Near field communication device and method of operation

Abstract

According to a first aspect of the present disclosure, there is provided a near field communication (NFC) apparatus, comprising: a wake-up unit configured to: transmit one or more radio frequency (RF) pulses; detecting a load condition change occurring in response to transmitting the RF pulse; waking up one or more functional components of the NFC device if the load condition change exceeds a predefined wakeup threshold; and a calibration state determination unit configured to determine a calibration state of the wake-up unit by detecting whether the load condition change is within a predefined range below the wake-up threshold. According to a second aspect of the present disclosure, a corresponding method of operating an NFC device is envisaged.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a near field communication device. Furthermore, the present disclosure relates to a corresponding method of operating a near field communication device. BACKGROUND

[0002] Wireless energy harvesting based on radio frequency (RF) technology is becoming more widely used to power electronic devices and to charge batteries. In particular, wireless charging using near field communication (NFC) is a deployment technology for small accessory charging. Small accessories include, for example, wearables, human interface devices, and audio devices. Implementations can follow the NFC Forum Wireless Charging (WLC) specification, or a proprietary system based on a traditional NFC communication scheme.

[0003] A system for wireless charging typically consists of a primary device, usually referred to as a "WLC Poller" (WLC-P), magnetically coupled to a secondary device, usually referred to as a "WLC Listener" (WLC-L). The secondary device is powered by a battery that can be recharged by the primary device using RF coupling, in particular NFC coupling. It should be noted that the primary device can also be battery powered. Furthermore, the primary device (e.g., a reader) can perform a presence check to poll a counterpart device using a technology referred to as Low Power Card Detection (LPCD). LPCD uses short RF "pings" (i.e., RF pulses) to sense small load variations to detect a counterpart device, such as a tag or a smart card, that is approaching. SUMMARY

[0004] According to a first aspect of the present disclosure, there is provided a near field communication (NFC) device comprising: a wake-up unit configured to: transmit one or more radio frequency, RF, pulses; detect a load condition change occurring in response to transmitting the RF pulses; wake up one or more functional components of the NFC device in case the load condition change exceeds a predefined wake-up threshold; and a calibration status determination unit configured to determine a calibration status of the wake-up unit by detecting whether the load condition change is within a predefined range below the wake-up threshold.

[0005] In one or more embodiments, the calibration status determination unit is additionally configured to: increment a count indicating a number of times the load condition change is within the predefined range; determine that the calibration of the wake-up unit is outdated in case the count exceeds a predefined count threshold.

[0006] In one or more embodiments, the calibration status determination unit is configured to reset the count in case the functional components have been woken up by the wake-up unit and a communication has been established with an external communication counterpart device.

[0007] In one or more embodiments, the calibration status determination unit is configured to subtract a configurable number from the count if the wake-up unit has already woken up the functional component and no communication has been established with an external communication counterpart device after a predefined amount of time.

[0008] In one or more embodiments, the calibration status determination unit is further configured to initiate a recalibration of the wake-up unit if it is determined that the calibration of the wake-up unit is outdated.

[0009] In one or more embodiments, the calibration status determination unit is configured to reset the count when or after the recalibration of the wake-up unit is initiated.

[0010] In one or more embodiments, the calibration state determination unit is configured to detect a load condition change within the predefined range if the load condition change is greater than a low threshold and less than a high threshold, wherein the low threshold and the high threshold are less than a wake-up threshold.

[0011] In one or more embodiments, load condition variations include variations in the amplitude of the output signal of the analog-to-digital converter (ADC) included in the NFC device.

[0012] In one or more embodiments, the NFC device is implemented as a wireless charging poller (WLC-P).

[0013] According to a second aspect of this disclosure, a method for operating a near-field communication (NFC) device is envisioned, comprising: transmitting one or more radio frequency (RF) pulses by a wake-up unit included in the NFC device; detecting a change in load conditions occurring in response to transmitting the RF pulses by the wake-up unit; waking up one or more functional components of the NFC device by the wake-up unit if the change in load conditions exceeds a predefined wake-up threshold; and determining the calibration state of the wake-up unit by a calibration state determination unit included in the NFC device by detecting whether the change in load conditions is within a predefined range below the wake-up threshold.

