Contactless communication device modulated by active load

Abstract

The invention relates to a contactless communication device modulated by an active load. An apparatus for contactless communication by active load modulation includes a receive circuit configured to receive as an input a receive signal originating from a magnetic field intended to be received by an antenna. The transmission circuit has an output coupled to the antenna, the output having a modulated signal intended to be delivered thereon in phase with the received signal. The circuit compensates for the delay of the modulated signal due to the transmission circuit and due to the amplitude of the received signal. A compensation circuit determines an input signal to be applied to the transmission circuit to compensate for a delayed phase shift value.

Description

[0001] Priority requirements

[0002] This application claims priority to French patent application No. 2310036, filed on September 22, 2023, the contents of which are incorporated herein by reference in their entirety to the fullest extent permitted by law. Technical Field

[0003] This disclosure generally relates to the field of wireless communication between a reader and a contactless communication device via active load modulation, and particularly to the field of wireless communication between a reader and such a device operating in card emulation (CE) mode. This disclosure may especially relate to the field of contactless communication implemented using near field communication (NFC) technology. Background Technology

[0004] Near Field Communication (NFC) is a wireless connectivity technology that allows communication between electronic devices (such as contactless chip cards and readers, or devices operating in card emulation (CE) mode (e.g., cellular phones or connected objects) and readers) over short distances (e.g., a few tens of centimeters).

[0005] A contactless communication device is a device that can exchange information with another contactless device (e.g., a reader) via an antenna according to a contactless communication protocol.

[0006] NFC devices, as contactless devices, are devices compatible with NFC technology. NFC technology is an open technology platform standardized by ISO / IEC 18092 and ISO / IEC 21481 standards, but it incorporates many existing standards, such as the Type A and Type B protocols defined in ISO-14443, which can be communication protocols used in NFC technology.

[0007] By using the contactless communication protocols available in NFC technology, CE devices can be used to exchange information with another contactless device (e.g., a contactless reader).

[0008] During information transmission between the reader and the CE device or NFC card, the reader generates an electromagnetic field via its antenna, which is typically a sine wave with a frequency of 13.56 MHz according to commonly used standards. Each NFC device (reader and CE device) transmits data using a modulation scheme (e.g., amplitude shift keying or ASK).

[0009] There may be two operating modes: passive mode (corresponding to the mode used by NFC cards) or active mode (generally corresponding to the mode used by CE devices).

[0010] In passive mode (also known as passive load modulation (PLM)), only the reader generates the electromagnetic field, while the card remains passive. The card antenna modulates the electromagnetic field generated by the reader by modifying the load connected to both ends of the card antenna, which changes the output impedance of the reader antenna due to the magnetic coupling between the two antennas. This results in changes in the amplitude and / or phase of the voltage and current present at the antennas of both the card and the reader. Therefore, information is transmitted from the card to the reader through load modulation of the reader's antenna current.

[0011] In active mode (also known as active load modulation (ALM)), both the reader and the CE device generate electromagnetic fields. This operating mode is used when the CE device is powered by a specific source (e.g., a battery).

[0012] Generally speaking, CE devices include antennas smaller than those of NFC cards, which is why active load modulation is typically used in such devices.

[0013] During active load modulation, the electromagnetic fields emitted by the reader and the CE device are in phase with each other, so the detection sensitivity of the device does not decrease. The CE device may specifically include a transmission circuit whose output is coupled to the antenna, as well as a phase-locked loop (PLL) specifically used to compensate for propagation delays in the transmission circuit.

[0014] However, the components of the transmission circuit are susceptible to variations in process, voltage, and temperature (PVT), which can cause delays or advances in the signal delivered at the output of the transmission signal, resulting in a phase shift between the electromagnetic field emitted by the reader and the electromagnetic field emitted by the CE device. This phase shift is also contributed by the coupling between the reader's antenna and the CE device's antenna, and / or by variations in the amplitude of the electromagnetic field emitted by the reader, because the transmission delay of the signal through the transmission circuit also varies depending on the amplitude of the received electromagnetic field and therefore on the coupling between the reader's antenna and the CE device's antenna.

