Patent Description:
From <CIT> there is known a communication apparatus capable of performing a non-contact communication with the information processing terminal, on which the IC chip is mounted, by transmitting carrier signals and performing a load modulation by the IC chip received with the carrier signals comprises: a reference clock generation part for generating the reference clock signals of a fixed cycle; a communication antenna for transmitting the carrier signals of a prescribed frequency corresponding to the reference clock signals, resonating response signals corresponding to the load modulation by a prescribed tuning frequency and receiving them; and a tuning frequency control part for adjusting the prescribed tuning frequency of the communication antenna on the basis of the phase change to the reference clock signals of the carrier signals in the communication antenna.

Embodiments of the inventive concepts relate to a wireless communication device, and more particularly, to a near field communication device.

Radio frequency identification (RFID) refers to a form of communication that allows a reader situated at a short range from a card to supply power to the card and communicate with the card. Near field communication (NFC) is being used as an example of RFID. NFC provides high flexibility in that one communication device can perform both a function of the reader and a function of the card.

A center frequency defined in the NFC standard and a resonant frequency of an antenna of an NFC device may be different from each other due to an error of the process of manufacturing tolerance or errors, or because the center frequency and the resonant frequency were intentionally designed to be different. If the center frequency and the resonant frequency differ from each other, communication quality of the NFC device may be degraded. This degradation may reduce the effective distance at which the NFC device can communicate.

Embodiments of the inventive concepts provide near field communication devices with improved communication quality. The object is attained by a near field communication device according to claim <NUM>. Further developments of the invention are specified in the dependent claims.

Below, embodiments of the inventive concepts will be described in detail with reference to accompanying drawings to such an extent that one of ordinary skill in the art may implement embodiments of the inventive concepts. Like reference numerals refer to like parts throughout the figures and specification unless otherwise specified.

<FIG> is a schematic block diagram of an example of a near field communication (NFC) system <NUM>. Referring to <FIG>, the NFC system <NUM> includes first and second NFC devices <NUM> and <NUM>. The first NFC device <NUM> is connected to a first antenna <NUM>, and the second NFC device <NUM> is connected to a second antenna <NUM>.

Each of the first and second NFC devices <NUM> and <NUM> may operate in a reader mode or a card mode. For example, the first NFC device <NUM> may operate in the reader mode, and the second NFC device <NUM> may operate in the card mode. The first NFC device <NUM> (operating in the reader mode) may transmit a first signal to the second NFC device <NUM> through electromagnetic induction between the first antenna <NUM> and the second antenna <NUM>. The first signal may include a continuous wave for transmitting power and a first information signal that is added to the continuous wave. The first information signal may include, for example, information that is to be transmitted from the first NFC device <NUM> to the second NFC device <NUM>.

The second NFC device <NUM> may obtain power from the continuous wave of the first signal. The second NFC device <NUM> may also obtain information from the first information signal of the first signal. The second NFC device <NUM> may add a second information signal to the continuous wave of the first signal and may transmit the second information signal to the first NFC device <NUM> as part of a second signal. For example, the second NFC device <NUM> may transmit the second signal to the first NFC device <NUM> through electromagnetic induction between the first antenna <NUM> and the second antenna <NUM>.

In an embodiment, a center frequency of the near field communication (in the above example, the center frequency of the first and second signals) may be determined by the near field communication standard and may be, for example, <NUM>. A resonant frequency of the first antenna <NUM> of the first NFC device <NUM> may be determined based on, for example, an intended purpose or use for the first NFC device <NUM> and a process used to manufacture the first NFC device <NUM>. Likewise, a resonant frequency of the second antenna <NUM> of the second NFC device <NUM> may be determined based on, for example, an intended purpose or use for the second NFC device <NUM> and a process used to manufacture the second NFC device <NUM>.

Resonant frequencies of the first and second antennas <NUM> and <NUM> of the first and second NFC devices <NUM> and <NUM> may be different from a center frequency of the near field communication due to, for example, the intended purpose(s) of the first and second antennas <NUM> and <NUM> or the manufacturing process or processes used to fabricate the first and second antennas <NUM> and <NUM>. If the center frequency of the signals transmitted by the first and second NFC devices <NUM> and <NUM> differ from the resonant frequency of one or both of the first and second antennas <NUM> and <NUM>, then the communication quality of the NFC system <NUM> may be degraded.

