Inductive Powering of Implanted Electronics

Description of Research


Concept of Operation

Presentation of Problem


  • Need For long-term, continuously operating implants
  • Distributed implants
  • Battery limitations
  • High-bandwith communication and control

Candidate application: Cardiac Mapping


  • Description of application
  • Application requirements

Hypothesis


  • “Magnetic Vector Steering (MVS) and Half-Cycle Amplitude Modulation (HCAM) are two techniques that enhance the state of the art in (Biotelemetry) implant technology, by providing an effective means of powering, controlling, and communicating with multiple, distributed implants. “

Research Goal


  • “To use theoretical, simulation, and experimental means to prove feasibility and efficacy of MVS and HCAM with respect.

Impact of Research


  • Means of providing “strategic” power delivery to distributed, arbitrarily positioned implants
  • Means of Providing bidirectional, high-bandwith communications with implants
  • Evaluated instance of a High-bandwith system using MVS and HCAM

State of the Art in Electronic Implants

Candidate implants

Three primary areas of interest:


  • System architectures
  • Inductive power transfer
  • Communication techniques

Relevant systems

  • Microstimulator technology (FNS)
  • Inductive power transfer (IPT)
  • In-link communication using IPT
  • Out-link communication using IPT
  • Distributed implant technology

Architecture


  • Focused vs. scattered power delivery
    Magnetic Vector Steering (MVS)
  • Transmission format (in-link and out-link)
  • Throughout
  • Noise and interference issues
  • Sensitivity
  • Complexity
  • Synergy
MVS

 

Anticipated advantages


  • Low hardware overhead
  • Fairly uniform magnetic field intensity
  • Conserved energy
  • Low sensitivity to misalignment
  • Distributed energy absorption by tissue

Possible disadvantages


  • Time-varying power delivery
  • Delay associated with redirection of magnetic fields
  • link detuning due to repositioning/motion of harness assembly
HCAM

HCAM Anticipated Advantages:


  • Very fast data rate
  • low harmonic content

Possible Disadvantages

  • Additional harmonic generation due to non-ideal switching
MVS and HCAM (programming and control)
MVS and HCAM (free-run mode)

MVS and HCAM

Anticipated Advantages :

  • ¬†Minimal interference between communications systems
  • communications channel optimize for given implant during power transfer
  • HCAM can be added easily to existing MVS Hardware
  • Presence of power carrier can be used for subsystems

Research Activities

Goal:

  • Prove feasability and efficacy of proposed techniques(MVS and HCAM)

Research Approach


  • Use theorhetical investigations, simulations, and experiments to achieve goal
  • Break-down proposed system into smaller units that can be analyzed effectively
  • Bring together sub-units into larger units
  • Optimize larger units
  • Test overall system prototype

Area of focus


  • Coil analysis and design
    Design and operating considerations
  • Power electronics system and design
  • Tissue loading analysis
  • Implant loading analysis / implant design
  • Communications systems analysis and design
  • System analysis and design
  • System construction
  • System evaluation

Experiments

Consideration of non-ideal effects
Experimental setup (IPT)
Experimental setup (HCAM)
Experimental setup (mock animal)

Expected Outcomes


  • ¬†IPT can be accomplished under a variety of non-ideal conditions
  • Link loss to be significantly but not detrimentally affected by animal motion, harness deformation, and the presence of metallic objects
  • Half power angle at approximately 45 degrees
  • HCAM not affected by motion but possibly affected to a small degree by position
  • Some degree of telemeter directionality unless there are significant reflections in the room

Accomplishments


Background investigations Simulations:


  • coupling between circular loops
  • modeling effects of tissue loading

Perliminary experiments:


  • Power coupling between circular loops
  • Experimentally determined effects of tissue loading

Harmonic generation analysis due to HCAM


Studies

Experimental hardware:


  • Energizing hardware with computer controlled amplitude and phase control
  • Computer interface card
  • 3-D field probe

Published in .