[0015] There is a need to provide a solution that can address the problems encountered by existing solutions. Summary of the Invention

[0016] In embodiments that overcome all or part of the drawbacks of known solutions, a device for contactless communication via active load modulation includes at least: a receiving circuit configured to receive a received signal originating from an electromagnetic field intended to be received by an antenna as input; a transmitting circuit including an output coupled to the antenna and having a modulated signal in phase with the received signal intended to be delivered thereon; and circuitry for compensating for delays in the modulated signal caused by the amplitude of the transmitting circuit and the received signal, configured to determine an input signal to be applied to the transmitting circuit to compensate for the delay phase shift value.

[0017] According to a specific embodiment, the device further includes a phase-locked loop configured to receive a first clock signal delivered at the output of the receiving circuit and a phase shift value as input, and to deliver an input signal of the transmission circuit at the first output.

[0018] According to a specific embodiment, the compensation circuit includes at least a circuit for measuring the phase difference between the input signal of the transmission circuit and the delayed signal, wherein the delayed signal corresponds to the input signal of the transmission circuit that has been delayed.

[0019] According to a specific embodiment, the measurement circuit includes at least: a counting trigger circuit, including a first input terminal configured to receive an input signal from at least a transmission circuit, a second input terminal configured to receive a signal with at least a delay, and a counting trigger signal configured to deliver a counting trigger signal as an output, the counting trigger signal having a first value for a time period equal to the delay and a second value different from the first value outside this time period; a counter, including a clock input terminal coupled to the output of the counting trigger circuit, and a data input terminal coupled to a second output terminal of a phase-locked loop, on which a periodic signal having a frequency equal to a multiple of the frequency of the input signal from the transmission circuit is intended to be delivered; and a calculation circuit configured to determine a phase shift value based on the value of the counting signal intended to be delivered by the counter.

[0020] According to a specific embodiment, the transmission circuit includes a controlled switch having an output terminal corresponding to the output terminal of the transmission circuit.

[0021] According to a specific embodiment, the transmission circuit includes a control input terminal configured to receive a signal controlling whether a signal is transmitted at the output terminal of the transmission circuit, and includes a delay circuit having an input terminal coupled to the input terminal of the transmission circuit, an output terminal coupled to a second input terminal of a counting trigger circuit, and is configured to apply a delay having a value equal to the delay caused by the transmission circuit.

[0022] According to a specific embodiment, the receiving circuit includes at least: a variable gain amplifier configured to receive a received signal as input; and a converter for converting a sine signal into a square wave signal, including an input coupled to the output of the variable gain amplifier and an output corresponding to the output of the receiving circuit.

[0023] According to a specific embodiment, a method for contactless communication between a reader and a device is provided, the method comprising the implementation of at least the following steps: detecting a magnetic field by the device; when the magnetic field is detected by the device, transmitting a first clock signal through a receiving circuit of the device, the receiving circuit receiving a received signal originating from the magnetic field as input; measuring and compensating for a delay in the modulated signal caused by the amplitude of the transmission circuit and the received signal in a signal applied at the input of the transmission circuit of the device, the compensated delay depending on the amplitude of the received signal and a target amplitude of the modulated signal intended to be delivered at the output of the transmission circuit; and applying the modulated signal to an antenna through the transmission circuit of the device.

[0024] According to a specific embodiment, after the receiving circuit of the device transmits the first clock signal, the phase-locked loop is started and locked onto the first clock signal.

[0025] According to a specific embodiment, the method further includes, between the transmission of the first clock signal and the application of the phase shift value: measuring the received power; and pre-programming the power of the components of the transmission circuit based on the measured received power.

[0026] According to a specific embodiment, the method further includes applying a control signal to the control input terminal of the controlled switch of the transmission circuit or the control input terminal of the transmission circuit before measuring and compensating for the delay, so that no signal is delivered at the output terminal of the transmission circuit.

[0027] According to a specific embodiment, the method further includes, after measuring and compensating for the delay, applying a control signal to the control input terminal of the controlled switch of the transmission circuit or the control input terminal of the transmission circuit in such a way that a modulated signal is delivered at the output terminal of the transmission circuit. Attached Figure Description

[0028] The foregoing features and advantages, as well as other features and advantages, will be described in detail with reference to the accompanying drawings in the remainder of the disclosure of specific embodiments given by way of illustration rather than limitation, wherein:

[0029] Figure 1 An example of a device for contactless communication via active load modulation is illustrated schematically;

[0030] Figure 2 Details of a first example of a device for contactless communication via active load modulation are schematically illustrated.

