Electromagnetic analysis, characterization and discussion of inductive transmission parameters for titanium based housing materials in active medical implantable devicess

Abstract

The growing demand for activemedical implantable devices requires data and or power links between the implant and the outsideworld. Every implant has to be encapsulated fromthe body by a specific housing and one of themost commonmaterials used is titaniumor titaniumalloy. Titaniumthas the necessary properties in terms of mechanical and chemical stability and biocompatibility. However, its electrical conductivity presents a challenge for the electromagnetic transmission of data and power. The proposed paper presents a fast and practicalmethod to determine the necessary transmission parameters for titanium encapsulated implants. Therefore, the basic transformer-transmission-model is used with measured or calculated key values for the inductances. Those are then expandedwith correction factors to determine the behaviorwith the encapsulation. The correction factors are extracted fromfinite elementmethod simulations. These also enable the analysis of the magnetic field distribution inside of the housing. The simulated transmission properties are very close to the measured values. Additionally, based on lumped elements and magnetic field distribution, the influential parameters are discussed in the paper. The parameter discussion describes how to enhance the transmitted power, data-rate or distance, or to reduce the size of the necessary coils. Finally, an example application demonstrates the usage of themethods.