Wireless medical telemetry systems (WMTSs) are typical radio communication–based medical devices that monitor various biological parameters, such as electrocardiograms and respiration rates. In Japan, the assigned frequency band for WMTSs is 400 MHz. However, the issues accounting for poor reception in WMTS constitute major concerns. In this study, we analyzed the effects of electromagnetic interferences (EMIs) caused by other radio communication systems, the intermodulation (IM) effect, and noises generated from electrical devices on WMTS and discussed their management. The 400-MHz frequency band is also shared by other radio communication systems. We showed the instantaneous and impulsive voltages generated from the location-detection system for wandering patients and their potential to exhibit EMI effects on WMTS. Further, we presented the IM effect significantly reduces reception in WMTS. Additionally, the electromagnetic noises generated from electrical devices, such as light-emitting diode lamps and security cameras, can exceed the 400 MHz frequency band as these devices employ the switched-mode power supply and/or central processing unit and radiate wideband emissions. Moreover, we proposed and evaluated simple and facile methods using a simplified spectrum analysis function installed in the WMTS receiver and software-defined radio for evaluating the electromagnetic environment.

无线医疗遥测系统 (WMTS) 是典型的基于无线电通信的医疗设备，可监测各种生物参数，例如心电图和呼吸频率。在日本，WMTS 的指定频段为 400 MHz。然而，导致 WMTS 接收效果不佳的问题构成了主要问题。在本研究中，我们分析了其他无线电通信系统引起的电磁干扰 (EMI)、互调 (IM) 效应以及电气设备产生的噪声对 WMTS 的影响，并讨论了它们的管理。 400 MHz 频段也由其他无线电通信系统共享。我们展示了游走患者位置检测系统产生的瞬时脉冲电压及其对 WMTS 表现出 EMI 影响的潜力。此外，我们还提出了 IM 效应显着降低了 WMTS 中​​的接收效果。此外，发光二极管灯和安全摄像头等电气设备产生的电磁噪声可能超过 400 MHz 频带，因为这些设备采用开关模式电源和/或中央处理单元并辐射宽带发射。此外，我们还提出并评估了简单易用的方法，使用安装在 WMTS 接收器和软件定义无线电中的简化频谱分析功能来评估电磁环境。