[0031] Figure 3 Details of a second example of a device for contactless communication via active load modulation are schematically illustrated.

[0032] Figure 4The steps of an example of a communication method for a device that communicates with a reader in a contactless manner via active load modulation are illustrated schematically.

[0033] Figure 5 Details of a second example of a device for contactless communication via active load modulation are schematically illustrated.

[0034] Figure 6 An example of a phase-locked loop counter in a device for contactless communication modulated by an active load is illustrated schematically;

[0035] Figure 7 An example of a counting trigger circuit and a counter is schematically shown, which constitute part of a device for contactless communication modulated by an active load; and

[0036] Figure 8 It shows Figure 7 Timing diagrams for examples of signals used in the circuit. Detailed Implementation

[0037] Similar features in the various figures are indicated by similar reference numerals. In particular, common structural and / or functional features between the various embodiments may have the same reference numerals and may have identical structures, dimensions, and material properties.

[0038] For clarity, only the steps and components useful for understanding the described embodiments are illustrated and described in detail. In particular, the formation of the various components and circuits of the device (variable gain amplifier, sine-to-square wave converter, phase-locked loop, lookup table, analog-to-digital converter, computing circuit, delay circuit, trigger, counter, etc.) is not described in detail. Those skilled in the art can implement the various functions of the device in a detailed manner based on the functional description given herein.

[0039] Unless otherwise indicated, when referring to two elements connected together, it means a direct connection without any intermediate elements other than a conductor, and when referring to two elements coupled together, it means that the two elements can be connected or they can be coupled via one or more other elements.

[0040] Unless otherwise indicated, the expressions “approximately,” “around,” “substantially,” and “…about” indicate an addition or subtraction of 10%, preferably 5%.

[0041] The following is combined Figure 1 An example of a device 100 for contactless communication via active load modulation according to a particular embodiment is described.

[0042] Device 100 is of NFC type, meaning it is configured to use a communication protocol compatible with NFC technology. In the described example, device 100 corresponds to a device in Card Emulation Mode (CE). Figure 1 The image shows a device 100 communicating with an NFC-type contactless reader (R) 200.

[0043] In the example, device 100 includes antenna 102, which is designed to exchange data with antenna 202 of reader 200 via electromagnetic field transmission through antennas 102, 202 and magnetic coupling of antennas 102, 202.

[0044] exist Figure 1 In the specific configuration shown, device 100 also includes a matching circuit (M) 104 coupled between antenna 102 and other components of device 100. Circuit 104 can be used in particular to match the impedance of antenna 102 to interface the input and output signals of antenna 102.

[0045] Device 100 also includes a receiving circuit 110 configured to receive a received signal originating from an electromagnetic field intended to be received by antenna 102 as input, and to deliver a first clock signal as output. Figure 1 In this context, the received signal is called "RFI" and corresponds to a sinusoidal signal. The frequency of the RFI signal is, for example, equal to 13.56 MHz.

[0046] In Figure 1 In the specific configuration corresponding to the configuration shown, the receiving circuit 110 includes at least: a variable gain amplifier or VGA 112, configured to receive the signal RFI as input; and a sine wave to square wave converter 114, including an input coupled to the output of the VGA 112, and an output having a first clock signal intended to be delivered thereon.

[0047] In this specific configuration, the signal transmitted at the output of converter 114 corresponds to a square wave signal with an amplitude greater than that of signal RFI, that is, it corresponds to the transformation of signal RFI into a square wave signal amplified with a gain greater than 1.

[0048] As a variant, the receiving circuit 110 may include additional elements and / or... Figure 1 The example components are different from the components.

[0049] Device 100 also includes transmission circuitry 116, which includes an output coupled to circuitry 104 and is designed to deliver a modulated signal, referred to as “RFO”, to antenna 102 at this output. This RFO signal contains information that device 100 intends to transmit to reader 200. The RFO signal is intended to be in phase with the RFI signal.