<FIG> is a graph illustrating how a difference between a center frequency of the signals transmitted by an NFC device and a resonant frequency of the antenna of the NFC device may influence the communication quality of the NFC system <NUM>. In <FIG>, the abscissa represents a resonant frequency Fres, and the ordinate represents a communication distance D in which near field communication is possible. The communication distance D in which near field communication is possible may be for example, the maximum communication distance or an average communication distance. A first line L1 shows a variation of the communication distance D as a function of the resonant frequency Fres in the NFC system <NUM>.

Referring to <FIG>, the communication distance D has the maximum value when the resonant frequency Fres coincides with the center frequency FC of the transmitted signal. The communication distance D decreases as the resonant frequency Fres is increased above the center frequency FC, and the communication distance D also decreases as the resonant frequency Fres is decreased below the center frequency FC. That is, the communication distance D decreases as the resonant frequency Fres moves away from the center frequency FC.

A phase of a signal that is transmitted between the first and second NFC devices <NUM> and <NUM> may be delayed or advanced because of, for example, a path delay associated with the antennas <NUM> and/or <NUM>. The communication distance D may be increased by adjusting a phase of the transmission signal when the resonant frequency Fres differs from the center frequency FC.

<FIG> is a graph illustrating how the communication distance D of the NFC system of <FIG> may be extended by adjusting the phase of the transmitted signals. Line L1 in <FIG> is identical to line L1 in <FIG>. A second line L2 is further illustrated in <FIG> that shows the communication distance D when a phase of a signal transmitted by one of the NFC devices (such a signal is referred to herein as a "transmission signal") is adjusted to, for example, compensate for a difference between the resonant frequency Fres and the center frequency FC of the transmitted signal.

In an embodiment, a transmission signal may be sent at a default phase θd when the resonant frequency Fres coincides with the center frequency FC. For example, the default phase θd may be <NUM> degree or <NUM> degrees.

A phase of the transmission signal may be adjusted according to a first phase adjustment PA1 when the resonant frequency Fres is lower than the center frequency FC. For example, a phase of the transmission signal may be delayed or advanced as the resonant frequency Fres decreases. For example, a phase of the transmission signal may be adjusted to a first phase θ1 when the resonant frequency Fres decreases to a first resonant frequency Fres1.

A phase of the transmission signal may be adjusted according to a second phase adjustment PA2 when the resonant frequency Fres is higher than the center frequency FC. For example, a phase of the transmission signal may be advanced or delayed as the resonant frequency Fres increases. For example, a phase of the transmission signal may be adjusted to a second phase θ2 when the resonant frequency Fres increases to a second resonant frequency Fres2.

If selected appropriately, the first phase adjustment PA1 and the second phase adjustment PA2 may be used to provide a communication distance extension (CDE) for the NFC system. This communication distance extension CDE may decrease the reduction in the communication distance D that occurs when the resonant frequency Fres is different from the center frequency FC of the transmission signal. This decrease is illustrated graphically in <FIG> as the portions of the dotted lines at the resonant frequencies Fres <NUM> and Fres2 that are between lines L1 and L2 (which are labelled CDE in <FIG>). Accordingly, by applying the first phase adjustment PA1 or the second phase adjustment PA2 the communication quality of the NFC system <NUM> may be improved.

The inventive concepts provide NFC devices that automatically detect a difference between the resonant frequency Fres and the center frequency FC of the transmission signal, and adjust a phase of the transmission signal based on the detected difference. The technical features of the inventive concepts will be described below with reference to an example of an NFC device that operates in the card mode. However, the scope and spirit of the inventive concepts are not limited to the card mode and may be applied to NFC devices that operate in the reader mode.

<FIG> is a schematic block diagram of an NFC device <NUM> according to an embodiment of the inventive concepts. It will be appreciated that the schematic block diagram of <FIG> may not illustrate all of the components of the NFC device <NUM>, but instead only illustrates certain of the signal transmission components that may be used in certain embodiments of the inventive concepts. Referring to <FIG>, the NFC device <NUM> includes a transmitter <NUM>, a transmission amplifier <NUM>, a matching circuit <NUM>, and an antenna <NUM>.

The transmitter <NUM> may operate in a phase measurement mode and a transmission mode. In the phase measurement mode, the transmitter <NUM> transmits a transmit clock CLKt to the transmission amplifier <NUM>. The transmit clock CLKt may be any appropriate waveform such as, for example, a pulse signal having a certain frequency. The transmitter <NUM> extracts an extraction clock CLKe from a waveform, which is formed in the antenna <NUM> and the matching circuit <NUM> in response to the transmit clock CLKt. The transmitter <NUM> may store information regarding a phase difference between the transmit clock CLKt and the extraction clock CLKe. In the transmission mode, the transmitter <NUM> may adjust a phase of a transmission signal based on the stored information regarding the phase difference.

