Near field communication device

Abstract

An NFC device includes: an amplifier that outputs a TX signal to an antenna; a phase detector that compares a phase of a recovered clock signal generated by the RX signal transmitted to the antenna with a phase of a reference clock signal to calculate a phase difference; and a clock generator that outputs the transmission clock signal to the amplifier and controls the phase of the transmission clock signal with reference to the calculated phase difference. When a field emitted by an external reader is sensed, the clock generator outputs a pre-clock signal having a random phase to the amplifier to emit a pre-TX signal prior to receiving an RX signal from the reader. The phase detector transmits, to the clock generator, an initial phase difference calculated by comparing a phase of a reflected clock signal recovered from a reflected signal of the pre-TX signal with a phase of a reference clock signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0052068 filed on April 18, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Aspects of the present inventive concept relate to a near field communication (NFC) device.

[0004] NFC technology is a communication technology that can exchange data over short distances using frequencies within a specific bandwidth, and due to its advantages (such as high security), it can be applied to various fields. Recently, near-field communication devices for providing NFC functions have been installed in various types of electronic devices, and mobile devices can use NFC functions to provide users with electronic payment functions and data exchange functions, such as transportation cards, credit cards, and coupons. In order to use the NFC function, initial setup may be required to ensure smooth communication between a device operating in reader mode and a device operating in card (e.g., card emulation) mode, and several methods have been proposed to quickly and accurately perform initial setup. Summary of the Invention

[0005] An aspect of the present inventive concept is to provide an NFC device that transmits a pre-transmission (pre-TX) signal before first receiving a receive (RX) signal from an external device operating in a reader mode, and sets an initial value of a radio frequency (RF) parameter using a reflected signal of the pre-TX signal.

[0006] According to one aspect of the present inventive concept, an NFC device includes: an amplifier configured to output a TX signal to an antenna; a phase detector configured to compare a phase of a recovered clock signal generated by an RX signal transmitted to the antenna with a phase of a reference clock signal to calculate a phase difference; and a clock generator configured to output a transmission clock signal to the amplifier and control the phase of the transmission clock signal with reference to the phase difference calculated by the phase detector, wherein, when a field transmitted by an external reader is detected, the clock generator outputs a pre-clock signal having a random phase to the amplifier before receiving the RX signal from the external reader to transmit a pre-TX signal from the amplifier, and the phase detector transmits an initial phase difference calculated by comparing a phase of a reflected clock signal recovered from a reflected signal of the pre-TX signal received at the antenna with a phase of the reference clock signal to the clock generator.

[0007] According to an aspect of the present inventive concept, an NFC device includes a clock generator configured to generate a pre-clock signal having a random phase when it is detected that a field generated by an external device is entered, an amplifier configured to transmit a pre-TX signal through an antenna in response to the pre-clock signal, and a phase detector configured to compare a reflection clock signal generated by a reflection signal of the pre-TX signal received by the antenna with a predetermined reference clock signal to calculate an initial phase difference when the reflection signal is received, wherein the clock generator adjusts an RF parameter including at least one of a frequency or a phase of a first TX signal first transmitted to the external device with reference to the initial phase difference.

[0008] According to an aspect of the present inventive concept, an NFC device includes an antenna configured to transmit a TX signal to an external device and receive an RX signal from the external device, an amplifier configured to output the TX signal to the antenna, and a clock generator configured to output a transmission clock signal corresponding to the TX signal to the amplifier before the RX signal is received from the external device, wherein the clock generator adjusts an RF parameter including at least one of a frequency or a phase of the transmission clock signal after the TX signal is transmitted to the antenna and before the RX signal is received from the external device. BRIEF DESCRIPTION OF DRAWINGS

[0009] The above and other aspects, features and advantages of the present inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a view illustrating an electronic device including an NFC device according to an embodiment.

[0011] Figure 2 is a block diagram illustrating an NFC device according to an embodiment.

[0012] Figure 3 and Figure 4 is a flowchart illustrating an operation of an NFC device according to an embodiment.

[0013] Figure 5 and Figure 6 is a view illustrating an operation of an NFC device according to an embodiment.

[0014] Figure 7 is a view illustrating an NFC device according to an embodiment.

[0015] Figure 8 is a view illustrating an operation of an NFC device according to an embodiment.

[0016] Figure 9 and Figure 10 is a view illustrating an operation of an NFC device according to an embodiment.

[0017] Figures 11 to 13 is a view illustrating an operation of an NFC device according to an embodiment.

[0018] Figure 14 is a view illustrating a time-to-digital converter included in an NFC device according to an embodiment.

[0019] Figure 15 is a block diagram illustrating an electronic device including an NFC device according to an embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, preferred embodiments of the inventive concept will be described with reference to the accompanying drawings.

[0021] Figure 1 is a view illustrating an electronic device including an NFC device according to an embodiment.

[0022] Reference Figure 1 , the electronic device 10 according to an embodiment can include a housing 11, a display 12, a camera unit 13, an input unit 14, a near field communication (NFC) device 15, and the like. Although the electronic device 10 is illustrated as a smartphone, the NFC device 15 according to an embodiment can also be applied to various other devices such as a desktop computer, a home TV, a set-top box, an electric appliance (e.g., a refrigerator, a washing machine, a dryer, an air conditioner, etc.), and the like, as well as mobile devices such as a tablet PC, a laptop computer, etc.

[0023] The NFC device 15 included in the electronic device 10 can communicate with an external device 20 using a wireless signal within a specific frequency band. As Figure 1 indicated, when the external device 20 is a device operating in a reader mode, the NFC device 15 can operate in a card mode. When the external device is an NFC tag, the NFC device 15 can operate in a reader mode as a reader of the NFC tag.

[0024] When the NFC device 15 operates in the card mode, the NFC device 15 can communicate with the external device 20 operating in the reader mode using a wireless signal in a specific frequency band (e.g., 13.56 MHz). When a radio frequency (RF) field caused by a signal emitted by the external device 20 is detected in the card mode, the NFC device 15 can continue an initial setting of RF parameters required for communication with the external device 20. For example, the RF parameters can include a frequency, a phase, etc. of a clock signal generated by the NFC device 15.

