Potential interference issues between FCC part 15 compliant UHF ISM emitters and equipment passing standard immunity testing requirements

The potential for electromagnetic (EM) interference between multi-channel, FCC Part 15 UHF (902-928 MHz) ISM (Industiral, Scientific, and Medical) [1] emitters and devices that have passed immunity requirements under international standards [2] is examined. At close ranges, the fields from a Part 15.247 compliant emitter may exceed minimum standard immunity testing levels. This does not imply interference will occur, only that the device may not be qualified to operate in the EM environment near the emitter. Some recent studies have shown minimal interference between Section 15.247 equipment and commercial devices [3, 4]. Other studies have indicated that (EU) UHF interference potential can exist [5, 6]. The range at which Part 15 devices may pose a risk to electronic devices compliant with standard immunity regulations is estimated and compared to these studies. Because Radio Frequency Identification (RFID), especially passive UHF RFID, emitters may be deployed in numerous locations and in close proximity to many devices, it has been the focus of many of the studies of interference potential. RFID emitters may be one of the largest populations of the Part 15 devices, but the EMI potential of general Section 15.247 emitters is addressed.