Electric Field and Transmitting Power Analysis of Segmented and Unsegmented Loop Antennas for Transcutaneous Power Transfer

This article investigates the peak electric field intensities (PEFIs) and maximum excitation voltage allowed (MEVA) of inductive link wireless power transfer (WPT) to medical implants embedded in the human head. Segmented and unsegmented antennas in the geometry of toroidal, hexagonal, and circular are included, with the widths of 2, 1, and 0.2 mm. Extensive simulations show that, compared with unsegmented antennas, the segmented ones can significantly reduce the PEFI and increase the MEVA within specific absorption rate (SAR) constraints. By segmentation, the reduction of PEFI is more effective at a higher operating frequency. The antenna with a smaller width will radiate a smaller PEFI. With the same antenna width, the hexagonal antenna radiates the largest PEFI, which is followed by its circular and toroidal counterparts. Of all the antennas under research, the unsegmented hexagonal antenna with a width of 2 mm radiates the largest PEFI, and the segmented toroidal antenna with a width of 0.2 mm radiates the smallest PEFI. Considering PEFI and MEVA, the antenna in a toroidal geometry is preferred, and the segmentation should be applied to a hexagonal antenna. When an antenna width is larger than 1 mm, the segmentation of the antenna is suggested.