coupled to terminals 407 and 409 of the isolation transformer 411 via resistors 441 and 443, respectively. The terminals 437 and 439 are capable of receiving, for example, signals captured by the antenna 207.

[0078] As described above with respect to Figure 4 an advantage of the near field communication circuit 200 discussed is the fact that the impedance of the impedance matching circuit 205 is adjusted by the variable capacitance elements 433 and 435 of the control circuit 401. This enables the implementation of impedance adjustment functionality without having to modify the impedance matching circuit 205, the NFC controller 201, and / or the antenna 207.

[0079] Figure 5 A method 500 for controlling a near field communication circuit according to an embodiment mode is shown. The method 500 is implemented, for example, by the circuit 200 previously described with respect to Figure 3 and 4 The circuit 200 is integrated, for example, in the NFC device 100A ( Figure 1 ).

[0080] In the example shown, the method 500 includes an initial step 501 (idle). As an example, the initial step 501 corresponds to the step in which the circuit 200 does not perform near field communication.

[0081] During another step 503 (attempt to detect NFC device) after the step 501, the near field communication circuit 200 attempts to detect an NFC device within its range. This corresponds, for example, to field emission such as previously described with respect to Figure 1 The description of the field emission.

[0082] During yet another step 505 (NFC device detected?) after the step 503, it is verified whether an NFC device (e.g., the NFC device 100B ( Figure 1 )) is within its range. As an example, the detection of the NFC device 100B is based on at least one of the following conditions:

[0083] A change in the current flowing through the impedance matching circuit 205;

[0084] The amplitude and phase variations of the signal transmitted by the NFC device 100A embedded in the circuit 200; and

[0085] The transmission of at least one data frame between the NFC devices 100A and 100B.

[0086] In the case where the NFC device 100B is detected by the NFC device 100A (the output of block 505 is yes), a further step 507 (identifying the device type) is performed to identify the type of the NFC device 100B. In the relative case, i.e., if the NFC device is not detected during step 505 (the output of block 505 is no), for example, it returns to step 503.

[0087] During step 505, for example, it is estimated whether the NFC device 100B is intended to exchange data with the NFC device 100A or whether the NFC device 100B is more intended to be charged by the NFC device 100A.

[0088] During a further step 509 (WLC-L device?) after step 507, it is verified whether the detected NFC device 100B is of the WLC-L type. In the case where the NFC device 100B is not of the WLC-L type (the output of block 509 is no), a further step 511 (maintaining the impedance equal to Z1) is performed to maintain the impedance of the impedance matching circuit 205 at a first value Z1. For example, the impedance value Z1 corresponds to a configuration in which the impedance matching circuit 205 of the NFC device 100A is optimized to exchange data with the NFC device 100B. As an example, the value Z1 is approximately equal to 8 ohms.

[0089] During a further step 513 (exchanging data with the NFC device) after step 511, for example, the data exchange between the NFC devices 100A and 100B is performed.

[0090] During a further step 515 (is the data exchange over?) after step 513, for example, it is verified whether the data exchange between the NFC devices 100A and 100B has ended or whether the NFC device 100B has left the field. If this is the case (the output of block 515 is yes), for example, it returns to the initial step 501. In contrast, i.e., for example, if the NFC device 100B is still in the field of the NFC device 100A and if the data exchange is in progress (the output of block 515 is no), for example, it returns to step 513.

[0091] In step 509, if the detected device is of the WLC-L type (the output of block 509 is), then proceed to another step 517 of adjusting the impedance of impedance matching circuit 205 to a second value Z2 (set the impedance to Z2). For example, the impedance value Z2 corresponds to a configuration in which the impedance matching circuit 205 of NFC device 100A is optimized to exchange power with NFC device 100B to, for example, charge NFC device 100B. As an example, the value Z2 is approximately equal to 12 ohms.

[0092] During another step 519 (exchange power with WLC-L device) after step 517, NFC device 100A, for example, starts to charge NFC device 100B. During another step 521 (is power exchange ended?) after step 519, for example, verify whether the charging of NFC device 100B has ended or whether NFC device 100B has left the field of NFC device 100A. If this is the case (the output of block 521 is), then proceed to another step 523 of adjusting the impedance of impedance matching circuit 205 to a first value Z1 (set the impedance to Z1). On the contrary, that is, for example, if NFC device 100B is still in the field of NFC device 100A and if the charging is in progress (the output of block 521 is no), then, for example, return to step 519.

