Design and application of broadband ceramic feedthrough capacitor EMI filters to cardiac pacemakers and implantable defibrillators
This paper describes ceramic feedthrough capacitor electromagnetic interference (EMI) broadband filter design and installation techniques that generally make cardiac pacemakers and implantable cardioverter defibrillators (ICDs) immune to EMI from handheld wireless communication devices (including cellular phones) and other RF emitters. A typical cardiac pacemaker with four platinum lead wires which egress through a titanium housing (can) via a gold brazed alumina hermetic terminal is studied. The titanium can is seam welded to act both as an electromagnetic shield and a hermetic barrier to protect the internal components from body fluids. These lead wires, which normally carry the pacing pulses and sense cardiac activity, can also act as an antenna and conduct undesirable RF carrier signals (such as EMI induced by cellular phones) to sensitive internal electronic circuits. The EMI filter design described herein effectively de-couples and shields such signals over a broad frequency range before they can enter into the titanium can and disrupt normal pacemaker or ICD functions.