[0014] In one or more embodiments, the method further includes: incrementing a count indicating the number of times the load conditions change within the predefined range by a calibration state determination unit; and determining, if the count exceeds a predefined count threshold, that the calibration of the wake-up unit is outdated.

[0015] In one or more embodiments, the calibration status determination unit resets the count when the wake-up unit has woken up the functional component and established communication with the external communication counterpart device.

[0016] In one or more embodiments, the calibration status determination unit subtracts a configurable number from the count if the wake-up unit has woken up the functional component and if no communication has been established with an external communication counterpart device after a predefined amount of time.

[0017] In one or more embodiments, the calibration status determination unit initiates a recalibration of the wake-up unit if it has been determined that the calibration of the wake-up unit is outdated.

[0018] In one or more embodiments, the calibration status determination unit resets the count when or after initiating a recalibration of the wake-up unit. Attached Figure Description

[0019] The embodiments will be described in more detail with reference to the accompanying drawings.

[0020] Figure 1A An example of a wireless charging system is shown.

[0021] Figure 1B A graph showing the change in WLC-P current consumption over time is shown.

[0022] Figure 2A The measurement of the analog-to-digital converter (ADC) output used to derive the detection metric is shown.

[0023] Figure 2B A graph showing the change in detection metrics and the distance between WLC-L and WLC-P over time is shown.

[0024] Figure 3A An illustrative embodiment of an NFC device is shown.

[0025] Figure 3B An illustrative embodiment of a method for operating an NFC device is shown.

[0026] Figure 4 The outdated calibration status derived from the detection metric is shown.

[0027] Figure 5 A flowchart of the calibration status monitoring process is shown.

[0028] Figure 6 A graph showing the changes in detection metrics, distance of WLC-L from WLC-P, and detection zone count over time is presented. Detailed Implementation

[0029] Figure 1AAn example of a wireless charging system is shown. In an NFC system, a proximity coupling device (PCD) (i.e., a reader or wireless charging device) can be magnetically coupled to a proximity integrated circuit card (PICC) (i.e., a tag or power receiving device). The PCD and PICC exchange information by modulating the radio frequency (RF) carrier signal emitted by the PCD. The NFC Wireless Charging (WLC) standard published by the NFC Forum extends the purely communicative use of NFC to wireless charging. In this case, WLC-P can use an NFC communication link to charge a small NFC-enabled device called WLC-L. Therefore, the NFC specification is used to control wireless power charging using the same antenna and communication link. Figure 1A Typical NFC systems including WLC-P 102 and WLC-L 104 are shown; WLC-L104 can be implemented, for example, as a smartwatch or an NFC-enabled ring.

[0030] Figure 1B A graph 106 shows the variation of WLC-P current consumption 108 during wake-up over time 110. To conserve energy, the WLC-P enters a low-power mode (e.g., "standby") when idle. In configurable time instances (e.g., 1-10 Hz), the WLC-P may become "active" to emit short RF pulses to detect objects nearby. Nearby NFC devices may cause the WLC-P's antenna and matching network to become detuned, which can be observed through the WLC-P's RF modem. This change in load conditions, or simply "load change," can be detected and compared to a reference condition. This process is called Low-Power Card Detection (LPCD). If the LPCD detects a peer device, the WLC-P attempts to initiate communication with a potential WLC-L using active polling for NFC communication at a frequency of 13.56 MHz. A typical LPCD RF pulse lasts approximately tens to hundreds of microseconds, but active polling lasts tens of milliseconds. Because LPCD is a much shorter process than communication initialization, WLC-P devices can remain in standby mode for longer periods of time and generate lower average current consumption compared to continuous polling of the other device. Figure 1B This process is illustrated.

[0031] NFC communication devices typically use the concept of I / Q modulators and demodulators for data transmission. A typical receiver (RX) chain consists of a 13.56MHz sampling mixer, DC offset correction circuitry, a baseband amplifier, and an analog-to-digital converter (ADC) stage. Therefore, after the RF signal is demodulated, the signal at the ADC is a DC-like signal because WLC-L does not perform passive load modulation, and only load changes in the RF field are observed.