[0050] Device 100 also includes a compensation circuit (Cmp) 118 for compensating for the delay δ of the signal RFO caused by the transmission circuit 116 and by the amplitude of the signal RFI. TX This includes delays caused by PVT variations in the components of transmission circuit 116. When device 100 communicates with reader 200, the amplitude of the signal RFI can be proportional to the amplitude of the electromagnetic field received by antenna 102, and thus proportional to the coupling between antennas 102 and 202. Compensation circuit 118 is configured to determine the input signal to be applied to transmission circuit 116 each time device 100 is started to compensate for delay δ. TX The phase shift value.

[0051] exist Figure 1 In the specific configuration shown, device 100 also includes a phase-locked loop (PLL) 120, which is designed to synchronize the signal RFO with the received signal RFI, thereby compensating for delays caused by signal processing in different circuits and components of device 100. This PLL 120 is configured to receive a first clock signal delivered by receiving circuit 110 and a phase shift value determined by compensation circuit 118 as inputs, and to deliver the input signal of transmission circuit 116 at a first output. Therefore, PLL 120 is configured here to take into account the phase shift value determined by compensation circuit 118, such that the signal delivered to transmission circuit 116 at the output of PLL 120 does not include further phase shifts or delays caused by transmission circuit 116 and by the amplitude of signal RFI.

[0052] exist Figure 1 The diagram only shows some of the components of device 100. Besides... Figure 1 In addition to the components shown, device 100 also includes other circuits and components not described herein, such as, for example, circuitry for modulating and demodulating data received and transmitted by device 100.

[0053] exist Figure 1 In the configuration shown, device 100 also includes a battery (B) 122 designed to power the various circuits and components of device 100.

[0054] The following is combined Figure 2 A more detailed first example describing device 100. Figure 2 In this document, only portions of the components and circuitry of device 100 are shown and described below. For example, with Figure 1 compared to, Figure 2 The antenna 102 and circuit 104 of device 100 are not shown in the diagram.

[0055] In the described example, the compensation circuit 118 includes a signal for measuring the input signal of the transmission circuit 116 obtained at the output of the PLL 120 and a delay δ. TX The circuit 116 is a circuit that measures the phase difference between the input signal and the delayed signal.

[0056] In Figure 2 In the specific configuration corresponding to the shown configuration, this measurement circuit includes: a counting trigger circuit 128, which includes a first input terminal having an input signal intended to be applied to a transmission circuit 116, and a delayed signal intended to be applied to it (delayed by a delay δ). TX The second input terminal of the transmission circuit 116 (the input signal) is configured to deliver a counting trigger signal as an output, which is equal to the delay δ. TX The time period has a first value and outside the time period has a second value different from the first value; a counter (C) 130 includes a clock input coupled to the output of circuit 128 and a data input coupled to the second output of PLL 120, which is intended to deliver a periodic signal having a frequency equal to a multiple of the frequency of the input signal of transmission circuit 116; and a calculation circuit (CM) 132, configured to determine the phase shift value to be applied based on the value of the count signal intended to be delivered by counter 130, the output of counter 130 being coupled to the input of calculation circuit 132.

[0057] The frequency of the periodic signal delivered to the second output of PLL 120 can depend on the components of PLL 120, and for example, on the operating frequency of the oscillator present in PLL 120. For example, the frequency of the received signal and the frequency of the input signal of transmission circuit 116 can be equal to 13.56MHz, while the frequency of the periodic signal delivered to the second output of PLL 120 can be approximately 868MHz (64*13.56MHz).

[0058] Therefore, the measurement circuit is configured to measure the phase difference between the input signal of the transmission circuit and the delayed signal via counting, the phase difference representing the delay δ. TX The result of this count represents this phase difference, and thus this delay δ. TX The delay δ TX In particular, it depends on the PVT variation of the components of the transmission circuit 116 and the amplitude of the received signal RFI.

[0059] exist Figure 2 In the example, the generation delay δ TXThe different elements and components of the transmission circuit 116 are represented by a single component labeled 135. In this first example of device 100, the transmission circuit 116 also includes a controlled switch 137 having an output corresponding to the output of the transmission circuit 116. The output of component 135 is coupled to the input of the controlled switch 137 and the second input of circuit 128. According to the control signal applied to the controlled switch 137 (in... Figure 2 The value of (referred to as "EN") determines whether the signal RFO is delivered or not at the output of the transmission circuit 116.

