EMI evaluation based on electromagnetic and circuit analysis for human body communication systems

In this paper, we employed a two-step approach to evaluate the electromagnetic interference (EMI) voltage at cardiac pacemaker from human body communication (HBC) signals. In the first step, we calculated the input voltage of the analogue sensing circuit of pacemaker using an electromagnetic field analysis tool by considering the pacemaker as a receiving antenna. In the second step, we evaluated the output voltage of the sensing circuit via a circuit simulation approach. The results have shown that a part of HBC signals passes through the low-pass filter of the sensing circuit as interference. Moreover, a DC offset component of the operational amplifier (opamp) in the sensing circuit is further added to the high-frequency interference voltages so that the sensing threshold of malfunction is easier to be exceeded. As a result, it is found that there may be a margin at least 25 dB for malfunction of pacemaker under a typical 1-V HBC transmit voltage and the representative sensing circuit configuration.