Impact of LED lamp noise on receiver sensitivity of wireless medical telemetry system

To evaluate the electromagnetic interference (EMI) in a wireless medical telemetry system (WMTS) caused by LED lamp emission, the statistical characteristics of noise and its impact on the receiver sensitivity of the WMTS were investigated. Noise from LED lamp is generally wide-band owing to high-speed switching, but the WMTS employs narrow-band reception of 8.5 kHz. The amplitude probability distribution of band-limited noise from LED lamp agrees well with that of Gaussian noise with average power equal to that of band-limited LED noise. The increase in the required signal power of the WMTS for critical reception, caused by LED noise, was almost the same as that in the case of purely Gaussian noise with equal power. The above results indicate that LED noise interfering with a WMTS channel can be well modeled by Gaussian noise, and that the interference effect can be simply represented by the reduction in the receiving carrier-to-noise ratio (CNR), enabling easier evaluation of the impact of interference in the WMTS by using the CNR.