Near-field communications device

1. A near-field communications device, comprising:

an energy harvesting circuit configured to be coupled to a near-field antenna that is responsive to non-propagating quasi-static near-field energy;

wherein the harvesting circuit is configured to harvest energy from the non-propagating quasi-static near-field energy; and

wherein the harvesting circuit includes a harvesting filter configured to input a first set of near-field energy and output a second set of near-field energy;

wherein the second set of near-field energy is a sub-set of the first set of near-field energy;

wherein the near-field communications device is configured to receive a desired near-field communications signal from the first set of near-field energy; and

wherein the desired near-field communications signal is substantially blocked by the harvesting filter.

2. The device of claim 1 :

wherein the near-field communications device is configured to receive near-field energy from the first set of near-field energy that does not include a desired near-field communications signal; and

wherein the near-field energy that does not include the desired near-field communications signal is substantially passed by the harvesting filter.

3. The device of claim 1 :

wherein the harvesting filter includes a minima gain at a blocking frequency.

4. The device of claim 3 :

wherein the blocking frequency is substantially aligned with a center frequency of the desired near-field communications signal.

5. The device of claim 4 :

wherein the center frequency of approximately 10.6 MHz.

6. The device of claim 1 :

wherein the harvesting filter has minima gains at multiple blocking frequencies; and

wherein each minima is substantially aligned with center frequencies of multiple desired near-field communications signals.

7. The device of claim 1 :

wherein the harvesting filter is a band-pass filter having a set of passed frequencies; and

wherein the second set of near-field energy is only within the set of passed frequencies.

8. The device of claim 1 :

wherein the harvesting filter is either a high-pass filter or a low-pass filter having a respective set of either high-passed frequencies or low-passed frequencies; and

wherein the second set of near-field energy is only within the set of passed frequencies.

9. The device of claim 1 :

wherein the harvesting circuit further includes a bypass switch;

wherein the harvesting circuit is configured to harvest energy from the first set of near-field energy if the bypass switch control signal is present; and

wherein the harvesting circuit is configured to harvest energy from the second set of near-field energy if the bypass switch control signal is absent.

10. The device of claim 9 :

further comprising a communications circuit;

wherein the communications circuit is configured to generate the bypass switch control signal when the communications circuit is either in a standby state, disabled state, or turned off state.

11. The device of claim 10 :

wherein the communications circuit is configured to periodically, aperiodically, or randomly switch from either the standby state, disabled state, or turned off state to another state that permits the communications circuit to search or receive the desired near field communication signal.

12. The device of claim 10 :

wherein the harvesting circuit is configured to harvest and store the near-field energy in an energy storage device; and

wherein the communications circuit is configured to drain power from the energy storage device only in either the standby state, disabled state, or turned off state.

13. The device of claim 1 :

further comprising a communications circuit;

wherein the communications circuit includes a communications filter;

wherein the communications filter includes a maxima gain at a pass frequency; and

wherein the pass frequency is substantially aligned with a center frequency of the desired near-field communications signal.

14. The device of claim 1 :

wherein the near-field antenna is responsive to non-propagating quasi-static near-field electric (E-field) energy; and

wherein the harvesting circuit is configured to harvest energy from the E-field energy.

15. The device of claim 13 :

wherein the near-field antenna includes a set of conductive plates responsive to the E-field energy;

wherein the conductive plates are connectable to the harvesting filter; and

wherein the harvesting circuit is configured to harvest and store the E-field energy in an energy storage device.

16. The device of claim 1 :

wherein the harvesting circuit includes a rectifier and a power regulator; and

wherein the rectifier and power regulator are configured to harvest and store the second set of near-field energy in an energy storage device.

17. The device of claim 1 :

wherein the near-field communications device is configured to be located proximate to a conductive structure; and

wherein the near-field antenna receives the non-propagating quasi-static near-field energy from the conductive structure.

18. The device of claim 17 :

wherein the conductive structure is at least one of: a human body, a vehicle, or a door security device.

19. The device of claim 1 :

wherein the near-field communications device is embedded in at least one of: a wearable device, an earbud, a medical monitoring device, a smartwatch or an implant.