NFC CARD READER, SYSTEM INCLUDING NFC CARD READER, AND A METHOD OF OPERATING THE SAME

• US 20160105220A1
• Filed: 10/13/2015
• Published: 04/14/2016
• Est. Priority Date: 10/14/2014
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Hyoung Hwan Roh, Hyun Jae Kang, Jun H.O. Kim, Min Woo Lee
• Inventors: KIM, Jun Ho, LEE, Min Woo, KANG, Hyun Jae, ROH, Hyoung Hwan
• Granted Patent: US 9,900,053 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A near-field communication (NFC) card reader may include a monitor configured to measure an amplitude of a magnetic field induced by an antenna; a gain controller configured to determine an amplification gain based on the measured amplitude of the magnetic field and output a gain control signal; a signal restoration unit configured to receive a carrier signal and a data signal that overlaps with the carrier signal via the antenna, and restore the data signal from the received signals; and a variable-gain amplifier configured to amplify the data signal restored by the signal restoration unit according to the gain control signal.

Claims

1. A near-field communication (NFC) card reader configured to communicate with an NFC card, the NFC card reader comprising:

a monitoring circuit configured to measure an amplitude of a magnetic field induced by an antenna;

a gain controller configured to determine an amplification gain based on the measured amplitude of the magnetic field, and to output a gain control signal based on the amplification gain;

a signal restoration circuit configured to,

receive, via the antenna, a received signal, the received signal including a carrier signal and a data signal that overlaps with the carrier signal, and

restore the data signal from the received signal; and

a variable-gain amplifier configured to amplify the restored data signal according to the gain control signal.

2. The NFC card reader of claim 1, wherein the signal restoration unit comprises:

a mixer configured to mix the carrier signal with an oscillation signal to generate a mixed signal; and

a low-pass filter configured to low-pass filter the mixed signal, wherein

the oscillation signal has a same frequency as the carrier signal.

3. The NFC card reader of claim 1, wherein the monitoring circuit is configured to digitize the measured amplitude of the magnetic field to generate a digital output code, and

the gain controller determines the amplification gain corresponding to the digital output code.

4. The NFC card reader of claim 3, wherein the monitoring circuit comprises:

a rectifier configured to rectify the received signal; and

an analog-digital converter (ADC) configured to convert an output signal of the rectifier into the digital output code which is a digital signal.

5. The NFC card reader of claim 3, wherein the gain controller is configured to determine the amplification gain based on a gain table, the gain table storing the amplification gain corresponding to the digital output code.

6. The NFC card reader of claim 3, wherein the gain controller is configured to determine the amplification gain by based on the output code and at least one reference value.

7. The NFC card reader of claim 1, wherein

the card reader is configured to,

determine, during a card detection period, whether the NFC card reader is contacted by the NFC card;

continuously radiate, during a continuous wave period, the magnetic field for a period of time after the card reader determines that the NFC card reader is contacted by the NFC card;

measure, in at least a part of the continuous wave period, an amplitude of the magnetic field;

transmitting, during a transmission period, output data to the NFC card; and

receive, during a receiving period, input data from the NFC card, wherein

the amplification gain of the input data is determined based on the amplitude of the magnetic field measured during at least part of the continuous wave period.

8. The NFC card reader of claim 7, wherein

the NFC card reader is configured to determine whether the NFC card reader is contacted by the NFC card by measuring the amplitude of the magnetic field during the card detection period, and

the NFC card reader is configured to determine a gain of the variable-gain amplifier based on the amplitude of the magnetic field measured in the continuous wave period.

9. The NFC card reader of claim 1, wherein the variable-gain amplifier comprises:

an operational amplifier;

a first resistor connected to a first input node of the operational amplifier; and

a second resistor connected between the first input node and an output node of the operational amplifier, wherein

at least one of the first and second resistors has a variable resistance value that varies according to the gain control signal.

10. The NFC card reader of claim 1, wherein the variable-gain amplifier comprises:

an operational amplifier;

a first capacitor connected to a first input node of the operational amplifier; and

a second capacitor connected between the first input node and an output node of the operational amplifier, wherein

at least one of the first and second capacitors has a capacitance value that varies according to the gain control signal.

11. A method of operating a near-field communication (NFC) card reader, the NFC card reader configured to communicate with an NFC card, the method comprising:

measuring a voltage of a carrier signal received via an antenna;

determining an amplification gain of a data signal based on the measured voltage of the carrier signal;

receiving, via the antenna, a received signal including the carrier signal and the data signal, the data signal overlapping with the carrier signal;

restoring the data signal from the received signal; and

amplifying the restored data signal based on the amplification gain.

12. The method of claim 11, wherein the determining the amplification gain comprises:

determining a range of the measured voltage based on the measured voltage and at least one reference value; and

selecting the amplification gain based on the range of the measured voltage.

13. The method of claim 12, wherein the selecting the amplification gain selects the amplification gain using a gain table, the gain table storing amplification gains corresponding to a plurality of ranges.

14. The method of claim 11, further comprising:

determining, during a card detection period, whether the NFC card reader is contacted by the NFC card;

radiating, during a continuous wave period, the magnetic field by continuously generating the carrier signal for a period of time after the NFC card reader is contacted by the NFC card;

transmitting, during a transmission period, output data to the NFC card; and

receiving, during a receiving period, input data from the NFC card.

15. The method of claim 14, wherein

the measuring the voltage of the carrier signal and the determining the amplification gain are performed during the continuous wave period, and

the restoring the data signal and the amplifying the restored data signal are performed during the receiving period.

16. The method of claim 14, further comprising:

generating, during the card detection period, a magnetic field by the antenna at set time intervals to determine whether the NFC card reader is contacted by the NFC card, and wherein

the measuring the voltage of the carrier signal includes continuously generating, during the continuous wave period, the magnetic field by the antenna for the period of time.

17. A near field communication (NFC) system comprising:

an antenna;

an NFC card reader configured to detect accessing of an NFC card, and to communicate with the NFC card, the NFC card reader including,

a monitoring circuit configured to measure an amplitude of a magnetic field induced by the antenna;

a gain controller configured to determine an amplification gain based on the amplitude of the magnetic field, and to output a gain control signal based on the amplification gain;

a signal restoration circuit configured to,

receive, via the antenna, a received signal, the received signal including a carrier signal and a data signal overlapping the carrier signal, and

restore the data signal from the received signals; and

a variable-gain amplifier configured to amplify the restored data signal according to the gain control signal.

18. The NFC system of claim 17, wherein

the monitoring circuit is configured to digitize the amplitude of the magnetic field to generate a digital output code, and

the gain controller is configured to determine the amplification gain corresponding to the digital output code.

19. The NFC system of claim 17, wherein the NFC card reader is configured to,

determine, during a card detection period, whether the NFC card reader is contacted by the NFC card;

continuously radiate, during a continuous wave period, the magnetic field for a period of time after the NFC card reader is contacted by the NFC card;

transmit, during a transmission period, output data to the NFC card; and

receive, during a receiving period, input data from the NFC card. wherein

the gain controller is configured to determine the amplification gain based on the amplitude of the magnetic field measured during at least a part of the continuous wave period.

20. The NFC system of claim 19, wherein, the NFC card reader is configured to,

generate, during the card detection period, a magnetic field by the antenna at set time intervals to determine whether the NFC card reader is contacted by the NFC card,

continuously generate, in the continuous wave period, the magnetic field by the antenna for the period of time, and

determine a gain of the variable-gain amplifier based on the amplitude of the magnetic field measured by the monitoring circuit in the continuous wave period.

21-26. -26. (canceled)