Wireless power transfer using tunable metamaterial systems and methods
The present disclosure provides system and methods for optimizing the tuning of impedance elements associate with sub-wavelength antenna elements to attain target radiation and/or field patterns. Both static and variable (tunable) antenna systems may be manufactured. Static embodiments may be entirely passive in some embodiments. A scattering matrix (S-Matrix) of field amplitudes for each of a plurality of modeled lumped ports, N, may be determined that includes a plurality of lumped antenna ports, N a , with impedance values corresponding to the impedance values of associated impedance elements and at least one modeled external port, N e , located external to the antenna system at a specified radius vector. Impedance values may be identified through an optimization process, and the impedance elements may be tuned (dynamically or statically) to attain a specific target radiation pattern.
1. A method of manufacturing a static wireless power transmitter, comprising:
determining a scattering matrix (S-Matrix) of field amplitudes for each of a plurality of lumped ports associated with a wireless power transmitter, including
a plurality of lumped antenna ports wherein each lumped antenna port corresponds to an impedance value of a lumped impedance element in communication with at least one sub-wavelength antenna element of the wireless power transmitter,
wherein the at least one sub-wavelength antenna element is configured to scatter received electromagnetic fields, and
at least one lumped external port located physically external to the wireless power transmitter,
wherein the S-Matrix is expressible in terms of an impedance matrix, Z Matrix, with impedance values of each of the plurality of lumped ports;
identifying a target electromagnetic radiation pattern of the wireless power transmitter defined in terms of target field amplitudes in the S Matrix for the at least one lumped external port;
determining an optimized port impedance vector, {z n }, of impedance values for each of the lumped antenna ports that results in an S-Matrix element for the at least one lumped external port that approximates the target field amplitude for an operating frequency;
forming a plurality of sub-wavelength antenna elements configured to scatter received electromagnetic fields; and
forming a plurality of impedance elements in communication with the plurality of sub-wavelength antenna elements with impedance values corresponding to the optimized impedance vector {z n }.
2. The method of claim 1 , wherein the formed plurality of sub-wavelength antenna elements are configured to scatter electromagnetic fields generated by a source external to the manufactured wireless power transmitter.
3. The method of claim 1 , wherein the formed plurality of sub-wavelength antenna elements are configured to scatter electromagnetic fields received from a slot in a transmission line.
4. The method of claim 1 , further comprising forming a transmission line coupled to the plurality of sub-wavelength elements,
wherein the formed plurality of sub-wavelength antenna elements are configured to transmit electromagnetic fields received from the transmission line.
5. The method of claim 1 , further comprising electromagnetically coupling an antenna to the formed plurality of sub-wavelength elements.
6. The method of claim 1 , wherein each impedance element is associated with a unique dielectric loading, such that the impedance value of each impedance element is independently selected to correspond to the optimized impedance vector {z n }.
7. The method of claim 1 , wherein the electromagnetic fields received by the plurality of sub-wavelength antenna elements are generated by at least one location on a transmission line.
8. The method of claim 1 , wherein the plurality of sub-wavelength antenna elements is divided into at least two groups,
wherein sub-wavelength antenna elements within each group are separated from one another by no more than half of an operating wavelength, and
wherein each group of sub-wavelength antenna elements is spatially separated from each other group of sub-wavelength antenna elements by at least a distance exceeding that of half of an operating wavelength.
9. The method of claim 8 , wherein the at least two groups of sub-wavelength antenna elements comprises a first group of sub-wavelength antenna elements that is not co-planar with a second group of sub-wavelength antenna elements.
10. The method of claim 9 , further comprising optimizing a power transfer from the first group of sub-wavelength antenna elements to the second group of sub-wavelength antenna elements.
11. The method of claim 10 , wherein optimizing the power transfer comprises minimizing the power transferred to one lumped external port while maintaining the power transferred to another lumped external port at or above a threshold level.
12. The method of claim 10 , wherein optimizing the power transfer comprises maintaining the power transferred to another lumped external port below a threshold level.
13. The method of claim 12 , wherein maintaining below the threshold level is a maintaining below a predetermined threshold to avoid overexposing objects, equipment, or living things.
14. The method of claim 12 , wherein maintaining below the threshold is a specific limiting of power density within a dynamic exclusion zone.
15. The method of claim 1 , wherein the at least one lumped external port comprises a wireless power receiver associated with a vehicle.
16. The method of claim 1 , wherein at least some of the sub-wavelength antenna elements comprise resonating elements.
17. The method of claim 1 , wherein the at least one lumped external port comprises a virtual external port.
18. The method of claim 1 , wherein each of the sub-wavelength antenna elements has a spacing from its nearest neighbor that is substantially less than a free-space wavelength corresponding to the operating frequency.
19. The method of claim 1 , wherein the at least one lumped external port comprises a plurality of lumped external ports all located external to the wireless power transmitter, and wherein the target electromagnetic field amplitudes in the S-Matrix of each of the plurality of lumped external ports correspond to a target electromagnetic radiation pattern of the wireless power transmitter for at least the operating frequency.
20. The method of claim 1 , wherein the at least one lumped external port comprises a plurality of lumped external ports all located external to the wireless power transmitter, and
wherein identifying the target electromagnetic radiation pattern of the wireless power transmitter in terms of the target field amplitude in the S-Matrix for the plurality of lumped external ports comprises:
identifying the target electromagnetic radiation pattern of the wireless power transmitter in terms of a target field amplitude for at least two linear polarizations.
