A design approach for reducing EMI problems with electronic medical equipment

摘要

High-tech medical equipment creates high levels of electrical energy. The use of electricity in medical equipment dates back to 1745 when Leyden, who invented the Leyden jar capacitor, designed an electrostatic machine to charge the capacitor, which was then discharged into the body ostensibly to cure some types of paralysis, diseases of the internal organs, impotence, infertility, psychoses, and a variety of other ailments. Even early medical devices, which were very simple, generated some form of electromagnetic emissions (radiated and conducted), but the emissions were low in magnitude and occupied a short frequency band. Moreover, there were few, if any, medical equipment or systems that might be compromised by such emissions. Today, the case is much more problematic. High-tech medical equipment creates high levels of electrical energy, measures picovolt to millivolt signals from the human body, treats diseases and illnesses with fewer invasive procedures, and probes the micro-cellular structures of vital organs. The demand for microprocessor-controlled medical equipment that can operate in known and complex electrical and electromagnetic environments that are forever changing has never been greater, and the concerns over creating an EMI problem continue.