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. An apparatus for wireless transmission of data and power to an implantable device disposed within a body that causes varying transmission characteristics, the apparatus comprising:
a forward link transmitter located exterior of the body the forward link transmitter configured to perform a method comprising the steps of:
providing a single power and data signal, the single power and data signal including a RF carrier and data encoded on the RF carrier; and
directing the single power and data signal toward the implantable device disposed within the body; and
one or more implantable devices configured to perform a method comprising the steps of:
receiving the single power and data signal; and
processing 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.
2. The apparatus according to claim 1 , wherein the implantable device includes:
a rectifier that is configured to collect the power required for operation; and
a decoder to asynchronously decode the data encoded on the RF carrier.
3. The apparatus according to claim 1 , wherein the one or more implantable devices are individually addressable.
4. The apparatus according to claim 2 , wherein the decoder is configured to use a detected envelope of the RF carrier to asynchronously decode the data encoded on the RF carrier.
5. The apparatus according to claim 4 , wherein the forward link transmitter includes a modulator that is configured to encode the data using amplitude shift keying modulation, with the data being encoded in a pulse width, amplitude, and/or timing.
6. The apparatus according to claim 5 , wherein the modulator is configured to encode the data on the RF carrier with minimal modulation depth.
7. The apparatus according to claim 5 , wherein the modulator is configured to encode the data on the RF carrier as either a digital “0” or a digital “1”.
8. The apparatus according to claim 5 , wherein the amplitude shift keying modulation includes multi-level encoding.
9. The apparatus according to claim 2 , the data encoded on the RF carrier is encoded as a symbol.
10. The apparatus according to claim 1 , wherein the data encoded on the RF carrier includes clock data and other circuit data, wherein the one or more implantable devices further includes a controller that is configured to receive the other circuit data and a PLL coupled to the controller, and wherein the one or more implantable devices are further configured to perform the steps of:
training the PLL using the clock data; and
using the other circuit data in the controller.
11. The apparatus according to claim 1 , wherein the one or more implantable devices is configured to use a dynamically generated reference level for decoding the data.
12. The apparatus according to claim 10 , wherein the reference level is adjusted continuously or periodically.
13. The apparatus according to claim 2 , wherein the data encoded on the RF carrier is encoded using frequency modulation.
14. The apparatus according to claim 13 , wherein the one or more implantable devices is configured to decode the data encoded using selective filtering of transmitted frequencies of the RF carrier.
15. The apparatus according to claim 5 , wherein the forward link transmitter is configured to change the pulse width, amplitude, and/or timing to accommodate a configuration of the decoder.
16. The apparatus according to claim 5 , wherein the forward link transmitter is configured to change a data rate to accommodate a configuration of the decoder.
17. The apparatus according to claim 5 , wherein the forward link transmitter is configured to reduce a data rate in response to the one or more implantable devices obtaining less power over a period of time.
18. The apparatus according to claim 5 , wherein the forward link transmitter is configured to change a data rate to accommodate the intended purpose of the one or more implantable devices.
19. The apparatus according to claim 1 , wherein:
the one or more implantable devices includes a reverse link transmitter that is configured to perform the steps of:
providing a single reverse link data signal, and
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 reverse link data encoded thereon, and causing a reader at a location exterior of the body to decode the reflected RF carrier to asynchronously receive and reconstruct the single reverse link data signal.
20. The apparatus according to claim 19 , wherein the one or more implantable devices configure a pulse width, amplitude, and/or timing of the reflected RF carrier to accommodate its purpose.
21. The apparatus according to claim 19 , wherein the one or more implantable devices configure a data rate to accommodate their intended purpose.
22. The apparatus according to claim 1 , 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.