Circularly Polarized Implantable Antenna With Improved Impedance Matching

This letter proposes a circularly polarized patch antenna with a compact volume of 91.9 mm(3) for implantable applications. Foremost, the input impedance of patch antenna with reduced ground inside lossy muscle tissue is analyzed. Then following the traditional way of realizing circular polarization (CP) performance, crossed slots are introduced into the patch center. However, as the working environment is lossy tissue rather than traditional air, additional LC elements are needed to meet the impedance matching of 50 omega. Thus, besides crossed slots in the center, arc-shaped slots and shorting pins are loaded on the antenna edge. Simulated results show that a CP bandwidth of 18.3% is obtained, proving the antenna is suitable for biomedical devices.