A Biosignal Instrumentation System Using Capacitive Coupling for Power and Signal Isolation

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.

[1]  François Krummenacher,et al.  A model for /spl mu/-power rectifier analysis and design , 2005, IEEE Transactions on Circuits and Systems I: Regular Papers.

[2]  C. A. Grimbergen,et al.  HIGH QUALITY RECORDING OF BIOELECTRIC EVENTS . I : INTERFERENCE REDUCTION , THEORY AND PRACTICE , 2009 .

[3]  E.M. Spinelli,et al.  A transconductance driven-right-leg circuit , 1999, IEEE Transactions on Biomedical Engineering.

[4]  Ramon Pallàs-Areny,et al.  A comprehensive model for power line interference in biopotential measurements , 2000, IEEE Trans. Instrum. Meas..

[5]  J G Webster,et al.  60-HZ interference in electrocardiography. , 1973, IEEE transactions on bio-medical engineering.

[6]  John G. Webster,et al.  Driven-right-leg circuit design , 1983, IEEE Transactions on Biomedical Engineering.

[7]  M.F. Hajer,et al.  Design of an optical power supply for biopotential measurement systems , 1999, Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. N.

[8]  Eugenio Culurciello,et al.  Capacitive coupling of data and power for 3D silicon-on-insulator VLSI , 2005, 2005 IEEE International Symposium on Circuits and Systems.

[9]  C A Grimbergen,et al.  High-quality recording of bioelectric events , 1990, Medical and Biological Engineering and Computing.

[10]  John G. Webster,et al.  Reductionl of Interference Due to Common Mode Voltage in Biopotential Amplifiers , 1983, IEEE Transactions on Biomedical Engineering.