携帯電話で埋込み型心臓ペースメーカーに生ずる電磁干渉電圧のFDTD計算

日本ペースメーカー協議会は,数百種類にのぼるペースメーカーの携帯電話に対するイミュニティ試験を実施し,アンテナがペースメーカー本体と電極リード線とのコネクタ部近辺にある場合には電磁干渉(EMI)が最も生じやすいことを示唆している.この知見に基き,ペースメーカーにおける携帯電話で生ずるEMIレベルの予測を試みた.すなわち,ペースメーカーを受信アンテナとみなし,コネクタからみたペースメーカー内部のインピーダンスを受信アンテナの負荷,本体及び電極リード線を受信アンテナの両エレメントとして,携帯電話による負荷上に誘起される電圧をEMI電圧としてFDTD(Finite-Difference Time-Domain)法で計算した.さらに,このように予測したEMIレベルを,ペースメーカー協議会の実測結果と比較し,その妥当性を検証した.
A prediction of the electromagnetic interference (EMI) of pacemakers due to portable telephones is significant in improving the immunity of pacemakers. The Pacemaker Committee of Japan recently conducted immunity tests of pacemakers for portable telephones, and consequently concluded that the connector between the pacemaker housing and the lead wire of electrode plays a major role for the EMI due to portable telephones. Based on this finding, a computer model for predicting the EMI level has been presented, in which the internal impedance looked from the connector and the metal portion consisting of the pacemaker housing and the lead wire of electrode were considered as a load and two halves of a receiving antenna, respectively. Interference voltages induced through the connector were analyzed by using the finite-difference time-domain (FDTD) method in conjunction with a torso and portable telephone model. The modeling was validated by comparison with the previously reported experimental results.