Signal transmission analysis in implantable human body communication for abdominal medical devices

Implantable medical devices, such as neurostimulators, need to be wirelessly controlled from outside the body. Many of these devices use high-frequency signals in the 400 MHz, 900 MHz, and 2.45 GHz bands to communicate with external devices. However, high-frequency bands can suffer from signal attenuation in biological tissues and from electromagnetic interference with surrounding devices. In contrast, human body communication (HBC) uses relatively low frequencies in the 3–30 MHz band, which can alleviate signal attenuation and prevent emissions outside the body during communication. In this study, we investigated the use of HBC for implantable medical devices in the abdomen using electromagnetic field simulations. The results showed that the transmission between the transmitter inside the body and the receiver outside the body was adequate for stable communication. However, when the receiver was detached from the skin surface, the transmission characteristics rapidly decreased. Moreover, when the receiver and skin were separated by 1 mm, the transmission degraded by 34 dB, indicating that electromagnetic interference between the implanted transmitter and surrounding devices (including other medical devices) is rare. Finally, we evaluated the proposed system from the perspective of medical electromagnetic compatibility and human safety. The simulation results demonstrated that the radiated emissions and human exposure of the HBC system meet international standards.