[0060] During operation of device 100, switch 137 is first controlled to be in an off state so that signal RFO is not delivered at the output of transmission circuit 116; that is, transmission circuit 116 does not deliver a modulation signal. The signal obtained at the output of component 135 is injected only into the measurement circuit to calculate or measure delay δ. TX The phase shift value calculated by PLL 120 (in...) Figure 2 China is called After the input signal is applied to the transmission circuit 116, the switch 137 can be controlled in such a way that it is turned on and the modulation signal RFO is transmitted from the output of the transmission circuit 116. The modulation signal RFO obtained at the output of the transmission circuit 116 is effectively phase-shifted to compensate for the delay δ. TX (Use the indicator "-δ" at the output of circuit 132) TX (This refers to compensation).

[0061] As a variation, the function performed by the measurement circuit can be achieved by using different circuits and components than those described above. Additionally, one or more different components of the controlled switch 137 described above can be used to perform a similar function, namely, to transmit or not transmit the signal RFO from the output of the transmission circuit 116.

[0062] Previous regarding Figure 1 The features and variations described in device 100 can be applied according to Figure 2 The device 100 shown is the first example shown.

[0063] The following will combine Figure 3 A second example describing device 100. Figure 3 In this document, only portions of the components and circuitry of device 100 are shown and described below. For example, with Figure 1 compared to, Figure 3 The antenna 102 and circuit 104 of device 100 are not shown in the diagram.

[0064] In the transmission circuit 116 of the device 100 according to the second example, there is no controlled switch 137, and whether the output of the transmission circuit 116 is interrupted is directly controlled by the control signal "EN" applied to component 135.

[0065] In this second example, the transmission circuit 116 includes a delay circuit 139 that replicates the delay δ caused by the different elements and components of the transmission circuit 116 and represented by component 135. TX The input of the delay circuit 139 is coupled to the input of the transmission circuit 116, thereby coupling to the first output of the PLL 120, and the output of the delay circuit 139 is coupled to the second input of the circuit 128.

[0066] During operation of device 100, component 135 is first controlled (via signal "EN") such that signal RFO is not delivered at the output of transmission circuit 116, i.e., transmission circuit 116 does not deliver the modulated signal. The signal obtained at the output of delay circuit 139 is injected into the measurement circuit, thereby enabling the calculation of delay δ. TX After PLL 120 applies the calculated phase shift value to the input signal of transmission circuit 116, component 135 can be controlled such that the RFO modulated signal is transmitted to the output of transmission circuit 116. The RFO modulated signal obtained at the output of transmission circuit 116 is effectively phase-shifted to compensate for the delay δ. TX (indicated by the "-δ" at the output of circuit 132) TX (This refers to compensation).

[0067] In addition, one or more different components of the aforementioned delay circuit 139 can be used to perform a similar function, namely, to replicate the transmission delay of the transmission circuit 116.

[0068] Previous regarding Figure 1 or Figure 2 The features and variations described in device 100 can be applied according to Figure 3 The device 100 shown is the second example shown.

[0069] Figure 4 The steps of an example of a method for device 100 to communicate with reader 200 are illustrated schematically.

[0070] Device 100 may be in an inactive state (step 400).

[0071] During step 402, device 100 verifies whether a magnetic field corresponding to the magnetic field emitted by the reader is detected.

[0072] In the absence of such a magnetic field, device 100 remains inactive (return to step 400).

[0073] In the presence of this magnetic field, a first clock signal is delivered by receiving circuit 110, which receives the received signal of the magnetic field from source-free antenna 102 as input. PLL 120 is activated and then locked to this first clock signal (step 404). This locking of the PLL ensures a fixed and known frequency of the oscillator, for example, equal to 64*13.56MHz, thereby enabling an accurate time reference for measurement.

[0074] The received power is measured to determine the coupling coefficient between the reader 200 and the device 100 (step 406). For example, using... Figures 1 to 3 The component not shown is capable of performing the measurement of received power using an analog-to-digital converter (ADC), the output of which is coupled to a digital circuit configured to analyze the amplitude of the received signal.

[0075] Based on the amplitude measured in the previous step, the power of elements 135 and 139 can be preprogrammed to apply sufficient power to the modulation signal RFO to respond to the reader 200 (step 408).

