Evaluation of Electromagnetic Noise Emitted from Light-Emitting Diode (LED) Lamps and Compatibility with Wireless Medical Telemetry Service

Kai ISHIDA  Ifong WU  Kaoru GOTOH  Yasushi MATSUMOTO  

Publication
IEICE TRANSACTIONS on Communications   Vol.E103-B   No.6   pp.637-644
Publication Date: 2020/06/01
Publicized: 2019/12/04
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2019HMP0003
Type of Manuscript: Special Section PAPER (Special Section on Information and Communication Technology for IoT/CPS in Medicine and Healthcare)
Category: 
Keyword: 
wireless medical telemetry service,  switching regulator,  LED lamp,  electromagnetic compatibility,  receiver sensitivity,  

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Summary: 
Wireless medical telemetry service (WMTS) is an important wireless communication system in healthcare facilities. Recently, the potential for electromagnetic interference by noise emitted by switching regulators installed in light-emitting diode (LED) lamps has been a serious problem. In this study, we evaluated the characteristics of the electromagnetic noise emitted from LED lamps and its effect on WMTS. Switching regulators generally emit wide band impulsive noise whose bandwidth reaches 400MHz in some instances owing to the switching operation, but this impulsive nature is difficult to identify in the reception of WMTS because the bandwidth of WMTS is much narrower than that of electromagnetic noise. Gaussian approximation (GA) can be adopted for band-limited electromagnetic noise whose characteristics have no repetitive variation. On the other hand, GA with the impulsive correction factor (ICF) can be adopted for band-limited electromagnetic noise that has repetitive variation. We investigate the minimum receiver sensitivity of WMTS for it to be affected by electromagnetic noise emitted from LED lamps. The required carrier-to-noise power ratio (CNR) of Gaussian noise and electromagnetic noise for which GA can be adopted was approximately 15dB, but the electromagnetic noise for which GA with the ICF can be adopted was 3 to 4dB worse. Moreover, the spatial distribution of electromagnetic noise surrounding an LED lamp installation was measured. Finally, we roughly estimated the offset distance between the receiving antenna of WMTS and LED lamps when a WMTS signal of a certain level was added in a clinical setting using our experimental result for the required CNR.