Method and Apparatus for Efficient Communication with Implantable Devices

Abstract

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.

What is claimed is: 
     
         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 power and data signal, the power and data signal including a RF carrier signal and data encoded on the RF carrier signal;   directing the power and data signal toward the implantable device disposed within the body;   receiving, at the implantable device or devices, the power and data signal; and   processing within the implantable device or devices the received power and data signal, the processing including:
 collecting power required for operation of the implantable device from the RF carrier signal of the power and data signal; and 
 decoding the data encoded on the RF carrier signal, wherein the decoding occurs without synchronizing to the RF carrier signal. 
   
     
     
         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 signal. 
 
     
     
         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 signal to asynchronously decode the data encoded on the RF carrier signal. 
     
     
         5 . The method according to  claim 4  wherein the data encoded on the RF carrier signal 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 signal is also encoded with minimal modulation depth. 
     
     
         7 . The method according to  claim 5  wherein the data encoded on the RF carrier signal 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 signal is encoded as a symbol. 
     
     
         10 . The method according to  claim 1  wherein the data 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 signal 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 reverse link data signal,   encoding the reverse link data signal by adjusting a load on an antenna that receives the RF carrier signal, thereby causing a reflected RF carrier signal that as the reverse link data encoded thereon; and   decoding the reflected RF carrier signal at a location exterior of the body to asynchronously receive and reconstruct the 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. 
     
     
         22 . A method for amplitude modulation of a high frequency carrier signal comprising the step of:
 Switching a variable impedance into a signal path of the high frequency carrier signal to either divert energy from a transmitter and/or reflect energy back to the transmitter, allowing modulation depths of the frequency carrier signal from 0-100%.   
     
     
         23 . The method according to  claim 22  wherein the step of switching uses a transistor to act as a switch and cause an impedance to vary, with the impedance being adjusted by a voltage applied to one of the dependent terminals of the transistor. 
     
     
         24 . The method according to  claim 22 , wherein the step of switching occurs in the transmitter and the energy is diverted from the transmitter. 
     
     
         25 . The method according to  claim 22 , wherein the step of switching occurs in a receiver and the energy is reflected back to the transmitter. 
     
     
         26 . The method according to  claim 1  wherein, during the step of directing, the distance between the forward link transmitter and the body being in the range of carrier wavelength/100 to carrier wavelength*100.