Wireless midfield systems and methods
Implantable devices and/or sensors can be wirelessly powered by controlling and propagating electromagnetic waves in a patient's tissue. Such implantable devices/sensors can be implanted at target locations in a patient, to stimulate areas such as the heart, brain, spinal cord, or muscle tissue, and/or to sense biological, physiological, chemical attributes of the blood, tissue, and other patient parameters. The propagating electromagnetic waves can be generated with sub-wavelength structures configured to manipulate evanescent fields outside of tissue to generate the propagating waves inside the tissue. Methods of use are also described.
1. A wireless power transmitter configured to provide tunneling wireless power signals toward one or more devices implanted in tissue when a first surface of the transmitter is provided adjacent to but spaced apart from a tissue interface, the transmitter comprising:
one or more electrically-excitable structures provided peripherally relative to a center of a substrate;
one or more excitation ports coupled respectively to the one or more electrically-excitable structures; and
a ground plane provided substantially parallel to the one or more electrically-excitable structures;
wherein in response to the one or more excitation ports receiving drive signals from a controller, a surface of the transmitter is configured to conduct current in an oscillatory current pattern that converges toward the center of the substrate to thereby provide a corresponding magnetic field that is substantially parallel with the tissue surface.
2. The transmitter of claim 1 , wherein in response to the one or more excitation ports receiving the drive signals from the controller, the surface of the transmitter is configured to conduct current in the oscillatory current pattern that converges toward the center of the substrate to generate a surface wave at the tissue surface and thereby excite propagating field modes inside the tissue.
3. The transmitter of claim 1 , wherein in response to the one or more excitation ports receiving the drive signals from the controller, the surface of the transmitter is configured to conduct current in the oscillatory current pattern that converges toward the center of the substrate to manipulate evanescent waves at or near the tissue surface and thereby excite propagating field modes inside the tissue.
4. The transmitter of claim 1 , further comprising a spacer configured to facilitate placement of the transmitter adjacent to and spaced apart from the tissue surface.
5. The transmitter of claim 4 , wherein the spacer is configured to maintain a standoff distance of about 1 centimeter between the tissue surface and the electrically-excitable structures.
6. The transmitter of claim 1 , wherein the one or more electrically-excitable structures comprise respective sub-wavelength structures that each include a portion of a conductive substrate and one or more slots or voids therein.
7. The transmitter of claim 1 , further comprising the controller configured to generate the drive signals.
8. The transmitter of claim 7 , wherein the controller is configured to concurrently provide at least two drive signals to respective ones of first and second ones of the excitation ports, wherein the at least two drive signals have different phase and/or amplitude characteristics.
9. A wireless power transmitter configured to provide wireless power to an implanted device when the transmitter is provided adjacent to but spaced apart from a tissue interface, the transmitter comprising:
one or more electrically-excitable structures provided peripherally relative to a center axis of a conductive substrate;
one or more excitation ports coupled respectively to the one or more electrically-excitable structures;
a ground plane provided substantially parallel to the one or more electrically-excitable structures; and
a signal generator circuit configured to generate and provide respective drive signals to the one or more excitation ports;
wherein when the one or more excitation ports receive drive signals from the signal generator circuit, the conductive substrate is configured to conduct current signals in oscillatory current patterns that converge substantially toward the center axis of the substrate and thereby provide a corresponding magnetic field that is substantially parallel with the tissue surface.
10. The transmitter of claim 9 , wherein when the one or more excitation ports receive the drive signals from the signal generator circuit, the transmitter generates a surface wave at the tissue surface that excites propagating field modes inside the tissue.
11. The transmitter of claim 9 , wherein when the one or more excitation ports receive the drive signals from the signal generator circuit, the transmitter is configured to manipulate evanescent waves at or near the tissue surface and thereby excite propagating field modes inside the tissue.
12. The transmitter of claim 9 , further comprising a spacer configured to facilitate placement of the transmitter adjacent to and spaced apart from the tissue surface.
13. The transmitter of claim 9 , wherein the one or more electrically-excitable structures comprise respective sub-wavelength structures.
14. The transmitter of claim 9 , wherein the signal generator circuit is configured to concurrently provide the drive signals to respective ones of the excitation ports, wherein the drive signals have different phase and/or amplitude characteristics.
15. A method for wirelessly transmitting power and/or data to an implanted device within tissue, the method comprising:
changing characteristics of an evanescent field adjacent to a tissue interface using a transmitter device that includes a planar excitation surface, wherein the planar excitation surface carries an oscillating current signal about a substantially circular path that is parallel with a tissue surface at the tissue interface; and
in response to the evanescent field as manipulated using the transmitter device, causing propagating waves inside of the tissue to carry power and/or data signals from the transmitter device to the implanted device.
16. The method of claim 15 , further comprising providing respective drive signals to the planar excitation surface in the transmitter device, wherein the respective drive signals have different phase and/or amplitude characteristics.
17. The method of claim 16 , further comprising generating the drive signals using a signal generator circuit that comprises a portion of the transmitter device.
18. The method of claim 16 , wherein the providing the respective drive signals to the planar excitation surface includes providing the drive signals to respective electrically-excitable structures provided peripherally relative to a center of the planar excitation surface.
19. The method of claim 15 , further comprising positioning the transmitter device a specified distance apart from the tissue surface using a spacer.
20. The method of claim 15 , wherein the changing the characteristics of the evanescent field includes in response to changing a characteristic of the oscillating current signal carried by the excitation surface.