Effectiveness evaluation of shielding material for reducing electromagnetic interference of cardiac pacemaker by portable information terminals

A shielding technique is an effective means to protect implanted cardiac pacemaker users from portable information terminals, whereas no evaluation methods for this aim have been established. In this paper, an FDTD model for predicting EMI levels in the pacemakers was introduced for numerical shielding effectiveness evaluation. In the model the pacemaker acted as a receiving antenna, which resulted in that the open-voltage at the pacemaker connector can be used as an appropriate index for EMI prediction. With this model the effectiveness of a magnetic rubber sheet and a resistive film was evaluated for reducing the EMI level in the pacemaker by portable information terminals. The results have shown that the resistive film has an excellent shielding effect so that even if the distance between the antenna and the human body is as close as 1.5 cm, the resistive film enables one to secure an effective distance longer than 22 cm being specified in the guideline of the Pacemaker Committee of Japan.