[0025] With respect to the conventional NFC technology, in the initial setting of the RF parameters by the NFC device 15, an arbitrary value can be used, or a value stored in a memory in a table or the like can be used. When the initial setting of the RF parameters is completed, the NFC device 15 can transmit a TX signal after receiving an RX signal from the external device 20 with the initially set RF parameters. When the initial setting of the RF parameters is performed in the above-described manner, it is not possible to cover all actual communication environments to which the NFC device 15 is exposed, and ultimately, since the external device 20 does not correctly recognize the TX signal transmitted by the NFC device 15 after the initial setting of the RF parameters, it can be impossible to establish communication.

[0026] According to aspects of the present application, when the NFC device 15 operating in the card mode senses an RF field generated by the external device 20, a pre-TX signal (e.g., a "first TX signal" or an "initial TX signal") for the initial setting of the RF parameters can be transmitted. For example, the pre-TX signal can be first transmitted before a first RX signal is received from the external device 20.

[0027] When the pre-TX signal is transmitted, a reflection signal thereof can enter the NFC device 15. The NFC device 15 can extract a recovered clock signal from the reflection signal, and can compare the recovered clock signal with a reference clock signal to determine a frequency, a phase, or the like for the initial setting of the RF parameters. Accordingly, the RF parameters can be initially set according to characteristics of an RF field generated by the external device 20 with which actual communication will be performed, and communication performance between the NFC device 15 and the external device 20 can be improved.

[0028] Figure 2 is a block diagram illustrating an NFC device according to an embodiment.

[0029] Reference Figure 2 The NFC device 100 according to an embodiment can include an antenna 110, a matching circuit 120, an amplifier 130, a clock generator 140, a phase detector 150, a clock extractor 160, and the like. In an embodiment, the NFC device 100 can be installed in the electronic device 10, and can receive power from a power supply device of the electronic device 10 to operate in a card mode and a reader mode.

[0030] The antenna 110 can be connected to the matching circuit 120, and can externally transmit a TX signal in response to a signal output by the amplifier 130. For example, the amplifier 130 can externally transmit a TX signal through the antenna 110 in response to a transmission clock signal CLK_TX output by the clock generator 140. The TX signal transmitted through the antenna 110 can include data to be transmitted to the external device 20. For example, data can be included in the TX signal by modulating the TX signal using an active load modulation (ALM) method, and can be externally released.

[0031] When the external device 20 generates an RF field and transmits a signal, an RX signal can be induced into the antenna 110 through the magnetic field. The clock extractor 160 can extract a recovery clock signal CLK_REC having a predetermined frequency and a predetermined phase from the RX signal introduced into the antenna 110. For example, characteristics such as a frequency and a phase of the recovery clock signal CLK_REC generated by the clock extractor 160 can be determined according to the RX signal entering the antenna 110.

[0032] The phase detector 150 can compare the recovery clock signal CLK_REC with a predetermined reference clock signal. For example, the reference clock signal can be generated by a phase-locked loop circuit or the like included in the NFC device 100, or included in the electronic device 10 together with the NFC device 100. The phase detector 150 can compare the phase of the recovery clock signal CLK_REC with the phase of the reference clock signal to calculate a phase difference PD, and can transmit the phase difference PD to the clock generator 140.

[0033] The clock generator 140 can adjust the phase of the transmission clock signal CLK_TX with reference to the phase difference PD received from the phase detector 150. For example, the clock generator 140 can advance or delay the phase of the transmission clock signal CLK_TX previously output to the amplifier 130 with reference to the phase difference PD. In this way, the phase of the transmission clock signal CLK_TX can be adjusted using the phase difference PD calculated by the phase detector 150 to improve the communication performance between the NFC device 100 and the external device 20.

[0034] In the operation of the NFC device 100, an RX signal can be received from the external device 20 through the antenna 110, a recovery clock signal CLK_REC can be extracted from the RX signal to generate a phase difference PD, and then the clock generator 140 can output a transmission clock signal CLK_TX to the amplifier 130. For example, after the NFC device 100 first receives an RX signal from the external device 20 in one communication period, the NFC device 100 can externally transmit a TX signal.

[0035] In an embodiment, the NFC device 100 can first transmit a TX signal before receiving an RX signal from the external device 20 under a condition that the NFC device 100 enters an RF field generated by the external device 20. The TX signal first transmitted before the NFC device 100 receives the RX signal can be defined as a pre-TX signal, and can be a signal transmitted for initial setting of RF parameters of the NFC device 100, not for communication with the external device.

[0036] For example, the RF parameters configured using the pre-TX signal can include a frequency, a phase, etc. of a transmission clock signal CLK_TX output by the clock generator 140. When the pre-TX signal is transmitted through the antenna 110, a reflected signal of the pre-TX signal can flow back into the antenna 110. The reflected signal of the pre-TX signal can be generated based in part on the RF field generated by the external device 20. The clock extractor 160 can generate a recovered clock signal CLK_REC from the reflected signal, the phase detector 150 can detect a phase difference PD between the recovered clock signal CLK_REC and the reference clock signal, and can transmit the detected phase difference PD to the clock generator 140. The phase difference PD transmitted to the clock generator 140 after the pre-TX signal is transmitted can be an initial phase difference for initial setting of the RF parameters.

[0037] The reflected signal of the pre-TX signal can vary depending on characteristics of the RF field generated by the external device 20. Unlike a method of selecting one of pre-stored values to initialize the RF parameters, the initial setting of the RF parameters can be performed by reflecting characteristics of the RF field for actual communication of the NFC device 100 to improve quality of a first TX signal transmitted by the NFC device 100 for communication with the external device 20. Accordingly, a communication probability between the NFC device 100 and the external device can increase, and a communication performance between the NFC device 100 and the external device can improve.

[0038] Figure 3 and Figure 4 is a flowchart illustrating an operation of an NFC device according to an embodiment.

[0039] First, referring to Figure 3 , an operation of an NFC device according to an embodiment can start with entering a field generated by an external device and sensed by the NFC device (S10). The external device can be a device operating in a reader mode, and can externally transmit an RF signal to generate the field.

