Implantable medical device with backscatter signal based communication
View Patent ↗An implantable medical device is disclosed that includes a charging coil configured to inductively couple to a first external coil to receive a charging signal to charge a charge storage element of the implantable medical device. The implantable medical device also includes a circuit coupled to the charging coil. The circuit includes a circuit component that, in response to the charging signal, generates a backscatter signal. The implantable medical device also includes a communication coil orthogonal to the charging coil and coupled to the circuit component. The communication coil is configured to inductively couple to a second external coil to communicate the backscatter signal to the second external coil.
1. An implantable medical device comprising:
a charging coil configured to inductively couple to a first external coil to receive a charging signal to charge a charge storage element;
a circuit coupled to the charging coil, the circuit including a circuit component that, in response to the charging signal being applied to the circuit, generates a backscatter signal having a higher frequency than the charging signal; and
a communication coil orthogonal to the charging coil and coupled to the circuit component, the communication coil configured to inductively couple to a second external coil to communicate the backscatter signal to the second external coil.
2. The implantable medical device of claim 1 , wherein the circuit component includes a non-linear circuit element.
3. The implantable medical device of claim 1 , wherein the circuit includes a rectifier and wherein the circuit component includes a diode of the rectifier.
4. The implantable medical device of claim 1 , further comprising a therapy delivery unit configured to be coupled to the charge storage element, the therapy delivery unit configured to be implanted into a patient and to deliver therapy to the patient.
5. The implantable medical device of claim 1 , wherein the higher frequency of the backscatter signal is less than five times a frequency of the charging signal.
6. The implantable medical device of claim 1 , wherein the higher frequency of the backscatter signal is approximately five times a frequency of the charging signal.
7. The implantable medical device of claim 1 , wherein the charging coil is formed from a first conductor wound about a core, wherein the communication coil is formed from a second conductor wound about the core, and wherein the second conductor is more lossy than the first conductor.
8. The implantable medical device of claim 1 , wherein the charging coil, the communication coil, and the circuit are included in a device that is configured to be implanted into a patient.
9. The implantable medical device of claim 1 , wherein the backscatter signal is indicative of a charging voltage applied to the charge storage element, the charging voltage responsive to the charging signal.
10. A method comprising:
receiving a charging signal at a charging coil of an implantable medical device via inductive coupling of the charging coil to a first external coil of a charging device;
rectifying the charging signal and applying the rectified charging signal to a charge storage element of the implantable medical device;
applying a backscatter signal, having a higher frequency than the charging signal, to a communication coil of the implantable medical device, wherein the backscatter signal is generated responsive to the charging signal being applied to a component of the implantable medical device and wherein the communication coil is orthogonal to the charging coil; and
sending the backscatter signal to an external device by inductively coupling the communication coil to a second external coil of an external device to communicate the backscatter signal to the second external coil.
11. The method of claim 10 , wherein the second external coil is orthogonal to the first external coil and the charging coil, and wherein the communication coil is orthogonal to the first external coil.
12. The method of claim 11 , wherein the external device is included in the charging device, and wherein the charge storage element comprises a rechargeable battery.
13. The method of claim 10 , wherein the backscatter signal is associated with a harmonic frequency of the charging signal.
14. A charging device comprising:
a first charging coil configured to couple to a second charging coil of an implantable medical device, wherein the first charging coil is adapted to communicate a charging signal to the second charging coil to charge a charge storage element of the implantable medical device; and
a sensing coil that is orthogonal to the first charging coil, the sensing coil configured to detect a backscatter signal, having a higher frequency than the charging signal, from a communication coil of the implantable medical device, the backscatter signal generated by the implantable medical device responsive to the charging signal.
15. The charging device of claim 14 , wherein the backscatter signal is generated by a component of the implantable medical device responsive to the charging signal being applied to the component of the implantable medical device.
16. The charging device of claim 14 , further comprising a control unit configured to perform a frequency sweep of the charging signal.
17. The charging device of claim 14 , further comprising a control unit configured to cease application of the charging signal in response to processing of the backscatter signal.
18. The device of claim 14 , wherein the sensing coil comprises a first inductor and a second inductor, the first inductor corresponding to a first portion of the sensing coil and a second inductor corresponding to a second portion of the sensing coil, and wherein the first inductor is orientated substantially orthogonal to the second inductor and the first charging coil.
19. A method comprising:
applying a charging signal to a first charging coil of a charging device;
communicating the charging signal to a second charging coil of an implantable medical device by inductively coupling the second charging coil and the first charging coil, wherein the implantable medical device includes a charge storage element that is charged using the charging signal; and
detecting, at a sensing coil, a backscatter signal, having a higher frequency than the charging signal, from a communication coil of the implantable medical device, wherein the sensing coil is orthogonal to the first charging coil, the backscatter signal generated by the implantable medical device responsive to the charging signal.
20. The method of claim 19 , further comprising estimating a charging efficiency of the charging signal based on the backscatter signal.
21. The method of claim 20 , further comprising, after estimating the charging efficiency, adjusting a frequency of the charging signal.
22. The method of claim 19 , further comprising performing a frequency sweep of the charging signal to identify, based on the backscatter signal, a particular frequency associated with an improved charging efficiency relative to other frequencies of the charging signal.
23. The method of claim 19 , further comprising ceasing application of the charging signal in response to processing of the backscatter signal.