The transmitter <NUM> may include, for example, a reference clock generation block <NUM>, a multiplexer <NUM>, a clock extraction block <NUM>, a comparison and selection block <NUM>, a phase lookup table <NUM>, and a phase control block <NUM>.

The reference clock generation block <NUM> may generate a reference clock CLKr. For example, the reference clock CLKr may have a center frequency that is determined by the NFC standard. For example, the reference clock CLKr may have a center frequency of <NUM>. The reference clock CLKr may be, for example, a pulse waveform. The reference clock CLKr may be transmitted to the multiplexer <NUM> and the comparison and selection block <NUM>.

The multiplexer <NUM> may receive the reference clock CLKr from the reference clock generation block <NUM> and may receive an adjusted clock CLKa from the phase control block <NUM>. In the phase measurement mode, the multiplexer <NUM> may output the reference clock CLKr as the transmit clock CLKt. The transmit clock CLKt may be transmitted to the transmission amplifier <NUM>. In the transmission mode, the multiplexer <NUM> may output the adjusted clock CLKa. Transmission information IF may be added to the adjusted clock CLKa. The adjusted clock CLKa including the transmission information IF added thereto may be transmitted to the transmission amplifier <NUM> as an information signal SIGi.

The clock extraction block <NUM> may extract the extraction clock CLKe from a waveform formed in the antenna <NUM> and the matching circuit <NUM>. For example, the clock extraction block <NUM> may output the extraction clock CLKe that has the same phase as the waveform formed in the antenna <NUM> and the matching circuit <NUM>. The extraction clock CLKe may be transmitted to the comparison and selection block <NUM> and the phase control block <NUM>.

The comparison and selection block <NUM> may compare the reference clock CLKr and the extraction clock CLKe in the phase measurement mode. In an embodiment, since the multiplexer <NUM> outputs the reference clock CLKr as the transmit clock CLKt in the phase measurement mode, the comparison and selection block <NUM> may be regarded as comparing phases of the reference clock CLKr and the extraction clock CLKe in the phase measurement mode. The comparison and selection block <NUM> may detect a phase difference △θ between the reference clock CLKr and the extraction clock CLKe based on the result of the comparison. The detected phase difference △θ may include information about a difference between the center frequency FC of the transmission signal and a resonant frequency of the antenna <NUM> and the matching circuit <NUM>.

As described with reference to <FIG> and <FIG>, the communication distance D decreases due to a path delay that is generated when the resonant frequency Fres and the center frequency FC differ from each other. The path delay may be quantified as the phase difference △θ between the reference clock CLKr and the extraction clock CLKe. That is, a difference between the resonant frequency and the center frequency may be quantified by the magnitude and sign of the phase difference △θ.

In the phase measurement mode, the comparison and selection block <NUM> may obtain phase selection information θs corresponding to the phase difference △θ with reference to the phase lookup table <NUM>. The phase selection information θs includes information about how much the phase of a transmission signal (e.g., a phase of the information signal SIGi) should be adjusted in the transmission mode to compensate for a difference between the resonant frequency and the center frequency.

As described with reference to <FIG>, an amount that the phase is to be adjusted when the resonant frequency Fres differs from the center frequency FC may be quantified. The phase lookup table <NUM> may store a plurality of phase differences △θ and corresponding phase selection information θs for each of the phase differences. This information may be stored, for example, in the form of a table. The comparison and selection block <NUM> may obtain the phase selection information θs corresponding to the phase difference △θ with reference to the phase lookup table <NUM>. The phase selection information θs may be transmitted to the phase control block <NUM>.

The phase control block <NUM> may store the phase selection information θs in the phase measurement mode. In the transmission mode, the phase control block <NUM> may adjust the extraction clock CLKe (e.g., adjust the phase of the extraction clock CLKe) based on the phase selection information θs to output the adjusted clock CLKa.

The transmitter <NUM> is described as including various blocks. The blocks included in the transmitter <NUM> may be implemented with hardware such as a semiconductor circuit or an integrated circuit, software driven in an integrated circuit, or a combination of hardware and software.

The transmission amplifier <NUM> may amplify a signal from the transmitter <NUM> and may transmit the amplified signal to the matching circuit <NUM>.

