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 over a carrier signal to an implantable device disposed within a body that causes varying transmission characteristics, the method comprising the steps of:
providing, from a forward link transmitter exterior of the body, a single power and data signal, the single power and data signal being encoded by amplitude modulation utilizing a minimized depth of modulation, the minimized depth of modulation configured for minimizing disruption in providing power to the implantable device; and
transmitting the single power and data signal for powering an operation of the implantable device,
wherein a carrier frequency of the carrier signal is based on a power budget of the implantable device.
2. The method of claim 1 , further comprising:
receiving, by a transceiver of the implantable device, the single power and data signal;
processing within the implantable device the single power and data signal, the processing including:
decoding a forward-link data portion of the single power and data signal; and
collecting power required for the operation of the implantable device from the RF carrier of the single power and data signal.
3. The method of claim 1 , wherein the forward link-data portion corresponds to a control operation of the implantable device, the method further comprising storing the control operation for execution by a processor of the implantable device.
4. The method of claim 1 , wherein the forward-link data portion is decoded asynchronous to the carrier signal.
5. The method of claim 1 , wherein decoding the forward link-data portion comprises utilizing an envelope detector and pulse decoder for:
tracking an average of the envelope of the carrier signal utilizing a dynamic reference; and
converting an envelope transition to a digital signal by comparison of an average of the dynamic reference and amplifying a result of the comparison.
6. The method of claim 5 , wherein the envelope transition includes at least one negative component and at least one positive component of equal length, and wherein encoding forward-link data on the single power and data signal, comprises encoding digital data on the at least one positive and negative envelope transitions.
7. The method of claim 2 , wherein collecting power comprises: passing the single power and data signal to a power receiver disposed within the implantable device, the power receiver including a rectifier and/or a voltage regulator configured for providing a stable power supply.
8. The method of claim 1 , further comprising recovering, at the forward link data transmitter exterior of the body, an encoded reverse data stream provided by a reverse data link of the implantable device.
9. The method of claim 1 , wherein recovering the encoded reverse data stream occurs when no forward link data is being transmitted.
10. The method of claim 1 , further comprising decoding the encoded reverse data stream at the forward data link transmitter exterior of the body.
11. The method of claim 9 , wherein the encoded reverse data stream includes a device ID corresponding to the implantable device, the method further comprising, determining, at the forward link data transmitter exterior of the body, the device ID corresponding to the implantable device.
12. The method of claim 1 , further comprising switching a variable impedance in a signal path of the carrier signal thereby increasing or decreasing the minimized depth of modulation.
13. The method of claim 11 , wherein switching the variable impedance for increasing or decreasing the minimized depth of modulation includes switching a bi-polar junction transistor (BJT) transistor, the BJT transistor configured to simultaneously act as a switch and the variable impedance in the signal path.
14. The method of claim 11 , wherein switching the variable impedance comprises, switching, in response to determining forward link data is being transmitted.
15. The method of claim 1 , wherein the minimized depth of modulation is in the range of a 15-20% reduction of an envelope of the carrier signal.
16. The method of claim 1 , wherein transmitting the single power and data signal includes transmitting the single power and data single a distance in the range of carrier wavelength/100 to carrier wavelength*100.
17. The method of claim 1 , wherein the carrier signal comprises a radio frequency (RF) carrier signal.
18. A method for wireless transmission of data and power over a carrier signal to an implantable device disposed within a body that causes varying transmission characteristics, the method comprising the steps of:
providing, from a forward link transmitter exterior of the body, a single power and data signal, the single power and data signal being encoded by amplitude modulation utilizing a minimized depth of modulation, the minimized depth of modulation configured for minimizing disruption in providing power to the implantable device; and
transmitting the single power and data signal for powering an operation of the implantable device,
wherein decoding the forward link-data portion comprises utilizing an envelope detector and pulse decoder for:
tracking an average of the envelope of the carrier signal utilizing a dynamic reference; and
converting an envelope transition to a digital signal by comparison of an average of the dynamic reference and amplifying a result of the comparison.
19. A method for wireless transmission of data and power over a carrier signal to an implantable device disposed within a body that causes varying transmission characteristics, the method comprising the steps of:
providing, from a forward link transmitter exterior of the body, a single power and data signal, the single power and data signal being encoded by amplitude modulation utilizing a minimized depth of modulation, the minimized depth of modulation configured for minimizing disruption in providing power to the implantable device; and
transmitting the single power and data signal for powering an operation of the implantable device; and
switching a variable impedance in a signal path of the carrier signal thereby increasing or decreasing the minimized depth of modulation.
20. A method for wireless transmission of data and power over a carrier signal to an implantable device disposed within a body that causes varying transmission characteristics, the method comprising the steps of:
providing, from a forward link transmitter exterior of the body, a single power and data signal, the single power and data signal being encoded by amplitude modulation utilizing a minimized depth of modulation, the minimized depth of modulation configured for minimizing disruption in providing power to the implantable device; and
transmitting the single power and data signal for powering an operation of the implantable device,
wherein the minimized depth of modulation is in the range of a 15-20% reduction of an envelope of the carrier signal.