Development of Nonsuperstrate Implantable Low-Profile CPW-Fed Ceramic Antennas

A broadband nonsuperstrate implantable CPW-fed monopole antenna operating at the Medical Implant Communication Service (MICS) frequency band (402~405 MHz) is developed on a microwave dielectric ceramic substrate with high dielectric constant and high quality factor. Compared to other similar implantable antennas covered with superstrates, the advantages of the proposed nonsuperstrate antenna are: miniaturization and low profile (≈1 mm), wide measured bandwidth (>130 MHz/33.5%), deep measured S₁₁ (>-25 dB) at 402 MHz, and gain stability of 0.35~0.5 GHz. Furthermore, the measured S₁₁ is stable enough even for a period of 60 days. Therefore, the proposed antenna demonstrates the stable characteristics of direct contact tissue loading on a high-dielectric-constant ceramic substrate and is suitable for implanted biotelemetry applications.