The matching circuit <NUM> may provide impedance matching with regard to the antenna <NUM>. The matching circuit <NUM> includes an inductor L and first to fourth capacitors C1 to C4. A first end of the inductor L is connected to an output of the transmission amplifier <NUM>, and a second end thereof is connected to first ends of the first and second capacitors C1 and C2. A second end of the first capacitor C1 is connected to a ground electrode to which a ground voltage is supplied. A second end of the second capacitor C2 is connected to first ends of the third and fourth capacitors C3 and C4 and the antenna <NUM>. A second end of the third capacitor C3 is connected to the ground electrode. A second end of the fourth capacitor C4 is connected to the clock extraction block <NUM> of the transmitter <NUM>. It will be appreciated that <FIG> illustrates one example matching circuit <NUM> and that matching circuits having different configurations may be provided in other embodiments. It will also be appreciated that the above-described connections may be direct or indirect connections.

<FIG> is a graph illustrating an example in which the NFC device <NUM> of <FIG> performs phase measurement and transmission in a card mode. In <FIG>, the abscissa represents time T, and the ordinate represents a service mode SM, an operating sequence SQ, a transmit signal TXS, and a receive signal RXS of the NFC device <NUM>.

Referring to <FIG> and <FIG>, the service mode SM of the NFC device <NUM> is changed from an OFF state to an ON state at a point in time T1. For example, power may be supplied to the NFC device <NUM>, or the NFC device <NUM> may be activated.

After the service mode SM is set to the ON state, the transmitter <NUM> may enter the phase measurement mode. In the phase measurement mode, the operating sequence SQ may enter a radiation interval RI at a point in time T2, and the operating sequence SQ may enter a calculation interval CI at a point in time T3. In the radiation interval RI and the calculation interval CI, the transmitter <NUM> may output the reference clock CLKr as the transmit clock CLKt. The transmit clock CLKt may form a waveform in the antenna <NUM> and the matching circuit <NUM>, and a wireless signal corresponding to the generated waveform may be radiated from the antenna <NUM>. If the waveform is stabilized during the radiation interval RI, as described with reference to <FIG>, the phase difference △θ between the reference clock CLKr and the extracted clock CLKe that is extracted from the generated waveform is determined during the calculation interval CI. The transmitter <NUM> determines and may store the phase selection information θs in the phase control block <NUM> in response to the determined phase difference △θ.

After the phase measurement mode ends, the transmitter <NUM> may enter the transmission mode. Thereafter, a signal radiated from an external reader may be received as the receive signal RXS in the antenna <NUM> at a point in time T4. For example, the receive signal RXS may be a continuous wave. The receive signal RXS may be received through a receiver (not illustrated) and may be used to supply power to the NFC device <NUM>.

The receive signal RXS may include reception information that is received at antenna <NUM> at a point in time T5. For example, the receive signal RXS may be of a form in which the reception information is added to the continuous wave. As the reception information is received, the operating sequence SQ may enter a reception interval RX. The receiver may interpret the reception information during the reception interval RX. When the reception interval RX ends, the receive signal RXS may be restored to a continuous wave that does not include the reception information.

The transmitter <NUM> may perform transmission at a point in time T6 to send transmission information as a response to the reception information that is received during the reception interval RX. The phase control block <NUM> may adjust the extraction clock CLKe which may be, for example, a clock which is extracted from the continuous wave of the receive signal RXS, based on the phase selection information θs and may output the adjusted clock CLKa. The information signal SIGi, which may comprise the adjusted clock CLKa with the transmission information IF added thereto, may be radiated as the transmit signal TXS through the antenna <NUM>.

<FIG> shows an example of waveforms of the reference clock CLKr, the transmit signal TXS, the extraction clock CLKe, and the adjusted clock CLKa when the resonant frequency Fres of the NFC device <NUM> is a first resonant frequency that coincides with the center frequency FC of the near field communication. Referring to <FIG>, <FIG>, and <FIG>, since a path delay does not exist when the resonant frequency Fres coincides with the center frequency FC, a phase may not be changed. In this case, a phase of a waveform of the transmit signal TXS coincides with a phase of the reference clock CLKr. Also, a phase of the extraction clock CLKe extracted from the transmit signal TXS coincides with a phase of the reference clock CLKr. Accordingly, the phase difference △θ is "<NUM>", and the phase selection information θs for compensating for the phase difference △θ may indicate "no phase adjustment". In the above-described case, the adjusted clock CLKa has the same phase as the extraction clock CLKe. That is, in the transmission mode, the phase control block <NUM> may output the extraction clock CLKe, which is extracted from the continuous wave of the receive signal RXS (refer to <FIG>), as the adjusted clock CLKa without phase adjustment.

