Method of Checking the Matching of an Antenna Connected to a NFC Component and Corresponding NFC Component

• US 20140022143A1
• Filed: 07/09/2013
• Published: 01/23/2014
• Est. Priority Date: 07/23/2012
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Tramoni, Alexandre
• Granted Patent: US 9,209,516 B2
• Time in Patent Office: Days
• US Class Current: 343/861
• CPC Class Codes: H01Q 1/50 Structural association of antennas with earthing switches, lead-in devices or lightning protectors
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/18 Monitoring during normal operation
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 5/0043 for taking measurements, e.g. using sensor coils
• CPC Class Codes: H04B 5/0081 with antenna coils loop aerials H01Q7/00
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/73 for taking measurements, e.g. using sensing coils

Abstract

An NFC component includes a first interface that can be used in reader mode and is configured to be connected to an antenna via an impedance matching external circuit. A second interface can be used in card mode and in reader mode and is configured to be connected to the antenna and to the first interface via the impedance matching external circuit. An internal module includes a first detection circuit configured to deliver a first detection signal that represents the phase antenna matching quality when the impedance matching external circuit and the antenna are indeed connected between the first interface and the second interface. The internal module is further configured to deliver a check signal from at least the first detection signal.

Claims

1. An NFC component, comprising:

a first interface that can be used in reader mode and is configured to be connected to an antenna via an external impedance matching circuit;

a second interface that can be used in card mode and in reader mode and is configured to be connected to the antenna and to the first interface via the impedance matching external circuit; and

an internal module comprising a first detection circuit configured to deliver a first detection signal that represents a phase antenna matching quality when the external impedance matching circuit and the antenna are indeed connected between the first interface and the second interface.

2. The NFC component according to claim 1, wherein the internal module is further configured to deliver a check signal from at least the first detection signal.

3. The NFC component according to claim 2, further comprising an internal matching adjustment circuit configured to adjust the antenna matching based upon the check signal.

4. The NFC component according to claim 1, further comprising an internal matching adjustment circuit that comprises:

a circuit of switched capacitors coupled between the first and second interfaces and between terminals of the second interface; and

a control circuit configured to control the switching of the capacitors.

5. The NFC component according to claim 1, wherein the first detection circuit comprises:

a generator configured to generate, on the first interface, a first voltage signal comprising rising edges;

a first processing block coupled to the generator and to the second interface and configured to receive, at the second interface, a second voltage signal resulting from the generation of the first voltage signal on the first interface;

a development circuit configured to develop predefined time windows about maximum values, respectively, of the second voltage signal; and

a first detection module configured to deliver the first detection signal having a first state when a position of a rising edge of the first voltage signal is located inside a time window.

6. The NFC component according to claim 5, wherein the development circuit comprises:

a rectifying module coupled to the second interface and configured to deliver a second voltage rectified signal having a voltage predefined level; and

a comparator having a first input coupled to an output of the rectifying module and a second input coupled to the second interface.

7. The NFC component according to claim 6, wherein the detection module comprises a logic gate having a first input connected to the output of the comparator and a second input connected to the output of the generator.

8. The NFC component according to claim 1, wherein the internal module further comprises second detection circuit configured to deliver a second detection signal that represents an amplitude antenna matching quality when the impedance matching external circuit and the antenna are indeed connected between the first interface and the second interface.

9. The NFC component according to claim 8, wherein the internal module is configured to deliver a check signal from the first detection signal and from the second detection signal.

10. The NFC component according to claim 9, wherein the second detection circuit includes a second comparator configured to compare a value of a second rectified signal with a reference value and to deliver the second detection signal, which has a first state when the value of the second rectified signal is greater than the reference value.

11. The NFC component according to claim 10, wherein the internal module includes an output circuit configured to deliver the check signal with a first state when the first detection signal and the second detection signal are both in the first state thereof.

