Evaluation of Electromagnetic Interference with Wireless Medical Telemeter by Radiation Noise from LED Lamps.

Abstract

Switched mode power supplies built in LED lamp radiate electromagnetic noise (LED noise) and may interfere with wireless medical telemeters (WMTs). We conducted research on statistical characteristics of LED noise and its effect on the receiver sensitivity of the WMT. We measured timedomain waveform of LED noise. At the wideband reception, LED noise has impulsive characteristics due to high-speed switching, but this impulsive nature is difficult to identify when the narrow bandwidth. Additionally, this noise is to be approximated as Gaussian noise, because the WMTs use a narrow reception bandwidth of 8.5 kHz and LED noise was limited to this bandwidth. We investigated the required signal power of the WMTs for critical reception under interference by LED noise and for comparison with Gaussian noise. The LED noise and Gaussian noise induce similar degradation in the WMT, confirming that the Gaussian approximation is promising for the evaluation of interference in the WMT caused by LED lamps. Moreover, we showed an experimentally investigation of spatial distribution of LED noise around an LED lamp and its power line under the basic configuration. The spatial variation caused by a standing wave of the disturbance current was observed in the parallel direction to the power line, and the noise amplitude was decreased away from the power line in the perpendicular direction.