Miniaturized Wireless Power Transfer System With a Dual-Band Implantable Antenna for Multifunctional Biomedical Devices

In this article, we present the development of a miniaturized wireless power transfer (WPT) for spinal cord (SC). The system comprises a dual-band implantable antenna, a wearable slotted patch antenna, and a half-wave rectifier. It introduces a miniaturized dual-band implantable antenna, combining meandered line and spiral techniques to achieve wide impedance bandwidths. The transmitter antenna demonstrates an impedance bandwidth below -10 dB, spanning a fractional impedance bandwidth of approximately 5.5% from 1.42 to 1.5 GHz. On the other hand, the dual-band implantable antenna receiver and the rectifier were designed on a two-layer printed circuit board (PCB), and the compactness of the system is improved by integrating the rectifier circuitry directly onto the bottom of the implanted antenna, streamlining the overall design. Its dimensions are 7 × 7× 0.5 mm3, achieving impedance bandwidths of 20.5% and around 17% at the industrial, scientific, and medical (ISM) frequency of 915 and 1470 MHz, respectively. Furthermore, the proposed WPT system achieves a power transfer efficiency (PTE) of 1.15% by improving the coupling between receiving (Rx) and transmitting (Tx) antennas using magnetic-based designs, thereby reducing human tissue losses. Finally, the measured results obtained inside minced pork show a high degree of agreement with the expected performance, validating the system's performance in realistic biological environments.