Antenna coil tuning mechanism for magnetic communication

• US 10,050,677 B1
• Filed: 05/23/2017
• Issued: 08/14/2018
• Est. Priority Date: 05/23/2017
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Thoen, Steven Mark
• Primary Examiner(s): Alam, Fayyaz
• Application Number:
  US15/603,054
• Time in Patent Office: 448 Days
• Field of Search: 455 411- 413
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 2001/6912 using chirp
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 27/2613 Structure of the reference signals

Abstract

Disclosed is an integrated circuit for a near-field radio, including an inductive-capacitive (LC) tank antenna circuit designed to operate at a predetermined carrier frequency, the tank LC tank antenna circuit including a variable capacitor and an antenna element, a transmitter configured to output a channel sounding signal (CSS) to the LC tank antenna circuit, a receiver to receive the CSS and a tank response from the LC tank antenna circuit, a tank response estimator to extract the tank response of the LC tank antenna circuit by removing the CSS from the received signal and determining an oscillation frequency of the LC tank antenna circuit, and a controller to adjust a reactance of the LC tank antenna circuit to resonate the LC tank antenna circuit and change the oscillation frequency to the predetermined carrier frequency.

Claims

1. An integrated circuit for a near-field radio, comprising:

an inductive-capacitive (LC) tank antenna circuit designed to operate at a predetermined carrier frequency, the tank LC tank antenna circuit including a variable capacitor and an antenna element;

a transmitter configured to output a channel sounding signal (CSS) to the LC tank antenna circuit;

a receiver to receive the CSS and a tank response from the LC tank antenna circuit;

a tank response estimator to extract the tank response of the LC tank antenna circuit by removing the CSS from the received signal and determining an oscillation frequency of the LC tank antenna circuit; and

a controller to adjust a reactance of the LC tank antenna circuit to resonate the LC tank antenna circuit and change the oscillation frequency to the predetermined carrier frequency.

2. The integrated circuit of claim 1, wherein CSS parameters are stored in a look-up table of a memory element to enable generation of the CSS.

3. The integrated circuit of claim 1, wherein the CSS has a bandwidth around the predetermined carrier frequency.

4. The integrated circuit of claim 1, wherein the CSS is an orthogonal frequency division multiplexing (OFDM) signal.

5. The integrated circuit of claim 1, wherein the CSS is a chirp sequence.

6. The integrated circuit of claim 1, wherein the CSS is a combined orthogonal frequency division multiplexing (OFDM) signal and chirp sequence.

7. The integrated circuit of claim 1, wherein the tank response estimator determines a relative oscillation frequency offset of an antenna coil.

8. The integrated circuit of claim 1, wherein the reactance of the LC antenna circuit is a variable capacitor.

9. The integrated circuit of claim 1, wherein the reactance of the LC antenna circuit is an inductance of the antenna.

10. A method of tuning an antenna coil having a predetermined carrier frequency, comprising:

sending a single channel sounding signal (CSS) through an inductive-capacitive (LC) tank antenna circuit having inductive and capacitive components to estimate a tank response;

receiving a received signal including the CSS and a tank response from the LC tank antenna circuit;

extracting the tank response of the LC tank antenna circuit by removing the CSS from the received signal;

using the tank response to determine an oscillation frequency of the LC tank antenna circuit;

and

adjusting a reactance of the LC tank antenna circuit to resonate the LC tank antenna circuit and change the oscillation frequency to at the predetermined carrier frequency.

11. The method of claim 10, comprising reading the CSS signal from a memory element before sending it through the LC tank antenna circuit.

12. The method of claim 11, wherein CSS parameters are stored in a look-up table of the memory element to enable generation of the CSS.

13. The method of claim 10, wherein the CSS has a bandwidth around the predetermined carrier frequency.

14. The method of claim 10, comprising adjusting a resistor of the LC tank antenna circuit to tune a bandwidth of the LC tank antenna circuit.

15. The method of claim 10, comprising determining a relative oscillation frequency offset of an antenna coil.

16. The method of claim 10, wherein the CSS is an orthogonal frequency division multiplexing (OFDM) signal.

17. The method of claim 10, wherein the CSS is a chirp sequence.

18. The method of claim 10, wherein the CSS is a combined orthogonal frequency division multiplexing (OFDM) signal and chirp sequence.

19. The method of claim 10, wherein adjusting the reactance includes adjusting a capacitance of the variable capacitor.

20. The method of claim 10, wherein adjusting the reactance includes adjusting an inductance of the antenna.