A Compact Tissue-Insensitive Ultra-Wideband Implantable Antenna for Wireless Power Transfer in Implantable Medical Devices

This work presents the development of a new, compact, two-port ultra-wideband implantable antenna with low sensitivity to implanting tissue and depth for energy harvesting applications in implantable medical devices (IMD). The proposed antenna features two compact radiating elements, operating at a center frequency of 2.45 GHz and occupying a very compact volume of 22.1 mm3 (<inline-formula> <tex-math notation="LaTeX">$7.25\times 6\times 0$ </tex-math></inline-formula>.508 mm3). Miniaturization techniques such as meandered line slots, Defected Ground Structure (DGS), and shorting via were utilized to achieve this compactness. The stable performance of the antenna versus the implantation depth is established numerically and experimentally by considering both shallow and deep implantation depths. The antenna was implanted in a meat phantom and the results revealed wideband performance with measured bandwidths of 80.5% (<inline-formula> <tex-math notation="LaTeX">$1.38~\sim ~3$ </tex-math></inline-formula>.24 GHz) and 32.6% (<inline-formula> <tex-math notation="LaTeX">$2.08~\sim ~2$ </tex-math></inline-formula>.89 GHz) for Port-1 and Port-2, respectively. This ultra-wideband performance is shown to be effective in reducing the antenna&#x2019;s sensitivity to the different types and depths of human biological tissues. Finally, the performance of the proposed implantable antenna has been successfully examined as part of a complete Wireless Power Transfer (WPT) system developed to improve Power Transfer Efficiency (PTE). The results show the superiority of the proposed two-port implantable antenna in improving PTE compared to the typical single-port implantable antennas.