[0040] When the NFC device detects the field, the NFC device can first transmit a pre-TX signal (S11). The pre-TX signal transmitted by the NFC device can be a signal that is first transmitted by the NFC device operating in a card mode before receiving a signal from an external device. For example, the NFC device can input a pre-clock signal to an amplifier connected to an antenna through a matching circuit, to transmit a pre-TX signal through the antenna.

[0041] The frequency and phase of the pre-clock signal input to the amplifier to transmit the pre-TX signal can be determined in various ways. In an embodiment, the NFC device can determine the frequency and phase of the pre-clock signal according to a predetermined setting.

[0042] Once the pre-TX signal is transmitted, the NFC device can adjust an RF parameter (S12). For example, when the NFC device adjusts the RF parameter, at least one of the frequency or the phase of a transmission clock signal input to the amplifier can be changed. When the RF parameter is adjusted, the NFC device can receive an RX signal from the external device through the field generated by the external device (S13). The NFC device can demodulate the RX signal to receive data transmitted by the external device.

[0043] The NFC device can transmit a TX signal to transmit a response to the RX signal to the external device (S14). The TX signal can include the response to the RX signal and data to be transmitted to the external device. A transmission clock signal can be input to the amplifier so that the NFC device can transmit the TX signal, and the frequency and / or phase of the transmission clock signal can be determined by the RF parameter adjusted previously in S12. Thereafter, field-out of the NFC device can be performed to terminate communication with the external device (S15). According to an embodiment, receiving the RX signal from the external device (S13) and transmitting the TX signal in response to the RX signal (S14) can be repeated a plurality of times.

[0044] Next, referring to Figure 4 , the operation of the NFC device according to an embodiment can begin with entering a field generated by an external device and sensed by the NFC device (S20). Similar to the embodiment previously described with reference to Figure 3 , the external device can be a device operating in a reader mode that generates a field by transmitting an RF signal.

[0045] When the field is detected, the NFC device can first output a pre-clock signal having a first phase to an amplifier (S21). The first phase of the pre-clock signal can be a randomly selected phase, and can be referred to herein as a "random phase." The amplifier can amplify the pre-clock signal, and can transmit it to an antenna, and thus, a pre-TX signal can be transmitted through the antenna (S22). When the pre-TX signal is transmitted through the antenna, a reflected signal of the pre-TX signal can return to the NFC device.

[0046] An analog signal can be generated at the antenna by a reflected signal that is returned to the NFC device. A clock extractor connected to the antenna in the NFC device can extract a reflected clock signal from the analog signal generated by the antenna in response to the reflected signal (S23). Once the reflected clock signal is extracted, a phase detector can compare a phase of the reflected clock signal with a phase of a reference clock signal (S24). For example, the reference clock signal can be a clock signal generated by the NFC device or by a separate circuit included in an electronic device equipped with the NFC device.

[0047] When a phase difference between the reflected clock signal and the reference clock signal is detected, the NFC device can adjust an RF parameter based on the phase difference (S25). For example, the phase difference between the reflected clock signal and the reference clock signal sensed by the phase detector in S24 can be an initial phase difference obtained by transmitting a pre-TX signal before the NFC device communicates with the external device. The NFC device can refer to the initial phase difference to adjust the RF parameter that determines a characteristic of a TX signal to be transmitted for communication with the external device.

[0048] When the RF parameter is adjusted, the NFC device can receive an RX signal from the external device through a field generated by the external device (S26). The NFC device can transmit a TX signal in response to the RX signal. In an embodiment, a clock generator included in the NFC device can output a transmission clock signal to an amplifier, and the amplifier can amplify the transmission clock signal and can input the transmission clock signal to the antenna to transmit the TX signal from the antenna.

[0049] In an embodiment, the NFC device can transmit the TX signal using the RF parameter adjusted in S25 (S27). For example, at least one of a frequency, a phase, or an amplitude of the transmission clock signal transmitted from the clock generator to the amplifier can be adjusted when the RF parameter is adjusted in S25. Accordingly, the RF parameter adjusted in S25 can be reflected in the TX signal transmitted by the amplifier through the antenna.

[0050] Thereafter, a field exit of the NFC device can be performed to terminate the communication with the external device (S28). According to an embodiment, receiving the RX signal from the external device (S26) and transmitting the TX signal in response to the RX signal (S27) can be repeated a plurality of times. In this case, during a time period after the TX signal is transmitted and before the RX signal is received again, the NFC device can readjust the RF parameter as needed.

[0051] As referred to above Figure 3 and Figure 4Described, in an embodiment, the NFC device operating in the card mode can first transmit a pre-TX signal before receiving a first RX signal from an external device operating in the reader mode and generating a field, and based on this, the RF parameters can be adjusted. Accordingly, the RF parameters can be adjusted considering the actual communication environment including the strength of the field generated by the external device, and the first TX signal can be transmitted based on this to improve the reliability of the communication between the NFC device and the external device and increase the communication between the NFC device and the external device.

[0052] Figure 5 and Figure 6 are views illustrating the operation of the NFC device according to an embodiment.

[0053] First, referring to Figure 5 , the NFC device can enter a space affected by a field generated by an external device, can sense the field, and can apply stored RF parameters. Information for the initial setting of the RF parameters can be stored in a memory inside or outside the NFC device, and when the field generated by the external device is detected, the NFC device can complete the initial setting of the RF parameters based on the information read from the memory.

[0054] Thereafter, the NFC device can receive a first RX signal RX1 from the external device during a first reception time TRX1. After receiving the first RX signal RX1, the NFC device can transmit a first TX signal TX1 based on the RF parameters set based on the information read from the memory before the first reception time TRX1. The first TX signal TX1 can be transmitted during a first transmission time TTX1 after the first reception time TRX1.

