A Miniature-Implantable Antenna for MedRadio-Band Biomedical Telemetry

Abstract

This letter presents a compact implantable antenna for biotelemetry in the Medical Device Radiocommunications Service (MedRadio) band (401-406 MHz). By employing meandering and shorting strategy, the whole dimension (including the superstrate) of the proposed antenna can be significantly reduced to ${\hbox {12.5}} \times {\hbox {12.5}} \times {\hbox {1.27}}~\hbox{mm}^3$ , equivalent to ${\hbox {0.0168}}{\lambda _0} \times {\hbox {0.0168}}{\lambda _0} \times {\hbox {0.0017}}{\lambda _0}$ ( ${\lambda _0}$ is the free-space wavelength at 403 MHz). Instead of common miniaturization methods used for implantable antennas, such as stacking multilayers and embedding slots on the ground plane, the proposed antenna is fabricated on the single-layer substrate with a full ground plane. Therefore, the proposed antenna is characterized by the advantages of easy manufacture, low cost, light mass and less sensitivity to package environment. The simulated and measured bandwidths are 6.15% and 7.26%, respectively. The peak realized gain is $-{\hbox {32.49}}~\hbox{dBi}$ at 403 MHz. The maximum specific absorption rate (SAR) value satisfies the IEEE standard safety guidelines. A prototype is fabricated and measured in vitro to verify the validity of the presented design.