Realization of Circular Polarization and Gain Enhancement for Implantable Antenna

Abstract

This paper proposes and investigates an implantable circularly polarized (CP) antenna with an enhanced gain. The proposed antenna consists of a pin-loaded patch and via walls around the patch. The pin-loaded patch has a pair of orthogonal normal modes instead of degenerated modes, and two open-ended slots etched on the patch make resonant frequencies of the two modes close and introduce a 90-deg phase difference. The via walls protect the antenna against a gain loss due to lossy tissues. Simulation results show that the proposed antenna has impedance and CP bandwidths of 23.1% and 12.8%, and a gain improvement of 1.5 dBi due to the via walls. Finally, the proposed antenna is fabricated and measured, and measured results agree well with simulated one.