Positioning guidance for increasing reliability of near-field communications
View Patent ↗To promote ease of use, as well as a reduction in bit error rates during extended data exchange between a coupled NFC tag/reader pair, signal strength is measured from a plurality of NFC tag antennas each positioned differently with respect to a common reader field, and differences in signal strength are used to determine an optimum positioning of the tag, or tag emulator, with respect to the reader. Alternative embodiments may include signal time of flight for determining orientation of the NFC antennas within the reader field. Information is generated by the tag, or tag emulator, and output by the tag, or tag emulator, such that a user may direct the positioning of the tag, or tag emulator, for improved communication with the reader.
1. A method of operating an NFC-enabled device, comprising:
detecting, by the NFC-enabled device, a respective current in each of a plurality of NFC antennas having antenna terminals, in an NFC antenna array, by measuring an averaged DC current when a shunt regulator is operating and measuring a peak-to-peak voltage across the antenna terminals when the peak-to-peak voltage is less than a threshold voltage of the shunt regulator, the respective currents induced by a common NFC reader field; and
determining, based at least in part on the magnitude of each of the respective currents, if changing a position of the NFC-enabled device would improve communicative interaction with the NFC reader field;
wherein the NFC antenna array is disposed on the NFC-enabled device.
2. The method of claim 1 , further comprising:
generating position-correction information if changing the position of the NFC-enabled device would improve communicative interaction with the NFC reader field.
3. The method of claim 2 , further comprising:
providing user-perceivable information based on the position-correction information.
4. The method of claim 3 , further comprising:
repeating:
detecting, by the NFC-enabled device, the respective current in each of the plurality of NFC antennas in the NFC antenna array, the respective currents induced by the common NFC reader field;
determining, based at least in part on the magnitude of each of the respective currents, if changing the position of the NFC-enabled device would improve communicative interaction with the NFC reader field;
generating positive correction information if changing the position of the NFC-enabled device would improve communicative interaction with the NFC reader field; and
providing user-perceivable information based on the position-correction information.
5. The method of claim 4 , wherein each of the plurality of NFC antennas nominally has the same shape and dimensions.
6. The method of claim 4 , wherein each of the plurality of NFC antennas nominally has the same material composition.
7. The method of claim 4 , wherein the position-correction information comprises information representing how far the center of the NFC antenna array should be moved in an x direction and a y direction to align the NFC antenna array to the reader field.
8. The method of claim 3 , wherein the user-perceivable information comprises a visual display representing the distance and direction to move the NFC-enabled device in order to align the NFC antenna array with the reader field.
9. The method of claim 8 , wherein aligning the NFC antenna array with the reader field comprises centering the NFC antenna array within the reader field.
10. The method of claim 8 , wherein aligning the NFC antenna array with the reader field comprises positioning the NFC antenna array within the reader field to obtain an increased level of coupling between the reader field and the NFC antenna array.
11. A method of operating an NFC tag emulator, comprising:
coupling to an NFC reader field at each of a plurality of NFC antennas having terminals, each of the plurality of NFC antennas disposed on the tag emulator;
determining, by the tag emulator, a relative coupling strength at each of the plurality of NFC antennas by measuring an averaged DC current when a shunt regulator is operating and measuring a peak-to-peak voltage across the antenna terminals when the peak-to-peak voltage is less than a threshold voltage of the shunt regulator; and
generating, by the tag emulator, position-correction information based at least in part on the relative coupling strength at each of the plurality of antennas;
wherein each of the plurality of NFC antennas has a known spaced-apart relationship to the other NFC antennas of the plurality of NFC antennas.
12. The method of claim 11 , wherein each of the plurality of NFC antennas nominally has the same physical dimensions.
13. The method of claim 11 , wherein at least one of the plurality of NFC antennas has dimensions that are different from the dimensions of the other NFC antennas of the plurality of NFC antennas.
14. The method of claim 11 , wherein the plurality of NFC antennas are co-planar.
15. The method of claim 11 , wherein determining the relative strength and generating the position-correction information are performed by computational resources disposed on the tag emulator.
16. An NFC-enabled device, comprising:
an NFC antenna array having at least three antennas, each of the at least three antennas having a corresponding pair of antenna terminals and a corresponding shunt regulator;
a plurality of field strength detector circuits, each one of the plurality of field strength detector circuits coupled to a corresponding one of the at the least three antennas, and each one of the plurality of field strength detector circuits configured to measure an averaged DC current when the shunt regulator coupled to its corresponding antenna is operating, and further configured to measure a peak-to-peak voltage across the antenna terminals when the peak-to-peak voltage is less than a threshold voltage of the shunt regulator;
a computational resource coupled to each of the plurality of field strength detector circuits, the computational resource configured, based at least in part on the signals indicative of the strength of the received signal at each antenna of the NFC antenna array, to determine whether the NFC-enabled device should be repositioned for improved communicative interaction with a reader device; and
a visual display device coupled to the computational resource;
wherein the visual display, under control of the computational resource, provides a user-perceivable output indicating the distance and direction for repositioning the NFC-enabled device.
17. The NFC-enabled device of claim 16 , wherein the at least three antennas are coplanar with each other.
18. The NFC-enabled device of claim 16 , wherein each of the at least three antennas nominally have the same shape and dimensions.
19. The NFC-enabled device of claim 16 , wherein each of the at least three antennas nominally comprise the same materials.
20. The NFC-enabled device of claim 18 , wherein each of the at least three antennas is positioned symmetrically with respect to each other.
21. The method of claim 3 , further comprising harvesting energy by the NFC-enabled device from an energization field.
22. The method of claim 15 , further comprising harvesting energy by the NFC-enabled device from an energization field.