K. Vanschuylenbergh et R. Puers, SELF-TUNING INDUCTIVE POWERING FOR IMPLANTABLE TELEMETRIC MONITORING SYSTEMS, Sensors and actuators. A, Physical, 52(1-3), 1996, pp. 1-7
Inductive powering of implantable monitoring devices is a widely accep
ted solution for replacing implanted batteries. However, this method d
emands technically skilled operators to tune constantly the power link
parameters. This becomes particularly important when the external sys
tem must also be portable. However, acceptable lifetimes for the exter
nal batteries can be obtained by a precise optimization of the power e
fficiency of the inductive link. In this paper, a technique is present
ed to render such a portable system fully compatible with a hospital e
nvironment. It is implemented in an independent, automatic and user-fr
iendly powering set-up to avoid the need for engineers or additional e
lectronic equipment for optimization of the link parameters. Multiple
automatic tuning loops are incorporated to handle component tolerances
and coil movements, and to optimize the power efficiency on a continu
ous basis. A visual and an acoustic indicator give the operator an add
itional feedback on the quality of the established link. As an example
, the problem of mechanical strain sensing in femoral nailplates is gi
ven. It is representative for the envisaged range of applications. The
se are characterized by a low coil coupling (k less than 1%) and power
transfers of the order of 20 mW.