Near field communication devices, systems, and methods using Q factor adjustments

• US 10,148,319 B2
• Filed: 02/28/2017
• Issued: 12/04/2018
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Cho, Jong-Pil, Song, Il-Jong
• Primary Examiner(s): Yun, Eugene
• Application Number:
  US15/445,028
• Publication Number:
  US 20170170878A1
• Time in Patent Office: 644 Days
• Field of Search: 455 411
• 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. A Near Field Communication (NFC) chip comprising:

a central processing unit (CPU) configured to generate a mode signal that represents a card mode or a reader mode; and

a transmit circuit configured to determine a quality factor (Q factor) based on the mode signal,

wherein the mode signal represents a signal receive operation or a signal transmit operation when the mode signal represents the card mode.

2. The NFC chip of claim 1,

wherein the transmit circuit connects between a supply voltage and a ground voltage, and includes at least one transistor.

3. The NFC chip of claim 2,

wherein the transmit circuit comprises a driving circuit configured to drive the at least one transistor based on the mode signal.

4. The NFC chip of claim 1,

wherein the transmit circuit connects a 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 output data in the reader mode, and

the transmit circuit connects the transmit terminal to the ground voltage through the pull-down load when the signal receive operation is performed in the card mode, or cuts off the transmit terminal from the ground voltage and the supply voltage when the signal transmit operation is performed in the card mode.

5. The NFC chip of claim 4, further comprising:

a driving circuit configured to selectively turn on one of a pull-up transistor and a 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.

6. The NFC chip of claim 1,

wherein the transmit circuit comprises:

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

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

a driving circuit configured to selectively turn on one of the pull-up transistor and the pull-down transistor based on output data and the mode signal.

7. The NFC chip of claim 1, wherein the transmit circuit comprises:

first to nth pull-up transistors connected in parallel between a supply voltage and a transmit terminal;

first to nth pull-down transistors connected in parallel between a ground voltage and the transmit terminal; and

a driving circuit configured to turn on the first to nth pull-up transistors or the first to nth pull-down transistors based on output data in the reader mode, configured to turn off the first to nth pull-up transistors and sequentially turn on the first to nth pull-down transistors during a first time interval when the signal receive operation is performed in the card mode, and configured to turn off the first to nth pull-up transistors and sequentially turn off the first to nth pull-down transistors during the first time interval when the signal transmit operation is performed in the card mode.

8. The NFC chip of claim 1, further comprising:

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

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

9. The NFC chip of claim 1 wherein the mode signal is configured to represent the card mode or the read mode at a first time and the mode signal is configured to represent the signal receive operation or the signal transmit operation at a second time.

10. The NFC chip of claim 1 wherein the card mode or the read mode and the signal receive operation or the signal transmit operation are time multiplexed onto the mode signal at different times.