[0076] Then execute the delay δ TX The measurement is performed to remove the phase shift corresponding to the set point of PLL 120 (step 410). Therefore, the delay of the modulated signal caused by the amplitude of the transmission circuit 116 and the received signal is compensated in the signal applied at the input of the transmission circuit 116.

[0077] Then, a signal RFO that is in phase with the field of the reader 200 is obtained at the output of the transmission circuit 116 and applied to the antenna 102, thereby enabling communication between the device 100 and the reader 200 (step 412).

[0078] A second example of device 100 is combined below. Figure 5 Describe it. In Figure 5 Only portions of the components and circuitry of device 100 are shown and described below. (In conjunction with the preceding text) Figure 3 Compared to the described device 100, Figure 5 An example of PLL120 is shown in detail.

[0079] exist Figure 5 In the example, PLL 120 includes a counter (C) 140, an oscillator (O) 142, a filter (F) 144, a subtractor 146, and an adder 148.

[0080] In this example, counter 140 includes a clock input coupled to the output of receiver circuit 110 and a data input coupled to the output of oscillator 142 (which is related to the previous...). Figure 3 The second output of the described PLL 120 corresponds to the output of the subtractor 146, which is coupled to the negative input and has the count value delivered thereon. The counter 140 also delivers the input signal of the transmission circuit 116 to another output.

[0081] Target phase value (referred to as This value is applied to the positive input of subtractor 146. Taking into account delays caused by the different components and circuitry of device 100, but disregarding delays caused by PVT variations in transmission circuit 116 and the amplitude of the received signal, this value... It can correspond to a predetermined value, which is stored, for example, in a register of device 100, and, for example, corresponds to a desired phase shift.

[0082] The output of subtractor 146 is coupled to the first input of adder 148, and the phase shift value... It is applied to the second input of adder 148.

[0083] The output of adder 148 is coupled to the input of filter 144, and the output of filter 144 is coupled to the input of oscillator 142.

[0084] According to the example, oscillator 142 can be a digitally controlled oscillator (DCO) type.

[0085] According to the example, the frequency of the periodic signal delivered by the oscillator 142 can be approximately 868MHz (64*13.56MHz), and the frequency of the input signal of the transmission circuit 116 delivered by the counter 140, as well as the frequency of the received signal and the frequency of the first clock signal, can be 13.56MHz.

[0086] As a variant, PLL 120 may include components similar to those described above and Figure 5 The circuits and / or components shown are different from those shown.

[0087] Figure 6 An example embodiment of counter 140 is shown in the figure.

[0088] In this example, counter 140 includes input terminal 149, to which the output signal of oscillator 142 is applied. Figure 6In this example, counter 140 also includes a plurality of frequency dividers 150, which are coupled in series with each other such that the output of each of these frequency dividers is coupled to the clock input of the next frequency divider. In this example, the output signal of oscillator 142 is applied to the clock input of the first frequency divider 150. Additionally, the output signal of one of the frequency dividers 150 corresponds to the input signal of transmission circuit 116. In this example, frequency divider 150 is configured to divide the frequency of the signal received at its input by a factor of 2. Therefore, in the described example, assuming that the ratio of the frequency of the periodic signal delivered by oscillator 142 to the frequency of the input signal of transmission circuit 116 is equal to 64, then the input signal of transmission circuit 116 obtains (2) at the output of the sixth frequency divider 150. 6 =64). In addition, in a specific configuration, each frequency divider 150 configured to divide the frequency of the received signal at its input by a factor of 2 can be formed by a D flip-flop, the output of which is fed back to its input via an inverter.

[0089] In this example, counter 140 also includes multiple triggers 152. Figure 6 There are three D flip-flops (152 in total), which are coupled in series with each other such that the output of each flip-flop 152 is coupled to the data input of the next flip-flop 152. The output signal of the oscillator 142 is applied to the clock input of each flip-flop 152. A first clock signal delivered by the receiving circuit 110 is applied to the data input of the first flip-flop 152. These flip-flops 152 enable the avoidance of metastability in the counter 140.

[0090] In the example described, counter 140 also includes other D flip-flops 154, which are coupled in series such that their clock inputs are coupled to each other. The first of these flip-flops 154 receives the output signal of the last flip-flop 152 at its clock input and the output signal of the oscillator 142 at its data input. The other flip-flops 154 receive the output signal of the frequency divider 150 at their data inputs. The output signals of the flip-flops 154 collectively form a counting signal (in...). Figure 6 The count signal, referred to as "cnt_out" in this example, is encoded in binary form (the output signal of each flip-flop 154 ​​corresponds to one bit of this count signal).