[0032] A typical WLC LPCD sequence operates in two phases. The first phase is the calibration phase, during which RF pulses are emitted in a known no-load environment. Therefore, no peer device is nearby. The ADC output is trimmed by adjusting the DC offset (DCO) correction until it is equal to a specified calibration target, typically defined as the midpoint of the ADC's full-scale range (FSR). The obtained DCO correction control value is saved and loaded during polling. The second phase is the polling phase, during which the WLC-P emits short RF pulses at configurable time instances or when triggered by an external event. Nearby peer devices detune the antenna and affect the magnetic resonance circuit (RLC network, antenna). As a result, the amplitude and phase of the RX chain input change. When the DCO control value is fixed, the ADC output changes and deviates from the calibration target. If the distance of the ADC output relative to the calibration target exceeds a predefined threshold, the device wakes up to initiate communication. This threshold can be referred to as the peer device presence threshold. The presence threshold of the other device is defined as the condition that WLC-P wakes up when WLC-P and WLC-L are at a desired distance (e.g., typically 1 to 10 mm apart).

[0033] In NFC-based WLC applications, a calibration process is typically performed once at the factory, and the DCO correction value is stored in non-volatile memory. This calibration is performed on each device before shipment. When high load variations are observed, a single factory calibration is sufficient. It should be noted that other NFC applications requiring very high LPCD detection sensitivity (e.g., detecting the distance to a peer device) can use LPCD runtime calibration, which is performed each time an LPCD sequence is initiated. However, a drawback of runtime calibration is that it can only detect relative load variations. Therefore, a polling device cannot detect whether the current load state is "no load" (e.g., no nearby device) or whether a peer device is present that is advantageous for the WLC application. For example, a polling device might fail to detect a fully charged accessory still on the charger.

[0034] Additionally, the calibration target is defined as making the entire dynamic range of the ADC usable. However, due to several field conditions, calibration can become outdated, meaning that observed ADC readings will drift relative to calibrated readings under the same load conditions. Example situations include changes in RX chain parameters (e.g., BBA gain, DC offset, RLC components of antenna matching) due to aging or extreme temperature variations, and mechanical changes in the antenna or accessories covering the antenna (e.g., cover or shielding of a handheld device).

[0035] Figure 2A and Figure 2BMeasurement 200, used to derive the detection metric from the analog-to-digital converter (ADC) output, is shown, along with a graph 206 displaying the changes in the detection metric 208 and the distance 210 from WLC-L to WLC-P over time 212. Specifically, Figure 2A and Figure 2B This illustrates how outdated calibration can affect the desired wake-up distance when LPCD technology is applied. In the example shown, the device needs to wake up when WLC-P and WLC-L are a considerable distance apart. This early wake-up can lead to unnecessary false wake-ups and an undesirable increase in average power consumption. For simplicity, Figure 2A The calibration target is set to 0 LSB for both I channel 202 and Q channel 204, but those skilled in the art will understand that this calibration target can be chosen arbitrarily. Furthermore, in this example, the detection metric 208 is the ADC amplitude. However, those skilled in the art will understand that other suitable detection metrics are possible, such as (in addition to) ADC-I and ADC-Q, i.e., the outputs of the ADCs in I channel 202 and Q channel 204. The choice of a suitable detection metric typically depends on the specific use case.

[0036] Figure 2B The impact of outdated LPCD calibration on wake-up performance is illustrated. Initially, the calibration is up-to-date, and wake-up works as expected. However, after a period (A), the calibration becomes outdated. Therefore, the approaching WLC-L results in an early wake-up (shortly before B). Conversely, outdated calibration can also cause a very late wake-up. Early wake-up can lead to higher power consumption and thus shorter battery life for the end-user device. When wake-up is late, or when no wake-up is performed at all, accessories for the end-user device cannot charge, leading to end-user dissatisfaction. In the worst case, outdated calibration can even cause missed wake-ups, depending on the detection metric used. To mitigate the impact of outdated calibration on LPCD performance, it is possible to avoid using the full dynamic range of the ADC and instead use a weaker wake-up threshold to detect potential adversaries at the desired detection distance, even under extreme temperature conditions and after prolonged operation.

