After nearly a decade of development, human-implantable sensors for detection of muscle activity have recently been demonstrated in the literature. These sensors are intended to provide better and more numerous control sources for a new generation of prosthetic devices that operate in a more natural fashion by using multiple joints and many degrees of freedom. The implantable sensors are powered and communicate wirelessly through the skin using coupled inductor coils.

The focus of the present work has been the development of a new approach to modeling the inductively coupled link by using the finite element method (FEM) to simulate a three-dimensional representation of the coils and surrounding magnetic field. This approach is attractive because it is able to encompass many physical geometric and magnetic parameters which have been a challenge to evaluate in the past.

The validity of the simulation is tested by comparison to analytically-developed formulas for self-inductance, ac resistance and mutual inductance of the coils. Determination of these parameters is necessary for calculation of the coupling coefficient between the coils, and to fully define the lumped circuit model of the link.

Use of FEM allows for more accurate simulation of configurations and materials not possible with the use of analytical formulas. For example, the complex permeability of a ferrite core is easily incorporated into the FEM model allowing for its effects to be included in the system design process. Furthermore, the three-dimensional nature of the simulation enables the calculation of transferred power for arbitrary orientations and positions of the secondary implant coil with respect to the primary coil.

Consequently, the proposed FEM approach can be a useful design tool for development of the next generation of implantable bio-sensors.