Design of a Compact 868 MHz On-Body Matched Antenna for Relaying Biomedical Implants

A compact <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(40\times 40\times 0.8$</tex> mm ) 868 MHz Long Range (LoRa, 863–870 MHz) band repeater antenna is proposed for on-body relaying of biomedical implants. The antenna is designed in close proximity to a canonical three-layer tissue model and validated with simulations using three realistic human models. The antenna achieves a 12.3 % fractional bandwidth and maintains robust performance across different models with a maximum on-body gain of -8.1 dBi. Specific Absorption Rate (SAR) analysis confirms compliance with International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines, making it suitable for on-body biomedical applications.