[0037] This discussion focuses on an NFC device and a corresponding method for operating it, which facilitates the detection of outdated calibration states of the wake-up unit within the NFC device. This, in turn, enables on-site recalibration to be initiated when appropriate, mitigating the impact of outdated calibration on the wake-up unit's performance while still allowing for accurate wake-up threshold definition using the full dynamic range of the ADC. Consequently, the end-user experience can be improved through more reliable detection of the communicating peer device and extended battery life due to lower current consumption. Advantageously, the NFC device can be implemented as a Wireless Charging Poller (WLC-P).

[0038] Figure 3A An illustrative embodiment of an NFC device 300 is shown. The NFC device 300 includes a wake-up unit 302 and a calibration state determination unit 304 operatively coupled to each other. The wake-up unit 302 is configured to send one or more RF pulses, detect changes in load conditions occurring in response to the sending of the RF pulses, and wake up one or more functional components of the NFC device 300 if the changes in load conditions exceed a predefined wake-up threshold. It should be noted that the term "functional component" can refer to any component of the NFC device 300 other than the wake-up unit 302 and the calibration state determination unit 304, which performs functions typically performed by the NFC device (e.g., performing contactless payments, fee transactions, or wireless charging). Furthermore, the calibration state determination unit 304 is configured to determine the calibration state of the wake-up unit 302 by detecting whether the changes in load conditions are within a predefined range below the wake-up threshold. In this way, outdated calibration states of the wake-up unit 302 can be easily determined, allowing recalibration of the wake-up unit 302 to be initiated when the NFC device 300 is used in the field. It should be noted that although the wake-up unit 302 and the calibration status determination unit are shown as separate units, they can also be integrated into a single physical unit. Furthermore, the wake-up unit 302 can be a unit specifically configured to perform the LPCD process.

[0039] In one or more embodiments, the calibration state determination unit is further configured to increment a count indicating the number of times load conditions change within the predefined range, and to determine that the wake-up unit's calibration is outdated if the count exceeds a predefined count threshold. In this way, it is easy to determine that the wake-up unit's calibration is outdated. More specifically, an outdated calibration of the wake-up unit represents a specific calibration state of the wake-up unit, and using the aforementioned count helps to determine that the wake-up unit is in this state.

[0040] In one or more embodiments, the calibration status determination unit is configured to reset the count when the wake-up unit has woken up the functional component and established communication with an external communication counterpart. In this way, it can be easily ensured that the determination of the calibration status of the wake-up unit, particularly the determination of whether the wake-up unit's calibration is outdated, restarts after a correct wake-up event (i.e., after a "real" wake-up event). Furthermore, in one or more embodiments, the calibration status determination unit is configured to subtract a configurable number from the count when the wake-up unit has woken up the functional component and no communication has been established with an external communication counterpart after a predefined amount of time. This may provide additional degrees of freedom. In particular, in the case of an unsuccessful attempt to communicate, this means that the antenna is detuned to the point of violating the wake-up threshold. However, it is impossible to determine whether this detuning is caused by outdated calibration, the actual counterpart device, or, for example, a metal plate. Therefore, if a configurable number can be subtracted from the recalibration count, unnecessary recalibration can be avoided.

[0041] In one or more embodiments, the calibration status determination unit is further configured to initiate a recalibration of the wake-up unit if it has been determined that the calibration of the wake-up unit is outdated. This facilitates online recalibration of the wake-up unit. It should be noted that the term "online" refers to recalibration performed while the NFC device is being used, while "offline" refers to recalibration performed at the factory (i.e., before the NFC device is sold). In one or more embodiments, the calibration status determination unit is configured to reset the count when or after initiating a recalibration of the wake-up unit. This easily ensures that the determination of the calibration status of the wake-up unit, particularly the determination of whether the calibration of the wake-up unit is outdated, can be restarted after the recalibration of the wake-up unit.

[0042] In one or more embodiments, the calibration status determination unit is configured to detect a load condition change within a predefined range, where the load condition change is greater than a low threshold and less than a high threshold, and the low threshold and the high threshold are less than a wake-up threshold. This results in a practical implementation according to which load condition changes within the aforementioned predefined range can be easily detected. Furthermore, in one or more embodiments, the load condition change includes a change in the amplitude of the output signal of the analog-to-digital converter (ADC) included in the NFC device. The ADC amplitude is a suitable detection metric for determining whether the calibration of the wake-up unit is outdated. However, those skilled in the art will understand that other detection metrics, such as the amplitude of the ADC-I reading and / or the amplitude of the ADC-Q reading, can also be used.

