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

• US 10,153,809 B2
• Filed: 03/17/2017
• Issued: 12/11/2018
• Est. Priority Date: 04/01/2016
• Status: Active Grant

• Current Assignee: Hangzhou Chivotech Limited
• Original Assignee: Fusens Technology Limited
• Inventors: Zhou, Ruogu, Wang, Qingbin
• Primary Examiner(s): Maung, Nay A
• Assistant Examiner(s): Fleming-Hall, Erica
• Application Number:
  US15/461,580
• Publication Number:
  US 20170288734A1
• Time in Patent Office: 634 Days
• 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 5/24 Inductive coupling
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A device for near-field communication (NFC) and wireless power transfer. The device has an antenna resonant circuit that includes an antenna for transmitting and receiving signals, a multi-Q antenna matching circuit for adjusting a Q-factor of the antenna resonant circuit, and an antenna driver for driving the antenna through the multi-Q antenna matching circuit. The device also includes a microcontroller (MCU) configured to control the multi-Q antenna matching circuit to switch between a high-Q mode for wireless power transfer and a low-Q mode for NFC.

Claims

1. A device for near-field communication (NFC) and wireless power transfer, comprising:

an antenna resonant circuit that includes

an antenna for transmitting and receiving signals,

a switch and a resistor connected in series, the serially-connected switch and resistor being connected in parallel to the antenna, and

an antenna matching circuit, connected in parallel to the serially-connected switch and resistor, for adjusting impedance of the antenna,

the switch being configured to turn on or off to cause the antenna resonant circuit to enter respectively a high-Q mode in which the Q-factor of the antenna resonant circuit is no lower than 50, and a low-Q mode in which the Q-factor of the antenna resonant circuit is no higher than 25, and

an antenna driver for driving the antenna through the switch, the resistor and the antenna matching circuit; and

a microcontroller (MCU) configured to

turn off or on the switch, so as to switch a mode of the antenna resonant circuit between the high-Q mode and the low-Q mode, and control the antenna resonant circuit to transmit, via the antenna,

an unmodulated carrier signal when the antenna resonant circuit is in the high-Q mode, so as to transfer wireless power, and

a modulated signal when the antenna resonant circuit is in the low-Q mode, so as to perform near-field communication, wherein

the antenna resonant circuit has a lower bandwidth in the high-Q mode than in the low-Q mode.

2. The device of claim 1, further comprising

a modulator connected to the antenna driver, for generating the modulated signal to be transmitted by the antenna;

a demodulator connected to the antenna, for demodulating a signal received by the antenna, the demodulator and modulator being connected to the MCU;

a data interface connected to the MCU via a FIFO (first in first out buffer) for data exchange with another device;

a power supply for providing power to the device; and

a clock system for providing clock signals to the device.

3. The device of claim 1, wherein the antenna driver has output impedance smaller than 5 ohm.

4. The device of claim 1, wherein the antenna has

an inductance in a range of 1 uH to 10 uH,

an area in a range of 100 mm² to 5000 mm², and

a Q value higher than 100.

5. The device of claim 1, wherein the MCU controls to switch the antenna resonant circuit between the high-Q mode and the low-Q mode in real-time.

6. The device of claim 1, wherein the antenna matching circuit is a PI matching circuit.

7. A device for near-field communication (NFC) and wireless power transfer, comprising:

an antenna resonant circuit that includes

an antenna for transmitting and receiving signals,

a multi-Q antenna matching circuit for adjusting a quality factor (Q-factor) of the antenna resonant circuit, the multi-Q antenna matching circuit including

a Q-factor tuning switch configured to be turned on and off, and

a Q-factor tuning resistor connected in series with the Q-factor tuning switch,

the multi-Q antenna matching circuit being so configured that the turning-off and turning-on of the Q-factor tuning switch cause the antenna resonant circuit to enter respectively a high-Q mode in which the Q-factor of the antenna resonant circuit is no lower than 50, and a low-Q mode in which the Q-factor of the antenna resonant circuit is no higher than 25, and

an antenna driver for driving the antenna through the multi-Q antenna matching circuit; and

a microcontroller (MCU) configured to

turn off or on the Q-factor tuning switch, so as to switch a mode of the antenna resonant circuit between the high-Q mode and the low-Q mode, and control the antenna resonant circuit to transmit, via the antenna,

an unmodulated carrier signal when the antenna resonant circuit is in the high-Q mode, so as to transfer wireless power, and

a modulated signal when the antenna resonant circuit is in the low-Q mode, so as to perform near-field communication,

the antenna resonant circuit having a lower bandwidth in the high-Q mode than in the low-Q mode,

wherein the antenna matching circuit has an insertion loss smaller than 1 db.

8. The device of claim 7, further comprising

a modulator connected to the antenna driver, for generating the modulated signal to be transmitted by the antenna;

a demodulator connected to the antenna via the multi-Q antenna matching circuit, for demodulating a signal received by the antenna, the demodulator and modulator being connected to the MCU;

a data interface connected to the MCU via a FIFO (first in first out buffer) for data exchange with another device;

a power supply for providing power to the device; and

a clock system for providing clock signals to the device.

9. The device of claim 7, wherein the multi-Q antenna matching circuit further includes an antenna matching circuit, connected in parallel to the serially-connected Q-factor tuning switch and Q-factor tuning resistor, for adjusting impedance of the antenna.

10. The device of claim 9, wherein the antenna matching circuit is a PI matching circuit.

11. The device of claim 7, wherein the antenna driver has output impedance smaller than 5 ohm.

12. The device of claim 7, wherein the antenna has

an inductance in a range of 1 uH to 10 uH,

an area in a range of 100 mm² to 5000 mm², and

a Q value higher than 100.

13. The device of claim 7, wherein the MCU controls to switch the antenna resonant circuit between the high-Q mode and the low-Q mode in real-time.

14. The device of claim 7, wherein the serially-connected Q-factor tuning resistor and Q-factor tuning switch are connected to the antenna in parallel.