Design and Performance Evaluation of a Compact Implantable Antenna for Biomedical Applications

This work presents an implantable antenna for biomedical applications, which resonates at the ISM (industrial, scientific, and medical) band of 2.4–2.48 GHz when placed beneath the skin, precisely within the fat tissue among the three layers (skin, fat, and muscle) of the human-tissue phantom. The antenna is designed on a FR-4
$(\ {{\varepsilon }_{\bm{r}}} = {\mathrm{ }}4.3{\mathrm{ }}and{\mathrm{ }}tan\delta = 0.025)$
substrate of 0.36 mm thickness. The design is based on a defected ground structure (DGS) and a shorting pin between patch and ground, both of which helps to reduce the antenna size by lengthening its electrical path. Furthermore, the antenna is encapsulated with biocompatible silicon
$(\ {{\varepsilon }_r} = 11.9{\mathrm{ }}and{\mathrm{ }}\sigma = 0.00025{\mathrm{ }}S/m)$
superstrates of 0.5 mm thickness. The proposed antenna is very compact in dimension
$( {8\ \times \ 6\ \times \ 1.36} )$
mm³, while provides high bandwidth and gain of 10.57% and -20.10 dBi, respectively. The antenna is simulated using CST to investigate its performance. At the center frequency of 2.46 GHz, input impedance of the antenna is found to be (
$50.09\ + \ 1.17)\ \Omega$
, which assists a good impedance matching, resulting a VSWR of 1.02. Finally, the link margin is calculated to establish far-field communication, which shows that the antenna supports a high data rate of 1 Mbps up to a distance of about 9 m for SAR limited power.