Analysis and optimization of six types of two-coil inductive for the human implantable wireless electrocardiogram sensor

Abstract

Atrial fibrillation (AFib or AF) is the leading cause of heart arrhythmia in the U.S and it causes damage to the heart tissue. It can be detected using an electrocardiogram (ECG or EKG). However, there are some limitations to using ECG sensors such as external electrodes, fault electrical signals, short time monitoring of patients, and failure to detect the abnormal heart rhythm. In addition, some patients with symptoms which are present for a limited time and then stop, need to be continuously monitored. A human implantable electrocardiogram sensor is a key instrument to monitor, diagnose, and detect the heart problem such as AFib, heart attack, and coronary artery diseases. In this paper, a 2-coil inductive wireless power transfer (WPT) system, having three different shapes including circular, elliptical, and square coils, is designed, and optimized at a resonant frequency of 13.56 MHz to overcome low power transfer efficiency (PTE). Six different combinations of coils are proposed to induce WPT. The transmitter and receiver coils are in alignment together and their PTE are compared. At close distance between aligned coils, the maximum PTE is 56.2 % for square-square coil at the resonant frequency of 13.56 MHz. The distance and frequency parameters are used to optimize the square-square coil with maximum PTE. The optimization results showed that the PTE of the square-square coil is maximum at 0 mm distance between coils. The optimized coil with maximum PTE was utilized in the implantable ECG sensor and the electrical signals were successfully recorded.