Metamaterial-Loaded Compact High-Gain Dual-Band Circularly Polarized Implantable Antenna System for Multiple Biomedical Applications

This communication presents a metamaterial (MTM)-loaded compact dual-band circularly polarized antenna system suitable for multiple bio-telemetric applications. The proposed antenna system operates in the industrial, scientific, and medical (ISM) bands with center frequencies: 915 MHz (902-928 MHz) and 2450 MHz (2400-2480 MHz). The integration of an MTM structure with epsilon-very-large property on the superstrate layer of the antenna produces significant gain enhancement and strong circular polarization (CP) behavior at both the operating frequencies. The key features of the proposed antenna system are its compact size (7 mm × 6 × 0.254 mm), dual-band CP characteristics, significantly high gain values (-17.1 and -9.81 dBi in the lower and upper bands, respectively), and slot-less ground plane that reduces the complexity and backscatter radiation. The performance of the MTM-loaded antenna system is validated experimentally. The antenna is fabricated and integrated with dummy electronics and batteries and is enclosed in a 3-D printed device. The hermetically sealed device is tested in minced pork muscle to validate the simulation results. The measured impedance bandwidths of 35.8% and 17.8% are obtained in the lower and upper ISM bands, respectively. The specific absorption rate of the antenna system is evaluated at both frequencies in different tissues. Additionally, to determine the wireless communication range, the link margin is estimated at data rates of 100 kbps and 1 Mbps.