<FIG> shows an example of waveforms of the reference clock CLKr, the transmit signal TXS, the extraction clock CLKe, and the adjusted clock CLKa when the resonant frequency Fres of the NFC device <NUM> is a second resonant frequency Fres1 that is less than the center frequency FC of the near field communication. Referring to <FIG>, <FIG>, and <FIG>, when the resonant frequency Fres is the second resonant frequency Fres1 that is less than the center frequency FC, a phase of a waveform of the transmit signal TXS is delayed relative to a phase of the reference clock CLKr. Also, a phase of the extraction clock CLKe that is extracted from the transmit signal TXS is delayed relative to a phase of the reference clock CLKr. As one example, the phase of the waveform of the transmit signal TXS and the phase of the extraction clock CLKe may be delayed by <NUM> degrees relative to the reference clock CLKr. In this case, the phase difference △θ is "<NUM> degrees (<NUM>°)", and the phase selection information θs for compensating for the phase difference △θ indicates "a <NUM>-degree decrease (or advance)". In this case, the adjusted clock CLKa has a phase that is advanced by <NUM> degrees relative to the extraction clock CLKe. That is, in the transmission mode, the phase control block <NUM> may output an adjusted clock CLKa that is obtained by advancing a phase of the extraction clock CLKe, which is extracted from the continuous wave of the receive signal RXS (refer to <FIG>), by <NUM> degrees.

<FIG> shows an example of waveforms of the reference clock CLKr, the transmit signal TXS, the extraction clock CLKe, and the adjusted clock CLKa when the resonant frequency Fres of the NFC device <NUM> is a third resonant frequency Fres2 that is higher than the center frequency FC of the near field communication. Referring to <FIG>, <FIG>, and <FIG>, when the resonant frequency Fres is the third resonant frequency Fres2 that exceeds the center frequency FC, the phase of the waveform of the transmit signal TXS and the phase of the extraction clock CLKe that is extracted from the transmit signal TXS are advanced relative to a phase of the reference clock CLKr. As an example, the phase of the waveform of the transmit signal TXS and the phase of the extraction clock CLKe may be advanced by <NUM> degrees relative to the reference clock CLKr. In this case, the phase difference △θ is "-<NUM> degrees (-<NUM>°)", and the phase selection information θs for compensating for the phase difference △θ may indicate "a -<NUM> degree increase (or delay)". With the above description, the adjusted clock CLKa has a phase that is delayed by <NUM> degrees relative to the extraction clock CLKe. That is, in the transmission mode, the phase control block <NUM> may output an adjusted clock CLKa that is obtained by delaying a phase of the extraction clock CLKe, which is extracted from the continuous wave of the receive signal RXS (refer to <FIG>), by <NUM> degrees.

<FIG> is a block diagram illustrating an example of the phase control block <NUM> of the NFC device <NUM> of <FIG>. Referring to <FIG> and <FIG>, the phase control block <NUM> includes a phase locked loop 116a, a phase splitter 116b, and a clock selector 116c.

The phase locked loop 116a may receive the extraction clock CLKe and output a phase locked clock CLKl that has the same frequency as the extraction clock CLKe and the same phase as the extraction clock CLKe when the transmitter <NUM> operates in the transmission mode. For example, the phase locked loop 116a may output the phase locked clock CLKl that has the same phase as the receive signal RXS or a continuous wave of the receive signal RXS before the transmission sequence TX (refer to <FIG>) starts. If the phase locked clock CLK1 is output, the phase locked loop 116a may maintain a phase of the phase locked clock CLK1 even though a phase of the extraction clock CLKe changes. That is, even though a phase of the extraction clock CLKe changes due to mixing the transmit signal TXS and the receive signal RXS in the transmission sequence TX, the phase locked loop 116a may maintain the phase locked clock CLKl.

The phase splitter 116b may receive the phase locked clock CLK1 and may output a plurality of clocks CLK1 to CLKn that have the same frequency as the phase locked clock CLK1 and have different phases. For example, the phase splitter 116b may include a plurality of delays D1 to Dn that are serially connected to each other. A time delay of each delay D1 to Dn may be smaller than a quarter of a period of the phase locked clock CLKl. The phase locked clock CLK1 may be input to the first delay D1. The phase splitter 116b may output the plurality of clocks CLK1 to CLKn.

The clock selector 116c may select one of the plurality of clocks CLK1 to CLKn as the adjusted clock CLKa based on the phase selection information θs.

In some embodiments, the phase locked loop 116a may be omitted from the phase control block <NUM>. If the phase locked loop 116a is omitted, the phase splitter 116b may generate the plurality of clocks CLK1 to CLKn using the extraction clock CLKe.

