Near field communication device, terminal device having the same, and operation method of the near field communication device
A near field communication (NFC) device includes a phase detector for receiving a reference clock signal, detecting a phase of the reference clock signal, outputting a generated clock signal having a frequency synchronized with the reference clock signal, and storing phase information of the generated clock signal as a first digital code. A phase delay calculator compares the phase of the generated clock signal applied from the phase detector and a reference phase to calculate a delta value while performing an active load modulation (ALM) operation and stores the delta value as a second digital code. A transmission clock signal generator reflects phase information stored as the first digital code and the second digital code to output a transmission clock signal. Accordingly, the NFC device controls the phase of the transmission clock signal applied to the antenna of the reader device to have optimal load modulation amplitude (LMA).
1 . A near field communication (NFC) device comprising:
a phase detector configured to receive a reference clock signal, detect a phase of the reference clock signal, output a generated clock signal having a frequency synchronized with the reference clock signal, and store phase information of the generated clock signal as a first digital code;
a phase delay calculator configured to
compare a phase of the generated clock signal with a reference phase to calculate a delta value while performing an active load modulation (ALM) operation, wherein the delta value corresponds to a phase difference between the phase of the generated clock signal and the reference phase, and
store the delta value as a second digital code; and
a transmission clock generator configured to reflect phase information stored as the first digital code and the second digital code to output a transmission clock signal.
2 . The NFC device of claim 1 , further comprising a transmission clock amplifier configured to amplify and output the transmission clock signal.
3 . The NFC device of claim 1 , wherein the transmission clock generator comprises:
a digital-time converter for converting the first digital code and the second digital code into a time domain, and
a voltage control oscillator for controlling an output oscillation frequency based on the generated clock signal.
4 . The NFC device of claim 1 , wherein the reference clock signal comprises a first reference clock signal input to the phase detector in a first section and a second reference clock signal input to the phase detector in a second section, after the first section.
5 . The NFC device of claim 4 , wherein a first transmission clock signal based on the first reference clock signal is not transmitted to a reader device in the first section and a second transmission clock signal based on the second reference clock signal is transmitted to the reader device in the second section.
6 . The NFC device of claim 4 , wherein the first reference clock signal is a signal generated by an approach of a reader device and the second reference clock signal corresponds to a first transmission clock signal output based on the first reference clock signal.
7 . The NFC device of claim 4 , wherein the transmission clock signal comprises a first transmission clock signal output from the transmission clock generator in the first section and a second transmission clock signal output from the transmission clock generator in the second section, the second reference clock signal corresponding to a first transmission clock signal based on the first reference clock signal.
8 . The NFC device of claim 7 , the phase information stored as the first digital code is reflected in the first transmission clock signal.
9 . The NFC device of claim 7 , wherein the phase information stored as the first digital code and the second digital code is reflected in the second transmission clock signal.
10 . The NFC device of claim 1 , wherein a load modulation amplitude based on the transmission clock signal appears constantly in a negative direction.
11 . The NFC device of claim 10 , wherein the transmission clock signal allows a magnitude of the load modulation amplitude to have a maximum value.
12 . The NFC device of claim 1 , wherein a phase of the generated clock signal is greater than a phase of the reference clock signal.
13 . The NFC device of claim 1 , wherein the delta value is determined by additional delay information that includes delay information according to a matching network, impedance distribution, and coupling with a reader device.
14 . The NFC device of claim 1 , wherein the delta value comprises a first delta value when a phase of the generated clock signal is greater than the reference phase, a second delta value when a phase of the generated clock signal is the same as the reference phase, and a third delta value when a phase of the generated clock signal is smaller than the reference phase.
15 . The NFC device of claim 1 , wherein the transmission clock generator reflects phase information related to a path delay in real time to output the transmission clock signal.
16 . The NFC device of claim 1 , wherein a phase of the transmission clock signal synchronized to an antenna of a reader device is different from a phase of the reference clock signal.