A biosignal instrumentation system using capacitive coupling for power and signal isolation

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Medical Device Technology

Background:

• Medical equipment requires high patient safety and interference rejection.
• Effective isolation devices are crucial for demanding medical applications.
• Existing isolation methods may have limitations in power transfer and signal integrity.

Purpose of the Study:

• To present a system-scale approach for power and signal isolation using capacitive coupling.
• To develop an instrumentation system prototype utilizing microwaves for power and data transfer across an isolation barrier.
• To demonstrate the effectiveness of reduced isolation capacitance for improved performance in biopotential measurements.

Main Methods:

• Developed a system using capacitive coupling for power and signal isolation.
• Engineered a prototype employing microwaves for power exchange and bidirectional data transfer.
• Integrated an isolated transducer unit, a central unit, and a coaxial cable.
• Achieved isolation capacitance as low as 1.6 pF for power (up to 600 mW dc) and data transfer.

Main Results:

• The developed system enables power and signal isolation with minimal capacitance (1.6 pF).
• Achieved efficient power exchange (up to 600 mW dc) and bidirectional data transfer.
• Demonstrated suitability for line-powered biopotential measurements.
• Reduced isolation capacitance from 180 pF to 1.6 pF improved power line rejection by 30 dB in ECG measurements.

Conclusions:

• The presented capacitive coupling system effectively addresses the need for high isolation in medical equipment.
• The microwave-based prototype offers a robust solution for power and data transfer across isolation barriers.
• Significantly lower isolation capacitance enhances performance, particularly in sensitive measurements like ECG, improving power line rejection.