title: A biosignal instrumentation system using capacitive coupling for power and signal isolation.
abstract: Requirements for patient safety and a high interference rejection ratio in medical equipment create a demand for effective isolation devices. A system scale approach that uses capacitive coupling for power and signal isolation is presented. In addition, we describe the development of an instrumentation system prototype that applies microwaves for power exchange and bidirectional data transfer across the isolation barrier. The system consists of an isolated transducer unit, a central unit, and a single coaxial cable between the units. The isolation capacitance is as low as 1.6 pF, inclusive of the digital data transfer and power exchange up to 600 mW of isolated direct current (dc) power. The system is suitable for line-powered biopotential measurements and it is shown that reducing the isolation capacitance from 180 to 1.6 pF improves the power line rejection by 30 dB in a typical electrocardiogram (ECG) measurement setup.
authors.affiliation: Applied Electronics Laboratory, Department of Electrical and Communications Engineering, Helsinki University of Technology, P.O. Box 3000, Otakaari 5 A, 02015 Espoo, FI-02015 TKK, Finland. kari.piipponen@tkk.fi
authors.forename: Kari Väinö Tapio
authors.initials: KV
authors.lastname: Piipponen
authors.forename: Raimo
authors.initials: R
authors.lastname: Sepponen
authors.forename: Pekka
authors.initials: P
authors.lastname: Eskelinen
mesh_terms: D000669:Amplifiers, Electronic; D016477:Artifacts; D017076:Computer-Aided Design; D025802:Electric Capacitance; D004560:Electricity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety / Q000295:instrumentation* / Q000379:methods