[0055] The first TX signal TX1 transmitted with the RF parameters set based on the information obtained from the memory can not be suitable for transmitting data to the external device through the field generated by the external device, and thus, after the first transmission time TTX1, the NFC device can further adjust the RF parameters. Thereafter, in a second reception time TRX2, the NFC device can receive a second RX signal RX2 from the external device, and can transmit a second TX signal TX2 during a second transmission time TTX2 in response to the second RX signal RX2. When the second transmission time TTX2 ends, the operation of adjusting the RF parameters can be performed again.

[0056] In this way, when the NFC device performs initial setting of the RF parameters based on the pre-stored information and first receives the first RX signal RX1 from the external device, compatibility of the first TX signal TX1 transmitted first by the NFC device with the external device can not be sufficiently ensured. For example, since the phase of the first TX signal TX1 does not match the phase of the external device, a phase error can occur, which can degrade reliability of communication between the NFC device and the external device.

[0057] The RF parameters affecting compatibility of the TX signals TX1 and TX2 transmitted from the NFC device with the external device can also change depending not only on the strength of the field formed by the external device, but also on characteristics of the antenna, matching circuit, etc. included in a transmission path of the TX signals TX1 and TX2 from the NFC device. Since compatibility of the TX signals TX1 and TX2 with the external device varies depending on the design and manufacturing process of the NFC device and the field generated by the external device in an actual use environment, there is a limitation in optimizing the initial setting of the RF parameters using only the information previously stored in the memory.

[0058] As shown in the embodiment of FIG. 1, Figure 6 Instead of using the information stored in the memory, the NFC device can transmit a pre-TX signal before receiving the first RX signal RX1 from the external device, and can use a reflection signal thereof to perform initial setting of the RF parameters. Accordingly, quality of the first TX signal TX1 transmitted to the external device as a response to the first RX signal RX1 can be improved to allow smooth communication between the NFC device and the external device.

[0059] Referring to Figure 6 Operation of the NFC device according to the embodiment can start with entering a space affected by a field generated by the external device and sensing the field by the NFC device. Upon detecting the field, the NFC device can transmit a pre-TX signal PRE-TX during a pre-transmission time TPRE, instead of initializing the RF parameters using the information stored in the memory. For example, a pre-clock signal generated inside the NFC device can be input to an amplifier, and the amplifier can amplify and output the pre-clock signal to an antenna. Accordingly, the pre-TX signal can be transmitted through the antenna. The pre-transmission time TPRE can be shorter than a first transmission time TTX1 at which the first TX signal TX1 is transmitted.

[0060] When the pre-TX signal is transmitted, a reflected signal of the pre-TX signal can flow back into the antenna. Accordingly, an analog signal corresponding to the reflected signal can be output from the antenna, and the NFC device can extract a reflected clock signal corresponding to the reflected signal from the analog signal. The reflected clock signal can have a predetermined frequency and a predetermined phase, and the NFC device can compare the phase of the reflected clock signal with the phase of the reference clock signal to detect an initial phase difference.

[0061] The NFC device can adjust the RF parameter based on the initial phase difference. In Figure 6 In the illustrated embodiment, the phase of a first TX signal TX1 that can be initially transmitted to the external device can be determined by the initial phase difference. Accordingly, the RF parameter can be adjusted using the reflected clock signal in which characteristics of a field generated by the external device to communicate with the NFC device and characteristics of the antenna, the matching circuit, etc. mounted on the NFC device are reflected, and the quality of the first TX signal TX1 can be improved.

[0062] For example, the phase of the reflected clock signal can be affected by the field generated by the external device. The phase of the transmission clock signal input to the amplifier during the first transmission time TTX1 based on the initial phase difference calculated by comparing the phase of the reflected clock signal with the phase of the reference clock signal can be adjusted to sufficiently ensure compatibility between the first TX signal TX1 and the external device and to improve reliability and accuracy of communication therebetween.

[0063] As Figure 6 As illustrated in the embodiment, the NFC device can operate by first transmitting a pre-TX signal before receiving an RX signal from the external device. For example, the pre-TX signal PRE-TX can be transmitted through the antenna before receiving the first RX signal RX1, and the first TX signal TX1 can be transmitted through the antenna before receiving the second RX signal RX2. In addition, the NFC device can adjust the RF parameter that determines the frequency, phase, etc. of the transmission clock signal used to transmit the first TX signal TX1 during a time after the pre-TX signal PRE-TX is transmitted through the antenna and before the first RX signal RX1 is received from the external device.

[0064] Figure 7 FIG. 1 is a view illustrating an NFC device according to an embodiment.

[0065] Referring to Figure 7According to embodiments, the NFC device 200 can include an antenna 210, a matching circuit 220, an amplifier (AMP) 230, a clock generator 240, a phase detector 250, a clock extractor 260, etc. The amplifier 230 can amplify a transmission clock signal CLK_TX received from the clock generator 240, and can output the same to the matching circuit 220. The matching circuit 220 can perform impedance matching on the signal output by the amplifier 230, can transmit the same to the antenna 210, and can transmit a TX signal from the antenna 210 to the outside.

[0066] The matching circuit 220 can include at least one inductor element and at least one capacitor element. Depending on embodiments, the matching circuit 220 can also be connected between the antenna 210 and the clock extractor 260.

[0067] The antenna 210 can generate an analog signal in response to an RF signal flowing in from the outside. The analog signal can be transmitted to the clock extractor 260, and the clock extractor 260 can extract a recovery clock signal CLK_REC from the analog signal. In embodiments, the analog signal can be a signal having a sinusoidal waveform, and the clock extractor 260 can generate the recovery clock signal CLK_REC, which can be a square wave signal, from the analog signal.

[0068] The recovery clock signal CLK_REC can be input to the phase detector 250. The phase detector 250 can compare the phase of the recovery clock signal CLK_REC with the phase of a reference clock signal CLK_REF. For example, the reference clock signal CLK_REF can be a clock signal generated by a phase-locked loop circuit included in the NFC device 200 or an electronic device equipped with the NFC device 200.

