NEAR FIELD COMMUNICATION DEVICES, SYSTEMS, AND METHODS USING Q FACTOR ADJUSTMENTS

• US 20140256253A1
• Filed: 03/06/2014
• Published: 09/11/2014
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Ii-Jong Song, Jong-Pil Cho
• Inventors: Cho, Jong-Pil, Song, II-Jong
• Granted Patent: US 9,596,003 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 7/10148 the step consisting of dynamically tuning the resonant circuit of the interrogation device that is emitting the interrogation signal, e.g. for impedance matching inside of the interrogation device for tuning related to loop aerials in general H01Q7/00
• CPC Class Codes: G06K 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

An NFC (near field communication) device can include a resonance unit and an NFC chip. The resonance unit may communicate with an external device through an electromagnetic wave. The NFC chip can provide output data to the resonance unit, receive input data from the resonance unit, and can reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and can maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.

Claims

1. An NFC (near field communication) device comprising:

a resonance unit configured to make data communication with an external device through an electromagnetic wave; and

an NFC chip configured to provide output data to the resonance unit, to receive input data from the resonance unit, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.

2. The NFC device of claim 1, wherein the NFC chip connects a terminal connected to the resonance unit to a ground voltage through a pull-down load when the signal receive operation is performed in the card mode and cuts off the terminal connected to the resonance unit from the ground voltage in the reader mode and when the signal transmit operation is performed in the card mode.

3. The NFC device of claim 1, wherein the NFC chip measures a voltage supplied from the resonance unit and controls a reduction degree of the Q factor of the resonance unit based on a magnitude of the measured voltage when the signal receive operation is performed in the card mode.

4. An NFC (near field communication) device comprising:

a resonance unit configured to generate a first voltage in response to an electromagnetic wave;

a rectifier configured to generate a second voltage by rectifying the first voltage;

a regulator configured to generate an internal voltage having a voltage level of a constant magnitude by using the second voltage to output the internal voltage to a first node; and

a Q (quality) sink unit connected between the first node and a ground voltage, the Q sink unit being turned on to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and being turned off to maintain the Q factor in a reader mode and when a signal transmit operation is performed in the card mode.

5. The NFC device of claim 4, wherein the Q sink unit comprises:

a Q sink controller configured to generate a Q sink signal enabled when the signal receive operation is performed in the card mode and disabled in the reader mode and when the signal transmit operation is performed in the card mode; and

a pull-down unit configured to connect the first node to the ground voltage through a pull-down load when the Q sink signal is enabled and to cut off the first node from the ground voltage when the Q sink signal is disabled.

6. The NFC device of claim 5, further comprising:

a central processing unit (CPU) configured to generate a mode signal that represents the card mode or the reader mode and the signal receive operation or the signal transmit operation when the mode is the card mode,

wherein the Q sink controller generates the Q sink signal based on the mode signal.

7. The NFC device of claim 5, wherein the pull-down unit comprises:

a switch connected to the first node and turned on in response to the Q sink signal; and

a current source connected between the switch and the ground voltage to generate a current having a constant magnitude.

8. The NFC device of claim 5, wherein the pull-down unit comprises:

a slew control unit configured to generate first to n^th Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^th Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled;

first to n^th switches connected to the first node and turned on in response to the first to n^th Q sink sub-signals, respectively; and

first to n^th current sources connected between the first to n^th switches and the ground voltage, respectively, to generate a current having a constant magnitude.

9. The NFC device of claim 5, wherein the pull-down unit comprises:

a switch connected to the first node and turned on in response to the Q sink signal; and

a resistor connected between the switch and the ground voltage.

10. The NFC device of claim 5, wherein the pull-down unit comprises:

a slew control unit configured to generate first to n^th Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^th Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled;

first to n^th switches connected to the first node and turned on in response to the first to n^th Q sink sub-signals, respectively; and

first to n^th resistors connected between the first to n^th switches and the ground voltage, respectively.

11. The NFC device of claim 4, further comprising:

a field detector configured to receive the first voltage to generate a field intensity signal corresponding to a magnitude of the first voltage,

wherein the Q sink unit controls a reduction degree of the Q factor of the resonance unit based on the field intensity signal when the signal receive operation is performed in the card mode.