[0093] An advantage of method 500 is that the impedance of impedance matching circuit 205 can be adjusted according to the detected type of NFC device 100B. If NFC device 100B is of the WLC-L type, the impedance of circuit 205 is adjusted to facilitate the charging of NFC device 100B. On the contrary, as long as a WLC-L type device is not detected by NFC device 100A, the impedance of circuit 205 remains at a value that can optimize data exchange. Specifically, this can more quickly detect NFC device 100B that wishes to exchange data with NFC device 100A.

[0094] Figure 6 An example of applying the described embodiments and implementation modes to data exchange between two near field communication devices 600A, 600B is shown. In the shown example, NFC devices 600A and 600B are cellular phones.

[0095] Cellular phone 600A, for example, integrates the near field communication circuit described with respect to Figure 4 More specifically, cellular phone 600A includes an NFC controller 201 coupled or connected to control circuit 401 and impedance matching circuit 205.

[0096] Cellular phone 600A exchanges data with cellular phone 600B, for example, via an electromagnetic field EMF. The impedance of circuit 205 is then, for example, equal to value Z1.

[0097] Figure 7 illustrates another example of applying the described embodiments and implementation modes to charging device 700 by device 600A Figure 6 . In the illustrated example, NFC device 700 is a pair of wireless earphones.

[0098] Cellular phone 600A charges battery 701 integrated in each of a pair of wireless earphones 700 via, for example, electromagnetic field EMF. The impedance of circuit 205 then equals, for example, value Z2.

[0099] Depending on the situation, circuit 200 enables device 600A to exchange data with cellular phone 600B or to charge a pair of wireless earphones 700 by adjusting the impedance of circuit 205 (e.g., by implementing method 500 discussed with respect to Figure 5 ).

[0100] Various embodiments, implementation modes, and variations have been described. Those skilled in the art will understand that certain features of these various embodiments, implementation modes, and variations can be combined, and other variations will occur to those skilled in the art. Specifically, the number of variable capacitance elements can be adjusted according to the application.

[0101] Finally, based on the functional indications given above, the actual implementation of the described embodiments, implementation modes, and variations is within the ability of those skilled in the art. Specifically, forming variable capacitance elements to obtain an impedance range corresponding to the target application will be within the ability of those skilled in the art.

[0102] Method (500) can be generally summarized as including the following steps: a) detecting the presence of a second near-field communication device (100B; 600B; 700) by a first near-field communication device (100A; 600A); and b) adjusting the impedance of an impedance matching circuit (205) that forms part of the near-field communication circuit (200) of the first device in the case where the second device is intended to be charged in the near field by the first device by a control device (201; 401).

[0103] A near-field communication circuit (200), intended to be integrated in a first near-field communication device (100A; 600A) capable of detecting the presence of a second near-field communication device (100B; 600B; 700), can be generally summarized as including an impedance matching circuit (205); and a control device (201; 401), configured to adjust the impedance of the impedance matching circuit in the case where the second device is intended to be charged in the near field by the first device.

[0104] A near-field communication device (100A; 600A) can be generally summarized as including a near-field communication circuit (200) and a near-field communication antenna (207) coupled to the near-field communication circuit.

[0105] In the absence of a second device (100B; 600B, 700), the impedance can be set to a first value (Z1); and in the presence of a second device, it can be set to a second value (Z2).

[0106] Detection can be adjusted by changes in the current flowing through the impedance matching circuit (205).

[0107] Detection can be adjusted by changes in the amplitude and phase of the signal transmitted by the first device (100A; 600A).

[0108] Detection can be adjusted by the transmission of at least one data frame between the first device (100A; 600A) and the second device (100B; 600B; 700).

[0109] The impedance can be adjusted by controlling at least one variable capacitance element (327, 329, 331) of the impedance matching circuit (205).

[0110] The impedance can be adjusted by connecting at least one second capacitance element (433, 435) in parallel with the first capacitance elements (421, 423) of the impedance matching circuit (205).

[0111] The circuit can further include a near field communication controller (201) coupled to the impedance matching circuit (205).

[0112] The control device (401) can be coupled to the near field communication controller (201) and the impedance matching circuit (205).

[0113] The various embodiments described above can be combined to provide other embodiments. In view of the description detailed above, these and other changes can be made to the embodiments.

[0114] Generally, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in this specification and the claims, but should be construed to include all possible embodiments and the full scope of equivalents to which such claims are entitled. Thus, the claims are not limited by the present disclosure.

