Near-Field Wireless Power Transfer to Deep-Tissue Implants for Biomedical Applications

Wireless power transfer (WPT) plays critical roles in powering deep-tissue implants, which also contributes to several emerging advances for biomedical engineering. To enable a high-power density region in implants, this article presents a method, termed the self-phasing technology, to focus electromagnetic fields from various paths at a deep-tissue spot. By performing the phase-conjugated operation on the incident signal and then retransfer back to the source, coherent RF power can be achieved without learning the precise or even dynamic locations of sources and concerning inhomogeneous medium perturbations. An external slot antenna array placed above skin surface 4 mm is considered as a transmitter and an implanted rectenna consisting of a magnetic resonant coil and an RF-to-dc rectifier circuit is treated as a receiver. The conversion efficiency of the rectifier circuit is optimized within the received power range and the measured efficiency of 50% can be achieved at 0 dBm. To visualize the transceiver effects of the integrated system under safety thresholds, a light-emitting diode (LED) is soldered at the terminal of the rectenna and measurements show that smooth drive can be achieved. Certain brightness of LED can demonstrate that the self-phasing technology can support WPT for biomedical applications.