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. An implantable device configured to wirelessly receive power and/or data via a mid-field signal when the device is implanted inside a patient body, the implantable device comprising:
an antenna configured to receive a wireless power signal transmitted by a first external device;
a stimulator configured to apply an electrostimulation therapy to the patient tissue;
an energy storage circuit configured to store power from the wireless power signal received using the antenna; and
a control circuit configured to control the electrostimulation therapy and configured to control an electrostimulation pulse characteristic of the electrostimulation therapy based on a characteristic of the wireless power signal received using the antenna, wherein the control circuit and the electrostimulation therapy use the stored power from the energy storage circuit.
2. The implantable device of claim 1 , wherein the electrostimulation pulse characteristic comprises frequency and wherein the characteristic of the wireless power signal comprises a power level.
3. The implantable device of claim 1 , wherein the antenna comprises a wire coil.
4. The implantable device of claim 1 , further comprising:
a rectifier circuit coupled to the antenna; and
a power converter coupled to the rectifier circuit, the stimulator, and the energy storage circuit.
5. The implantable device of claim 4 , wherein the power converter comprises an AC-DC power converter divided into a first lower-voltage power domain and a second higher-voltage power domain.
6. The implantable device of claim 1 , wherein the energy storage circuit comprises at least one of a battery, a fixed-capacitance capacitor, and a variable-capacitance capacitor.
7. The implantable device of claim 1 , wherein the control circuit is configured to control the electrostimulation therapy synchronously with receipt of the wireless power signal.
8. The implantable device of claim 1 , wherein the control circuit is configured to control the electrostimulation therapy asynchronously with receipt of the wireless power signal.
9. The implantable device of claim 1 , wherein the control circuit is configured to measure an amount of power received from the first external device and communicate information about the amount to the first external device.
10. The implantable device of claim 1 , further comprising at least one of a physiologic sensor configured to sense a physiologic signal from the patient tissue;
a memory circuit, coupled to the at least one physiologic sensor or the stimulator, configured to store information about a sensed physiologic signal from the physiologic sensor or store information about an electrostimulation therapy provided by the stimulator; and
a transmitter circuit configured to transmit the stored information to the same first external device or to a different external device.
11. The implantable device of claim 10 , wherein the memory circuit is configured to store information about an effect of a therapy provided by the implanted device, and wherein the transmitter circuit is configured to transmit the stored information about the effect of the therapy.
12. A method for providing therapy to an internal body tissue site using an implantable mid-field device, the method comprising:
receiving a wireless power signal at the implantable mid-field device;
storing at least a portion of the received wireless power signal using an energy storage circuit in the implantable mid-field device; and
controlling an electrostimulation therapy provided by the implantable mid-field device using a control circuit in the implantable mid-field device, wherein the electrostimulation therapy uses energy from the energy storage circuit, and wherein controlling the electrostimulation therapy includes using information about a characteristic of the wireless power signal received at the implantable mid-field device.
13. The method of claim 12 , wherein controlling the electrostimulation therapy includes changing one or more of an amplitude, duration, frequency, or shape of an electrostimulation pulse that comprises the electrostimulation therapy.
14. The method of claim 12 , wherein controlling the electrostimulation therapy includes using information about a magnitude of the wireless power signal received at the implantable mid-field device.
15. The method of claim 12 , wherein receiving the wireless power signal at the implantable mid-field device comprises receiving a portion of a non-stationary signal inside the patient body.
16. The method of claim 12 , further comprising:
rectifying, using a rectifier circuit in the implantable mid-field device, at least a portion of the wireless power signal as-received to provide a rectified power signal;
converting the rectified power signal to at least two different voltage signals and providing the different voltage signals to circuitry in respective different power domains in the implantable mid-field device.
17. The method of claim 12 , wherein controlling the electrostimulation therapy includes providing the electrostimulation therapy synchronously or asynchronously with receipt of the wireless power signal.
18. A system of implantable devices configured to wirelessly receive power via a mid-field signal from a common external source device when the implantable devices are implanted inside a patient body, wherein each of the implantable devices is individually addressable by the common external source device, the system comprising:
a first implantable device including:
an antenna configured to receive a wireless power signal transmitted by an external device, wherein the wireless power signal comprises a portion of a non-stationary signal inside the patient body;
a stimulator configured to apply an electrostimulation therapy to the patient tissue;
an energy storage circuit configured to store power from the wireless power signal received using the antenna; and
a control circuit configured to control the electrostimulation therapy based on a characteristic of the power signal received using the antenna, wherein the control circuit and the electrostimulation therapy use the stored power from the energy storage circuit.
19. The system of claim 18 , wherein the control circuit is configured to control an amplitude, duration, frequency, or shape of an electrostimulation signal that comprises the electrostimulation therapy based on a magnitude of the wireless power signal received using the antenna.