Near-field communication (NFC) system and method for high performance NFC and wireless power transfer with small antennas

• US 10,666,325 B2
• Filed: 03/17/2017
• Issued: 05/26/2020
• Est. Priority Date: 04/01/2016
• Status: Active Grant

• Current Assignee: Hangzhou Chivotech Limited
• Original Assignee: Nan Jing Qiwei Technology Limited
• Inventors: Zhou, Ruogu, Wang, Qingbin
• Primary Examiner(s): Pan, Yuwen
• Assistant Examiner(s): Tran, Paul P
• Application Number:
  US15/461,609
• Publication Number:
  US 20170288736A1
• Time in Patent Office: 1,166 Days
• Field of Search: 455 411, 455 412, 455411
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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: 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: H01Q 1/248 provided with an AC/DC converting device, e.g. rectennas
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A method for a near-field communication (NFC) tag to perform NFC and wireless power transfer (WPT) with an NFC reader, the NFC tag having an antenna resonant circuit, of which a quality factor (Q-factor) is no lower than 50 in a high-Q mode of the NFC tag, and no higher than 25 in a low-Q mode of the NFC tag. The method includes continuously preforming steps of detecting an NFC radio frequency (RF) field generated by the NFC reader, measuring strength of the NFC RF field, operating in the high-Q mode for the WPT upon determining that the strength of the NFC RF field is larger than a predetermined threshold, operating in the low-Q mode for the NFC upon determining that the strength of the NFC RF field is smaller than the predetermined threshold, and transmitting a response back to the NFC reader.

Claims

1. A near-field communication (NFC) tag for concurrent NFC and wireless power transfer (WPT) with an NFC reader, comprising:

a high quality factor (Q-factor) antenna resonant circuit of which a Q-factor is no lower than 50,

a low Q-factor antenna resonant circuit of which the Q-factor is no higher than 25, the high Q-factor and low Q-factor antenna resonant circuits having no shared component;

a modulator connected to the high Q-factor antenna resonant circuit to perform load modulation;

a demodulator connected to the low Q-factor antenna resonant circuit to demodulate a signal received by the low Q-factor antenna resonant circuit; and

an interface that is connected to both the modulator and the demodulator, and serves as a data exchange hub for the modulator and the demodulator to communicate with an external device connected to the NFC tag, wherein

the NFC tag is configured to

receive a first NFC signal transmitted by the NFC reader using the low Q-factor antenna resonant circuit and demodulating the first NFC signal using the demodulator, and

receive energy contained in an NFC radio frequency (RF) magnetic field transferred by the NFC reader in the WPT and transmit a second NFC signal to the NFC reader, both using the high Q-factor antenna resonant circuit, the second NFC signal being an amplitude modulated signal modulated by the modulator.

2. The NFC tag of claim 1, wherein the NFC tag is powered by the energy received through the WPT, and is configured to power the external device connected thereto.

3. The NFC tag of claim 1, wherein the high Q-factor and low Q-factor antenna resonant circuits are configured to be activated simultaneously.

4. A method for a near-field communication (NFC) tag to perform NFC and wireless power transfer (WPT) with an NFC reader, the NFC tag having

a high quality factor (Q-factor) antenna resonant circuit, of which a Q-factor is no lower than 50,

a low Q-factor antenna resonant circuit, of which the Q-factor is no higher than 25, the high Q-factor and low Q-factor antenna resonant circuits having no shared component,

a modulator connected to the high Q-factor antenna resonant circuit to perform load modulation,

a demodulator connected to the low Q-factor antenna resonant circuit to demodulate a signal received by the low Q-factor antenna resonant circuit, and

an interface that is connected to both the modulator and the demodulator, and serves as a data exchange hub for the modulator and the demodulator to communicate with an external device connected to the NFC tag,

the method comprising:

repeatedly preforming steps of detecting an NFC radio frequency (RF) field generated by the NFC reader using the low Q-factor antenna resonant circuit and the demodulator;

measuring strength of the NFC RF field, upon determining that the strength of the NFC RF field is higher than a predetermined threshold that has a fixed hysteretic value preset based on a load level of the external device, performing the WPT using the high Q-factor antenna resonant circuit, and transmitting a response back to the NFC reader using the high Q-factor antenna resonant circuit, the response being an amplitude modulated signal modulated by the modulator.

5. The method of claim 4, wherein the NFC tag is configured to supply power to the external device, and, after determining that the strength of the NFC RF field is higher or lower than the predetermined threshold, connects or disconnects the power supply to the external device, respectively.

6. The method of claim 4, wherein after the signal reception, the NFC tag switches transmits the response within a time t1, t1 being smaller than a maximum time interval between a transmission time by the NFC reader and a response time by the NFC tag as defined in ISO14443 standards.