Method and apparatus for efficient communication with implantable devices
Described herein are methods of making and using and apparatus for wirelessly communicating data and providing power, particularly from a location exterior to a body and to an implantable device disposed within a body with tissue. The described embodiments provide apparatus and methods for efficiently transfer data and power between an external transceiver and an (implanted) biomedical device. The method is to modulate power carrier, which wirelessly powers the device, using an asynchronous modulation scheme, such as amplitude shift keying (ASK) modulation, with minimal modulation depth in order to not disrupt the power flow. The digital data is encoded in the pulse width, eliminating the need for synchronization to the power carrier signal and further minimizing the power consumption necessary for data transfer. Additionally, a reverse backscatter method for obtaining data from the implant is described that has flexible, low power operation.
1. A method for wireless transmission of data and power to an implantable device disposed within a body that causes varying transmission characteristics, the method comprising the step of:
providing, from a forward link transmitter exterior of the body, a single power and data signal, the single power and data signal including a RF carrier and data encoded on the RF carrier;
directing the single power and data signal toward the implantable device disposed within the body;
receiving, at the implantable device or devices, the single power and data signal; and
processing within the implantable device or devices the received single power and data signal, the processing including:
collecting power required for operation of the implantable device from the RF carrier of the single power and data signal; and
decoding the data encoded on the RF carrier, wherein the decoding occurs without synchronizing to the RF carrier, and wherein during the step of directing, a distance between a forward link transmitter and the implantable device is in the range of carrier wavelength/100 to carrier wavelength*100.
2. The method according to claim 1 wherein:
the step of collecting power required for operation uses a rectifier; and
the step of decoding uses a decoder to asynchronously decode the data encoded on the RF carrier.
3. The method according to claim 1 wherein the implantable devices are individually addressable.
4. The method according to claim 2 wherein the step of decoding uses a detected envelope of the RF carrier to asynchronously decode the data encoded on the RF carrier.
5. The method according to claim 4 wherein the data encoded on the RF carrier is encoded during the step of providing using amplitude shift keying modulation, with the data being encoded in a pulse width, amplitude, and/or timing.
6. The method according to claim 5 wherein the data encoded on the RF carrier is also encoded with minimal modulation depth.
7. The method according to claim 5 wherein the data encoded on the RF carrier is encoded as either a digital “0” or a digital “1”.
8. The method according to claim 5 wherein the amplitude shift keying modulation includes multi-level encoding.
9. The method according to claim 2 wherein the data encoded on the RF carrier is encoded as a symbol.
10. The method according to claim 1 wherein the data encoded on the RF carrier provided in the step of providing includes clock data and other circuit data, wherein the implantable device further includes a controller that received the other circuit data and a PLL coupled to the controller, and further including the steps of:
training the PLL using the clock data; and
using the other circuit data in the controller.
11. The method according to claim 1 wherein the step of decoding uses a dynamically generated reference level.
12. The method according to claim 10 wherein adjustable reference level is adjusted continuously or periodically.
13. The method according to claim 2 wherein the data encoded on the RF carrier is encoded during the step of providing using frequency modulation.
14. The method according to claim 13 wherein the decoding of the encoded data uses selective filtering of the transmitted frequencies.
15. The method according to claim 5 wherein the step of providing changes the pulse width, amplitude, and/or timing to accommodate a configuration of the decoder.
16. The method according to claim 5 wherein the step of providing changes a data rate to accommodate a configuration of the decoder.
17. The method according to claim 5 wherein the step of providing reduces a data rate in response to the step of collecting obtaining less power over a period of time.
18. The method according to claim 5 wherein the step of providing changes a data rate to accommodate the intended purpose of the device or devices.
19. The method according to claim 1 , further including the step of:
providing, from a reverse link transmitter within the implantable device, a single reverse link data signal,
encoding the single reverse link data signal by adjusting a load on an antenna that receives the RF carrier, thereby causing a reflected RF carrier that has the reverse link data encoded thereon; and
decoding the reflected RF carrier at a location exterior of the body to asynchronously receive and reconstruct the single reverse link data signal.
20. The method according to claim 19 wherein the device or devices configure the reflected signal pulse width, amplitude, and/or timing to accommodate its purpose.
21. The method according to claim 19 wherein the device or devices configure a data rate to accommodate their intended purpose.