Controlling Antenna Characteristics of a Near Field Communications (NFC) Device

• US 20130002033A1
• Filed: 06/30/2011
• Published: 01/03/2013
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: FUCHS, Franz Xaver
• Granted Patent: US 8,957,548 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 5/50 Feeding or matching arrangements for broad-band or multi-band operation

Abstract

An apparatus and method is disclosed to control antenna characteristic of a near field communications (NFC) device. The apparatus and method may tune a resonant frequency of an antenna module of the NFC device to compensate for manufacturing tolerances of the antenna module. The NFC device may cause the antenna module to operate in a first configuration for a first period of time that is characterized by a compensation resonant frequency and a second configuration for a second period of time that is characterized by an actual resonant frequency. The NFC device causes the antenna module to continuously switch between the first configuration and the second configuration such that on average, a resonant frequency of the antenna module is approximately equal to an expected resonant frequency of the antenna module.

Claims

1. An antenna module, comprising:

a resonant tuned circuit configured to operate in a first configuration and a second configuration, the first configuration being characterized as resonating at a compensation resonant frequency and the second configuration being characterized as resonating at an actual resonant frequency of the resonant tuned circuit; and

a tuning control module configured to cause the resonant tuned circuit to operate in the first configuration for a first period of time and in the second configuration for a second period of time.

2. The antenna module of claim 1, wherein the resonant tuned circuit comprises:

a compensation circuit configured to be introduced into the resonant tuned circuit in the first configuration and to be removed from the resonant tuned circuit in the second configuration.

3. The antenna module of claim 2, wherein the compensation is configured to be introduced into the resonant tuned circuit for the first period of time such that the resonant tuned circuit resonates at the compensation resonant frequency and to be removed from the resonant circuit for the second period of time such that the resonant tuned circuit resonates at the actual resonant frequency.

4. The antenna module of claim 1, wherein manufacturing tolerances of the resonant tuned circuit cause the actual resonant frequency to differ from an expected resonant frequency of the resonant tuned circuit.

5. The antenna module of claim 4, wherein the expected resonant frequency represents a resonant frequency of the resonant tuned circuit without the manufacturing tolerances.

6. The antenna module of claim 1, wherein the tuning control module is further configured to cause the resonant tuned circuit to continuously switch between the first configuration and the second configuration such that, on average, a resonant frequency of the resonant tuned circuit is approximately equal to an expected resonant frequency of the resonant tuned circuit.

7. The antenna module of claim 6, wherein for a given second time period, the first time period is given as:

8. The antenna module of claim 1, wherein the tuning control module comprises:

a switch tuning control circuit configured to provide a tuning control signal at a first logical level for the first time period and at a second logical level for the second time period; and

a switching module configured to cause the resonant tuned circuit to operate in the first configuration when the tuning control signal is at the first logical level and in the second configuration when the tuning control signal is at the second logical level.

9. The antenna module of claim 8, wherein the switching module is further configured to operate in a non-conducting state when the tuning control signal is at the first logical level and in a conducting state when the tuning control signal is at the second logical level.

10. The antenna module of claim 9, wherein the resonant tuned circuit comprises:

a compensation circuit configured to be introduced into the resonant tuned circuit when the switching module is operating in the non-conducting state and to be removed from the resonant tuned circuit when the switching module is operating in the conducting state.

11. The antenna module of claim 10, wherein the resonant tuned circuit includes a first node and a second node, and

wherein the switching module is further configured to couple the first node to the second node in the conducting state to remove the compensation circuit from the resonant tuned circuit.

12. A method for tuning a resonant tuned circuit, comprising:

(a) determining an actual resonant frequency of the resonant tuned circuit;

(b) determining a compensation resonant frequency of the antenna module;

(c) determining a first time period to tune the resonant tuned circuit to a first configuration, the first configuration being characterized as resonating at a compensation resonant frequency,

(d) determining a second time period to tune the resonant tuned circuit to a second configuration, the second configuration being characterized as resonating at an actual resonant frequency,

(e) tuning the resonant tuned circuit to the first configuration for the first time period and the second configuration for the second time period.

13. The method of claim 12, wherein step (a) comprises:

(e)(i) introducing a compensation circuit into the resonant tuned circuit for the first period of time such that the resonant tuned circuit resonates at the compensation resonant frequency; and

(e)(ii) removing the compensation circuit from the resonant tuned circuit for the second period of time such that the resonant tuned circuit resonates at the actual resonant frequency.

14. The method of claim 12, wherein step (e) comprises:

(e)(i) continuously switching between the first configuration for the first time period and the second configuration for the second time period such that, on average, a resonant frequency of the resonant tuned circuit is approximately equal to an expected resonant frequency of the resonant tuned circuit.

15. The method of claim 12, wherein step (c) comprises:

(c)(i) determining the first time period, wherein for a given second time period, the first time period is given as;

16. The method of claim 12, wherein step (d) comprises:

(d)(i) determining the second time period, wherein for a given first time period, the second time period is given as;

17. The method of claim 12, wherein step (e) comprises:

(e)(i) generating a tuning control signal at a first logical level for the first time period and at a second logical level for the second time period; and

(e)(ii) tuning the resonant tuned circuit to the first configuration when the tuning control signal is at the first logical level and to the second configuration when the tuning control signal is at the second logical level.

18. The method of claim 17, wherein step (e)(ii) comprises:

(e)(ii)(A) operating a switching module in a non-conducting state when the tuning control signal is at the first logical level and in a conducting state when the tuning control signal is at the second logical level.

19. The method of claim 18, wherein step (e)(ii) further comprises:

(e)(ii)(B) introducing a compensation circuit into the resonant tuned circuit when the switching module is operating in the non-conducting state; and

(e)(ii)(C) removing the compensation circuit from the resonant tuned circuit when the switching module is operating in the conducting state.

20. The method of claim 19, wherein the resonant tuned circuit includes a first node and a second node, and wherein step (e)(ii)(C) comprises:

(e)(ii)(C)(1) coupling the first node to the second node in the conducting state to remove the compensation circuit from the resonant tuned circuit.