21. The method of claim 1 , wherein a physical location of the at least one lumped external port and the target electromagnetic field amplitude in the S-Matrix from the at least one lumped external port are selected to increase uniformity of a radiation profile of the wireless power transmitter in the near-field.
22. The method of claim 1 , wherein determining the optimized {z n } of impedance values for each of the lumped antenna ports comprises determining an optimized set of control values for the plurality of impedance control inputs that results in an field amplitude for the at least one lumped external port in the S-Matrix that approximates the target field amplitude for an operating frequency.
23. A method of manufacturing a variable wireless power transmitter, comprising:
arranging a plurality of sub-wavelength antenna elements configured to scatter received electromagnetic fields;
communicatively coupling a plurality of variable impedance elements in communication with the plurality of sub-wavelength antenna elements;
connecting a plurality of variable impedance control inputs to the plurality of variable impedance elements, such that the plurality of variable impedance control inputs allow for a selection of an impedance value for each of the lumped impedance elements;
communicatively coupling the variable impedance control inputs to a processor, such that the processor can control the selection of an impedance value for each of the lumped impedance elements via the variable impedance control inputs; and
a computer readable medium providing instructions accessible to the processor to cause the processor to perform operations for wireless transferring power, comprising
determining a scattering matrix (S-Matrix) of electromagnetic field amplitudes for each of a plurality of lumped ports, wherein the lumped ports include:
a plurality of lumped antenna ports with impedance values corresponding to the impedance values of each of the plurality of variable impedance elements; and
at least one lumped external port corresponding to a wireless power receiver located physically external to the wireless power transmitter,
wherein the S-Matrix is expressible in terms of an impedance matrix, Z-Matrix, with impedance values of each of the plurality of lumped ports;
identifying a target electromagnetic radiation pattern of the wireless power transmitter defined in terms of target electromagnetic field amplitudes in the S-Matrix for the at least one lumped external port;
determining an optimized port impedance vector, {z n } of impedance values for each of the lumped antenna ports that results in an S-Matrix element for the at least one lumped external port that approximates the target electromagnetic field amplitude for an operating frequency; and
adjusting at least one of the plurality of variable impedance control inputs to modify at least one of the impedance values of at least one of the plurality of variable impedance elements based on the determined optimized {z n } of the impedance values for the lumped antenna ports.
24. The method of claim 23 , further comprising forming a transmission line coupled to the plurality of sub-wavelength elements,
wherein the formed plurality of sub-wavelength antenna elements are configured to transmit electromagnetic fields received from the transmission line.
25. The method of claim 23 , wherein the plurality of sub-wavelength antenna elements is divided into at least two groups,
wherein sub-wavelength antenna elements within each group are separated from one another by no more than half of an operating wavelength, and
wherein each group of sub-wavelength antenna elements is spatially separated from each other group of sub-wavelength antenna elements by at least a distance exceeding that of half of an operating wavelength.
26. The method of claim 25 claim, wherein the at least two groups of subwavelength antenna elements comprises a first group of sub-wavelength antenna elements that is not co-planar with a second group of sub-wavelength antenna elements.
27. The method of claim 26 , further comprising optimizing a power transfer from the first group of sub-wavelength antenna elements to the second group of subwavelength antenna elements.
28. The method of claim 27 , wherein optimizing the power transfer comprises maintaining a heat generation associated with the power transfer below a threshold level.
29. The method of claim 23 , wherein the at least one lumped external port comprises a wireless power receiver associated with a medical implant.
30. The method of claim 23 , wherein the at least one lumped external port comprises a wireless power receiver associated with a medical device passing through a lumen of a patient.
31. The method of claim 23 , further comprising submerging the plurality of sub-wavelength elements in a fluid.
32. The method of claim 23 , wherein the at least one lumped external port comprises a plurality of lumped external ports all located external to the wireless power transmitter, and wherein the target electromagnetic field amplitudes in the S-Matrix of each of the plurality of lumped external ports correspond to a target electromagnetic radiation pattern of the wireless power transmitter for at least the operating frequency.
33. The method of claim 23 , wherein determining the optimized {z n } of impedance values for each of the lumped antenna ports comprises determining an optimized set of control values for the plurality of impedance control inputs that results in an field amplitude for the at least one lumped external port in the S-Matrix that approximates the target field amplitude for an operating frequency.
34. The method of claim 23 , wherein the impedance control input associated with at least one of the impedance elements comprises a direct current (DC) voltage input, wherein the impedance value of the at least one impedance element is based on the magnitude of the voltage supplied via the DC voltage input.
35. The method of claim 23 , wherein at least one of the impedance elements comprises at least one of a split ring resonator, a spiral resonator, an ELC resonator, a complementary split ring resonator, and a complementary ELC resonator.
36. The method of claim 23 , wherein at least one of the impedance elements comprises a volatile memory element.
37. The method of claim 23 , wherein at least one of the impedance elements comprises a non-volatile memory element.
38. The method of claim 23 , wherein at least one of the impedance elements is connected to and collocated with a tunable microelectronic circuit located at the intersection of a word line and a bit line, and connected to both the word line and the bit line.