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A Low-Frequency 3-Coil Inductive System for Wirelessly Powering Leadless Pacemakers

The purpose of this study is to investigate the outcome of a small-sized implant at low frequency for powering the pacemakers. To do so, a 3-coil inductive wireless power transfer system having a solenoid implantable coil is designed at low-frequency in the air and tissue mediums and the performance is evaluated on the basis of power transfer efficiency (PTE). The PTE of the designed system is analyzed at perfect alignment, lateral and/or angular misalignments with respect to varying distances between the coils and input powers. The simulations are carried out by a magnetic field simulator at 13.56 MHz for input powers of 1 W and 500 mW. The maximum lateral and angular misalignments considered are 20 mm and 60° respectively. When the distance between the external and implantable coils in air is 40 mm, a maximum PTE of 0.24% is achieved at perfect alignment and conversely, a minimum PTE of 0.11% is obtained at 60° of angular misalignment. The efficiency drops by 0.10% at perfect alignment with tissue in between the coils. Based on the simulated results it is observed that, a minimum of 600 mW input power is required for powering the pacemaker at 13.56 MHz in tissue medium even under severe misalignment of coils.