12. The NFC device of claim 11, wherein the Q sink unit comprises:

a Q sink controller configured to generate a Q sink signal enabled when the signal receive operation is performed in the card mode and disabled in the reader mode and when the signal transmit operation is performed in the card mode and to generate a Q factor tuning signal based on the field intensity signal; and

a pull-down unit configured to connect the first node to the ground voltage through a pull-down load having a magnitude corresponding to the Q factor tuning signal when the Q sink signal is enabled and to cut off the first node from the ground voltage when the Q sink signal is disabled.

13. The NFC device of claim 12, wherein the pull-down unit comprises:

a switch connected to the first node and turned on in response to the Q sink signal; and

a variable current source connected between the switch and the ground voltage to generate a current having a magnitude corresponding to the Q factor tuning signal.

14. The NFC device of claim 12, wherein the pull-down unit comprises:

a slew control unit configured to generate first to n^th Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^th Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled;

first to n^th switches connected to the first node and turned on in response to the first to n^th Q sink sub-signals, respectively; and

first to n^th variable current sources connected between the first to n^th switches and the ground voltage, respectively, to generate a current having a magnitude corresponding to the Q factor tuning signal.

15. The NFC device of claim 12, wherein the pull-down unit comprises:

a switch connected to the first node and turned on in response to the Q sink signal; and

a variable resistor connected between the switch and the ground voltage and having a resistance with a magnitude corresponding to the Q factor tuning signal.

16. The NFC device of claim 12, wherein the pull-down unit comprises:

a slew control unit configured to generate first to n^th Q sink sub-signals, which are sequentially enabled at a first time interval, when the Q sink signal is enabled and to generate first to n^th Q sink sub-signals, which are sequentially disabled at the first time interval, when the Q sink signal is disabled;

first to n^th switches connected to the first node and turned on in response to the first to n^th Q sink sub-signals, respectively; and

first to n^th variable resistors connected between the first to n^th switches and the ground voltage, respectively, and having a resistance with a magnitude corresponding to the Q factor tuning signal.

17. An NFC (near field communication) device comprising:

a resonance unit configured to generate an electromagnetic wave corresponding to a transmit signal received from a transmit terminal in a reader mode; and

a transmit unit configured to generate the transmit signal corresponding to output data to provide the transmit data to the transmit terminal in the reader mode, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor when a signal transmit operation is performed in the card mode.

18. The NFC device of claim 17, wherein the transmit unit connects the transmit terminal to a supply voltage through a pull-up load or connects the transmit terminal to a ground voltage through a pull-down load based on the output data in the reader mode, connects the transmit terminal to the ground voltage through the pull-down load when the signal receive operation is performed in the card mode, and cuts off the transmit terminal from the ground voltage and the supply voltage when the signal transmit operation is performed in the card mode.

19. The NFC device of claim 17, wherein the transmit unit comprises:

a pull-up transistor connected between the supply voltage and the transmit terminal;

a pull-down transistor connected between the ground voltage and the transmit terminal; and

a driving unit configured to selectively turn on one of the pull-up transistor and the pull-down transistor based on the output data in the reader mode, to turn off the pull-up transistor while turning on the pull-down transistor when the signal receive operation is performed in the card mode, and to turn off the pull-up transistor and the pull-down transistor when the signal transmit operation is performed in the card mode.

20. The NFC device of claim 19, further comprising:

a central processing unit (CPU) configured to generate a mode signal that represents the card mode or the reader mode and the signal receive operation or the signal transmit operation when the mode is the card mode,

wherein the driving unit drives the pull-yup transistor and the pull-down transistor based on the mode signal.

21. The NFC device of claim 17, wherein the transmit unit comprises:

first to n^th pull-up transistors connected in parallel between the supply voltage and the transmit terminal;

first to n^th pull-down transistors connected in parallel between the ground voltage and the transmit terminal; and

a driving unit configured to turn on the first to n^th pull-up transistors or the first to n^th pull-down transistors based on the output data in the reader mode, to turn off the first to n^th pull-up transistors while sequentially turning on the first to n^th pull-down transistors at a first time interval when the signal receive operation is performed in the card mode, and to turn off the first to n^th pull-up transistors while sequentially turning off the first to n^th pull-down transistors at the first time interval when the signal transmit operation is performed in the card mode.

