Sources of radiofrequency interference for medical devices in the non clinical environment

Radiofrequency (RF) sources in the non clinical environment can expose medical devices to field strengths that exceed several volts per meter Electric (E) field strengths were measured at typical usage sites for home or ambulatory medical devices. Isotropic, broadband E field probes and calibrated antennas with spectrum analyzers were used. Three distinct categories of RF source/exposure situations were identified: “Distant Transmitters” includes high power radio and television broadcast transmitters. These can produce field strengths that are greater than 3 V/m at distances greater than 500 meters from the broadcast antenna. “Local Transmitters” such as 25-100 watt transceivers in emergency vehicles can produce exposure field strengths of more than 3 V/m up to 10 meters from their antenna. “User Handheld Transceivers” such as handheld cellular phones and security guard transceivers radiate 0.6 to 7 watts and produce field strengths that can exceed 3 V/m at distances of over 3 meters. These field strengths all equal the minimum 3 V/m immunity level specified in the prevailing IEC-601-1-2 international medical device electromagnetic compatibility standard