12. The NFC component according to claim 8, wherein the internal module is further configured to deliver a check signal from at least the first detection signal and wherein the NFC component further comprises a matching adjustment circuit configured to adjust the antenna matching based upon the check signal delivered by the internal module.

13. The NFC component according to claim 12, wherein the matching adjustment circuit comprises:

a circuit of switched capacitors coupled between the first and second interfaces and between terminals of the second interface; and

a control circuit configured to control the switching of the capacitors based upon at least one of the check signal, the first detection signal or the second detection signal.

14. A system comprising:

the NFC component according to claim 1;

the antenna connected to the second interface of the component; and

the external impedance matching circuit connected to the first interface of the component as well as to the antenna.

15. An apparatus comprising the system according to claim 14.

16. The apparatus according to claim 15, wherein the apparatus comprises a cellular mobile phone.

17. A method of checking matching of an antenna, connected via an external impedance matching circuit to a first interface of an NFC component that can be used in reader mode and connected to a second interface of the NFC component that can be used in card mode and in reader mode, the method comprising:

generating a detection signal within the NFC component, the detection signal representing a phase antenna matching quality; and

generating a check signal based upon the detection signal.

18. The method according to claim 17, wherein generating the detection signal comprises:

generating, on the first interface, a first voltage signal comprising rising edges;

receiving, at the second interface, a second voltage signal resulting from generating the first voltage signal on the first interface; and

delivering the detection signal in a first state when a position of a rising edge of the first voltage signal is located inside a predefined time window of a maximum value of the second voltage signal.

19. The method according to claim 17, further comprising generating a second detection signal within the NFC component, the second detection signal representing and amplitude antenna matching quality.

20. The method according to claim 19, wherein generating the check signal comprises generating an overall detection signal that represents the phase and amplitude antenna matching quality based on the detection signal and the second detection signal.

21. The method according to claim 19, wherein generating the second detection signal comprises comparing a value of a second voltage rectified signal with a reference value and delivering the second detection signal in a first state when the value of the second voltage rectified signal is greater than the reference value.

22. The method according to claim 19, further comprising adjusting the matching of the antenna based upon at least one of the check signal, the detection signal or the second detection signal.

23. The method according to claim 22, wherein the adjusting comprises switching at least one switched capacitor of an internal circuit of switched capacitors that are connected between the first and second interfaces and between terminals of the second interface of the NFC component, the switching being controlled by at least one of the check signal, the detection signal or the second detection signal.

24. The method according to claim 17, further comprising adjusting the matching of the antenna based upon at least one of the check signal or the detection signal.

25. An NFC component, comprising:

an interface configured to be connected to an antenna via an external impedance matching circuit, the interface including a first interface terminal and a second interface terminal;

a diode bridge coupled between the first interface terminal and the second interface terminal and including an output;

a comparator with a first input coupled to the output of the diode bridge and a second input coupled to the second interface terminal;

a voltage signal generator; and

a logic gate with a first input coupled to an output of the comparator and a second input coupled to an output of the voltage signal generator.

26. The NFC component according to claim 25, further comprising a second interface, wherein the second interface can be used in reader mode and is configured to be connected to the antenna via the external impedance matching circuit and wherein the interface can be used in card mode and in reader mode.

27. The NFC component according to claim 26, wherein the second interface comprises a third interface terminal and a fourth interface terminal and wherein the external impedance matching circuit comprises:

a first capacitor coupled between the first interface terminal and the third interface terminal;

a second capacitor coupled between the second interface terminal and the fourth interface terminal; and

a third capacitor coupled between the first interface terminal and the second interface terminal.

28. The NFC component according to claim 27, further comprising a circuit of switched capacitors coupled to the first, second and third capacitors.

29. The NFC component according to claim 25, further comprising:

an analog-to-digital converter with an input coupled to the output of the diode bridge;

a register;

a second comparator with a first input coupled to an output of the analog-to-digital converter and a second input coupled to an output of the register; and

a second logic gate with a first input coupled to an output of the second comparator and a second input coupled to an output of the logic gate.