22. The NFC device of claim 17, further comprising:

a field detector configured to measure a voltage supplied from the resonance unit to generate a field intensity signal corresponding to a magnitude of the measured voltage in the card mode,

wherein the transmit unit controls a reduction degree of the Q factor of the resonance unit based on the field intensity signal when the signal receive operation is performed in the card mode.

23. The NFC device of claim 22, wherein the transmit unit comprises:

first to n^th pull-up transistors connected in parallel between the supply voltage and the transmit terminal;

first to n^th pull-down transistors connected in parallel between the ground voltage and the transmit terminal; and

a driving unit configured to turn on the first to n^th pull-up transistors or the first to n^th pull-down transistors based on the output data in the reader mode, to select k pull-down transistors (k is a positive integer equal to or less than n) among the first to n^th pull-down transistors based on the field intensity signal in the card mode, to turn off the first to n^th pull-up transistors and (n−

k) pull-down transistors, which are not selected, while sequentially turning on the k pull-down transistors at a first time interval when the signal receive operation is performed in the card mode, and to turn off the first to n^th pull-up transistors and (n−

k) pull-down transistors, which are not selected, while sequentially turning off the k pull-down transistors at the first time interval when the signal transmit operation is performed in the card mode.

24. An electronic system comprising:

an NFC (near field communication) device configured to make communication with an external device through an NFC;

a memory device configured to store output data and input data; and

an application processor configured to control operations of the NFC device and the memory device,

wherein the NFC device comprises;

a resonance unit configured to transmit the output data to the external device through an electromagnetic wave; and

an NFC chip configured to provide the output data to the resonance unit, to receive the input data from the resonance unit, to reduce a Q factor (quality factor) of the resonance unit when a signal receive operation is performed in a card mode, and to maintain the Q factor of the resonance unit in a reader mode and when a signal transmit operation is performed in the card mode.

25. A method of operating a Near Field Communication (NFC) device, the method comprising:

operating a resonance circuit with a first quality factor responsive to at least a first operation of the NFC device; and

operating the resonance circuit with a second quality factor, that is less than the first quality factor, responsive to at least a second operation of the NFC device that is different than the first operation of the NFC device.

26. The method of claim 25 wherein operating the resonance circuit with a second quality factor comprises reducing a gain of the resonance circuit from a first gain value to a second gain value.

27. The method of claim 26 wherein the first and second gain values comprise first and second voltage gain values, respectively.

28. The method of claim 26 wherein the first gain value of the resonance circuit is associated with the first operation of the NFC device and the second gain value of the resonance circuit is associated with the second operation of the NFC device.

29. The method of claim 26 wherein the first gain value is defined as a maximum value for a response of the resonance unit as a function of frequency over a first bandwidth and the second gain value is defined as a maximum value for a response of the resonance unit as a function of frequency over a second bandwidth;

wherein reducing a gain of the resonance circuit from a first gain value to a second gain value further comprises;

increasing the bandwidth of the resonance unit from the first bandwidth to the second bandwidth.

30. The method of claim 25 wherein the first operation of the NFC device comprises at least one of an operation in a reader mode for the NFC device and a signal transmit operation in a card mode for the NFC device.

31. The method of claim 25 wherein the second operation of the NFC device comprises a signal receive operation in a card mode for the NFC device.

32. The method of claim 29 wherein operating the resonance circuit with a second quality factor comprises electrically coupling a terminal of the resonance circuit to a ground voltage through a pull-down circuit in the second operation of the NFC device.

33. The method of claim 30 wherein operating the resonance circuit with a second quality factor comprises electrically decoupling a terminal of the resonance circuit from a ground voltage in the first operation of the NFC device.

34. The method of claim 25 wherein operating the resonance circuit with a second quality factor comprises:

determining a magnitude of a voltage signal provided by the resonance circuit;

providing a signal indicating an amount of reduction to the quality factor based on the magnitude of the voltage signal to provide the second quality factor; and

operating the resonance circuit with the second quality factor second responsive to the second operation of the NFC device.