[0069] The phase detector 250 can count the difference between the phase of the recovery clock signal CLK_REC and the phase of the reference clock signal CLK_REF using a count clock signal CLK_CNT. The frequency of the count clock signal CLK_CNT can be faster than the frequency of the recovery clock signal CLK_REC and the frequency of the reference clock signal CLK_REF. In embodiments, the frequency of the recovery clock signal CLK_REC and the frequency of the reference clock signal CLK_REF can be about 13.56 MHz, respectively, and the frequency of the count clock signal CLK_CNT can be several hundred MHz. In embodiments, the phase detector 250 can count the time between the rising edge of the recovery clock signal CLK_REC and the rising edge of the reference clock signal CLK_REF as the count clock signal CLK_CNT to calculate a phase difference PD, and can transmit the phase difference PD to the clock generator 240.

[0070] The clock generator 240 can adjust the phase of the transmission clock signal CLK_TX with reference to the phase difference PD. In an embodiment, the transmission clock signal CLK_TX can be generated by controlling the phase of the recovery clock signal CLK_REC or the phase of the reference clock signal CLK_REF with reference to the phase difference PD. The transmission clock signal CLK_TX can be input to the amplifier 230, and as described above, the amplifier 230 can amplify the transmission clock signal CLK_TX and can apply it to the matching circuit 220 and the antenna 210.

[0071] In an embodiment, before receiving the first RX signal from the external device, the NFC device 200 can first transmit a pre-TX signal through the antenna 210. When the pre-TX signal is transmitted, some of it can return as a reflection signal and flow back into the NFC device 200 through the antenna 210. The antenna 210 can transmit an analog signal corresponding to the reflection signal to the clock extractor 260, and the clock extractor 260 can extract a reflection clock signal from the reflection signal and can transmit it to the phase detector 250 as the recovery clock signal CLK_REC.

[0072] The phase detector 250 can compare the phase of the reflection clock signal received as the recovery clock signal CLK_REC with the phase of the reference clock signal CLK_REF. As described above, the phase detector 250 can count the delay time between the reflection clock signal and the reference clock signal CLK_REF using the count clock signal CLK_CNT having a relatively short period to calculate the phase difference PD and can transmit it to the clock generator 240.

[0073] The clock generator 240 can adjust the phase of the transmission clock signal CLK_TX with reference to the phase difference PD calculated by the phase detector 250. Accordingly, before receiving the first RX signal from the external device, an operation of optimizing the TX signal transmitted by the NFC device 200 to adapt to the communication environment can be first completed, and the quality of the first TX signal can be improved to improve the accuracy and reliability of the communication between the NFC device 200 and the external device.

[0074] The phase detector 250 can calculate the phase difference PD in various ways. As explained previously, the count clock signal CLK_CNT having a fast frequency can be used to calculate the phase difference PD corresponding to the delay time between the rising edge of the recovery clock signal CLK_REC and the rising edge of the reference clock signal CLK_REF. In addition, a time-to-digital converter for calculating the delay time between the recovery clock signal CLK_REC and the reference clock signal CLK_REF, which can be difficult to determine from the count clock signal CLK_CNT, can be included in the phase detector 250.

[0075] Figure 8 is a view illustrating an operation of an NFC device according to an embodiment.

[0076] Figure 8 may be a view illustrating a recovery clock signal CLK_REC and a reference clock signal CLK_REF input to a phase detector of an NFC device according to an embodiment. In an embodiment, although the reference clock signal CLK_REF generated by a phase-locked loop circuit has a constant period, each period of the recovery clock signal CLK_REC can not be fixed and can increase or decrease. Thus, a phase difference can occur between the reference clock signal CLK_REF and the recovery clock signal CLK_REC.

[0077] In Figure 8 the illustrated embodiment, the period of the recovery clock signal CLK_REC can be longer than the period of the reference clock signal CLK_REF. Thus, as Figure 8 indicated, clock delay times (ΔT1 to ΔT5) can occur between rising edges of the reference clock signal CLK_REF and the recovery clock signal CLK_REC.

[0078] As previously described with reference to Figure 7 , the NFC device can include a phase detector that compares the recovery clock signal CLK_REC and the reference clock signal CLK_REF to calculate a phase difference. In an embodiment, the phase detector can receive the recovery clock signal CLK_REC and the reference clock signal CLK_REF and can count clock delay times (ΔT1 to ΔT5) between rising edges of the recovery clock signal CLK_REC and the reference clock signal CLK_REF as a separate count clock signal. Hereinafter, with reference to Figure 9 and Figure 10 , a method for calculating a phase difference based on a third clock delay time ΔT3 in the highlighted section 300 will be described in more detail. Figure 8

[0079] Figure 9 and Figure 10 is a view illustrating an operation of an NFC device according to an embodiment.

[0080] With reference to Figure 9 ​, the NFC device 400 according to the embodiment can include a phase detector 410, a clock generator 420, etc. The phase detector 410 can receive the recovered clock signal CLK_REC, the reference clock signal CLK_REF, and the counting clock signal CLK_CNT, and can transmit a phase difference PD to the clock generator 420. The clock generator 420 can control a phase of the transmission clock signal CLK_TX based on the phase difference PD, and then can output the same to the amplifier.

[0081] Figure 10 may be an enlarged view of the section 300 in the embodiment, as previously described with reference to Figure 8 . Referring to Figure 8 and Figure 10 , a rising edge of the recovered clock signal CLK_REC can be later than a rising edge of the reference clock signal CLK_REF by a third clock delay time ΔT3. A period TP of the counting clock signal CLK_CNT can be shorter than periods of the recovered clock signal CLK_REC and the reference clock signal CLK_REF, respectively. In the embodiment, the periods of the recovered clock signal CLK_REC and the reference clock signal CLK_REF can be several tens of ns, and the period TP of the counting clock signal CLK_CNT can be several ns.

[0082] In the embodiment illustrated in Figure 10 , the first to fourth periods P1 to P4 of the counting clock signal CLK_CNT can be included during the third clock delay time ΔT3. Accordingly, the phase detector 410 can output the phase difference PD corresponding to the count number 4 calculated based on the counting clock signal CLK_CNT to the clock generator 420.