Claims

1. A method for near field communication, comprising: Detecting the presence of a second near field communication device by a first near field communication device; Using the first near field communication device to detect whether the second near field communication device is a first type of device configured to be charged by the first near field communication device or a second type of device configured to exchange data with the first near field communication device; If the second near field communication device is the first type of device: Adjusting, by a control device of the first near field communication device, an impedance of an impedance matching circuit that forms part of a near field communication circuit of the first near field communication device from a first impedance value to a second impedance value, the adjustment being performed by adjusting a capacitance of a variable capacitor; And Transmitting an electromagnetic field using an antenna of the first near field communication device when the matching circuit is at the second impedance value; If the second near field communication device is the second type of device: Keeping the impedance of the impedance matching circuit unchanged; And Transmitting an electromagnetic field using the antenna when the impedance matching circuit is at the first impedance value.

2. The method according to claim 1, wherein the impedance is set to: The first impedance value in the absence of the second near field communication device; and The second impedance value in the presence of the second near field communication device.

3. The method according to claim 1, wherein the detection is adjusted by a change in current flowing through the impedance matching circuit.

4. The method according to claim 1, wherein the detection is adjusted by changes in amplitude and phase of a signal transmitted by the first near field communication device.

5. The method according to claim 1, wherein the detection is adjusted by transmission of at least one data frame between the first near field communication device and the second near field communication device.

6. The method according to claim 1, wherein the impedance is adjusted by controlling at least one variable capacitance element of the impedance matching circuit.

7. The method according to claim 1, wherein the impedance is adjusted by connecting at least one second capacitance element in parallel with a first capacitance element of the impedance matching circuit.

8. A near field communication circuit configured to be integrated in a first near field communication device capable of detecting the presence of a second near field communication device, the near field communication circuit comprising: An impedance matching circuit; And A control device configured to: Detect whether the second near field communication device is a first type of device configured to be charged by the first near field communication device or a second type of device configured to exchange data with the first near field communication device; If the second near field communication device is configured to be charged by the first near field communication device in the near field, adjust the impedance of the impedance matching circuit from a first impedance value to a second impedance value, the adjustment being performed by adjusting a capacitance of a variable capacitor, Transmit an electromagnetic field using an antenna of the first near field communication device when the matching circuit is at the second impedance value, If the second near field communication device is intended to exchange data with the first near field communication device and the same antenna is alternatively used for power exchange and communication, the impedance of the impedance matching circuit is kept unchanged, and using the antenna, an electromagnetic field is emitted when the impedance matching circuit is at the first impedance value.

9. The circuit according to claim 8, wherein the impedance is set to: the first impedance value in the absence of the second near field communication device; and the second impedance value in the presence of the second near field communication device.

10. The circuit according to claim 8, wherein the detection is adjusted by a change in the current flowing through the impedance matching circuit.

11. The circuit according to claim 8, wherein the detection is adjusted by changes in the amplitude and phase of a signal transmitted by the first near field communication device.

12. The circuit according to claim 8, wherein the detection is adjusted by the transmission of at least one data frame between the first near field communication device and the second near field communication device.

13. The circuit according to claim 8, wherein the impedance is adjusted by controlling at least one variable capacitance element of the impedance matching circuit.

14. The circuit according to claim 8, wherein the impedance is adjusted by connecting at least one second capacitance element in parallel with a first capacitance element of the impedance matching circuit.

15. The circuit according to claim 8, further comprising a near field communication controller coupled to the impedance matching circuit.

16. The circuit according to claim 15, wherein the control device is coupled to the near field communication controller and the impedance matching circuit.

17. A near field communication device, comprising: a near field communication circuit configured to be integrated in a first near field communication device capable of detecting the presence of a second near field communication device, the near field communication circuit comprising: a near field communication antenna coupled to the near field communication circuit; an impedance matching circuit comprising a variable capacitor; and a control device configured to: detect whether the second near field communication device is a first type of device configured to be charged by the first near field communication device in the near field or a second type of device configured to exchange data with the first near field communication device, if the second near field communication device is configured to be charged by the first near field communication device in the near field, adjust the impedance of the impedance matching circuit from a first impedance value to a second impedance value, the adjustment being performed by adjusting the capacitance of the variable capacitor, and using the near field communication antenna, emit an electromagnetic field when the matching circuit is at the second impedance value, if the second near field communication device is intended to exchange data with the first near field communication device and the same near field communication antenna is alternatively used for power exchange and communication, keep the impedance of the impedance matching circuit unchanged; and using the antenna, emit an electromagnetic field when the impedance matching circuit is at the first impedance value.

18. The device according to claim 17, wherein the impedance is set to: the first impedance value in the absence of the second near field communication device; and is the second impedance value in the presence of the second near field communication device.

19. The apparatus according to claim 17, further comprising a near field communication controller coupled to the impedance matching circuit.

20. The apparatus according to claim 19, wherein the control device is coupled to the near field communication controller and the impedance matching circuit.

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