On-body passive patch antenna for enhanced wireless power transfer to an implantable antenna

This paper presents a novel configuration using an on-body passive patch antenna (PPA) to enhance far-field wireless power transfer (WPT) to an implantable antenna. The PPA consists of a radiating patch printed on a dielectric substrate and backed by a slotted metallic ground plane, mounted directly on the body. This configuration simultaneously reduces power reflections caused by the skin–air impedance mismatch and increases the concentration of electromagnetic field intensity in the target implant region. The combined effect results in a significant enhancement in power transfer efficiency (PTE). The proposed approach is validated through theoretical analysis, full-wave simulations, and experimental measurements. Compared with existing designs reported in the literature, the proposed on-body PPA configuration achieves significantly higher PTE while maintaining a low-profile, compact, and simple structure, and simultaneously increasing the return-loss (RL) bandwidth of the in-body antenna. The measured results show close agreement with simulations, and additional measurements using phantoms of different sizes further demonstrate the robustness of the proposed configuration. The measured enhancements in the transmission coefficient are 18.6 dB and 15.4 dB for the small and large phantoms, respectively, compared with 20.4 dB and 17.1 dB obtained from simulations. In addition, the semi-infinite phantom simulation predicts an enhancement of 18 dB. Finally, beyond WPT applications, the proposed configuration is theoretically shown to extend the transmission range of the in-body antenna for data telemetry from 2.5 m to 18.5 m for a 10 dB link margin. Alternatively, the additional link margin can be utilized to reduce the transmit power of the implantable device, thereby lowering power consumption and extending battery life.