[0083] The clock generator 420 can adjust a phase of a pre-clock signal output to the amplifier to emit the pre TX signal with reference to the phase difference PD corresponding to the third clock delay time ΔT3 including the first to fourth periods P1 to P4. For example, the clock generator 420 can reflect the phase difference PD inversely into the pre-clock signal to generate the transmission clock signal of the TX signal for transmission to the external device. In the embodiment illustrated in Figure 10 , the clock generator 420 can advance the phase of the pre-clock signal by the third clock delay time ΔT3 indicated by the phase difference PD to generate the transmission clock signal.

[0084] According to the embodiment, clock delay times (ΔT1 to ΔT5) between the recovered clock signal CLK_REC and the reference clock signal CLK_REF can not be accurately counted as multiples of one period TP of the counting clock signal CLK_CNT. In this case, as reference is made to Figure 9 and Figure 10As described above, it can be difficult to accurately calculate the phase difference PD between the recovery clock signal CLK_REC and the reference clock signal CLK_REF by using only the count clock signal CLK_CNT.

[0085] In an embodiment, the phase detector 410 of the NFC device 400 can detect a phase difference PD shorter than a period TP of the count clock signal CLK_CNT due to a delay time. Hereinafter, referring to FIG. 5, Figures 11 to 13 will be described in more detail.

[0086] Figures 11 to 13 is a view illustrating an operation of an NFC device according to an embodiment.

[0087] Referring to Figure 11 , the NFC device 500 according to an embodiment can include a phase detector 510, a clock generator 520, etc. The phase detector 510 can include a first phase detector 511 and a second phase detector 512, and the recovery clock signal CLK_REC and the count clock signal CLK_CNT can be input to the first phase detector 511 and the second phase detector 512, respectively.

[0088] In addition to the recovery clock signal CLK_REC and the count clock signal CLK_CNT, a reference clock signal CLK_REF can be further input to the first phase detector 511. As described above, the reference clock signal CLK_REF can have a fixed period, and a period of the recovery clock signal CLK_REC can vary depending on a communication environment, etc. The count clock signal CLK_CNT can have a period shorter than the period of the recovery clock signal CLK_REC and the period of the reference clock signal CLK_REF.

[0089] As previously described with reference to Figure 9 and Figure 10 , the first phase detector 511 can provide the clock generator 520 with a first phase difference PD1 corresponding to a result of counting a clock delay time between the recovery clock signal CLK_REC and the reference clock signal CLK_REF with the count clock signal CLK_CNT. For example, the first phase difference PD1 can correspond to an integer part of a phase difference between the recovery clock signal CLK_REC and the reference clock signal CLK_REF.

[0090] The second phase detector 512 can not receive the reference clock signal CLK_REF. The second phase detector 512 can include a time-to-digital converter TDC and can provide the clock generator 520 with a second phase difference PD2 corresponding to a clock delay time between the recovered clock signal CLK_REC and the counting clock signal CLK_CNT. The second phase difference PD2 can be generated as a multiple of a unit delay time, shorter than a period of the counting clock signal CLK_CNT, and thus the second phase difference PD2 can correspond to a fractional part of a phase difference between the recovered clock signal CLK_REC and the reference clock signal CLK_REF.

[0091] Referring to FIGS. 11 and 12 together Figure 11 and Figure 12 , the rising edge of the recovered clock signal CLK_REC can be later than the rising edge of the reference clock signal CLK_REF. The period TP of the counting clock signal CLK_CNT can be shorter than the period of the recovered clock signal CLK_REC and the period of the reference clock signal CLK_REF, respectively. In Figure 12 the embodiment shown in FIG. 12, the first period P1 to the fourth period P4 of the counting clock signal CLK_CNT can be included during the time between the rising edge of the recovered clock signal CLK_REC and the rising edge of the reference clock signal CLK_REF. The first phase detector 511 can calculate the first delay time TD1 based on the counting clock signal CLK_CNT, and the clock generator 520 can provide the first phase difference PD1 corresponding to the first delay time TD1.

[0092] In Figure 12 the embodiment shown in FIG. 12, the delay time between the rising edge of the recovered clock signal CLK_REC and the rising edge of the reference clock signal CLK_REF can not match a multiple of one period TP of the counting clock signal CLK_CNT. Referring to Figure 12 , in the section 600 including the rising edge of the recovered clock signal CLK_REC, the end point of the fourth period P4 can not coincide with the rising edge of the recovered clock signal CLK_REC. Thus, only the first phase difference PD1 can not accurately represent the phase difference between the recovered clock signal CLK_REC and the reference clock signal CLK_REF.

[0093] In Figure 11 the embodiment shown in FIG. 12, the second phase detector 512 can calculate a second delay time TD2 excluding the first delay time TD1 from the delay time between the rising edge of the recovered clock signal CLK_REC and the rising edge of the reference clock signal CLK_REF. The second phase detector 512 can include a time-to-digital converter. Referring to Figure 13The second delay time TD2 can be counted as a unit delay time shorter than one period TP of the count clock signal CLK_CNT, and a second phase difference PD2 corresponding to the second delay time TD2 can be provided to the clock generator 520.

[0094] The clock generator 520 can inversely reflect the first phase difference PD1 and the second phase difference PD2 to the transmission clock signal CLK_TX to adjust a phase of the transmission clock signal CLK_TX. For example, the transmission clock signal CLK_TX can be advanced by a clock delay time which can be a sum of a first delay time TD1 defined by the first phase difference PD1 and a second delay time TD2 defined by the second phase difference PD2.

[0095] The phase of the transmission clock signal CLK_TX can be adjusted with reference to the first phase difference PD1 calculated in units of a period TP of the count clock signal CLK_CNT and the second phase difference PD2 calculated by a unit delay time shorter than the period TP of the count clock signal CLK_CNT to generate the transmission clock signal CLK_TX optimized for a communication environment of the NFC device 500. In this way, the first phase difference PD1 can be calculated using the count clock signal CLK_CNT with a relatively low resolution, and the second phase difference PD2 can be calculated using a time-to-digital converter with a high resolution to increase accuracy of phase difference detection and effectively manage power consumption of the NFC device 500.

[0096] Figure 14 is a view illustrating a time-to-digital converter included in an NFC device according to an embodiment.