[0091] As a variant, counter 140 can be composed of the components described above and Figure 6 The elements and / or components shown are different elements and / or components.

[0092] Figure 7 An example embodiment of the counting trigger circuit 128 and the counter 130 is shown. Figure 8 The diagram also illustrates the process of determining the input signal to be applied to the transmission circuit 116 to compensate for the delay δ. TX Timing diagrams of the signals used in these circuits 128 and 130 during the phase shift period.

[0093] exist Figure 7 and Figure 8 In Chinese, the following headings are used:

[0094] SG_FIRST: The output signal of PLL 120, which corresponds to the input signal of transmission circuit 116;

[0095] SG_SECD: The output signal of transmission circuit 116, i.e., including delay δ TX ;

[0096] Window: Counting trigger signal;

[0097] WINDOW_EN: A signal used to enable the counter trigger circuit 128;

[0098] DCO: Output signal of oscillator 142;

[0099] Gated DCO: Figure 7 The output signals of the gate and counter 130 shown;

[0100] DFLL_counter: Output signal of counter 130;

[0101] Delay_meas_done: A signal delivered at the output of circuit 128 that indicates the counting is complete and can be read at the output of circuit 130;

[0102] RN: A signal that resets the D flip-flop when its value is 0 and allows the D flip-flop to operate on every clock edge when its value is 1; and

[0103] Rni: Measurement completion indication signal.

[0104] exist Figure 7 In the diagram, box “Dff” corresponds to a D flip-flop, and box “ / 2” corresponds to a frequency divider with a division factor of 2.

[0105] Figure 7 The operational details of circuits 128 and 130 shown are not described herein, but those skilled in the art will understand them based on... Figure 7 The components and wiring shown, and based on Figure 8 Timing diagrams are used to understand the operation of these circuits. Additionally, the amplitude and time intervals of different parts of these signals are analyzed. Figure 8 The signals in the timing diagram are schematically shown and are disproportionate to each other.

[0106] In various examples, for each use of the device in communication with the reader, the provided device 100 enables compensation for delays caused by variations in the PVT of the transmission circuit 116 of device 100 and by the amplitude of the received signal received at the input of the receiving circuit 110. Different elements of device 100 may specifically allow: synchronization of a clock signal (the first clock signal described above) with the received signal, such as a square wave signal with no delay variation, and the received signal, such as a sine wave signal with variable amplitude; measurement of the delay between the input and output signals of the transmission circuit 116; and automatic measurement and correction of delays occurring in the device using a PLL as an accurate time reference.

[0107] In all examples, the provided devices facilitate contactless communication between the device and the reader, and the authorized devices have small antennas and / or low power and / or a large distance between the device and the reader.

[0108] In all examples, delay compensation can be performed via the device without using an external device to measure the delay, and / or without delivering one or more measurement signals as output, because the compensation can be performed within the device.

[0109] In all examples, the device can include a counter to automatically perform delay measurements.

[0110] In all examples, due to the implementation of delay compensation, the phase of the signal transmitted by the device remains stable even when the amplitude of the magnetic field received by the device changes, resulting in magnetic fields with significantly different amplitude levels that are distinct from each other.

[0111] In all examples, a delay δ may be performed even after the transmission signal RFO is transmitted in transmission circuit 116. TX The measurement made it possible to improve this delay δ TX Measurement.

[0112] In the above description, device 100 corresponds to a device for contactless communication via active load modulation, which is in card emulation mode during communication with a reader. Device 100 may have functions other than those described above. For example, device 100 may correspond to a cellular phone or a connected object (such as a watch).

[0113] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations can be combined, and other variations will occur to those skilled in the art.

[0114] Finally, based on the functional indications given above, the actual implementation of the described embodiments and variations is within the capabilities of those skilled in the art.