In the transmission sequence TX (refer to <FIG>), a waveform formed in the antenna <NUM> and the matching circuit <NUM> corresponds to a mixed shape of the transmit signal TXS and the receive signal RXS, and the transmit signal TXS may be dominant. Accordingly, the extraction clock CLKe may follow the transmit signal TXS. Clock adjustment by the clock selector 116c may be accumulated every clock cycle due to iteration of the process in which the transmit signal TXS is extracted as the extraction clock CLKe, the extraction clock CLKe is output as the adjusted clock CLKa after being adjusted by the clock selector 116c, and the adjusted clock CLKa is sent as the transmit signal TXS. To prevent the above-described issue, the clock selector 116c may dynamically select the plurality of clocks CLK1 to CLKn. For example, the clock selector 116c may select a clock, which is designated by the phase selection information θs, of the clocks CLK1 to CLKn as a start clock, and then, may select the same or a different clock every clock cycle. For example, the clock selector 116c may select an output of the latter delay or an output of the former delay every clock cycle.

<FIG> is a schematic block diagram that illustrates an NFC device <NUM> according to further embodiments of the inventive concepts. Referring to <FIG>, the NFC device <NUM> includes a transmitter <NUM>, a transmission amplifier <NUM>, a matching circuit <NUM>, and an antenna <NUM>.

The transmission amplifier <NUM>, the matching circuit <NUM>, and the antenna <NUM> may be the same as the transmission amplifier <NUM>, the matching circuit <NUM>, and the antenna <NUM> of <FIG>. A detailed description thereof is thus omitted.

The transmitter <NUM> includes a phase locked loop <NUM>, a multiplexer <NUM>, a clock extraction block <NUM>, a comparison and selection block <NUM>, a phase lookup table <NUM>, and a phase control block <NUM>.

In the phase measurement mode, the phase locked loop <NUM> may output a phase locked clock CLKl that has the same frequency as the extraction clock CLKe and the same phase as the extraction clock CLKe.

The multiplexer <NUM> may output the phase locked clock CLK1 to the transmission amplifier <NUM> as the transmit clock CLKt in the phase measurement mode. The multiplexer <NUM> may output the adjusted clock CLKa in the transmission mode. In the transmission mode, the information signal SIGi in which the transmission information IF is added to the adjusted clock CLKa may be transmitted to the transmission amplifier <NUM>.

The clock extraction block <NUM>, the comparison and selection block <NUM>, the phase lookup table <NUM>, and the phase control block <NUM> may operate the same as the clock extraction block <NUM>, the comparison and selection block <NUM>, the phase lookup table <NUM>, and the phase control block <NUM> of <FIG>, respectively, except that the clock extraction block <NUM> transmits the extraction clock CLKe to the phase locked loop <NUM>. A detailed description of these elements is thus omitted.

<FIG> is a graph illustrating an example in which the NFC device <NUM> of <FIG> performs phase measurement and adjustment and transmission in a card mode. In <FIG>, the abscissa represents the time T, and the ordinate represents a service mode SM, an operating sequence SQ, a transmit signal TXS, and a receive signal RXS of the NFC device <NUM>.

Referring to <FIG> and <FIG>, the service mode SM of the NFC device <NUM> is changed from an OFF state to an ON state at a point in time T1. For example, at time T1 power may be supplied to the NFC device <NUM>, or the NFC device <NUM> may be activated.

After the service mode SM is set to the ON state, a signal radiated from an external reader may be received as the receive signal RXS in the antenna <NUM> at a point in time T2. For example, the receive signal RXS may be a continuous wave. The receive signal RXS may be received through a receiver (not illustrated) and may be used to supply power to the NFC device <NUM>.

After the receive signal RXS starts (at time T2) to be received and before the reception sequence RX starts, the transmitter <NUM> may enter the phase measurement mode. In the phase measurement mode (at time T5), the operating sequence SQ may enter a radiation interval RI at a point in time T3, and the operating sequence SQ may enter a calculation interval CI at a point in time T4. In the radiation interval RI and the calculation interval CI, the phase locked loop <NUM> of the transmitter <NUM> may output the phase locked clock CLK1 that has the same phase as the receive signal RXS or a continuous wave of the receive signal RXS. The transmitter <NUM> outputs the phase locked clock CLKl as the transmit clock CLKt to the transmission amplifier <NUM>. The transmit clock CLKt may form a waveform in the antenna <NUM> and the matching circuit <NUM>, and a wireless signal corresponding to the generated waveform may be radiated from the antenna <NUM>. If the waveform is stabilized during the radiation interval RI, as described with reference to <FIG> and <FIG>, the phase difference △θ is determined during the calculation interval CI. The transmitter <NUM> determines and may store the phase selection information θs in the phase control block <NUM> in response to the determined phase difference △θ.

