DEVICE DETECTION USING LOAD MODULATION IN NEAR-FIELD COMMUNICATIONS

• US 20140113551A1
• Filed: 10/22/2012
• Published: 04/24/2014
• Est. Priority Date: 10/22/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: KRISHNAN, Koushik, Gaethke, Rainer
• Granted Patent: US 9,071,926 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device
• 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: H04B 5/0031 for data transfer
• CPC Class Codes: H04B 5/0075 using inductive coupling transformers or inductances adapted for inductive coupling H01F38/14
• CPC Class Codes: H04B 5/02 using transceiver
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04M 1/72412 using two-way short-range wireless interfaces
• CPC Class Codes: H04M 2250/04 including near field communication means, e.g. RFID
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

First and second NFC devices both seek to determine whether the other device is present and available for communication across an NFC channel. The first NFC device modulates a load in its transceiver. The second NFC device transmits a waveform. If the first NFC device detects the waveform while modulating its load, and if the second NFC device detects the load modulation while transmitting the waveform, then the two NFC devices initiate communication in accordance with a communication protocol.

Claims

1. A method of establishing communications between near-field communications (NFC) devices, the method comprising:

at a first NFC device;

modulating a load in a transceiver of the first NFC device;

while modulating the load, detecting a waveform transmitted on an NFC channel by a second NFC device; and

in response to detecting the waveform while modulating the load, communicating with the second NFC device over the channel.

2. The method of claim 1, wherein modulating the load comprises repetitively varying the load.

3. The method of claim 2, wherein:

the load comprises a resistor in a transmitter of the first NFC device; and

repetitively varying the load comprises repetitively switching the resistor in and out of a signal path.

4. The method of claim 1, wherein detecting the waveform comprises detecting an oscillating signal.

5. The method of claim 1, wherein communicating with the second NFC device comprises:

listening to the channel to determine whether the channel is idle;

determining that the channel is idle; and

in response to determining that the channel is idle, transmitting a packet to the second NFC device over the channel.

6. The method of claim 1, wherein communicating with the second NFC device comprises entering a receive mode to receive a signal from the second NFC device.

7. A method of establishing communications between near-field communications (NFC) devices, the method comprising:

at a first NFC device;

transmitting a waveform on an NFC channel;

while transmitting the waveform, detecting modulation of a load in a second NFC device; and

in response to detecting the modulation while transmitting the waveform, communicating with the second NFC device over the channel.

8. The method of claim 7, further comprising:

prior to transmitting the waveform on the channel;

listening to the channel to determine whether the channel is idle, and

determining that the channel is idle;

wherein the waveform is transmitted on the channel in response to determining that the channel is idle.

9. The method of claim 7, wherein transmitting the waveform comprises transmitting an oscillating signal.

10. The method of claim 7, wherein detecting modulation of the load comprises detecting repetitive variation of the load.

11. The method of claim 7, wherein detecting modulation of the load comprises determining that a predefined voltage satisfies a threshold.

12. The method of claim 7, wherein communicating with the second NFC device over the channel comprises entering a receive mode to receive a signal from the second NFC device.

13. The method of claim 7, wherein communicating with the second NFC device over the channel comprises:

listening to the channel to determine whether the channel is idle;

determining that the channel is idle; and

in response to determining that the channel is idle, transmitting a packet to the second NFC device over the channel.

14. A near-field communications (NFC) device, comprising:

an NFC antenna;

a transmitter to modulate a load coupled to the NFC antenna;

a receiver to receive a waveform from another NFC device via the NFC antenna; and

a controller to initiate a first portion of a protocol for communicating with the other NFC device in response to the receiver receiving the waveform while the transmitter modulates the load.

15. The NFC device of claim 14, wherein:

the load comprises a switchable resistor; and

the transmitter is to repetitively switch the resistor into and out of a signal path.

16. The NFC device of claim 14, wherein, to initiate the first portion of the protocol, the controller is to instruct the receiver to listen to an NFC channel and to instruct the transmitter to transmit a packet to the other NFC device over the channel in response to a determination that the channel is idle.

17. The NFC device of claim 14, wherein:

the transmitter is to modulate the load during a first mode and to transmit a waveform during a second mode;

the receiver comprises a detector to detect load modulation by the other NFC device; and

the controller is to initiate a second portion of the protocol in response to the detector detecting the load modulation by the other NFC device while the transmitter transmits the waveform.

18. The NFC device of claim 17, wherein the transmitter is to transmit an oscillating signal during the second mode.

19. The NFC device of claim 17, wherein, to initiate the second portion of the protocol, the controller is to activate the receiver, wherein upon activation the receiver is configured to receive a signal from the second NFC device.

20. The NFC device of claim 14, wherein the controller comprises one or more processors and memory storing instructions that, when executed by the one or more processors, cause the controller to initiate the first portion of the protocol in response to the receiver receiving the waveform while the transmitter modulates the load.

21. The NFC device of claim 20, wherein:

the transmitter is to modulate the load during a first mode and to transmit a waveform during a second mode;

the receiver comprises a detector to detect load modulation by the other NFC device; and

the memory further stores instructions that, when executed by the one or more processors, cause the controller to initiate a second portion of the protocol in response to the detector detecting the load modulation by the other NFC device while the transmitter transmits the waveform.