Methodologies for reduction of noise interference in wireless charging implantable cardiac sensor

Abstract

With the commercialization of implantable medical devices (IMDs), wireless charging system has also been introduced into IMDs. It can solve the problem of the battery discharge so it can give convenience to the patients by eliminating the requirement of the battery replacement surgery. However, magnetic field is generated by the wireless charging system, causing magnetic interference to the IMDs. Especially, measured by the implantable cardiac sensor among IMDs to detect abnormal heartbeat, electrocardiography (ECG) is vulnerable to external interference. Therefore, it is important to solve magnetic interference for implantable cardiac sensor applied with the wireless charging system.This paper proposes methodologies for reduction of noise interference at ECG in wireless charging implantable cardiac sensor. The first methodology is to design the pattern of the trace between sensing electrodes using the principle of canceling the magnetic field. And the second methodology is to physically block the magnetic field with shielding material such as aluminum and magnetic sheet. In the proposed methodologies, the shielding effectiveness against interference was verified through simulation and experiment. In addition, the proposed methodologies were compared for the shielding effectiveness and, pros and cons of applying to wireless charging IMDs.