The receive signal RXS may include reception information (e.g., data, commands, etc.) that is received at antenna <NUM> at a point in time T5. For example, the receive signal RXS may comprise a continuous wave that has reception information added thereto. As the reception information is received at the receiver (not shown) of NFC device <NUM>, the operating sequence SQ may enter a reception interval RX. The receiver may interpret the reception information during the reception interval RX. When the reception interval RX ends, the receive signal RXS may be a continuous wave that does not include reception information.

The transmitter <NUM> may perform transmission at a point in time T6 to send transmission information (e.g., data, commands, etc.) as a response to the reception information that is received during the reception interval RX. The phase control block <NUM> may adjust the extraction clock CLKe which may be, for example, a clock which is extracted from the continuous wave of the receive signal RXS, based on the phase selection information θs, and may output the adjusted clock CLKa. The information signal SIGi, which may comprise the adjusted clock CLKa with the transmission information IF added thereto, may be radiated as the transmit signal TXS through the antenna <NUM>.

The NFC device <NUM> described with reference to <FIG> and <FIG> may automatically detect the phase selection information θs using the reference clock generation block <NUM> before near field communication starts; on the other hand, the NFC device <NUM> described with reference to <FIG> and <FIG> may detect the phase selection information θs using the receive signal RXS after near field communication starts.

<FIG> is a schematic block diagram that illustrates an NFC device <NUM> according to still further embodiments of the inventive concepts. Referring to <FIG>, the NFC device <NUM> includes a transmitter <NUM>, a transmission amplifier <NUM>, a matching circuit <NUM>, and an antenna <NUM>.

The transmission amplifier <NUM>, the matching circuit <NUM>, and the antenna <NUM> may be the same as the transmission amplifier <NUM>, the matching circuit <NUM>, and the antenna <NUM> of the NFC device <NUM> of <FIG>. Accordingly, detailed description thereof is omitted.

The transmitter <NUM> includes a clock extraction block <NUM>, a comparison and selection block <NUM>, a phase lookup table <NUM>, and a phase control block <NUM>. As described with reference to <FIG>, the phase control block <NUM> may include a phase locked loop PLL.

The phase locked loop PLL may output the phase locked clock CLK1, which has the same frequency as the extraction clock CLKe and the same phase as the extraction clock CLKe, to the transmission amplifier <NUM> as the transmit clock CLKt in the phase measurement mode. In the transmission mode, the phase locked loop PLL may adjust a phase of the phase locked clock CLK1 based on the phase selection information θs and may output the adjusted clock CLKa. The information signal SIGi, which comprises the adjusted clock CLKa with the transmission information IF added thereto, is transmitted to the transmission amplifier <NUM> in the transmission mode.

The clock extraction block <NUM>, the comparison and selection block <NUM>, the phase lookup table <NUM>, and the phase control block <NUM> may operate the same as the clock extraction block <NUM>, the comparison and selection block <NUM>, the phase lookup table <NUM>, and the phase control block <NUM> of <FIG>. Accordingly, detailed description thereof is omitted.

The transmitter <NUM> of <FIG> includes the phase locked loop <NUM> that generates the phase locked clock CLK1 in the phase measurement mode. Accordingly, as described with reference to <FIG>, the phase control block <NUM> may include the phase locked loop 116a or may not include the phase locked loop 116a. In contrast, the transmitter <NUM> of <FIG> may use the phase locked loop PLL of the phase control block <NUM> in both the phase measurement mode and the transmission mode.

<FIG> is a flowchart illustrating method of operating an NFC device according to an embodiment of the inventive concepts. Referring to <FIG>, <FIG>, <FIG>, and <FIG>, in operation S110, the transmitter <NUM>, <NUM>, or <NUM> of the NFC device <NUM>, <NUM>, or <NUM> may send a basic clock as the transmit clock CLKt to the transmit amplifier <NUM>, <NUM>, <NUM>. The basic clock may be the reference clock CLKr that is generated by the reference clock generation block <NUM> or the phase locked clock CLKl that is generated by the phase locked loop <NUM> or PLL. The transmit clock CLKt is transmitted by the NFC device as a transmit signal TXS.

In operation S120, the transmitter <NUM>, <NUM>, or <NUM> may extract, for example, the extraction clock CLKe from the transmit signal TXS.

In operation S130, the transmitter <NUM>, <NUM>, or <NUM> may compare the reference clock CLKr or CLKl to the extraction clock CLKe.