[0097] As previously described, the phase detector can include a time-to-digital converter capable of detecting a second phase difference PD2 having a resolution higher than a period of a count clock signal. With reference to Figure 14 The time-to-digital converter 700 included in the phase detector can include a plurality of delay cells (DCs) 710, a plurality of flip-flops 720, a TDC encoder 730, etc.

[0098] The plurality of delay cells 710 can be connected in series and can receive the count clock signal CLK_CNT. Each of the plurality of delay cells 710 can have a predetermined unit delay time. For example, the unit delay time of each of the plurality of delay cells 710 can be tens of ps.

[0099] An input terminal of each of the plurality of flip-flops 720 can be connected to an input terminal of each of the plurality of delay units 710, and an output terminal of each of the plurality of flip-flops 720 can be connected to the TDC encoder 730. The plurality of flip-flops 720 can operate in synchronization with the reference clock signal CLK_REF. The TDC encoder 730 can output a second phase difference PD2 obtained by encoding outputs of the plurality of flip-flops 720 into a digital signal. A number of bits of the second phase difference PD2 can be determined depending on a number of the plurality of flip-flops 720.

[0100] A number of the plurality of delay units 710 and a number of the plurality of flip-flops 720 can be determined according to a unit delay time of each of the plurality of delay units 710 and one period of the count clock signal CLK_CNT. For example, the number of the plurality of delay units 710 can be equal to the number of the plurality of flip-flops 720, and the number of the plurality of delay units 710 can be a value obtained by dividing one period of the count clock signal CLK_CNT by the unit delay time of each of the plurality of delay units 710.

[0101] For convenience of explanation, reference is made to Figure 13 The count clock signal CLK_CNT can be delayed by the unit delay time by the plurality of delay units 710 to be input to the plurality of flip-flops 720. In the example shown in Figure 13 , among the plurality of flip-flops 720, 12 flip-flops can output '1', and the remaining flip-flops can output '0'.

[0102] In the embodiments described with reference to Figures 9 to 14 , the NFC device (400 and 500) can transmit a pre-TX signal before receiving a first RX signal from an external device, and can use a reflected signal of the pre-TX signal to apply an initial setting to an RF parameter. For example, in the NFC device 500 of the embodiment shown in Figure 11 , the clock generator 520 can output a transmission clock signal CLK_TX for transmitting the pre-TX signal to the amplifier before receiving the first RX signal from the external device. A frequency and / or a phase of the transmission clock signal CLK_TX for transmitting the pre-TX signal can be arbitrarily determined.

[0103] When the pre-TX signal is transmitted to the outside, a reflected signal thereof can flow back into the NFC device 500. A clock extractor of the NFC device 500 can generate a recovered clock signal CLK_REC from the reflected signal, and can provide the same to the phase detector 510. The first phase detector 511 can count a phase difference between the recovered clock signal CLK_REC and the reference clock signal CLK_REF as a count clock signal CLK_CNT to calculate a first phase difference PD1. The second phase detector 512 can include a time-to-digital converter 700 which calculates a second phase difference PD2 corresponding to a phase difference between the recovered clock signal CLK_REC and the count clock signal CLK_CNT.

[0104] A resolution of the first phase difference PD1 can be determined according to a period TP of the count clock signal CLK_CNT, and a resolution of the second phase difference PD2 can be determined according to a unit delay time of each of a plurality of delay units 710 included in the time-to-digital converter 700. With reference to the first phase difference PD1 detected at a relatively low resolution and the second phase difference PD2 detected at a relatively high resolution, the clock generator 520 can adjust a frequency and / or a phase of the transmission clock signal CLK_TX.

[0105] Before the NFC device 500 receives the first RX signal from the external device, the NFC device 500 can adjust RF parameters for generating the transmission clock signal CLK_TX with reference to the first phase difference PD1 and the second phase difference PD2. Accordingly, after the NFC device 500 receives the first RX signal, a quality of the first TX signal transmitted to the external device in response to the first RX signal can be improved, and an accuracy and a reliability of communication between the NFC device 500 and the external device can be improved.

[0106] Figure 15 is a block diagram illustrating an electronic device including an NFC device according to an embodiment.

[0107] Referring to Figure 15 , the electronic device 800 can include an application processor (AP) 810, an NFC device 820, a memory device 830, a user interface 840, a power supply unit 850, etc. For example, the electronic device 800 can be a mobile phone, a smart phone, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital camera, a music player, a portable game machine, a navigation system, a laptop computer, etc.

[0108] The application processor 810 can control overall operations of the electronic device 800. The application processor 810 can execute applications that provide Internet browsing, games, video playback, image capture, etc. The application processor 810 can include one processor core (single core), or can include a plurality of processor cores (multi core). The application processor 810 can include a cache memory device that temporarily stores instructions or data stored in the memory device 830.

[0109] The memory device 830 can store data required for operations of the electronic device 800. As an example, the memory device 830 can include a volatile memory device and / or a non-volatile memory device. The volatile memory device can be implemented as a DRAM, a SRAM, a mobile DRAM, or a memory similar thereto, and the non-volatile memory device can be implemented as an electrically erasable programmable read-only memory (EEPROM), a flash memory, a phase change RAM (PRAM), a resistive RAM (RRAM), a nano floating gate memory (NFGM), a polymer RAM (PoRAM), a magnetic RAM (MRAM), a ferroelectric RAM (FRAM), or a memory similar thereto. For example, the memory device 830 can store a boot image for booting the electronic device 800, and can store output data to be transmitted to an external device and input data received from the external device.

[0110] The NFC device 820 can transmit data provided by the application processor 810 and / or the memory device 830 to an external device through NFC communication, and can receive data received from the external device to provide the same to the application processor 810 and / or the memory device 830. For example, the NFC device 820 can be implemented according to the embodiments of the inventive concept described in the detailed description. Figures 1 to 14 To improve communication quality with the external device, the NFC device 820 can emit a pre-TX signal before receiving a first RX signal from the external device, and can compare a reflection clock signal recovered from a reflection signal with a reference clock signal to adjust an RF parameter for setting a first TX signal.

