Methods and apparatus for improving remote NFC device detection using a low power oscillator circuit

Patent metadata

Field	Value
Publication number	US-9698872-B2
Application number	US-201313920670-A
Country	US
Kind code	B2
Filing date	Jun 18, 2013
Priority date	Jun 18, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A method, an apparatus, and a computer program product for inductive communication are provided in connection with providing mechanisms for detecting a remote NFC device without excessive power consumption. In one example, a communications device is equipped to monitor frequency oscillations associated with a NFC antenna using a calibrated LPO, determine that a number of occurrences of the frequency oscillations from a reference frequency is greater than a frequency deviation threshold, and perform a NFC polling procedure in response to the determination.

First claim

What is claimed is:

1. A method of wireless communications, comprising:
monitoring frequency oscillations associated with a near field communication (NFC) antenna and a matching network using a calibrated low power oscillator (LPO) connected to the NFC antenna, wherein the monitoring comprises:
generating the frequency oscillations using the LPO; and
counting a number of occurrences of the frequency oscillations using a frequency counter connected to the LPO, wherein the frequency oscillations are at a frequency which is a function of an impedance of the NFC antenna;

determining that the number of occurrences of the frequency oscillations is greater than a frequency deviation threshold from a reference frequency;
waking up an NFC chip and a crystal oscillator coupled to the NFC antenna and matching network in response to the determination; and
performing a NFC polling procedure using the NFC chip and the crystal oscillator to determine whether the frequency deviation is based on the presence of a remote NFC device in response to the determination.

2. The method of claim 1 , further comprising:
calibrating the LPO using the crystal oscillator, wherein the crystal oscillator provides a comparatively higher quality reference clock value to a reference clock value associated with the LPO.

3. The method of claim 2 , wherein the calibration is performed periodically.

4. The method of claim 2 , wherein the calibration is performed when a subsystem that uses the crystal oscillator is activated.

5. The method of claim 2 , wherein the calibration is performed once per an integer number of wake-up cycles, wherein the integer is greater than one.

6. The method of claim 1 , wherein the monitoring is performed continuously.

7. The method of claim 1 , wherein the number of occurrences is averaged over a time duration.

8. The method of claim 1 , wherein the reference frequency is adaptively determined based on one or more previously determined values.

9. The method of claim 1 , wherein the number of occurrences of the frequency oscillations is based on changes in impedance associated with the NFC antenna.

10. An apparatus for wireless communications, comprising:
means for monitoring frequency oscillations associated with a near field communication (NFC) antenna and a matching network using a calibrated low power oscillator (LPO) connected to the NFC antenna, wherein the means for monitoring are further configured to:
generate the frequency oscillations using the LPO connected to the NFC antenna; and
count a number of occurrences of occurrences of the frequency oscillations using a frequency counter connected to the LPO, wherein the frequency oscillations are at a frequency which is a function of an impedance of the NFC antenna;

means for determining that the number of occurrences of the frequency oscillations is greater than a frequency deviation threshold from a reference frequency;
means for waking up an NFC chip and a crystal oscillator coupled to the NFC antenna and matching network in response to the determination; and
means for performing a NFC polling procedure using the NFC chip and the crystal oscillator to determine whether the frequency deviation is based on the presence of a remote NFC device in response to the determination.

11. The apparatus of claim 10 , further comprising:
means for calibrating the LPO using the crystal oscillator, wherein the crystal oscillator provides a comparatively higher quality reference clock value to a reference clock value associated with the LPO.

12. The apparatus of claim 11 , wherein the calibration is performed periodically.

13. The apparatus of claim 11 , wherein the calibration is performed when a subsystem that uses the crystal oscillator is activated.

14. The apparatus of claim 11 , wherein the calibration is performed once per an integer number of wake-up cycles, wherein the integer is greater than one.

15. The apparatus of claim 10 , wherein the monitoring is performed continuously.

16. The apparatus of claim 10 , wherein the number of occurrences is averaged over a time duration.

17. The apparatus of claim 10 , wherein the reference frequency is adaptively determined based on one or more previously determined values.

18. The apparatus of claim 10 , wherein the number of occurrences of the frequency oscillations is based on changes in impedance associated with the NFC antenna.

19. A non-transitory computer-readable medium comprising code for:
monitoring frequency oscillations associated with a near field communication (NFC) antenna and a matching network using a calibrated low power oscillator (LPO) connected to the NFC antenna, wherein the code for monitoring the frequency oscillations comprises code for:
generating the frequency oscillations using the LPO coupled to the NFC antenna; and
counting a number of occurrences of the frequency oscillations using a frequency counter connected to the LPO, wherein the frequency oscillations are at a frequency which is a function of an impedance of the NFC antenna;

determining that the number of occurrences of the frequency oscillations is greater than a frequency deviation threshold from a reference frequency;
waking up an NFC chip including a crystal oscillator coupled to the NFC antenna and matching network in response to the determination; and
performing a NFC polling procedure using the NFC chip and the crystal oscillator to determine whether the frequency deviation is based on the presence of a remote NFC device in response to the determination.

20. The non-transitory computer-readable medium of claim 19 , further comprising code for:
calibrating the LPO using the crystal oscillator, wherein the crystal oscillator provides a comparatively higher quality reference clock value to a reference clock value associated with the LPO.

21. The non-transitory computer-readable medium of claim 20 , wherein the calibration is performed periodically.

22. The non-transitory computer-readable medium of claim 20 , wherein the calibration is performed when a subsystem that uses the crystal oscillator is activated.

23. The non-transitory computer-readable medium of claim 20 , wherein the calibration is performed once per an integer number of wake-up cycles, wherein the integer is greater than one.

24. The non-transitory computer-readable medium of claim 19 , wherein the monitoring is performed continuously.

25. The non-transitory computer-readable medium of claim 19 , wherein the number of occurrences is averaged over a time duration.

26. The non-transitory computer-readable medium of claim 19 , wherein the reference frequency is adaptively determined based on one or more previously determined values.

27. The non-transitory computer-readable medium of claim 19 , wherein the number of occurrences of the frequency oscillations is based on changes in impedance associated with the NFC antenna.

28. An apparatus for wireless communications, comprising:
a near field communication (NFC) antenna and matching network;
a calibrated low power oscillator (LPO) circuit connected to the NFC antenna and the matching network and configured to monitor frequency oscillations associated with the NFC antenna;
an NFC chip;
a crystal oscillator; and
a processing system coupled to at least one of the LPO circuit or the NFC antenna and matching network and configured to:
generate t

Assignees

• Qualcomm Inc

Inventors

• Haverinen Anssi Kaleva
• Reynolds Todd
• Wong Angelica
• Brockenbrough Roger
• Lee Sang-Min

Classifications

• H04B5/77 Primary

  for interrogation · CPC title

• H04B5/266

  One coil at each side, e.g. with primary and secondary coils · CPC title

• H04B5/0031 Primary

  Electricity · mapped topic

• H04B5/0081

  Electricity · mapped topic

• Y02B60/50

  Cross-Sectional Technologies · mapped topic