Claims

1. A device for contactless communication by active load modulation, comprising: a receiving circuit having an input configured to receive a receive signal derived from a magnetic field intended to be received by the antenna; a transmission circuit having an output coupled to the antenna and configured to generate a modulated signal in phase with the received signal intended for delivery to the output; as well as A compensation circuit is configured to compensate for a delay of a modulated signal caused by a transmission circuit and an amplitude of a received signal, wherein the compensation circuit determines a phase shift value to be applied to an input signal of the transmission circuit to compensate for the delay.

2. The apparatus of claim 1 , further comprising a phase-locked loop configured to receive as input the first clock signal delivered at the output of the receiving circuit and the phase shift value and to deliver the input signal of the transmitting circuit on the first output.

3. The apparatus according to claim 2, wherein the compensation circuit comprises a circuit configured to measure a phase difference between an input signal of the transmission circuit and a delayed signal corresponding to the input signal of the transmission circuit delayed by the delayed signal, and wherein the circuit configured to measure the phase difference comprises at least: a count trigger circuit comprising a first input terminal configured to receive at least an input signal of the transmission circuit, and a second input terminal configured to receive at least a delayed signal, wherein the count trigger circuit is configured to output a count trigger signal having a first value for a time period equal to the delay and having a second value different from the first value outside the time period; a counter including a clock input coupled to the output of the count trigger circuit, and a data input coupled to the second output of a phase locked loop providing a periodic signal having a frequency equal to a multiple of the frequency of the input signal to the transmission circuit; as well as A calculation circuit is configured to determine a phase shift value according to the value of the count signal delivered by the counter.

4. The apparatus of claim 3 , wherein the transmission circuit comprises a control input configured to receive a signal that controls selective transmission of a signal at an output of the transmission circuit, and comprises a delay circuit having an input coupled to the input of the transmission circuit and an output coupled to a second input of the counting trigger circuit, wherein the delay circuit is configured to apply a delay having a value equal to the delay due to the transmission circuit.

5. The apparatus according to claim 1, wherein the compensation circuit comprises a phase difference circuit configured to measure a phase difference between an input signal of the transmission circuit and a delayed signal corresponding to the input signal of the transmission circuit delayed by the delayed signal.

6. The apparatus of claim 5, wherein the transmission circuit comprises a controlled switch having an output terminal corresponding to the output terminal of the transmission circuit.

7. The device of claim 1, wherein the receiving circuit comprises: a variable gain amplifier having an input configured to receive a receive signal; as well as The converter circuit is configured to convert the sinusoidal signal into a square wave signal, wherein the converter circuit includes an input terminal coupled to the output terminal of the variable gain amplifier, and an output terminal corresponding to the output terminal of the receiving circuit.

8. A method for contactless communication between a reader and a device, comprising the steps of: Detecting magnetic fields through equipment; When a magnetic field is detected by the device, transmitting a first clock signal by a receiving circuit of the device, the receiving circuit receiving as input a received signal originating from the magnetic field; measuring by a compensation circuit of the device and compensating in a signal applied at an input of a transmission circuit of the device a delay of the modulated signal due to the transmission circuit and the amplitude of the received signal, the compensated delay being dependent on the amplitude of the received signal and a target amplitude of the modulated signal delivered at an output of the transmission circuit; as well as The modulated signal is applied to the antenna via the device's transmission circuitry.

9. The method according to claim 8, further comprising, after transmitting the first clock signal, starting a phase-locked loop and locking it to the first clock signal, and outputting an input signal of the transmission circuit from the phase-locked loop.

10. The method of claim 8, further comprising, between the transmission of the first clock signal and the application of the phase shift value: measuring received power; and The power of components of the transmission circuit is preprogrammed according to the measured received power.

11. The method of claim 8, wherein the compensation circuit comprises a circuit for measuring a phase difference between an input signal of the transmission circuit and a delayed signal corresponding to the input signal of the transmission circuit delayed by the delay, and wherein the transmission circuit comprises a controlled switch having an output terminal corresponding to the output terminal of the transmission circuit, the method further comprising, before measuring and compensating for the delay, applying a control signal to a control input terminal of the controlled switch of the transmission circuit or one of the control input terminals of the transmission circuit in such a manner that no signal is delivered at the output terminal of the transmission circuit.

12. The method of claim 11 , further comprising, after measuring and compensating for the delay, applying a control signal to a control input of a controlled switch of the transmission circuit or to one of the control inputs of the transmission circuit in such a way that the modulated signal is delivered at the output of the transmission circuit.

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