[0111] The user interface 840 can include one or more input devices such as a keypad or a touch screen, and / or one or more output devices such as a speaker or a display device. The power supply unit 850 can supply an operating voltage of the electronic device 800. In addition, the electronic device 800 can further include a camera image processor (CIP), a modem such as a baseband chipset, etc. For example, the modem can be a modem processor that supports communication such as GSM, GPRS, WCDMA, HSxPA, etc.

[0112] According to an embodiment, after sensing a field generated by an external device, and before first receiving an RX signal from the external device, a pre-TX signal can be first transmitted from the NFC device. The NFC device can receive a reflected signal of the pre-TX signal to generate a recovered clock signal, and can compare a phase of a pre-clock signal input to an amplifier that transmits the pre-TX signal with a phase of the recovered clock signal to perform initial setting of RF parameters. Accordingly, the RF parameters can be accurately set, and communication performance between the NFC device and the external device can be improved.

[0113] The various advantages and effects of the present inventive concept are not limited to the above-described content, and can be more easily understood through a description of specific embodiments of the present inventive concept.

[0114] While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and changes can be made thereto without departing from the scope of the present inventive concept defined by the appended claims.

Claims

1. A near field communication (NFC) device, comprising: an amplifier configured to output a transmit TX signal to an antenna; a phase detector configured to compare a phase of a recovered clock signal generated by a received RX signal transmitted to the antenna with a phase of a reference clock signal to calculate a phase difference; as well as a clock generator configured to output a transmission clock signal to the amplifier and control a phase of the transmission clock signal with reference to the phase difference calculated by the phase detector, wherein, when a field transmitted by an external reader is detected, the clock generator outputs a pre-clock signal having a random phase to the amplifier to transmit a pre-TX signal from the amplifier before receiving the RX signal from the external reader, The phase detector transmits an initial phase difference calculated by comparing a phase of a reflected clock signal recovered from a reflected signal of the pre-TX signal received at the antenna with the phase of the reference clock signal to the clock generator.

2. The NFC device of claim 1, wherein, When the phase detector detects the initial phase difference and receives the RX signal from the external reader, the clock generator controls the phase of the transmission clock signal based on the initial phase difference.

3. The NFC device according to claim 1 , further comprising: A matching circuit is connected between the output terminal of the amplifier and the antenna.

4. The NFC device of claim 1, wherein, When active load modulation operation is activated, the phase detector compares the phase of the reflected clock signal with the phase of the reference clock signal to detect the initial phase difference.

5. The NFC device of claim 1, wherein, The phase detector calculates the initial phase difference using a count clock signal having a period shorter than a period of the reference clock signal.

6. The NFC device of claim 5, wherein, The phase detector includes a first phase detector that calculates a first component of the initial phase difference as a multiple of the period of the counting clock signal, and a second phase detector that calculates a second component of the initial phase difference as a multiple of a unit delay time shorter than the period of the counting clock signal.

7. The NFC device of claim 6, wherein, The second phase detector is a time-to-digital converter including a plurality of delay cells, each of the plurality of delay cells having a delay time equal to the unit delay time.

8. The NFC device of claim 6, wherein, The first component is determined by the number of times the cycle of the counting clock signal is repeated during a clock delay time between a rising edge of the recovered clock signal and a rising edge of the reference clock signal.

9. The NFC device of claim 8, wherein, The second component is determined by the number of times the unit delay time is repeated after the last cycle of the count clock signal included in the clock delay time and before the rising edge of the recovery clock signal arrives.

10. The NFC device of claim 6, wherein, The first component is an integer part of the initial phase difference, and the second component is a fractional part of the initial phase difference.

11. A near field communication (NFC) device, comprising: a clock generator configured to generate a pre-clock signal having a random phase when an entry into a field generated by an external device is detected; an amplifier configured to transmit a pre-transmission (TX) signal through an antenna in response to the pre-clock signal; and a phase detector configured to compare a reflection clock signal generated by a reflection signal of the pre-TX signal received by the antenna with a predetermined reference clock signal to calculate an initial phase difference when the reflection signal is received by the antenna, wherein the clock generator adjusts a radio frequency (RF) parameter including at least one of a frequency or a phase of a first TX signal first transmitted to the external device with reference to the initial phase difference.

12. The NFC device according to claim 11, wherein: the initial phase difference includes a first phase difference and a second phase difference, the phase detector detects the first phase difference at a first resolution and detects the second phase difference at a second resolution higher than the first resolution.

13. The NFC device of claim 11, wherein, the phase detector compares a recovered clock signal generated by a signal received by the antenna after the first TX signal is transmitted with the predetermined reference clock signal to adjust the RF parameter to be applied to a second TX signal transmitted to the external device after the first TX signal is transmitted.

14. The NFC device of claim 11, wherein, the phase detector receives the reflection clock signal, the predetermined reference clock signal, and a counting clock signal having a period shorter than a period of the reflection clock signal and a period of the predetermined reference clock signal.

15. The NFC device of claim 14, wherein, a transmission time of the pre-TX signal is shorter than a transmission time of the first TX signal. 16.The NFC device of claim 11, further comprising: a matching circuit connected between the amplifier and the antenna and including at least one capacitor element and at least one inductor element.

17. The NFC device of claim 11, wherein, the clock generator generates a transmission clock signal for the first TX signal by inversely reflecting a clock delay time defined by the initial phase difference to the pre-clock signal. 18.A near field communication (NFC) device, comprising: an antenna configured to transmit a transmission (TX) signal to an external device and receive a reception (RX) signal from the external device; an amplifier configured to output the TX signal to the antenna; and a clock generator configured to output a transmission clock signal corresponding to the TX signal to the amplifier before the RX signal is received from the external device, wherein the clock generator adjusts a radio frequency (RF) parameter including at least one of a frequency or a phase of the transmission clock signal after the TX signal is transmitted to the antenna and before the RX signal is received from the external device.

19. The NFC device of claim 18, wherein, the RX signal is a first RX signal first received from the external device.

20. The NFC device of claim 19, wherein, a phase of the transmission clock signal output from the clock generator to the amplifier before the first RX signal is received from the external device is randomly determined.

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