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

Abstract

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 S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> (>-25 dB) at 402 MHz, and gain stability of 0.35~0.5 GHz. Furthermore, the measured S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> 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.