[0043] Figure 3BAn illustrative embodiment of a method 306 for operating an NFC device is shown. Method 306 includes the following steps: At 308, a wake-up unit included in the NFC device sends one or more RF pulses. At 310, the wake-up unit detects a change in load conditions occurring in response to the sending of the RF pulses. Furthermore, at 314, a calibration state determination unit included in the NFC device determines the calibration state of the wake-up unit by detecting whether the change in load conditions is within a predefined range below a wake-up threshold. (See reference...) Figure 3A As described in the corresponding NFC device, method 306 helps determine the outdated calibration state of the wake-up unit, enabling a recalibration of the wake-up unit to be initiated when the NFC device is used in the field.

[0044] Typically, when there is no suitable counterpart device nearby, an NFC device enters a low-power mode. However, NFC-enabled devices periodically emit RF pulses to detect changes in RF field load and antenna detuning. This process, known as tag detection or low-power card detection (LPCD), is used by NFC-based wireless charging devices. Once the LPCD process, performed by the wake-up unit, detects a counterpart device near the NFC device, communication with that counterpart device is initiated. Initiating communication with a counterpart device is a much longer process than LPCD, thus requiring significantly more power. If the LPCD calibration becomes outdated relative to its original "no-load" condition target, LPCD performance degrades. This means false wake-ups may occur, leading to increased overall power consumption. In other cases, the counterpart detection volume decreases due to reduced detection sensitivity. Typically, a WLC LPCD calibration is performed once per device at the factory. This is feasible because significant RF load changes are observed in the WLC.

[0045] According to this disclosure, outdated LPCD calibration status can be easily detected in the field, enabling online recalibration to be initiated to track "no-load" conditions. Performing LPCD calibration in the field eliminates the effects of temperature dependence and aging on LPCD performance. Therefore, the currently disclosed NFC device enables accurate wake-up threshold definition using the full dynamic range of the ADC. Consequently, the end-user experience can be improved through more reliable peer device detection and extended battery life due to lower current consumption.

[0046] More specifically, at least one LPCD detection metric can be monitored to detect slow changes or drifts in the LPCD calibration relative to no-load conditions, caused by factors such as device aging, extreme temperatures, or mechanical stress. Once an outdated LPCD calibration is detected, an online recalibration of the LPCD can be triggered to track the "no-load" condition. This minimizes degraded detection performance or the probability of false alarms that could lead to increased power consumption or user dissatisfaction. Monitoring may include: defining a configurable LPCD metric monitoring zone associated with slow drift in the "no-load zone," where the slow drift is less than a detection threshold of the other device; applying a count of the LPCD metric results within the defined monitored zone; and triggering LPCD recalibration if a configurable number of LPCD metric occurrences are observed within the monitored zone.

[0047] Figure 4 The outdated calibration state 400 derived from the detection metric is shown. To detect outdated calibration, two additional thresholds (i.e., two thresholds in addition to the wake-up threshold) can be defined according to this disclosure. These two additional thresholds define the monitored detection area (i.e., the detection region). In this example, the LPCD detection metric is the ADC amplitude, such as sqrt(ADC-I). 2 +ADC-Q 2 Therefore, the detection metric can be visualized as a circle on the Cartesian plane. However, those skilled in the art will understand that different detection zones can also be formed. Under no-load conditions, if calibration is outdated, the ADC output will gradually deviate from the original target. It should be noted that in this example, for the sake of simplicity in visualization, the target value ADC-I = ADC-Q = 0 is assumed. However, different target values ​​can be chosen depending on the application design. According to this disclosure, if the result is within a predefined monitored region between the calibration target and the wake-up threshold, the count can be incremented.

