Implantable Wideband Low-Specific-Absorption-Rate Antenna on a Thin Flexible Substrate

This letter proposes an implantable wideband low-specific-absorption-rate (SAR) antenna on a flexible substrate. The proposed antenna structure was printed on a thin flexible substrate, which is suitable for implantable human body applications. A sigma-shaped monopole radiator and the C-shaped design excited fundamental and coupled modes that dominated the near E-field distribution evenly to achieve a low SAR. The proposed antenna was fabricated and measured on a flexible substrate. The smallest size (80 mm³) was achieved with low-profile flexible substrate compared to a state-of-the-art implantable antenna over 400 MHz, and 68% fractional bandwidth was achieved. The maximum peak value of the average SAR was approximately 230 W/kg when the input power was 1 W. The maximum input power of the proposed antenna was approximately 10 mW.