NFC Communicators Implementing Coil Voltage Reduction Circuitry

• US 20130273845A1
• Filed: 06/10/2013
• Published: 10/17/2013
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Innovision Limited (Broadcom, Inc.)
• Inventors: Bangs, Joakim, Wilson, Robin, Fuchs, Franz
• Granted Patent: US 9,143,199 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• 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 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/26 using coils

Abstract

An NFC communicator has an antenna circuit to enable inductive coupling, via an RF H field, of the NFC communicator and another near field RF communicator in near field range. The antenna circuit has an antenna element coupled in parallel with a first capacitor to form a parallel LC circuit. The antenna element has an antenna coil in series with a second capacitor to reduce the voltage to which circuitry of the NFC communicator is subjected by a received RF H field. Alternatively or additionally, receive circuitry of the NFC communicator may be coupled to only a proportion of the antenna coil to reduce the voltage to which circuitry of the NFC, communicator is subjected by a received RF H field.

Claims

1. A near field communication (NFC) device, comprising:

a coupling component coupled in parallel with a first capacitance, the coupling component including a second capacitance coupled in series with an inductance having a tap;

a transmitter coupled to the coupling component via a junction formed between the first and the second capacitance; and

a receiver coupled to the coupling component via the tap.

2. The NFC device of claim 1, wherein the transmitter is further configured to transmit a signal utilizing a first and a second transmit signal line, wherein the first transmit signal line is coupled to the coupling component via the junction, and wherein the second transmit signal line is coupled to the coupling component via an end terminal associated with the inductance.

3. The NFC device of claim 1, wherein the tap is from among a first and a second tap, and wherein the receiver is further configured to receive a signal from the coupling component utilizing a first and a second receive signal line coupled to the first and second taps, respectively.

4. The NFC device of claim 3, wherein the first and second taps are positioned substantially equidistant from a center point of the inductance.

5. The NFC device of claim 1, wherein the inductance is an autotransformer coil.

6. The NFC device of claim 2, wherein the first transmit signal line is coupled to the coupling component via a third capacitance coupled in series between the transmitter and the junction, and

wherein the second transmit signal line is coupled to the end terminal via a fourth capacitance coupled in series between the transmitter and the end terminal.

7. The NFC device of claim 1, wherein the second capacitance is from among a second and a third capacitance, and wherein the inductance is coupled between the second and third capacitances.

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

a resistive element coupled in parallel with the coupling component.

9. A near field communication (NFC) device, comprising:

a coupling component including a coil and a capacitance coupled in series with the coil, the coil having a first terminal, a second terminal, a first tap, and a second tap, a total inductance of the coil being represented by a first inductance between the first and second terminals;

a transmitter coupled to the coupling component; and

a receiver coupled to the first and second taps,

wherein a portion of the total inductance is represented by a second inductance between the first and second taps.

10. The NFC device of claim 9, wherein the transmitter is further configured to transmit a signal utilizing a first and a second transmit signal line, wherein the first transmit signal line is coupled to the coupling component via the first terminal, and wherein the second transmit signal line is coupled to the coupling component via the capacitance.

11. The NFC device of claim 9, wherein the receiver is further configured to receive a signal from the coupling component utilizing a first and a second receive signal line coupled to the first and second taps, respectively.

12. The NFC device of claim 9, wherein the first and second taps are positioned substantially equidistant from a center point of the coil.

13. The NFC device of claim 9, further comprising:

a second capacitance coupled in parallel with the coupling component.

14. The NFC device of claim 9, further comprising:

a resistive element coupled in parallel with the coupling component.

15. The NFC device of claim 10, wherein the first transmit signal line is coupled to the first terminal via a second capacitance coupled in series between the transmitter and the first terminal, and

wherein the second transmit signal line is coupled to the capacitance via a third capacitance coupled in series between the transmitter and the capacitance.

16. The NFC device of claim 9, wherein the capacitance is from among a first and a second capacitance, and wherein the coil is coupled between the first and second capacitances.

17. A near field communication (NFC) device, comprising:

a coupling component including an autotransformer having a first end terminal, a second end terminal, and a tap terminal;

a transmitter coupled to the first end terminal; and

a receiver coupled to the tap terminal,

wherein the transmitter is further configured to cause a first voltage to be formed between the first and second end terminals during a signal transmission, and

wherein the receiver is further configured to receive a second voltage less than the first voltage at the tap terminal during the signal transmission.

18. The NFC device of claim 17, wherein the transmitter is coupled to the first end terminal via a capacitance coupled in series between the transmitter and the first end terminal.

19. The NFC device of claim 17, wherein the coupling component further comprises:

a capacitance coupled in series with the autotransformer.

20. The NFC device of claim 19, wherein the capacitance is from among a first and a second capacitance, and wherein the autotransformer is coupled between the first and second capacitances.