[0048] Figure 5 A flowchart of the calibration status monitoring process 500 is shown. Specifically, Figure 5 A flowchart illustrating how outdated calibration can be detected is shown. After performing LPCD RF pulse transmission and measurement, the WLC-P can calculate the LPCD detection metric. If the detection metric is higher than a configurable peer device presence threshold (i.e., the wake-up threshold mentioned above), communication with the WLC-L can be initiated. If communication has been established, the count (outdated_cal_cnt) can be reset upon detection of a load condition. If no communication is possible, LPCD polling can continue. However, this is an erroneous wake-up event. In the case of an erroneous wake-up event, a configurable number can be subtracted from outdated_cal_cnt (not shown). As explained above, this can provide additional degrees of freedom.

[0049] If the LPCD metric falls below a configurable threshold for the presence of a peer device, it can be checked whether the LPCD detection metric is within the defined monitored detection area. If so, the count `outdated_cal_cnt` can be incremented. If this count exceeds a defined threshold (`cp_detect_th`), a recalibration can be initiated, and the count `outdated_cal_cnt` can be reset to zero. One advantage is that the measurement results are available regardless, so only the count `outdated_cal_cnt` of the additional area should be added. Furthermore, the method is flexible and can be easily optimized for specific use cases because the monitored detection area can be easily configured.

[0050] Figure 6 A graph 600 shows the changes in detection metric 602, distance 604 between WLC-L and WLC-P, and detection zone count 606 over time 608. Consistent LPCD performance can be ensured through detection outdated calibration because the distance between the "no-load" condition and the detection threshold of the other device can be restored to its original state. Figure 6 The diagram illustrates how LPCD recalibration causes the ADC output to return to the calibration target (A). A monitoring area for monitoring detection metric 602 is shown below the wake-up threshold (i.e., the threshold at which the other device is present). Once the LPCD metric enters the monitoring area, the count `outdated_cal_cnt` may increase until it exceeds the recalibration threshold `recal_th`. The wake-up threshold is exceeded once WLC-L approaches WLC-P (B), when WLC-P is at the expected distance from WLC-L (C).

[0051] It should be noted that the above embodiments have been described with reference to different subjects. In particular, some embodiments may have been described with reference to claims of the method class, while other embodiments may have been described with reference to claims of the device class. However, those skilled in the art will conclude from the foregoing that, unless otherwise indicated, any combination of features related to different subjects, particularly features of claims of the method class and features of claims of the device class, is also considered to be disclosed in this document, except for any combination of features belonging to one type of subject matter.

[0052] Furthermore, it should be noted that the drawings are schematic. Similar or identical elements are represented by the same reference numerals in different drawings. Additionally, it should be noted that, in order to provide a concise description of illustrative embodiments, implementation details that are customary to those skilled in the art may not be described. It should be understood that in the development of any such implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developer's specific objectives, such as complying with system-related and business-related constraints, which may vary from implementation to implementation. Furthermore, it should be understood that such development work can be complex and time-consuming, but is merely a routine task of design, manufacture, and production for those skilled in the art.

[0053] Finally, it should be noted that those skilled in the art should be able to devise numerous alternative embodiments without departing from the scope of the appended claims. Any reference numerals placed between parentheses in the claims should not be construed as limiting the claims. The words “comprise(s)” or “comprising” do not exclude the presence of elements or steps other than those listed in the claims. The words “a(a)” or “an(an)” preceding an element do not exclude the presence of a plurality of such elements. The measures recited in the claims can be implemented by means of hardware comprising several distinct elements and / or by means of a suitably programmed processor. In device claims enumerating several components, several of these components can be embodied by one and the same hardware. The mere fact that certain measures recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to exert an advantage.

[0054] List of reference numerals

[0055] 100 Wireless Charging System

[0056] 102 Wireless Charging Poller (WLC-P)

[0057] 104 Wireless Charging Listener (WLC-L)

[0058] 106 shows a graph illustrating the change in current consumption of the WLC-P over time.

[0059] 108WLC-P Current Consumption

[0060] 110 time

[0061] 200 Measurements using the analog-to-digital converter (ADC) output for deriving detection metrics

[0062] 202 I Channel

[0063] 204 Q channel

[0064] 206 shows the curves illustrating the changes in detection metrics and the distance between WLC-L and WLC-P over time.