In operation S140, the transmitter <NUM>, <NUM>, or <NUM> may store phase difference information between the reference clock CLKr or CLK1 and the extraction clock CLKe, for example, the phase selection information θs or the phase difference △θ.

In operation S150, the transmitter <NUM>, <NUM>, or <NUM> may receive an external signal. For example, the transmitter <NUM>, <NUM>, or <NUM> may receive a continuous wave from an external NFC device.

In operation S160, the transmitter <NUM>, <NUM>, or <NUM> may extract a clock from the received external signal.

In operation S170, the transmitter <NUM>, <NUM>, or <NUM> may adjust a phase of the extracted clock CLKe based on the phase difference information to provide an adjusted clock CLKa.

In operation S180, the transmitter <NUM>, <NUM>, or <NUM> may transmit an information signal in synchronization with the adjusted clock CLKa.

<FIG> is a block diagram illustrating a mobile device <NUM>, according to an embodiment of the inventive concepts. Referring to <FIG>, the mobile device <NUM> includes an application processor <NUM>, a codec <NUM>, a speaker <NUM>, a microphone <NUM>, a display device <NUM>, a camera <NUM>, a modem <NUM>, a storage device <NUM>, a random access memory <NUM>, a NFC device <NUM> and a user input interface <NUM>.

The application processor <NUM> may drive an operating system that operates the mobile device <NUM> and may drive various applications on the operating system. The codec <NUM> may perform coding and decoding of signals such as, for example, an image signal. The codec <NUM> may perform a task associated with processing a voice signal or an image signal under delegation of the application processor <NUM>.

The speaker <NUM> may play a voice signal from the codec <NUM>. The microphone <NUM> may detect sound sensed from the outside, may convert the detected sound into a voice signal, and may output the voice signal to the codec <NUM>. The display device <NUM> may play an image signal from the codec <NUM>. The camera <NUM> may convert a scene in a range of vision into an electrical image signal and may output the image signal to the codec <NUM>.

The modem <NUM> may perform wireless or wired communication with an external device. In response to a request of the application processor <NUM>, the modem <NUM> may transmit data to an external device or may request data from the external device. The storage device <NUM> may be main storage of the mobile device <NUM>. The storage device <NUM> may be used to store data for a long time and may retain data stored therein even at power-off. The random access memory <NUM> may be a main memory of the mobile device <NUM>. The random access memory <NUM> may be used for the master devices, such as the application processor <NUM>, the modem <NUM>, and the codec <NUM>, to temporarily store data.

The NFC device <NUM> may be the NFC device <NUM>, <NUM>, or <NUM> described with reference to <FIG>. The NFC device <NUM> may operate as a reader or a card. The NFC device <NUM> may detect a phase difference and may adjust a phase of a transmit clock based on the detected phase difference. Accordingly, accuracy of the NFC device <NUM> may be improved, and the reliability of the mobile device <NUM> may be improved.

The user input interface <NUM> may include various devices for receiving an input from a user. For example, the user input interface <NUM> may include devices, which directly receive an input from the user, such as touch panels, touch screens, buttons, and keyboards, or devices, which indirectly receive results generated by actions of the user, such as an optical sensor, a proximity sensor, a gyroscope sensor, and a pressure sensor.

Claim 1:
A near field communication device comprising:
an antenna (<NUM>);
a transmission amplifier (<NUM>);
a matching circuit (<NUM>) connected between the antenna (<NUM>) and the transmission amplifier (<NUM>); and
a transmitter (<NUM>),
wherein the transmitter (<NUM>) comprises a reference clock generation block (<NUM>) configured to output a reference clock (CLKr),
wherein, in a phase measurement mode, the transmitter (<NUM>) is configured to output the reference clock (CLKr) as a transmit clock (CLKt), to transmit the transmit clock (CLKt) through the transmission amplifier (<NUM>) to the matching circuit (<NUM>) to form a waveform in the matching circuit (<NUM>) and the antenna (<NUM>) such that a wireless signal corresponding to the waveform is radiated from the antenna (<NUM>), to extract an extraction clock (CLKe), and to determine information relating to a phase difference between the transmit clock (CLKt) and the extraction clock (CLKe), and
wherein the transmitter (<NUM>) is further configured to control transmission of an information signal (SIGi) through the antenna (<NUM>), the transmission amplifier (<NUM>), and the matching circuit (<NUM>) based on the determined information relating to the phase difference, and
characterized in that the extraction clock (CLKe) is extracted from the waveform formed in the matching circuit (<NUM>).