[0065] 208 detection metrics

[0066] Distance from 210WLC-L to WLC-P

[0067] 212 Time

[0068] 300 NFC devices

[0069] 302 Wake-up Unit

[0070] 304 Calibration Status Determination Unit

[0071] 306 Methods for operating NFC devices

[0072] 308 sends one or more RF pulses from the wake-up unit included in the NFC device.

[0073] 310 The wake-up unit detects the change in load conditions that occurs in response to the transmission of the RF pulse.

[0074] 312 If the load condition change exceeds a predefined wake-up threshold, the wake-up unit wakes up one or more functional components of the NFC device. 314 The calibration state of the wake-up unit is determined by a calibration state determination unit included in the NFC device by detecting whether the load condition change is within a predefined range below the wake-up threshold.

[0075] 400 Outdated calibration status derived from detection metrics

[0076] 402 I Channel

[0077] 404Q channel

[0078] Flowchart of the 500 calibration status monitoring process

[0079] 502outdated_cal_cnt:=0

[0080] 504 Waiting for LPCD to trigger

[0081] 506 Load LPCD calibration

[0082] 508 sends LPCD pulses and calculates detection metrics.

[0083] 510 Detection metric > cp_detect_th 512 Initiate communication

[0084] 514 Was the communication successful?

[0085] 516 Perform communication

[0086] 518 Is the detection metric within the recalibration zone?

[0087] 520outdated_cal_cnt+=1

[0088] 522outdated_cal_cnt>recal_th524 Run LPCD recalibration

[0089] The 600 displays graphs showing the changes in detection metrics, the distance between WLC-L and WLC-P, and the number of detection zones over time.

[0090] 602 detection measurement

[0091] Distance from 604WLC-L to WLC-P

[0092] 606 Detection Zone Count

[0093] 608 Time.

Claims

1. A near-field communication (NFC) device, characterized in that, include: Wake-up unit, the wake-up unit being configured to: Send one or more radio frequency (RF) pulses; Detect changes in load conditions that occur in response to the transmission of the RF pulse; When the load condition change exceeds a predefined wake-up threshold, one or more functional components of the NFC device are woken up; as well as A calibration state determination unit is configured to determine the calibration state of the wake-up unit by detecting whether the load condition change is within a predefined range below the wake-up threshold.

2. The NFC device according to claim 1, characterized in that, The calibration status determination unit is further configured to: Increment the count indicating the number of times the load conditions change within the predefined range; If the count exceeds a predefined count threshold, the calibration of the wake-up unit is determined to be outdated.

3. The NFC device according to claim 2, characterized in that, The calibration status determination unit is configured to reset the count when the wake-up unit has woken up the functional component and communication has been established with the external communication counterpart device.

4. The NFC device according to claim 2 or 3, characterized in that, The calibration status determination unit is configured to subtract a configurable number from the count if the wake-up unit has woken up the functional component and if no communication has been established with an external communication counterpart device after a predefined time period.

5. The NFC device according to any one of claims 2 to 4, characterized in that, The calibration status determination unit is further configured to initiate a recalibration of the wake-up unit if it is determined that the calibration of the wake-up unit is outdated.

6. The NFC device according to claim 5, characterized in that, The calibration status determination unit is configured to reset the count when or after the recalibration initiated by the wake-up unit.

7. The NFC device according to any one of the preceding claims, characterized in that, The calibration state determination unit is configured to detect that the load condition change is within a predefined range when the load condition change is greater than a low threshold and less than a high threshold, wherein the low threshold and the high threshold are less than the wake-up threshold.

8. The NFC device according to any one of the preceding claims, characterized in that, The load condition change includes a change in the amplitude of the output signal of the analog-to-digital converter (ADC) included in the NFC device.

9. The NFC device according to any one of the preceding claims, characterized in that, The implementation is a wireless charging poller WLC-P.

10. A method for operating a Near Field Communication (NFC) device, characterized in that, include: One or more radio frequency (RF) pulses are sent by the wake-up unit included in the NFC device; The wake-up unit detects changes in load conditions in response to the transmission of the RF pulse; When the load condition change exceeds a predefined wake-up threshold, the wake-up unit wakes up one or more functional components of the NFC device; The calibration status of the wake-up unit is determined by the calibration status determination unit included in the NFC device by detecting whether the load condition change is within a predefined range below the wake-up threshold.

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